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1
Keating, Sarah Margaret. "Modelling of evanescent field immunosensors." Thesis, University College London (University of London), 2004. http://discovery.ucl.ac.uk/1446866/.
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Several factors affect the viability of biosensor design. This thesis presents the development of a computer-based model that will enable the sources and effects of noise and variations in concentrations within an evanescent field immunosensor to be analysed. The model was developed as a series of modules, each representing one aspect of the sensor, which when linked provide a simulation of the whole sensor. A complete solution of the complex biochemical reactions involved in the immunoassay module was achieved using a Markov chain approach. More traditional methods of solving sets of equations, such as optimisation, genetic algorithms and simulated annealing, all failed to produce satisfactory results. Two alternative assays, a sandwich and a competitive assay, are presented. The light module details the modelling of the coupling into a planar monomode waveguide and calculation of fluorescence excited by the resulting evanescent field using standard electromagnetic formulae. However, both beam divergence and scattering from the immobilised antibody layer were incorporated into the model. Two alternative coupling techniques were modelled, prism coupling and coupling through a "resonant mirror" multilayer. The detection system modelled the amplification of the fluorescence by a photomultiplier tube. The resulting model represents the most rigorous modelling undertaken in this area and the potential applications and benefits of such a model were detailed. Analysis of noise within the sensor allowed the impact of variation in the physical parameters defining the sensor to be determined and compared. The model was used to compare different protocols and confirmed that the sandwich assay produced the more sensitive device. A study of the kinetic response of the assay determined that measurements could be performed at half the time taken to reach equilibrium without significant loss of sensitivity. An analysis of the effect of scattering at the waveguide surface showed this to be significant noise factor. An initial study of the impact of the humectant layer illustrated that this is an issue that merits further consideration.
2
Grossman, Michael. "Evanescent Field Absorption Sensing Using Sapphire Fibers." Scholar Commons, 2007. http://scholarcommons.usf.edu/etd/3814.
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This thesis explores the application of coiled sapphire multimode optical fibers for evanescent wave chemical sensing in both the visible spectrum and the near infrared. As has been suggested in the literature pertaining to silica fibers, bending converts low-order modes to high order ones, which leads to more evanescent absorption and thus a more sensitive chemical detector. By coiling the fiber many times, it was expected that even greater sensitivity would be attained.
Experiments were performed to investigate the sensor response to different solutions and to characterize this response. In the first of three experiments, the large absorption peak of water at 3μm was examined in order to compare the sensitivity of a straight fiber versus a coiled one. In the second experiment, the effect of increasing the number of coils was investigated, as was the response of the sensor to varying concentrations of water in heavy water. In the third experiment, methylene blue dye was used to investigate the extent of adsorption of dye molecules on the sapphire fiber and its persistence
3
Ismaeel, Rand. "Microfiber devices based on evanescent field coupling." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/384514/.
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Microfiber (MF) devices are increasingly becoming attractive building blocks for numerous applications. This is attributed to a combinations of enabling properties including large evanescent field, compactness, low insertion loss and, most importantly, their configurability. This thesis describes the evanescent field coupling in MF devices in different forms and applications, such as microresonators for sensing, modal couplers for mode conversion and nonlinear frequency conversion. Micro-resonators are devices based on evanescent field coupling between turns of adjacent segments of the MF. Light inside these devices is confined within the resonator structure and trapped inside its cavity. Light, therefore, follows a longer path before passing to the output and this is wavelength dependent. A new type of resonator was successfully designed and manufactured: the multiport MF coil resonator. This structure has excellent features such as high extinction ratio, multiple resonance peaks and high stability. Novel modal couplers were also analysed and fabricated with high conversion efficiencies, high modal purity and low insertion loss. Modal couplers were manufactured to convert the launched input LP01 mode, into any of the higher order modes supported by the fiber. High conversion efficiencies were demonstrated for the LP11,LP21 and the LP02 modes. A MF coupler was successfully used for the detection of DNA by exploiting hybridisation on the surface of the MF coupler. The large evanescent field of the MF allows to detect the refractive index change that occurs when DNA attaches to the surface. Detection limits in the range of 10⁻⁶ per Refractive Index Unit (RIU) and sensitivities as high as 200nm=RIU were obtained. Nonlinearities were investigated both in straight MF and MF resonators, with particular stress on the second and third harmonic generation. While the conversion effciency remained relatively low for straight MFs, by using a loop resonator, the circulation of pump power (at resonance) inside the loop allowed for a conversion efficiency enhancement of 7.7 dB for the Third harmonic generation (THG) and 7.6 dB for the Second Harmonic Generation(SHG). Knot resonators were also used and provided larger enhancement of 14.2 dB for the SHG signal.
4
Shah, Suhani Kiran. "Modeling scattered intensity from microspheres in evanescent field." Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2021.
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Delezoide, Camille. "Polymer microring resonators for optofluidic evanescent field sensors." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2012. http://tel.archives-ouvertes.fr/tel-00846193.
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Optofluidic evanescent field sensing, especially microresonator-based label-free biochemical sensing, is an emerging technology under intensive study. In this context, we demonstrate that polymeric microring resonators are excellent transducers. It is partly due to the simplicity and cost-efficiency of their fabrication and integration, and also to their robustness: a fast, repeatable and low-cost method was developed to fabricate devices with long lifetimes and state-of-the-art performances. A second advantage is the extreme sensitivity achievable to grafted molecules: a detectable signal was obtained with only a few hundreds of 5-TAMRA-cadaverine (5-TC) molecules, relatively small as compared to nucleic acids, antibodies and other biomolecules. The surface immobilization of 5-TC molecules was achieved after a simple and reproducible UV/ozone procedure for surface preparation. However, the qualities of polymer microring resonators only become apparent when coupled to high-precision instrumentation. In that respect, a measuring instrument was built to detect minute and real-time variations of the optical resonances, and thus in an optofluidic regime. The detection of absorption and desorption of 5-TC molecules on a surface functionalized with its antibody was achieved. However, truly specific responses of the instrument would only be achieved in a multiplexed configuration. Such configuration is achievable, but has yet to be developed. Meanwhile, the measuring instrument, as is, can be used for a wide variety of applications, from the measurement of dispersion coefficients to the study of local thermal effects.
6
MacKenzie, Harry Straghan. "Evanescent-field devices for non-linear optical applications." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358807.
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McNab, Sharee J. "Evanescent near-field optical lithography : overcoming the diffraction limit." Thesis, University of Canterbury. Electrical and Electronic Engineering, 2001. http://hdl.handle.net/10092/6655.
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Concepts of optical resolution limits have been transformed in the past two decades with the development of near-field optical microscopy. Resolutions of λ/40 have been demonstrated by taking advantage of additional information present the near field of an object. These resolutions are far higher than what diffraction-limited lens-based optical systems are capable of. Attempts have been made to replicate these resolutions for lithography using a scanning probe based optical equivalent, but these systems suffer from low throughput owing to their serial nature.
A desirable alternative would be replication of all the patterns within a field in a single flood exposure in a manner similar to how optical projection lithography replicates the field of a mask, but with the additional resolution available from working in the near field. This is the basis of evanescent near-field optical lithography, the subject of this thesis. Evanescent near-field optical lithography (ENFOL) brings traditional contact lithography into the near-near field using a combination of conformable masks and ultra-thin photoresists.
This thesis describes a study of ENFOL both experimentally and via electromagnetic simulations to evaluate what the resolution limit might be. The fabrication of membrane masks is described, a key component for the ENFOL exposure. The characteristics of an ENFOL exposure using broad-band light are investigated from exposures into thick resist. These exposures demonstrate the trend of decreasing depth of field as the period of grating structures is reduced.
ENFOL's requirement of a thin imaging photoresist for high resolution lithography complicates the pattern transfer step essential to translate the photoresist image into a useful material for devices. The development of an additive pattern transfer process is described, that utilises a trilayer resist scheme to enable lift-off metallisation. NiCr gratings with periods down to 270nm have been fabricated using this process subsequent to an ENFOL exposure. Wire-grid polarisers consisting of 270nm-period NiCr gratings on glass substrates have been fabricated and their polarisation properties measured at visible wavelengths.
Simulation results of exposures of sub-wavelength grating structures are presented that investigate the fundamental limit to resolution for contact lithography techniques such as ENFOL. A full-vector, rigorous electromagnetic simulation technique, the multiple multipole program is used to provide information about the near field of subwavelength gratings. The potential for λ/20 resolution is indicated; a tantalising prospect for optical lithography and well below the diffraction limit of conventional optical projection-based lithographies. Perhaps the most critical parameter for an evanescent exposure, the depth of field, was characterised and a linear relationship shown between the depth of field and grating period. The effect of parameters such as grating duty cycle, absorber material and thickness on the exposure are observed with the intention to optimise the experimental setup.
Interesting interference phenomena are observed in simulation results for exposures. where the effective exposure wavelength is equivalent to the grating period. In particular a period halving occurs in the transverse magnetic polarisation due to interference of the first diffracted orders. A novel interference technique - evanescent interference lithography is proposed that takes advantage of an enhanced period halving at an exposure wavelength corresponding to a grating resonance.
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Wong, Yuen Mei. "Optimising the plastic optical fibre evanescent field biofilm sensor." Thesis, Liverpool John Moores University, 2008. http://researchonline.ljmu.ac.uk/5906/.
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This thesis describes the development, characterisation and application of large diameter multimode plastic optical fibre (POF) sensors using evanescent field modulation. The exposed polymethylmethacrylate (PMMA) core of the POF fibre forms the sensor interface that detects refractive index changes of a measurand acting as the cladding. When a liquid measurand is used, the sensor can detect changes in refractive index, absorption and suspended particulates. It is this simple mechanism by which the evanescent field POF sensor operates. The evanescent field POF sensor has been characterised for refractive index of surrounding liquid from 1.33 to 1.49. The sensor demonstrated accuracy of ± 7x 10-3 refractive index units below 1.4 and ±2x 10-3 refractive index units above 1.4. Components have been selected and designed for this project to ruggedise the sensor, to make the sensor more self-contained and cheaper. The original design of the test conditions did not allow for optimum deployment of the sensor as it stripped out the very modes of light that were required for sensing purposes. The system was also operating under pressure, not reflecting the real conditions under which the sensor would be operating. The re-design of test conditions holds the sensor without straining the POF and operates under normal atmospheric pressure. The POF sensor was demonstrated reacting to a real measurand eg biofilm in which initial growth affects the optical properties at the core cladding interface by refractive index modulation. This sensor was capable of measuring biofouling and scaling at water interfaces. The sensor was trialled in a European Commission funded project (CLOOPT) to study biofouling and scaling in closed loop water systems such as heat exchangers in the cooling tower of an electric power plant, and as an interface sensor for water quality monitoring (AQUA-STEW) involving biofilm removal and surface cleansing with a new application for contact lens protein removal systems. Tapering multimode POF was a desirable goal as this increases the proportion of light coupled into the core available for sensing purposes, to achieve a more sensitive evanescent field POF sensor. Optically clear and consistent smooth tapering of ends and mid-lengths of POF fibre were achieved through chemical removal of material. The tapered POF sensor was characterised with a range of refractive indices, and it exhibited two distinct regions; the water/alcohol region below 1.4 refractive index units, and the oil region above 1.4 suggesting the sensor's use as an oil-in-water, or water-in-oil sensor. From 95% confidence limits, the accuracy of the POF was ±O.006 refractive index units (to 2 standard deviations) for fluids of refractive indices above 1.4. Tapered POF is sensitive to refractive index providing a cheap, easy to handle and rugged throwaway sensor for water and beverage process and quality monitoring.
9
Ayachitula, Rajani. "Atom Optics Using an Optical Waveguide-Based Evanescent Field." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276669685.
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Shan, Liye. "Stimulated Raman scattering in the evanescent field of nanofibers." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112421/document.
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Cette thèse porte sur les mélanges d’onde non linéaires qui peuvent avoir lieu dans le champ évanescent de nanofibres de silice. Nous nous sommes plus particulièrement intéressés à la diffusion Raman stimulée qui est obtenue par l’interaction du champ évanescent très intense et un liquide non linéaire dans lequel baigne la nanofibre. Afin de mettre en évidence la diffusion Raman stimulée« évanescente », nous avons développé un modèle de simulation non linéaire dont le but est de déterminer les caractéristiques des nanofibres à réaliser. Le gain Raman modal est calculé afin de trouver le rayon optimal des nanofibres pour chaque liquide ou mélange de liquides possible. En considérant la puissance critique et le seuil de dommage de nos nanofibres, nous avons déduit la longueur minimale d’interaction. Les conditions d’adiabacité des parties évasées menant à la nanofibre sont également discutées. Ces spécifications nous ont amenés à développer une plateforme de tirage de nanofibres spécifiquement dédiée à ces expériences de non-linéarités évanescentes. Cette palteforme nous permet de tirer des nanofibres de diamètre allant jusqu’à 200 nm sur des longueurs de 10 cm, avec plus de 90% de transmission. Avec ces nanofibres, nous avons mis en évidence le premier ordre Stokes de l’éthanol dans le champ évanescent d’une nanofibre, ainsi que les premier et second ordres Stokes du toluène. Ces premières expériences sont en très bon accord avec nos simulations et ouvrent la voie à de nombreuses expériences en optique non linéaireThe present PhD thesis explored nonlinear wave mixing with the strong evanescent field of nanofibers. The focus has been on the effect of stimulated Raman scattering which is activated by the interaction between such a strong evanescent field and the nonlinear liquid surrounding the nanofiber. In order to observe the stimulated Raman scattering, we investigated the nonlinear modeling to determine the needed characteristics of the nanofibers. The modal Raman gain was calculated to determine the optimal radius of nanofibers for each possible liquid. Considering the critical power and the damage threshold of our nanofibers, we found the minimum required interaction length. The condition of adiabacity of the tapers was also described. These specifications of nanofibers guide us towards the design of a proper pulling system. Several pulling systems and techniques are investigated for the fabrication of our specific nanofibers. We now are able to fabricate low loss uniform nanofibers of up to 10 cm long, a diameter down to 200 nm, with two identical low loss tapers by using our own designed translation stage pulling platform and implemented with the “variable heat brush” technique. With the achieved nanofibers, the Raman effect induced in the evanescent field was observed in both pure (ethanol) and binary mixture (toluene in ethanol) liquids. These first measurements are in good agreement with our simulation even without any fitting parameters in the modeling
11
Sefa-Ntiri, Baah. "Embedded metal mask evanescent near field optical lithography (EMM-ENFOL)." Thesis, University of Birmingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522037.
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Wright, Alan James. "Distortion in conformable masks for evanescent near field optical lithography." Thesis, University of Canterbury. Electrical and Computer Engineering, 2007. http://hdl.handle.net/10092/1161.
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In this thesis the in-plane pattern distortion resulting from the use of Evanescent Near Field Optical Lithography (ENFOL) masks was investigated. ENFOL is a high resolution low-cost technique of lithography that is able to pattern features beyond the diffraction limit of light. Due to its use of the evanescent near field, ENFOL requires the use of conformable masks for intimate contact. Such masks can stretch and skew as they come into contact with silicon substrates and therefore distort the high resolution features patterned on them. It was desired to measure this distortion to ascertain the patterning performance of ENFOL masks and possibly correct for any uniform distortion found. To this end a sophisticated measuring process was successfully demonstrated. This involved the use of a Raith 150 Electron Beam Lithography (EBL) system with precision laser interferometer stage and metrology software module for automated measurements. Custom software was written for the Raith to enable it to take additional measurements to compensate for electron beam drift. Processing algorithms were then employed to using the measurements to compensate for beam drift and correcting for shift and rotation systematic errors. The performance of the in-plane distortion measuring process was found to have a precision of 60nm. With the ability to measure distortion, ENFOL masks were used to pattern substrates and distortion was found to be large, on the order of 1µm. This is much larger than desired for sub 100nm patterning as is expected of ENFOL. The distortions were non-uniform patterns of localised displacements. This, the observation of Newton's rings beneath a test mask and the observation of a single particle distortion across measurements of the same mask across different loadings in the EBL pointed to particulate contamination causing the distortion. In order to prove beyond doubt that particulate contamination was the cause of the spurious distortions, mechanical modelling using the Finite Element Method (FEM) of analysis was employed. The results from this matched the distortions observed experimentally, particles 20-40µm modelling the observed distortion.
13
Janotta, Markus. "Chemical surface modifications for improved mid-infrared evanescent field sensing systems." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/30549.
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Wang, Xiaofeng [Verfasser]. "Towards on-chip miniaturized mid-infrared evanescent field sensors / Xiaofeng Wang." Ulm : Universität Ulm, 2020. http://d-nb.info/1212443608/34.
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Yang, Seung-Hune. "A STUDY ON HIGH NA AND EVANESCENT IMAGING WITH POLARIZED ILLUMINATION." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/195239.
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Simulation techniques are developed for high NA polarized microscopy with Babinet's principle, partial coherence and vector diffraction for non-periodic geometries. A mathematical model for the Babinet approach is developed and interpreted. Simulation results of the Babinet's principle approach are compared with those of Rigorous Coupled Wave Theory (RCWT) for periodic structures to investigate the accuracy of this approach and its limitations.A microscope system using a special solid immersion lens (SIL) is introduced to image Blu-Ray (BD) optical disc samples without removing the protective cover layer.Aberration caused by the cover layer is minimized with a truncated SIL. Sub-surface imaging simulation is achieved by RCWT, partial coherence, vector diffraction and Babinet's Principle. Simulated results are compared with experimental images and atomic force microscopy (AFM) measurement.A technique for obtaining native and induced using a significant amount of evanescent energy is described for a solid immersion lens (SIL) microscope.Characteristics of native and induced polarization images for different object structures and materials are studied in detail. Experiments are conducted with a NA = 1.48 at wavelength550nm microscope. Near-field images are simulated and analyzed with an RCWT approach. Contrast curve versus object spatial frequency calculations are compared with experimental measurements. Dependencies of contrast versus source polarization angles and air gap for native and induced polarization image profiles are evaluated. By using the relationship between induced polarization and topographical structure, an induced polarization image of an alternating phase shift mask (PSM) is converted into a topographical image, which shows very good agreement with AFM measurement. Images of other material structures include a dielectric grating, chrome-on-glass grating, silicon CPU structure, BD-R and BD-ROM.
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Chung, Euiheon. "Super-resolution wide-field optical microscopy by use of Evanescent standing waves." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38594.
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Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2007.Vita.
Includes bibliographical references.
The development of high resolution, high speed imaging techniques allows the study of dynamical processes in biological systems. Optical fluorescence microscopy is an essential tool for investigations in many disciplines in biology and medicine with molecular specificity. The resolution of optical far-field microscopy has been limited by the wave nature of light. In this thesis, a microscopy technique, standing wave total internal reflection fluorescence (SW-TIRF), has been developed with resolution beyond the classical diffraction limit. The SW-TIRF approach modifies the point-spread function to effectively decrease the excitation wavelength by utilizing an evanescent standing wave, carrying high spatial frequency information near the interface between the specimen and a high refractive index substrate. Evanescent standing wave illumination is used to generate a sinusoidal, high-spatial frequency, fringe pattern on the specimen providing lateral resolution enhancement. Furthermore, the less than 100 nm penetration depth of the evanescent field from the substrate ensures a thin excitation region resulting in low background fluorescence. The first experimental realization of SW-TIRF in an objective-launched geometry demonstrates the potential for super-resolution imaging at high speed in wide-field microscopy.
(cont.) The super-resolution has been realized with the effective point-spread function providing better than a fifth of the emission wavelength or approximately 100 nm, which is better than twice that of conventional microscopy. In addition, imaging biological specimens with SW-TIRF demonstrated the performance revealing the fine actin cytoskeleton structures of fibroblasts. On the other hand, the surface plasmons induced by evanescent fields at a specific angle can generate an enhanced electric field which can effectively excite fluorophores near a metal coated surface. We observed a unique doughnut-shaped point-spread function of surface plasmon coupled emission and explained it with theoretical modeling using vector field theory. The combination of surface plasmon resonance fluorescence imaging and SW-TIRF resulted in a novel high-resolution microscopy, the standing wave surface plasmon resonance fluorescence (SW-SPRF) microscopy. These findings may allow super-resolution imaging with even higher sensitivity and signal-to-noise ratio at high imaging speed.
by Euiheon Chung.
Ph.D.
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Pawliuk, Peter Cornelius. "Evanescent field interactions in the scattering from cylinders with applications in super-resolution." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44809.
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The diffraction limit defines the maximum resolution of an imaging system that collects and focuses waves. This limited resolution arises from the finite length of the waves used to create the image. Therefore, the only way to increase the resolution is to use higher frequencies with shorter wavelengths. For situations in which increasing the frequency is not possible or not desirable, super-resolution imaging techniques can be applied to overcome the diffraction limit. Super-resolution is possible with the inclusion of evanescent waves, which exhibit unlimited spatial frequencies.
Evanescent waves decay exponentially away from their surface of origin so they are difficult to recover. One way to recover evanescent wave information is to scatter the wave from a small object. This scattering converts part of the evanescent wave into radiation that can propagate into the far-field where it can be detected. In order to characterize this conversion, the two-dimensional scattering of evanescent fields from a single cylinder and from multiple cylinders is investigated. The scattering models are derived using an analytical approach where the electromagnetic fields are broken down into cylindrical waves so that the boundary conditions on the cylinders can be applied directly. The incident field can be formulated from a vector plane-wave spectrum, which allows for an arbitrary combination of radiative and evanescent waves. Multiple cylinders of various sizes can be used to approximate the scattering from many two-dimensional objects. For simulating the imaging of objects buried underneath a surface, or near a planar interface, the model is separated into two dielectric half-spaces.
An example of a super-resolution application for these models is the simulation of apertureless near-field scanning optical microscopy (ANSOM). In ANSOM, a probe is placed in the extreme near-field of an object in order to scatter the evanescent fields that are formed by the illumination of the object. Images created by ANSOM are fundamentally different from traditional images and are difficult to interpret. The simulations provide insight into how the images are formed and what information they contain.
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Li, Cheng, Shin’ichiro Hayashi, Adrian Dobroiu, Chiko Otani, Kodo Kawase, Teruo Miyazawa, and Yuichi Ogawa. "Terahertz-wave absorption in liquids measured using the evanescent field of a silicon waveguide." American Institite of Physics, 2008. http://hdl.handle.net/2237/11977.
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Jia, Baohua, and n/a. "A study on the complex evanescent focal region of a high numerical aperture objective and its applications." Swinburne University of Technology, 2006. http://adt.lib.swin.edu.au./public/adt-VSWT20070205.150740.
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In recent years, optical near-field has received an ever-increasing attention owing to
its ability to localise optical signals beyond the diffraction limit. Optical near-field is
a non-propagating field existing in the close vicinity of a matter within a range less
than the wavelength of the illumination light and it carries the high spatial frequency
information showing the fine details of the matter.
An optical near-field can be generated by a near-field optical microscope with a
nano-aperture or a metal-coated fibre tip. However, common difficulties associated
with this approach, such as a fragile probe, a low throughput and signal-to-noise ratio,
and a slow response of gap controlling between the probe and the sample, make it
less applicable. Alternatively, optical near-field can be produced by total internal
reflection (TIR) occurring at the interface of a prism, which is capable of localising
the electromagnetic (EM) field in the close vicinity of the interface. However, in this
geometry, no confinement of the field can be achieved in the transverse direction,
whereas, in most applications such as optical trapping, micro-fabrication and optical
data storage, a transverse confinement of the light field is essential.
In order to achieve a transverse confinement of the light field, maintaining the
high spatial resolution of the optical near-field, and at the same time eliminating
the drawbacks associated with the conventional near-field optical microscope, a novel
near-field probe based on a high numerical aperture (NA) TIR objective combined
with annular illumination has been developed recently. In this arrangement, an
obstruction disk is inserted at the back aperture of the objective to block the light
with a convergence angle lower than the critical angle determined by the refractive
indices of the two media, resulting in a pure focused evanescent field in the second
medium.
The evanescent field produced by this method provides a useful tool for studying
light-matter interaction at the single molecule level not only because of its high
resolution but also due to its inherent merits such as no distance regulation, no heating
effect and simple experimental setup. But, the most significant advantage that makes
this method unique and superior to the other approaches in terms of producing the
optical near-field is that it allows the dynamic control of the focal field by simply
modulating the phase or amplitude or even the polarisation state of the incident beam
before it enters the objective so that complex illumination beams can be generated,
whereas in other fibre probe based approaches this goal is extremely difficult to achieve.
To make use of such a novel near-field probe, a thorough theoretical and
experimental investigation is required. A complete knowledge of the focused evanescent
field is a prerequisite for a wide range of applications including single molecule
detection, Raman spectroscopy, near-field non-linear imaging and near-field trapping.
Therefore, it is not only necessary but also urgent to exploit the focusing properties
of a focused evanescent field under complex field illumination both experimentally and
theoretically and this is the major aim of this thesis.
The complex fields, which are of particular interest in this thesis, are the radially
polarised beam and the Laguerre-Gaussian (LG) beam, because the former owns a
more compact circularly symmetric field distribution in the focal region when focused
by a high NA objective, while the latter is capable of rotating a trapped particle
by transferring the orbital angular momentum. Combining them with the focused
evanescent field is potentially able to induce novel functions in the near-field region,
which cannot be fulfilled by other near-field approaches. In this thesis, in order to
generate these two types of beams, a single liquid crystal spatial light modulator
(LCSLM) is employed to produce useful phase modulation to the incident beam.
Experimental characterisation of an evanescent focal spot is performed with
scanning near-field optical microscopy (SNOM), which is capable of providing the direct
mapping of the focused evanescent field not only because of its high spatial resolution
and its ability to detect the near-field and far-field signals simultaneously, but also due
to the motion of the piezzo-stage enables a three-dimensional characterisation of the
evanescent focal spot.
In this thesis, a SNOM system with an aluminum coated aperture probe is
implemented. The field distributions at both the interface and parallel planes with
a small distance away from the interface are obtained. To verify the applicability of
SNOM as a characterisation methodology, the field distribution in the focal region
of a high NA objective illuminated by a linearly polarised plane wave is measured
first. A focus splitting along the direction of incident polarisation is observed threedimensionally
near the interface under such a circumstance. It has been demonstrated
that the depolarisation effect plays an important role in determining the coupling
behaviour of the light into the fibre probe of SNOM. The good match between the
experimental results and theoretical predications confirms the validity of SNOM.
Theoretical investigation of a tightly focused radially polarised beam is undertaken
based on the vectorial-Debye diffraction theory because under the tight focusing of a
high NA objective, the vectorial nature of the highly localised field has to be carefully
considered in order to represent the field distribution accurately. The calculations
on the focusing properties of a radially polarised beam suggest that the longitudinal
field component in the focal region plays a dominant role in determining the overall
field distribution. Direct measurement of the focused evanescent radially polarised
beam in a three-dimensional manner near the interface is performed with SNOM. A
highly localised focal spot is achieved in the close vicinity of the coverglass. The
measured intensity distributions from SNOM show that correction of the focal spot
deformation associated with a linearly polarised beam is achieved by taking advantage
of the radially symmetric focal spot of a radially polarised beam. A smaller focal spot is
acquired due to the dominant longitudinal polarisation component in the focal region,
which possesses a more compact focal intensity distribution than that of the overall
field. The experimental results demonstrate a good agreement with the theoretical
expectations.
The fact that a radially polarised beam is capable of eliminating the focus
deformation often presented in the focal region of a high NA objective when a linearly
polarised beam is employed can be very useful in many applications, including microfabrication
using two-photon photopolymerisation technique. The theoretical study
on the two-photon point spread function (PSF) of a radially polarised beam indicates
that the focus elongation and splitting associated with a linearly polarised beam are
eliminated and the achievable lateral size of the focal spot is approximately a quarter
of the illumination wavelength, which is less than half of that under the illumination
of a linearly polarised beam. A further reductiont of the lateral size can be expected
by using annular radial beam illumination.
The investigation on the focusing properties of LG beams has also been one of
the major tasks of this thesis. Theoretical investigations of a focused evanescent LG
beam suggest that the phase shift induced by the boundary effect when a light beam
passes the interface satisfying TIR condition plays a vital role in determining the
overall shape of the total field distribution. A severe focal intensity deformation is
predicted theoretically in the case of focused evanescent LG beam illumination, which
might involve new physical phenomena when applied in the near-field trapping. Such
a focal intensity deformation is evidenced experimentally by the direct mapping result
obtained from the SNOM probe. A quantitative cross-section comparison with the
theoretical predication is conducted, which demonstrates a good agreement.
To achieve a controllable optical trap and rotation in the near-field region, complex
optical fields such as LG beams carrying orbital angular momentum, have been induced
for the manipulation of a polystyrene particle. The influence of the focal intensity
deformation on a near-field trapping has been thoroughly investigated. Rotation
motion of the particle is examined by mapping the two-dimensional (2D) transverse
trapping efficiency of the particle. Theoretical investigation reveals that a significant
tangential force component is generated on the particle when it is illuminated by a
focused evanescent LG beam. Such findings may prove useful in introducing a rotation
mechanism in near-field trapping.
The research investigations and methodologies described in this thesis provide a new
approach to characterise the near-field focal spot under complex field illumination.
It enhances the understanding of the novel near-field probe, thus opening the
pathway for numerous near-field applications including optical trapping, two-photon
excitation (photopolymerisation) and spectroscopy. The focal field rotation phenomena
demonstrated in this thesis may prove particularly beneficial in introducing a rotation
mechanism in near-field trapping using a focused evanescent field.
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Jia, Baohua. "A study on the complex evanescent focal region of a high numerical aperture objective and its applications." Australasian Digital Thesis Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20070205.150740/index.html.
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Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Micro-Photonics, 2005.A thesis submitted for the degree of Doctor of Philosophy, Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2005. Typescript. Bibliography: p. 129-142.
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Kuhn, Kevin John. "Evaluation of a planar optic waveguide as a platform for evanescent field chemical sensor development /." Thesis, Connect to this title online; UW restricted, 1993. http://hdl.handle.net/1773/8682.
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Thanyani, Simon Tshililo. "An assessment of two evanescent field biosensors in the development of an immunoassay for tuberculosis." Thesis, Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-05252009-231404.
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D'Alberto, Tiffanie Gabrielle. "Long-Period Gratings as Immuno-Diagnostic biosensors." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/30480.
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This research presents a novel biosensor which utilizes the refractive index sensitivity of a fiber optic long-period grating. The long period grating couples light from the forward propagating guided core mode of a single-mode fiber into discrete circularly symmetric cladding modes. Due to imperfections in the cladding surface, loss bands are seen in the transmission spectrum corresponding to the coupled wavelengths. Based on the phase-matching condition between the coupling and coupled modes, the loss bands shift with changes in the refractive index of the surrounding medium. The grating surface is chemically treated to covalently bond antibody to the cladding of the sensor. Treatment with the proper antigen increases the effective index seen by the cladding modes and affects the placement of the loss bands. This sensor demonstrates specific antigen binding capacity with loss band shifts of 10 nm or more. The device offers several advantages over the widely used Enzyme-Linked Immuno-Sorbent Assays. Diagnostic applications can be expanded beyond the tests presented here.Master of Science
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Valk, Bernd. "Investigation of nonlinear effects with ps-pulses and studies of evanescent field interaction in single mode fibres /." Bern : Universitätsdruckerei, 1985. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Gamez, Jimmy Ray. "The Effects of Diameter Fluctuations and Coiling on the Sensitivity of Sapphire Single Crystal Optical Fiber Evanescent Wave Fluorescence Sensors." Scholar Commons, 2009. https://scholarcommons.usf.edu/etd/1980.
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The purpose of this research was to determine the effect of diameter fluctuations on the sensitivity of sapphire multimode optical fibers used as evanescent wave fluorescence sensors. It was predicted that fluctuations in the diameter of the fiber would act as a series of bi-tapers converting lower order modes to higher order modes increasing the evanescent wave penetration depth thereby increasing the excitation of a cladding of fluorescent fluid. Induced fluorescence from the fluid cladding would then couple back into the fiber more efficiently increasing the sensitivity of the sensor.
The effect of coiling the fiber on the sensitivity of the sensor was also explored. Coiling the fiber converts lower order modes into higher order modes and increases the sensing length while maintaining a small probe size. However, coiling experiments produced unexpected results and in the course of studying these results a layer of material was discovered coating the surface of the sapphire fibers.
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Ash, William Mason III. "Total Internal Reflection Holographic Microscopy (TIRHM) for Quantitative Phase Characterization of Cell-Substrate Adhesion." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1564.
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Total Internal Reflection Holographic Microscopy (TIRHM) combines near-field microscopy with digital holography to produce a new form of near-field phase microscopy. Using a prism in TIR as a near-field imager, the presence of microscopic organisms, cell-substrate interfaces, and adhesions, causes relative refractive index (RRI) and frustrated TIR (f-TIR) to modulate the object beam's evanescent wave phase front. Quantitative phase images of test specimens such as Amoeba proteus, Dictyostelium Discoideum and cells such as SKOV-3 ovarian cancer and 3T3 fibroblasts are produced without the need to introduce stains or fluorophores. The angular spectrum method of digital holography to compensate for tilt anamorphism due to the inclined TIR plane is also discussed.
The results of this work conclusively demonstrate, for the first time, the integration of near-field microscopy with digital holography. The cellular images presented show a correlation between the physical extent of the Amoeba proteus plasma membrane and the adhesions that are quantitatively profiled by phase cross-sectioning of the holographic images obtained by digital holography. With its ability to quantitatively characterise cellular adhesion and motility, it is anticipated that TIRHM can be a tool for characterizing and combating cancer metastasis, as well as improving our understanding of morphogenesis and embryogenesis itself.
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Křepelka, Pavel. "NÁVRH OPTOVLÁKNOVÉHO BIOSENZORU SE SPEKTRÁLNÍ ANALÝZOU V BLÍZKÉ INFRAČERVENÉ OBLASTI." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-409090.
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This thesis deals with a measurement and interpretation of NIR spectra of bacterial cells and design of biosensor using this analytical technique. In the first chapter, there is introduction of current state of knowledge in the field of NIR spectroscopy in microbiology and technology of fiber optic biosensors. The summary of this chapter shows that NIR is a suitable technique for direct molecular analysis of bacteria, but it suffers from low sensitivity and insufficient interpretation of bacterial spectra. In the next part of the thesis, there is a theoretical background of spectral analysis techniques and technology of fiber optic sensors. In the practical part of this work, there is suggested the elimination of disadvantages of NIR spectroscopy in microbiology by a series of experiments used for interpretation of NIR spectra of bacteria and design of fiber optic sensor to increase sensitivity of this technique. In this work, spectral regions important for the identification of bacterial strains were determined and partially interpreted and the sensor for bacterial analysis capable of classifying strains based on 105 captured cells was designed. Therefore, the objectives of this work were fulfilled.
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Li, Muchen. "Determination of dissociation constant of DNA/DNA hybridization by three different surface techniques : comparison of surface plasmon resonance, fluorescent microarray and evanescent field fluorescence." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC028/document.
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Les biocapteurs sont des outils de détection et d'analyse puissants qui ont été largement utilisés dans les domaines de la santé, de la recherche biomédicale et de l’environnement. Cependant, différents biocapteurs utilisent différents transducteurs qui varient par la nature des substrats utilisés et par la chimie de surface. Tous ces paramètres peuvent avoir un effet sur les réactions biomoléculaires aux interfaces et conduire à des variations de la mesure de la constante de dissociation Kd. Dans ce contexte, ce travail de thèse visait à comparer trois techniques différentes : biopuce avec une détection par fluorescence, biocapteur à fluorescence par champ évanescent et biocapteur par résonance de plasmon de surface (SPR). Ces trois techniques ont été comparées pour la détermination de la constant de dissociation de l'hybridation de l'ADN. Pour la biopuce à fluorescence classique, le substrat est une lame de verre et la mesure est effectuée à la fin de l'expérience. Dans le cas du biocapteur à fluorescence à champ évanescent, le polystyrène est le substrat et une détection en temps réel est réalisée. La SPR est réalisée sur un film d'or mince. C'est une technique en temps réel et sans marquage. Les deux techniques basées sur la fluorescence nécessitent de marquer les cibles avec un fluorophore avant la mesure. Un facteur important déterminant la performance de l'analyse est la chimie de surface du capteur. Ici, nous avons optimisé la chimie de la surface de l'or pour le greffage d'ADN modifié thiol. Nous avons étudié deux méthodes de nettoyage: la solution de piranha et le plasma d'oxygène, dans le but d'obtenir une surface d'or propre sans oxydation de l'or. Ensuite, nous avons optimisé les paramètres lors de la mesure SPR comme par exemple la structure interfaciale du capteur, la force ionique .... Enfin, ces trois techniques ont été utilisées pour mesurer la constante de formation du duplex ADN/ADN. Les résultats ont montré que les Kd sont du même ordre de grandeur pour les trois techniques. De plus, pour les trois techniques, une augmentation de la densité de sonde de surface a entraîné une baisse d’affinité telle que mesuréeBiosensors are powerful detection and analysis tools that have been widely applied in pharmaceuticals, healthcare, biomedical research, and environmental monitoring. However different biosensors use different transducers and therefore different substrates and surface chemistries. All of these parameters may have an effect on the biomolecular reactions at the interface and lead to a deviation in dissociation constant Kd measurements. In this context, this PhD work aimed at comparing three different techniques: fluorescent microarray, evanescent field fluorescence biosensor and surface plasmon resonance (SPR) biosensor, to determine DNA hybridization Kd. For the classical fluorescence microarray, the substrate is a glass slide and the detection is performed at the end of the experiment. In the case of evanescent field fluorescence biosensor, polystyrene is the substrate and it permits a real-time detection. SPR is performed on thin gold film. It is a real-time and a label-free technique. The two fluorescent based techniques require to label the targets with fluorescent dyes prior to the measurements. One important factor determining the performance of the analysis is the surface chemistry of the sensor chip. Herein, we have optimized gold surface chemistry for thiol modified DNA grafting. We studied two cleaning methods: piranha solution and oxygen plasma, aiming at obtaining a clean gold surface without oxidation of the gold. Then, we optimized SPR assay parameters such as interfacial structure of sensor chip, ionic strength... After, these three techniques were used to measure the DNA hybridization Kd. The results showed that the Kds measured are similar for the three techniques. In addition, increasing surface probe density resulted in an increase of Kd of DNA hybridization
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Huda, Gazi Mostafa. "EFFECT OF A SILICON TIP ON ABSORPTION CROSS SECTION, FIELD ENHANCEMENT, AND LOCALIZED SURFACE PLASMON RESONANCE OF DIFFERENT SIZED GOLD NANOPARTICLES UNDER EVANESCENT WAVE ILLUMINATION." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/114.
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We have numerically investigated the influence of a nanoscale silicon tip in proximity to an illuminated gold nanoparticle. We describe how the position of the high-permittivity tip and the size of a nanoparticle impact the absorption, peak electric field and surface plasmon resonance wavelength under different illumination conditions. We detail the finite element method (FEM) approach we have used for this, whereby we specify a volume excitation field analytically and calculate the difference between this source field and the total field (i.e., scattered-field formulation). We show that a nanoscale tip can locally enhance the absorption of the particle as well as the peak electric field at length scales far smaller than the wavelength of the incident light.
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Lombardo, David. "Design and Fabrication of Suspended Waveguides With Photonic Grating Structures." University of Dayton / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1591796311145344.
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Charlton, Christy. "Quantum Cascade Lasers for Mid-Infrared Chemical Sensing." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/13953.
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The mid-infrared (MIR) spectral range (2-20 m) is particularly useful for chemical sensing due to the excitation of fundamental rotational and vibrational modes. In the fingerprint region (10-20 m), most organic analytes have unique absorption patterns; absorption measurements in this region provide molecule-specific information with high sensitivity.
Quantum cascade lasers (QCLs) present an ideal light source for (MIR) chemical sensing due to their narrow linewidth, high spectral density, compact size, and ease of fabrication of nearly any MIR wavelength. As the emission wavelength is dependent on layer size within the heterostructure rather than material composition, various wavelengths in the MIR can be achieved through bandstructure engineering.
High sensitivity measurements have been achieved in both gas and liquid phase by developing integrated sensing systems. The laser emission frequency is selected to match a strong absorption feature for the analyte of interest where no other interfering bands are located. A waveguide is then developed to fit the application and wavelength used.
Gas sensing applications incorporate silica hollow waveguides (HWG) and an OmniGuide fiber (or photonic bandgap HWG). Analyte gas is injected into the hollow core allowing the HWG or OmniGuide to serve simultaneously as a waveguide and miniaturized gas cell. Sensitivities of parts per billion are achieved with a response time of 8 s and a sample volume of approximately 1 mL.
Liquid sensing is achieved via evanescent wave measurements with planar waveguides of silver halide (AgX) and gallium arsenide (GaAs). GaAs waveguides developed in this work have a thickness on the order of the wavelength of light achieving single-mode waveguides, providing a significant improvement in evanescent field strength over conventional multimode fibers. Liquid samples of L volume at the waveguide surfaces are detected.
QCLs have begun to be utilized as a light source in the MIR regime over the last decade. The next step in this field is the development of compact and highly integrated device platforms which take full advantage of this technology. The sensing demonstrations in this work advance the field towards finding key applications in medical, biological, environmental, and atmospheric measurements.
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Sergides, M. "Optical manipulation of micro- and nano-particles using evanescent fields." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1410938/.
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We present a study of the manipulation of micro-particles and the formation of optically bound structures of particles in evanescent wave traps. Two trapping geometries are considered: the first is a surface trap where the evanescent field above a glass prism is formed by the interference of a number of laser beams incident on the prism-water interface; the second uses the evanescent field surrounding a bi-conical tapered optical fibre that has been stretched to produce a waist of sub-micron diameter. In the surface trap we have observed the formation of optically bound one- and two-dimensional structures of particles and measured the binding spring constant by tracking particle motion and the extent of the particle’s Brownian fluctuations. Additionally, we have measured the inter-particle separations in the one-dimensional chain structures and characterised the geometry of the two-dimensional arrays. In the tapered optical fibre trap we demonstrated both particle transport for long distances along the fibre, and the formation of stable arrays of particles. We present the fabrication of tapered optical fibres using the 'heat-and-pull` technique, and evanescent wave optical binding of micro-particles to the taper. Calculations of the distribution of the evanescent field surrounding a tapered fibre are also presented. We show that the combination of modes can give control over the locations of the trapping sites. Additionally, we show how the plasmon resonance of metallic nano-particles can be exploited to enhance the optical trapping force, and suggest how a bi-chromatic nano-fibre trap for plasmonic particles may be implemented. In both experiments we implement video microscopy to track the particle locations and make quantitative measures of the particle dynamics. The experimental studies are complemented by light scattering calculations based on Mie theory to infer how the geometries of the particle structures are controlled by the underlying incident and scattered optical fields.
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Foubert, Kevin. "Etude en champ proche optique de structures nanophotoniques couplées." Thesis, Dijon, 2011. http://www.theses.fr/2011DIJOS091.
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Depuis une vingtaine d’années, l’optique bénéficie des avancées considérables de la microélectronique.Ainsi, il est maintenant possible de produire, guider, confiner ou encore ralentirla lumière sur puce à une échelle sub-longueur d’onde. Dans cette thèse, nous étudions de telscomposants par l’intermédiaire d’un microscope en champ proche optique (SNOM).La première partie présente une vision d’ensemble de la situation actuelle en nanophotoniqueintégrée sur substrat diélectrique. Elle expose plusieurs enjeux et faits marquants récents dansce domaine. Elle introduit également le principe physique et le fonctionnement d’un SNOMdans les grandes lignes.La seconde partie est consacrée à la microscopie en champ proche optique d’un point devue instrumental. Après une analyse physique, nous détaillons le montage de notre propremicroscope sur le banc de caractérisation optique du laboratoire, avant d’analyser la formationdes images optiques obtenues avec cette technique.La troisième partie concerne l’étude de guides d’onde couplés en Silicium sur isolant (SOI),dans lesquels s’intègrent des nano-cavités optiques. Les phénomènes de couplage par recouvrementde champs évanescents sont étudiés numériquement et analytiquement. L’analyse de cesstructures grâce au SNOM nous a permis d’une part de vérifier la validité de ces modèles, etd’autre part d’observer directement le guidage et le confinement de la lumière dans un milieude faible indice de réfraction. Nous montrons cependant que ces résultats restent très sensiblesaux aléas de fabrication. Enfin, nous mettons en évidence grâce au SNOM et à des mesuresspectrales que la description de structures de N cavités juxtaposées peut être approchée par lathéorie des modes couplésSince the end of the XXth century, optics benefits from significant breakthrough comingfrom the micro-electronic technologies. It is thus now possible to produce, guide, slow downor even trap light on a chip at a sub-wavelength scale. In this thesis, we study such opticalcomponents thanks to a Scanning Near-Field Optical Microscope (SNOM).The first part exposes an overall view of the current situation in the field of dielectricsubstrate integrated nanophotonics. Some of the recent outstanding issues and results are hereintroduced, as well as the general principle and the necessary tools to operate a SNOM.The second part is dedicated to optical near-field microscopy, technically speaking. Thephysical rules are here developed. Then we detail the instrumental set up of our own SNOMon our optical characterization bench. We end by analysing the optical images formation witha SNOM.The third part bears upon the study of Silicon-on-Insulator (SOI) coupled waveguides whereoptical nano-cavities could be inserted, by resorting to the previously implemented SNOM.Overlapping evanescent fields induced coupling phenomena are numerically and analyticallystudied. The use of the SNOM allowed us here to check the validity of our models. Besides,we have directly observed thanks to this instrument the guiding and confinement of light ina low refractive index media. However, we show that this phenomenon is highly subjected tofabrication uncertainties. Finally, we use the SNOM and spectral measurements in order todemonstrate that systems of N coupled nanocavities could be described with a simple coupledmodes model
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Li, Jing. "Applications of optical-cavity-based spectroscopic techniques in the condensed phase." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:d6a0c476-e67f-4390-a63a-e3cb9e60bf2c.
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Cavity ring-down spectroscopy (CRDS) and cavity enhanced absorption spectroscopy (CEAS) are two well-established absorption spectroscopic techniques originally developed for gas-phase samples. Condensed-phase applications of these techniques still remain rare, complicated as they are by additional background losses induced by condensed-phase samples as well as the intracavity components in which the sample is constrained. This thesis is concerned with the development and application of optical-cavity-based techniques in the condensed phase. Polarization-dependent evanescent wave CRDS (EW-CRDS) has been used to study the molecular orientation at the solid/air and solid/liquid interfaces. An increase in average orientation angle with respect to the surface normal has been observed for both methylene blue and coumarin molecules as a function of coverage at the fused silica/air interface. An orientation-angle-dependent photobleaching of pyridin molecules at the fused silica/methanol interface have also been observed. EW-CRDS has also been used to monitor slow in situ photobleaching of thin dye films deposited on the prism surface. The photobleaching dynamics is interpreted as a combination of first- and second-order processes. A significant fraction of this thesis has been devoted to studying magnetic field effects (MFEs) on the kinetics of the radical pair (RP) reactions in solution, in an effort to understand the ability of animals to sense the geomagnetic field. Two novel optical-cavity-based techniques – broadband CEAS (BBCEAS) and CRDS have been developed for this purpose. BBCEAS uses a supercontinuum (SC) source as the cavity light source and a CCD camera as photodetector, enabling simultaneous acquisition of absorption spectrum across the whole visible region (400 – 800 nm). In CRDS, a tunable optical parametric oscillator has been used as the cavity light source. Combined with the switching of external magnetic field (SEMF) method, this technique allows the decay kinetics of the geminate RPs to be monitored, with nanosecond resolution. Both BBCEAS and CRDS provide sensitivity superior to single-pass transient absorption (TA), a technique traditionally used in the MFE studies. A series of photochemical systems have been studied by BBCEAS and CRDS, respectively, among which, the MFEs of drosophila melanogaster cryptochrome has been observed. Importantly, this is the first time an MFE has been observed in an animal cryptochrome, and provides key supporting evidence for the cryptochrome hypothesis of magnetoreception in animals. Besides the optical-cavity-based techniques, a novel fluorescence detection method of MFEs has also been demonstrated. This technique proved ultrahigh sensitivity when applicable.
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Zacher, Thomas. "Utilisation of evanescent fields for the characterisation of thin biosensing layer systems." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964808854.
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Neil, Simon R. T. "Condensed-phase applications of cavity-based spectroscopic techniques." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:4431e46e-1226-4950-aa5d-ce22e0309ba9.
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This thesis describes the development and application of condensed-phase cavity-based spectroscopic techniques - namely cavity ring-down spectroscopy (CRDS); cavity enhanced absorption spectroscopy (CEAS); broadband cavity enhanced absorption spectroscopy (BBCEAS) and evanescent wave (EW) variants of all three. The recently-developed cavity technique of EW-broadband cavity enhanced absorption spectroscopy (EW-BBCEAS) has been used—in combination with a supercontinuum source (SC) and a sensitive, fast readout CCD detector—to record of the full visible spectrum (400–700 nm) of a silica-liquid interfacial layer (with an effective thickness ca. 1 µm), at rapid acquisition rates (> 600 Hz) that are sufficient to follow fast kinetics in the condensed phase, in real time. The sensitivity achieved (Amin= 3.9 x 10-5) is comparable with previous EW-CRDS and EW-CEAS studies, but the spectral region accessed in this broadband variant is much larger. The study of liquid|air interfaces using EW cavity-based techniques is also illustrated for the first time. The first application of BBCEAS to the analysis of microfluidic samples, flowing through a microfluidic chip, is illustrated. Proof-of-principle experiments are presented, demonstrating the technique’s ability to provide full visible broadband spectral measurements of flowing microfluidic droplets, with both high detection sensitivity (αmin < 10-2 cm-1) and excellent spatial and temporal resolution: an SC light source and sensitive, fast readout CCD allowed measurement repetition rates of 273 Hz, whilst probing a very small sample volume (ca. 90 nL). A significant portion of this thesis is devoted to demonstrating the powerful capabilities of CEAS, CRDS and BBCEAS in monitoring radical recombination reactions and associated magnetic field effects (MFEs) in solution. The efficacy of CEAS as a high-sensitivity MFE detection method has been established in a proof-of-principle study, using narrow band CEAS in combination with phase-sensitive detection: MFE-induced absorbance changes of ca. 10-6 could be detected using the modulated CEAS technique and the data are shown to be superior to those obtained using conventional transient absorption (TA) methods typically employed for MFE measurements. The powerful capabilities of CRDS in monitoring radical recombination reactions and associated MFEs are also demonstrated. In particular, a pump-probe CRDS variant allows not only high sensitivity (Amin on the order 10-6), but also sub-microsecond time-resolution. Combined, these features represent significant advantages over TA. Finally, SC-BBCEAS is used to measure full visible spectra of photoinduced reactions and their MFEs. The applicability of this approach to in vitro MFE studies of Drosophila cryptochrome is demonstrated—the results mark the first in vitro observation of a magnetic field response in an animal cryptochrome, a key result supporting the hypothesis that cryptochromes are involved in the magnetic sense in animals.
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SCHUTZMANN, STEFANO. "Towards hybrid sol-gel devices for optoelectronic biosensors." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2006. http://hdl.handle.net/2108/202687.
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I sensori per la rilevazione di sostanze inquinanti in acqua, terra e atmosfera così come i dispositivi biosensori per l’identificazione di proteine ed enzimi, rappresentano un interessantissimo ambito di ricerca con forti applicazioni in campo industriale. In questo contesto, una promettente possibilità è rappresentata dallo sviluppo di sensori basati sull’optoelettronica dato che essi assicurano un’alta sensibilità, una buona stabilità meccanica, la possibilità di miniaturizzare i dispositivi e di produrli su larga scala. In particolare, negli ultimi anni molti sforzi sono stati orientati allo sviluppo di sensori ottici a guida d’onda. Il principio di funzionamento di questo tipo di dispositivi è basato sull’interazione fra la componente del campo evanescente di un’onda guidata e la regione che si vuole analizzare.
Lo sviluppo di dispositivi optoelettronici, d’altra parte, richiede la possibilità di sintetizzare materiali dalle qualità ottiche appropriate. In particolare, la possibilità di cambiare opportunamente l’indice di rifrazione rappresenta un aspetto fondamentale per la fabbricazione di dispositivi reali. I materiali ibridi organico-inorganici sintetizzati con la tecnologia sol-gel rappresentano una valida alternativa ai più tradizionali metodi per la fabbricazione di dispositivi ottici integrati come la tecnica dello scambio ionico o la CVD (chemical vapor deposition). Questa tecnica ibrida permette lo sviluppo di materiali dalle caratteristiche nuove in modo semplice ed economico.
La presente tesi tratta dello sviluppo, della sintesi e della caratterizzazione di guide d’onda sol-gel ibride per possibili applicazioni come sensori ottici a guida d’onda.
La caratterizzazione ottica dei dispositivi è stata effettuata principalmente utilizzando un apparato sperimentale sviluppato ed ottimizzato dal candidato durante il primo periodo del lavori di dottorato. Il setup si basa sia sulla tecnica m-line sia sulla tecnica dell’angolo di Brewster e rappresenta uno strumento semplice e a basso costo per l’analisi dell’indice di rifrazione di film sottili. I risultati mostrano che l’apparato permette la stima dell’indice di rifrazione a diverse lunghezze d’onda nel visibile e nel vicino infrarosso di film aventi spessore da poche decine di nanometri a diversi micron. L’errore nella determinazione dell’indice di rifrazione è compreso nel range ±0.001-0.003 a seconda della lunghezza d’onda e delle proprietà del campione. L’ottima accuratezza e affidabilità del nostro apparato è anche confermata dal confronto con i risultati ottenuti da misure di ellissometria spettroscopica.
Molti sforzi sono stati indirizzati alla sintesi e caratterizzazione di diverse guide d’onda sol-gel deposte su substrati sia di vetro che di silicio. I campioni sono stati caratterizzati mediante misure di indice di rifrazione di perdite ottiche usando la tecnica dell’analisi della luce di scattering. I risultati hanno mostrato la possibilità di modulare l’indice di rifrazione fra 1.45 e 1.90 semplicemente modificando la sintesi chimica e i trattamenti post-deposizione. Perdite di propagazione dell’ordine di 3-10 dB/cm sono state misurate sui nostri campioni a seconda della lunghezza d’onda, della polarizzazione del modo selezionato. Questi valori sono piuttosto comuni per guide d’onda planari di tipo sol gel ibrido.
Durante questo lavoro sono state inoltre sintetizzate a caratterizzate guide d’onda drogate con molecole luminescenti al fine di mostrare la possibilità di usare le nostre strutture guidanti come dispositivi attivi. Si è investigata anche l’opportunità di modulare l’indice di rifrazione di film ibridi utilizzando le proprietà di molecole fotosensibili esposte a luce ultravioletta.
Infine, l’ultimo periodo di tesi è stato dedicato con successo ad investigare la possibilità di utilizzare la guide d’onda sol-gel ibride come strutture-base per lo sviluppo di sensori ottici a fluorescenza. A tal fine sono state condotte misure di fluorescenza eccitata mediante onda evanescente.Environment sensors for the detection of polluting substances in water, earth and atmosphere as well as biosensor devices for the recognition of proteins and enzymes represent a very intriguing topic for both research and industrial applications. In this framework, a very promising alternative is represented by the development of sensors based on optoelectronic technology since they combine high sensitivity, mechanical stability, miniaturization and the possibility of mass-production. In particular, extensive research have been devoted to evanescent-field-based optical waveguide sensors. The operation principle of this kind of devices is based on the interaction between the evanescent field component of a guided optical wave and the monitoring region. The development of optoelectronic devices requires the possibility to design materials with suitable optical properties. In particular, the possibility of changing appropriately the refractive index represents a fundamental step for design and fabrication of real devices. Hybrid organic-inorganic materials synthesized by sol-gel technology seem to be a valid alternative to more traditional methods such as ion exchange or chemical vapor deposition for fabrication of integrated optical devices. Hybrid materials combining organic and inorganic networks allow the design and fabrication of new materials with appropriate features in a simple and economic way. This thesis reported on the design, synthesis and characterization of hybrid sol-gel-based waveguides for possible applications as fluorescence-based optical sensors. Optical characterization has been accomplished using a home-made experimental setup built and optimized by the candidate during the first period of the PhD fellowship. The setup is based on both m-line and Brewster methods and represents a completely non-destructive, low cost and very simple tool for thin film refractive index estimation. Results have shown that the apparatus allows the estimation of refractive index at different wavelengths in the visible and near infrared spectral region for films having thickness from few tens of nanometers to several micrometers. The error in refractive index determination was in the range ±0.001-0.003, depending on wavelength and sample features. Comparison with results obtained by ellipsometric measurements have confirmed the high accuracy and reliability of our setup. Many efforts was dedicated to the synthesis and characterization of different hybrid sol-gel waveguides grown both on silicon and glass substrates. Samples were characterized by refractive index determination and propagation loss measurements using scattered light detection technique. Results have shown the possibility to modulate quite easily the refractive index from 1.45 to about 1.90 playing on the chemical synthesis and on the post-deposition treatments. Propagation loss coefficients in the range 3-10 dB/cm were commonly obtained on our samples, depending on wavelengths, polarization, and mode selected. These values are quite common for planar organic/inorganic sol-gel based waveguides. Waveguides doped with fluorescent molecules were synthesized and characterized showing the possibility to use our structures as active optical devices. The modulation of refractive index of hybrid films using photosensitive molecules was investigated exposing films to different UV light dose. Moreover, first efforts to fabricate channel waveguides exploiting photolithographic techniques were accomplished. Finally, the possibility to use hybrid sol-gel planar waveguides as building blocks for a fluorescence-based optical sensor has been demonstrated performing measurements of fluorescence excited by guided wave evanescent field.
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Bugler-Lamb, Samuel Lloyd. "The quantum vacuum near time-dependent dielectrics." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/29879.
Full textAbstract:
The vacuum, as described by Quantum Field Theory, is not as empty as classical physics once led us to believe. In fact, it is characterised by an infinite energy stored in the ground state of its constituent fields. This infinite energy has real, tangible effects on the macroscopic clusters of matter that make up our universe. Moreover, the configuration of these clusters of matter within the vacuum in turn influences the form of the vacuum itself and so forth. In this work, we shall consider the changes to the quantum vacuum brought about by the presence of time-dependent dielectrics. Such changes are thought to be responsible for phenomena such as the simple and dynamical Casimir effects and Quantum Friction. After introducing the physical and mathematical descriptions of the electromagnetic quantum vacuum, we will begin by discussing some of the basic quasi-static effects that stem directly from the existence of an electromagnetic ground state energy, known as the \textit{zero-point energy}. These effects include the famous Hawking radiation and Unruh effect amongst others. We will then use a scenario similar to that which exhibits Cherenkov radiation in order to de-mystify the 'negative frequency' modes of light that often occur due to a Doppler shift in the presence of media moving at a constant velocity by showing that they are an artefact of the approximation of the degrees of freedom of matter to a macroscopic permittivity function. Here, absorption and dissipation of electromagnetic energy will be ignored for simplicity. The dynamics of an oscillator placed within this moving medium will then be considered and we will show that when the motion exceeds the speed of light in the dielectric, the oscillator will begin to absorb energy from the medium. It will be shown that this is due to the reversal of the 'radiation damping' present for lower velocity of stationary cases. We will then consider how the infinite vacuum energy changes in the vicinity, but outside, of this medium moving with a constant velocity and show that the presence of matter removes certain symmetries present in empty space leading to transfers of energy between moving bodies mediated by the electromagnetic field. Following on from this, we will then extend our considerations by including the dissipation and dispersion of electromagnetic energy within magneto-dielectrics by using a canonically quantised model referred to as 'Macroscopic QED'. We will analyse the change to the vacuum state of the electromagnetic field brought about by the presence of media with an arbitrary time dependence. It will be shown that this leads to the creation of particles tantamount to exciting the degrees of freedom of both the medium and the electromagnetic field. We will also consider the effect these time-dependencies have on the two point functions of the field amplitudes using the example of the electric field. Finally, we will begin the application of the macroscopic QED model to the path integral methods of quantum field theory with the purpose of making use of the full range of perturbative techniques that this entails, leaving the remainder of this adaptation for future work.
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Sabek, Jad. "Combination of nanophotonic biosensors and light-assisted immobilization procedures for the detection of cardiac biomarkers." Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/124821.
Full textAbstract:
[ES] El cuidado de la salud es un campo en el que la detección precoz de enfermedades está cobrando cada vez más importancia. Hoy en día, profesionales y ciudadanos demandan que las técnicas de diagnóstico sean de alta calidad, tanto para el sistema de sanidad privado como para el público. Cuando se utilizan técnicas de diagnóstico de manera inadecuada, eso puede acarrear bastantes consecuencias, tales como un serio peligro sobre la salud y la sobrecarga técnica y económica de los servicios de salud. Eso es debido a que las técnicas de diagnóstico disponibles hoy en día son demasiado costosas, centralizadas en laboratorios y necesitan profesionales altamente cualificados para poder llevar a cabo dichas tareas, lo que conllevaría una demora en el tiempo, siendo este muchas veces vital para los enfermos. Es muy necesario, por lo tanto, reflexionar sobre la necesidad y emergencia de tales prácticas preventivas, especialmente para enfermedades de alto riesgo como el cáncer, el Alzheimer o la primera causa de muerte en el mundo, las enfermedades cardiovasculares.
En este contexto, el objetivo principal del trabajo realizado durante esta Tesis Doctoral es ayudar a superar estos problemas mediante la exploración de la posibilidad de utilizar tecnología fotónica para el desarrollo de sistemas de análisis que puedan ser utilizados para el diagnóstico y pronóstico de las enfermedades cardiovasculares. Este objetivo se ha abordado mediante la combinación de la tecnología nanofotónica, consistiendo en la nanofabricación de las estructuras PBG de sensado que ofrece varios beneficios, como una alta sensibilidad, una extrema reducción de tamaño y un proceso de fabricación compatible con el de la industria microelectrónica, con un método de biofuncionalización obteniendo una capa de bioreconocimiento estable y selectiva mediante el uso de la reacción TEC asistida por luz capaz de proporcionar unas capas de bio-reconocimiento extremadamente finas con una inmovilización espacialmente selectiva.[CAT] L'atenció a la salut és un camp en què la detecció precoç de malalties està cobrant cada vegada més importància. Hui en dia, professionals i ciutadans demanen que les tècniques de diagnòstic siguin d'alta qualitat, tant per al sistema de sanitat privat com per al públic. Quan s'utilitzen tècniques de diagnòstic de manera inadequada, això pot comportar bastants conseqüències, com ara, un seriós perill sobre la salut i la sobrecàrrega tècnica i econòmica dels serveis de salut. Això és degut al fet que les tècniques de diagnòstic disponibles hui en dia són molt costoses, centralitzades en laboratoris i necessiten professionals altament qualificats per poder realitzar aquestes tasques, lo que comportaria a una demora en el temps que moltes vegades es vital pels malalts. És molt necessari, per tant, reflexionar sobre la necessitat i emergència de tals practiques preventives, especialment per a malalties d'alt risc com el càncer, l'Alzheimer o la primera causa de mort al món, les malalties cardiovasculars. En aquest context, l'objectiu principal del treball realitzat durant aquesta Tesi Doctoral és ajudar a superar aquests problemes mitjançant l'exploració de la possibilitat d'utilitzar tecnologia fotònica per al desenvolupament de sistemes d'anàlisis que puguin ser utilitzats per al diagnòstic i pronòstic de les malalties cardiovasculars. Aquest objectiu s'ha abordat mitjançant la combinació de la tecnologia nanofotònica, consistint en la nanofabricació de les estructures de detecció de PBG fotòniques que ofereix diversos beneficis, com una alta sensibilitat, una extrema reducció de mida i un procés de fabricació compatible amb el de la indústria microelectrònica, amb un mètode de biofuncionalització obtenint una capa de bio-reconeixement estable i selectiva mitjançant l'ús de la reacció TEC assistida per llum capaç de proporcionar unes capes de bioreconeixement extremadament fines amb una immobilització espacialment selectiva. preventives, especialment per a malalties d'alt risc com el càncer, l'Alzheimer o la primera causa de mort al món, les malalties cardiovasculars. En aquest context, l'objectiu principal del treball realitzat durant aquesta Tesi Doctoral és ajudar a superar aquests problemes mitjançant l'exploració de la possibilitat d'utilitzar tecnologia fotònica per al desenvolupament de sistemes d'anàlisis que puguin ser utilitzats per al diagnòstic i pronòstic de les malalties cardiovasculars. Aquest objectiu s'ha abordat mitjançant la combinació de la tecnologia nanofotònica, consistint en la nanofabricació de les estructures de detecció de PBG fotòniques que ofereix diversos beneficis, com una alta sensibilitat, una extrema reducció de mida i un procés de fabricació compatible amb el de la indústria microelectrònica, amb un mètode de biofuncionalització obtenint una capa de bio-reconeixement estable i selectiva mitjançant l'ús de la reacció TEC assistida per llum capaç de proporcionar unes capes de bioreconeixement extremadament fines amb una immobilització espacialment selectiva.
[EN] Healthcare is a field where the early detection of diseases is becoming more and more important. Nowadays, professionals and citizens demand high quality diagnosis techniques offered by both private and public health systems. When the application of diagnostic tests is not adequate, different consequences can be observed such as health hazard and technical and economic overload of health services. This is due to the fact that the diagnostic techniques available are expensive, centralized in laboratories and with the need for highly qualified professionals to carry out these tasks, what can fundamentally lead to delays in time, being critical for the patient's health. It is very necessary, therefore, to reflect on the need and emergency of such preventive practices, especially for high-risk diseases such as cancer, Alzheimer or the first cause of death in the world, the cardiovascular diseases. Within this context, the main objective of the work done during this PhD Thesis is to help on overcoming these problems by exploring the possibility of using photonic technology for the development of analysis devices which might be used for the early diagnosis and prognosis of cardiovascular diseases. This objective has been addressed by combining nanophotonic technology, by the nanofabrication of the photonic PBG sensing structures, which provides several benefits such as a high sensitivity, an extreme size reduction and a fabrication process being compatible with that from the microelectronics industry, with a light-assisted biofunctionalization method forming a stable and selective biorecognition layer using TEC reaction able to provide extremely thin biorecognition layers with a spatially-selective immobilization.
Sabek, J. (2019). Combination of nanophotonic biosensors and light-assisted immobilization procedures for the detection of cardiac biomarkers [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/124821
TESIS
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Li, Xia. "Evanescent field coupled microdisk cavities." 2007. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-2222/index.html.
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Lin, Chin Sung, and 林金松. "Near-field imaging of the interactions of evanescent fields." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/17012470111052025502.
Full textAbstract:
碩士國立臺灣海洋大學
光電科學研究所
92
The principal goal of present thesis is to study the near-field interactions between evanescent fields at the TIR interface and the evanescent fields generated by the total internal reflection inside the prism. We use light sources with different wavelengths, polarization directions, and different incident directions in our experiment. By changing the experimental conditions, the corresponding period and intensity of interference patterns of evanescent fields were observed to realize the degree of interfering influence of evanescent fields. The near-field images of interactions of evanescent fields provide the novel method for the application of near-field optics. The main instrumentation of a tapping-mode tuning fork force sensing and short fiber probe near-field scanning optical microscope (TMTF-NSOM) are used to measure the interactive signal of evanescent fields at the TIR interface, the comparisons between experimental and calculated results are analyzed and discussed as well.
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Zhan, Jing-Hong, and 詹景宏. "The Evanescent-field Excitation Method and Its Application." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/88368828004256210637.
Full textAbstract:
碩士國立清華大學
電機工程學系
85
The determination of propagation constant β for waveguiding structures is important both in intergrated- and fiber-optics because the designs of many optical waveguide devices such as directional couplers, polarizers, etc., depend on β. Except for those elementary three-layered step-index planar structures, the methods of finding β or dispersion relationship in optical waveguides are generally regarded as complicated ones and these materials are normally covered in graduate-level textbooks. Today, in-depth knowledges of guided-wave optics in conjunction with numerical techniques or the coupled-mode theory seem critical in analyzing or designing waveguiding structures and thereby potential researchers are discouraged from these interesting areas! With the familiar Fresnel's law of the lightwave reflection/transmission in the interface between two media learned in the Junior year, this thesis introduces a computationally and conceptually easy approach to find β for multi-planar waveguiding structures and thereby it is worth being included in textbooks for undergraduates. This proposed method, named evanescent-field excitation, should appear in undergraduate texts soon. We believe. Other than planar waveguides, optical components based on fibers with a cylindrical geometry are also considered here. This thesis investigates doubly-clad cylindrical waveguides because of novel filtering properties in presence. A new kind of formulation incorporation the Goods-Hanchen shift was used to tell the power transmittance in such structures. To our best knowledge, the well-known Goos-Hanchen shift phenomenon is applied to estimate the transmittance of guided wave in fiber-optic components for the first time. Although some approximations are invoked, this method is applicabel for further complicated structures.
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Lin, Gong-Cheng, and 林恭政. "Fabrication and Application of the Evanescent-Field Fiber Devices." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/80821032976982108711.
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碩士大同大學
光電工程研究所
89
The side-polished fiber is a very fundamental and important component in making passive or active fiber devices. The polished surface must be very close to the fiber core sufficiently in order to interact effectively with the evanescent fields in the fiber. The transmission and properties of guide modes in a leaky step-index planar waveguide have been discussed to analyze such a side-polished fiber. In this thesis, we successfully demonstrate a new method to fabricate side-polished fibers with the polish surface to be near to fiber core about 0.1μm. We also propose a new measurement method of the cladding thickness by using the characteristics of the polish machine. We have detailed studied the fabrication processes and performances of the optical devices, such as fiber temperature sensors (sensitivity=-0.4dB/℃), optical sensors, optical attenuators (attenuate loss=50dB), temperature switches (extinction ration=110dB), and optical couplers (tuning ration from 0% to 25%), and all of such devices are based on the side-polished fiber structure that we proposed in this thesis.
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Li, Jiang-Yi, and 李建億. "Verification of 3D Resolution in Nanometer Range in Evanescent Field." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/77720710929554283716.
Full textAbstract:
碩士國立臺灣大學
應用力學研究所
93
Single-molecule detection (SMD) provides a way to observe and measure the behavior of single molecule directly. In the past ensemble measurements involving a large number of molecules, the differences between individual molecule are ignored. Therefore, SMD provides powerful tools to look into biomolecules. However, fluorescent microscopy is limited in its resolution by the Rayleigh criterion at ~250nm. On the other end of the size spectrum, fluorescence resonance energy transfer (FRET) provides a way to probe the events under 10nm. Distance measurements in the range of 10-250nm is the choke point of most techniques. Motivation of this thesis is originated from verifying the three-dimensional resolution in nanometer range of total internal reflection fluorescent microscopy (TIRFM) by using atomic force microscopy (AFM). Fluorescent beads are affixed to cantilever tip through chemical modification and use property of the piezoscanner which can resolve displacement in nanometer range. The tip is moved by piezoscanner and the images are collected by CCD simultaneously. With comparison of data of AFM and TIRFM, the resolution of TIRFM can be confirmed. To quantify horizontal displacement, this paper use Gaussian curve to fit the distribution of intensity profile of single fluorescent molecule. The center position of fluorescent molecule can correspond to the peak of fitting curve. The change of vertical distance can be determined from the change of intensity and penetration depth. To show that TIRFM is able to observe and quantify signal transduction in cell or between cells, we observe the phenomenon that GFP adsorb on the coverslip. Distinct from other fluorescent techniques that only observe the dynamic motion in the transverse plane, TIRFM is able to observe the three-dimensional motion of single molecule in real time. Quantum dot has a variety of features such as lifetime long as ten hours and only one wavelength for excitation. To make use of the characteristic of quantum dot and excellent resolution of TIRFM, it will be revolutionary of single-molecule detection in cell and between cells.
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Yang, Wen-Jui, and 楊文睿. "Nano optical surface plasmon enhancement of the interfered evanescent field intensity." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/24302837926494833733.
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Wan-LingTseng and 曾琬玲. "Terahertz wave sensing applications using the evanescent field of a plastic wire waveguide." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/a36jr6.
Full textAbstract:
碩士國立成功大學
光電科學與工程學系
107
The thesis successfully demonstrates a plastic-wire terahertz (THz) waveguide is workable for sensing the minute molecules. The experimental observation first illustrates the relation between dielectric core geometry and the waveguide spectrum. The sample substrate with nano-porous structure is then revealed as the critical element of the waveguide sensing configuration. Based on the sensitivity calibration with the standard sample of DPBS (Dulbecco's Phosphate-Buffered Saline), various porous substrates are discussed for their sensing abilities while being integrated with evanescent waves of a plastic-wire waveguide. The sensitivity of substrate-integrated plastic wire sensor is also compared with the ribbon waveguides with the porous structures in the study. For the same waveguide frequency and minute amounts of sample, the sensitivity of substrate-integrated plastic wire sensor is higher than that of a ribbon waveguide sensor. Based on the optimal geometry of substrate-integrated plastic-wire sensor, molecules in particles and drops can be recognized from different waveguide properties of the sample substrate, including the spectral shift of transmittance dip (or attenuation peak), attenuation coefficient variation at 0.3 THz, and the variation of effective waveguide refractive indices or attenuation coefficients.
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Boybay, Muhammed Said. "Sensitivity Enhancement of Near Field Probes Using Negative Materials." Thesis, 2009. http://hdl.handle.net/10012/4597.
Full textAbstract:
In the last decade, design and application of negative materials have been one of the most interesting subjects in the electromagnetic research. The extraordinary properties of double negative (DNG) and single negative (SNG) materials have been studied extensively over this period. In this thesis, one of the unusual properties of negative materials, the evanescent amplification, is used to improve the sensitivity of the near field probes.
The effect of placing DNG and SNG layers between the near field probes and the targets are investigated theoretically. A sensitivity definition is introduced for evanescent probes and it is shown using quantitative measures that the sensitivity can be increased using DNG and SNG materials for a target in vacuum and for a buried target. The electromagnetic loss of the negative materials and the mismatch between the material properties of the host medium and DNG and SNG materials are studied. Using an unmatched DNG layer or SNG layer enhances the sensitivity within an evanescent spectrum range while a lossless and matched DNG layer improves the sensitivity of entire evanescent spectrum.
The idea of using negative materials is implemented over conventional near field probes by numerical experiments. Sensitivities of open-ended waveguides and open-ended coaxial lines for a specific application are studied in the presence of negative materials. In the case of precursor pitting detection on airplane bodies, the sensitivity of an open-ended waveguide probe is increased by 35 times for a λ/10 sized cubic crack. It is also shown that the negative material increases the quality of the image generated by the probe. The sensitivity improvement is also verified for an open-ended coaxial line. A 11 times improvement is achieved for a similar detection practice, with a λ/20 sized crack. The effect of coaxial line size and the dielectric material on the sensitivity enhancement are studied.
The improvement is studied theoretically and numerically for an electrically small dipole. Theoretical studies show that when a small dipole is placed within a spherical shell made of DNG materials, the antenna parameters of the dipole becomes more sensitive to the position of a target placed outside the negative material shell. The field distribution generated by a small dipole in a multilayered spherical medium is studied for this purpose. Numerical analysis of a small dipole placed next to a planar DNG layer is presented. The DNG layer increases the sensitivity of the dipole due to a λ/30 sized metallic target by 5.5 times.
To provide experimental verification, the sensitivity of an electrically small loop is studied. SNG materials with a negative permeability around 1.25 GHz are designed using modified split ring resonators (MSRR). By using the effective parameters of the designed structure, a sensitivity improvement of 10 times is achieved numerically. The improvement is verified using fabricated MSRR structures. The sensitivity of the small loop is enhanced by 9 times for a λ/12.2 sized metallic target. The sensitivity improvements are achieved within the frequency band where the MSRR structures behave as a μ-negative SNG material.
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Li, Ching-Tao, and 李京道. "Phase and amplitude measurement of the interfered evanescent field by using near-field scanning optical microscopy with phase-modulation." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/05353671477067214123.
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Hung, Shuo-fu, and 洪碩甫. "Study of Mode-Locked Fiber Lasers Based on Graphene Saturable Absorbers Employing Evanescent Field Interaction." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/25624944358751167549.
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碩士國立高雄大學
電機工程學系碩士班
102
A passively harmonic MLFL employing evanescent field interaction with mica-dispersed graphene-based saturable absorbers was produced. The performance of fundamental MLFL has 3dB bandwidth of 5.4 nm, pulse width of 523 fs, repetition rate of 16.52 MHz and pulse energy of 0.228 nJ. The 16th harmonic MLFL was achieved with pumping current of 360 mA and had a repetition rate of 247.9 MHz. The MD of mica-dispersed graphene based SAs side-polished fiber is 1.2% for 10 mm polished length and 1.5 dB insertion loss, it is like to transmission type with MD of 1.7 %. In threshold current measurement, evanescent wave can provide higher energy tolerance, in other words, evanescent wave can provide higher output power in passive mode-locking fiber laser system.
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Ke, Pu Chun. "Near-field scanning optical microscopy with laser trapping." Thesis, 2000. https://vuir.vu.edu.au/15616/.
Full textAbstract:
This thesis is concerned with a comprehensive understanding of particle-trapped near-field scanning optical microscopy. This technique is unique in that it relies on the collection of scattered evanescent waves from a sample with a laser-trapped particle. In comparison with the other forms of near-field scanning optical microscopy with a
tapered fibre or a metallic needle probe, particle-trapped near-field scanning optical microscopy offers several advantages such as no need of distance control, high signal
collection efficiency, and easy replacement of a particle probe. In consideration of the major problems of particle-trapped near-field scanning optical microscopy such as low signal strength and low transverse scanning speed due to
the use of a dielectric particle, a two-dimensional laser-trapped metallic particle is proposed as a near-field probe for imaging.