Rozprawy doktorskie na temat „Guided mode resonance grating filters”

Guided mode resonant (GMR) structures are optical devices that consist of a planar waveguide with a periodic structure either imbedded in or on the surface of the structure. The resonance anomaly in GMR structures has many applications as dielectric mirrors, tunable devices, sensors,and narrow spectral band reflection filters. A desirable response from a resonant grating filter normally includes a nearly 100% narrowband resonant spectral reflection (transmission), and a broad angular acceptance at either normal incidence or an oblique angle of incidence. This dissertation is a detailed study of the unique nature of the resonance anomaly in GMR structures with two-dimensional (2-D) periodic perturbation. Clear understanding of the resonance phenomenon is developed and novel 2-D GMR structures are proposed to significantly improve the performance of narrow spectral filters. In 2-D grating diffraction, each diffracted order inherently propagates in its distinct diffraction plane. This allows for coupled polarization dependent resonant leaky modes with one in each diffraction plane. The nature of the interaction between these non-collinear guides and its impact on spectral and angular response of GMR devices is investigated and quantified for 2-D structures with rectangular and hexagonal grids. Based on the developed understanding of the underlying phenomenon, novel GMR devices are proposed and analyzed. A novel controllable multi-line guided mode resonant (GMR) filter is proposed. The separation of spectral wavelength resonances supported by a two-dimensional GMR structure can be coarse or fine depending on the physical dimensions of the structure and not the material properties. Multiple resonances are produced by weakly guided modes individually propagating along multiple planes of diffraction. Controllable two-line and three-line narrow-band reflection filter designs with spectral separation from a few up to hundreds of nanometers are exhibited using rectangular-lattice and hexagonal-lattice grating GMR structures, respectively. Broadening of the angular response of narrow band two-dimension guided mode resonant spectral filters, while maintaining a narrow spectral response, is investigated. The angular response is broadened by coupling the diffracted orders into multiple fundamental guided resonant modes. These guided modes have the same propagation constant but propagating in different planes inherent in multiple planes of diffraction of the 2-D gratings. The propagation constants of the guided resonant modes are determined from the physical dimensions of the grating (periodicity and duty cycle) and the incident direction. A five-fold improvement in the angular tolerance is achieved using a grating with strong second Bragg diffraction in order to produce a crossed diffraction. A novel dual grating structure with a second grating located on the substrate side is proposed to further broaden the angular tolerance of the spectral filter without degrading its spectral response. This strong second Bragg backward diffraction from the substrate grating causes two successive resonant bands to merge producing a resonance with symmetric broad angular response.
Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD

Les filtres spectraux à réseaux résonants, ou GMRF (Guided-Mode Resonance Filters), sont une nouvelle génération de filtres à bande étroite et constituent une alternative très prometteuse aux filtres conventionnels multicouches Fabry-Pérot. Le pic de résonance d'un GMRF peut être très fin spectralement et de longueur d'onde de centrage accordable en fonction de l'angle d'incidence. Ces propriétés sont particulièrement importantes pour la spectroscopie. Les travaux antérieurs ont permis de mettre en œuvre une structure originale comportant deux réseaux 1D croisés. Les performances de ce filtre surpassent celles des filtres conventionnels par leur réponse spectrale subnanométrique, leur accordabilité, et leur capacité à s'affranchir de l'influence de la polarisation de l'onde incidente sous incidence oblique. Le but de ce travail est d'explorer les performances ultimes de ce type de dispositif en termes de résolution et taux de réjection, par une approche mêlant théorie, technologie et caractérisation. Nous présentons des résultats expérimentaux d'un filtre en réflexion indépendant de la polarisation, accordable sur 40 nm avec 8.3nm/° d'accordabilité, ayant une réflexion de 10-3 sur une plage de 90nm en dehors de la résonance et un facteur de qualité supérieur à 5000
Guided Mode Resonance Filters ( GMRF ) are a new generation of narrowband optical filters and are a very promising alternative to conventional multilayer Fabry-Perot filters. The resonance peak of GMRF can be spectrally extremely thin and with a centering wavelength tunable according to the angle of incidence of the light. These properties are particularly important for spectroscopy. Previous works have helped to implement an original structure with two 1D crossed gratings. The performance of this filter overpasses those of conventional filters in their spectral subnanometric response, tunability and their ability to overcome the influence of the polarization of the incident wave under oblique incidence. The aim of this work is to explore the final performances of such devices in terms of resolution and rejection rate, thanks to an approach combining theory, fabrication technology and characterization. We present experimental results of a polarization independent reflective filter, tunable over 40nm with a tunability of 8.3nm / °, having a reflection of 10-3 on a 90nm range outside the resonance and a quality factor over 5000

This dissertation develops a theoretical framework for guided mode resonance filters (GMRFs) with surface relief gratings based on a physical optics approach. A GMRF is a unique optical device that utilizes the resonance due to the coupling of a diffraction order of a grating with a waveguide mode. This coupling process leads to rapid fluctuations in the reflected and transmitted fields from the GMRF. The reflected output can change from 0% to 100% over extremely small wavelength (or angular) regions with a Lorentzian lineshape. It is shown that the surface relief gratings can be effectively modeled using effective medium theory (EMT). Combining the EMT modeled surface relief grating and thin film theory provides an approximation of the sidelobe levels around a resonance peak and can be used to design a grating that acts as an anti-reflection coating. In addition, EMT can be combined with multilayer waveguide relationships to provide an improved method for determining the wavelength of a resonance. The effect of a finite aperture grating upon the reflected and transmitted output from a GMRF is analyzed. The resonance peak width is found to be inversely proportional to the grating length and the peak efficiency of the GMRF is shown to decrease with reduced grating length. Finally, the design and analysis of a GMRF with a nonlinear waveguide is presented and shown to be capable of providing all-optical switching with low input intensities.

A wide range of applications currently utilize conventional optical elements to individually transform the phase, polarization, and spectral transmission/reflection of the incident radiation to realize the desired system level function. The material properties and the feasibility of fabrication primarily impact the device and system functionality that can be realized. With the advancement in micro/nano patterning, growth, deposition and etching technology, devices with novel and multiplexed optical functionalities have become feasible. As a result, it has become possible to engineer the device response in the near and far field by controlling the phase, polarization or spectral response at the micro scale. One of the methods that have been explored to realize unique optical functionalities is by varying the structural properties of the device as a function of spatial location at the sub-micron scale across the device aperture. Spatially varying the structural parameters of these devices is analogous to local modifications of the material properties. In this dissertation, the optical response of interference transmission filters, guided mode resonance reflection filters, and diffraction gratings operated in Littrow condition with strategically introduced spatial variation have been investigated. Spatial variations in optical interference filters were used to demonstrate wavelength tunable spatial filters. The effect was realized by integrating diffractive and continuous phase functions on the defect layer of a one-dimensional photonic crystal structure. Guided mode resonance filters are free space optical filters that provide narrow spectral reflection by combining grating and waveguide dispersion effects. Frequency dependent spatial reflection profiles were achieved by spatially varying the grating fill fraction in designed contours. Diffraction gratings with space variant fill fractions operating in Littrow condition were used to provide graded feedback profiles to improve the beam quality and spatial brightness of broad area diode lasers. The fabrication of space variant structures is challenging and has been accomplished primarily by techniques such as ruling, electron beam writing or complex deposition methods. In order to vary the desired structural parameter in a designed manner, a novel technique for the fabrication of space variant structures using projection lithography with a fidelity that rivals any of the current technologies was also developed as a part of this work. The devices exhibit wavelength dependent beam shaping properties in addition to spatial and spectral filtering and have potential applications in advanced imaging systems, graded reflectivity laser mirrors, and engineered illumination. The design, modeling, microfabrication and experimental characterization of space variant micro optical elements with novel optical functionalities are presented.
Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD

L'analyse spectrale d'une scène infrarouge permet une meilleure identification des objets la composant. Il est possible d'obtenir du filtrage spectral grâce à des résonances optiques au sein de nanostructures. Cette thèse traite de l'utilisation de structures à réseau sub-longueur d'onde pour obtenir des filtres spectraux à l'échelle d'un pixel de détection. Je me suis concentré sur l'étude de filtres à résonance de mode guidé, constitué d'un réseau de couplage associé à une couche mince diélectrique, qui nécessite typiquement de grandes surfaces pour fonctionner. J'ai mené une étude numérique du comportement spectral et angulaire de ces structures et j'ai envisagé deux possibilités pour obtenir un filtrage sur de petites dimensions: l'utilisation d'une cavité résonante dans le guide d'onde à l'aide de miroirs latéraux et l'utilisation de réseaux métalliques.L'analyse numérique de la réponse optique des structures à réseau métallique montre qu'il est possible d'obtenir une extension spatiale limitée du champ électromagnétique dans le guide d'onde à la résonance. Grâce à cette faible extension, j'ai pu étudier numériquement des filtres à résonance de mode guidé foisonnants sur des longueurs aussi faibles que 30 µm. J'ai aussi pu établir un processus de fabrication en salle blanche puis caractériser des filtres de la taille d'un pixel de détection infrarouge.Finalement, j'ai étudié la possibilité de fabriquer des mosaïques de filtres à résonance de mode guidé pour le filtrage spectral à proximité d'un détecteur plan focal. J'ai pu démontrer que les dimensions, les transmissions résonantes et les tolérances angulaires de ces filtres les rendent compatibles avec une telle utilisation. J'ai alors pu montrer un exemple d'architecture simple de caméra multi-spectrale infrarouge mettant en jeu une mosaïque de filtres à résonance de mode guidé
Spectral analysis of an infrared scene allows for a better identification of its components. Nanotechnologies offer new opportunities to achieve spectral filtering thanks to optical resonances. In this thesis, I use sub-wavelength gratings to achieve spectral filtering on areas as small as a pixel. I focused on the study of guided-mode resonance filters, made of a coupling grating and a thin dielectric layer acting as a waveguide. This structure typically needs large surfaces to filter infrared light. However, I proposed two possible modifications of this structure: either using a resonant cavity or using metallic gratings.Numerical analysis of the optical response of structures with a metallic grating showed that the spatial extension of the electromagnetic field is limited at the resonant wavelength. Thanks to this short extension, I is possible to achieve filtering with only 30 µm-long guided-mode resonance filters. I also fabricated and characterized those pixel-sized filters.Finally, I studied mosaics of small guided-mode resonance filters. I showed that the dimensions, the resonant transmissions and the angular acceptance of those mosaics are compatible with using them inside multi-spectral cameras. I also showed a sample architecture for an infrared multispectral-camera using a mosaics of guided-mode resonance filters

Waveguide gratings are widely being used for multitude of applications owing to high sensitivity, immunity to electromagnetic interference, multiplexing capabilities, light weight and compactness. Waveguide gratings on Silicon-on-Insulator (SOI) platform have been attracting interest for optical communication and sensing applications. SOI platform has several advantages over other materials like Lithium Niobate, Polycarbonate, Silicon Nitride etc. High index contrast of SOI leads to miniaturization of the chip. But to design ultra low cost devices, SOI is not the suitable platform. Plastic or polycarbonate might be a possible alternative to silicon for low cost or disposable sensors. In this thesis, we have designed and analysed various structures of waveguide gratings on the basis of their suitability for communication and sensing applications. Mathematical models have been developed for various structures and analysed using simulations. Waveguide diffraction grating has been used as a grating coupler for fiber to integrated optic (IO) coupling. Fabrication and characterization of waveguide grating is also carried out. Waveguide Bragg gratings are useful in optical MEMS sensor applications. Here waveguide Bragg grating (WBG) based pressure and acceleration sensors are studied. Diaphragm and cantilever beam, mechanical structures have been used for pressure and acceleration measurements respectively. These mechanical structures are designed to enhance the sensitivity of sensors. Opto-mechanical coupling is analyzed through photo-elastic effect. A new design of surface relief waveguide Bragg grating configuration called superstructure WBG is proposed to eliminate the cross-sensitivity of the sensor due to external factors like temperature. A theoretical analysis has been provided for the superstructure WBG configuration. The sensitivity measurement for pressure and acceleration is found to be 0.21 pm/Pa and 6.49 nm/g respectively. The superstructure configuration is also used for multiparametric sensor designs. Multiple parameters like pressure and acceleration have been measured simultaneously using monolithic, multiparametric sensor using superstructure WBG. Finally a novel differential pressure sensor is proposed using surface relief WBGs embedded in a Mach Zehnder interferometer (MZI) and theoretically designed and analysed. The differential pressure sensor sensitivity of 0.2 pm/Pa has been achieved. Guided mode resonance grating filters are used for biosensing applications. The change in effective refractive index leads to two types of biosensing namely, the homogeneous sensing and surface sensing. In homogeneous sensing, the effective refractive index of a propagating optical mode changes with uniformly distributed sample extending over a distance well exceeding the evanescent field penetration depth. Here the sample serves as the waveguide cover. Where as in surface sensing, the sample adsorbs onto the surface of the waveguide and in this case, the effective refractive index of an optical mode changes with the refractive index as well as the thickness of a sample. Both sensing schemes have been analysed to detect concentration of sugar, the analyte in honey being the sample. The sensitivity of 142 nm/RIU and 23 nm/RIU for homogeneous and surface sensing respectively are found. WBG is also useful in filtering applications. We have designed WBG with periodic perturbation to get multiple wavelengths filter response.

碩士
國立中正大學
化學暨生物化學研究所
103
Many diseases will release specific biomolecules before outbreak of the diseases. Particle plasmon resonance (PPR) occurs when a noble metal nanoparticle absorbs a specific wavelength of energy which is equal to the oscillation frequency of the conductive electrons. The principle of sensing here is based on the coupling of incident light into the guided-mode resonance sensing chip through a grating at a specific angle and wavelength. When the leakage mode and diffraction grating matching condition is reached, the electric field distribution on the grating surface will enhance the particle plasmon resonance effect of the gold nanoparticles. When the particle’s surrounding refractive index changes, the particle plasmon resonance band will shift, resulting in optical signal change. In this study, we successfully modified gold nanoparticles (GNP) and gold nanorods (GNR) on grating. The GNP-GMR-PPR sensor has achieved an absorbance sensitivity of 2.21 RIU-1 at an excitation wavelength of 532 nm and a sensor resolution of 1.82×10-5 RIU. The limit of detection for anti-DNP antibody is 1.18×10-10 M. The GNR-GMR-PPR sensor has achieved an absorbance sensitivity of 26.61 RIU-1 at an excitation wavelength of 885 nm and a sensor resolution 4.16×10-6 RIU.

碩士
國立中山大學
光電工程學系研究所
104
In this study, we employ two-dimensional (2-D) grating structures and the guided mode resonance effect to design dual-parameter sensors. The incident light is diffracted by the 2-D grating to induce both the transverse electric (TE) guided mode and transverse magnetic (TM) guided mode of the waveguide. Due to the grating structures, the guided waveguide modes will leak out from the waveguide. As they fulfill the phase matching condition, we can observe resonance peaks in the spectrum. The resonance wavelengths can be affected by the external environment parameters. As a result, we can achieve dual-parameter sensing by measuring the TE/TM resonance wavelengths. The numerical tool we utilized is Comsol Multiphysics. For the reflection type dual-parameter sensor, the sensing sensitivities to temperature and environment refractive index are -13.8pm/°C (TE waveguide mode), -24pm/°C (TM waveguide mode), 37nm/RIU (TE waveguide mode), and 186nm/RIU (TM waveguide mode). Meanwhile, the calculated sensing sensitivities of transmission type dual-parameter sensor to temperature and environment refractive index are -20pm/°C (TE waveguide mode), -40pm/°C (TM waveguide mode), 27nm/RIU (TE waveguide mode), and 54nm/RIU (TM waveguide mode). We have also designed reflection type dual-parameter sensor for thin-film sensing. The sensing sensitivities to thin film thickness and index are 0.18 nm/nm (TE waveguide mode), 0.2 nm/nm (TM waveguide mode), 252.849nm/RIU (TE waveguide mode), and 190.5 nm/RIU (TM waveguide mode). Moreover, our proposed dual-parameter sensors can be used without cross-sensitivities to increase their sensing applications.

碩士
國立中央大學
光電科學研究所
95
In this thesis, we show that ultranarrow-band guided-mode resonance (GMR) filters with flattened sidebands can be implemented with weakly modulated subwavelength gratings and low/high/low quarter-half-quarter dielectric thin-film stacks. These band-stop (notch) filters with characteristics of high efficiency, extended low-sideband reflection, and symmetric line shapes are designed by embedding waveguide gratings in layered structures possessing the feature of antireflection. The resonant wavelength of proposed GMR filters is precisely controlled at 1550 nm for optical communication. Furthermore, the improved spectral performance at sideband including the intensity of zero-order diffraction efficiency greater than 0.9 and the spectral range of sideband greater than 400 nm, the improved contrast between resonance peak and sideband, as well as the modulate ultra-narrow linewidth for resonance peak are demonstrated theoretically. The thickness of SiNx waveguide and its corresponding grating period are designed by using the waveguide theory and the phase-matching condition. The sideband performance can be improved by means of the effective medium theory. The effects of the grating filling factor and the grating depth on weakly-modulated GMRs are studied. The fabrication feasibility of proposed structures is considered during our design. Two GMR filters, containing the case of the transverse electric (TE) and the transverse magnetic (TM) polarization, are designed to demonstrate the concept. Under the requirement of transmission efficiency at sideband greater than 93%, resonance wavelength of 1550 nm, and its linewidth Δλ less than 0.8 nm, and sideband can extended more than 660 nm. Finally the sideband spectral response of proposed structures is compared by using the rigorous coupled wave analysis (RCWA) and the effective medium theory (EMT). The fabrication tolerance regarding grating depth, resonant peak location, and linewidth are discussed. Furthermore, the performances of ultranarrow-band guided-mode resonance filters are also studying by using band diagrams.

碩士
國立中央大學
光電科學研究所
96
In this letter, the two-layer ultranarrow bandstop guided-mode resonance filter with a flattened sideband within a wide spectral range is implemented by using the combination of a subwavelength grating, a waveguide layer with multiple guided modes, and a lower cladding layer with a quarter-wave thickness. The proposed filter based on a free-standing silicon nitride membrane suspended on a silicon substrate is realized by using the anisotropic wet etching to remove the substrate beneath the silicon nitride layer. Both of grating and waveguide structures are fabricated simultaneously on a silicon nitride membrane. Moreover, the silicon dioxide membrane playing a role on modifying the spectral response of proposed GMR filter is deposited beneath the free-standing silicon nitride layer. The incident light is TE mode and the thickness of grating is 30nm. The resonance wavelength of proposed band-stop filter is controlled at 1550.4nm with a linewidth (FWHM) less than 0.1 nm. The improved spectral performance including the sideband can be extended to be nm with the maximum transmittance greater than 93%. The quality factor is 15504. However, the incident light is TM mode and the thickness of grating is 30nm. The resonance wavelength of proposed band-stop filter is controlled at 1549.9nm with a linewidth (FWHM) less than 0.011 nm. The improved spectral performance including the sideband can be extended to be nm with the maximum transmittance greater than 93%. The quality factor is 140902.

碩士
國立中正大學
化學暨生物化學研究所
102
In this study, guided mode resonance (GMR) biosensing platform combining the features of gold nanoparticles with grating waveguide is developed. This approach has an advantage as compared to the traditional guided mode resonance approach in biosensing, namely, the sensing depth of particle plasmon resonance generated on the gold nanoparticle surface is just tens of nanometers. This feature is useful for measuring biochemical binding on nanoparticle surface. Besides, the use of gold nanoparticles in biosensing also have two other features: label-free and real-time. It also allows using mixed self-assembled monolayer on gold nanoparticle surface to reduce nonspecific adsorption problem. The waveguide was fabricated by sputtering TiO2 (60nm) on the imprinted grating. The sensor has a wavelength shift sensitivity of 120.54 nm/RIU. When gold nanoparticles was used to modify the grating surface, an absorbance sensitivity of 7.73 AU/RIU at an excitation wavelength of 532 nm is achieved. Finally, the gold nanoparticle surface is modified by a mixed self-assembled monolayer and further conjugated with anti-OVA for detection of ovalbumin. The limit of detection (LOD) is 1.2x10-8 M.

碩士
國立中正大學
光機電整合工程研究所
99
In this thesis, we produced the azo-copolymer planar waveguide with surface relief grating (SRG) by two beam interference technique. Our samples were measured with guided mode resonance (GMR) transmission spectra that demonstrated full-half width-maximum (FHWM) about 3nm and the transmission efficiency indicated the attenuation down to 43%. In our experiment, Argon laser (514nm) exposure to the sample in order to change the refractive index of grating layer and guiding layer that controlled the GMR peak wavelength. The maximum shift of resonance wavelength was up to 26.4nm. After turning off the pumping laser, we observed the GMR peak wavelength can’t back to the original position for a long time. We decreased the GMR peak wavelength recovery time and rewrite the GMR successfully. In addition, the numerical simulation of GMR transmission spectra verified the experimental results. Simulation was used with Rigorous Coupled Wave Analysis (RCWA) method, the trend of simulation results approached with the experimental results very well.

碩士
國立中正大學
物理系研究所
104
The enhanced upconversion luminescence of lanthanide-ion(Ln3+) doped upconversion nanoparticles (UCNPs) is particularly important and highly required for their innumerable applications in fluorescence microscope, bio-imaging, sensing, solid-state lasers, 3D displays, and solar cells.In this study, we investigate the enhancement effect of upconversion fluorescence emission of UNCP by using low refractive index resonant waveguide grating(RWG) when both excitation and extraction resonance occur in the waveguide structure.The method to fabricate one-dimensional grating patterns with nanoporous SiO2, a low refractive index material (n=1.22), using nanoimprint lithography is reported. A guided mode resonant structure is obtained by subsequent sputtering of thin film of high refractive index titanium dioxide (TiO2) on the sample surface, and then NaYF4:Yb3+,Tm3+ nanoparticles are deposited onto the top cladding layer of a RWG structure by dip-coating method.We demonstrate the up-conversion photoluminescence signal generated from the rare-earth nanocrystal coated on top of such RWG structure can be enhanced up to 10^4 times when both excitation and extraction resonance are simultaneously achieved, compared with UCNPs on an non-patterned surface. Keywords : Low-refractive index , Up conversion, Rare earth, Fluorescence, Guided-mode resonance