Dissertations / Theses on the topic 'VISIBLE PHOTONIC'
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1
González, Xavier (Xavier R. González Barrios). "Edible photonic crystals tunable within the visible regime." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/112496.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 50-52).
An experimental study was performed to design and fabricate an edible photonic crystal made of alternating layers of food grade titanium dioxide and agar that is able to selectively reflect wavelengths of light within the visible spectrum and allow for dynamic color changes through the tuning mechanism of swelling its agar layers with the addition of edible solvents. After doing a literature search to discover which materials were available to create this edible photonic structure, a trial and error process was conducted using deposition and film thickness characterization techniques to optimize the physical and optical characteristics of the layers composing the photonic structure. The materials selected for the layers in the structure yield a high refractive index contrast, which allows for high reflectivity with a reduced amount of total layers. The multilayer stack can be designed to reflect particular wavelengths by selecting the thickness of the layers accordingly. Thin film characterization took place through the use of profilometry, ellipsometry, and atomic force microscopy. The feasibility and practicality of two manufacturing techniques, spin-coating and RF-sputtering, were analyzed in the process of learning how to assemble an edible multilayer stack for molecular gastronomy applications.
by Xavier González/
S.B.
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CALAFIORE, GIUSEPPE. "Nanoimprinting of Photonic Devices for Visible Light Applications." Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2640840.
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The science of photonics is increasingly enabling the discovery of unprecedented proprieties that stem from the interaction of light with nanostructured matter. On the other hand, nanotechnology provides a key support to the research in photonics. In particular nanoimprint lithography (NIL) proved important to accelerate the development and prototyping of novel photonic device concepts. In this thesis, NIL was analyzed as a suitable, flexible, low-cost lithography solution for photonics. The purpose of this work is to research and evaluate novel nanofabrication technologies, materials and device concepts to support and innovate the fields of photonics and nanotechnology. In doing so, different implementations of NIL were experimentally investigated on the imprint of novel photonic devices into purely organic and hybrid organic-inorganic sol-gel materials.
Two main research themes on printable photonics are explored in parallel. The first concerns the development and testing of nanoimprint technologies to pursue the fabrication of progressively more challenging device concepts, from 2D to 3D. As a second research theme, the idea to couple top-down nano-patterning approaches (NIL) with bottom-up functionalities that emerge from engineering material proprieties at the chemistry level is put forward. To explore these research courses, two photonic devices were designed, fabricated and tested: an integrated holographic planar circuit for on-chip spectroscopy, and a photonic crystal slab printed out of a functional, high-refractive index material. The amount of integration, complexity and variety of the printed optical components presented here allow us to extend the validity of the work to an even broader range of photonic devices. This work advances the field of printable photonics and demonstrates its leverage to innovation, which encompasses several scientific fields.
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MAKHLOGA, ASHISH, and VIDESH KUMAR. "Sm3+ IONS DOPED BOROSILICATE GLASS FOR VISIBLE PHOTONIC DEVICE APPLICATIONS." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18625.
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An intense reddish-orange colour radiating Samarium doped Aluminium Calcium
borosilicate (BSACS) glasses were synthesized with the help of the melt-quench method to
analyze the photoluminescence properties using characterization methods like XRD, FT-IR,
photoluminescence (PL) excitation, PL emission, and PL decay. XRD and FT-IR reveal the
non-crystalline behavior along with the presence of numerous functional groups in BSACS
host glass correspondingly. Under 402 nm excitation, three major peaks were found in the
emission spectra which perfectly resembles to 4G5/2 → 6H5/2 (562 nm), 4G5/2 → 6H7/2 (599
nm), and 4G5/2 → 6H9/2 (646 nm) transitions of Samarium ions. 4G5/2 → 6H9/2 transition at 599
nm is comparatively more intense and noticeable. PL decay observed for 4G5/2 state reveals
the exponential nature in which curves are fitted by using bi-exponential and tri- exponential
fitting to assess the practically measured lifetimes (τexp). It is observed that the τexp values are
decreasing with increasing Samarium ion concentration due to the cross-relaxation energy
transference. All of the findings indicate that Sm3+ doped borosilicate glass is suitable for its
usage in visible reddish orange photonic devices.
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Haigh, Paul. "Using equalizers to increase data rates in organic photonic devices for visible light communications systems." Thesis, Northumbria University, 2014. http://nrl.northumbria.ac.uk/21415/.
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This thesis proposes to marry two separate technologies together. The first technology is that of visible light communications (VLC), and the second is small molecule and polymer organic photonic devices. These two technologies both offer outstanding potential in their respective fields of information communications and optoelectronics, with both being proposed as two of the most important technologies about to emerge in the next decades by their respective research communities. As such, it is imperative to investigate and analyse the performance of organic photonic devices in the context of VLC broadcasting networks. There have been no experimental results in the literature reporting on organic-VLC systems until the work proposed in this thesis and therefore the focus is on improving transmission speeds.
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Pierre, Thomas. "Mesure de la température à l'échelle microscopique par voie optique dans la gamme ultraviolet-visible." Thesis, Vandoeuvre-les-Nancy, INPL, 2007. http://www.theses.fr/2007INPL096N/document.
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Cette étude porte sur la mesure de la température à l’échelle microscopique par voie optique dans la gamme UV-visible par comptage de photons à l’aide d’un PMT refroidi. À partir des avantages et des inconvénients de chaque technique existante, la première partie permet de comprendre les orientations de nos travaux. Le Second Chapitre montre et insiste sur l’intérêt de travailler aux courtes longueurs d’onde (limite de diffraction, précision sur la mesure...), d’utiliser la méthode multi-spectrale pour s’affranchir de paramètres inconnus (e.g. l’émissivité) en choisissant judicieusement les longueurs d’onde de travail, ainsi que les lois statistiques classiques pour mesurer le flux photonique sachant son émission aléatoire. Le Chapitre Trois présente le banc de mesure (microscope optique, système de mesure du flux photonique...) et une attention toute particulière est portée sur la conception des éléments chauffants servant à l’étalonnage. Le Quatrième Chapitre présente les résultats en températures obtenues à l’aide des lois statistiques. Ils valident le bon fonctionnement du dispositif, la mise au point de la zone microscopique, et l’intérêt de bien modéliser les filtres monochromatiques. Enfin, des améliorations sur la précision de la mesure (réseau de diffraction, analyseur multi-canal) et pour mesurer des températures plus faibles (LIF, méthode corrélation temporelle) sont présentées dans le Cinquième ChapitreThe aim of this study is to measure microscale temperature by optical way in the UV-visible range by photons counting using a cooled PMT. From the existing techniques advantages and disadvantages, this first part allows to understand the choices of this study. The second part shows and underlines the interest in working in short wavelengths (diffraction limit, measurement accuracy), in using the multi-spectral method to get rid of unknown parameters (e.g. emissivity) by choosing judicious working wavelengths, as well as the statistic laws to measure the photonic flux knowing its random emission. The third chapter presents the optical bench (optical microscope, photonic flux measurement facility…). A particularly attention is given to the design of the heated elements, which allow to calibrate the facility. The fourth part exposes the temperature results obtained through statistic laws. They validate the well-running of the facility, the microscopic area focusing, and the interest to model correctly the filters. Finally, measurement accuracy improvements (diffraction grating, multi-channel analyzer) and lower temperature measurement techniques (LIF, time-correlated method) are presented in the fifth part
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Gach, Jean-Luc. "Imageurs à amplification." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0317.
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La quête du détecteur parfait, sans bruit, capable de détecter des photons uniques dans le visible et l’infrarouge, et ultimement de déterminer leur énergie est le graal de la détection. Pour arriver à ce but, de nombreux scientifiques ont développé des dispositifs depuis plusieurs dizaines d’années, et les astronomes ont toujours été à la pointe en ce domaine. En ce sens les imageurs à amplification semblent être la voie la plus rapide et la plus prometteuse pour atteindre ce but ultime. Ainsi après un bref historique de l’état de l’art sont exposés les systèmes à comptage de photons (IPCS) développés au LAM, qui ont été utilisés sur les télescopes ESO 3m60, OHP 1m93 ou encore WHT 4m20. Sont ensuite abordés les dispositifs imageurs intégrés à amplification comme les EMCCD (Electron multiplying charge coupled devices) dans le visible, avec quelques exemples de leur utilisation en astronomie. C’est la technologie qui, appliquée aux senseurs de front d’onde, aura permis conjointement à d’autres développements l’avènement des optiques adaptatives extrêmes comme celle de l’instrument VLT-SPHERE ou encore de SUBARU-SCExAO. Pour finir les e-APD (electron initiated avalanche photodiode) dans l’infrarouge seront abordés. Les e-APD ont cette propriété très intéressante d’être des amplificateurs quasi parfaits, et ont une capacité à détecter l’énergie des photons, des propriétés qui seront développées et analysées. Nous finirons par les perspectives et les progrès que nous sommes en droit d’attendre dans les prochaines annéesThe quest for the perfect, noiseless detector, capable of detecting unique photons in the visible and infrared, and ultimately determining their energy is the grail of detection. To achieve this goal, many scientists have developed devices for several decades, and astronomers have always been at the forefront in this area. In this sense amplification imagers seem to be the fastest and most promising way to achieve this ultimate goal. Thus, after a brief history of the state of the art are exposed the photon counting systems (IPCS) developed at LAM, which were used on ESO telescopes 3m60, OHP 1m93 or WHT 4m20. Imaging integrated imaging devices such as Electron Multiplying Charge Coupled Devices (EMCCDs) are then discussed in the visible, with some examples of their use in astronomy. It is the technology that, applied to the wavefront sensors, has jointly enabled other developments the advent of extreme adaptive optics such as the VLT-SPHERE or SUBARU-SCExAO. To finish the e-APD (electron-induced avalanche photodiode) in the infrared will be discussed. E-APDs have this very interesting property of being almost perfect amplifiers, and have an ability to detect photon energy, properties that will be developed and analyzed. We will end up with the prospects and the progress that we are entitled to expect in the coming years
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West, Gavin N. (Gavin Neal). "Visible and ultraviolet integrated photonics for addressing atomic systems." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122915.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 117-129).
In the wake of many technological successes in integrated photonics based on silicon, attention has been given to applications in the visible light regime. This thesis is concerned with furthering the development of integrated photonics for controlling atomic systems, in particular individual trapped atomic ions. Nature places strict constraints on the frequency of the lasers used to address these atoms, typically spanning from the ultraviolet into the near infrared, and on the sensitivity to accidental perturbations from the control hardware. A platform for broadband integrated photonics, using amorphous aluminum oxide as the patterned material, is developed and exhibits suitable performance in the visible and ultraviolet. The waveguide loss and resonator quality factors are the best which have been reported to date, for wavelengths shorter than 500 nm. Next, a theory is developed which proposes laser frequency noise as a limiting factor for the extinction ratio of common integrated modulator designs. Understanding of this limit, and possible methods to suppress its effects, is important due to the fragile nature of single-photon-sensitive quantum systems. Finally, the application of technology developed here is applied to the analysis of trapped-ion-based optical atomic clocks. Justification for such integration of clocks and the impacts that result -- both good and bad -- are discussed from the perspective of a hardware designer.
by Gavin N. West.
S.M.
S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Choy, Jennifer Tze-Heng. "Nanophotonic Structures for Coupling to Quantum Emitters in the Visible." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10990.
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This thesis is about the design, fabrication, and characterization of nanophotonic elements in the visible that can enhance light-matter interaction for single quantum emitters. We focus on two material systems: single photon sources based on the nitrogen-vacancy (NV) center in diamond with improved spontaneous emission rates and collection efficiencies, and passive TiO2 devices that comprise a potentially broadband (from the visible to the infrared), low loss photonics platform and that are suitable for probing and manipulating single colloidal quantum dots. We first discuss the requirements for using color center emission in bulk diamond crystals for potential applications in quantum information processing, and provide examples of using nanowire structures and planar resonators made in diamond for engineering the the NV center’s pump and collection efficiencies, and spontaneous emission rates, respectively. We also describe the integration of diamond with plasmonic structures. We have designed and implemented diamond-silver apertures for broadband enhancements of the spontaneous emission rates of NV centers. We show that shallow-implanted NV centers in diamond nanoposts provide a good system for controlling the NV center spontaneous emission rates, allowing for quenched emission with long lifetimes in the bare case, and enhanced emission with fast decay rates (corresponding to a Purcell factor of around 6) when coated with silver. We add plasmonic gratings around the diamond-silver apertures to improve the collection efficiency of the system, and observe over two-fold improvement in collection. We demonstrate the fabrication of chip-scale linear optical elements such as waveguides and racetrack resonators in low-loss \(TiO_2\) thin films. The fabricated waveguides operate over a wide bandwidth with propagation losses from from 30 dB/cm in the visible to 4 dB/cm in the IR, while racetrack resonators can critically couple to waveg- uides and have quality factors as high as ~22000 in the red wavelengths. We present the fabrication of dielectric slot waveguides and their integration with colloidal quan- tum dots. Finally, we describe efforts to study and control charge transfer processes between quantum dots and \(TiO_2\) on a single emitter level.Engineering and Applied Sciences
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Alsolami, Ibrahim. "Visible light communications with single-photon avalanche diodes." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:744eeb47-8bb6-4776-8b8f-f7b6374d89bd.
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This thesis explores the use of single-photon avalanche diodes (SPADs) for visible light communications (VLC). The high sensitivity of SPADs can potentially enhance the performance of VLC receivers. However, a SPAD-based system has challenges that need to be addressed before it can be considered as a viable option for VLC. The first challenge is the susceptibility of SPAD-based receivers to variations in ambient light. The high sensitivity of SPADs is advantageous for signal detection, but also makes SPADs vulnerable to variations in ambient light. In this thesis, the performance of a SPAD-based receiver is investigated under changing lighting conditions. Analytical expressions to quantify performance are derived, and an experiment is conducted to gain further understanding of system performance. It is shown that a SPAD-based receiver is highly sensitive to illumination changes when on-off keying (OOK) is employed, and that pulse-position modulation (PPM) is a preferred modulation scheme as it is more robust. The second challenge is broadcasting to SPAD-based receivers with different capabilities. A traditional broadcasting scheme is time-sharing, whereby a transmitter sends data to receivers in an alternating manner. Broadcasting to SPAD-based receivers is challenging as receivers may have diverse capabilities. In this thesis, a new multiresolution modulation scheme is proposed, which can potentially improve system performance over the traditional timesharing approach. The performance of the proposed scheme is analyzed, and a proof-of-concept experiment is performed to demonstrate its viability.
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Bellocchi, Gabriele. "Visible light emission from Eu-containing Si-based materials." Doctoral thesis, Università di Catania, 2014. http://hdl.handle.net/10761/1519.
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Among the various rare earth ions, a particular attention is currently devoted to Eu, because of its peculiar chemical and optical properties. Indeed Eu is stable both in its trivalent and divalent oxidation state; Eu2+ ions are characterized by a very intense and broad emission band, tunable in all the visible range, which can be of interest for many technological fields, while Eu3+ ions present less intense and sharp emission peaks at arround 600 nm. In this thesis, two different approaches able to take advantage of the properties of Eu ions have been presented: i) the doping approach, which fully exploits the many advantages offered by a Si oxycarbide (SiOC) host matrix, and ii) the compound approach, which mainly focuses on Eu silicates.
By centering the attention on host matrices compatible with Si technology, Eu-doped SiO2 is a widely studied system, but its perspectives are quite poor, since the low Eu solid solubility in SiO2 strongly limits the concentration of optically active Eu ions. On the other hand, it has been demonstrated in this thesis that a SiOC matrix is able to enhance the solubility of Eu ions by two orders of magnitude with respect to SiO2, and simultaneously acts as an efficient reducing ambient for Eu ions, which are indeed stabilized in their divalent oxidation state. As a result, Eu-doped SiOC shows a very strong room temperature PL emission in the visible range, which is more than two orders of magnitude more intense than that one of Eu-doped SiO2. Furthermore, the occurrence of an energy transfer mechanism between the SiOC matrix and Eu2+ ions increases the efficiency of photon absorption for excitation wavelengths shorter than 300 nm.
Due to this properties Eu-doped SiOC offers great potentialities for the fabrication of light sources. In this thesis a continuous redshift of the emission peak from 400 to 600 nm by increasing the Eu concentration has been reported, allowing to consider this material a tunable light source. Furthermore, Eu2+ properties have been also used to realize a white light source, through the synthesis of a bilayer consisting of two SiOC films doped with different Eu concentrations. Through a proper choice of the annealing temperature, and taking advantage of the dependence of the PL peak position on the Eu concentration, an intense white emission at room temperature has been obtained. The CIE chromaticity coordinates of the emission are (0.33, 0.36), to be compared with those relative to an ideal white emission which are (0.33, 0.33), and the calculated color rendering index is 91/100.
The second approach discussed in this thesis is based on the synthesis of Eu compounds by thermal processing of Eu2O3 thin films deposited by RF magnetron sputtering on Si substrates. It has been shown that annealing processes in N2 ambient lead to a complex reactivity at the Eu2O3/Si interface, which induces from Eu3+ to Eu2+ reduction and formation of stable Eu2+ silicates (Eu2SiO4 and EuSiO3). These materials show a very strong and broad room temperature emission peaked at 590 nm, with a very high external quantum efficiency arround 10%. This result is very impressive, especially if we consider previously reported data for Eu silicates grown with different methods, in which an external quantum efficiency of 0.1\% has been observed.
The results shown in this thesis demonstrate that Eu-doped SiOC and Eu silicates have the potentialities for becoming the building blocks of future devices for lighting and photonics. The development of suitable strategies for obtaining an electrical excitation in both kind of materials, coupled with a full comprehension of the dependence of their optical properties and structural features on growth conditions and post-growth processing will be able to drive a complete transition of these materials from research laboratories to devices for every-day life.
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Li, Yichen. "Enhancing communication link performance in visible light communication." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/25666.
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With data throughput increasing exponentially in wireless communication networks, the limited radio frequency (RF) spectrum is unable to meet the future data rate demand. As a promising complementary approach, optical wireless communication (OWC) has gained significant attention since its licence-free light spectrum provides a considerable amount of communication bandwidth. In conventional OWC systems, the information-carried signal has to be real-valued and non-negative due to the incoherent light output of the conventional optical transmitter, light emitting diode (LED). Therefore, an intensity modulation and direct detection (IM/DD) system is used for establishing the OWC link. Some modified orthogonal frequency division multiplexing (OFDM) schemes have been proposed to achieve suitable optical signals. In previous research, three OFDM-based schemes have been presented, including DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM), asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) and unipolar orthogonal frequency division multiplexing (U-OFDM). Basic concepts of SPAD receivers are studied and a novel application in OWC is proposed for a permanent downhole monitoring (PDM) system in the gas and oil industry. In this thesis, a complete model of the SPAD-based OWC system is presented, including some related SPAD metrics, the photon counting process in SPAD and a specific nonlinear distortion caused by passive quenching (PQ) and active quenching (AQ) recharged circuits. Moreover, a practical SPAD-based visible light communication (VLC) system and its theoretical analysis are presented in a long-distance gas pipe with a battery-powered LED and a basic on-off keying (OOK) modulation scheme. In this thesis, two novel optical orthogonal frequency division multiplexing (O-OFDM) technologies are proposed: non-DC-biased orthogonal frequency division multiplexing (NDCOFDM) and OFDM with single-photon avalanche diode (SPAD). The former is designed for optical multiple-input multiple-output (O-MIMO) systems based on the optical spatial modulation (OSM) technique. In NDC-OFDM, signs of modulated O-OFDM symbols and absolute values of the symbols are separately transmitted by different information carrying units. This scheme can eliminate clipping distortion in DCO-OFDM and achieve high power efficiency. Furthermore, as the indices of transmitters carry extra information bits, NDC-OFDM gives a significant improvement in spectral efficiency over ACO-OFDM and U-OFDM. In this thesis, SPAD-based OFDM systems with DCO-OFDM and ACO-OFDM are presented and analysed by considering the nonlinear distortion effect of PQ SPAD and AQ SPAD. A comprehensive digital signal processing of SPAD-based OFDM is shown and theoretical functions of the photon counting distribution in PQ SPAD and AQ SPAD are given. Moreover, based on Bussgang theorem, a conventional method for analysing memoryless distortion, close-formed bit-error rate (BER) expressions of SPAD-based OFDM are derived. Furthermore, SPAD-based OFDM is compared with conventional photo-diode (PD) based OFDM systems, and a gain of 40 dB in power efficiency is observed.
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Zhang, Yun. "Fabrication and characterization of GaN visible-blind ultraviolet avalanche photodiodes." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29604.
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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Shen, Shyh-Chiang; Committee Member: Doolittle, William A.; Committee Member: Dupuis, Russell Dean. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Bruckner, Jean-Baptiste. "Réseaux de diffraction et métamatériaux photoniques pour le contrôle de la lumière dans le visible et l’infrarouge." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4319.
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Grâce aux récents progrès dans le domaine de la nanofabrication, la réalisation de structures photoniques a été rendue possible, permettant le contrôle de rayonnements lumineux utiles en tant que vecteurs d'informations ou pour la collecte de l'énergie. Ce manuscrit de thèse rassemble les études menées en collaboration avec Thalès Optronique sur deux démonstrateurs du projet ANR NPOEM, dont l'objectif est de réaliser des structures photoniques sur substrats souples par nanoimpression. Le premier démonstrateur consiste en un antireflet utilisant le domaine de résonance de réseaux de diffraction bipériodiques composés de motifs pyramidaux. Des réseaux de structures coniques à méplat lisse, structuré ou rugueux ont été modélisés par FDTD et RCWA, réalisées en collaboration avec le LTM et le CEA Liten, puis caractérisés à l'IM2NP. Les performances antireflets obtenues sont remarquables (réflectivité inférieure à 2% en incidence normale) et s'étendent sur une très large gamme spectrale du visible à l'infrarouge. Le second démonstrateur présente une fonction de filtrage de type passe-bas dans le visible et l'infrarouge. Une étude de plusieurs structures résonnantes de type métamatériaux (croix métalliques, empilement métal-diélectrique-métal, cônes métalliques et plaque métallique perforée) a montré les phénomènes de propagation singuliers liées aux petites dimensions (modes de bord, ondes de surface et couplages de proximité) et a conduit à la réalisation finale d'un filtre flexible et de large surface présentant les propriétés souhaitées. Les composants photoniques réalisés dans cette thèse trouvent leurs applications dans les domaines de la furtivité et du solaire thermiqueThanks to recent advances in nanofabrication, the realization of photonic structures was possible, allowing the control of light as an information vector or for energy harvesting. This PhD thesis adresses the studies carried out in collaboration with Thales Optronics on two demonstrators for the ANR NPOEM research project, whose objective is to fabricate photonic structures on flexible substrates by nanoimprint technology. The first demonstrator consists of an antireflective coating using resonance phenomena within biperiodic diffraction gratings. Conical structures with flat, rough or patterned tops were modeled by FDTD and RCWA, carried out in collaboration with the CEA Liten LTM and then characterized at the IM2NP institute. The antireflective performances obtained are remarkable (reflection coefficient lower than 2 % at normal incidence) and extend over a wide spectral range from the visible to the infrared region. The second demonstrator presents a low-pass type filtering function at optical and infrared frequencies. A study of several resonant structures such as metamaterials (metallic crosses, metal-dielectric-metal stack, metallic cones and perforated plates) showed singular propagation phenomena related to small dimensions (modes, surface waves and proximity coupling) and led to the completion of a large surface, flexible filter demonstrating the desired properties. The photonic components made during this thesis have applications in the stealth and thermal solar domains
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Tabasso, Alberto. "Spatially resolved measurement of photon fluxes from the JET divertor on the visible range." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286688.
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Morel, Yannick. "Optimisation de matériaux organiques absorbant à deux photons pour la protection laser dans le visible." Université Joseph Fourier (Grenoble ; 1971-2015), 2001. http://www.theses.fr/2001GRE10111.
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Nous presentons dans ce travail l'optimisation de materiaux organiques absorbant a deux photons pour la limitation optique dans le visible. En regime nanoseconde, le phenomene de limitation optique est issu d'un processus d'absorption non-lineaire a trois photons. Ce processus se decompose en deux etapes : une absorption a deux photons suivie d'une absorption entre etats excites. Nous presentons trois exemples d'ingenierie moleculaire sur differentes familles de molecules organiques : des derives de biphenyles, des derives de bis-stilbenes, et des oligomeres. Cette derniere famille presente une nouvelle voie d'optimisation des proprietes d'absorption a deux photons grace aux couplages entre les monomeres. Les oligomeres de fluorene possedent des sections efficaces d'absorption a deux photons superieures aux autres familles etudiees de plusieurs ordres de grandeur. Notre travail a egalement montre les avantages et inconvenients de la mise en forme des materiaux en cristaux et nanocristaux. Finalement, nous avons demontre les performances de limitation optique de ces materiaux en regime nanoseconde et dans le visible (450-650 nm).
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ANEMIAN, REMI. "Ingenierie moleculaire pour l'optimisation des effets lies a l'absorption a deux photons dans le visible." Lyon, École normale supérieure (sciences), 2001. http://www.theses.fr/2001ENSL0204.
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La protection large bande contre les agressions laser dans la region spectrale du visible (450 nm - 650 nm) requiert des materiaux capables de limiter le flux optique entrant dans un systeme optique ; dans ce cadre, les materiaux organiques presentant une forte absorption non lineaire se sont reveles etre des candidats prometteurs. En regime nanoseconde, l'absorption non lineaire correspond a un processus a deux etapes : une absorption instantanee de deux photons (adp) suivie par une absorption a partir de l'etat excite se produisant pendant la duree de l'impulsion. Dans ce contexte, notre travail a pour objectif l'exaltation de l'absorption non lineaire par l'optimisation (i) des proprietes d'adp et (ii) des effets d'absorption a partir de l'etat s 1 induits par adp. (i) la strategie fondee sur l'augmentation du transfert s'est revelee certes efficace, mais conduit a des molecules plus colorees. Devant les limites de cette methode pour les applications dans le visible, nous avons developpe une approche oligomere fondee sur l'exploitation des effets d'interactions dans le modele excitonique. Des calculs semi-empiriques ont permis de predire une exaltation significative de la section efficace d'adp avec le nombre d'unites. Pour mettre en uvre au plan experimental cette approche, nous avons mis au point une strategie de synthese d'oligofluorenes de type monodisperse dont l'etude est en cours. (ii) l'application de la strategie fondee sur l'optimisation des proprietes liees a l'etat excite par la reduction des processus de relaxation a egalement conduit dans le cas de triarylamines substituees a une exaltation des proprietes d'absorption non lineaire. Ce travail, qui a permis d'obtenir des composes particulierement efficaces pour la limitation optique en regime nanoseconde dans le visible, ouvre de nouvelles perspectives pour d'autres applications necessitant des materiaux avec de grandes sections efficaces d'adp comme la photopolymerisation ou l'imagerie biomedicale.
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Fisher, Edward Michael Dennis. "Parallel reconfigurable single photon avalanche diode array for optical communications." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/11690.
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There is a pressing need to develop alternative communications links due to a number of physical phenomena, limiting the bandwidth and energy efficiency of wire-based systems or economic factors such as cost, material-supply reliability and environmental costs. Networks have moved to optical connections to reduce costs, energy use and to supply high data rates. A primary concern is that current optical-detection devices require high optical power to achieve fast data rates with high signal quality. The energy required therefore, quickly becomes a problem. In this thesis, advances in single-photon avalanche diodes (SPADs) are utilised to reduce the amount of light needed and to reduce the overall energy budget. Current high performance receivers often use exotic materials, many of which have severe environmental impact and have cost, supply and political restrictions. These present a problem when it comes to integration; hence silicon technology is used, allowing small, mass-producible, low power receivers. A reconfigurable SPAD-based integrating receiver in standard 130nm imaging CMOS is presented for links with a readout bandwidth of 100MHz. A maximum count rate of 58G photon/s is observed, with a dynamic range of ≈ 79dB, a sensitivity of ≈ −31.7dBm at 100MHz and a BER of ≈ 1x10−9. We investigate the properties of the receiver for optical communications in the visible spectrum, using its added functionality and reconfigurability to experimentally explore non-ideal influences. The all-digital 32x32 SPAD array, achieves a minimum dead time of 5.9ns, and a median dark count rate (DCR) of 2.5kHz per SPAD. High noise devices can be weighted or removed to optimise the SNR. The power requirements, transient response and received data are explored and limiting factors similar to those of photodiode receivers are observed. The thesis concludes that data can be captured well with such a device but more electrical energy is needed at the receiver due to its fundamental operation. Overall, optical power can be reduced, allowing significant savings in either transmitter power or the transmission length, along with the advantages of an integrated digital chip.
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Conroy, Matthew James. "NMR studies of bacterial light-harvesting complexes." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298888.
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Cao, Bertrand. "Systèmes performants pour la limitation optique large bande dans le visible et le proche infrarouge." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2009. http://tel.archives-ouvertes.fr/tel-00363735.
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La protection des systèmes d'observations contre les lasers impulsionnels et accordables en longueurs d'onde passe par l'utilisation de matériaux non linéaires auto activés. Parmi ces matériaux, les absorbeurs à deux photons (ADP), qui suscitent un intérêt croissant de par les nombreuses applications, constituent une solution intéressante pour obtenir des limiteurs présentant une bonne transparence et une réponse rapide. Dans une première partie, nous étudions différentes familles de chromophores ADP pour la limitation optique (OL): systèmes branchés purement organiques à base de fluorène (molécules octupolaires et en "V", dendrimères) optimisés pour le visible, et complexes organométalliques pour le proche infrarouge. Dans une seconde partie, une nouvelle voie reposant sur la combinaison de nanotubes de carbones avec d'autres matériaux optiquement non linéaires est explorée afin d'induire des effets coopératifs susceptibles d'améliorer les performances de LO. Nous nous sommes d'abord intéressés à des nanotubes de carbone combinés avec des nano particules d'or, puis nous nous sommes focalisés sur l'étude d'un nouveau système hybride nanotube de carbone/fullerène C6o. Dans ce dernier système, les chromophores C6o absorbeurs saturables inverses (ASI) sont directement greffés à la surface des nanotubes. Les résultats obtenus ont permis de mettre en évidence un effet coopératif résonnant entre les deux entités, pour lequel nous proposons une interprétation physique basée sur un mécanisme de recombinaison Auger.
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Kalusniak, Sascha. "Ultraviolet and visible semiconductor lasers based on ZnO heterostructures." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://dx.doi.org/10.18452/16898.
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Im Rahmen dieser Arbeit wurden die optischen Eigenschaften von auf ZnO-basierenden Heterostrukturen untersucht. Besonderes Augenmerk lag hierbei auf ihrer Eignung als aktives Material in Laserdioden für den ultravioletten und sichtbaren Spektralbereich. Es wurde gezeigt, dass ZnO und seine ternären Mischkristalle ZnCdO und ZnMgO erstaunlich vielfältige Anwendungen ermöglichen. Mit diesem Materialsystem lässt sich sowohl ein sehr großer Spektralbereich für Lasertätigkeit abdecken als auch eine Vielzahl von Laseranordnungen realisieren. Im Detail wurde demonstriert, dass sich die Lasertätigkeit von ZnCdO/ZnO Quantengraben-Strukturen vom violetten bis in den grünen Spektralbereich verschieben lässt. Obwohl diese Strukturen starke interne elektrische Felder aufweisen, konnte optisch gepumpte Lasertätigkeit bei Zimmertemperatur bis zu einer Wellenlänge von 510 nm gezeigt werden. Die für die Lasertätigkeit nötige optische Rückkopplung wird durch makroskopische Defekte der Probe verursacht und die Proben fungieren somit als Zufallslaser. Die Herstellung von Mikroresonatoren ermöglichte die Untersuchung des Zusammenspiels von Fabry-Perot- und Zufalls-Rückkopplung. Die experimentellen und theoretischen Ergebnisse zeigen, dass der Schwellengewinn eines Zufallslasers in der Regel größer ist als der des Fabry-Perot-Lasers. Des Weiteren wurde gezeigt, dass hoch reflektierende Braggreflektoren für den ultravioletten und blau/grünen Spektralbereich aus ZnO- und ZnMgO-Schichten hergestellt werden können. Ferner wurden die teils unbekannten Brechungsindexverläufe der verwendeten ternären Materialen erarbeitet und Mikrokavitäten mit ZnO/ZnMgO Quantengraben Strukturen als aktive Schichten realisiert. An diesen Kavitäten konnte bei Temperaturen bis zu 150 K starke Kopplung zwischen Exzitonen und Photonen nachgewiesen werden. Bei Zimmertemperatur konnte vertikal-emittierende Lasertätigkeit im nahen ultravioletten Spektralbereich demonstriert werden.In the framework of this thesis, the optical properties of ZnO-based heterostructures fabricated by molecular beam epitaxy have been investigated, particularly with regard to their suitability for semiconductor laser devices operating in the ultraviolet and visible spectral range. It turned out that ZnO and its ternary alloys ZnMgO and ZnCdO are extremely versatile. They allow to tune the laser emission in a wide spectral range as well as to realize various laser geometries. In detail, it was shown that the laser emission of ZnCdO/ZnO multiple quantum wells can cover a spectral range from violet to green wavelengths. Although these structures suffer from large built-in electric fields, room temperature laser action under optical pumping was demonstrated up to a wavelength of 510. The optical feedback for lasing is provided by growth imperfections on a macroscopic length scale turning these structures into random lasers. The fabrication of micro-resonators allowed to study the interplay between random and Fabry-Perot feedback. The experimental and theoretical analysis shows that random feedback generally requires a larger gain than under Fabry-Perot feedback. Further, this work demonstrates that ZnO- and ZnMgO-layers can be used to fabricate highly reflective distributed Bragg reflectors for applications in the ultraviolet and blue/green spectral range. The partly unknown dispersion curves of the index of refraction of the employed ternary alloys have been elaborated. This enabled the realization of all monolithic microcavities with ZnO/ZnMgO quantum wells as active zone. For temperatures below 150 K strong exciton-photon coupling is observed in such microcavities. At room temperature, vertical cavity surface emitting laser action in the near UV spectral range is demonstrated for appropriately designed microcavities.
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Denneval, Charline. "Design, synthèse et évaluation de contrastophores bimodaux pour l'imagerie par absorption à deux photons et par tomographie par émission de positons." Thesis, Rouen, INSA, 2014. http://www.theses.fr/2014ISAM0012/document.
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L’objectif de ce travail a porté sur l’élaboration d’une sonde bimodale ADP–TEP (absorption à deux photons–tomographie par emission de positons) pour des applications en imagerie médicale.Dans un premier temps, le projet a consisté en le design, la synthèse et l’évaluation des propriétés photophysiques d’une nouvelle série de chromophores diaziniques A–p–D (A : groupement électro-attracteur, p : lien conjugué, D : groupement électro-donneur). Des études de relation structure-propriétés photophysiques impliquant des modulations sur chacune des sous-structures (groupements A et D, lien p-conjugué) ont été réalisées puis étudiées en UV et en fluorescence. Suite à l’obtention de ces premiers résultats, des mesures d’absorption à deux photons ont été effectuées sur ces fluorophores.Dans un second temps, les fluorophores ont été modifiés afin de greffer des parties hydrophiles. Des propriétés photophysiques encourageantes ont été obtenues et des premiers tests en imagerie bi-photonique ont été réalisés.L’insertion du fluor radiomarqué est envisagée via l’insertion d’un groupement –BF2. Pour cela des structures chélatantes, « mimes de BODIPY », incorporant une pyrimidine ou un triazole ont été élaborées. Des premiers essais ont été conduits mais n’ont pas permis l’obtention des composés borés correspondantsThe purpose of this subject has been the synthesis of a bimodal probe using TPA–PET techniques for a potential application in biological imaging.In this context, we have synthesized a new range of A–π –D fluorophores incorporating diazine (p-deficient heterocycle) as electron-withdrawing moiety, N,N-dimethylaniline as electron-donating part and fluorene as p-conjugated linker. In order to increase the conjugation along the scaffold, ethynyl and/or triazole bridges have been introduced on both sides of the fluorene. The UV/Vis and photoluminescence properties have been measured. Further to those results two-photon absorption cross-section of our fluorophores (dTPA) has been obtained. Following these promising results, hydrophilic compounds using PEG groups have been prepared and photoluminescence properties have been carried out. In order to use the boron center as a site for radiofluorination, the synthesis of "BODIPY-like" probes has been considered. A new series of pyrimidine and triazole ligand have been synthesized but the corresponding boron complexes haven’t been obtained
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Gendron, François. "Étude spectroscopique de métaux de transition dans les semi-conducteurs." Paris 6, 1986. http://www.theses.fr/1986PA066001.
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Étude par RPE, absorption optique et photoluminescence de ZnS : Ni, ZnTe : Ni et GaAs : Ni, effets du champ magnétique et d'une contrainte. Mise en évidence d'une raie à zéro phonon dans les processus d'absorption, interprétation par la transition interne **(2)T::(2) -> **(2)E de Ni**(+) isolé.
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TOUAHRI, DRISS. "Developpement d'une chaine de synthese de frequences de l'infrarouge au visible : application a la mesure de la frequence de la transition a deux photons 5s#1#/#2 (f=3) - 5d#5#/#2 (f=5) du rubidium (#8#5rb) a 385 thz (778 nm)." Paris 11, 1996. http://www.theses.fr/1996PA112262.
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L'objet de cette these est la mesure de la frequence absolue de la transition a deux photons 5s#1#/#2 (f=3) - 5d#5#/#2 (f=5) du rubidium a 385 thz (778 nm) sur laquelle est asservie une diode laser. Les performances metrologiques de ce dispositif sont: stabilite: 4 x 10#-#1#3 #-#1#/#2 repetabilite: 5 x 10#-#1#3 reproductibilite: 2 x 10#-#1#2 elles en font un candidat tres prometteur en tant qu'etalon secondaire de frequence dans le domaine visible. La frequence de cette transition est mesuree a l'aide d'une chaine de multiplication de frequence. La frequence d'un laser a co#2 stabilisee sur une transition de la molecule de oso#4 a 29 thz, est multipliee par 13 en quatre etapes, a l'aide de dispositifs non-lineaires (une diode mim et trois cristaux d'aggas#2). Les frequences de trois dispositifs similaires ont ete mesurees simultanement. Deux sont localises au lptf/observatoire de paris. Le troisieme situe au laboratoire kastler-brossel (ens/paris vi) est relie a la chaine de mesure du lptf par une fibre optique longue de 3 km. Ce laser etalon est utilise comme reference de frequence pour l'etude spectroscopique a tres haute resolution de l'atome d'hydrogene. La resolution de la chaine de frequence developpee au lptf est meilleure que 1 x 10#-#1#3. La mesure est limitee principalement par la stabilite des etalons de frequence a rubidium. La valeur de la frequence de la transition a deux photons 5s#1#/#2 (f=3) - 5d#5#/#2 (f=5) ainsi mesuree est: = 385 285 142 378. 280 2 khz l'incertitude de 2 khz prend en compte les ecarts observes entre les trois dispositifs
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Ayed, Othman. "Etude des interactions entre atomes alcalins (li, na, k) et monoxyde de carbone en matrices de gaz rares : analyse en spectroscopie vibrationnelle et calcul quantiques de quelques complexes." Paris 6, 1987. http://www.theses.fr/1987PA066117.
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Dans le cas de li(le plus reactif), identification de li(co)::(n), ou n = 1,2,3,4,(ou 6), avec des frequences de vibration de valence de co plus perturbees que pour les metaux de transition carbonyle,et de li::(m) co, ou m = 2,3, avec frequences nu (co) abaissees. Pour na et k, observation d'especes de haute stoechiometrie (c::(n)o::(n))**(2-) (m**(+))::(2) ou n = 2,3,4, formees apres irradiation uv-visible et correspondant a des transformations chimiques. Essai d'interpretation de ces differences de reactivite par une description quantique des agregats de plus basse stoechiometrie : dans le complexe 1 :1, les deux etats electroniques inferieurs sont l'etat **(2)sigma non liant et l'etat **(2)pi liant; la courbe de potentiel de lico possede un minimum pour li-c equiv. A 2,5 a au-dessous de la courbe de l'etat **(2)pi alors que pour naco, le minimum de la courbe pour l'etat **(2)pi est au-dessous de la courbe de l'etat **(2)sigma ; le calcul met en evidence le caractere ionique de m::(2)c::(2)o::(2) (acetylenediolate) resultant d'une reaction chimique
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Doclot, Olivier. "Etude des propriétés optiques non linéaires de troisième ordre de la molécule et du cristal de 4-(N,N diéthylamino)-b-nitrostyrène par Z scan et ellipsométrie." Grenoble 1, 1996. http://www.theses.fr/1996GRE10230.
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Dans cette these, nous avons etudie les proprietes optiques non lineaires de troisieme ordre de la molecule et du cristal de 4-(n,n diethylamino)-nitrostyrene (deanst). Nous avons fait des mesures d'absorption a deux photons de la molecule de deanst en solution par ellipsometrie kerr. Nous avons modelise le spectre non lineaire ainsi obtenu a partir du spectre d'absorption lineaire et d'un unique parametre: la variation de moment dipolaire entre les etats s#0 et s#1. Nous avons monte un banc z scan qui permet la mesure de l'indice de refraction dependant de l'intensite et de l'absorption non lineaire aux deux longueurs d'onde 1,064 m et 532 nm. Les mesures a 1,064 m en solutions ont montre que la variation d'indice de refraction est dominee par l'effet d'orientation moleculaire et que l'absorption a deux photons est faible a cette longueur d'onde. Les mesures effectuees a 532 nm dans une bande d'absorption a un photon de la solution de deanst mettent en evidence de fortes non-linearites dues a la creation d'une population dans un etat excite. Ces mesures montrent qu'aux concentrations elevees, les molecules isolees ne sont pas les seules a jouer un role dans les proprietes non lineaires des solutions. Les mesures z scan sur le cristal de deanst revelent l'anisotropie de ses proprietes non lineaires. De plus, l'absorption non lineaire n'est pas uniquement interpretable par un phenomene de troisieme ordre et necessite l'intervention d'un coefficient non lineaire supplementaire. L'analyse des non-linearites du cristal de deanst doit etre envisagee dans le cadre d'un modele excitonique: le modele du gaz oriente en considerant une hyperpolarisabilite dominee par l'element tensoriel le long du grand axe de la molecule ne rend pas compte des non-linearites du cristal
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Goutaland, François. "Processus multiphotoniques, défauts ponctuels et mécanismes de leur formation dans les fibres optiques : étude par spectroscopie laser." Saint-Etienne, 1998. http://www.theses.fr/1998STET4021.
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Ce mémoire se compose de deux parties, la première consacrée à l'étude des processus multiphotoniques se produisant dans des fibres optiques fortement dopées avec des ions er3+ et yb3+, et la seconde à l'étude des défauts induits par différents traitements dans des fibres germanosilicates. En étudiant la spectroscopie d'émission des fibres fortement dopées, sous excitations visibles (488 nm) et infrarouge (790 - 880 nm), nous mettons en évidence les différents mécanismes aux émissions bleues, vertes et rouge observées. Deux principaux types de processus d'up - conversion peuvent alors être distingués : ceux faisant appel aux transferts d'énergie Yb er et ceux faisant intervenir le phénomène d'absorption dans l'état excité (ESA). L'influence de la longueur de fibre et des concentrations en ions de terre rare sur les efficacités respectives de chacun de ces deux mécanismes est ensuite abordée. Après une présentation bibliographique des différents défauts dans la silice et les fibres germanosilicates, nous présentons le phénomène appelé dépendance modale du spectre d'émission d'une fibre optique, c'est-à-dire la variation du spectre d'émission d'une fibre en fonction du mode excité. L'évolution avec la température d'une bande d'émission centrée autour de 600 nm nous permet ensuite d'attribuer cette émission à des radicaux péroxys. Nous montrons alors que ces radicaux péroxys peuvent être photoinduits dans le CUR des fibres par irradiation intense à 488 nm. Enfin, nous étudions par spectroscopie Raman et spectroscopie d'émission les défauts générés dans deux types de fibres germanosilicates irradiées à 240 nm. Une technique de filtrage spatial du mode excité permet alors de séparer les défauts photoinduits dans le CUR de ces fibres de ceux localisés près de l'interface CUR/gaine
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Prasad, Tushar. "Photonic crystals at visible, x-ray, and terahertz frequencies." Thesis, 2008. http://hdl.handle.net/1911/22186.
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Photonic crystals are artificial structures with a periodically varying refractive index. This property allows photonic crystals to control the propagation of photons, making them desirable components for novel photonic devices. Photonic crystals are also termed as "semiconductors of light", since they control the flow of electromagnetic radiation similar to the way electrons are excited in a semiconductor crystal. The scale of periodicity in the refractive index determines the frequency (or wavelength) of the electromagnetic waves that can be manipulated.
This thesis presents a detailed analysis of photonic crystals at visible, x-ray, and terahertz frequencies. Self-assembly and spin-coating methods are used to fabricate colloidal photonic crystals at visible frequencies. Their dispersion characteristics are examined through theoretical as well as experimental studies. Based on their peculiar dispersion property called the superprism effect, a sensor that can detect small quantities of chemical substances is designed. A photonic crystal that can manipulate x-rays is fabricated by using crystals of a non-toxic plant virus as templates. Calculations show that these metallized three-dimensional crystals can find utility in x-ray optical systems. Terahertz photonic crystal slabs are fabricated by standard lithographic and etching techniques. In-plane superprism effect and out-of-plane guided resonances are studied by terahertz time-domain spectroscopy, and verified by numerical simulations.
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Lin, Tung-Ching, and 林東慶. "High-speed GaN-based Photonic Crystal Light-emitting Diodes for Visible Light Communication Applications." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/srw2p5.
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碩士國立臺灣大學
光電工程學研究所
105
Recently, GaN based light-emitting-diodes (LEDs) have attracted a lot of attention as they can be applied to visible light communication (VLC) as the transmitter. However, the modulation bandwidth of LEDs is usually limited by the spontaneous carrier lifetime in the multiple quantum wells. Nowadays, much research has been investigated to solve this problem. In this thesis, we discuss the photonic crystal (PhC) structure embedded in LED (PhCLED) which can improve the performance of the devices on high-speed operation due to its unique spatial and temporal management. In the first part of this thesis, we compare four kind of various PhC structures with corresponding dynamic behaviors in the small signal modulation. Faster transient responses and higher efficiency of the out-coupled modes were obtained in the room-temperature time-resolved photoluminescence (TRPL) and Raman scattering measurement. For the best performance, an optimal design of PhCs, with a larger period and a larger air-hole portion characterizes PhCLEDs achieved the highest f-3dB bandwidth of 347 MHz, which corresponds a 55% enhancement of modulation bandwidth compared to a convention LED. For LEDs on visible light communication applications, there is generally a trade-off of high-speed performance of the LEDs. By shrinking the mesa area, LEDs can achieve higher bandwidth but at the cost lower light output, which is unfavorable when the signal-to-noise ratio (SNR) is the concern for large-signal modulation. In the second part of our work, we demonstrated data transmission capability of our devices. The eye pattern up to 400Mb/s using on-off keying (OOK) modulation is observed. Moreover, VLC with 16-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) transmission capacity up to 2Gbit/s is achieved from the LEDs with PhC with an error vector magnitude (EVM) of 8.4%, signal-to-noise ratio (SNR) of 17.05dB and bit-error-rate (BER) of 3.8 x 10^(-3) passes the forward error correction (FEC) criterion. The results reveals the advantages of LEDs with PhC for achieving higher data rate transmission.
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Lin, Yi-Sheng, and 林益生. "New design of optical devices with visible spectrum based on planar photonic crystal structure." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/25714217100290692465.
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碩士國立高雄應用科技大學
電子工程系
97
In this thesis, we discussed the application of all-optical devices in the visible spectrum based on compound-material and Left-handed behavior in the photonic crystals. A photonic crystal is a revolutionary class of artificially periodic electromagnetic media, in which a fundamentally new electromagnetic phenomenon can be achieved. A photonic band gap defines a range of frequencies for which light is forbidden to exist inside the crystal. We by using crystal defect, plane-wave expansion method and finite-difference time-domain method to analyzed photonic crystal optical devices structure. Firstly, we by varying the radius of the material rods of the left-handed structure，the light beam would be controlled by negative refraction propagating behavior based on photonic crystals. The distance of path 1 is the same as path 2. The source beam can be split to two propagating paths in compound structure. We present a novel photonic crystal cloaking device at visible spectrum based on the association of two lattices working in different regimes, namely, stop band and negative refraction. Finally, we presented the novel visible wavelength division multiplexer based on ultralow-refractive-index. The metamaterial structure is devoted to the visible optical characterization, through a periodic structure of compound-material of metallic and semiconductor in air. In addition, we are modify our crystals radius of metamaterial, to obtain a better effect with that has cut down loss and cross talk.
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Kouba, Josef [Verfasser]. "Investigation of silicon nitride based two-dimensional photonic crystals for the visible spectral range / Josef Kouba." 2008. http://d-nb.info/989315703/34.
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Shen, Chao. "III-nitride Photonic Integrated Circuit: Multi-section GaN Laser Diodes for Smart Lighting and Visible Light Communication." Diss., 2017. http://hdl.handle.net/10754/625282.
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The past decade witnessed the rapid development of III-nitride light-emitting diodes (LEDs) and laser diodes (LDs), for smart lighting, visible-light communication (VLC), optical storage, and internet-of-things. Recent studies suggested that the GaN-based LDs, which is free from efficiency droop, outperform LEDs as a viable high-power light source. Conventionally, the InGaN-based LDs are grown on polar, c-plane GaN substrates. However, a relatively low differential gain limited the device performance due to a significant polarization field in the active region. Therefore, the LDs grown on nonpolar m-plane and semipolar (2021)-plane GaN substrates are posed to deliver high-efficiency owing to the entirely or partially eliminated polarization field. To date, the smart lighting and VLC functionalities have been demonstrated based on discrete devices, such as LDs, transverse-transmission modulators, and waveguide photodetectors. The integration of III-nitride photonic components, including the light emitter, modulator, absorber, amplifier, and photodetector, towards the realization of III-nitride photonic integrated circuit (PIC) offers the advantages of small-footprint, high-speed, and low power consumption, which has yet to be investigated. This dissertation presents the design, fabrication, and characterization of the multi-section InGaN laser diodes with integrated functionalities on semipolar (2021)-plane GaN substrates for enabling such photonic integration. The blue-emitting integrated waveguide modulator-laser diode (IWM-LD) exhibits a high modulation efficiency of 2.68 dB/V. A large extinction ratio of 11.3 dB is measured in the violet-emitting IWM-LD. Utilizing an integrated absorber, a high optical power (250mW), droop-free, speckle-free, and large modulation bandwidth (560MHz) blue-emitting superluminescent diode is reported. An integrated short-wavelength semiconductor optical amplifier with the laser diode at ~404 nm is demonstrated with a large gain of 5.32 dB at 6 V. A high-performance waveguide photodetector integrated LD at 405 nm sharing the single active region is presented, showing a significant large modulation bandwidth of 230 MHz. Thus these seamlessly integrated elements enable photonic IC at the visible wavelength for many important applications, such as smart lighting and display, optical communication, switching, clocking, and interconnect. The findings are therefore significant in developing an energy-saving platform technology that powers up human activities in a safe, health- and environmental-friendly manner.
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Menon, Sruti Hemachandran Geetha. "Medium Index Contrast Guided Mode Resonant Structures for Photonic Applications in the Visible-Near Infrared Wavelength Regime." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5746.
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Guided mode resonant (GMR) structures are interesting from the point of view of enhanced light-matter interaction and find applications in sensing, filtering, and miniaturized photonic components. The Guided mode resonance (GMR) arises due to the coupling of the incident light into the guiding medium, followed by interference of the leaky modes with the reflected/transmitted light, resulting in high Q resonance features with field enhancement in and around the structure. GMR structures using high refractive index materials like silicon, germanium, gallium arsenide are explored widely due to the high scattering capability of the material. However, such materials are lossy and are not suitable for visible frequency applications. On the other hand, GMR structures based on materials like silicon dioxide, titanium dioxide, polymer, silicon nitride are transparent in the visible frequency regime yet are not widely studied due to its weak refractive index and low scattering capability. In this thesis, silicon nitride and gallium nitride-based GMR with refractive index contrast of ~0.4-1.5 with respect to the substrate are studied for fluorescence and nonlinear enhancement studies.
In this first part of the work, the high refractive index contrast gratings are compared with the weak refractive index contrast gratings and the techniques are studied to widen the narrow design space encountered in weak refractive index gratings by altering the design parameters of the gratings. Further, fully etched silicon nitride gratings with 80% duty cycle are studied for resonantly enhancing the absorption and emission of the Rhodamine B ITC dye using TE and TM polarized resonances, respectively. The fluorescence enhancement of 10.8 times obtained experimentally using TE polarized excitation and TM polarized collection is then corroborated with simulations by representing the fluorophores to be an array of dipoles in presence of gratings to model the effect of polarization-sensitive resonances on the enhancement of absorption and fluorescence. The GMR structure discussed in this study proves to be a promising approach to realize highly sensitive fluorescence assays and to probe polarization-sensitive information from 2D materials transferred onto these structures.
Next, layered GMR structures consisting of silicon dioxide gratings conformally coated with silicon nitride are studied for resonantly enhancing the third harmonic generation from the 10 nm amorphous silicon layer. The GMR structure is designed to have maximum field interaction with the amorphous silicon layer. In addition, it also behaves as a passive medium with low inherent absorption and nonlinearity, enabling the integration of these structures with other highly nonlinear medium of interest. The GMR structure being sensitive to the incidence angle, the contrast of the resonances and THG enhancement is learned to decrease with an increase in the divergence angle of the incident beam. Experimentally, the backward THG enhancement measured as the ratio of backward THG power in presence of grating and in absence of grating increases from 18 times to 1120 times when the angular spread is reduced from 11 degree to 2.3 degree. This is corroborated with Gaussian beam-based simulations which show good agreement with the experimental results. The structure discussed here enables THG enhancement from the thinnest amorphous silicon layer to the best of our knowledge with minimal absorption at the THG wavelength and provides a scalable platform for nonlinear enhancement and sensing based applications.
Furthermore, the gratings being a one-dimensional periodic structure, the angular sensitivity of the resonances reduces in case of full-conical illumination with the projected wave vector parallel to the grating lines as compared to the full-classical illumination with the projected wave vector perpendicular to the grating lines. Leveraging this concept, four orders of forward THG enhancement is reported using a partial conical illumination setup with a rectangular pupil mask placed at the back focal plane of the objective to limit the angles perpendicular to the gratings, while allowing full angular spread supported by the objective along the grating lines. With this setup, improvement in THG enhancement from 2860 to 1.7x10^4 is observed when the angular spread perpendicular to the grating lines is reduced from 2.3 degree to 0.43 degree. The THG enhancement obtained in this work is the best reported so far from 10 nm silicon to the best of our knowledge and the technique discussed here paves way for enhanced nonlinear generation from any angle-sensitive structure.
Finally, a simulation and experimental based study of amorphous silicon-Gallium Nitride based heterogeneous structures on sapphire substrate is performed for resonant enhancement of second order harmonic generation (SHG) in 5 𝜇m thick c-Gallium Nitride. Due to the restrictions imposed by the lattice symmetry in c-Gallium Nitride material, it is necessary to have enhanced longitudinal and transverse fundamental field components to ensure the efficient excitation of nonlinear polarization terms and to efficiently radiate the in-plane polarized SHG, thereby enabling enhanced excitation and collection of SHG using low NA optics. With 45 degree polarized fundamental incidence, TE and TM polarized resonances are simultaneously excited in these structures which leads to efficient SHG generation with maximum in-plane polarized component radiated along the optic axis. Experimentally, 1300 times SHG enhancement is demonstrated at 1460 nm, with the measured SHG efficiency of 1.54 x 10^-3 %/W at a smaller peak intensity of 0.11 GW/cm^2. The measured efficiency is comparable to the reported SHG efficiencies in x-cut Lithium Niobate based structures with d33 axis in-plane allowing efficient excitation and collection of SHG and higher as compared to the z-cut Lithium Niobate structures with maximum susceptibility component d33 oriented out-of-plane similar to the c-Gallium Nitride material studied in this work. This work reports the best SHG efficiency value from Gallium Nitride when compared to previous work on GaN based muti-quantum well based metasurfaces.
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"Nonlinear Integrated Photonics in the Visible Spectrum Based on III-N Material Platform." Doctoral diss., 2020. http://hdl.handle.net/2286/R.I.62652.
Full textAbstract:
abstract: Photonic integrated circuit (PIC) in the visible spectrum opens up new opportunities for frequency metrology, neurophotonics, and quantum technologies. Group III nitride (III-N) compound semiconductor is a new emerging material platform for PIC in visible spectrum. The ultra-wide bandgap of aluminum nitride (AlN) allows broadband transparency. The high quantum efficiency of indium gallium nitride (InGaN) quantum well is the major enabler for solid-state lighting and provides the opportunities for active photonic integration. Additionally, the two-dimensional electron gas induced by spontaneous and polarization charges within III-N materials exhibit large electron mobility, which is promising for the development of high frequency transistors. Moreover, the noncentrosymmetric crystalline structure gives nonzero second order susceptibility, beneficial for the application of second harmonic generation and entangled photon generation in nonlinear and quantum optical technologies. Despite the promising features of III-N materials, the investigations on the III-N based PICs are still primitive, mainly due to the difficulties in material growth and the lack of knowledge on fundamental material parameters. In this work, firstly, the fundamental nonlinear optical properties of III-N materials will be characterized. Then, the fabrication process flow of III-N materials will be established. Thirdly, the waveguide performance will be theoretically and experimentally evaluated. At last, the supercontinuum generation from visible to infrared will be demonstrated by utilizing soliton dynamics in high order guided modes. The outcome from this work paves the way towards fully integrated optical comb in UV and visible spectrum.Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2020
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McKay, Kyle. "Development of the Visible Light Photon Counter for Applications in Quantum Information Science." Diss., 2011. http://hdl.handle.net/10161/4990.
Full textAbstract:
The visible light photon counter (VLPC) is a high quantum efficiency (QE), Si-based, single-photon detector with high gain, low-noise multiplication, low timing jitter, and photon number resolution. While the VLPC has high QE in the visible wavelengths, the QE in the ultraviolet and infrared is low due to minimal absorption within the active layers of the device. In the ultraviolet, the absorption coefficient of Si is high and most of the incident photons are absorbed within the top contact of the device, whereas, in the infrared, Si is practically transparent. A number of applications in quantum information science would benefit from use of the VLPC if the QE was improved in the ultraviolet (e.g., state detection of trapped ions) and the infrared (e.g., long-distance quantum cryptography). This thesis describes the development of the ultraviolet photon counter (UVPC) and the infrared photon counter (IRPC), which are modified versions of the VLPC with increased QE in the ultraviolet and infrared wavelengths, respectively. The UVPC has a transparent metal Schottky contact to reduce absorption within the top contact of the VLPC, resulting in an increase in the QE in the ultraviolet by several orders of magnitude. The IRPC is a proposed device that has an InGaAs absorption layer that is wafer-fusion bonded to the VLPC. The band alignment of the resulting InGaAs/Si heterojunction is measured and shows a large discontinuity in the valence band that impedes carrier transport at the interface. A ultra-high vacuum wafer-bonding system was developed to understand the impact of the surface chemistry of the bonded wafers on the band alignment of the InGaAs/Si heterojunction of the IRPC.
Dissertation
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Sinha, Sujata. "OTFS Modulation in MIMO Visible Light Communication Systems." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5739.
Full textAbstract:
Visible light communication (VLC) technology is emerging as an attractive technology for wireless communication in indoor and vehicular environments. In VLS systems, light emitting diodes (LED) and photo diodes (PD) are used for wireless signal transmission and reception, respectively, using the visible light spectrum. VLC systems are gaining popularity because of their ability to provide lighting and short-range communication simultaneously. Recently, a new modulation scheme called orthogonal time frequency space (OTFS) modulation has been introduced in the radio frequency (RF) communications domain, where it has been shown that OTFS achieves significantly better performance compared to the widely used orthogonal frequency division multiplexing (OFDM). OTFS is a two-dimensional (2D) modulation scheme, where MN information symbols are multiplexed in the delay-Doppler (DD) domain using M Doppler bins and N delay bins. This is in contrast to OFDM where information symbols are multiplexed in the time-frequency (TF) domain. Because of the demonstrated superiority of OTFS in the RF communication domain, research in OTFS for VLC systems has gained importance recently. In this context, it is of interest to 1) adapt OTFS waveform to VLC settings, and 2) investigate the performance OTFS in indoor VLC environments. In this thesis, we propose efficient multi-LED OTFS modulation schemes suited for visible light communication and analyze their bit error performance in indoor communication environments.
First, we propose two dual-LED transmission schemes, namely, non-DC-biased OTFS (NDC-OFTS) scheme and dual-LED complex modulation OTFS (DCM-OTFS) scheme. The NDC-OTFS scheme uses 2D Hermitian symmetry operation to convert complex signals to positive, real-valued signals suitable for transmission in the optical domain, and the DCM-OTFS scheme achieves this by exploiting the polar representation of complex signals. We obtain analytical upper bounds on the bit error performance of the proposed schemes, which are found to be tight at high signal-to-noise ratios (SNRs). Our analytical and simulation results show that the proposed OTFS schemes achieve better performance compared to their OFDM counterparts reported in the VLC literature. Further, using the ratio of the minimum distance of different normalized received signal sets as a metric, we quantify the spatial distribution of the SNR gain of the OTFS schemes compared to their OFDM counterparts.
Next, we propose two quad-LED architectures, namely, quad-LED complex modulation OTFS (QCM-OTFS) scheme and spatial modulation DCM-OTFS (SM-DCM-OTFS) scheme. The QCM-OTFS scheme sends the magnitudes of real and imaginary parts of complex signals through intensity modulation and their sign information through spatial indexing of LEDs. The proposed SM-DCM-OTFS scheme sends the magnitude and phase of complex signals (polar representation) through a pair of LEDs and frame indexing across two pairs of LEDs. We also propose two multi-LED OTFS schemes, namely, quadrature spatial modulation OTFS (QSM-OTFS) scheme and dual mode index modulation OTFS (DMIM-OTFS) scheme. The proposed schemes use the dual-LED complex modulation block as the basic building block and offer enhanced rates compared to conventional index modulation schemes. The proposed schemes have the advantage of not requiring the Hermitian symmetry and DC bias operations to obtain real, positive-valued signals suited for intensity modulation of LEDs. Our results show that the proposed OTFS based schemes perform better than their OFDM counterparts. Finally, to mitigate the effect of channel correlation and achieve improved system performance, we investigate the use of the pairwise coding technique and singular value decomposition precoding in multiple-input multiple-output (MIMO) VLC systems. Our simulation results show that the pairwise coding is effective in alleviating the effect of spatial correlation.
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Shi, Le. "TiO2/Cu2O composite based on TiO2 NTPC photoanode for photoelectrochemical (PEC) water splitting under visible light." Thesis, 2015. http://hdl.handle.net/10754/552893.
Full textAbstract:
Water splitting through photoelectrochemical reaction is widely regarded as a major method to generate H2 , a promising source of renewable energy to deal with the energy crisis faced up to human being. Efficient exploitation of visible light in practice of water splitting with pure TiO2 material, one of the most popular semiconductor material used for photoelectrochemical water splitting, is still challenging. One dimensional TiO2 nanotubes is highly desired with its less recombination with the short distance for charge carrier diffusion and light-scattering properties. This work is based on TiO2 NTPC electrode by the optimized two-step anodization method from our group. A highly crystalized p-type Cu2O layer was deposited by optimized pulse potentiostatic electrochemical deposition onto TiO2 nanotubes to enhance the visible light absorption of a pure p-type TiO2 substrate and to build a p-n junction at the interface to improve the PEC performance. However, because of the real photocurrent of Cu2O is far away from its theoretical limit and also poor stability in the aqueous environment, a design of rGO medium layer was added between TiO2 nanotube and Cu2O layer to enhance the photogenerated electrons and holes separation, extend charge carrier diffusion length (in comparison with those of conventional pure TiO2 or Cu2O materials) which could significantly increase photocurrent
to 0.65 mA/cm2 under visible light illumination (>420 nm) and also largely improve the stability of Cu2O layer, finally lead to an enhancement of water splitting performance.
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Ashok, D. R. "Precoding and Channel Estimation Schemes for MIMO VLC Systems." Thesis, 2019. https://etd.iisc.ac.in/handle/2005/4726.
Full textAbstract:
Increase in the usage of smartphones and growing demand for data have resulted in
congestion in the RF spectrum. To ease the overcrowding of RF spectrum, there is a
need for wireless communication systems that can complement RF based communication
systems. Visible light communication (VLC) is proving to be an attractive alternate for
wireless communications in indoor and vehicular environments. In VLC, light emitting
diodes (LEDs) and photo detectors (PDs) serve as transmitters and receivers, respectively.
Using multiple-input multiple-output (MIMO) techniques is one way to increase
the spectral e ciency. Spatial multiplexing (SMP), spatial modulation (SM), generalized
spatial modulation (GSM), dual-LED complex modulation (DCM), and quad-LED
complex modulation (QCM) are some of the MIMO modulation schemes that are suited
for MIMO VLC. The degrading e ect on the performance of the modulation schemes due
to the presence of high degree of spatial correlation is one of the major issues in MIMO
VLC systems. We consider the use of precoding at the transmitter as a promising approach
to alleviate this issue. Most precoding schemes require channel state information
at the transmitter (CSIT). CSIT is usually obtained by estimating the channel at the
receiver and sending this estimate to the transmitter through feedback. Therefore, the
performance of these precoding schemes depends on the accuracy of channel estimation.
In this thesis, our main focus is on designing precoding schemes and channel estimation
schemes for MIMO VLC systems. Our contributions can be classified into three parts as
follows.
In the first part, we propose two efficient precoding schemes for point-to-point MIMO
VLC systems which employ DCM and QCM schemes. The first proposed precoder is
for DCM, and it is termed as \optimized diagonally precoded DCM" (ODP-DCM).
In ODP-DCM, symbols emitted by the LEDs are weighted such that the normalized
minimum distance of the received signal set is maximized. The second precoder is for
both DCM and QCM, and it is termed as \pseudo-random phase precoded DCM/QCM"
(PRPP-DCM/QCM). In PRPP-DCM/QCM, pseudo-random phase matrices which do
not need any channel knowledge at the transmitter for their construction are used as
the precoding matrices. Numerical results show that the proposed precoding schemes
achieve good performance and alleviate the effeect of spatial correlation in MIMO VLC
channels.
In the second part, we are concerned with precoding in point-to-point and multiuser
MIMO VLC systems under maximum and average power constraints. Average power
constraint is considered to ensure that the LEDs maintain a desired intensity of light
for the purpose of illumination. Maximum power constraint arises due to the maximum
current rating of the LEDs. We propose a weighted precoding scheme for point-to-point
MIMO VLC which uses suitable scaling and DC-biasing to satisfy the aforementioned
power constraints. We also consider the extension of this scheme to multiuser MIMO
VLC using block diagonalization. Results show that SMP and DCM schemes achieve
signi cant improvement in performance by using this precoding technique in both pointto-
point and multiuser MIMO VLC systems.
In the third part, we are concerned with channel estimation in VLC systems under
maximum and average power constraints. In particular, we consider extensions to
combinational codes for optimal pilot transmission assuming that the receiver employs
a zero-forcing decoder. We construct optimal codes which need much fewer pilot channel
uses for channel estimation compared to that needed by combinational codes. We
propose a recursive algorithm to construct such codes that are short in length and meet
the optimality constraints. The bit error performance achieved using the estimates of
the channel obtained using the proposed codes are shown to be quite close to that with
perfect channel knowledge.