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Sánchez, Diana Luis David. "High performance photonic devices for switching applications in silicon photonics." Doctoral thesis, Universitat Politècnica de València, 2017. http://hdl.handle.net/10251/77150.
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El silicio es la plataforma más prometedora para la integración fotónica, asegurando la compatibilidad con los procesos de fabricación CMOS y la producción en masa de dispositivos a bajo coste. Durante las últimas décadas, la tecnología fotónica basada en la plataforma de silicio ha mostrado un gran crecimiento, desarrollando diferentes tipos de dispositivos ópticos de alto rendimiento.
Una de las posibilidades para continuar mejorando las prestaciones de los dispositivos fotónicos es mediante la combinación con otras tecnologías como la plasmónica o con nuevos materiales con propiedades excepcionales y compatibilidad CMOS. Las tecnologías híbridas pueden superar las limitaciones de la tecnología de silicio, dando lugar a nuevos dispositivos capaces de superar las prestaciones de sus homólogos electrónicos. La tecnología híbrida dióxido de vanadio/ silicio permite el desarrollo de dispositivos de altas prestaciones, con gran ancho de banda, mayor velocidad de operación y mayor eficiencia energética con dimensiones de la escala de la longitud de onda.
El objetivo principal de esta tesis ha sido la propuesta y desarrollo de dispositivos fotónicos de altas prestaciones para aplicaciones de conmutación. En este contexto, diferentes estructuras basadas en silicio, tecnología plasmónica y las propiedades sintonizables del dióxido de vanadio han sido investigadas para controlar la polarización de la luz y para desarrollar otras funcionalidades electro-ópticas como la modulación.Silicon is the most promising platform for photonic integration, ensuring CMOS fabrication compatibility and mass production of cost-effective devices. During the last decades, photonic technology based on the Silicon on Insulator (SOI) platform has shown a great evolution, developing different sorts of high performance optical devices. One way to continue improving the performance of photonic optical devices is the combination of the silicon platform with another technologies like plasmonics or CMOS compatible materials with unique properties. Hybrid technologies can overcome the current limits of the silicon technology and develop new devices exceeding the performance metrics of its counterparts electronic devices. The vanadium dioxide/silicon hybrid technology allows the development of new high-performance devices with broadband performance, faster operating speed and energy efficient optical response with wavelength-scale device dimensions. The main goal of this thesis has been the proposal and development of high performance photonic devices for switching applications. In this context, different structures, based on silicon, plasmonics and the tunable properties of vanadium dioxide, have been investigated to control the polarization of light and for enabling other electro-optical functionalities, like optical modulation.
El silici és la plataforma més prometedora per a la integració fotònica, assegurant la compatibilitat amb els processos de fabricació CMOS i la producció en massa de dispositius a baix cost. Durant les últimes dècades, la tecnologia fotònica basada en la plataforma de silici ha mostrat un gran creixement, desenvolupant diferents tipus de dispositius òptics d'alt rendiment. Una de les possibilitats per a continuar millorant el rendiment dels dispositius fotònics és per mitjà de la combinació amb altres tecnologies com la plasmònica o amb nous materials amb propietats excepcionals i compatibilitat CMOS. Les tecnologies híbrides poden superar les limitacions de la tecnologia de silici, donant lloc a nous dispositius capaços de superar el rendiment dels seus homòlegs electrònics. La tecnologia híbrida diòxid de vanadi/silici permet el desenvolupament de dispositius d'alt rendiment, amb gran ample de banda, major velocitat d'operació i major eficiència energètica en l'escala de la longitud d'ona. L'objectiu principal d'esta tesi ha sigut la proposta i desenvolupament de dispositius fotònics d'alt rendiment per a aplicacions de commutació. En este context, diferents estructures basades en silici, tecnologia plasmònica i les propietats sintonitzables del diòxid de vanadi han sigut investigades per a controlar la polarització de la llum i per a desenvolupar altres funcionalitats electró-òptiques com la modulació.
Sánchez Diana, LD. (2016). High performance photonic devices for switching applications in silicon photonics [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/77150
TESIS
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Zhou, Ying. "CHOLESTERIC LIQUID CRYSTAL PHOTONIC CRYSTAL LASERS AND PHOTONIC DEVICES." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2706.
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This dissertation discusses cholesteric liquid crystals (CLCs) and polymers based photonic devices including one-dimensional (1D) photonic crystal lasers and broadband circular polarizers. CLCs showing unique self-organized chiral structures have been widely used in bistable displays, flexible displays, and reflectors. However, the photonic band gap they exhibit opens a new way for generating laser light at the photonic band edge (PBE) or inside the band gap. When doped with an emissive laser dye, cholesteric liquid crystals provide distributed feedback so that mirrorless lasing is hence possible. Due to the limited surface anchoring, the thickness of gain medium and feedback length is tens of micrometers. Therefore lasing efficiency is quite limited and laser beam is highly divergent. To meet the challenges, we demonstrated several new methods to enhance the laser emission while reducing the beam divergence from a cholesteric liquid crystal laser. Enhanced laser emission is demonstrated by incorporating a single external CLC reflector as a polarization conserved reflector. Because the distributed feedback from the active layer is polarization selective, a CLC reflector preserves the original polarization of the reflected light and a further stimulated amplification ensues. As a result of virtually doubled feedback length, the output is dramatically enhanced in the same circular polarization state. Meanwhile, the laser beam divergence is dramatically reduced due to the increased cavity length from micrometer to millimeter scale. Enhanced laser emission is also demonstrated by the in-cell metallic reflector because the active layer is pumped twice. Unlike a CLC reflector, the output from a mirror-reflected CLC laser is linearly polarized as a result of coherent superposition of two orthogonal circular polarization states. The output linear polarization direction can be well controlled and fine tuned by varying the operating temperature and cell gap. Enhanced laser emission is further demonstrated in a hybrid photonic band edge - Fabry-Perot (FP) type structure by sandwiching the CLC active layer within a circular polarized resonator consisting of two CLC reflectors. The resonator generates multiple FP modes while preserving the PBE mode from the active layer. More importantly this band edge mode can be greatly enhanced by the external resonator under some conditions. Theoretical analysis is conducted based on 4×4 transfer matrix and scattering matrix and the results are consistent with our experimental observations. To make the CLC laser more compact and miniaturized, we have developed a flexible polymer laser using dye-doped cholesteric polymeric films. By stacking the mirror reflecting layer, the active layer and the CLC reflecting layer, enhanced laser emission was observed in opposite-handed circular polarization state, because of the light recycling effect. On the other hand, we use the stacked cholesteric liquid crystal films, or the cholesteric liquid crystals and polymer composite films to demonstrate the single film broadband circular polarizers, which are helpful for converting a randomly polarized light into linear polarization. New fabrication methods are proposed and the circular polarizers cover ~280 nm in the visible spectral range. Both theoretical simulation and experimental results are presented with a good match.Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
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Zhou, Yaling. "Photonic Devices Fabricated with Photonic Area Lithographically Mapped Process." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1233528818.
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Forsberg, Erik. "Electronic and Photonic Quantum Devices." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3476.
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In this thesis various subjects at the crossroads of quantummechanics and device physics are treated, spanning from afundamental study on quantum measurements to fabricationtechniques of controlling gates for nanoelectroniccomponents.
Electron waveguide components, i.e. electronic componentswith a size such that the wave nature of the electron dominatesthe device characteristics, are treated both experimentally andtheoretically. On the experimental side, evidence of partialballistic transport at room-temperature has been found anddevices controlled by in-plane Pt/GaAs gates have beenfabricated exhibiting an order of magnitude improvedgate-efficiency as compared to an earlier gate-technology. Onthe theoretical side, a novel numerical method forself-consistent simulations of electron waveguide devices hasbeen developed. The method is unique as it incorporates anenergy resolved charge density calculation allowing for e.g.calculations of electron waveguide devices to which a finitebias is applied. The method has then been used in discussionson the influence of space-charge on gate-control of electronwaveguide Y-branch switches.
Electron waveguides were also used in a proposal for a novelscheme of carrierinjection in low-dimensional semiconductorlasers, a scheme which altogether by- passes the problem ofslow carrier relaxation in suchstructures. By studying aquantum mechanical two-level system serving as a model forelectroabsorption modulators, the ultimate limits of possiblemodulation rates of such modulators have been assessed andfound to largely be determined by the adiabatic response of thesystem. The possibility of using a microwave field to controlRabi oscillations in two-level systems such that a large numberof states can be engineered has also been explored.
A more fundamental study on quantum mechanical measurementshas been done, in which the transition from a classical to aquantum "interaction free" measurement was studied, making aconnection with quantum non-demolition measurements.
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Alonzo, Massimo. "Photonic devices in solitonic waveguides." Phd thesis, Université de Metz, 2010. http://tel.archives-ouvertes.fr/tel-00557947.
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La thèse montre des solutions pour la réalisation de circuits photoniques intégrés utilisant le caractère volumétrique et les très faibles pertes en propagation des solitons spatiaux . On s'intéresse aux élément de base: interconnections, sources et router optique (comme dispositif d'élaboration). Interconnections et sources sont réalisé dans le niobat de lithium (LN) qui fournis des structures avec une très longe durée temporelle. Le fonctionnement d'un router optique est démontré dans le semiconducteur photorefractif (PR) InP:Fe en raison de sa sensitivité aux longueurs d'onde infrarouges (IR) et à son temps de réponse rapide. On montre que les pertes en propagation dans les interconnections solitoniques peuvent être réduites à nouveau en utilisant un faisceau en polarisation ordinaire qui augmente la variation d'indice de réfraction induite. La réalisation de sources intégrées solitoniques est étudié pour avoir émission en bleu à 400nm et en IR à 1530nm. Celles en bleu sont obtenues par génération de deuxième harmonique ; le rôle du bleu pour la formation des solitons est montré et ses propriété physiques étudiées. Celles en IR sont obtenues en dopant le LN avec des ions (actifs) d'erbium. Leurs effets sur les paramètres PR sont présentés et les solitons spatiaux sont obtenus en excitant l'absorption soit du LN soit de l'erbium. L'amplification de la luminescence est étudié numériquement. Le routage optique dans le InP :Fe est obtenu en faisant interagir deux solitons cohérents et en changeant leur phase relative. L'augmentation de la séparation ou leur fusion est analysé en fonctionne de la distance entre eux, température et intensité de la lumière.
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Liu, Tao. "Photonic Crystal Based Optical Devices." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1294%5F1%5Fm.pdf&type=application/pdf.
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Fan, Yun-Hsing. "TUNABLE LIQUID CRYSTAL PHOTONIC DEVICES." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3926.
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Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices and their fabrication methods. The devices presented include inhomogeneous polymer-dispersed liquid crystal (PDLC), polymer network liquid crystals (PNLC) and phase-separated composite film (PSCOF). Liquid crystal/polymer composites could exist in different forms depending on the fabrication conditions. In Chap. 3, we demonstrate a novel nanoscale PDLC device that has inhomogeneous droplet size distribution. In such a PDLC, the inhomogeneous droplet size distribution is obtained by exposing the LC/monomer with a non-uniform ultraviolet (UV) light. An electrically tunable-efficiency Fresnel lens is devised for the first time using nanoscale PDLC. The tunable Fresnel lens is very desirable to eliminate the need of external spatial light modulator. Different gradient profiles are obtained by using different photomasks. The nanoscale LC droplets are randomly distributed within the polymer matrix, so that the devices are polarization independent and exhibit a fast response time. Because of the small droplet sizes, the operating voltage is higher than 100 Vrms. To lower the driving voltage, in Chap. 2 and Chap. 3, we have investigated a polymer-network liquid crystal (PNLC) using a rod-like monomer structure. Since the monomer concentration is only about 5%, the operating voltage is below 10 Vrms. The PNLC devices are polarization dependent. To overcome this shortcoming, stacking two cells with orthogonal alignment directions is a possibility. In Chap. 3, another approach to lower the operating voltage is to use phase-separated composite film (PSCOF) where the LC and polymer are separated completely to form two layers. Without multi-domain formed in the LC cell, PSCOF is free from light scattering. Using PNLC and PSCOF, we also demonstrated LC blazed grating and Fresnel lens. The diffraction efficiency of these devices is continuously controlled by the electric field. Besides Fresnel lens, another critical need for imaging and display is to develop a system with continuously tunable focal length. A conventional zooming system controls the lens distance by mechanical motion along the optical axis. This mechanical zooming system is bulky and power hungry. To overcome the bulkiness, in Chap. 4 we developed an electrically tunable-focus flat LC spherical lens which consists of a spherical electrode imbedded in the top flat substrates while a planar electrode on the bottom substrate. The electric field from the spherical and planar electrodes induces a centrosymmetric gradient refractive index distribution within the LC layer which, in turn, causes the focusing effect. The focal length is tunable by the applied voltage. A tunable range from 0.6 m to infinity is achieved. Microlens array is an attractive device for optical communications and projection displays. In Chap. 5, we describe a LC microlens array whose focal length can be switched from positive to negative or vise versa by the applied voltage. The top spherical electrode glass substrate is flattened with a polymer layer. The top convex substrate and LC layer work together like a zoom lens. By tuning the refractive index profile of the LC layer, the focal length of the microlens array can be switched from positive to negative or vise versa. The tunable LC microlens array would be a great replacement of a conventional microlens array which can be moved by mechanical elements. The fast response time feature of our LC microlens array will be very helpful in developing 3-D animated images. A special feature for LC/polymer composites is light scattering. The concept is analogous to the light scattering of clouds which consist of water droplets. In Chap. 6, we demonstrate polymer network liquid crystals for switchable polarizers and optical shutters. The PNLC can present anisotropic or isotropic light scattering behavior depending on the fabrication methods. The use of dual-frequency liquid crystal and special driving scheme leads to a sub-millisecond response time. The applications for display, light shutters, and switchable windows are emphasized. Although polymer networks help to reduce liquid crystal response time, they tend to scatter light. In Chap. 7, for the first time, we demonstrate a fast-response and scattering-free homogeneously-aligned PNLC light modulator. Light scattering in the near-infrared region is suppressed by optimizing the polymer concentration such that the network domain sizes are smaller than the wavelength. As a result, the PNLC response time is ~300X faster than that of a pure LC mixture except that the threshold voltage is increased by ~25X. The PNLC cell also holds promise for mid and long infrared applications where response time is a critical issue.Ph.D.
Other
Optics and Photonics
Optics
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Scardaci, Vittorio. "Carbon nanotubes for photonic devices." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612536.
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Gallacher, Kevin. "Germanium on silicon photonic devices." Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4994/.
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There is presently increased interest in using germanium (Ge) for both electronic and optical devices on top of silicon (Si) substrates to expand the functionality of Si technology. It has been extremely difficult to form an Ohmic contact to n-Ge due to Fermi level pinning just above the Valence band. A low temperature nickel process has been developed that produces Ohmic contacts to n-Ge with a specific contact resistivity of , which to date is a record. The low contact resistivity is attributed to the low resistivity NiGe phase, which was identified using electron diffraction in a transmission electron microscope. Light emission from Ge light emitting diodes (LEDs) was investigated. Ge is an indirect bandgap semiconductor but the difference in energy between the direct and indirect is small (~136 meV), through a combination of n-type doping and tensile strain, the band structure can be engineered to produce a more direct bandgap material. A silicon nitride (Si3N4) process has been developed that imparts tensile strain into the Ge. The stress in the Si3N4 film can be controlled by the RF power used during the plasma enhanced chemical vapour deposition. LEDs covered with Si3N4 stressors were characterised by Fourier transform infrared spectroscopy. Electroluminescence characterisation (EL) revealed that the peak position of the direct and indirect radiative transitions did not vary with the Si3N4 stressors due to the device geometries being too large. Therefore, nanostructures consisting of pillars smaller than a micron were investigated. Photoluminescence characterisation of 100 nm Ge pillars with Si3N4 stressors show emission at much longer wavelengths compared to bulk Ge (> 2.2 μm). In addition, the EL from Ge quantum wells grown on Si was also investigated. EL characterisation demonstrates two peaks around 1.55 and 1.8 μm, which corresponds to the radiative recombination between the direct and indirect transitions, respectively. This result is the first demonstration of EL above 1.45 μm for Ge quantum wells. Finally, the fabrication of Ge-on-Si single-photon avalanche detectors are presented. A single-photon detection efficiency of 4 % at 1310 nm wavelength was measured at low temperature (100 K). The devices have the lowest reported noise equivalent power for a Ge-on-Si single-photon avalanche detector (1×10-14 WHz-1/2).
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Raghunathan, Varun. "Raman-based silicon photonic devices." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1481677321&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Wang, Jing. "Fabrication and Characterization of Photonic Crystals, Optical Metamaterials and Plasmonic Devices." Doctoral thesis, KTH, Fotonik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33600.
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Nanophotonics is an emerging research field that deals with interaction between light and matter in a sub-micron length scale. Nanophotonic devices have found an increasing number of applications in many areas including optical communication, microscopy, sensing, and solar energy harvesting especially during the past two decades. Among all nanophotonic devices, three main areas, namely photonic crystals, optical metamaterials and plasmonic devices, gain dominant interest in the photonic society owning to their potential impacts. This thesis studies the fabrication and characterization of three types of novel devices within the above-mentioned areas. They are respectively photonic-crystal (PhC) surface-mode microcavities, optical metamaterial absorbers, and plasmonic couplers. The devices are fabricated with modern lithography-based techniques in a clean room environment. This thesis particularly describes the critical electron-beam lithography step in detail; the relevant obstacles and corresponding solutions are addressed. Device characterizations mainly rely on two techniques: a vertical fiber coupling system and a home-made optical transmissivity/reflectivity setup. The vertical fiber coupling system is used for characterizing on-chip devices intended for photonic integrations, such as PhC surface-mode cavities and plasmonic couplers. The transmissivity/reflectivity setup is used for measuring the absorbance of metamaterial absorbers. This thesis presents mainly three nanophotonic devices, from fabrication to characterization. First, a PhC surface-mode cavity on a SOI structure is demonstrated. Through a side-coupling scheme, a system quality-factor of 6200 and an intrinsic quality-factor of 13400 are achieved. Such a cavity can be used as ultra-compact optical filter, bio-sensor and etc. Second, an ultra-thin, wide-angle metamaterial absorber at optical frequencies is realized. Experimental results show a maximum absorption peak of 88% at the wavelength of ~1.58μm. The ultra-fast photothermal effect possessed by such noble-metal-based nanostructure can potentially be exploited for making better solar cells. Finally, we fabricated an efficient coupler that channels light from a conventional dielectric waveguide to a subwavelength plasmonic waveguides and vice versa. Such couplers can combine low-loss dielectric waveguides and lossy plasmonic components onto one single chip, making best use of the two.QC 20110524
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Boertjes, David Weldon. "Passive and electrooptic polymer photonic devices." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0002/NQ39506.pdf.
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Hua, Yan. "Development of photonic-based measurement devices." Thesis, University of Salford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308172.
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DEMENICIS, LUCIENE DA SILVA. "DEVELOPMENT AND CHARACTERIZATION OF PHOTONIC DEVICES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1996. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8844@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORPolimeros orgânicos de natureza conjugada têm despertado bastante interessante como materiais ópticos não-lineares por serem extremamente promissores para o desenvolvimento de dispositivos fotônicos, como por exemplo dispositivos de comunicações. Além de possuírem resposta óptica não - linear intensa e rápida, seu modo de preparação e sua forma final apresentam grande flexibilidade. Do ponto de vista de aplicação, os parâmetros do material mais importantes são : a susceptibilidade não-linear de terceira ordem (x (3)) cuja parte real está relacionada com o índice de refração não-linear e a parte imaginária relacionada com o coeficiente de absorção não-linear; o tempo de resposta; o coeficiente de absorção linear no comprimento de onda de operação (alfa L); a capacidade de processamento; o limiar de dano e a estabilidade térmica. Dentre os polímeros conjugados, destaca-se a família dos politiofenos, compostos heterocíclicos de elevada estabilidade, que exibem interessantes propriedades de transporte e acentuada não-linearidade de terceira ordem. Neste trabalho as propriedades ópticas do politiofeno: X (3), partes real e imaginária; alfaL; e tempo de resposta, foram investigadas experimentalmente. A técnica utilizada para medida dos efeitos não-lineares de terceira ordem foi a técnica de Z-scan convencional. Os valores absolutos e s sinais do índice de refração não - linear e do coeficiente de absorção não-linear foram encontrados como sendo da ordem de - 10 -12 cm 2/W e - 10 - 8 cm/W, respectivamente. Para analisar os resultados experimentais foi necessário utilizar um tratamento teórico relativamente novo. Esta abordagem teórica é diferente da convencional e fornece resultados satisfatórios que descrevem bem os resultados experimentais. O tempo de resposta da não-linearidade do politiofeno foi obtido com a técnica de Z-scan resolvida no tempo, utilizando um único comprimento de onda e polarizações cruzadas. O valor obtido foi inferior à 100 os. Além de caracterizar o politiofeno, foi também demonstrada a utilização dexte polímero comoporta lógica E (AND)m através de uma medida envolvendo chaveamento Kerr. Este experimento mostrou que é possível realizar um chaveamento total óptico onde um feixe de luz é controlado por um outro feixe de luz, com duração de algumas dezenas de picossegundos.
Conjugated organic polymers are of wide interest as nonlinear optical materials because of their potential applications in photonic devices, such as communication devices. They have a large and fast nonlinear optical response, as well as a great flexibility in their preparing method. For device applications, the most important parameters are: third-order optical nonlinear susceptibility X(3), which real part is related with nonlinear refractive index and imaginary part is related with nonlinear absorption coefficient; response time; absorptioon at operating wavelength alfaL; processability; damage threshold; and thermal stability. There are many conjugated polymers, and the polythiophene class, which includes high stabilityn heterocyclic compunds, is one of the most impoant because of its interesting transport properties and large third-order nonlinearity. In this work the optical properties of polythiophene: X (3), real and imaginary parts; alfaL and time response, were investigated experimentally. The Z-scan technique was used to measure the third-order nonlinear effects. The value and the sign of the nonlinear refractive index and nonlinear absorption coefficient of the polythiophene were found to be around -10 -12cm2/W and -10-8 cm/W, respectively. To analyze the experimental data it wass necessary to use a new theoretical approach. This approach is different from the conventional one and produces better fitting of the experimental results. The nonlinear response time of the polythiophene was measured using the time-resolved Z-scan technique, using a single waveguide and perpendicular polarizations. The time response is smaller than 100 ps. Besides the polythiophene characterization, it was demonstrated that this polymer can work like an AND logical gate using Kerr switching. This wxperiment showed that it is possible to make a fast (picoseconds) all- optical switch using a light beam to control another light beam.
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Psaila, Nicholas David. "Photonic devices for integrated optical applications." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2325.
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work presented in this thesis encompasses an investigation into the use of ultrafast laser inscription in the fabrication of glass based photonic devices for integrated optical applications. Waveguide fabrication and characterisation experiments were carried out in three categories of glass substrate. Firstly, waveguides were inscribed in an erbium doped glass with the aim of fabricating optical amplifiers and lasers operating in the 1.5 μm spectral region. Low loss waveguides were fabricated in substrates with different dopant concentrations. Fibre to fibre net gain was achieved from one substrate composition, however it was found that ion clustering limited the amount of achievable gain. Laser action was demonstrated by constructing an optical fibre based cavity around the erbium doped waveguide amplifier. Waveguides were also inscribed in bismuth doped glass with the aim of fabricating optical amplifiers and lasers operating in the 1.3 μm spectral region. Low loss waveguides were fabricated, however the initial composition was incapable of providing gain. A proven substrate material was employed, demonstrating ultra-broadband gain spanning more than 250 nm. High losses prevented the achievement of net gain, however the broad potential of the substrate material was highlighted. Finally, waveguides were inscribed in a Chalcogenide glass. Strong refractive index contrasts were observed, with a wide range of waveguiding structures produced. Supercontinuum experiments were carried out in order to confirm the nonlinear behaviour of the waveguides. A spectrally smooth supercontinuum spanning 600 nm was generated, providing a potentially useful source for optical coherence tomography.
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Klitis, Charalambos. "Polarisation selective integrated silicon photonic devices." Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/8725/.
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The main objective of this thesis was the development of polarisation selective gratings in silicon-on-insulator (SOI) technology. These devices can find numerous applications in the design of highly performing optical filters and, more in general, in all those devices that require on-chip manipulation of the polarisation state. The development of these devices was preceded by the optimisation of several fabrication processes, such as lithography and dry etching, and the re-design of a number of key components such as inverse polymer tapers and metallic heaters for thermal tuning. This activity culminated into a very robust process flow for SOI devices, with repeatable propagation losses in the order of 1 dB/cm, heaters with a very high tuning efficiency of 12 mW per π phase shift and 2dB and 1dB waveguide-to-optical fibre coupling losses for the TE and TM polarised mode, respectively. The grating designs developed in this thesis consisted of periodic holes etched onto the top surface of the silicon optical waveguide. Such geometry overlaps strongly with the TM polarised mode only and does not introduce additional losses to the TE mode. The benefit and the additional functionalities provided by the top grating geometry was assessed on two different polarisation sensitive devices. The first consisted in a microring resonator with integrated gratings for the emission of optical vortex beams, for which the top gratings provided a route to engineer the polarisation state of the emitted beam. The second device was a Bragg grating filter, where the top grating allowed the demonstration of extinction ratio values as high as 60dB by filtering the residual TM mode generated by the strong polarisation scattering.
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Andreakou, Peristera. "Hybrid nanomaterials for novel photonic devices." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/347152/.
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This PhD thesis investigates the optical properties of colloidal semiconductor nanocrystals and evaluates concepts regarding the development of novel photonic devices. Spectroscopic studies of the exciton dynamics in colloidal lead sulfide (PbS) quantum dots (QDs) by tuning the temperature are presented. The lowest exciton splitting for a range of PbS QDs sizes is calculated and a transfer of the oscillator strength from dark to bright states as the size increases is demonstrated. Hybrid structures with PbS QDs deposited on silicon substrates were also studied in order to explore whether excitons can be created in this material by means of resonant energy transfer. Furthermore, elongated asymmetric cadmium selenide/cadmium sulfide (CdSe/CdS) quantum rods are used as gain medium for the development of whispering gallery mode microlasers. Single-mode operation of hybrid lasers based on colloidal CdSe/CdS core/shell QRs in silica microspheres is for the first time reported. Laser-emission tunability over a range of 2.1 nm is also demonstrated, by heating the microsphere cavity with a 3.5-μm laser. In the last part of this thesis, unstructured and micro structured LiNbO3 are presented as excellent substrates for cell culture. Two commonly used neuron-like cells have been successfully proliferated and differentiated on both polar (±z) faces of LiNbO3 crystal substrates. Spatially selective attachment of neuron-like cells onto the domain engineered micro-structured substrates is also shown, providing the opportunity for the development of functional materials for the study of neuronal networks.
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Li, Huanlu. "Integrated photonic devices for data communications." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682683.
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With the increasing capacity requirements of telecommunication systems, the ability to increase capacity density is of great importance for optical transmission technologies. This thesis presents several integrated photonic devices (semiconductor laser diodes and silicon devices) aimed at boosting the capacity density of the optical transmission systems. The first part of the thesis is about four wave mixing (FWM) effects in semiconductor ring lasers. Mode beating via third order nonlinearity in semiconductor ring lasers has been analysed using a frequency-domain multi-mode rate equation model. Compared with Fabry-Perot lasers, semiconductor ring lasers are found to be 1.33, 2, and 4 times more efficient in self-gain compression, cross-gain compression and four-wave mixing processes, respectively, due to its travelling-wave nature. It is shown that, using dual (pump and signal) external optical injections into the ring laser cavity, multiple modes can be locked in phase via the strong four wave mixing phenomenon. This results in modulation of the light wave at the mode beating frequencies which could be used for RF optical catrier generation. Secondly, following Bristol's research on compact optical vortex beam emitter based on silicon photonic micro-ring resonators, a different approach is demonstrated to simultaneously generate a pair of orbital angular momentum (OAM) modes with opposite topological charge by integrating a micro-ring OAM resonator with simple waveguide devices. The relative phase between two vortices can be actively modulated on the chip by thermo-optical controls. Furthermore, based on the ring cavity structure, OAM ring lasers on AlGaInAs/InP wafer are also developed. Detailed designs, fabrication processes and characterization of the device are discussed. In the last part of the thesis, a new approach is to propose and demonstrate directly generated optical OAM beams, by integrating a micro-scale spiral phase plate (SPP) on top of a vertical-cavity surface-emitting laser (VCSEL). The presence of the multi-level SPP transforms the linearly polarized Gaussian beam to a beam carrying specific OAM modes and their superposition states. The emitted OAM beams are characterized by usmg a spatial light modulator (SLM), and show good agreement with semi-analytical numerical simulation. The innovative OAM emitter opens a new horizon in the field of OAM-based optical and quantum communications, especially for low-cost short reach interconnects.
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Liu, Hangyu. "Diamond processing for advanced photonic devices." Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28405.
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Diamond photonic devices are critical components for applications including diamond based optics, diamond Raman lasers and the building blocks of quantum information processing. In this thesis work, to achieve such novel diamond photonic devices, micro-fabrication techniques for diamond have been further developed. For making diamond optical structures such as diamond micro-lenses, the fabrication involves the definition of photoresist (PR) masks on the surface of diamond by using photolithography and the pattern transfer by using inductively coupled plasma (ICP) etching. A detailed study of the PR thermal reflow process has been carried out to control the shape of PR masks and the resulting diamond structures with spherical or aspheric features after pattern transfer. By combining PR mask shape control with the optimisation of ICP diamond etching, novel micro-lenses on single crystal diamond have been realised. In particular, diamond micro-lenses with radii of curvature larger than 13 mm have been fabricated. Based on these diamond micro-lenses, novel monolithic diamond Raman lasers were achieved. Furthermore, by using Ar/Cl2 plasma etching, a large area ultra-thin single crystal diamond membrane with a thickness less than 250 nm has been produced. By coupling the diamond membrane within an open optical Fabry-Perot cavity, the enhanced emission from the nitrogen vacancy (NV) colour centre in diamond was investigated. This approach is attractive for the scalable development of quantum computing based on diamond NV centres.
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Zhang, Ziyang. "Silicon-based Photonic Devices : Design, Fabrication and Characterization." Doctoral thesis, Stockholm : Mikroelektronik och tillämpad fysik, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4647.
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MAINI, LUCA. "Metamaterials based on photonic quasicrystals: from superlensing to new photonic devices." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2010. http://hdl.handle.net/10281/18116.
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In this Ph.D thesis we verified that metamaterials based on photonic quasicrystals
can have superlensing properties and that the same type of material, in
a different configuration, is able to localize photons and thus suggests
the possibility to build new photonic devices, namely optomechanical
switches.
We saw that a slab cut from a two dimensional 12-fold quasicrystalline
tiling constitutes a metamaterial because of its effective refactive
index that becomes negative in some frequency ranges. These regions of
the spectrum where negative refraction and superlensing occurr can be
found with the help of computational methods that calculate dispersion
curves, equifrequency surfaces and electromagnetic field distribution of
the system under study. In the particular case of quasicrystals, where the
lack of translational symmetry forces to use big supercells, the amount
of data and information contained in the dispersion curves and equifrequency
surfaces is very dense and sometimes difficult to disentangle,
suggesting particular care when predicting the behaviour of the physical
system without the experimental counterpart.
Examiming the electromagnetic field patterns of the quasicrystalline
slab we found that several modes could be useful for cloaking, since they
do not propagate in the whole structure but they are inhibited to go
through certain regions, that remain hidden at particular frequencies.
We think that other configurations of this kind of metamaterial give
rise to interesting physical properties, more easily predictable, that can
lead to the realization of new photonic devices. If we place two 12-fold
quasicrystalline slabs together, separated by a vacuum layer of a precise
thickness, we obtain the right conditions to localize photons between
the two slabs. The localization takes place between two indentations of
the slabs’ surfaces, that are a kind of intrinsic defects formed when the
surface are created from the bigger quasicrystalline lattice. This type of
defects is unique to quasicrystalline systems and originates from their lack of translational periodicity. The capability of localizing photons
opens up the possibility of building devices exploiting this feature: for
instance, we could realize a photonic switch with two states, one where
the photon is localized and the other where the photon propagates, and
as we discussed, the choice between these two states can be made only
varying the distance between the two slabs.
This double slab system seems to be exploitable for cloaking too,
since we saw that point defects in the lattice, characterized by a different
dielectric constant, do not affect the localization properties of the device.
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Wang, Ying. "Integrated photonic devices using self-assembled and optically defined photonic crystal superstructures." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3288723.
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Lawson, Llewellyn Rhys. "Hybrid silicon-organic ring resonator photonic devices /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/11542.
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Li, Qiang. "Silicon Based Photonic Devices and Their Applications." Doctoral thesis, KTH, Fotonik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-31290.
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The integration of modern electronic devices for information processing is rapidly ap-proaching an interconnect bottleneck. Silicon photonics can be a promising solution forcircumventing this bottleneck, as already being anticipated by many electronics manu-facturers including HP, IBM and Intel. In particular, optical interconnects can expeditedata transfer both between and within microchips. This thesis aims at two basic buildingblocks of silicon photonics: waveguides and resonators and addresses their applications inoptical signal processing and their potential integration with plasmonic devices. Firstly, the basic theories of waveguide and resonator are introduced. For a singleresonator which acts as a basic signal processing unit, the transmission, phase shift andgroup delay exhibit unique characteristics. Mode splitting is observed in both a singleresonator and a coupled-resonator system. By tuning the configuration of the coupled-resonator system, one can obtain different transmission characteristics for more advancedsignal processing. Secondly, the fabrication and characterization of silicon waveguides and resonatorsused in the thesis are introduced. The fabrication is carried out with e-beam lithographyfollowed by inductively coupled plasma etching. A vertical grating coupling method isadopted to characterize the transmission spectrum. Thirdly, based on a single-ring resonator, three kinds of signal processing are ex-perimentally demonstrated: (1) 10 Gb/s format conversion from non-return-to-zero toalternate-mark-inversion signal; (2) a microwave photonic phase shifter providing a tun-able phase shift of 0–4.6 rad for a 20 GHz signal; (3) a delay line providing maximaldelay times of 80 ps, 95 ps, 110 ps and 65 ps, respectively, for signals in return-to-zero,carrier-suppressed return-to-zero, return-to-zero duobinary, and return-to-zero alternate-mark-inversion formats. Fourthly, based on a single-ring resonator with mode-splitting, two kinds of signalprocessing are experimentally demonstrated: (1) a dense wavelength conversion using thefree carrier dispersion effect with a data rate ranging from 500 Mb/s to 5 Gb/s; (2) amaximum pulse advancement of 130 ps for a 1 ns signal pulse. Since silicon photonic devices are limited by diffraction limit, we further look intotheir hybridization with the diffraction-limit-free plasmonic devices. Two directional cou-plers from a Si photonic waveguide to a hybrid Si-metal plasmonic waveguide and to ametal-insulator-metal plasmonic waveguide are investigated. The proposed hybrid cou-plers feature a short coupling length, a high coupling efficiency, a high extinction ratioand a low insertion loss.QC 20110315
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Zhu, Weiming. "Photonic micromachined devices : design, fabrication and experiment." Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00596905.
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In this PhD project, three different approaches have been studied for tunable photonic devices based on MEMS technology. First, the optical double barrier structure has been numerically studied and experimentally demonstrated as the thermo-optical switch, switchable polarizer and optical tunneling junctions integrated as reconfigurable WDM system. Second, the slow light structure using metamaterial with coupled split ring unit cells is numerically analyzed. Finally, a tunable magnetic metamaterial is demonstrated using MEMS technology. The first major work is to use the optical tunneling effects to design MEMS based photonic devices. Three different tunable photonic devices has been demonstrated using thermo-optical tuning. a thermo-optic switch is realized using MEMS technology. The device is fabricated on silicon-on-isolator wafer using deep etching process. The transmission of the optical switch is controlled by the optical length of the central rib which is thermally controlled by the external pumping current. In experiment, it measures a switching speed of 1 us and an extinction ratio of 30 dB. A switchable polarizer is demonstrated using the double optical barrier structure which transmit the light with one polarization state and filter out the others. In experiment it measures a PER of lager than 23 dB when the pumping current is above 60mA. The switching time is shorter than 125 us which is limited by the polarization analyzer used in the experiment. A MEMS reconfigurable add-drop multiplexer is realized by applied the optical tunneling structure to the ribbed waveguide. The tunable add-drop multiplexer is based on Y-shape optical double barriers tunneling junction which are realized by MEMS technology
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Xu, Su. "Optical Fluid-based Photonic and Display Devices." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5585.
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Conventional solid-state photonic devices exhibit an ultra-high optical performance and durability, but minimal adaptability. Recently, optical fluid-based photonic and display devices are emerging. By dynamically manipulating the optical interface formed by liquids, the optical output can be reconfigured or adaptively tuned in real time. Such devices exhibit some unique characteristics that are not achievable in conventional solid-state photonic devices. Therefore, they open a gateway for new applications, such as image and signal processing, optical communication, sensing, and lab-on-a-chip, etc. Different operation principles of optical fluid-based photonic devices have been proposed, for instance fluidic pressure, electrochemistry, thermal effect, environmentally adaptive hydrogel, electro-wetting and dielectrophoresis. In this dissertation, several novel optical fluid-based photonic and display devices are demonstrated. Their working principles are described and electro-optic properties investigated. The first part involves photonic devices based on fluidic pressure. Here, we present a membrane-encapsulated liquid lens actuated by a photo-activated polymer. This approach paves a way to achieve non-mechanical driving and easy integration with other photonic devices. Next, we develop a mechanical-wetting lens for visible and short-wavelength infrared applications. Such a device concept can be extended to longer wavelength if proper liquids are employed. In the second part, we reveal some new photonic and display devices based on dielectrophoretic effects. We conceive a dielectric liquid microlens with well-shaped electrode for fixing the droplet position and lowering the operating voltage. To widen the dynamic range, we demonstrate an approach to enable focus tuning from negative to positive or vice versa in a single dielectric lens without any moving part. The possibility of fabricating microlens arrays with different aperture and density using a simple method is also proposed. Furthermore, the fundamental electro-optic characteristics of dielectric liquid droplets are studied from the aspects of operating voltage, frequency and droplet size. In addition to dielectric liquid lenses, we also demonstrate some new optical switches based on dielectrophoretic effect, e.g., optical switch based on voltage-stretchable liquid crystal droplet, variable aperture or position-shifting droplet. These devices work well in the visible and near infrared spectral ranges. We also extend this approach to display and show a polarizer-free and color filter-free display. Simple fabrication, low power consumption, polarization independence, relatively low operating voltage as well as reasonably fast switching time are their key features.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
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Gnan, Marco. "Photonic wire devices in silicon-on-insulator." Thesis, University of Glasgow, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443405.
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Namiq, Medya Fouad Namiq. "Photonic microfibre devices based on carbon nanotubes." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/419479/.
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Photonic fibre devices based on the interaction of evanescent fields with materials possessing high Kerr nonlinearity such as carbon nanotubes are promising as an efficient, low loss and low cost devices to be employed in all-optical system applications. Specifically, this report encompasses the work toward addressing the basic key parameters to design and fabricate sufficient all-optical fibre devices based on coated CNTs. Thus, the fundamental concepts of optical fibres; fibre Bragg gratings (FBG), Optical nonlinear (ONL) properties and their effects, CNTs characteristics have been explored. Experimentally, an etch method by utilizing HF acid has been proposed to reduce cladding diameter of the optical fibre and to extend the overlapped evanescent waves to the outer-cladding, thus gaining an efficient interaction with the nonlinear effect of CNTs. And we probed a numerical model for SMF-28 fibre to estimate the fraction of evanescent field coupling within outer-cladding. In addition, real-time monitoring of etching process for both standard fibre SMF-28 and uniform FBG have been applied to demonstrate the influence of etching cladding diameter on the insertion loss of both fibre simultaneously. An optical deposition technique has been proposed to fabricate all-optical fibre devices by CNTs dispersed in DMF solution to be coated on the etched fibre. Moreover, Four wave mixing (FWM) has been performed experimentally and numerically to optimize the fabricated devices. A numerical study has been propped for the effective nonlinear coefficient of the fabricated all-optical fibre devices where it reported on interested results. With the purpose of controlling the losses, the extended fraction of the evanescent field in the etched optical fibre, a simple technique based on measuring, in-situ, the differential relative shifts of the Bragg resonances between the fundamental mode LP01 and the higher-order modes; LP11, LP02, LP21, LP12, LP31 in an etched FBG with accuracy precision ~0.2μm. Furthermore, we determine the refractive index of buffered Hydrofluoric (BHF) acid to be 1.36± 0.005 at 1.55μm. The experimental results were compared with simulations and exhibited excellent agreement. Adding to that, we applied this technique experimentally as a sensor for detecting the change of water salinity and as detector of thermal change based on the relative shifts of between the LP01 and first higher-order mode LP11. This it came matched with the simulations results. A Bragg wavelength shift has been observed about 3.3nm from complete etched cladding of the FBG and has been confirmed simultaneously. In additional work, for thinned FBG the evanescent field of the propagating mode within outer-cladding and the effect of surrounding refractive index on effective refractive index, Bragg wavelength shift for LP01, LP02 and LP03 have been simulated.
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Mittal, Vinita. "Mid-infrared integrated photonic devices for biosensing." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/416430/.
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This thesis describes the realisation of devices and techniques based on evanescent field sensing using planar optical waveguides for mid-infrared (MIR) absorption spectroscopy, to provide bio-chemical sensing capabilities for medical diagnostics. The fundamental vibrations of bio-chemical molecules occur in the MIR region, where their absorption is orders of magnitude stronger than their overtone bands in the near-infrared making it suitable for highly sensitive and specific absorption spectroscopy. Realisation of waveguides is an essential step towards mass-producible and low-cost integrated lab-on-chip devices. Two chalcogenide compositions were used to make waveguides, germanium telluride (GeTe4) as waveguide core and zinc selenide (ZnSe) as waveguide lower cladding. Two approaches were followed for waveguide fabrication: GeTe4 waveguides on bulk ZnSe and GeTe4 waveguides on thin films ZnSe deposited on Si. High contrast (Δn ~ 0.9) GeTe4 channel waveguides on ZnSe were fabricated using photolithography and lift-off. Waveguiding was demonstrated for the wavelength range between 2.5 and 9.5 μm for GeTe4 channel waveguides on bulk ZnSe substrates. GeTe4 waveguides fabricated on Si with ZnSe isolation layers were characterised for waveguiding and propagation losses in the wavelength range between 2.5 and 3.7 μm. ZnSe rib waveguides were also fabricated on oxidised Si by photolithography and dry etching and were characterised for propagation losses in the wavelength region of 2.5-3.7 μm. Absorption spectroscopy of liquid mixtures absorbing in the MIR was performed on the surface of the waveguide and the results were compared with a theoretical model.
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Dorjgotov, Enkh-Amgalan. "Tunable Liquid Crystal Etalon and Photonic Devices." Kent State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=kent1278035084.
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Sevison, Gary Alan. "Silicon Compatible Short-Wave Infrared Photonic Devices." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1523553057993197.
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Fry, Daniel J. "Multimode quantum interference in integrated photonic devices." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.685350.
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This thesis contains experimental and theoretical work based on pair-photon interference in integrated photonic devices. Multimode interference (MMI) devices fabricated with silicon oxynitride technology are used to experimentally demonstrate high visibility pair-photon Hong-Ou-Mandel (HOM) interference. A theoretical model of pair-photon interference is derived for the self-imaging multimode interference that occurs between guided modes in the MMI device , and the scalability of MMI devices for use in quantum photonic networks is considered by modelling serially concatenated devices for decoherent intermodal dispersion effects.
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Rahachou, Aliaksandr. "Theoretical studies of light propagation in photonic and plasmonic devices." Doctoral thesis, Norrköping : Department of Science and Technology, Linköpings universitet, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9585.
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Cross, Jeffrey Brian. "Alignment tolerant smart photonic optical interconnects." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/15756.
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Askari, Murtaza. "High efficiency devices based on slow light in photonic crystals." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39558.
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Photonic crystals have allowed unprecedented control of light and have allowed bringing new functionalities on chip. Photonic crystal waveguides (PCWs), which are linear defects in a photonic crystal, have unique features that distinguish these waveguides from other waveguides. The unique features include very large dispersion, existence of slow light, and the possibility of tailoring the dispersion properties for guiding light. In my research, I have overcome some of the challenges in using slow light in PCWs. In this work, I have demonstrated (i) high efficiency coupling of light into slow group velocity modes of a PCW, (ii) large bandwidth high transmission and low dispersion bends in PCWs, (iii) accurate modeling of pulse propagation in PCWs, (iv) high efficiency absorbing boundary conditions for dispersive slow group velocity modes of PCWs. To demonstrate the utility of slow light in designing high efficiency devices, I have demonstrated refractive index sensors using slow light in PCWs. In the end, a few high efficiency devices based on slow light in PCWs are mentioned. The remaining issues in the widespread use of PCW are also discussed in the last chapter.
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Kutluer, Kutlu. "Quantum memory protocols for photonic solid-state devices." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/461494.
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A photonic quantum memory (QM) is a device that has the capability of storing a quantum state of light and retrieving back after a controlled time. It is an important element in quantum information science and is, among other applications, a crucial device for quantum repeater architectures which have been proposed to overcome the loss and the decoherence issues in long distance transmission of photons. Rare earth ion doped solid state systems are promising candidates for QMs which combine the advantages of solid state systems, such as scalability and reduced experimental complexity, with the long coherence time typically found in atomic systems. In this thesis, I investigated three different QM protocols in a Pr3+:Y2SiO5 crystal.
The first part describes here the first demonstration of the spectral hole memory (SHoMe) protocol which was proposed theoretically in 2009. This protocol relies on slowing down the light in a long-lived spectral hole and transferring the excitations to the spin state. We first prepare a spectral hole, then send an input pulse whose bandwidth is comparable with the hole and stop the compressed light in the crystal by transferring the off-resonant coherence to the spin state with an optical p pulse. Later a second p pulse transfers the coherence back and leads to the emission of the stored light. We reached a storage and retrieval efficiency of around 40% in the classical regime, and of 31% in the single photon level, with a signal-to-noise ratio of 33 ± 4 for a mean input photon number of 1. These results demonstrate the most efficient and noiseless spin-wave solid-state optical memory at the single photon level to date.
The second part of the thesis describes new experiments using the well-known atomic frequency comb (AFC) protocol. It is based on tailoring the inhomogeneously broadened absorption profile of the rare earth with periodic absorptive peaks, which induces the re-emission of the absorbed light field after a certain time determined by the separation between the peaks. In this chapter I describe several AFC experiments. First I present the storage of frequency converted telecom photons into our crystal where we obtained a total efficiency of 1.9 ± 0.2 % for a storage time of 1.6 µs storage time and signal-to-noise ratio of more than 200 for a mean input photon number of 1. Then I discuss the results of improved excited state storage efficiency values for long storage times where we achieved 30% at short storage times and up to 17% at 10 µs storage time. And finally I present a spin-wave AFC experiment where we obtained a signal-to-noise ratio value of 28 ± 8 for a mean input photon number of 1, the highest value achieved so far for this kind of experiment.
Finally, in the last part, I describe the first demonstration of a solid-state photon pair source with embedded multimode quantum memory. The aim of the protocol is to combine a single photon source and a QM in one ensemble as in the well-known Duan-Lukin-Zoller-Cirac (DLCZ) scheme however this time not in a cold atomic ensemble but in a solid-state crystal.
The protocol takes advantage of the AFC protocol for rephasing the ions and obtaining efficient read-out. The use of AFC also makes the protocol temporally multi-mode. In the experiment, after the AFC preparation we send an on-resonant write pulse and detect the decayed Stokes photons which herald single spin excitations. At a later time a read pulse transfers the spin excitation back to the excited state and we detect the anti-Stokes photons. We show strong non-classical second order cross-correlations between the Stokes and anti-Stokes photons and demonstrate storage of 11 temporal modes.
The results presented in this thesis represent a significant contribution to the field of solid-state quantum memories and an important steps towards the realization of scalable quantum network architectures with solid state systems.Una memòria quàntica (MQ) és un dispositiu que té la capacitat d'emmagatzemar l'estat quàntic de la llum i retornar-lo després d'un temps controlat.És un element important en la ciència de la informació quàntica i és un dispositiu crucial per a arquitectures de repetidors quàntica.Els sistemes d'estat sòlid basats en ions de terres rares són candidats prometedors per implementar MQs, ja que combinen els avantatges dels sistemes sòlids (escalabilitat i poca complexitat experimental) amb els llargs temps de coherència dels sistemes atòmics.En aquesta tesis he investigat tres protocols diferents de MQ en un cristall de Pr3+:Y2SiO5. La primera part descriu la primera demostració del protocol de memòria basat en forats espectrals (MFE), que va ser proposat teòricament el 2009. Aquest protocol es basa en disminuir la velocitat de la llum en un forat espectral de vida llarga i transferir les excitacions a un estat d'espín. Comencem preparant un forat espectral, després enviem un pols de llum amb una amplada espectral comparable a la del forat i aturem la llum comprimida en el cristall transferint la coherència fora de ressonància a l'estat d'espín amb un pols òptic.Seguidament un segon pols retorna la coherència i porta a l'emissió de la llum emmagatzemada. Aconseguim una eficiència d'emmagatzematge i recuperació de 40% en el règim clàssic i de 31% al nivell de fotons individuals, amb una relació senyal-soroll de 33 ±4 per un nombre mitjà de fotons incidents igual a 1. Aquests resultats demostren la memòria òtica operant al nivell de fotons individuals amb més eficiència i més lliure de soroll. La segona part de la tesis descriu nous experiments que utilitzen el protocol de pintes de freqüència atòmiques (PFA). Aquest està basat en modificar el perfil d'absorció eixamplat inhomogèniament dels ions de terres rares, creant pics d'absorció periòdics que indueixen la reemissió del camp de llum absorbit, després d'un cert temps que ve determinat per la separació dels pics. En aquest capítol descric varis experiments de PFA. Primer presento l'emmagatzematge en el nostre cristall de fotons amb freqüència convertida des de telecom, obtenint una eficiència total de 1.9 ± 0.2% per un temps d'emmagatzematge de 1.6us i una relació senyal-soroll de més de 200 per un nombre mitjà de fotons incidents igual a 1. Seguidament discuteixo els resultats obtinguts amb una millorada eficiència d'emmagatzematge en l'estat excitat per temps d'emmagatzematge llargs, on vam obtenir 30% per temps curts i 17% a 10us. I finalment presento un experiment de PFA amb ona d'espín on vam obtenir una relació senyal-soroll de 28 ± 8 per un nombre mitjà de fotons incidents igual a 1, el valor més alt assolit mai en un experiment d'aquest tipus. Finalment, en la última part, descric la primera demostració d'una font de parelles de fotons d'estat sòlid integrada amb una memòria quàntica multimodal. L'objectiu del protocol és combinar en un sol sistema una font de fotons individuals i una MQ, com té lloc en el conegut esquema de Duan-Lukin-Cirac-Zoller (DLCZ), però en aquest cas amb un cristall en lloc d'un sistema d'àtoms freds.El protocol agafa els avantatges del protocol PFA per refasar els ions i obtenir una recuperació eficient. Utilitzant PFA fa que el protocol sigui temporalment multimodal.En l'experiment, després de la preparació de la PFA, enviem un pols d'escriptura en ressonància i detectem un fotó Stokes que anuncia excitacions d'espín individuals. Un temps més tard, un pols de lectura transfereix l'excitació d'espín de tornada cap a l'estat excitat i detectem fotons anti-Stokes. Mostrem fortes correlacions de segon ordre no-clàssiques entre els fotons de Stokes i anti-Stokes i demostrem l'emmagatzematge de 11 modes temporals. Els resultats presentats en aquesta tesis representen una contribució significativa en el camp de les memòries quàntiques d'estat sòlid i un pas important cap a la realització d'arquitectures de xarxes quàntiques amb sistemes d'estat sòlid
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Atabaki, Amir Hossein. "Reconfigurable silicon photonic devices for optical signal processing." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41207.
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Processing of high-speed data using optical signals is a promising approach for tackling the bandwidth and speed challenges of today's electronics. Realization of complex optical signal processing functionalities seems more possible than any time before, thanks to the recent achievements in silicon photonics towards large-scale photonic integration. In this Ph.D. work, a novel thermal reconfiguration technology is proposed and experimentally demonstrated for silicon photonics that is compact, low-loss, low-power, fast, with a large tuning-range. These properties are all required for large-scale optical signal processing and had not been simultaneously achieved in a single device technology prior to this work. This device technology is applied to a new class of resonator-based devices for reconfigurable nonlinear optical signal processing. For the first time, we have demonstrated the possibility of resonance wavelength tuning of individual resonances and their coupling coefficients. Using this new device concept, we have demonstrated tunable wavelength-conversion through four-wave mixing in a resonator-based silicon device for the first time.
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Wilkinson, Scott Tolbert. "Photonic devices for optical interconnects using epitaxial liftoff." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/15059.
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Calhoun, Kenneth Harold. "Thin film compound semiconductor devices for photonic interconnects." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15478.
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Ge, Zhibing. "MODELING OF LIQUID CRYSTAL DISPLAY AND PHOTONIC DEVICES." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3867.
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Liquid crystal (LC) materials have been widely applied in electro-optical devices, among which display is the most successful playground and numerous new applications in photonic areas (such as laser beam steering devices) are also emerging. To well guide the device design for optimum performance, accurate modeling is of prior and practical importance. Generally, the modeling of LC devices includes two parts in sequence: accurate LC molecule deformation extraction under external electric fields and optical calculation thereafter for the corresponding electro-optical behaviors. In this dissertation, first, hybrid finite element method and finite difference method are developed to minimize the free energy of the LC systems. In this part of study, with computer-aided derivation, the full forms of the LC free energy equations without any simplification can be obtained. Besides, Galerkin's method and weak form technique are further introduced to successfully degrade the high order nonlinear derivative terms associated with the free energy equations into ones that can be treated by first order interpolation functions for high accuracy. The developed modeling methods for LC deformation are further employed to study display structures, such as 2D and 3D in-plane switching LC cells, and provides accurate results. Followed is the optical modeling using extended Jones matrix and beam propagation method to calculate the electro-optical performances of different devices, according to their amplitude modulation property or diffractive one. The developed methods are further taken to assist the understanding, development, and optimization of the display and photonic devices. For their application in the display area, sunlight readable transflective LCDs for mobile devices and the related optical films for wide viewing angle are developed and studied. New cell structure using vertically aligned liquid crystal mode is developed and studied to obtain a single cell gap, high light efficiency transflective LCD that can be driven by one gray scale control circuit for both transmissive and reflective modes. And employing an internal wire grid polarizer into a fringe field switching cell produces a single cell gap and wide viewing angle display with workable reflective mode under merely two linear polarizers. To solve the limited viewing angle of conventional circular polarizers, Poincaré sphere as an effective tool is taken to trace and understand the polarization change of the incident light throughout the whole LC system. This study further guides the design of high performance circular polarizers that can consist of purely uniaxial plates or a combination of uniaxial and biaxial plates. The developed circular polarizers greatly enhance the viewing angle of transflective LCDs. Especially, the circular polarizer design using a biaxial film can even provide comparable wide viewing angle performance for the same vertically aligned cell as it is used between merely two linear polarizers, while using circular polarizers can greatly boost the display brightness. As for the beam steering device modeling, the developed LC deformation method is taken to accurately calculate the associated LC director distribution in the spatial light modulator, while beam propagation method and Fourier transformation technique are combined to calculate the near and far fields from such devices. The modeling helps to better understand the origins and formations of the disclinations associated with the fringe fields, which further result in reduced steering efficiency and output asymmetric polarizations between positive and negative diffractions. Optimization in both voltage profile and driving methods is conducted to well tune the LC deformation under strong fringe fields and improve the light efficiency.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD
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Camargo, Edilson Alexandre. "Switchable devices based on photonic crystal channel waveguides." Thesis, University of Glasgow, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412954.
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Bushell, Zoe L. "Development of novel infrared photonic materials and devices." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/841718/.
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This thesis investigates a range of novel photonic devices and their constituent semiconductor materials with emission in the infrared (IR) region of the spectrum. These have a variety of potential applications, including in telecoms, sensing and defence systems. Studies focus on aspects of the electronic and photonic band structures, and how these impact upon device performance. Type-II interband cascade lasers and LEDs emitting in the mid-IR region of 3 – 4 μm are characterised using temperature and hydrostatic pressure dependent techniques. The key finding is that the threshold current density exhibits a minimum for emission around 0.35 eV (~3.5 μm), in both the pressure dependent results and data for many devices with different design wavelengths. The increase in threshold current density towards lower energies can be explained by an increase in CHCC Auger recombination. The increase in threshold current towards higher energies cannot be well explained by an Auger process, and it is concluded that this may be evidence of defect-related recombination. Dilute bismide alloys are an interesting new material system for IR applications. The electronic and optical properties of several dilute bismide alloys are determined by spectroscopic ellipsometry. Key findings include the first experimental measurements of the spin-orbit splitting in GaNAsBi, which show that it is approximately independent of N content, and the first evidence for a decrease in the direct band gap of GaP with the addition of bismuth, reducing by 130 ± 20 meV/%Bi. The refractive index was determined for all the materials and in the transparency region the real part of the refractive index was found to decrease approximately linearly with increasing band gap. In addition to modifying the electronic properties, photonic effects can be used to develop new IR devices. Finite difference time domain simulations of photonic crystal cavity structures within thick multi-layer slabs were carried out. These showed that it is possible to achieve high Q-factors, > 10^4, in slabs with refractive indices corresponding to typical semiconductor heterostructures. This opens up possibilities for designing photonic crystal lasers that do not require the thin suspended membranes typically found in the literature, with applications in integrated photonic circuits and on-chip sensors.
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Tandon, Sheila (Sheila N. ). 1978. "Engineering light using large area photonic crystal devices." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33931.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references.
Photonic crystals are fabricated structures composed of a periodic arrangement of materials with differing indices of refraction. This research has focused on the realization of two distinct photonic crystal structures in which large area has played a key role: 1) large area broadband saturable Bragg reflectors, and 2) large area 2D photonic crystal devices. Saturable Bragg reflectors (SBRs) can be used to self-start ultra-short pulse generation in a variety of solid state and fiber lasers. To form shorter pulses, SBRs with broadband reflectivity and large area (100's of [mu]m) are required. This thesis describes the design and fabrication of large area broadband saturable Bragg reflectors through the monolithic integration of semiconductor saturable absorbers with large area broadband Bragg mirrors. One of the key elements for realizing this device is the development of a wet oxidation process to create buried low-index ... layers over large areas. Large area 2D photonic crystals enable new methods for routing and guiding light with applications in compact integrated optical circuits. This research has explored the design and fabrication of two large area (centimeter-scale) 2D photonic crystal devices: a superprism and a super- collimator.
(cont.) A superprism is a photonic crystal device in which the direction of light propagation is extremely sensitive to the wavelength and angle of incidence. A super- collimator is a device in which light is guided by the dispersion properties of a photonic crystal slab without boundaries which define the light's path. Design, fabrication, and testing are discussed for both 2D photonic crystal devices.
bu Sheila N. Tandon.
Ph.D.
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Bradley, Michael Scott. "Highly absorptive thin films for integrated photonic devices." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36394.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 52-53).
Highly absorptive thin films serve as the active layer of a new class of photonic devices based on the strong coupling of light and matter. In order to develop these devices into a new field of integrated photonics, methods for analysis, patterning, and deposition of the active layer are necessary. This thesis develops these methods and applies them to thin films of J-aggregates grown in a layer-by-layer (LBL) process, which have been shown to have remarkable optical and morphological properties and have recently enabled the demonstration of strong coupling between light and matter in an electroluminescent device at room temperature. J-aggregate thin films are analyzed using Kramers-Kronig regression to determine their complex index of refraction, an important parameter involved in photonic device design. Additionally, a soft lithography method is demonstrated for patterning and deposition of LBL J-aggregate thin films. Together, these methods can be used to further enable integrated photonics based on the strong coupling of light and matter.
by Michael Scott Bradley.
M.Eng.
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Chen, Jerry C. (Jerry Chia-yung). "Electromagnetic field computation and photonic band gap devices." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/11293.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (p. 147-166).
by Jerry Chia-yung Chen.
Ph.D.
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Selim, Ramsey. "Numerical modelling of photonic crystal based switching devices." Thesis, University of South Wales, 2010. https://pure.southwales.ac.uk/en/studentthesis/numerical-modelling-of-photonic-crystal-based-switching-devices(568c3416-9479-4c7e-aeb0-80c7d31a7e83).html.
Full textAbstract:
In the last few years research has identified Photonic Crystals (PhCs) as promising material that exhibits strong capability of controlling light propagation in a manner not previously possible with conventional optical devices. PhCs, otherwise known as Photonic Bandgap (PBG) material, have one or more frequency bands in which no electromagnetic wave is allowed to propagate inside the PhC. Creating defects into such a periodic structure makes it possible to manipulate the flow of selected light waves within the PhC devices outperforming conventional optical devices. As the fabrication of PhC devices needs a high degree of precision, we have to rely on accurate numerical modelling to characterise these devices. There are several numerical modelling techniques proposed in literature for the purpose of simulating optical devices. Such techniques include the Finite Difference Time Domain (FDTD), the Finite Volume Time Domain (FVTD), and the Multi-Resolution Time Domain (MRTD), and the Finite Element (FE) method among many others. Such numerical techniques vary in their advantages, disadvantages, and trade-offs. Generally, with lower complexity comes lower accuracy, while higher accuracy demands more complexity and resources. The Complex Envelope Alternating Direction Implicit Finite Difference Time Domain (CE-ADI-FDTD) method was further developed and used throughout this thesis as the main numerical modelling technique. The truncating layers used to surround the computational domain were Uniaxial Perfectly Matched Layers (UPML). This thesis also presents a new and robust kind of the UPML by presenting an accurate physical model of discretisation error. iv This thesis has focused on enhancing and developing the performance of PhC devices in order to improve their output. An improved and new design of PhC based Multiplexer/Demultiplexer (MUX/DEMUX) devices is presented. This is achieved using careful geometrical design of microcavities with respect to the coupling length of the propagating wave. The nature of the design means that a microcavity embedded between two waveguides selects a particular wavelength to couple from one waveguide into the adjacent waveguide showing high selectivity. Also, the Terahertz (THz) frequency gap, which suffers from a lack of switching devices, has been thoroughly investigated for the purpose of designing and simulating potential PhC based switching devices that operate in the THz region. The THz PhC based switching devices presented in this thesis are newly designed to function according to the variation of the resonant frequency of a ring resonator embedded between two parallel waveguides. The holes of the structures are filled with polyaniline electrorheological fluids that cause the refractive index of the holes to vary with applied external electric field. Significant improvements on the power efficiency and wavelength directionality have been achieved by introducing defects into the system.
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Peacock, Anna Claire. "Applications of light propagation in novel photonic devices." Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/42429/.
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In this thesis, the propagation of light in novel photonic devices has been studied theoretically, numerically and experimentally. In particular, self-similar solutions to the nonlinear Schrödinger equation have been investigated as a means of avoiding distortions associated with high power pulse propagation in optical fibres. The results show that it is the interplay between the nonlinear and dispersive effects that leads to stable formation of the self-similar solutions. By considering generalised nonlinear Schrödinger equations we have extended the previous investigations of linearly chirped parabolic pulse solutions, which exist in the normal dispersion regime, and have found a new broader class of self-similar solutions, which exist when the fibre parameters are allowed to vary longitudinally. Numerical simulations of these systems confirm the analytic predictions. Experimental confirmation of parabolic pulse generation in high gain cascaded amplifier systems and in highly nonlinear microstructured fibres is also reported. In addition, the propagation of light in modulated crystal structures has been investigated. By modifying the linear and nonlinear properties of the crystals it has been shown that it is possible to manipulate the speed and the wavelength of the propagating light. In particular, negative refractive index materials have been shown to support fast and/or slow propagating light, whilst two dimensional nonlinear photonic crystals have been used to demonstrate multiple harmonic generation over a wide range of phase matching angles. The influence of waveguiding geometries has also been considered to determine the optimum design for the efficiency of the devices
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Ning, Ding. "Analytical and Numerical Models of Multilayered Photonic Devices." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1207712683.
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Drummond, Miguel Vidal. "Photonic devices for optical and RF signal processing." Doctoral thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/7562.
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Doutoramento em Engenharia ElectrotécnicaO presente trabalho tem por objectivo o estudo de novos dispositivos fotónicos aplicados a sistemas de comunicações por fibra óptica e a sistemas de processamento de sinais RF. Os dispositivos apresentados baseiam-se em processamento de sinal linear e não linear. Dispositivos lineares ópticos tais como o interferómetro de Mach-Zehnder permitem adicionar sinais ópticos com pesos fixos ou sintonizáveis. Desta forma, este dispositivo pode ser usado respectivamente como um filtro óptico em amplitude com duas saídas complementares, ou, como um filtro óptico de resposta de fase sintonizável. O primeiro princípio de operação serve como base para um novo sistema fotónico de medição em tempo real da frequência de um sinal RF. O segundo princípio de operação é explorado num novo sistema fotónico de direccionamento do campo eléctrico radiado por um agregado de antenas, e também num novo compensador sintonizável de dispersão cromática. O processamento de sinal é não linear quando sinais ópticos são atrasados e posteriormente misturados entre si, em vez de serem linearmente adicionados. Este princípio de operação está por detrás da mistura de um sinal eléctrico com um sinal óptico, que por sua vez é a base de um novo sistema fotónico de medição em tempo real da frequência de um sinal RF. A mistura de sinais ópticos em meios não lineares permite uma operação eficiente numa grande largura espectral. Tal operação é usada para realizar conversão de comprimento de onda sintonizável. Um sinal óptico com multiplexagem no domínio temporal de elevada largura de banda é misturado com duas bombas ópticas não moduladas com base em processos não lineares paramétricos num guia de ondas de niobato de lítio com inversão periódica da polarização dos domínios ferroeléctricos. Noutro trabalho, uma bomba pulsada em que cada pulso tem um comprimento de onda sintonizável serve como base a um novo conversor de sinal óptico com multiplexagem no domínio temporal para um sinal óptico com multiplexagem no comprimento de onda. A bomba é misturada com o sinal óptico de entrada através de um processo não linear paramétrico numa fibra óptica com parâmetro não linear elevado. Todos os dispositivos fotónicos de processamento de sinal linear ou não linear propostos são experimentalmente validados. São também modelados teoricamente ou através de simulação, com a excepção dos que envolvem mistura de sinais ópticos. Uma análise qualitativa é suficiente nestes últimos dispositivos.
This work investigates novel photonic devices for optical fiber communication systems and microwave photonics. Such devices rely on linear and nonlinear optical signal processing. Basic linear optical devices such as the Mach-Zehnder delay interferometer enable delaying and adding optical signals with fixed or variable weights. Therefore, such device can be respectively used as an optical amplitude filter with two complementary optical outputs, or, as an optical phase filter with tunable group delay response. The first operation principle is explored in a novel instantaneous RF frequency measurement system, whereas the latter serves as basis to a novel photonic beamforming system for a phase array antenna, and also to a novel tunable optical dispersion compensator. Nonlinear optical signal processing is obtained when optical signals are delayed and mixed, instead of being linearly added. Such operation principle is behind electro-optical mixing, which is explored in a novel instantaneous RF frequency measurement system. All-optical mixing enables ultra-fast and thereby broad bandwidth operation. This operation principle is explored to obtain tunable wavelength conversion. An optical time division multiplexed signal with a large spectral width is parametrically mixed with two continuous wave pumps in a periodically-poled lithium niobate waveguide. Instead of continuous wave pumps, a pulsed pump in which each pulse has a tunable wavelength enables a novel routable optical time-to-wavelength division converter. The pump signal is parametrically mixed with the input optical signal in a highly nonlinear optical fiber. All the proposed linear and nonlinear optical signal processing devices are experimentally validated. In addition, theoretical modeling and simulations are presented in all concepts, with the exception of the ones which employ alloptical mixing. A qualitative analysis is sufficient for the latter devices.
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Roney, Thomas. "Applications of plasmonics in silicon based photonic devices." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/3397/.
Full textAbstract:
Surface plasmon polaritons are highly confined electromagnetic waves which can be employed in developing miniaturised optical devices for bridging the size-mismatch between the nanoscale electronics and large diffraction-limited photonic devices. For this purpose, it is desired to develop silicon compatible plasmonic devices in order to achieve seamless integration with electronics on the silicon-on-insulator platform. Plasmonic devices such as modulators, detectors, couplers, (de)multiplexers, etc, would possess the advantages of having a small device footprint, low cost, low power consumption and faster response time. In this thesis, different silicon-based plasmonic devices were investigated using finite element simulations, including optical modulators, couplers and splitters. A metallised stub filled with SiGe/Ge multiple quantum wells or quantum dots in a silicon matrix, coupled to a dielectric waveguide was investigated. The modulation principles include ’spoiling’ of the Q factor and conversion of the electromagnetic mode parity, due to variation of the absorption coefficient of the stub filling. A CMOS compatible interference-based Mach-Zehnder modulator with each arm comprising a metal-insulator-semiconductor-insulator-metal structure, and a simpler single arm variant, were considered for electro-optic and electroabsorption modulation respectively. The electron density profiles in bias-induced accumulation layers were calculated with the inclusion of size-quantisation effects at the oxide-silicon interfaces. These were then used to find the complex refractive index profiles across the structure, in its biased and unbiased states, and eventually the modulator insertion loss and extinction ratio, and their dependence on various structural parameters. Finally, a silicon-based plasmonic nanofocusing coupler was investigated, which comprised symmetric rectangular grooves converging towards a central metal-silicon-metal nano-slit at the apex of the structure. The structure was optimised to achieve maximum coupling of light incident from a wide input opening, and coherent excitation and focusing of surface plasmons as they propagate towards the nano-slit waveguide. Application of the nanofocusing structure to achieve simultaneous coupling and splitting was also investigated, whereby incident light was focused into two nano-slits separated by a metal gap region at the apex. Such a plasmonic coupler or splitter can be used for coupling light directly from a wide fibre grating opening into nanoplasmonic waveguides in future on-chip plasmonic-electronic integrated circuits, or into the two arms of a plasmonic Mach-Zehnder modulator.