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1
Yi, Yasha 1974. "On-chip silicon based photonic structures : photonic band gap and quasi-photonic band gap materials." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29457.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2004."June 2004."
Includes bibliographical references (leaves 170-180).
This thesis focuses on integrated silicon based photonic structures, photonic band gap (PBG) and quasi-photonic band gap (QPX) structures, which are based on high refractive index contrast dielectric layers and CMOS compatibility. We developed a new type of silicon waveguide - Photonic Crystal (PC) cladding waveguide is studied based on PBG principle. The refractive index in the new PC cladding waveguide core therefore has a large flexibility. Low index core (e.g. SiO2) or hollow core waveguide can be realized with our PC cladding waveguide structure. The fabrication of the waveguide is compatible to CMOS process. To demonstrate the PBG guiding mechanism, we utilized prism coupling to the Asymmetric PC cladding waveguide and the effective index of the propagation mode is measured directly. The measured effective mode index is less than both Si and Si3N4 cladding layers, which is clear demonstration of the photonic band gap guiding principle. We also fabricated and measured the PC cladding channel waveguide. Potential applications include high power transmission, low dispersion, thin cladding thickness and nonlinear properties engineering. Secondly, we developed a Si-based multi-channel optical filter with tunability, which is based on omnidirectional reflecting photonic band gap structure with a relatively large air gap defect. Using only one device, multi channel filter with tunability around two telecom wavelength 1.55[mu]m and 1.3[mu]m by electrostatic force is realized. Four widely spaced resonant modes within the photonic band gap are observed, which is in good agreement with numerical simulations.
(cont.) The whole process is compatible with current microelectronics process technology. There are several potential applications of this technology in wavelength division multiplexing (WDM) devices. Thirdly, to further extend the photonic crystal idea, we studied the quasi-photonic crystal structures and their properties, especially for the fractal photonic band gap properties and the transparent resonant transmission states. A-periodic Si/SiO2 Thue-Morse (T-M) multilayer structures have been fabricated, for the first time, to investigate both the scaling properties and the omnidirectional reflectance at the fundamental optical band-gap. Variable angle reflectance data have experimentally demonstrated a large reflectance band-gap in the optical spectrum of a T-M quasicrystal, in agreement with transfer matrix simulations. The physical origin of the T-M omnidirectional band-gap has been explained as a result of periodic spatial correlations in the complex T-M structure. The unprecedented degree of structural flexibility of T-M systems can provide an attractive alternative to photonic crystals for the fabrication of photonic devices.
by Yasha Yi.
Ph.D.
2
Castiglicone, Dario Calogero. "Block copolymer based photonic band gap materials." Thesis, University of Reading, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501328.
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A photonic crystal is any material which exhibits a photonic band gap (PBG) and is comprised of a periodic arrangement of alternating layers of different dielectric constant. It has been found recently that an interesting route to approach such materials is via the synthesis of block copolymers which are able to microphase separate. This thesis describes the synthetic methods, in particular anionic polymerization, used to prepare such copolymers which exhibit photonic properties in the visible region of the electromagnetic spectrum.
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Maldovan, Martin. "Exploring for new photonic band gap structures." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30121.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references (leaves 103-104).
In the infinite set of possible photonic band gap structures there are no simple rules to serve as a guide in the search for optimal designs. The existence and characteristics of photonic band gaps depend on such factors as dielectric contrast, volume fraction, symmetry and connectivity of the dielectric structure. In this thesis a large set of photonic structures are developed to help understand the nature of the dependencies and provide a platform for easy fabrication of three-dimensional structures with large complete photonic band gaps. Two approaches for accessing new structures are examined. A systematic method based on crystallography to search for photonic band gap structures is established in this thesis. A search within the FCC space groups is undertaken resulting in the discovery of two new photonic band gap structures. Specific structures found in self-organizing systems, the single P, the single G, and single D structures, are shown to possess large photonic band gaps. Design guidelines to fabricate these structures by interference lithography are given. A layer-by-layer approximation of the single D structure amenable to fabrication by conventional semiconductor fabrication techniques is proposed. A second technique for obtaining photonic band gap structures with different topologies is based on the splitting of nodes in the diamond network. The realization of these structures using block copolymer self assembly and layer-by-layer lithographic technique are briefly examined.
by Martin Maldovan.
Ph.D.
4
Lancaster, Greg A. "A Tunable Electromagnetic Band-gap Microstrip Filter." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/952.
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In high frequency design, harmonic suppression is a persistent struggle. Non-linear devices such as switches and amplifiers produce unwanted harmonics which may interfere with other frequency bands. Filtering is a widely accepted solution, however there are various shortcomings involved. Suppressing multiple harmonics, if desired, with traditional lumped element and distributed component band-stop filters requires using multiple filters. These topologies are not easily made tunable either. A new filter topology is investigated called Electromagnetic Band-Gap (EBG) structures.
EBG structures have recently gained the interest of microwave designers due to their periodic nature which prohibits the propagation of certain frequency bands. EBG structures exhibit characteristics similar to that of a band-stop filter, but in periodically repeating intervals making it ideal for harmonic suppression. The band-gap frequency of an EBG structure may be varied by altering the periodicity of the structure. However, EBG materials are generally static in structure making tuning a challenge.
In this thesis, a novel solution for tuning the band-gap properties of an EBG structure is investigated. Designs aimed to improve upon existing solutions are reached. These designs involve acoustic and mechanical tuning methods. Performance is simulated using Agilent’s Advanced Design System (ADS) and a device is constructed and evaluated. Comparing all measured test cases to simulation, band-gap center frequency error is on average 4.44% and absolute band-gap rejection error is 1.358 dB.
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Whitehead, Debra Elayne. "Photonic band gap systems based on synthetic opals." Thesis, University of Salford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402126.
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Nanni, Emilio A. (Emilio Alessandro). "A 250 GHz photonic band gap gyrotron amplifier." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82364.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 191-206).
This thesis reports the theoretical and experimental investigation of a novel gyrotron traveling-wave-tube (TWT) amplifier at 250 GHz. The gyrotron amplifier designed and tested in this thesis has achieved a peak small signal gain of 38 dB at 247.7 GHz, with a 32 kV, 0.35 A electron beam and a 8.9 T magnetic field. The instantaneous -3 dB bandwidth of the amplifier at peak gain is 0.4 GHz. A peak output power of 45 W has been measured. The output power is not saturated but is limited by the 7.5 mW of available input power. The amplifier can be tuned for operation from 245- 256 GHz. With a gain of 24 dB and centered at 253.25 GHz the widest instantaneous -3 dB bandwidth of 4.5 GHz was observed for a 19 kV, 0.305 A electron beam. To achieve stable operation at these high frequencies, the amplifier uses a novel photonic band gap (PBG) interaction circuit. The PBG interaction circuit confines the TE₀₃-like mode which couples strongly to the electron beam. The PBG circuit provides stability from oscillations by supporting the propagation of TE modes in a narrow range of frequencies, allowing for the confinement of the operating TE₀₃-like mode while rejecting the excitation of oscillations at lower frequencies. Experimental results taken over a wide range of parameters, 15-30 kV and 0.25-0.5 A, show good agreement with a theoretical model. The theoretical model incorporates cold test measurements for the transmission line, input coupler, PBG waveguide and mode converter. This experiment achieved the highest frequency of operation (250 GHz) for a gyrotron amplifier. At present, there are no other amplifiers in this frequency range that are capable of producing either high gain or high-output power. With 38 dB of gain and 45 W this is also the highest gain observed above 94 GHz and the highest output power achieved above 140 GHz by any conventional-voltage vacuum electron device based amplifier. The output power, output beam pattern, instantaneous bandwidth, spectral purity and shot-to-shot stability of the amplified pulse meet the basic requirements for the implementation of this device on a pulsed dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectrometer.
by Emilio A. Nanni.
Ph.D.
7
Smirnova, Evgenya I. "Novel photonic band gap structures for accelerator applications." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32294.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005."June 2005."
Includes bibliographical references (p. 181-184).
In this thesis I present the design and experimental demonstration of the first photonic band gap (PBG) accelerator at 17.140 GHz. A photonic band gap structure is a one-, two- or three-dimensional periodic metallic and/or dielectric system (for example, of rods), which acts like a filter, reflecting rf fields in some frequency range and allowing rf fields at other frequencies to transmit through. Metal PBG structures are attractive for the Ku-band accelerators, because they can be employed to suppress wakefields. Wakefields are unwanted modes affecting the beam propagation or even destroying the beam. Suppression of wakefields is important. In this thesis, the theory of metallic PBG structures is explained and the Photonic Band Gap Structure Simulator (PBGSS) code is presented. PBGSS code was well benchmarked and the ways to'benchmark the code are described. Next, the concept of a PBG resonator is introduced. PBG resonators were modelled with Ansoft HFSS code, and a single-mode PBG resonator was designed. The HFSS design of a travelling-wave multi- cell PBG structure was performed. The multicell structure was built, cold-tested and tuned. Finally, the hot-test PBG accelerator demonstration was performed at the accelerator laboratory. The PBG accelerating structure was installed inside a vacuum chamber on the Haimson Research Corporation (HRC) accelerator beam line and powered with 2 MW from the HRC klystron. The electron bunches were produced by the HRC accelerator. The electron beam was accelerated by 1.4 MeV inside the PBG structure.
by Evgenya I. Smirnova.
Ph.D.
8
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.
9
Marsh, Roark A. "Experimental study of photonic band gap accelerator structures." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/52788.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 181-186).
This thesis reports theoretical and experimental research on a novel accelerator concept using a photonic bandgap (PBG) structure. Major advances in higher order mode (HOM) damping are required for the next generation of TeV linear colliders. In this work, PBG HOMs are studied theoretically and experimentally for the first time. PBG HOMs are shown in simulation to be low Q lattice modes, removed from the cavity defect and beam position. Direct wakefield measurements were made in hot test using the bunch train produced by the MIT HRC 17 GHz linear accelerator. Measurements are compared with beam-loading theory, and wakefield simulations using ANALYST. Excellent agreement is observed between theory predictions and power measured in the 17 GHz fundamental operating mode; reasonable agreement is also seen with the 34 GHz wakefield HOM. In order to understand the performance of PBG structures under realistic high gradient operation, an X-band (11.424 GHz) PBG structure was designed for high power testing in a standing wave breakdown experiment at SLAC. The PBG structure was hot tested to gather breakdown statistics, and achieved an accelerating gradient of 65 MV/m at a breakdown rate of two breakdowns per hour at 60 Hz, and accelerating gradients above 110 MV/m at higher breakdown rates. High pulsed heating occurred in the PBG structure, with many shots above 270 K, and an average of 170 K for 35x10⁶ shots. Damage was observed in both borescope and scanning electron microscope imaging.
(cont.) No breakdown damage was observed on the iris surface, the location of peak electric field, but pulsed heating damage was observed on the inner rods, the location of magnetic fields as high as 1 MA/m. Breakdown in accelerator structures is generally understood in terms of electric field effects. PBG structure results highlight the unexpected role of magnetic fields on breakdown. The hypothesis is presented that the low level electric field on the inner rods is enhanced by pulsed heating surface damage, and causes breakdown. A new PBG structure was designed with improved pulsed heating, and will be tested. These results greatly further the understanding of advanced structures with wakefield suppression that are necessary for future colliders.
by Roark A. Marsh.
Ph.D.
10
Aközbek, Neset. "Optical solitary waves in a photonic band gap material." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0007/NQ35096.pdf.
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Vats, Nipun. "Non-Markovian radiative phenomena in photonic band-gap materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ63758.pdf.
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Zhang, JieXi. "Experimental studies of hybrid photonic band gap accelerator structures." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103230.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 211-217).
This thesis reports the first high power tests of a hybrid photonic band gap (PBG) accelerator structure. PBG structures can support a single electromagnetic mode, thus damping higher-order modes (HOMs) generated by wakefields. We have designed, built and successfully tested a 17.14 GHz hybrid PBG (HPBG) structure containing both dielectric and metallic elements. Dielectric elements have low loss and the potential to survive high surface electromagnetic fields. The HPBG structure was constructed as a triangular lattice array with sapphire rods inside and copper rods outside sandwiched between copper plates. The lattice parameter and the rod pattern were adjusted to excite a high-Q TM0 2 mode and to suppress HOMs. This overmoded operation is a unique and novel feature of the hybrid design. The design included the birefringence of sapphire. Simulations showed relatively high surface fields at the triple point where sapphire, copper and vacuum meet as well as in any gaps between components in the clamped assembly. Three structures were tested with later structures designed to sequentially reduce the surface electric field. The third structure used sapphire rods with pin extensions at each end and obtained the highest gradient of 19 MV/m, corresponding to a surface E field of 78 MV/m, with a breakdown probability of 5 x 10 1 /pulse/m in 45-ns pulses. Operation above 20 MV/m gradient led to runaway breakdowns with extensive light emission and eventual damage. For all three structures, multipactor light emission was observed at gradients well below the breakdown threshold. Breakdown damage was found at the triple point where surface fields peaked. The deposition of copper onto sapphire resulting from breakdowns might eventually degrade the cavity quality. This research indicated that multipactor triggered at the triple point limited the operational gradient of the hybrid structure. These experiments represent the first high power tests of a hybrid PBG structure. The gradient achieved of 19 MV/m is the highest achieved with a dielectric structure. The gradient was found to be limited by multipactor and breakdown. The overmoded cavity with relatively large beam apertures might still find applications at high frequency or in high current transmission.
by JieXi Zhang.
Ph. D.
13
Hu, Qichao. "Synthesis of electromagnetic modes in photonic band gap fibers." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40896.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2007.Includes bibliographical references (leaves 66-67).
In this paper, we report on the successful synthesis of three individual modes, HE11, TEo0, and TE02 for transmission in photonic band gap fibers at near infrared wavelengths. We measure the propagation losses of the HE11 and TE01 modes both inside and outside the band gap of the fiber, and show that the TE01 is indeed the lowest loss mode, and is less lossy and has a much wider band gap than the HE11. We study the superpostions of the HE11 and TE01 modes using the pure phase approach, and discuss the degeneracy problem that arises. We analyze these superpositions by decomposing the superposed images into low energy eigenmodes (m < 3), and compute each of the eigenmode's contribution in the superposition. We show that the contributions of the HE11 and TE01 behave sinusoidally in their superpostions. Finally we also explain the minor discrepancies between the superposition and decomposition results.
y Qichao Hu.
S.B.
14
Tang, Xiaofeng. "The fabrication of 3-D photonic band gap structures." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/43305.
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Thesis (Elec. E.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 85-88).
by Xiaofeng Tang.
Elec.E.
15
Luan, Feng. "Linear and nonlinear properties of photonic band-gap fibres." Thesis, University of Bath, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410923.
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Gao, Jian. "Fluorescence Enhancement using One-dimensional Photonic Band Gap Multilayer Structure." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1343753064.
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Hung, Jenny. "3D spherical layer photonic band-gap structures in dichromate gelatin /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202008%20HUNG.
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Arsenyev, Sergey A. "Photonic band gap structures for superconducting radio-frequency particle accelerators." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107281.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 175-181).
This thesis presents the design and testing of the first multi-cell superconducting accelerating cavity with a photonic band gap (PBG) coupler cell. The structure serves as a building block for superconducting radio-frequency (SRF) electron accelerators. It has five accelerating cells: four cells of elliptical shape, commonly used for SRF cavities, and one PBG cell in the middle. The purpose of the PBG cell is to damp unwanted Higher-Order electromagnetic Modes (HOMs) in the structure. Strong HOM damping is highly desirable for SRF cavities because it increases maximum achievable beam current by reducing the negative effect that HOMs have on the propagating electron beam. In the presented structure, effective HOM damping is achieved because of the inherent frequency selective properties of the PBG cell. The HOM spectrum in the five-cell cavity was carefully analyzed using eigenmode and wakefield simulations with good agreement between the two methods. The simulations showed that most of the dangerous HOMs were damped to fairly low external quality factors on the order of 102-104. This in principle implies that the new multicell cavity will support much higher beam currents than achievable in conventional SRF cavities that are not optimized for high-current operation. The improved HOM damping does not significantly compromise the accelerating properties of the cavity which are comparable to those of the cavities that only use the elliptical cells. Additionally, the PBG cavity does not need HOM couplers on the beam-pipe sections of the structure, and hence for the same amount of acceleration has a shorter length in the direction of the propagating beam. The five-cell cavity was fabricated of high purity niobium. Fabrication and tuning mechanisms were successfully tested on a copper prototype before being implemented for the niobium cavity. The accelerating gradient profile in the tuned niobium cavity matched the desired profile within a 5% accuracy. Two cryogenic tests were conducted with the five-cell cavity. The first test did not succeed due to a problem with the low quality factor of the cavity's accelerating mode. The problem was identified as a poor waveguide joint in the fundamental power coupler. Modifications were made to the waveguide joint and a second cryogenic test was conducted. In the second test, the high cavity quality factor was demonstrated at the temperature of 4.2 K for accelerating gradients up to 3 MV/m. The measured value of the cavity's quality factor with all ports closed was 1.55 x 108, in agreement with the prediction. This agreement indicated that the implemented surface treatment was effective in the cavity, including the complex PBG cell. No cavity leaks were observed during the tests in superfluid helium, proving the reliability of the fabrication process which included difficult electron-beam welds. No hard barriers in the accelerating gradient were observed during the test, indicating the absence of fundamental limits to cavity's operation for the gradient of at least several MV/m. A series of room-temperature experiments were conducted to measure external quality factors of six dangerous HOMs in the fabricated five-cell cavity. The measurements agreed with the simulations, showing all of the measured Q-factors below 3 x 103. Effective HOM damping, together with the ability to support accelerating gradients of multiple MV/m at cryogenic temperatures, makes the cavity an attractive candidate for future high-current accelerators.
by Sergey A. Arsenyev.
Ph. D.
19
Allahverdyan, Karen. "Study of resonant reflection in helicoidal photonic band gap structures." Doctoral thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/25827.
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La présente thèse de doctorat rapporte une étude expérimentale sur la réflexion résonante de la lumière dans des structures hélicoïdales à bande photonique interdite. Plusieurs aspects optiques et électro-optiques des cristaux liquides cholestériques sont abordés en concentrant l’attention sur deux effets principaux: l’influence des conditions aux limites (mécaniques et optiques) sur les propriétés optiques des couches de cristaux liquides cholestériques et le contrôle de la bande interdite de ces dernières. On présente un élément à double-rétroaction optique basé sur une cavité de Fabry-Pérot remplie de cristal liquide cholestérique. Les propriétés spectrales et de polarisation de cet élément sont caractérisées expérimentalement et par des simulations théoriques. Un changement mineur dans la structure en haut (cavité de Fabry-Pérot) nous a permis d’obtenir une transmission non-réciproque de la lumière sans application d’un champ externe à l’élément en question. Nous avons observé une transmission non-réciproque de la lumière par un système qui ressemble beaucoup aux structures naturelles observées sur certaines carapaces d’insectes (par exemple, sur les élytres de certains coléoptères): une simple couche de matière transparente linéaire dans son état fondamental. L’effet est défini par deux facteurs principaux: la chiralité et la périodicité de la matière ainsi que les conditions asymétriques aux surfaces limites. Concernant la partie sur le contrôle de la bande interdite, nous présentons la création et l’utilisation du mélange de cristal liquide cholestérique à deux fréquences pour le ‘déroulement’ et la reconstruction dynamique de la structure hélicoïdale. Le processus de reconstruction est accéléré d’un ordre de grandeur par l’application de champs électriques modérés. L’étape suivante du contrôle de la bande interdite est l’accord en longueur d’onde de la bande interdite. Un effet électromécanique est utilisé pour générer et étudier l’auto-adaptation du pas d’hélice de la couche de cristal liquide cholestérique. L’anisotropie négative diélectrique a permis d’assurer la stabilisation de la structure hélicoïdale de la couche pendant l’application du champ électrique qui a aussi changé l’épaisseur de la couche de cristal liquide en pliant un des substrats minces de la cellule. Cette déformation de la couche a généré un d’accord (et des sauts) des longueurs d’onde de la bande interdite. Les études spectrales et morphologiques pendant les changements de la bande interdite sont présentées et discutées.The present PhD thesis reports experimental study of resonant reflection in helicodal photonic band gap structures. Several optical and electro-optical properties of cholesteric liquid crystals are investigated where attention was concentrated on two principal phenomena: the influence of mechanical and optical boundary conditions on optical properties of cholesteric liquid crystal layers and control of photonic band gap of cholesteric liquid crystals. The creation of a double-feedback optical element based on a Fabry-Perot cavity filled with a planar aligned cholesteric liquid crystal mixture is presented. The polarization and spectral properties of this element are characterized experimentally and simulated theoretically. Experimental results are obtained for the transmittance dependence upon the orientation of the linear polarization plane and the polarization state of incident probe beam. A slight change in above mentioned structure (Fabry-Perot cavity) let us obtain a non-reciprocal transmittance of light without applying any external field. We observed an optical non reciprocity in a material system that is very close to natural structures, such as insect skin: a single layer of linear transparent material in its ground state. The process is shown to be defined by two key parameters: the chiral and periodic nature of the material and its asymmetric boundary conditions. In the part of band gap control, we present the creation and the use of dual frequency cholesteric liquid crystal mixtures for the dynamic electrical unwinding and forced (accelerated) restoring of their molecular helix. The restoring process is accelerated almost by an order of magnitude for quite moderate voltages used. The next step of band gap control is the tuning of band gap (wavelength). Strong electromechanical effect was used to generate and study self-adaptation and pitch jumps in a layer of cholesteric liquid crystal. The negative dielectric anisotropy of the material allowed its stabilization by the electric field and important thickness changes, achieved thanks to the use of a very thin substrate, allowed the observation of multiple dynamic jumps at fixed deformation conditions. Spectral and morphological studies of the material during those jumps were performed and are presented.
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Wu, Jay-Hsing 1979. "Characterization of planar photonic band gap structures with controllable bandstop widths." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80153.
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The effects of planar PBG structure with microstrip transmission line were investigated. Both measurement and simulation results are compared and the bandstop characteristics such as 3 dB bandstop width, central bandstop frequency, and maximum attenuation were examined. Also, various dimensions of PBG structure were explored to demonstrate the correlation to the bandstop effects. It was found that the central bandstop frequency is directly depended on the period distance (a). Meanwhile, the maximum attenuation was observed to depend on the number of periods presented in the ground plane. Furthermore, the vertical scale of the square perforation to the period distance ratio (d/a) was found to affect the left bandstop edge consistently. As the ratio is increased from 0.2 to 0.9, the left bandstop edge shifts toward the lower frequencies steadily and the range of the frequency shift is around 3.5 GHz. This important finding gives the PBG structure the potential to be tuned.Moreover, the possibilities of switching and tuning of the PBG structure were also investigated. Switching of the PBG structure with a gold metal piece electrically was successfully demonstrated. At 16 GHz, the bandstop effect is being switched off from -35 dB to -1 dB. Also, tuning of the bandstop edge was demonstrated and the range of frequency shift measured is 1.5 GHz. Therefore, the switching and tuning abilities of the PBG structure can be utilized as tunable filters.
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Benoit, Gilles Ph D. Massachusetts Institute of Technology. "Tunable micro-cavities in photonic band-gap yarns and optical fibers." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36206.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.Includes bibliographical references (leaves 134-140).
The vision behind this work is the fabrication of high performance innovative fiber-based optical components over kilometer length-scales. The optical properties of these fibers derive from their multilayer dielectric photonic band-gap structure that exhibits omnidirectional reflectivity. The theoretical tools needed to design, analyze and optimize such structures are introduced. We show that defect layers in these otherwise periodic structures act as optical micro-cavities that enable precise design of the fibers' spectral response. Fabrication of these composite fibers by thermal drawing of a macroscopic preform in the viscous state requires solving material selection challenges in order to identify pairs of materials with high refractive index contrast and similar thermo-mechanical properties. Operational wavelengths ranging from the UV to the IR are demonstrated and made possible by the wavelength scalability of the photonic band-gap structure and accurate knowledge of the materials' dispersion relation afforded by broadband spectroscopic ellipsometry. The fundamentals of this technique, which is used to characterize a number of dielectrics, semi-conductors and metals, are surveyed. Two fiber structures are then explored: fibers for external reflection and hollow-core transmission fibers.
(cont.) We demonstrate that the resonance wavelength of Fabry-Perot cavities embedded in reflecting fibers can be tuned reversibly under applied elastic strain or external illumination at 514 nm. A simple opto-mechanical model is developed to assess the mechanical tuning efficiency while a review of the photodarkening effect in chalcogenide glasses and accurate measurements of the amplitude and response time associated with its transient component are presented to explain and optimize the optical tuning scheme. Modulation of the fibers' reflectivity near their cavity resonant wavelengths is demonstrated at various frequencies. Based on these results, we show that optical micro-cavities in transmission fibers can induce very high group-velocity dispersion as a result of the interaction between the propagating core modes and the lossy cavity resonant mode(s). Widely tunable dispersion is achieved using a mechanical tuning scheme. Applications for these fibers and future research directions are envisioned.
by Giles Benoit.
Ph.D.
22
Amoah, T. K. "Designer disordered complex media : hyperuniform photonic and phononic band gap materials." Thesis, University of Surrey, 2016. http://epubs.surrey.ac.uk/812500/.
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In this thesis we investigate designer disordered complex media for photonics and phononics applications. Initially we focus on the photonic properties and we analyse hyperuniform disordered structures (HUDS) using numerical simulations. Photonic HUDS are a new class of photonic solids, which display large, isotropic photonic band gaps (PBG) comparable in size to the ones found in photonic crystals (PC). We review their complex interference properties, including the origin of PBGs and potential applications. HUDS combine advantages of both isotropy due to disorder (absence of long-range order) and controlled scattering properties from uniform local topology due to hyperuniformity (constrained disorder). The existence of large band gaps in HUDS contradicts the long-standing intuition that Bragg scattering and long-range translational order is required in PBG formation, and demonstrates that interactions between Mie-like local resonances and multiple scattering can induce on their own PBGs. The discussion is extended to finite height effects of planar architectures such as pseudo-band-gaps in photonic slabs as well as the vertical confinement in the presence of disorder. The particular case of a silicon-on-insulator compatible hyperuniform disordered network structure is considered for TE polarised light. We address technologically realisable designs of HUDS including localisation of light in point-defect-like optical cavities and the guiding of light in free-form PC waveguide analogues. Using finite-difference time domain and band structure computer simulations, we show that it is possible to construct optical cavities in planar hyperuniform disordered solids with isotropic band gaps that efficiently confine TE polarised radiation. We thus demonstrate that HUDS are a promising general-purpose design platform for integrated optical micro-circuitry. After analysing HUDS for photonic applications we investigate them in the context of elastic waves towards phononics applications. We demonstrate the first phononic band gaps (PnBG) for HUDS. We find that PnBGs in phononic HUDS can confine and guide elastic waves similar to photonic HUDS for EM radiation.
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Kwan, Kai-Cheong. "The effects due to disorder in the applications of photonic band gap materials /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202002%20KWAN.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 58-59). Also available in electronic version. Access restricted to campus users.
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Charlton, Martin David Brian. "Computational design and microfabrication of photonic crystals." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287304.
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Reynolds, Andrew Lawrence. "Modelling of photonic band gap materials for mm-wave and optical applications." Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325302.
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Hughes, Alison Frances. "A new theory of lasers with application to photonic band gap materials." Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368127.
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Kang, Henry Hao-Chuan. "Fabrication of Ceramic Layer-by-Layer Infrared Wavelength Photonic Band Gap Crystals." Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/835375-KQ7RuV/webviewable/.
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Khodami, Maryam. "Dispersion Characteristics of One-dimensional Photonic Band Gap Structures Composed of Metallic Inclusions." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23179.
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An innovative approach for characterization of one dimensional Photonic Band Gap structures comprised of metallic inclusions (i.e. subwavelength dipole elements or resonant ring elements) is presented. Through an efficient S- to T-parameters conversion technique, a detailed analysis has been performed to investigate the variation of the dispersion characteristics of 1-D PBG structures as a function of the cell element configuration. Also, for the first time, the angular sensitivity of the structure has been studied in order to obtain the projected band diagrams for both TE and TM polarizations. Polarization sensitivity of the subwavelength cell element is exploited to propose a novel combination of elements which allows achieving PBGs with simultaneous frequency and polarization selectivity. The proposed approach demonstrates that the dispersion characteristic of each orthogonal polarization can be independently adjusted with dipole elements parallel to that same polarization. Generally, the structure has potential applications in orthomode transducer, and generally whenever the polarization of the incoming signal is to be used as a means of separating it from another signal in the same frequency band that is of orthogonal polarization. The current distribution and the resonance behavior of the ring element is studied and the effect of resonance on dispersion characteristics of 1-D PBGs composed of rings is investigated for the first time, for both individual and coupled rings. Interestingly, it is observed that 1-D PBG composed of resonant elements consistently has a bandgap around the resonant frequency of the single layer structure.
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Rappe, Andrew Marshall. "AB initio theoretical studies of transition-metal, molecular, and photonic band-gap materials." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/29861.
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Hang, Zhihong. "Experimental investigation on the effect of disorder in metallo-photonic band gap system /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202004%20HANG.
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Shakya, Jagat B. "Micro/nano-photonic structures and devices of III-nitride wide band-gap semiconductors /." Search for this dissertation online, 2004. http://wwwlib.umi.com/cr/ksu/main.
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Mohammadi, Saeed. "Phononic band gap micro/nano-mechanical structures for wireless communications and sensing applications." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/41069.
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Because of their outstanding characteristics, micro/nano-mechanical (MM) structures have found a plethora of applications in wireless communications and sensing. Many of these MM structures utilize mechanical vibrations (or phonons) at megahertz or gigahertz frequencies for their operation.
On the other hand, the periodic atomic structure of crystals is the fundamental phenomenon behind the new era of electronics technology. Such atomic arrangements lead to a periodic electric potential that modifies the propagation of electrons in the crystals. In some crystals, e.g. silicon (Si), this modification leads to an electronic band gap (EBG), which is a range of energies electrons can not propagate with. Discovering EBGs has made a revolution in the electronics and through that, other fields of technology and the society.
Inspired by these trends of science and technology, I have designed and developed integrated MM periodic structures that support large phononic band gaps (PnBGs), which are ranges of frequencies that phonons (and elastic waves) are not allowed to propagate.
Although PnBGs may be found in natural crystals due to their periodic atomic structures, such PnBGs occur at extra high frequencies (i.e., terahertz range) and cannot be easily engineered with the current state of technology. Contrarily, the structures I have developed in this research are made on planar substrates using lithography and plasma etching, and can be deliberately engineered for the required applications. Although the results and concepts developed in this research can be applied to other substrates, I have chosen silicon (Si) as the substrate of choice for implementing the PnBG structure due to its unique properties.
I have also designed and implemented the fundamental building blocks of MM systems (e.g., resonators and waveguides) based on the developed PnBG structures and have shown that low loss and efficient MM devices can be made using the PnBG structures. As an example of the possible applications of these PnBG structures, I have shown that an important source of loss, the support loss, can be suppressed in MM resonators using PnBG structures. I have also made improvements in the characteristics of the developed MM PnBG resonators by developing and employing PnBG waveguides.
I have further shown theoretically, that photonic band gaps (PtBGs) can also be simultaneously obtained in the developed PnBGs structures. This can lead to improved photon-phonon interactions due to the effective confinement of optical and mechanical vibrations in such structures.
For the design, fabrication, and characterization of the structures, I have developed and utilized complex and efficient simulation tools, including a finite difference time domain (FDTD), a plane wave expansion (PWE), and a finite elements (FE) tool, each of which I have developed either completely from scratch, or by modification of an existing tool to suit my applications. I have also developed and used advanced micro-fabrication recipes, and characterization methods for realizing and characterizing these PnBG structures and devices. It is agued that by using the same ideas these structures can be fabricated at nanometer scales to operate at ultra high frequency ranges.
I believe my contributions has opened a broad venue for new MM structures based on PnBG structures with superior characteristics compared to the conventional devices.
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CHINCHOLI, ASHWIN. "PARALLEL FABRICATION OF PHOTONIC CRYSTALS USING INTERFERENCE LITHOGRAPHY." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115996014.
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Yamashita, Tsuyoshi. "Unraveling photonic bands : characterization of self-collimation in two-dimensional photonic crystals." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-06072005-104606/.
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Thesis (Ph. D.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2006.Summers, Christopher, Committee Chair ; Chang, Gee-Kung, Committee Member ; Carter, Brent, Committee Member ; Wang, Zhong Lin, Committee Member ; Meindl, James, Committee Member ; Li, Mo, Committee Member.
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Kral, Zdenek. "Development of optical characterization methods for micro-and nano- scale planar photonic band gap structures." Doctoral thesis, Universitat Rovira i Virgili, 2009. http://hdl.handle.net/10803/8466.
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The characterization of photonic band gap materials (Photonic Crystals) is a fundamental issue in the development of the technologies for their fabrication and future application. This Doctoral Thesis has dealt with the development of optical characterization methods and their implementation to planar photonic structures. According to the objectives established in the present work we have obtained several results that are concluded in the following paragraphs: We have developed an experimental technique based on the Bragg diffraction in the near and middle infra red (IR) spectral range to determine the lattice properties of planar photonic structures.
We have applied the Angular-Dependent Reflectance Spectroscopy technique (ADRS) to the characterization of photonic bands in PhC slabs. The objective was the implementation of the technique to our samples with lattice parameters that require the measurement to be carried out in the mid-IR spectral range.
We have implemented the Angle-Resolved Spectroscopic Polarimetry to characterize the band structure of planar photonic-crystal structures in the visible spectral range.
We have developed of a simulation tool and post-processing method to enhance the photonic bands recognition by the cited methods.
La caracterización de materiales de gap fotónico (Cristales Fotónicos) es un aspecto fundamental en el desarrollo de las tecnologías para su fabricación y su futura utilización. Esta tesis doctoral se ha ocupado del desarrollo de métodos ópticos de caracterización, así como de su implementación en estructuras fotónicas planares, también conocidas como láminas de cristal fotónico (Photonic Cristal Slabs). De acuerdo con los objetivos fijados para el presente trabajo, hemos obtenido varios resultados, los cuales se resumen en los párrafos siguientes:
Se ha desarrollado una técnica experimental basada en la difracción de Bragg en el rango espectral de la radiación infrarroja (IR) cercana y media, para determinar las propiedades de varias estructuras fotónicas planas.
Se ha aplicado la técnica de la espectroscopia de reflectometría en ángulo variable (Angular-Dependent Reflectance Spectroscopy, ADRS) a la caracterización de bandas fotónicas en láminas de cristal fotónico. El objetivo ha sido la implementación de la técnica a las muestras fabricadas en el marco del grupo NePhoS de la Universitat Rovira i Virgili. Estas muestras tienen parámetros de red que requieren llevar a cabo una medición en un rango espectral del infrarojo (IR) medio.
Finalmente, se ha desarrollado otra técnica óptica para caracterizar estructuras fotónicas planas: la polarimetría espectroscópica de ángulo variable.
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Thapa, Rajesh. "Doppler-free spectroscopy of acetylene in near infrared spectral region inside photonic band gap fiber." Manhattan, Kan. : Kansas State University, 2005. http://hdl.handle.net/2097/133.
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Franson, Steven James 1974. "Finite difference time domain analysis of photonic band gap structures in one and two dimensions." Thesis, The University of Arizona, 1997. http://hdl.handle.net/10150/278606.
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Dielectric and magnetic structures which inhibit the propagation of light for a given frequency range at any angle of incidence are said to have a photonic band gap (PBG). By placing defects inside of these PBG structures, useful devices can be constructed including micro-cavity lasers and nanometer scale waveguides. This thesis is concerned with the evaluation of these PBGs in order to obtain an understanding of how they work, as well as developing new methods to evaluate them. The photonic band gap configurations are modeled with the Finite Difference Time Domain (FDTD) method in one and two dimensions. By modeling these structures in the time domain, the finite amount of time that it takes to establish the photonic band gaps may be observed. Also, methods using the Fast Fourier Transform in combination with the FDTD algorithm are capable of determining the frequency spectrum of a structure with little computation time.
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Lozada, Vera John Jairo. "Propagação não linear de pulsos em estruturas 1D com band gap fotônico." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277154.
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Orientador: Solange Bessa CavalcantiDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Estuda-se a interação entre pulsos ópticos ultracurtos e materiais com band gap fotônico, considerando-se a propagação de luz através de estruturas unidimensionais, compostas de uma super-rede dielétrica periódica cuja célula unitária consiste em um par de camadas com diferentes índices de refração n1e n2, respectivamente. Em particular considera-se o caso em que n2, por exemplo, é um material com não linearidade X (3). É bem sabido que a largura e a localização dos band gaps dependem fundamentalmente do contraste entre os índices de refração d n = | n1 - n1 | e, atribuindo-se a n2 um índice de refração dependente da intensidade, conseguimos controlar dinamicamente a largura do band gap com o pulso de luz incidente. Portanto, a idéia básica é investigar a dinâmica de propagação nas vizinhanças de um band gap dependente da intensidade para aplicações importantes no projeto de dispositivos fotônicos, como por exemplo limitadores de luz e switches puramente ópticos. Dentro do formalismo de Maxwell, experimentos computacionais são feitos considerando a propagação de campos ópticos através de super-redes que possuem não linearidades do tipo Kerr, assim como saturável. Esta última é importante para a descrição da interação com pulsos muito intensos já que neste caso a mudança induzida no índice de refração depende de não linearidades de ordem mais alta e, como consequência, alcança uma saturação. Este modelo é apropriado para descrever materiais tais como vidros dopados com semicondutores (e.g. CdS 1-x Sex) polímeros orgânicos, que possuem propriedades ópticas altamente não lineares. A propagação da onda é resolvida usando uma versão modificada no domínio do tempo do método standard fast Fourier Beam Propagation Method (FFT-BPM) com um passo adaptativo, que pode manejar transmissão, difração e, especialmente, reflexões das ondas electromagnéticas causadas por descontinuidades no índice de refração, com a vantagem de não requerer a introdução de condições de contorno adicionais.
Abstract: The interaction of ultrashort optical pulses with photonic band gap materials has been studied by considering light propagation through one-dimensional photonic band gap structures, composed of a periodic multilayer stack of dielectric materials whose unitary cell consists of a pair of layers with different refractive indices n1and n2, respectively. One of these, say n2, is doped with a X (3)nonlinear material. It is well known that band gaps widths and locations depend fundamentally on the refractive index contrast d n = | n1 - n1 | and, by assigning to n2 an intensity dependent refractive index, one is bound to dinamically control the band gap width with the incident light pulse. Therefore, the basic idea here is to investigate the dynamics of propagation in the neighborhood of such an intensity-dependent band gap for important applications in the design of all-optical photonic devices such as limiters and switches. Within the framework of Maxwell's equations, a numerical investigation is made by considering the propagation of optical fields through multilayers with a Kerr, as well as a saturable, type of nonlinearity. The latter is important for the description of the interaction with high field strength pulses because in this case the field-induced change in the refractive index is influenced by higher-order nonlinearities and, as a consequence, this change becomes saturated. This model is appropriate to describe materials such as semiconductor-doped glasses (e.g. CdS 1-x Sex) and organic polymers, which have high nonlinear optical properties. The wave propagation is solved using a time-domain modified version of the standard fast Fourier Beam Propagation Method (FFT-BPM) with an adaptive step size, which can handle transmission, diÿraction and, especially, reflection of electromagnetic waves caused by discontinuities on the refractive index, with the advantange of not requiring the introduction of additional boundary conditions.
Mestrado
Ótica
Mestre em Física
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Li, Jianyou. "Oligonucleotide guanosine conjugated to gallium nitride nano-structures for photonics." Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9065/.
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In this work, I studied the hybrid system based on self-assembled guanosine crystal (SAGC) conjugated to wide-bandgap semiconductor gallium nitride (GaN). Guanosine is one of the four bases of DNA and has the lowest oxidation energy, which favors carrier transport. It also has large dipole moment. Guanosine molecules self-assemble to ribbon-like structure in confined space. GaN surface can have positive or negative polarity depending on whether the surface is Ga- or N-terminated. I studied SAGC in confined space between two electrodes. The current-voltage characteristics can be explained very well with the theory of metal-semiconductor-metal (MSM) structure. I-V curves also show strong rectification effect, which can be explained by the intrinsic polarization along the axis of ribbon-like structure of SAGC. GaN substrate property influences the properties of SAGC. So SAGC has semiconductor properties within the confined space up to 458nm. When the gap distance gets up to 484nm, the structure with guanosine shows resistance characteristics. The photocurrent measurements show that the bandgap of SAGC is about 3.3-3.4eV and affected by substrate properties. The MSM structure based on SAGC can be used as photodetector in UV region. Then I show that the periodic structure based on GaN and SAGC can have photonic bandgaps. The bandgap size and the band edges can be tuned by tuning lattice parameters. Light propagation and emission can be tuned by photonic crystals. So the hybrid photonic crystal can be potentially used to detect guanosine molecules. If guanosine molecules are used as functional linker to other biomolecules which usually absorb or emit light in blue to UV region, the hybrid photonic crystal can also be used to tune the coupling of light source to guanosine molecules, then to other biomolecules.
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Woldeyohannes, Mesfin Arega. "Quantum electrodynamics of a driven three-level atom near the edge of a photonic band gap." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ59058.pdf.
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Kuang, Ping. "Economical fabrication methods of three-dimensional ceramic Photonic Band Gap crystals at micron and submicron scales." [Ames, Iowa : Iowa State University], 2007.
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Graham, Matthew. "DEVELOPMENT OF HIGH REFRACTIVE INDEX POLY(THIOPHENE) FOR THE FABRICATION OF ALL ORGANIC 3-D PHOTONIC MATERIALS WITH A COMPLETE PHOTONIC BAND GAP." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1164049666.
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Kurt, Hamza. "Photonic crystals analysis, design and biochemical sensing applications /." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-06252006-174301/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007.Papapolymerou, John, Committee Member ; Adibi, Ali, Committee Member ; Citrin, David, Committee Chair ; Summers, Christopher, Committee Member ; Voss, Paul, Committee Member.
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Rung, Andreas. "Numerical Studies of Energy Gaps in Photonic Crystals." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5848.
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SHARMA, ADITI. "A NEAR FIELD SCANNING OPTICAL MICROSCOPY INVESTIGATION OF PHOTONIC STRUCTURES." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1046725704.
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Ellis, Frederick Paa Kwesi. "Fabrication of Random Hole Optical Fiber Preforms by Silica Sol-Gel Processing." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/31489.
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Conventional fibers are comprised of a solid glass core and solid glass cladding often protected by a thin polymer sheath. The finely tuned difference in refractive indices, for step index-fibers, is achieved by doping the core with germanium or elements with similar effects. Holey fibers (including photonic crystal fibers) comprise of a pure silica core, and a pure but porous silica cladding of air holes [1]. This provides a huge difference in the refractive indices on the cladding and core without doping. This translates into radiation resistant fibers with very low losses and very robust to high temperatures to mention a few [2]. Several successful attempts have been made for ordered holey optical fibers since the initial publication by Knight et al; random holey optical fibers, which can be just as effective, have yet to be fabricated [3].
Sol-gel processing of silicon alkoxides can be used to fabricate silica monoliths of tailored pore densities and sizes [4]; this makes the process attractive for random holey fiber preform manufacturing. Similar attempts have been made by Okazaki et al [5] to make conventional optical fibers. This paper chronicles efforts to make random holey fiber optical preforms from silica sol-gel monoliths, characterized for some structural properties. Silica monoliths can be made by hydrolysis and condensation of TEOS (tetraethylorthosilicate) or TMOS (tetramethylorthosilicate). These can be catalyzed in a single step or two-step process, aged and dried at ambient pressures and temperatures, as well as by supercritical fluid extraction of CO2. Mechanical strengthening techniques as described by Okazaki [5] have also been employed. The silica gel monoliths are characterized by helium pycnometry and scanning electron microscopy. Various shapes and densities of silica monoliths have been prepared and characterized. Some of these have also drawn into fibers to demonstrate their viability.Master of Science
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Shahid, Naeem. "Technology and properties of InP-based photonic crystal structures and devices." Doctoral thesis, KTH, Halvledarmaterial, HMA, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-101662.
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Photonic crystals (PhCs) are periodic dielectric structures that exhibit a photonic band gap; a range of wavelengths for which light propagation is forbidden. 2D PhCs exhibit most of the properties as their three dimension counterparts with a compatibility with standard semiconductor processing techniques such as epitaxial growth, electron beam lithography, Plasma deposition/etching and electromechanical lapping/polishing. Indium Phosphide (InP) is the material of choice for photonic devices especially when it comes to realization of coherent light source at 1.55 μm wavelength. Precise engineering of the nanostructures in the PhC lattice offers novel ways to confine, guide and control light in phonic integrated circuits (PICs). Strong confinement of light in PhCs offer novel opportunities in many areas of physics and engineering. Dry etching, a necessary process step in PhC device manufacturing, is known to introduce damage in the etched material. Process induced damage and its impact on the electrical and optical properties of PhCs depends on the etched material, the etching technique and process parameters. We have demonstrated a novel post-etch process based on so-called mass-transport (MT) technology for the first time on InP-based PhCs that has significantly improved side-wall verticality of etched PhC holes. A statistical analysis performed on several devices fabricated by MT process technology shows a great deal of improvement in the reliability of optical transmission characteristics which is very promising for achieving high optical quality in PhC components. Several PhC devices were manufactured using MT technology. Broad enough PhC waveguides that operate in the mono/multi-mode regime are interesting for coarse wavelength de-multiplexing. The fundamental mode and higher order mode interaction creates mini-stop band (MSB) in the dispersion diagram where the higher order mode has a lower group velocity which can be considered as slow light regime. In this thesis work, the phenomena of MSBs and its impact on transmission properties have been evaluated. We have proposed and demonstrated a method that enables spectral tuning with sub-nanometer accuracy which is based on the transmission MSB. Along the same lines most of the thesis work relates to broad enough PhC guides that operated in the multimode regime. Temperature tuning experiments on these waveguides reveals a clear red-shift with a gradient of dλ/dT=0.1 nm/˚C. MSBs in these waveguides have been studied by varying the width in incremental amounts. Analogous to semiconductors heterostructures, photonic heterostructures are composed of two photonic crystals with different band-gaps obtained either by changing the air-fill factor or by the lattice constant. Juxtaposing two PhC and the use of heterostructures in waveguide geometry has been experimentally investigated in this thesis work. In particular, in multimode line defect waveguides the “internal” MSB effect brings a new dimension in single junction-type photonic crystal waveguide (JPCW) and heterostructure W3 (HW3) for fundamental physics and applications. We have also fabricated an ultra-compact polarization beam splitter (PBS) realized by combining a multimode waveguide with internal PhC. MSBs in heterostructure waveguides have shown interesting applications such as designable band-pass flat-top filters, and resonance-like filters with high transmission. In the course of this work, InGaAsP suspended membrane technology was developed. An H2 cavity with a linewidth of ~0.4 nm, corresponding to a Q value of ~3675 has been shown. InGaAsP PhC membrane is an ideal platform to study coupled quantum well/dot-nanocavity system.QC 20120831
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Brito, Davi Bibiano. "Acoplador e linha de l?mina unilateral e bilateral com substrato fot?nico." Universidade Federal do Rio Grande do Norte, 2006. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15343.
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Previous issue date: 2006-07-06Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The aim of this work is to characterize and use the characteristic parameters of the planar structures constructed with fin lines looking for their applications in devices, using PBG Photonic Band Gap photonic materials as substrate, operating in the millimeter and optic wave bands.The PBG theory will be applied for the relative permittivity attainment for the PBG photonic substrate s and p polarizations. The parameters considered in the structures characterization are the complex propagation constant and the characteristic impedance of unilateral and bilateral fin lines that were obtained by the use of the TTL Transverse Transmission Line Method, together with the Method of the Moments. The final part of this work comprises studies related to the behavior of the asymmetric unilateral fin line coupler with photonic substrate. This research opens perspectives for new works in this modern area. Numerical results are shown by means of bi-dimensional and three-dimensional graphics. Conclusions and suggestions for future works are also presented
O presente trabalho tem como objetivo caracterizar e utilizar os par?metros de estruturas planares constru?das com linhas de l?minas visando a sua utiliza??o em circuitos, com materiais fot?nicos do tipo PBG Photonic Band Gap como substrato, operando nas faixas de ondas milim?tricas e ?pticas. A teoria PBG ser? aplicada para a obten??o da permissividade relativa para as polariza??es s e p dos substratos compostos de material fot?nico PBG. Os par?metros considerados na caracteriza??o das estruturas s?o a constante de propaga??o complexa e a imped?ncia caracter?stica, de linhas de l?mina unilaterais e bilaterais, que foram obtidos atrav?s da utiliza??o do m?todo da Linha de Transmiss?o Transversa LTT com o aux?lio do M?todo dos Momentos. Nesse trabalho foi realizado ainda, um estudo do funcionamento do acoplador com linha de l?mina unilateral assim?trica com substrato fot?nico. Esta pesquisa abre perspectivas para novos trabalhos nesta moderna ?rea. A an?lise te?rica computacional desse trabalho se mostrou precisa, com compara??es de outros trabalhos, podendo ser empregada em outros dispositivos que utilizem a linha de l?mina como estrutura b?sica, e materiais ?pticos. Resultados num?rico-computacionais em forma de gr?fico em duas e tr?s dimens?es para todas as an?lises realizadas s?o apresentados, para as estruturas propostas que tem como substratos materiais fot?nicos. S?o apresentadas conclus?es e sugest?es para a continuidade deste trabalho
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Silva, Andre Tavora de Albuquerque. "Antenas planares reconfiguraveis do tipo V - estatico e tipo defasamento de arranjo por matrizes PBG - photonic band gap - para aplicação em telefonia movel celular." [s.n.], 2002. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260158.
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Orientador : Luiz Carlos KretlyDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Heineman, Dawn Laurel. "Optimization of ALD grown titania thin films for the infiltration of silica photonic crystals." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-05142004-143254/unrestricted/heineman%5Fdawn%5Fl%5F200407%5Fms.pdf.
Full textAbstract:
Thesis (M.S.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2005. Directed by Christopher Summers.Summers, Christopher, Committee Chair ; Snyder, Robert, Committee Member ; Wang, Zhong Lin, Committee Member. Includes bibliographical references.