Thèses sur le sujet « Aluminum waveguide »

A near infrared hybridly mode-locked dye laser system consisting of a femtosecond oscillator and a high repetition rate dye amplifier was designed and built. This system was then applied to the study of room temperature below-bandgap femtosecond switching and coherent pulse propagation in GaAs/GaAlAs multiple quantum well waveguides. The noise properties of the oscillator output were studied using radio frequency spectrum analysis techniques. Two distinct modes of operation were identified: The first is characterized by the shortest pulse duration and its real-time autocorrelation signal appears more strongly modulated. The second mode of operation, which exhibits a slightly longer pulse duration and a smoother real-time autocorrelation signal, is obtained for a relative cavity length detuning of ΔL = -0.7 μm. Unexpectedly, the second mode features larger pulse duration fluctuations than the first mode and self-pulsing, while the pulse repetition timing and pulse energy fluctuations were found to be similar in both cases, making the first mode preferable for use in time-resolved experiments. Femtosecond all-optical switching under off-resonance room temperature excitation was demonstrated in a passive GaAs/AlGaAs multiple quantum well directional coupler for the first time. The required phase mismatch originates from an ultrafast refractive index change caused by the optical Stark effect. The main obstacle regarding practical device applications is its low transmission (less than 10%). The use of electrically pumped semiconductor waveguides that provide gain promises to remove this disadvantage. Below-resonance, coherent pulse breakup in a room temperature semiconductor waveguide was observed for the first time. Numerical simulations of the coupled semiconductor Maxwell-Bloch equations show that the light-matter interaction can induce enough chirp through self-phase modulation during propagation in order to violate the initial adiabatic following regime and cause pulse breakup. This coherent effect is distinctly different from self-induced transparency, because it does not involve Rabi-oscillations at the start of propagation, from temporal solitons, because it does not require group velocity dispersion, and from self-steepening. However, it should be ubiquitous under off-resonance pulse propagation with a pulse duration less than the polarization dephasing time.

Thesis (M.S.)--West Virginia University, 2006.
Title from document title page. Document formatted into pages; contains vii, 85 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 70-72).

An experimental investigation on the furnace and CO₂ laser densification of sol-gel derived SiO₂-TiO₂-Al₂O₃ planar optical waveguides was performed. Solutions containing equal mole fractions of tetraethoxysiline [Si(C₂H₅O)₄], titanium ethoxide [Ti(C₂H₅O)₄], aluminum tri-sec-butoxide [Al(C₄H₉O)₃] were used to spin films with a nominal 2:2:1 molar SiO₂-TiO₂-Al₂O₃ composition. Emphasis was placed on determining what effects the densification techniques had on film shrinkage, index change, crystallization and composition. Film shrinkage and refractive index change were found to be similar for both densification techniques. Fully dense, amorphous film were obtained with both methods. After densification, further heating caused titania crystalline phases to form with both processing techniques. However, anatase formed in the furnace fired films while rutile formed in the laser irradiated films.

O presente trabalho tem como objetivo principal a produção e estudo de filmes de nitreto de alumínio (AlN) depositados por pulverização catódica (sputtering) reativa e a fabricação e caracterização de guias de onda tipo pedestal utilizando o AlN como núcleo. Inicialmente, filmes de AlN foram fabricados por pulverização catódica reativa (sputtering) de rádio frequência (RF) utilizando um alvo de alumínio (Al) com 99,999% de pureza, e nitrogênio (N2) como gás reativo. Subsequentemente, os filmes foram caracterizados mediante as técnicas de elipsometria, difração de raios X (DRX), espectroscopia de absorção por transformada de fourier na região do infravermelho (FTIR) e espectroscopia de absorção na região do ultravioleta e do visível (UV-VIS). Tendo as melhores condições ópticas e físicas para a deposição de filmes de AlN, foram fabricados neste trabalho guias de onda tipo pedestal utilizando estes filmes como núcleo. O guia de onda pedestal traz um processo de fabricação alternativo, em que a geometria do guia de onda determina-se na camada anterior ao do núcleo, assim já não é necessário delinear as paredes laterais da camada de núcleo facilitando desta forma, o processo de fabricação do dispositivo. Os guias de tipo pedestal fabricados neste trabalho foram definidos através da corrosão parcial do óxido de silício (SiO2) mediante a técnica de RIE (Reactive Ion Etching) usando gases trifluorometano (CHF3) e oxigênio (O2) como gases reativos. Uma vez definido o pedestal, um filme de nitreto de alumínio é depositado sobre o SiO2 com a finalidade de constituir o núcleo do guia de onda. O ar foi utilizado como revestimento superior, cujo índice de refração (n = 1) aumenta o confinamento da luz no núcleo e também para poder possibilitar a caracterização das perdas ópticas do dispositivo. Para esta caracterização usamos a técnica de vista superior que permitiu a análises das perdas ópticas de propagação para diferentes alturas de pedestal e diferentes espessuras de núcleo tanto para filmes de AlN orientado no plano cristalino (002) quanto para filmes de AlN amorfos.
The main objective of this work is the production and study of Aluminum Nitride (AlN) films deposited by reactive sputtering and the fabrication and characterization of pedestal optical waveguides using AlN as core. Initially, aluminum nitride films were produced by reactive sputtering using a 99.999% aluminum (Al) purity target, and nitrogen (N2) as the reactive gas. Subsequently, the films were characterized by ellipsometry, X-ray Diffraction, Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet-visible spectroscopy (UV-VIS). Once the best optical and physical conditions for the deposition of AlN films were obtained, pedestal waveguides using these films as a nucleus were fabricated in this work. The pedestal waveguide provides an alternative manufacturing process where the geometry of the waveguide is determined in the pre-core layer, so it is no longer necessary to delineate the side walls of the core layer thereby facilitating the device fabrication process. The pedestal waveguides fabricated in this work were defined by the partial corrosion of SiO2 by the RIE (Reactive Ion Etching) technique using CHF3 and O2 gases as reactive gases. Once the pedestal is completed, an aluminum nitride film is deposited onto the SiO2 layer as the waveguide core. The air was used as an upper cladding, whose refractive index (n ? 1) increases the confinement of the light in the core and also allows the optical loss characterization. For this characterization, we used the superior view technique that allowed the analysis of optical propagation losses for different pedestal heights and different core thicknesses for both highly (002) oriented and amorphous AlN films.

Le confinement électrique et optique par oxydation des couches minces d'AlGaAs est une étape essentielle dans la réalisation des composants photoniques actifs et passifs dans la filière de matériaux GaAs. La recherche de performances ultimes sur ces composants nécessite une meilleure maîtrise du procédé d'oxydation ainsi qu'une meilleure connaissance des propriétés optiques de l'oxyde d'aluminium (AlOx). Dans cette perspective, j'ai d'abord réalisé une étude expérimentale de la vitesse d'oxydation des couches d'AlGaAs en fonction de la température du substrat, de la composition en gallium des couches étudiées, de la pression atmosphérique et de la géométrie des mesas considérés. Puis, j'ai établi un modèle anisotrope permettant une meilleure résolution spatiale et temporelle de la forme du front d'oxydation de l'AlAs. Enfin, j'ai exploité ce procédé pour réaliser des composants d'optique guidée notamment des micro-résonateurs puis réalisé des guides optiques à fente et caractérisé leurs performances optiques
Optical and electrical confinement using Al(Ga)As layer oxidation is a key milestone in the fabrication of active and passive GaAs-based photonic components. To optimize those devices, through the control of the optical and electrical confinements, a better modelling of oxidation process and a better understanding of optical properties of aluminum oxide (AlOx) is required. One part of this work is focusing on a throughout experimental study of AlGaAs oxidation kinetics, where I studied different important parameters such as wafer temperature, gallium composition, atmospheric pressure and mesa geometry. Then, I developed a new predictive model taking into account the process anisotropy, thus allowing a better temporal and spatial of AlAs oxidation front evolution. Finally, I could exploit this technological process to realize whispering gallery mode microdisks as well as slot optical waveguides, and I have characterized this latter photonic devices

Dans le cadre des recherches sur des dispositifs laser compacts pouvant etre pompes par diodes, ce memoire decrit le developpement d'une nouvelle technique d'elaboration de lasers guides d'onde, l'epitaxie en phase liquide. Cette technique a ete appliquee a la croissance de couches minces monocristallines de yag dope neodyme et ytterbium sur des substrats de yag non dope. Afin d'obtenir des guides de bonne qualite, nous avons defini les conditions de croissance des couches et montre l'interet de la croissance d'une surcouche de confinement. Deux co-dopages ont ete etudies en supplement a l'ion actif: gallium pour controler l'indice optique des couches, lutetium pour controler leur parametre cristallin. La determination du coefficient de segregation des divers dopants a requis le developpement d'un modele qui prend en compte l'evolution des bains au cours du temps. Nous avons mesure l'augmentation d'indice due a chaque dopant et propose un mecanisme expliquant cette augmentation. La caracterisation spectroscopique des couches a indique que les ions actifs ont les memes proprietes que le materiau massif de meme composition. La caracterisation laser a montre des pertes par propagation tres faibles (environ 0,1 db/cm), comparables a celles du materiau massif. Pour la transition laser a 1064 nm du neodyme, nous avons demontre l'effet laser pour une puissance absorbee au seuil de 700 w et mesure un rendement differentiel de 40% en pompage par diode, pour un seuil de 14 mw. Pour des transitions laser quasi-3 niveaux, une diminution significative du seuil par rapport a une configuration non guidee a ete obtenue: a 946 nm dans un guide dope neodyme, a 1029 nm dans un guide dope ytterbium en pompage par barrette de diode 1w. Un rendement differentiel de 80% a egalement ete mesure dans un guide dope ytterbium emettant a 1048 nm

This dissertation addresses three research challenges in planar lightwave circuit (PLC) optical signal processing. 1. Dynamic localization, a relatively new class of quantum phenomena, has not been demonstrated in any system to date. To address this challenge, the quantum system was mapped to the optical domain using a set of curved, coupled PLC waveguides in aluminum gallium arsenide (AlGaAs). The devices demonstrated, for the first time, exact dynamic localization in any system. These experiments motivate further mappings of quantum phenomena in the optical domain, leading toward the design of novel optical signal processing devices using these quantum-analog effects. 2. The PLC microresonator promises to reduce PLC device size and increase optical signal processing functionality. Microresonators in a parallel cascaded configuration, called "side coupled integrated spaced sequence of resonators" (SCISSORs), could offer very interesting dispersion compensation abilities, if a sufficient number of rings is present to produce fully formed "Bragg" gaps. To date, a SCISSOR with only three rings has been reported in a high-index material system. In this work, one, two, four and eight-ring SCISSORs were fabricated in AlGaAs. The eight-ring SCISSOR succeeded in producing fully formed Bragg peaks, and offers a platform to study interesting linear and nonlinear phenomena such as dispersion compensators and gap solitons. 3. PLCs are ideal candidates to satisfy the projected performance requirements of future microchip interconnects. In addition to data routing, these PLCs must provide over 100-bit switchable delays operating at ~ 1 Tbit/s. To date, no low loss optical device has met these requirements. To address this challenge, an ultrafast, low loss, switchable optically controllable delay line was fabricated in AlGaAs, capable of delaying 126 bits, with a bit-period of 1.5 ps. This successful demonstrator offers a practical solution for the incorporation of optics with microelectronics systems. The three aforementioned projects all employ, in their unique way, the coupling of light between PLC waveguides in AlGaAs. This central theme is explored in this dissertation in both its two- and multi-waveguide embodiments.

This thesis aims at both developing highly nonlinear Aluminum Gallium Arsenide waveguides(AlGaAs) and demonstrating all-optical wavelength conversion via cross-phase modulation in AlGaAs waveguides at telecommunications wavelengths. This work covers waveguide design, device fabrication, device characterization and system work.

碩士
臺灣大學
電信工程學研究所
95
There are many allocated frequency band can provide a bandwidth of more than 5 GHz to realize high speed communication up to 2Ghps to 4Ghps. This thesis presents the design of bandpass filters on 60GHz-band and 70GHz-band. In this thesis, we design several coupling resonant bandpass filters for 60GHz-band and 70GHz-band by the substrate integrated waveguide (SIW) cavity structure on the LTCC and alumina substrate. And then we add shunt CPW lines to introduce a transmission zero. The lowest insertion loss of these filters is less than 2.8 dB, and the return loss is higher than 15 dB except the filter with transmission zero. There will be a second passband due to the high order mode of the cavity if we design filters by the substrate integrated waveguide cavity structure.

碩士
國立臺灣大學
電機工程學研究所
96
In order to provide the high speed communication with 5GHz bandwidth, this thesis focus on the design of 60GHz-band and 70GHz-band bandpass filters. In this thesis, there are two design structures. The first one is a rectangular ring structure. This structure can create two transmission zeros and have large bandwidth. But this structure is not suitable for the narrowband bandpass filter. The second one is using substrate integrated waveguide (SIW) cavity structure with coupled resonators. Because of the low loss of SIW, we can design SIW filter well. This structure can make the narrowband bandpass filter. Adding the shut CPW lines can introduce an additional transmission zero. We make these two structures on the LTCC substrate. But only the second structure is made on the alumina substrate. Besides the LTCC 60GHz BPF, the insertion loss are less than 2.8dB for all filters. The bandwidth of the rectangular ring structure BPF is 21.35%. And the bandwidth of SIW cavity structure BPFs are 6.8%