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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Multiple quantum well structures as optical waveguides

MacBean, M. D. A. January 1986 (has links)
No description available.
2

Optical bistability in semiconductor waveguides

Aitchison, J. Stewart January 1987 (has links)
No description available.
3

Nonlinear Optics in III-V Quaternary Semiconductor Waveguides

Saeidi, Shayan January 2018 (has links)
The fundamental limits of electronic systems in communication networks motivated scholars to think of an alternative approach to overcome problems such as demand for wider bandwidths and heat dissipation. All-optical signal processing is demonstrated as a potential solution. A major improvement in cost and speed of networking systems is expected through replacing microelectronics by photonic chips. However, the variety of operations essential to perform all-optical signal processing cannot be handled by a single material platform yet. Several III-V semiconductors, such as AlGaAs, have demonstrated potentials for photonic integration; nevertheless, there is still lack of data in literature on nonlinear optical properties of these materials. In this thesis, we extend the quest to evaluate more candidates from this class of semiconductors. Moreover, we are aiming for demonstrating the potentials of various III-V compounds for nonlinear photonics on-a-chip. In this thesis, we propose several optical waveguide designs based on quaternary III-V semiconductors AlGaAsSb and InGaAsP. We present modal analysis for waveguide designs and show that effective mode area much less than 1 $\mu m^{2}$ can be obtained. We also report specific waveguide designs that display zero-dispersion points at the specific wavelength ranges of interest. The designed waveguides are thus expected to demonstrate efficient nonlinear optical interactions. Next step is the fabrication of these devices with the goal to experimentally assess their nonlinear optical performance. The fabrication process of InGaAsP/InP strip-loaded waveguide is briefly reviewed. Following that, we report on the first, to the best of our knowledge, demonstration of third-order nonlinear optical interactions in InGaAsP/InP strip-loaded waveguides. We have performed self-phase modulation, nonlinear absorption measurements, and four-wave mixing experiments at the telecom wavelength range. The nonlinear phase shift up to 2.5 $\pi$ has been observed. Following that, we use Monte-Carlo method for design optimization and tolerance analysis of a multi-step lateral taper Spot-Size Converter in indium phosphide. An exemplary four-step lateral taper design featuring 0.35 dB coupling loss at optimal alignment of a standard single-mode fiber, $>$7 $\mu m$ 1-dB displacement tolerance in any direction of in a facet plane, and a great stability against manufacturing variances demonstrated.
4

Monolithic Integration of Active and Second-order Nonlinear Functionality in Bragg Reflection Waveguides

Bijlani, Bhavin J. 29 August 2011 (has links)
This thesis explored the theory, design, fabrication and characterization of AlGaAs Bragg reflection waveguides (BRW) towards the goal of a platform for monolithic integration of active and optically nonlinear devices. Through integration of a diode laser and nonlinear phase-matched cavity, the possibility of on-chip nonlinear frequency generation was explored. Such integrated devices would be highly useful as a robust, alignment free, small footprint and electrically injected alternative to bulk optic systems. A theoretical framework for modal analysis of arbitrary 1-D photonic crystal defect waveguides is developed. This method relies on the transverse resonance condition. It is then demonstrated in the context of several types of Bragg reflection waveguides. The framework is then extended to phase-match second-order nonlinearities and incorporating quantum-wells for diode lasers. Experiments within a slab and ridge waveguide demonstrated phase-matched Type-I second harmonic generation at fundamental wavelength of 1587 and 1600 nm, respectively; a first for this type of waveguide. For the slab waveguide, conversion efficiency was 0.1 %/W. In the more strongly confined ridge waveguides, efficiency increased to 8.6 %/W owing to the increased intensity. The normalized conversion efficiency was estimated to be at 600 %/Wcm^2. Diode lasers emitting at 980 nm in the BRW mode were also fabricated. Verification of the Bragg mode was performed through imaging the near- field of the mode. Propagation loss of this type of mode was measured directly for the first time at 14 cm^-1. The lasers were found to be very insensitive with characteristic temperature at 215 K. Two designs incorporating both laser and phase-matched nonlinearity within the same cavity were fabricated, for degenerate and non-degenerate down-conversion. Though the lasers were sub-optimal, a parametric fluorescence signal was readily detected. Fluorescence power as high as 4 nW for the degenerate design and 5 nW for the non-degenerate design were detected. The conversion efficiency was 4176 %/Wcm^2 and 874 %/Wcm^2, respectively. Neither design was found to emit near the design wavelength. In general, the signal is between 1600-1800 nm and the idler is between 2200-2400 nm. Improvements in laser performance are expected to drastically increase the conversion efficiency.
5

Monolithic Integration of Active and Second-order Nonlinear Functionality in Bragg Reflection Waveguides

Bijlani, Bhavin J. 29 August 2011 (has links)
This thesis explored the theory, design, fabrication and characterization of AlGaAs Bragg reflection waveguides (BRW) towards the goal of a platform for monolithic integration of active and optically nonlinear devices. Through integration of a diode laser and nonlinear phase-matched cavity, the possibility of on-chip nonlinear frequency generation was explored. Such integrated devices would be highly useful as a robust, alignment free, small footprint and electrically injected alternative to bulk optic systems. A theoretical framework for modal analysis of arbitrary 1-D photonic crystal defect waveguides is developed. This method relies on the transverse resonance condition. It is then demonstrated in the context of several types of Bragg reflection waveguides. The framework is then extended to phase-match second-order nonlinearities and incorporating quantum-wells for diode lasers. Experiments within a slab and ridge waveguide demonstrated phase-matched Type-I second harmonic generation at fundamental wavelength of 1587 and 1600 nm, respectively; a first for this type of waveguide. For the slab waveguide, conversion efficiency was 0.1 %/W. In the more strongly confined ridge waveguides, efficiency increased to 8.6 %/W owing to the increased intensity. The normalized conversion efficiency was estimated to be at 600 %/Wcm^2. Diode lasers emitting at 980 nm in the BRW mode were also fabricated. Verification of the Bragg mode was performed through imaging the near- field of the mode. Propagation loss of this type of mode was measured directly for the first time at 14 cm^-1. The lasers were found to be very insensitive with characteristic temperature at 215 K. Two designs incorporating both laser and phase-matched nonlinearity within the same cavity were fabricated, for degenerate and non-degenerate down-conversion. Though the lasers were sub-optimal, a parametric fluorescence signal was readily detected. Fluorescence power as high as 4 nW for the degenerate design and 5 nW for the non-degenerate design were detected. The conversion efficiency was 4176 %/Wcm^2 and 874 %/Wcm^2, respectively. Neither design was found to emit near the design wavelength. In general, the signal is between 1600-1800 nm and the idler is between 2200-2400 nm. Improvements in laser performance are expected to drastically increase the conversion efficiency.
6

Nonlinear frequency conversion in isotropic semiconductor waveguides

Moutzouris, Konstantinos January 2003 (has links)
This thesis describes an experimental investigation of optical frequency conversion in isotropic semiconductor waveguides by use of several phase-matching approaches. Efficient, type I second harmonic generation of femtosecond pulses is reported in birefringently-phase-matched GaAs/Alox waveguides pumped at 2.01 μm. Practical second harmonic average powers of up to ~ 650 μW are obtained, for an average launched pump power of ~ 5 mW. This corresponds to a waveguide conversion efficiency of ~ 20 % and a normalized conversion efficiency of greater than 1000 % W−1cm−2. Pump depletion of more than 80 % is recorded. Second harmonic generation by type I, third order quasi-phase-matching in a GaAs- AlAs superlattice waveguide is reported for fundamental wavelengths from ~1480 to 1520 nm. Quasi-phase-matching is achieved through modulation of the nonlinear coefficient χ[sub](zxy)(2), which is realised by periodically tuning the superlattice bandgap. An average output power of ~25 nW is obtained for a launched pump power of < 2.3 mW. Type I second harmonic generation by use of first order quasi-phase-matching in a GaAs/AlAs symmetric superlattice waveguide is also reported, with femtosecond fundamental pulses at 1.55 μm. A periodic spatial modulation of the bulk-like second- order susceptibility χ[sub](zxy)(2) is realized using quantum well intermixing by As+ ion implantation. A practical second harmonic average power of ~1.5 μW is detected, for a coupled pump power of ~11 mW. Second harmonic generation through modal-phase-matching in GaAs/AlGaAs semiconductor waveguides is reported. Using femtosecond pulses, both type I and type II second harmonic conversion is demonstrated for fundamental wavelengths near 1.55 μm. An average second harmonic power of ~10.3 μW is collected at the waveguide output for a coupled pump power of < 20 mW. For a complete characterisation, the optical loss is measured in these nonlinear GaAs- based waveguides over the spectral range 1.3-2.1 μm in the infrared, by deploying a femtosecond scattering technique. Typical losses of ~5-10 dB/cm are measured for the best of the waveguides, while a systematic intensity and wavelength dependent study revealed the contribution of Rayleigh scattering and two photon absorption in the overall transmission loss.
7

Conversion de fréquence vers les grandes longueurs d'onde dans des guides d'onde en semi-conducteurs à orientation périodique / Frequency conversion to long wavelength generation in orientation patterned semiconductor waveguides

Roux, Sophie 09 November 2016 (has links)
Le développement de sources moyen infrarouge compactes et accordables dans les gammes de transmission de l’atmosphère présente un intérêt majeur dans les secteurs de la défense et de la sécurité. Les sources paramétriques à quasi-accord de phase en configuration guidée sont prometteuses pour gagner en compacité puisque l’on réduit la puissance de pompe nécessaire par rapport aux sources « massives ». Le premier axe de la thèse consiste à étudier des guides d’onde en arséniure de gallium périodiquement orientés (OP-GaAs) adaptés à un pompage par laser fibré et à des puissances relativement élevées. Le second vise à étudier de façon novatrice la possibilité d’intégrer dans un composant monolithique une diode laser en matériaux antimoniures avec un convertisseur de fréquence en antimoniure de gallium (GaSb). L’enjeu dans les deux cas est de réduire au maximum les pertes à la propagation dans ces guides d’onde pour exploiter pleinement leurs propriétés non-linéaires.Ce travail de thèse a permis de modéliser des structures de guides d’onde ambitieuses pour réduire les pertes, de développer les briques technologiques nécessaires à la fabrication de guides d’onde OP-semi-conducteur faibles pertes et de faire de premières caractérisations de ces composants dans le moyen-infrarouge. Les performances de guides d’onde GaAs ruban enterrés ou non ont pu être comparées, donnant une réduction des pertes d’un facteur trois avec des rubans enterrés. Plusieurs générations de guides d’onde GaSb ont vu le jour, et montrent des performances à l’état de l’art des structures en GaAs. En conséquence, diverses solutions ont été explorées pour intégrer une diode laser en matériaux antimoniures avec le guide d’onde convertisseur de fréquence. / The development of compact and tunable mid-infrared laser sources in the atmospheric transmission windows presents a major interest for several security and defense applications. Quasi-phase-matched parametric sources in guided wave configuration are promising solutions to enhance compactness, because of the reduction in pump power requirements with respect to bulk devices.The first axis of this thesis consists in studying orientation-patterned gallium arsenide (OP-GaAs) waveguides, adapted to fiber laser pumping and to relatively high pump power. The second axis is devoted to the original idea of integrating an antimonide based laser diode with a gallium antimonide (GaSb) frequency converter in a monolithic component. The goal in both cases is to minimize propagation losses in those waveguides to exploit the whole potential of their non-linear properties.This work led to model ambitious low-loss waveguides structures, to develop the technological fabrication steps necessary for OP-semiconductor waveguides manufacturing, and to characterize these components in the mid-infrared. The first buried ridge GaAs waveguide structure has been compared to the ridge one, giving a reduction of a factor three in the propagation losses. Several generations of GaSb waveguides have come forward, with constant losses improvement and reach GaAs state-of-the-art performances. Lastly, multiple solutions have been explored in order to integrate an antimonide-based laser diode with the frequency converter waveguide.

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