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" Nonlinear behavior and applications of vertical cavity semiconductor optical amplifiers "
Zhang, Haijiang
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Latin Dissertation
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English
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| Record Number
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898112
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TL2831191g
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Iranmehr, Arya
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Nonlinear behavior and applications of vertical cavity semiconductor optical amplifiers\ Zhang, Haijiang
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2007
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2007
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| Abstract
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This dissertation mainly focuses on two closely-related research topics about Vertical Cavity Semiconductor Optical Amplifiers (VCSOAs). One is theoretical study, modeling, and characterization of the nonlinear gain characteristics of VCSOAs due to the dependence of nonlinear refractive index on carrier concentration in its Fabry-Perot (FP) cavity; the other is the experimental investigation of the feasibility of all-optical logic operations. First, the theoretical study and demonstration of Wavelength Bistability (WB) and Multiple Bistability (MB) in a VCSOA are presented. It is proved both experimentally and theoretically that WB and Power Bistability (PB) are inter-related through the same bistable switching points. MB is observed by sweeping the optical input power, with input wavelength fixed at the longer-wavelength side of two Polarization-Dependent Gain (PDG) windows of a VCSOA while the input polarization direction is set to a specific angle with respect to two intrinsic principal axes of material birefringence in the VCSOA. Secondly, a cascadable All-Optical Inverter (AOI), All-Optical Flip-Flop (AOFF) and All-Optical Pass Transistor (AOPT) are proposed and demonstrated experimentally based on VCSOAs. The operation of cascadable AOI is based on three types of nonlinearities in a VCSOA: Cross-Gain Modulation (XGM), nonlinear gain characteristics (including optical bistability), and polarization gain anisotropy. The demonstrated AOI shows fast switching time <80ps, low switching threshold (̃10[mu]W), and a high noise margin for cascadability. AOFF is realized by a cross-coupled AOI pair, demonstrating all-optical memory functionality at a low switching power. The realization of AOPT is based on a bistable VCSOA, where the signal output of a transistor is switched ON/OFF by an optical control beam that alters the bistable switching threshold for the signal beam through Cross-Phase Modulation (XPM). Finally, the nonlinear gain characteristics of VCSOAs subject to external feedback are studied. If optical feedback is constructive and co- polarized with the input beam, the resonant wavelength of the VCSOA experiences a red-shift and increased gain as the feedback is increased, resulting in enhanced nonlinear gain. When coherent optical feedback is cross-polarized with the input and its wavelength is detuned to the longer -wavelength side of both VCSOA intrinsic PDG windows, a self-sustained optical oscillation is obtained
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Zhang, Haijiang
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UC San Diego
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