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Study on the Q-switching Microcosmic Mechanism of Semiconductor Saurable Absober

Author: TangWenZuo
Tutor: LiDeChun
School: Shandong University
Course: Optical Engineering
Keywords: Saturable absorber Maximize Molecular modeling Electronic structure Elastic properties
CLC: TN248
Type: Master's thesis
Year: 2011
Downloads: 51
Quote: 0
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Abstract


The all-solid-state Q-switched lasers, laser Q-components in the ordinary solid-state lasers with a full cure, small size, high pumping efficiency advantages great deal of concern by the people, has a broad application prospects. For Q-switched lasers, the performance of the Q-component has a great impact on the output of the laser, it is also critical to optimize its performance parameters. Semiconductor saturable absorber as a new type of passively Q components, with small size, simple structure, easy to use and low cost advantages, to become passively Q-switched laser field research hotspot. In this thesis rate equation theory, the middle mirror semiconductor saturable absorber mirror passively Q-switched laser output energy optimization; using molecular simulation technology for GaAs and InGaAs semiconductor saturable absorber electronic structure and elastic properties theoretical simulations. The main innovation of the paper contents of the following three parts: (I) according to the middle mirror type semiconductor saturable absorber mirror Q-mechanism, taking into account the InGaAs saturable absorption layer and the GaAs substrate saturable absorber in the Gaussian distribution introduced under the normalized parameters and gives a description of the middle mirror semiconductor saturable absorption mirror Q-switched laser pulse output performance normalized rate equation model, the saturable absorber mirror type intermediate body Q-switched laser pulse energy, peak power and pulse width optimization study, for the first time to come to the middle mirror semiconductor saturable absorber mirror (C-SESAM) passively Q-switched laser output characteristics under the optimized conditions of key performance parameters and the corresponding curve. (II) with the first plane wave pseudopotential method based on density functional theory of the GaAs intrinsic point defects (gallium vacancies, arsenic vacancy, gallium substitute arsenic, gallium arsenic alternative lattice structure optimized gallium-gap, the arsenic gap) exists obtained a stable structure; calculation of formation energy and then through the defect can be learned that the degree of difficulty that it is formed in the growth process, and from the angle of the density of states of a variety of intrinsic point defects caused by the defect level and electrons occupy situation analysis; Finally, with different intrinsic point defects GaAs saturable absorption calculated the elastic constants of the body, and the presence of intrinsic point defects in GaAs saturated to absorb the impact of the elastic properties of the body. Calculated intrinsic defect levels is important for the analysis of the formation mechanism of the EL2 deep level defects in GaAs saturable absorber; while the calculation of the elastic constants will also help to further analysis contains deep level defects in the structure of GaAs saturable absorber The flexible nature of the body, and GaAs crystal as a saturable absorber for passively Q-switched lasers are theoretically significant; (III) to study the electronic structure and elastic properties of In atoms doped the concentration gradient InGaAs crystal use Castep software, has been In atomic doping concentration gradient three InGaAs crystal state density distribution curve and the elastic constant values, and calculated using the Voigt-Reuss-Hill method to give the corresponding elastic modulus. Decreases with increasing a doping concentration of In atoms through simulation finding the width of the band gap of the InGaAs crystal; crystal elastic properties with the symmetry of the cubic crystal system, with the In atoms doping concentration increases, the elastic constant of the InGaAs crystal and elastic modulus smaller crystals reduce brittleness, ductility enhancement lattice easier deformation occurs; comparing the corresponding properties of the electronic structure and elastic properties of the simulation of InGaAs crystal GaAs crystal analysis of the InGaAs / GaAs lattice The reasons for mismatch and proposed solutions.

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