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Study On The Thermal Induced Birefringence And Polarization Of YAG Laser Medium

Posted on:2015-12-24Degree:MasterType:Thesis
Country:ChinaCandidate:J HuFull Text:PDF
GTID:2308330452455970Subject:Physical Electronics
Abstract/Summary:PDF Full Text Request
In this thesis, a theoretical and experimental for thermally induced birefringence andpolarization characteristics of the homogeneously pumped YAG laser medium isinvestigated. First, the development of thermally induced birefringence effects researcheswas introduced. Combined with the need for research, the theory of refractive index changeand cross section distribution profile that caused by thermally induced birefringence wasintroduced and analyzed. An analytical result of the radial and tangential refractive indexchanges as well as intensity of the transmitted wave that a linearly polarized light through abirefringent Nd:YAG crystal between parallel polarizers and orthogonal polarizers werederived, and calculated the depolarization ratio. Then, an experiment of conoscopicinterference was carried out in an uniaxial crystal and pumped [111]-cut Nd: YAG crystal.By analogy with an uniaxial crystal, a reasonable explanation for [111]-oriented Nd: YAGcrystal conoscopic interference patterns was given. The experiment verified the thermalinduced birefringence refractive index distribution profile of [111]-cut Nd:YAG medium hasradial symmetry property when under homogeneously pumped. At the same time, wededuced an equation by experimental measure of hyperbolic isogyre ring patterns spacing tocalculated the change of refractive index, moreover, it also can be used for quantitative studythe optical thermal distortion of laser medium. At last a detailed demonstrated the change ofpolarization state that after a linear polarized light through the thermally inducedbirefringence crystal.In order to analyzes the thermal depolarization, we simulated depolarization anddepolarization patterns of the cross section of [111]-cut Nd:YAG rod. As the depolarizationdepends on the crystal growth direction, make a comparison, a theoretical analysis andnumerical simulation for [100] direction crystal in depolarization ratio and the outputdepolarization intensity was investigated. And then analysed the depolarization of the twokinds direction discipline. Which confirmed the depolarization ratio in [100] direction issmaller than [111] direction at an appropriate incident linearly polarized. An experiment wascarried out to study the depolarization of [111]-cut Nd: YAG crystal. Finally, anexperimental scheme was designed to measure the [111]-oriented Nd: YAG crystal radialand tangential thermal focal length, and compared with theoretical calculations, which proved the feasibility and correctness of the scheme.
Keywords/Search Tags:YAG laser medium, Thermally induced birefringence, Conoscopic interference, Depolarization, Thermal focal length
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