フッ化カルシウム単結晶アニール後の複屈折シミュレーション : クリープ挙動を考慮した残留応力による解析

概要

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We developed an analysis system for simulating birefringence of an annealed ingot of CaF_2 single crystal caused by the residual stress after annealing process. The analysis system comprises the heat conduction analysis that provides the temperature distribution during ingot annealing, the stress analysis to calculate the residual stress after ingot annealing, and the birefringence analysis of an annealed ingot induced by the residual stress. The finite element method was applied to the heat conduction analysis and the stress analysis. In these analyses, the temperature dependence of material properties and the crystal anisotropy were taken into account. In the residual stress calculation, we considered the time-dependent nonlinear deformation behavior of a material called creep. In the birefringence analysis, the distributions of optical path difference were calculated by using the average stress method with consideration of the crystal anisotropy. We can perform the birefringence analysis of an ingot of CaF_2 single crystal with any growth direction, using this analysis system, and we performed the analyses of the crystals with the <100> and <111> growth directions. From these analyses, we obtained reasonable results of optical path difference in comparison with the experimental results.
2010-10-25