QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY
Print ISSN : 0288-4771
Theoretical Analysis on Temperature Dependence of SHG by Nonlinear Optical Crystal
Etsuji OHMURAKazufumi NOMURAIsamu MIYAMOTO
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2003 Volume 21 Issue 3 Pages 344-349

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Abstract

In recent years, applications of solid-state lasers with frequency conversion techniques such as SHG, THG and FHG to precision microfabrication progress rapidly. When nonlinear optical crystal used for frequency conversion absorbs laser beam, temperature of the crystal rises, and the frequency-conversion efficiency decreases. In this study, KH2PO4, that is potassium dihydrogen phosphate (KDP), whose physical properties are well known was supposed as a nonlinear optical crystal for SHG. Temperature dependence of frequency-conversion efficiency was examined theoretically by solving the coupling problem composed of heat conduction equation and complex amplitude equations, which are derived considering the absorption of laser in the crystal. The temperature change of the crystal induced by Nd:YAG laser absorption, the local change of refractive indices, and the consequential variation of SHG frequency-conversion efficiency were analyzed for single and repetitive pulses. As a result, the temperature dependence of frequency-conversion became clear quantitatively. Remarkable inverse-conversion of SHG also appears for the repeated laser irradiation with high power density.

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© 2003 by JAPAN WELDING SOCIETY
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