Thermal inhibition of high-power second-harmonic generation in periodically poled LiNbO_3 and LiTaO_3 crystals

摘要

A coupled thermo-optical model shows strong thermal inhibition of second-harmonic generation (SHG) in periodically poled (PP) LiNbO_3 (PPLN) and stoichiometric LiTaO_3 (PPSLT) crystals. Three-dimensional simulations performed for a 1.064 μm fundamental wavelength pulsed nanosecond laser beam 150 μm in radius show the onset of significant temperature nonuniformities along and across the irradiated zone, and strong thermal dephasing and inhibition of SHG in these crystals for input powers > 10 W. PPSLT is found to have a significant advantage over PPLN due to the higher heat conductance, decreasing these temperature nonuniformities and allowing one to maintain the irradiated zone within the corresponding SHG temperature tolerance range (ΔT ≈ 3 K).