Non-critical phase matching of Gd xY 1− xCa 4O(BO 3) 3(Gd xY 1− xCOB) crystal

Abstract

By using an optical parametric amplifier (OPA), we have measured the non-critical phase-matching (NCPM) wavelengths for frequency-doubling (including type I and type II) in different Gd x Y 1− x COB crystals. From the Sellmeier equations of YCOB and GdCOB, we calculated the ranges of NCPM wavelengths in Gd x Y 1− x COB, and compared them with the data obtained from our experiment. When the output power of a mode-locked Nd/YAG laser is 110 mW (λ=1.064 μm), a conversion efficiency of 37% is obtained for the type II NCPM frequency-doubling in Gd 0.2Y 0.8COB crystal. Using a KTP crystal as frequency-doubler, we have achieved NCPM third harmonic generation (THG) in Gd 0.22Y 0.78COB crystal. When the output power of Nd/YAG laser is 94 mW and the power of the second-harmonic wave is 38 mW, THG conversion efficiency can reach 21%.