By using an optical parametric amplifier (OPA), we have measured the non-cr
itical phase-matching (NCPM) wavelengths for frequency-doubling (including
type I and type II) in different GdxY1-xCOB crystals. From the Sellmeier eq
uations, of YCOB and GdCOB, we calculated the ranges of NCPM wavelengths in
GdxY1-xCOB, and compared them with the data obtained from our experiment.
When the output power of a mode-locked Nd/YAG laser is 110 mW (lambda = 1.0
64 mum), a conversion efficiency of 37% is obtained for the type II NCPM fr
equency-doubling in Gd0.2Y0.8COB crystal. Using a KTP crystal as frequency-
doubler, we have achieved NCPM third harmonic generation (THG) in Gd0.22Y0.
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%. (C) 2001 Published by Elsevier Science Ltd.