Determination of the nonlinear optical coefficients of YCa_4O(BO_3)_3 crystal

Abstract

The nonlinear optical coefficients of YCa4O(BO3)3 (YCOB) have been calculated for the first time to the authors’ knowledge by use of the revised Gaussian 92 program on the basis of the anionic group theory. The d11,d12,d32, and d33 coefficients of the crystal were determined by the Maker fringes method at λ=1064 nm, and d13, and d31 were also evaluated by measurement of the Maker fringes. The coefficients determined by the Maker fringes are in agreement with the theoretical values. On the basis of the dij coefficients and the Sellmeier equations, the effective second-harmonic generation (SHG) coefficient deff of YCOB as a function of phase-matching angles θ and Φ was determined. It is interesting that the maximum effective SHG coefficient deff of YCOB is not in the principal plane but is located out of the X–Z plane in the positions θ=65.9°,Φ=36.5° and θ=66.3°,Φ=143.5°. It is also worth noting that the largest deff of YCOB in the region of 0°<θ<90°,90°<Φ<180° is larger than that in 0°<θ<90°,0°<Φ<90°. These calculated results have been proved by the effective SHG coefficient measurements of YCOB and conversion-efficiency measurements of frequency-doubling experiments on Nd:YCOB.