Design of walk-off corrected biaxial crystal composites

摘要

A comprehensive model for determining the phase matching conditions for biaxial nonlinear crystals of general orientations of given Sellmeir equations for OPO applications has been developed. The model calculates the phase matching angle for a given pump wavelength and ranges of generated wavelengths, and the walk-off angle and refractive indexes and the polarization states of the fast and slow rays. Walk-off is proposed to be compensated by an Adhesive-Free Bond (AFB~R) twist 180° twin pair configuration the length of which is a function of the crystal type, crystal orientation, pump wavelength, converted wavelength, tuning curve, and beam diameter. The walk-off corrected design overcomes an obstacle that has prevented using biaxial crystals oriented in other than principal planes in terms of greater d_(eff) values. Experimental results on biaxial and uniaxial nonlinear single crystals have validated the model, allowing efficient evaluation of new nonlinear crystals and optimization of existing ones.