Theoretical study of diode-pumped Nd:YAG triple-frequency UV laser by LBO crystal

Based on the nonlinear three optical waves of coupling theory, the walk-off angle, effective nonlinear coefficients and the interaction length of wavelength of 1064nm and 532nm were calculated numerically under the condition of second class phase matching of the LBO crystals. In the phase matching range, the bigger the effective nonlinear coefficient and the smaller walk-off angle between 1064nm and 532nm beams, the higher frequency conversion efficiency. When the fundamental frequency light was an ideal Gaussian beam, the conversion efficiency improved with the crystal length increasing in the case of a particular power. And then, the conversion efficiency is limited by the fundamental frequency light was absorbed and the walk-off angle was increased with the crystal length increasing.