<title>OPO performance with an aberrated input pump beam</title>

Abstract

The performance of an optical parametric oscillator (OPO) with non-ideal input pump fields is investigated numerically. The analysis consists of a beam propagation calculation based on Fourier methods including walk-off in the non-linear crystal coupled with the three-wave interaction in the crystal. The code is time dependent enabling analysis of laser pulses. The pump beam aberrations are described by Zernike polynomials. The OPO investigated is a LiNbO<SUB>3</SUB> crystal in a flat-flat resonator. The LiNbO<SUB>3</SUB> crystal is cut to produce a 1.5 micrometers signal and 3.6 micrometers idler from a 1.06 micrometers input pump field. The results show that the type of aberration is significant when predicting the output performance of the OPO and not simply the beam quality or M<SUP>2</SUP> angular divergence of the pump beam. While thresholds for input pump beams with M<SUP>2</SUP> equals 2 only increase on the order of 10% over unaberrated beams, the divergence of the output fields can be much worse than the pump beam divergence. The output beam divergence is also a function of the input pump energy. Aberrated pump fields can also lead to angular displacements between the generated signal and idler fields.