OPO performance with an aberrated input pump beam

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 LiNbO3 crystal in a flat-flat resonator. The LiNbO3 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 M2 angular divergence of the pump beam. While thresholds for input pump beams with M2 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.