Bandwidth and threshold calculations for angle-tuned parametric oscillators.

The bandwidth of angle-tuned optical parametric oscillators, in some cases, is limited by the noncolinear interaction of the pump, signal, and idler beams, which results when the nonlinear material is rotated relative to the pump beam. To determine this bandwidth, a theoretical expression for the pump power threshold is derived in the near field limit taking into account double refraction for a noncolinear interaction. Angle tuning can be done by (1) rotating the crystal and mirrors as a unit, or by (2) rotating the crystal only. Expressions for determining the tuning rate and threshold increase for both tuning methods are derived.