CW optical parametric oscillation near 2.1 μm, pumped by 1064 nm

All previously demonstrated continuous wave (cw) optical parametric oscillators (OPOs) have required noncritical (90°) phasematching. Critical (non 90°) phasematching can reduce the parametric gain by orders of magnitude due to Poynting vector walkoff. For example, room temperature conversion between 1 and 2 microns in lithium niobate (LN) phasematches at 45° to the z axis and has a Boyd-Kleinman gain reduction factor of h⩽0.1. In fact, Boyd and Kleinman pointed out that a 1064 nm pumped degenerate cw OPO using LN has a threshold pump power of 4.5 W, assuming a round trip power loss of 2% We can decrease the threshold pump power by reducing the losses in our resonator. We have designed an uncoated, total internal reflection (TIR) resonator that has a finesse limited only by the absorption and scatter loss of the nonlinear crystal