Servo tuning and stabilization of nonlinear optical crystals

A new optical technique for servo tuning and stabilization of angle tuned nonlinear optical crystals is described. This technique has zero insertion loss and works equally well with collimated, focused, or noncollinear fundamental beams. Servo tuning of a Type I KDP nonlinear crystal for summing the output of a tunable dye laser with the Nd:YAG second harmonic and servo stabilization of the production of the Nd:YAG fourth harmonic in Type I KDP are demonstrated.