Equivalent temperature stabilization of nonlinear-optical crystals

We introduce an approach for the temperature stabilization of nonlinear-optic crystals during laser frequency conversion processes. This approach is based on the stabilization of the piezoelectric resonance (PR) frequency of the crystal, so that the crystal itself becomes a temperature sensor. Application of an electronic oscillator provides a remarkably handy way to determine the PR frequency. When the PR frequency stabilization was employed, the stable generation of the second harmonic (SH) at 532 nm wavelength was achieved in periodically poled lithium niobate (PPLN) at more than 30% power compared to the case of the application of external temperature sensors. Long-term stability of SH power was also enhanced.