Temperature-insensitive sum frequency generation of 355-nm ultraviolet laser radiation in LiB3O5 by compensating thermally induced phase mismatch.

A temperature-insensitive sum frequency generation method based on thermally induced phase mismatch compensation is proposed to enhance the thermal stability and scale up the output power of ultraviolet (UV) lasers. In the method, three LiB3O5 crystals are cascaded for sum frequency generation of a 355-nm UV laser, and the two crystals at the ends are employed for frequency conversion; the middle one, which is not required to be phase matched and has an opposite sign of first temperature derivative of phase mismatch, compensates the thermally induced phase mismatch generated in the first crystal. The temperature acceptance bandwidth of frequency conversion in the three cascaded crystals is about double that in a single long crystal with the same interaction length.