High-efficiency single-pass >100mW continuous-wave UV-355nm generation by focusing optimization of 1064nm cascaded third harmonic generation in periodically poled lithium niobate crystals

High-efficiency single-pass CW UV 355nm generation using PPLN has been studied under focusing optimization concept. Using a 25mm (1st order, SHG) PPLN crystal cascaded with a 10mm (3rd order, SFG) PPLN crystal and 3.8W 1064nm input pump, we have successfully generated >100mW CW 355nm output with good beam quality and power stability. As compared to previous publications and to other kind of nonlinear materials, maximum CW UV 355nm power generated from PPLN has been enhanced by a factor of 2~3, and the single pass conversion efficiency at 4W 1064nm input level has been enhanced by a factor of ~4.