Ring cavity enhanced second harmonic generation of a diode laser using LBOcrystal

We report on a lithium triborate (LBO) second harmonic generator delivering up to 6-mu W usable power at 397 nm out of 33 mW of a 794-nm diode laser r adiation. The LBO crystal is placed in an external ring cavity, compensated for astigmatism and coma, to enhance the fundamental power. Three cavity i nput couplers were tested for impedance-matching. With the best cavity, the enhancement factor of 1.5 is measured for 794-nm radiation, leading to an enhancement factor of 225 for the 397-nm beam. (C) 1998 Elsevier Science B. V. All rights reserved.