2ND-HARMONIC GENERATION OF THE OUTPUT OF AN ALGAAS DIODE OSCILLATOR AMPLIFIER SYSTEM IN CRITICALLY PHASE-MATCHED LIB3O5 AND BETA-BAB2O4

Blue 403 nm laser light is generated by frequency doubling the radiati on of an AlGaAs diode laser oscillator amplifier system in critically phase matched LiB3O5 (LBO) and beta-BaB2O4 (BBO) crystals. The laser s ystem emits 400 mW of single frequency 806 nm radiation in an almost d iffraction limited beam. For optimum doubling efficiency the laser rad iation is enhanced by a resonant external ring cavity. The nonlinear c rystal is placed at a resonator internal focus. Using a 16-mm-long LBO crystal a diode laser power of 387 mW generated 98 mW of second harmo nic radiation, corresponding to a conversion efficiency of 25%. The sa me power was obtained in a 12-mm-long BBO crystal with a laser power o f 417 mW. The measured conversion efficiencies are in good agreement w ith the values calculated for critically phase matched conversion in t hese nonlinear materials. (C) 1997 American Institute of Physics.