Second 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 radiation of an AlGaAs diode laser oscillator amplifier system in critically phase matched LiB3O5 (LBO) and beta-BaB2O4 (BBO) crystals. The laser system emits 400 mW of single frequency 806 nm radiation in an almost diffraction limited beam. For optimum doubling efficiency the laser radiation is enhanced by a resonant external ring cavity. The nonlinear crystal 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 harmonic radiation, corresponding to a conversion efficiency of 25%. The same power was obtained in a 12-mm-long BBO crystal with a laser power of 417 mW. The measured conversion efficiencies are in good agreement with the values calculated for critically phase matched conversion in these nonlinear materials. (C) 1997 American Institute of Physics.