CONSIDERATION OF ANGULAR ACCEPTANCE ANGLE IN BBO CRYSTAL ON A HIGHLY EFFICIENT 2ND-HARMONIC GENERATION

The angular acceptance angle (phase matching acceptance angle) Delta t heta in BBO crystal is theoretically calculated in milli-radian magnit ude. To satisfy a fully phase matching condition of a laser beam and o btain efficient conversion of SHG, an intracavity frequency doubled (I FD) Nd:YAP mode-locked laser with a confocal unstable resonator and a BBO crystal as an SH generator is designed. Thus, fully phase matching of an approximately ideal plane wave can be realized in BBO crystal a nd an energy conversion efficiency of 81% for SHG from 1.08 to 0.54 mu m has been achieved. The pulse durations of fundamental wave and maxi mum energy fluctuations are measured and calculated. The results are c ompared with those of a convex-antiresonant ring (ARR) unstable resona tor IFD laser. (C) 1998 Elsevier Science Ltd. All rights reserved.