Abstract

Compact, long-lived, and efficient visible-light sources with coherent radiation have been required for high-density optical disk systems. Much attention has been attracted by second harmonic generation (SHG) in a diode-pumped Nd:YAG laser in which a nonlinear optical crystal KTiOPO₄ (KTP) is placed within a laser resonator. However, there is a serious problem, called “green problem,”¹ that low-frequency noise is inherent arising from the mode coupling due to sum-frequency generation in the nonlinear optical crystal.

© 1991 Optical Society of America