Compensation for variation of a semiconductor laser threshold position is based on the utilization of the rectifying property of such lasers near threshold. A small amplitude test signal is applied to the laser close to threshold and a distortion component at a harmonic of the test signal frequency is...http://www.google.com.au/patents/US4344173?utm_source=gb-gplus-sharePatent US4344173 - Stabilization circuit for a digitally operated laser
