Optically self-locked semiconductor laser with servo control for feedback phase and laser current

The operating current of a semiconductor laser optically locked to a high-finesse reference cavity can be controlled using a second-harmonic lock-in technique. The authors present theoretical calculations for this novel servo scheme. For stabilization and noise reduction of semiconductor lasers, the optical lock to a high-finesse cavity with a feedback phase servo has become a standard technique. An additional servo for the laser current is desirable for combining good tuning capability and high spectral purity. It is demonstrated that such a servo can easily be established with no changes in the optical setup. The practical applicability of this technique has been demonstrated in a setup with a 780-mm laser diode