NOISE-REDUCTION IN A MODE-LOCKED SEMICONDUCTOR-LASER BY COHERENT PHOTON SEEDING

We have used coherent photon seeding to reduce the noise in an activel y mode-locked extended-cavity semiconductor laser. Feedback is provide d by an auxiliary cavity terminated either by a wedge plate or by a ph ase-conjugate mirror. Both conventional and phase-conjugate feedback c an reduce the low-frequency noise components (0-5 MHz) by as much as 3 6 dB, hence drastically reducing the pulse fluctuations. A noise reduc tion of as much as 18 dB is also observed in the 0.01-3.0-GHz frequenc y range, We obtained these results while preserving the pulse duration (26 ps) and improving the time-bandwidth product. (C) 1998 Optical So ciety of America.