Advances in power scalable, tunable, and mode-locked semiconductor disk lasers

Abstract

We present new approaches for power scaling and tunability in semiconductor disk lasers. The novel concepts allow for reduced thermal load of the gain material, increasing the threshold of rollover and extending the capability for boosting the output power without significant degradation in the beam quality. The proposed technique for power scaling of optically-pumped semiconductor disk lasers is based on the multiple gain scheme. The method allows for significant power improvement while preserving good beam quality. Total power of over 8 W was achieved in dual-gain configuration, while one-gain lasers could produce separately about 4 W, limited by the thermal rollover of the output characteristics. The results show that reduced thermal load to a gain element in a dual-gain cavity allows extending the range of usable pump powers boosting the laser output. Tunable Sb-based semiconductor disk laser operating at 2-mm is demonstrated with nearly 100 nm operation range. The maximum output is 210 mW and the 3dB tuning range spans from 1946 to 1997 nm. The wavelength tuning is based on an intracavity birefringent filter. The potential of semiconductor disk lasers for high repetition rate ultrashort pulse generation using harmonic mode-locking is also discussed. We report on optically-pumped vertical-external-cavity surface-emitting lasers passively mode-locked with a semiconductor saturable-absorber mirror. The potential of harmonic mode-locking in producing pulse trains at multigigahertz repetition rates has been explored. The results present first systematic study of multiple pulse formation in passively mode-locked VECSELs.