Mode-locked surface-emitting semiconductor lasers for gigawatt peak power and gigahertz pulse repetition frequency

03.06.2014, 14:00

Prof Anne Tropper, Physics and Astronomy, University of Southampton, UK

My talk will describe recent advances in the generation of picosecond and sub-picosecond pulses at repetition frequencies in the 1 - 175 GHz range from vertical-external-cavity surface-emitting semiconductor lasers (VECSELs). The gain structures use optically-pumped InGaAs quantum wells that emit at 1 µm. Passive mode-locking is established by a separate quantum well semiconductor saturable absorber mirror (SESAM) in the external cavity, typically generating near-transform-limited pulses. Optically-pumped VECSELs combine high output beam quality with the potential for power scaling: average power of more than 100 W has been demonstrated in continuous-wave operation. My group has reported the highest peak power recorded to date from a mode-locked semiconductor laser, at 4.35 kW, corresponding to a mode-locked train of 400-fs pulses, with average power 3.3 W, at a pulse repetition frequency (prf) of 1.67 GHz. We have also shown broad band tuning of prf, from 2.78 - 7.87 GHz, in a VECSEL with mechanical adjustment of the cavity length. In harmonic mode-locking it has been possible to demonstrate a source emitting 400-fs pulses at a prf of 175 GHz. I shall discuss some potential applications for these versatile high repetition frequency pulse sources, including the generation of heralded single photons.