Optica 3, 844–852 (2016)

For semiconductor disk lasers there is a trade-off between the shortest pulse duration and the highest achievable pulse peak power. Now, Dominik Waldburger and colleagues from ETH Zürich in Switzerland have designed a vertical external-cavity surface-emitting laser (VECSEL) that uses a semiconductor saturable absorber mirror (SESAM) for mode-locking and offers significantly improved performance. The device emits 96-fs-long pulses (with external compression) at a rate of 1.6 GHz and a peak power of 560 W. The laser featured a simple V-shaped cavity with the output coupler and the SESAM at each end. The laser was optically pumped with 21 W of power from an 808-nm diode laser. The layer structures of the GaAs-based VECSEL were designed to have a large gain saturation fluence and a slightly positive but flat group delay dispersion over a large gain bandwidth. Numerical simulations suggest that the optical spectrum could support transform-limited pulses as short as 65 fs if higher-order dispersion compensation was employed.