Pulse shortening of an ultrafast VECSEL

Abstract

ABSTRACT Ultrafast, optically pumped, passively modelocked vertical external -cavity surface-emitting lasers (VECSELs) are excellent sources for industrial and scientific applications that benefit from compact semiconductor based high -power ultrafast lasers with gigahertz repetition rates and excellent beam quality. Applications such as self-referenced frequency combs and multi -photon imaging require sub -200-fs pulse duration combined with high pulse peak power. Here, we present a semiconductor saturable absorber mirror (SESAM) modelocked VECSEL with a pulse duration of 1 47 fs and 328 W of pulse peak power. The average output power was 100 mW with a repetition rate of 1.8 2 GHz at a cent er wavelength of 103 4 nm. The laser has optimal beam quality operating in a fundamental transverse mode with a M 2 value of <1.05 in both orthogonal directions. The VECSEL was grown by metal -organic vapor phase epitaxy (MOVPE) with five pairs of strain-compensated InGaAs quantum wells (QW s). The QWs are placed symmetrical around the antinodes of the standing electric field at a reduced average field enhancement in the QWs of ! 0.5 (normalized to 4 outside the structure). The modelocking results overcome the trade -off between pulse duration and peak power of the state -of-the-art threshold values of 4.3 5 kW peak power for a pulse d uration of 400 fs and 3.3 W peak power for a pulse duration of 107 fs. Keywords: Mode -locked lasers, Semiconductor lasers, Ultrafast lasers, Vertical emitting lasers.