Passively mode-locked diode-pumped surface-emitting diode laser

We demonstrate to our knowledge the first passively mode-locked surface-emitting semiconductor laser. We used a 3-W high-brightness diode laser as pump source and a semiconductor saturable absorber mirror (SESAM [1,2]) as modelocker. The laser generates two stably mode-locked output beams with 11 mW average power each, 26ps pulse duration, and a repetition rate of 4.4 GHz. In contrast to edge-emitting semiconductor optically pumped semiconductor vertical external cavity surface emitting lasers [OPS-VECSELs) allow one to scale up the mode area in order to generate a high average power and high pulse energies, while the external cavity enforces a diffraction-limited output. A diffraction-limited output with >0.5 W in cw operation has been demonstrated for a similar kind of device [3]. Thus our concept promises to be scalable to much higher average and peak powers than can be obtained from electrically pumped surface-emitting mode-locked diode lasers or from edge emitting diode lasers. Only synchronously pumped surface emitting semiconductor lasers have generated pulses with high average power and pulse energy, but these require a powerful pulsed pump source [4]. Compared to mode-locked laser based on ion-doped crystals or glasses. mode-locked semiconductor lasers can generate high repetition rate (multi-GHz) pulse trains without Q-switching instabilities [5]. Their broad amplification bandwidth is sufficient for pulse durations in the femtosecond regime.