Pico-second passively mode locked surface-emitting laser with self-assembled semiconductor quantum dot absorber

Diode-pumped quantum-well vertical-external-cavity surface-emitting lasers (DP-VECSELs) have generated high average powers with circular diffraction-limited output beams, and short pulse operation. In this type of semiconductor laser, which is simple to manufacture, both the beam quality limitations of edge-emitting diode lasers and the power restrictions of electrically pumped surface-emitting lasers are overcome. It also does not require wavelength stabilization of the pump source, compared to solid-state laser systems. The laser mode area on the chip can be ∼10⁴ times larger than the one on the facet of an edge-emitting laser, offering scope for the generation of high average power and large pulse energy. The relatively small gain saturation fluence of quantum-well lasers implies that they can be passively mode-locked at repetition rates of several gigahertz with no tendency to Q-switching. Pulsed semiconductor lasers do not generally use the broad gain bandwidth to full advantage in the generation of picosecond pulses.