Researchers at ETH Zurich (Zurich, Switzerland) announced the first successful demonstration of a novel type of ultrafast laser. The passively modelocked vertical-external-cavity surface-emitting semiconductor laser (MIXSEL) has potential as a cost-effective, ultracompact source suitable for high-volume wafer-scale fabrication. The team used molecular-beam epitaxy to integrate a vertical-external-cavity surface-emitting semiconductor laser (VECSEL) with a semiconductor saturable-absorber mirror (SESAM) to achieve peak output powers of 2.1 W at 953 nm and high pulse repetition rates of up to 50 GHz. A 5.4-cm-long straight cavity and a 0.35% transmission output coupler obtained stable modelocking to deliver an average of 40 mW of power in 34.6 ps pulses at 2.8 GHz with a spectral full width at half-maximum of 0.11 nm.
As in previously demonstrated VECSEL-SESAM modelocking schemes, the output power can be improved to the multiwatt regime by growing the structure upside down before removing the substrate. The next barrier to further reduction in the size and cost of the MIXSEL, say the researchers, is electrical pumping, which if overcome would result in devices suitable for applications including telecommunications, optical clocking, and microscopy. Contact Aude-Reine Bellancourt at [email protected].
