GaSb-based optically pumped semiconductor disk lasers emitting in the 2.0-2.8 µm wavelength range

Abstract

In recent years, optically pumped semiconductor disk lasers (OPSDLs) have attracted increasing interest due to their capability of delivering simultaneously high output power and excellent beam quality. Here we report on group-III-Sbbased OPSDLs allowing to cover the wavelength range around and above 2 μm. First the current state-of-the-art and recent progress for OPSDLs emitting in the 2.0-to-2.3 μm spectral range is presented, which includes power scaling through the use of multiple gain elements and as well as spectral tuning and line width narrowing, exploiting in both cases the versatility of the external cavity concept. Then, results on III-Sb-based OPSDLs emitting at 2.8 μm with a cw output power of up to 0.12 W and a peak output power in pulsed mode of >0.5 W, both data referring to roomtemperature operation, are presented. In both cases, the active region of the OPSDL chip consists of compressively strained GaInAsSb quantum well (QW) layers embedded between AlGaAsSb barrier and pump-light-absorbing layers. The emission wavelength is controlled by adjusting the composition of the quaternary QW material. The active region is grown on top of an epitaxial GaSb/AlAsSb Bragg mirror. For efficient heat extraction, SiC intra-cavity heat spreaders were bonded to the surface of the cleaved laser chips. An N-shaped resonator with one OPSDL chip acting as an end mirror and the second OPSDL chip as a folding mirror was used for power scaling, while a V-shaped resonator configuration with a birefringent tuner inserted into the collimated beam path of the resonator was employed for wavelength tuning. Optical pumping was achieved by standard fiber-coupled diode laser modules emitting at 980 nm.