GaSb-based high-power and high-brightness semiconductor lasers emitting at ≥2 µm

In this paper an overview of infrared semiconductor lasers, covering the 2-to-3 μm wavelength range, will be given. The (AlGaIn)(AsSb) materials family is well suited for the fabrication of quantum well (QW) based semiconductor lasers covering the 2-to-3 μm spectral range. Optically pumped vertical external cavity surface emitting lasers (VECSELs), also known as optically pumped semiconductor disk lasers (OPSDLs) are attracting considerable current interest as an alternative to edge-emitting diode lasers when a laser source with a high beam quality and small beam divergence is required. VECSELs combine a nearly diffraction limited circular output beam, which is a feature of conventional solid state lasers, with the wavelength versatility of a gain medium composed of semiconductor quantum structures. VECSELs consisting of a GalnAsSb/AlGaAsSb QW active region and a GaSb/AlAsSb distributed Bragg reflector have been demonstrated in the 1.0-to-2.8 μm wavelength range. Using a simple linear cavity, a maximum cw output power exceeding 3 W at 20°C and over 4 W when cooling the heat sink to OοC has been achieved at a lasing wavelength of 2.0 μm. The quantum efficiency reaches values of 44 % at 20°C and 49 % at OοC, which is already close to that of state of the art (AlGaln)As-based disk lasers with emission wavelengths around 1 μm.