2.7- $\mu{\rm m}$ Single-Frequency ${\rm TEM}_{00}$ Low-Threshold Sb-Based Diode-Pumped Exter

We present the design, technology, and performances of a tunable Sb-based diode-pumped type-I quantum-well (QW) vertical-external-cavity surface-emitting lasers emitting at 2.7 μm. The half vertical-cavity surface-emitting laser (VCSEL) structure was grown by molecular beam epitaxy with quantum-well growth temperature of 440 ^°C. The sample was thermally annealed to optimize the QW gain design. We report on room-temperature continuous-wave laser with 0.17-mW output power and low threshold incident pump intensity of 0.7 kW/cm² while pumping at 830 nm with a commercial diode laser. The external cavity provides a circular TEM₀₀ beam with a low divergence of 3.6^°. The short mm-long optical cavity laser exhibits tunable single frequency operation, with a sidemode suppression ratio >;>; 23dB, a linewidth <;<;4;GHz, and a linear light polarization. Thermal and optical properties are studied.