Low-threshold 3 µm GaInAsSb/AlGaInAsSb quantum-well lasers operating in continuous-wave up to 64 °C

Long-wavelength lasers, emitting above 2 μm, are attractive light sources for trace-gas sensing systems with tunable diode-laser absorption spectroscopy (TDLAS). Here, GaSb-based lasers are perfectly suited, as they can cover the spectral range from 2 to 4 μm. Many technologically important gases, such as CO, CO₂, CH₄, NH₃, N₂O, etc., have strong absorption lines in this region. The spectral range around 2.9 - 3.0 μm is of specific interest for NH₃ and N₂O sensing applications. In this work, we present state-of-the-art GaInAsSb/AlGaInAsSb quantum-well (QW) ridge-waveguide lasers emitting around 3 μm. Episide-up mounted devices operate in continuous wave (CW) with very low threshold current densities up to record-high 64 °C heatsink temperature. This is by ~20 °C higher, than the best reported value of 45 °C for episide-down indium-soldered devices at this wavelength range. In pulsed mode devices were operating beyond 80 °C heatsink temperature, limited only by the characterization set-up. Extrapolated pulsed threshold currents at 20 °C for infinite resonator length (L→∞) yield 168 A/cm² for 3 QW active region, corresponding to only 56 A/cm² per QW. In CW operation the extrapolated (L→∞) threshold current was found to be 198 A/cm², yielding 66 A/cm² per QW. For this long wavelength range, a very high characteristic temperature (T₀) of 43 K was determined in the temperature range of 10 to 60°C.