Ultralow-threshold cryogenic vertical-cavity surface-emitting laser

Data are presented characterizing a low-threshold vertical-cavity surface-emitting laser designed for cryogenic operation. A threshold current of 12 μA and current density of 25 A/cm² are obtained at 77 K with the low-loss cavity design. From 77 K to 160 K, the threshold increases linearly with temperature, but only approximately tracks the detuning of the cavity resonance from the minimum energy transition of the quantum well. At 77 K, we estimate that the 25-A/cm² threshold current density is about twice that required for transparency.