Near-room-temperature continuous-wave operation of multiple-active-region 1.55 μm vertical-cavity lasers with high differential efficiency

Abstract

We present completely monolithic, single-step grown, bipolar cascade vertical-cavity surface-emitting lasers at 1.55 μm with a greater-than-unity differential quantum efficiency. A typical device had a threshold current density of 1 kA/cm2, a threshold voltage of 3.2 V, and demonstrated continuous wave operation up to 8 °C. Devices smaller than 10 μm in diameter lased single mode. Active regions in our device were epitaxially stacked in three stages. This technique of multiple-active regions enabled the greater-than-unity differential quantum efficiency operation, which is essential in constructing high-efficiency microwave optical links with gain. We report the device characteristics and a model on the scaling properties of active region stacking in multiple-active-region vertical-cavity lasers.