Continuous-wave III–V micro-ring lasers with position-controlled vertical QWs laterally integrated on SOI

Minimizing the footprint and energy consumption of integrated III–V lasers necessitates tight optical confinement in all three dimensions. Limited by the small index contrast of conventional vertical epitaxy, light confinement in the vertical direction is often achieved via undercutting sacrificial layers or transferring onto foreign low-index substrates. In contrast, selective lateral heteroepitaxy enables the architecture of III–V-on-insulator and supports strong vertical mode confinement. However, lasers fabricated by this method are all limited to pulse pumping due to inadequate understanding of the gain characteristics of laterally grown vertical quantum wells (QWs). Here, we demonstrate continuous-wave (CW) III–V micro-ring lasers monolithically integrated on SOI using selective lateral heteroepitaxy. We carefully analyzed the influence of position and strain of the vertical QWs on the optical gain of micro-ring cavities and strategically placed compressive-strained vertical QWs at the field maximum of the TE ∥ mode. With effective surface passivation, we achieved CW lasing at room temperature with a low threshold of 10.1 μW and stable CW lasing up to 80°C. Our results provide a compelling solution for compact CW micro-lasers monolithically integrated on SOI.