Ultralow-threshold single-mode quantum-dot laser operating at Oband based on bound-states in the continuum

Light sources for generation of optical angular momentum (OAM) are popular on telecommunication systems and in demand for key telecommunications platforms, including on-chip ultra-compact integrated communication systems, free-space optical communica-tion and optical fiber networks. Here, we demonstrate an ultralow-threshold laser based on optical bound states in the continuum (BICs), which serves as an ideal light source for generation of beams with OAM. In this context, given semiconductor material stability and robustness, the proposed BIC laser, comprising an InAs/GaAs quantum-dot (QD) active region and lasing at a wave-length of ~1.3 μm, is characterised by a power threshold of 7.5 μW (0.038 kW/cm²) at room temperature. Moreover, our experimental measurements and computational analysis of the generated optical field reveal the vortex nature of the optical beam, as well as its non-trivial topological properties. This work demonstrates an energy-efficient, stable, and versatile single-mode QD BIC laser, which, as a source of optical vortex beams with large light extraction efficiency, offers great potential to facilitate high-capacity data transmission in future optical communi-cation systems.