Metasurface lasers based on bound states in the continuum (BICs) have recently attracted significant research interest. In theory, a true photonic BIC is characterized by complete decoupling from the radiation continuum, resulting in an infinite radiative lifetime and Q-factor. Remarkably, a slight perturbation can cause a true BIC to collapse into a Fano-like resonance, forming what is known as a quasi-BIC—a mode with a very high and tunable Q-factor. Metasurfaces composed of large ensembles of unit cells supporting such quasi-BIC modes are, therefore, excellent candidates for low-threshold laser cavities.

To date, all demonstrated quasi-BIC metasurface lasers have been fabricated using conventional top-down techniques. In this project, we aim to demonstrate lasing in a bottom-up metasurface device that supports a perturbed symmetry-protected quasi-BIC mode. The unit cell of the metasurface consists of a pair of InP nanosheet structures grown via selective area epitaxy. The high sidewall facet quality of these nanosheets is expected to minimize scattering losses within the cavity, enabling ultra-low threshold lasing at room temperature.