Compact optically controlling the emission chirality of microlasers in single subwavelength particles supporting quasi-bound states in the continuum

On-chip light sources play significant roles in the implementation of highly integrated photonic circuits. So far, the size of miniaturized semiconductor lasers is mainly limited to a few microns. Although the use of plasmonic structures based on metals can effectively reduce the volumes, there are limitations in practical applications attributed to the high ohmic loss of the metal. On the other hand, an all-dielectric structures with high refractive index can avoid the loss problem of the metal structure, which provides a new way for the realization of high-performance, miniaturized and highly integrated photonic circuits. In this work, we numerically demonstrate that in all-dielectric structures, supercavity modes, also known as quasi-bound states in continuum, with high quality factor are achievable and hence can be employed in a microlaser to reduce its footprint. This proposed structure has low radiation loss and the chirality of the laser wavefront can be easily controlled optically. Moreover, due to the existence of the quasi-BIC, these merits can be achieved with a single dielectric pillar. Therefore, our work provides a new approach to realize an ultra-small laser with orbital angular momentum.