Metasurface-integrated microring resonators for off-chip vortex beam generation

Vortex beams that carry orbital angular momentum (OAM) have garnered significant attention, as they bring the degree of freedom of OAM to modern optical communication, beyond the traditional degrees of freedom such as amplitude, phase and polarization. Meanwhile, metasurfaces composed of ultra-thin layers of subwavelength structures have also been utilized for light manipulation. Nevertheless, the combination of these two concepts has not been explored in the form of microring resonator-based light emitter. In this work, we demonstrate a Si-based, passive, conjugate symmetrybreaking emitter in numerical simulation. This broken conjugate symmetry enables the emitter to generate OAMs with different topological charges, when it is driven at two opposite input directions.