Unidirectional reflection from an integrated “taiji” microresonator
Allegra Calabrese, Fernando Ramiro‐Manzano, Hannah M. Price, Stefano Biasi, Martino Bernard, Mher Ghulinyan, Iacopo Carusotto, Lorenzo Pavesi
Abstract
We study light transmission and reflection from an integrated microresonator device, formed by a circular microresonator coupled to a bus waveguide, with an embedded S-shaped additional crossover waveguide element that selectively couples counter-propagating modes in a propagation-direction-dependent way. The overall shape of the device resembles a “taiji” symbol, hence its name. While Lorentz reciprocity is preserved in transmission, the peculiar geometry allows us to exploit the non-Hermitian nature of the system to obtain high-contrast unidirectional reflection with negligible reflection for light incident in one direction and a significant reflection in the opposite direction.