Gain-momentum locking in chiral-gain media
Phys. Rev. Applied 26, 044033 – Published 9 October, 2026
DOI: https://doi.org/10.1103/8qmb-p6nk
Abstract
Conventional optical materials are characterized by either a dissipative response, which results in polarization-independent absorption, or by a gain response that leads to wave amplification. In this work, we study a peculiar class of materials with chiral-gain properties, where gain selectively amplifies waves of one polarization handedness, while dissipation suppresses the opposite handedness. We uncover a novel phenomenon, “gain-momentum locking,” at the boundary of chiral-gain media, where surface plasmons are amplified or attenuated based on their direction of propagation. This effect, driven by the interplay between spin-momentum locking and polarization-sensitive non-Hermitian responses, enables precise control over unidirectional wave propagation. Our findings open the door to the design of unidirectional photonic devices with compensated attenuation and the generation of light with intrinsic orbital angular momentum.
