Uniform optical gain as a non-Hermitian control knob

Non-Hermitian optics utilizes judicious engineering of the spatial and spectral distribution gain loss in order to tailor behavior photonic systems ways that could not be achieved by modulating only real part refractive index. In this respect, a question has never been addressed is whether uniform or can also lead nontrivial non-Hermitian effects linear systems, beyond just signal amplification decay. Here, we investigate problem demonstrate application symmetric molecule (PM) reverse optical energy inside structure. For PM composed two coupled resonators, translates into changing resonators. formed through scattering defect-induced intermodal coupling ring resonator, applied gain, despite being symmetric, impose strong chirality switch direction light propagation from dominantly clockwise counterclockwise. These predictions are confirmed using both mode formalism full-wave finite-element simulations. Our work establishes different field where interesting engineered unbalancing parameter but its average value---a feature was overlooked previous works.