Chiral‐Gain Photonics

Abstract This work presents an exploratory study of the potential applications of electrically biased materials that possess a nonreciprocal and non‐Hermitian electromagnetic response analogous to the electronic response of field‐effect transistors. The most distinctive feature of such materials is their chiral‐gain, meaning that their response can be active or dissipative depending on the handedness of the wave polarization. It is shown how the chiral‐gain can be harnessed to develop novel electromagnetic devices with unique properties such as chiral lasers, polarization‐dependent mirrors, and coherent‐perfect‐absorber lasers. Furthermore, it is demonstrated that materials with chiral‐gain can bypass a reciprocity constraint that typically limits the external coupling strength, thus facilitating the excitation of cavities with extremely large quality factors.