Fluctuation-induced forces in systems with optical gain

We theoretically investigate quantum-fluctuation-induced forces in photonic systems with optical gain. A static bias, such as an electric field in low-symmetry materials, can induce optical gain, breaking electromagnetic reciprocity through Berry curvature dipoles and leading to chiral non-Hermitian responses. Another example is a shearing motion between slabs, previously studied in quantum friction, where energy is pumped into the system due to relative motion. We discuss how the fluctuation-dissipation relation must be modified to account for optical gain in these systems. Additionally, we explore how engineering optical gain properties can enhance and control quantum-fluctuation-induced forces.