Observation of exceptional points in anisotropic ReS₂ microcavities

Exceptional points (EPs) are spectral singularities in non-Hermitian systems where eigenvalues and eigenvectors simultaneously coalesce. Manipulating EPs in solid-state systems typically requires complex architectures. Here, based on a hybrid system consisted of few-layer rhenium disulfide (ReS₂) deposited on a distributed Bragg mirror, we demonstrate an all-optical method to dynamically control EPs by harnessing the intrinsic optical anisotropy of ReS₂. By utilizing the incident polarization angle as a dynamic control parameter, we continuously modulate the exciton–photon coupling strength, driving the system from the strong coupling regime to the weak coupling regime. The EPs are manifested as simultaneous coalescence of the real (energy) and imaginary (linewidth) parts of the complex eigenvalues. This dual-degeneracy provides unambiguous experimental evidence for EP formation and the associated collapse of the Hilbert space dimensionality. Our findings establish anisotropic light–matter coupled systems as a robust paradigm for exploring non-Hermitian topology in photonics, enabling polarization-driven topological devices without intricate nanofabrication.