Ultralow-threshold dual-wavelength optical bistability from a perovskite hyperbolic metasurface and its application in a photonic neural network

In a hyperbolic metamaterial or metasurface (HMM or HMS), strong light-matter interaction occurs at the phase transition wavelength where the material behavior changes from metal to dielectric. As a result, the enhanced electric field can generate non-linear phenomena, such as optical bistability. In this work, we numerically investigate polarization-dependent dual-wavelength optical bistability from perovskite HMS consisting of alternating layers of MAPbBr 3 perovskite and Au. Benefiting from the anisotropic property, the bistable operation wavelength for TE and TM polarizations are different. In particular, for TE polarization, strong light matter interaction resulting from the increment of incident light power not only shifts the phase transition wavelength but also enhances the transmission. Consequently, the bistable on-off contrast ratio is unprecedentedly enlarged. For TM polarization, strong light-matter interaction gives rise to an ultra-low bistable threshold. The proposed optical bistable states can serve as an activation function for optical neurons in a photonic neural network, with similar prediction accuracy across a variety of learning tasks as the classic activation functions ReLU and Sigmoid. Our work suggests a novel avenue towards the insertion of perovskite HMS into optical computing networks.