Hyperbolic metamaterials (HMMs) attract increasing attentions due to their unique optical properties and offer new approaches for realizing novel functionalities in emerging photonic meta-devices. Tunable is one of the most attractive optical properties since multifunction optical devices are one of the important research directions. So far, most active HMMs working in the visible region are based on the combination of metal and phase-change chalcogenides and the performance is limited by the optical losses of phase-change chalcogenides and interdiffusion of the metals with phase-change chalcogenides. In this work, incorporating α-phase molybdenum trioxide (α-MoO3) and Au, an active and low loss HMM device is proposed in the visible region and can effectively overcome the shortcoming. A tunable plasmonic biosensor based on prism coupled α-MoO3/Au HMM is further designed by enhancing Goos–Hänchen (GH) shift, since GH shift is highly sensitive to the refractive index of the substrate. The calculated refractive index sensitivity of this proposed biosensor is of the order of 106 nm/refractive index unit. The proposed approach offers new direction for potential application in the development of the active ultrasensitive biosensor operating at visible range.

Two-dimensional (2D) materials attract wide attention due to their unique exciting physical properties, which offer new opportunities to design novel devices with enhanced or multiple functionalities. In particular, α-phase molybdenum trioxide (α-MoO3) is an emerging 2D material and exhibits strong anisotropic optical properties and low optical losses in the visible region, making it a promising candidate in tunable optical devices. Here, we proposed a tunable plasmonic biosensor based on α-MoO3/graphene hybrid architectures. By optimizing Au film thickness, the number of α-MoO3 layers and rotation angle, our proposed biosensor can achieve a high phase detection sensitivity of 1.5172 × 105 deg RIU−1 with a biosensor configuration of SF11 prism/47 nm Au/6-layer α-MoO3/monolayer graphene at the rotation angle ϕ = 60°. In addition, the proposed biosensor represents tunable phase detection sensitivity since α-MoO3 can act as a polarizer. Our approach offers a new direction in the development of tunable ultrasensitive plasmonic biosensors for label-free detection and ultralow-concentration analytes.