Brewster Mode‐Enhanced Sensing with Hyperbolic Metamaterial

Abstract Hyperbolic metamaterials (HMMs) are used to demonstrate extreme sensitivity biosensing by exciting their high‐ k modes. However, momentum couplers, such as subwavelength diffraction grating or bulky high‐index prism, are required to excite these nonradiative modes, which is not cost‐effective and thus not suitable for point‐of‐care applications. Here, a cost‐effective and scalable HMM‐based sensor platform is proposed and experimentally demonstrated, by exciting the Brewster mode of HMM from free‐space. The excitation of Brewster modes is shown in a multilayered HMM comprising of alternating thin layers of TiN and phase change material, such as Sb 2 S 3 . Brewster modes in the hyperbolic region occur due to abrupt phase change, and enhanced Goos–Hänchen shift is realized at the Brewster angle. The enhanced refractive index sensing is demonstrated by exploiting the singular phase of light associated with the Brewster mode of the proposed HMM. This microfluidics integrated lithography‐free nanophotonic device can be a potential sensor platform for a cost‐effective development of label‐free biosensors for point‐of‐care applications.