Dielectric Permittivity Tensor of Muscovite for Next Generation All Van Der Waals Broadband Photonic Components

<jats:title>ABSTRACT</jats:title> <jats:p> We report a comprehensive determination of the dielectric permittivity tensor of van der Waals (vdW) muscovite, also referred to as mica, establishing it as a low‐index, low‐loss platform for next‐generation nanophotonics. Resolving its anisotropic vibrational response and extracting accurate dielectric tensor components across a broad ultraviolet (UV) to near‐infrared (NIR) spectral region, we display that vdW muscovite exhibits consistently low refractive indices, negligible extinction, and weak in‐plane anisotropy, allowing its treatment as an effectively uniaxial crystal in thin‐layer limits. Leveraging these properties, we design muscovite‐based all‐vdW heterostructures pairing it with high‐refractive‐index MoS <jats:sub>2</jats:sub> , engineering few‐layer and sub‐micron‐thick distributed Bragg reflectors (DBR) and short‐pass dichroic beam splitters (DBS), operating with high efficiency, robust and broadband optical performance in the NIR spectral region. Our findings spotlight the significance of low‐index extinctionless vdW crystals, positioning muscovite as a highly perspective atomically flat building‐block for the creation of next‐generation, broadband, and scalable all‐vdW nanophotonic components. </jats:p>