Scientific Reports · 2021
Mid-Infrared Polarization Engineering via Sub-wavelength Biaxial Hyperbolic vdW Crystals
Authors
Saurabh Dixit, Nihar Ranjan Sahoo, Abhishek Mall, and Anshuman Kumar
Abstract
Mid-infrared (IR) spectral region is crucial in astronomy, medical diagnostics, security, and imaging due to molecular vibrational modes. Two-dimensional van der Waals (vdW) crystals such as α-MoO3 and α-V2O5 exhibit in-plane biaxial hyperbolicity in the mid-IR at room temperature. Here, we use this hyperbolic anisotropy to design lithography-free, sub-wavelength mid-IR photonic devices for polarization engineering. We demonstrate dramatic footprint reduction while maintaining high extinction ratios via thin vdW crystal films. Full-wave simulations and analytical models enable precise control of polarization rotation, ellipticity, and phase, creating miniaturized waveplates and polarizers that rival metasurfaces — offering a compact and integrable platform for IR photonics.