2023 Departmental Poster Competition

Polarimetry is an invaluable tool for investigating material properties under the influence of polarized light. Long-wave infrared polarimetry is often limited due to a lack of polarization-sensitive optical components at mid- and far-infrared (MIR and FIR). Here, we experimentally demonstrate a MIR active and highly efficient polarization-control nanostructure. We measure the polarization rotation and ellipticity induced from gold subwavelength grating structures on top of vanadium dioxide (VO2) film on silicon carbide. The proposed structure has a resonance at 840 cm-1 due to the Fabry-Perot cavity array of coupled surface plasmon-phonon polaritons. The insulator-metal phase transition of VO2 at 55C causes a 25 cm-1 resonance shift. The polarized light parallel to the grating reflects when on resonance, while the light polarized perpendicular to the grating is strongly absorbed. Off resonance, the reflected light gains an additional scattering phase and intensity from the cavity, changing its polarization. A custom, high-resolution polarimetric spectrum microscope was developed to measure the IR polarization spectra of samples as small as 100x100-micron. This work demonstrates a novel polarimetry apparatus, enabling researchers to do precise polarimetric studies of small samples at FIR wavelengths.