Thermally Tuning Infrared Light Scattering Using Planar Layered Thin Films and Space Gradient Metasurface

We experimentally demonstrate a tunable planar layered thin film (PLTF) structure operating at the short-wavelength infrared spectrum by employing the phase transition of vanadium dioxide through thermal stimulus. We obtain 400-nm spectral wavelength shift of scattering resonances by heating up or cooling down the structure. This temperature change leads to a contrast in the scattering intensities so that the contrast of transmission at Fabry-Perot resonance wavelength of 1.75 μm is obtained by the numerical simulations and verified by the measurements. We add a metasurface layer on the tunable PLTF structure, and we theoretically investigate and numerically demonstrate the scattering effects of this modified design. In this case, the contrast of transmission is enhanced compared to the only PLTF design due to Mie-type scattering. We also indicate that the normally incoming infrared light passes through the proposed design with a bending angle at room temperature whereas the intensity of the bending light is not appreciable at high temperature. Thus, we have achieved the so-called thermally adjustable infrared light bending/steering. The dynamic devices based on these kinds of pure planar layered and metasurface incorporated structures can be employed in numerous active photonic applications in the infrared spectrum.