Combined molibdenum trioxide/vanadium dioxide multilayers for a new class of tunable photonic devices in the mid-infrared

In this work, we propose a strategy for developing actively tunable mid-infrared photonic devices by integrating polaritonic and phase-change materials. Specifically, we combine the anisotropic response of molybdenum trioxide (α-MoO₃) with the thermochromic behavior of vanadium dioxide (VO₂) in a large-area multilayer architecture. In order to optimize their interaction, we performed electromagnetic simulations and evaluated deposition conditions, adjusting key film parameters such as thicknesses. Based on these results, we fabricated thin-film stacks using Pulsed Laser Deposition (PLD), enabling precise control over composition and growth of large area α-MoO₃ films. The resulting structures were characterized by Fourier Transform Infrared Spectroscopy (FTIR) as a function of temperature, polarization, and incidence angle. The measurements reveal a clear modulation of α-MoO₃ phonon-polariton resonances triggered by the insulator-to-metal transition of VO₂. This thermally induced tunability of the mid-infrared optical response suggests promising applications in areas such as thermal camouflage and radiative cooling, where dynamic control of thermal emissivity is critical. Overall, our study demonstrates that combining a polaritonic medium with a phase-change layer provides an effective route toward infrared photonic components with real-time reconfigurability.