Thermo-optical properties of α-MoO3 thin films in the mid-infrared and phonon frequency shift

We investigate the mid-infrared thermo-optical properties of polycrystalline alpha-phase molybdenum trioxide (α-MoO3) thin films grown on fused silica substrates via pulsed laser deposition (PLD) at 500 ◦C. By analyzing temperature-dependent reflection spectra, we determine stable and uniquely defined MoO3 thermo-optical constants, dn/dT and dk/dT, over a 20 ◦C–250 ◦C temperature range. Unlike films grown using other deposition techniques at room temperature and subsequently annealed, our results demonstrate that PLD enables the fabrication of reliable and thermally stable MoO3 thin films, making them highly suitable for infrared applications, such as filters, polarizers, and sensors.