Advancing phononic polaritons: materials and excitation strategies

This research explores the optical properties of α-MoO₃, VO₂, β-Ga₂O₃, and GaN/AlₓGa₁−ₓN heterostructures, utilizing advanced fabrication methods such as Pulsed Laser Deposition (PLD), Metal-Organic Chemical Vapor Deposition (MOCVD), and Molecular Beam Epitaxy (MBE). These materials exhibit distinctive plasmonic and phononic characteristics tailored for MIR applications. α-MoO₃ films produced via PLD showed excellent spectral properties and strong field confinement, while tungsten-doped VO₂ provided dynamic tunability through phase transitions at room temperature. Additionally, β-Ga₂O₃ thin films demonstrated significant birefringence and polarization-dependent resonances, and GaN/AlₓGa₁−ₓN heterostructures facilitated enhanced light–matter interactions through engineered band structures. Comprehensive optical analyses were conducted using Fourier-transform infrared (FTIR) spectroscopy alongside theoretical modeling with the Generalized 4×4 matrix formalism, confirming the performance and reliability of these materials. This study addresses key challenges in MIR nanophotonics, including material fabrication, device integration, and dynamic control, by taking advantage of the unique properties of each material investigated. The results contribute to the advancement of high-performance MIR photonic devices.