This talk will review our efforts to utilize phase-transition materials in mid-infrared optics and highlight relevant related literature. Materials like vanadium dioxide (VO2) and rare-earth nickelates (RNOs) undergo structural and electronic phase transitions that can be driven via thermal, electrical, and optical means. These phase transitions result in dramatic changes in electronic properties, and correspond to large changes in optical properties, especially in the mid-infrared spectral range where the Drude response dominates. Previously we have demonstrated that VO2 integrated into thin film structures enable temperature- and current-tunable absorbers and reflectors and plasmonic antennas, as well as thermal emitters with anomalous temperature dependence.

More recently, we looked to expand the palette of tunable optical materials by defect engineering VO2 to alter its properties, and by using less-studied phase-transition materials such as samarium nickelate (SNO). By combining these approaches, thermally driven phase transitions can be found over a range of critical temperatures from below room temperature to above 100 °C. We are currently demonstrating anomalous thermal emitters using SNO, which can mask the temperatures of objects from thermal imagers, and VO2-based metasurfaces with new functionalities using nanoscale defect engineering with ion irradiation.