Remote Sensing of High Temperatures with Refractory, Direct-Contact Optical Metacavity

In this work, temperature-dependent optical properties of refractory plasmonic transition metal nitrides and dielectric thin films are utilized to design and realize a planar, direct-contact, nanophotonic metacavity for remote, all-optical sensing of a wide range of surface temperatures (from room temperature to above 1000oC). The proposed hybrid metacavity device integrates the plasmonic cavity with a planar metasurface that utilizes refractory material components, namely titanium nitride (TiN) and silicon nitride (Si3N4), and operates in a spectral wavelength window of 900 - 1400 nm. The unique feature of this approach is that metacativy is located directly on the hot surface while other components are kept remote. The thermally variant optical properties of the constituent materials (TiN, Si3N4) enable metacavity operation with a strong polarization-dependent resonant reflectance response. At the cavity resonance, relative amplitude variations of above 30% are detected in the temperature-dependent refl...