Enhancing Fiber-Coupled Thermal Emission Collection Using IR Plasmonic Coating

With the continued effort to make technology smaller, it has become increasingly important to study nanoscale thermal imaging. However, current thermal imaging collection methods that utilize near-field emissions such as Near-Field Scanning Optical Microscopy have a low collection efficiency with their optical probes. To improve this collection efficiency for a thermal signal, we employ a plasmonic collection method in which the fiber probe is coated with a metallic material with a plasmonic resonance that can be tuned to the infrared region, titanium nitride (TiN). The TiN was deposited onto an etched fiber at room temperature using RF sputtering. The amplification of thermal signals was tested by the heating of coated etched optical fibers within a mini furnace. Signals were collected by coupling the fiber to an optical spectrum analyzer. TiN thin film coating deposited at room temperature enhances collection efficiency of the thermal signal, but less so than that of reference tests done using a gold thin film coating. The ellipsometry measurements of room-temperature deposited TiN thin film indicate that high-temperature deposition of the TiN could tune the resonance further to the infrared for greater collection efficiency.