Near-Field Optical Thermometry

Far-field optical thermometry techniques have spatial resolution limited by diffraction to the order of the radiation wavelength. We report progress on near-field optical thermometry (NFOT) that targets spatial resolution better than 50 nm. A tapered, single-mode optical fiber scans nanometers above electronic microstructures, which are heated using transient electrical currents. The fiber tip releases about 1 nW of radiation power from a steady probe laser, and the reflected radiation is used to measure the local temperature. Simultaneous electrical resistance thermometry is used to estimate the relative importance of temperature dependent optical properties of the sample and thermal expansion of the sample and tip. This work provides guidance for implementing other NFOT techniques using radiation transmission and infrared emission.