Passive THz Near-Field Imaging and its Applications for Engineering

Abstract

We have recently developed a THz near-field microscope with an ultrahighly sensitive detector, CSIP (charge-sensitive infrared phototransistor). The microscope probes spontaneous evanescent field on samples derived from local phenomena and the signal origin from metals was previously revealed to be thermal charge/current fluctuations. The intensity of passive near-field signal is very well consistent with Bose-Einstein distribution, which corresponds to the sample temperature. In this study, we demonstrate nano-thermometry with the microscope by monitoring passive near-field signals on a biased NiCr pattern. The obtained signals correspond to the local temperature and the result shows that the inner side of the line curve is much brighter than outer side. It can be easily interpreted by Kirchhoff’s law. The spatial resolution is 60 nm, which cannot be experimentally achieved by any other optical thermometry. This demonstration strongly suggests that our microscope is very well suited for real-time temperature mapping of complicated circuit patterns, and others like bio-samples.