Thermal signal dependence on the probe height in the passive THz near-field microscope

Abstract

Our passive THz near-field microscope probes thermally excited surface waves with nanoscale resolution from room temperature object. When a probe is separated from the sample surface, near-field components decay within several 10 nm, whereas standing wave components occur at a height of more than 1 μm. This finding is interesting because our microscope does not use any external coherent source. Here we report theoretical and experimental analyses of localized near-field components and the standing wave components.