From Event: SPIE Commercial + Scientific Sensing and Imaging, 2018
All material surfaces are covered with strong infrared/terahertz (IR/THz) evanescent waves since all materials contain positive and negative charges and the charge movement generates local electromagnetic waves at finite temperature. Previous theoretical analyses suggest that the thermal evanescent waves on metals and dielectrics are strongly localized within 100 nm from the surface, the energy density is more than 10000 times higher than the one of Planck’s radiation and their spectra lie in THz regions (wavelength: 8～20 μm). Probing such spontaneous evanescent waves with nanoscale spatial resolution can visualize the local dynamics of thermal equilibrium and non-equilibrium phenomena. Recently we have developed a passive scanning near-field optical microscope (SNOM), which probes surface evanescent waves without any external illumination. The microscope consists of a confocal infrared microscope, and an ultra-highly sensitive detector, named the charge-sensitive infrared phototransistor (CSIP, wavelength range is 14.5 ± 0.7 μm). In this presentation, we first describe the development of the passive SNOM. Then we show the results obtained with the SNOM; thermal evanescent waves on metals and dielectrics, and nanoscale distribution of evanescent waves derived from non-equilibrium phenomena in two dimensional electron gas. Our SNOM should open up a new way of investigating material surfaces in general and provide a novel technique of probing local temperature/electro-magnetic field distribution.
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