THz spectroscopic near-field measurement for nanoscale thermal evanescent waves

Thermally excited evanescent waves generated due to local phenomena of materials is served as a local probe of temperature. The nanoscale near-field spectroscopic information of the thermally excited evanescent waves is applicable to nano-thermography or nano-chemical microscopy. In this study, we demonstrated passive-type scanning near-field optical spectroscopy (SNOS) which detects spectroscopic information of the thermally excited evanescent waves without using any external illuminations. The passive SNOS has been developed with grating-based spectroscopic optics which has over 60 % signal efficiencies. Using the developed passive SNOS, we have achieved detecting the near-field signal on SiC at several different wavelengths in the long-wavelength infrared (LWIR) range.