Long-Infrared Passive Near-field Spectroscopic Imaging

Local phenomena of materials generate strongly localized electromagnetic wave, called thermally excited evanescent waves, in the long-wavelength infrared spectra range. In order to directly detect the spectroscopic information of the thermally excited evanescent wave, we have developed passive near-field optical spectroscopy (SNOS) based on grating-based spectroscopy. Using the passive SNOS, we achieved detecting the thermally excited evanescent waves on an Au/SiC micropattern sample at different wavelengths. The detected near-field signals were well consistent with the electromagnetic local density of states of SiC and Au. Passive SNOS will be a powerful tool for numerous spectroscopic applications including a surface chemical analysis.