抄録
IR spectroscopy is powerful method to study structure of molecule based on vibrational spectrum. However, its application to microscope did not show large progresses so much. The largest difficulty is the lower resolution of IR microscope due to the longer wavelength of IR light, and it is limited at several μm. To overcome this limitation, we developed a novel IR microscope based on vibrational sum-frequency generation (VSFG). VSFG is a non-linear optical process and we irradiate visible and IR beams on the sample. If IR beam is resonant to vibrational mode of target molecule, VSFG signal photon whose frequency is equal to sum-frequency of the two pump beams will be strongly generated. Therefore, we can detect IR absorption of the molecule by monitoring VSFG and IR spectrum can be obtained by scanning IR wavelength. Because VSFG signal has visible wavelength, IR absorption can be imaged at the resolution of visible light (several 100 nm).
