Description
This work extends the frequency range of SFS from mid-infrared to the THz range, serving as a surface/interface specific nonlinear spectroscopy covering the whole new THz gap of (5~15) THz. Making use of the desktop-size, broadband THz source based on diamond and designing a 5-step filtering scheme, the SF signal between THz and visible beams can be generated, separated and detected successively. Tests conducted on samples including Au, anatase, $\alpha$-quartz and thiol SAM justifies the wide applicable range, precise peak position identification and monolayer sensitivity of the system. Our setup paves the way for studying the responses, dynamics and couplings of unique elementary excitations residing in THz range.
