Fig. 1: THz SERS spectroscopy.
From: Uncovering low-frequency vibrations in surface-enhanced Raman of organic molecules
a Schematic optics with 785-nm laser pre-filtered by two volume holographic gratings (VHGs) and focused onto the sample by NA = 0.8 objective. Filtering the scattered light with three notch VHGs removes the laser before the spectrometer and CCD. b Au nanoparticle-on-mirror (NPoM) confines incident laser to nm-scale gap volume, producing anti-Stokes and Stokes Raman scattering at \({\omega }_{L}\pm \nu\). Inset: height of NPoM gap set by molecular monolayer (here biphenyl-4-thiol, BPT). c Vibrational (purple) and electronic (orange box) Raman scattering processes, colours as in (a, b). d Typical SERS from BPT-NPoM (black) compared to flat gold (green). Background fits show the expected background from the electronic Raman scattering model (see text, red/blue dashed lines) and Au PL model (red/blue dotted).
