Frequency Modulated Raman Spectroscopy

The coupling of plasmonic and mechanical properties at the nanoscale is of great potential for the development of next generation devices capable to detect weak forces, mass changes, minute displacements and temperature induced effects. Both the transduction of mechanical motion to the scattered light fields in term of polarization or intensity modulation and plasmon-driven mechanical oscillations have already been demonstrated. Quasi static tunable hot spots have recently been designed and applied to surface-enhanced Raman spectroscopy (SERS). Here we fabricated a plasmo-mechanical device, with a plasmonic hot spot modulated at the oscillator eigenfrequency, and demonstrated that the nonlinear modulation of polarization-dependent SERS signal from a synthetic dye can be analyzed with lock-in techniques, thus, realizing frequency modulated Raman spectroscopy.