Fig. 1: Nonlinear optics inside a tip-enhanced NPoM cavity.
From: In-operando control of sum-frequency generation in tip-enhanced nanocavities
a Jablonski energy diagram of coherent upconversion signals for one vibrational mode of the BPT molecule (inset). b Illustration of the field distributions inside the BPT functionalized NPoM gap at the frequencies where SFG (blue) and DFG (green) occur. c, d Illustration of vibrational signals from a tip-controlled NPoM cavity in two configurations: tip out of contact (c), and tip in contact (d) with the NPoM. The molecules in the NPoM cavity, under both infrared (IIR) and visible (IVIS) illuminations, generate Stokes/anti-Stokes (S/aS), SFG and DFG vibrational signals
