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. 2021 Mar 31;12:1995. doi: 10.1038/s41467-021-22209-w

Fig. 4. SINS and FEL s-SNOM control measurements outside NBs cavity condition.

Fig. 4

a Experimental SINS amplitude S2(ω) spectral linescan across the SnO2-NB2 crystal (t = 130 nm, w = 200 nm). Red line profile at the bottom illustrates the AFM topography profile of the NB. Vertical white-dashed lines delimit amorphous and crystalline SnO2 phases. Horizontal blue dark-dashed lines denote the volume (HPhPs) and surface (SPhPs) phonon polaritons spectral ranges. The horizontal orange dashed line indicates the cutoff frequency for this NB. b (top) Tunable THz-IR (λn) s-SNOM nano-imaging experimental scheme and FEL s-SNOM narrowband maps (bottom) of the SnO2-NB3 (t = 117 nm, w = 700 nm) for the frequencies 561 and 587 cm−1. Scale bar represents 300 nm. c Cavity cutoff frequency map for M0 modes as a function NBs thickness (t) and width (w). Isofrequency diagonal-dashed lines denote M0 mode cavity cutoff for the SnO2-NB1, -NB2, and -NB3, analyzed by SINS and FEL s-SNOM in this work.