Fig. 9
(Reprinted with permission from Ref. [59])
a 4-NTP SERS signal acquired through the waveguide (solid blue) and the Si3N4 background spectrum on a blank reference waveguide (dashed green). The 1339 cm−1 is used for quantifying the enhancement factor. The inset shows a characteristic peak for our Si3N4 at 2330 cm−1. b Waveguide collected SERS spectrum (solid blue) after subtracting the Si3N4 background and scaling with the coupling losses, compared to a free-space collected SERS spectrum (dashed red) acquired on the same nanotriangle section. c SERS substrate-EF (SSEF) for free-space excitation and collection compared to the signal strength using a waveguide-based measurement, acquired on multiple waveguides on two different chips.