Figure 1: (A) Structure of the dye-labeled RNA/DNA duplex; (B)Schematic of the grating with embedded nanocavity; (C) Representativeframes from the split-channel Cy3/Cy5 FRET recordings; (D) Simulatedelectric field distribution at the nanocavity-grating interface (black dashedline indicates the level of the base of the grating); and (E) Electric fielddepth profile along the middle of the nanocavity (white dashed line in (D))