Fig. 2: Two optical modes dominating excitation and emission paths of the WS₂-Ag hybrid nanostructure.

a The excitation path of 532 nm pump laser from nanoslits to WS₂ in the backward (BW) direction is denoted as A, the emission path from WS₂ to nanoslits in the forward (FW) direction as B₁ and the emission path from WS₂ to Si and bounced back to the nanoslits as B₂. t₁ and t₂ indicate the thickness of Al₂O₃ and SiO₂, respectively. b The BW transmittance spectra are simulated under the TE polarized light incidence for the excitation path A, i.e. silver nanoslits (b = 200 nm, θ = 45°) on Al₂O₃ with increasing t₁ from 10 to 40 nm, in which the resonance mode is denoted as Mode I whose electric field distribution is presented in 3D. c The FW transmittance spectra of the emission paths B₁ and B₂, i.e. silver nanoslits and Al₂O₃ (t₁ = 30 nm) without (violet curve) and with (red curve) SiO₂, respectively, are calculated for the TE polarized light incidence, the latter of which exhibits a resonance mode II whose electric field distribution is also depicted in 3D. d–g Electric fields E_xx and E_yx for resonances I and II in the xz plane cutting along the dashed lines denoted in the 3D view (b, c).