Fig. 5
(Reprinted with permission from Ref. [53])
Maximized volume enhancement factor (VEF) with the optimal WG length for the case of in-plane excitation and forward scattered signal collection (see Fig. 1), as a function of wavelength for the Ag plasmonic slot WG (PSW) with gap width g = 50 nm, and other WGs obtained by a varying the gap width g: Ag PSW with gap width g = 100 and 20 nm, b varying the metal filling fraction fm: Ag-Si3N4 HM slot WG (HMSW) with fm = 0.8 and 0.5, and c changing the WG type: Ag-Si3N4 hybrid plasmonic slot WG (HPSW) and Si3N4 dielectric slot WG (DSW). The results here are based on comparing to a reference Gaussian beam focused using an objective lens with NA = 0.75 that has a waist diameter D0 ≈ 1.28 μm and depth of focus b ≈ 17.4 μm. Note that changing the Gaussian beam parameters will simply scale the VEF. Each marker indicates a specific Stokes or anti-Stokes wavelength corresponding to one of the Raman modes. The vertical dotted line indicates the pump wavelength at λ0 = 785 nm.