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Figure 4: Simultaneous processes of SHG and SFG in hybrid spiral WSe2 plasmonic structure. (a) The schematic of simultaneous processes of SHG and SFG. (b) The spectrum collected from the hybrid spiral WSe2 plasmonic structure excited with 1064 nm and 980 nm CW laser simultaneously. (c) The spectra collected from the hybrid 3D spiral WSe2 plasmonic structure with varied 1064 nm pump power while the 980 nm laser power was fixed. (d) The corresponding signals intensities vary with the increase of the 1064 nm laser power.