Fig. 4

Generation of THF GPs on the GSSDG. a The NEFI for the structure with (red line) and without (blue line) grating normally illuminated by CW light with the power density of 0.11 MW/cm² and the central wavelength of 28.62 μm. The two peaks in the red line denote the FF GPs (λ = 28.62 μm) and the generated THF GPs (λ = 9.54 μm), respectively. b The distribution of the real part of E_y for the generated THF GPs. The black dashed line in b represents the outlines of the silicon layer. The structural parameters of GSSDG are the same as those in Fig. 3