Fig. 3: Critical coupling condition for enhancing THG.
Measured (a) and calculated (b) dependencies of THG yield of the representative nanobump array (λR = 1.32 µm; Λ = 1 µm) on the pump laser wavelength and incidence angle θ under TM-polarized excitation. Markers on (b) trace the variation of the THG signal intensity versus incidence angle θ under resonant excitation λω = λR. Curves on (b) provide calculated radiative (white line) and non-radiative (green lines) decay rates of the plasmonic BIC mode versus θ. Non-radiative losses were calculated considering only the Ohmic losses derived from the optical constants of gold (green dashed curve), as well as additional losses due to fabrication defects of the array and thermally increased Ohmic losses (green solid curve)
