Fig. 2: Optical spectroscopy and THG from BIC-supporting plasmonic metasurfaces.
a Sketch of an isolated nanobump and its ordered arrays, as well as calculated intensity distribution upon excitation of the LSPR in the isolated structure (at λR = 2.54 µm) and BIC mode in the array of such structures (at λR = 1.47 µm). The following parameters of the nanobump were used for simulations: height of 0.42 µm, the base radius of 0.4 µm and pitch size of Λ = 1.2 µm. b Absorption map calculated for the aforementioned nanobump array under TE- and TM-polarized excitation for different incidence angles θ. Vertical axis is plotted as the normalized frequency Λ/λ. c FTIR spectra of several produced nanobump arrays (top solid curves), as well as corresponding dependencies of THG yield I3ω measured for each array as a function of fundamental harmonic wavelength λω (bottom dotted curves). d Comparative power dependencies of the THG signal obtained from the smooth Au film and from plasmonic metasurface under its resonant excitation (λω = λR) and at θ = 0° and 16°. e Spectra of the THG signal measured from the smooth Au film and plasmonic metasurface under its resonant excitation at θ = 0°
