Figure 4: SHG emissions from a series of double-resonant plasmonic structures.
From: Giant colloidal silver crystals for low-loss linear and nonlinear plasmonics
(a,b) SEM images of a series of nanogroove array structures with different nanogroove depths. (c) Corresponding reflection OM images of nanogroove structures acquired with an H-polarized, normal incident white light. The reflection colours of the OM images depend on the spectral positions of plasmonic resonances. (d) Corresponding white-light reflectance spectra of reflective OM images shown in c. (e) Corresponding SHG spectra of nanogroove structures shown in a excited using a 1,064 nm pulsed laser. The SHG signal is maximized when the excitation laser wavelength and the SHG emission wavelength match with the double-resonant plasmonic modes supported by the nanogroove array. The inset shows the variation of SHG peak intensity at 532 nm with respect to the plasmonic resonances (λ1) of different nanogroove structures. According to this plot, a 1.5-nm variation of nanogroove depth from the optimized depth can lead to about 10% decrease in the SHG intensity.
