Fig. 4: SHG characterization of the PdSe2 flakes.
From: Giant nonlinear optical activity in two-dimensional palladium diselenide
a The SHG intensities excited at various wavelengths from 780 to 1000 nm, represented by different colors. The highest intensity appeared at the wavelength of 440 nm, manifesting the strongest SHG signal of excitation at 880 nm. b The excitation power dependence of SHG intensities in 4 L PdSe2. Both axes are shown on the log scale. The correlation of the pump power and SHG intensities exhibits was linear with a slope of 1.9 ± 0.12. c The SHG signal excited at the fixed wavelength of 880 nm in 1–8 L PdSe2. The integrated intensity of SHG varied with different layers, represented by the blue dots. The SHG signal was the strongest in the 4 L sample. The inset represents the SHG intensities versus the layer numbers of PdSe2. d The purple dots indicate the polar plot of integrated SHG intensities excited by the 880 nm laser in 4 L PdSe2. The corresponding fitting result is denoted by the solid red curve.
