Fig. 3: Thickness-dependent optical properties.
From: Large area single crystal gold of single nanometer thickness for nanophotonics
a Measured transmittance (T) and reflectance (R) of 2DGFs (solid lines) and sputtered gold films (dashed lines) with different thicknesses on a mica substrate. b, c Nonlinear emission spectra measured from 2DGFs with various thicknesses and a 200-nm-thick sputtered gold film (b) and the thickness dependence of second-harmonic generation (SHG) and third-harmonic generation (THG) intensities from the 2DGFs normalized with those from the 200-nm-thick sputtered gold film (c) under p-polarized pulsed laser excitation (1550-nm wavelength, ~140-fs pulse width) at an incident angle of 30°. The spectra in (b) are shifted along the vertical axis for visibility. d Thickness-dependent multiphoton photoluminescence (MPPL) intensity from 2DGFs obtained under p-polarized pulsed laser excitation (800-nm wavelength, ~100-fs pulse width) at an incident angle of 30°. The inset shows the measured emission spectra from 2DGFs with thicknesses of 2, 3, 6, and 30 nm. The dashed line is an exponential fit to the measured data points. e, f Optical transmission micrograph (e) of a microhole array locally etched in a 24-nm-thick gold flake (the height contrast is 15 nm) and its MPPL image (f) with the signal integrated over a 575–630 nm spectral range.
