Fig. 2: SHG enhancement in centrosymmetric-nonlinear material/metal heterostructures.
From: Boosting classical and quantum nonlinear processes in ultrathin van der Waals materials
a The experimental and simulated SH intensity for h-BN with different thicknesses on gold films and SiO2/Si substrates. Symbols are experimental points while solid and dashed lines are nonlinear transfer matrix simulation results. Error bars represent the standard deviation of SHG values over the six maxima in the polarization-resolved measurements. The pump field in the simulation is 890 nm. All data are normalized to the value for 70 nm h-BN on gold. b SHG of h-BN on gold film under variable pumping wavelengths at 790 nm, 808 nm, 834 nm, 868 nm, 890 nm. Solid lines represent Lorentzian fits to the SHG signal spectrum. c Polar plot of h-BN SHG intensities as a function of the polarization angle of the incident laser on the same 18 nm (left) and 36 nm thick h-BN flakes (right) transferred onto a gold film and onto a SiO2/Si substrate, respectively. The corresponding experimental points are highlighted by shadowed regions in (a), where we assume that both flakes have an odd-layer structure. Solid lines represent fits to the polarization-dependent SHG response under strain.
