Fig. 1: Electric field distribution in centrosymmetric-nonlinear material/metal heterostructures.
From: Boosting classical and quantum nonlinear processes in ultrathin van der Waals materials
a Schematic of incident light distribution on gold film (left) and SiO2/Si substrate (right), showing a magnified electric field amplitude and gradient on the gold film. Inset: Illustration of the second harmonic generation (SHG) process, where two photons with frequency \({\omega }_{p}\) are combined to generate a single signal photon with frequency \({\omega }_{s}\). b Simulation results of the magnitude of pump field intensity (red) and of the gradient of electric field (blue) in a 300-monolayer hexagonal boron nitride (h-BN) flake on gold (line) and SiO2/Si (dashed line). The dark area is the substrate. c The simulation results of dipolar (green) and quadrupolar (orange) contributions to the magnitude of SHG electric field of h-BN flakes with odd number of monolayers on gold (solid lines) as well as SiO2/Si (dashed lines). Dip: dipolar; Quad: quadrupolar.
