Fig. 3: SHG enhancement in twisted h-BN on gold film.
From: Boosting classical and quantum nonlinear processes in ultrathin van der Waals materials
a Detailed process for preparing the h-BN homostructure. It illustrates the step-by-step method used to assemble the h-BN homostructure. PC: polycarbonate. b Schematic of h-BN homostructures (blue) on gold film (yellow). A homostructure is formed by rotating the top h-BN flake relative to the bottom one by an angle. Inset: Rotation of h-BN lattice with a θ angle. c The experimental results of SHG intensity as a function of polarization angle for the homostructures on gold and SiO2/Si; AA’ stack corresponds to 0° and AB stack corresponds to 60° stacking angle. d Bright field optical microscopy image of h-BN homostructures. Red dashed line: top layer h-BN. Green dashed line: bottom layer h-BN. e SHG intensity along a closed loop including all the h-BN homostructures (AA’ and AB)/substrates(gold and SiO2/Si) combinations. Different combinations are represented by unique colors and symbols, each corresponding to the path depicted by a line of the same color in (d). The dashed lines mark the boundaries between different regions. f Summary of the enhancement factors from different areas in (d) with respect to the 0° homostructure on SiO2/Si substrates, measured at a 72° polarization angle: AB (60°) homostructure on gold; AA’ (0°) homostructure on gold; AB (60°) homostructure on SiO2/Si; AA’ (0°) homostructure on SiO2/Si. The error bars represent the standard deviation of the enhancement factor within each region.
