FDTD Simulation

The simulations were performed using commercial software packages Lumerical FDTD⁴⁴ unless otherwise specified. Normal incidence of polarized plane-wave light was used as a source to irradiate the designed structure to mimic the experimental setup with laser excitation. The reflectance spectra and electric field distribution were recorded simultaneously. Perfect matched layers (PML) were applied at the x- and y- boundaries for 6 × 3 units of double spacing and 6 × 6 units of equal spacing Au NC array coupled structures. PML were also applied at the z boundaries. The thickness of the MoS₂ was taken to be ~0.7 nm. An additional mesh size of 0.01 nm for the MoS₂ layer region was utilized making sure that enough mesh points are present inside the material. For the E-field intensity distribution⁴⁴ calculations, we placed the Au array coupled ML MoS₂ in the xy-plane and the source excitation on top along the z-axis. The span of z-axis was such that the distance between the structure and top z-axis PML boundary was at least half of the maximum wavelength. Wavelength dependent complex permittivity of the materials were used to define their absorption. Lumerical FDTD simulations were performed on a Dell Precision workstation with the following components: Dual Intel Xeon E5 2650V3 processors (10 core) at 2.3 GHz and 128 GB DDR4 RAM.