Giant enhancement of second harmonic generation efficiency from monolayer group-VI transition metal dichalcogenides embedded in 1D photonic crystals

In this study, an effective numerical method wasused to describe NLO impacts on photonic crystal structures,particularly 2D TMDCs and three-dimensional (3D)materials (air and SiO2). Moreover, the amplification of thesecond harmonic (SH) efficiency in one-dimensional (1D)photonic crystals, including TMDCs, was investigated. Thesephotonic crystal structures comprise of air, SiO2, and TMDClayers that are periodically arranged; however, the first twolayers have the same thickness. The transfer matrix methodwas applied to calculate the SH efficiency and no-reductionfield approximation. The incident wavelength λ of 810 nmwas achieved by adjusting the thickness of the air and SiO2layers. In addition, by choosing a specific thickness, theharmonic waves generated in the structure interactedconstructively. The conditions were such that both thefundamental and the SH waves lay in the edge of the bandgap, where the density of electromagnetic modes andinteraction time increased. However, density ofelectromagnetic modes and interaction time interactionenhanced the efficiency of the SH efficiency.