Giant Enhancement of Second Harmonic Generation Efficiency from Monolayer Group-VI Transition Metal Dichalcogenides (WS2 and WSe2) Embedded in 1D Photonic Crystals

In this study, an effective numerical method was used to describe NLO impacts on photonic crystal structures, particularly 2D TMDCs and three-dimensional (3D) materials (air and SiO2). Moreover, the amplification of the second harmonic (SH) efficiency in one-dimensional (1D) photonic crystals, including TMDCs, was investigated. These photonic crystal structures comprise of air, SiO2, and TMDC layers that are periodically arranged; however, the first two layers have the same thickness. The transfer matrix method was applied to calculate the SH efficiency and no-reduction field approximation. The incident wavelength λ of 810 nm was achieved by adjusting the thickness of the air and SiO2 layers. In addition, by choosing a specific thickness, the harmonic waves generated in the structure interacted constructively. The conditions were such that both the fundamental and the SH waves lay in the edge of the band gap, where the density of electromagnetic modes and interaction time increased. However, density of electromagnetic modes and interaction time interaction enhanced the efficiency of the SH efficiency.