Enhanced second harmonic generation of MoS₂layers on a thin gold film

Abstract

The linear and nonlinear optical properties of thin MoS2 layers exfoliated on an Au/SiO2 substrate were investigated both numerically and experimentally. It was found that the MoS2 layers with different thicknesses exhibited different colors on the gold film. The reflection spectra of the MoS2 layers with different thicknesses were calculated by using the finite-difference time-domain technique and the corresponding chromaticity coordinates were derived. The electric field enhancement factors at both the fundamental light and the second harmonic were calculated and the enhancement factors for second harmonic generation (SHG) were estimated for the MoS2 layers with different thicknesses. Different from the MoS2 layers on a SiO2/Si substrate where the maximum SHG was observed in the single-layer MoS2, the maximum SHG was achieved in the 17 nm-thick MoS2 layer on the Au/SiO2 substrate. As compared with the MoS2 layers on the SiO2/Si substrate, a significant enhancement in SHG was found for the MoS2 layers on the Au/SiO2 substrate due to the strong localization of the electric field. More interestingly, it was demonstrated experimentally that optical data storage can be realized by modifying the SHG intensity of a MoS2 layer through thinning its thickness.

Nonlinear optics of two‐dimensional transition metal dichalcogenides

“…173 Zeng et al demonstrated that SHG of few layers MoS 2 can be enhanced by simply placing MoS 2 on a gold film. 172 They found that F I G U R E 6 A, SHG mapping of monolayer MoS 2 . 160 Copyright 2018, American Chemical Society.…”

“…Copyright 2016, American Chemical Society. D, Au film‐enhanced SHG of few layers MoS 2 . Copyright 2015, The Royal Society of Chemistry.…”

“…SHG intensity is proportional to the fourth power of the local field enhancement . Zeng et al demonstrated that SHG of few layers MoS 2 can be enhanced by simply placing MoS 2 on a gold film . They found that SHG was strongest when the thickness of MoS 2 was around 17 nm, in sharp contrast to TMDs on the silicon substrate where the monolayer exhibited a strongest SHG.…”

“…168 The ability of enhancing light-mater interaction motivates researchers to incorporate those optical cavies to layered TMDs. Recently, TMDs were integrated to various cavities such as the waveguides, 67 photonic crystals, [169][170][171] and plasmonic resonators [172][173][174][175] to enhance their nonlinear performance.…”

Two-Photon Luminescence and Second Harmonic Generation of Single Layer Molybdenum Disulphide Nanoprobe for Nonbleaching and Nonblinking Optical Bioimaging

“…Recently, an exceedingly large two-photon absorption coefficient (larger than that of conventional semiconductors by three orders of magnitude) and a large laser damage threshold of single layer MoS 2 island were reported [20]. SHG and third harmonic generation from single or few layers MoS 2 film were also reported [21][22][23]. MoS 2 nanosheets are expected to be NIR-excited optical nanoprobes for bioimaging.…”