Plasmon-Enhanced Second-Harmonic Generation in Monolayer WS2 with Refractory Plasmonic Nanostructures

LiChien Chang^1,2*, I-Hung Ho^1,4, Jia-Wern Chen¹, Wei-Ren Syong¹, Jing-Wei Yang^1,3, Tzu-Tu Peng^1,3, Yen-Yu Wang^1,2, Xing-Hao Lee^1,2, Yu-Cheng Chu^1,2, Hye-Young Ahn⁴, Yu-Jung Lu^1,2

¹Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
²Department of Physics, National Taiwan University, Taipei, Taiwan
³Graduate Institute of Applied Physics, National Taiwan University, Taipei, Taiwan
⁴Department of Photonics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:LiChien Chang, email:r09222076@ntu.edu.tw

Monolayer Transition metal dichalcogenides (TMDs) have a giant optical second-order nonlinearity because of their broken inversion symmetry, whereas the responses are strongly limited owing to their atomic thickness. However, the low absorption of total photons in the monolayer TMDs has become a challenge in the realization of monolayer TMD-based optical devices. Therefore, it’s desired to find an approach to increasing the absorption coefficient to enhance the signals. Here, we demonstrated a plasmon-enhanced second-harmonic generation (SHG) in monolayer WS2 with refractory plasmonic nanostructures. The working mechanism is based on the localized surface plasmon resonance (LSPR), which could generate a strong electrical field that enhances the effective absorption in the monolayer WS2. We calculated the electromagnetic field of different designed structures by the finite-difference time-domain (FDTD) method. By varying the plasmonic resonance wavelength, we could study the nonlinear properties in WS2 coupled with plasmonic nanostructures to investigate the exciton-plasmon interactions under the resonant condition and vise versa. The resonant structures were designed at the exciton emission peak wavelength of WS2. In the end, we will discuss the potential applications related to the plasmon-enhanced SHG based on monolayer TMDs.

Keywords: Low-dimensional Semiconductors, Nanostructures, Plasmonics