Giant Enhancement and Directional Second Harmonic Emission from Monolayer WS<sub>2</sub> on Silicon Substrate via Fabry-Pérot Micro-Cavity
Jianwei Shi, Xianxin Wu, Keming Wu, Shuai Zhang, Xinyu Sui, Wenna Du, Shuai Yue, Yin Liang, Chuanxiu Jiang, Zhuo Wang, Wenxiang Wang, Luqi Liu, Bo Wu, Qing Zhang, Yuan Huang, Cheng‐Wei Qiu, Xinfeng Liu
Abstract
Two-dimensional transition metal dichalcogenides (TMDs) possess large second-order optical nonlinearity, making them ideal candidates for miniaturized on-chip frequency conversion devices, all-optical interconnection, and optoelectronic integration components. However, limited by subnanometer thickness, the monolayer TMD exhibits low second harmonic generation (SHG) conversion efficiency (<0.1%) and poor directionality, which hinders their practical applications. Herein, we proposed a Fabry-Pérot (F–P) cavity formed by coupling an atomically thin WS2 film with a silicon hole matrix to enhance the SH emission. A maximum enhancement (∼1580 times) is achieved by tuning the excitation wavelength to be resonant with the microcavity modes. The giant enhancement is attributed to the strong electric field enhancement in the F–P cavity and the oscillator strength enhancement of excitons from suspended WS2. Moreover, directional SH emission (divergence angle ∼5°) is obtained benefiting from the resonance of the F–P microcavity. Our research results can provide a practical sketch to develop both high-efficiency and directional nonlinear optical devices for silicon-based on-chip integration optics.