Abstract
Abstract Mid-infrared (MIR) photonics has attracted tremendous interest because of its broad applications at atmospheric windows. In this work, we report high-performance MIR photonics based on large-scale and good-quality monolayer molybdenum disulfide (MoS2). The open-aperture Z-scan measurement on the nonlinear saturable absorption features shows that the as-grown monolayer MoS2 possesses a modulation depth of 26% and a low saturable intensity of 271 kW/cm2, enabling its application as an excellent saturable absorber for the MIR pulse generation. This is further evident by the measured high effective nonlinear absorption coefficient β eff (−16 cm/MW). In addition, the two-photon absorption coefficient and the nonlinear refractive index of monolayer MoS2 are also determined by the closed-aperture Z-scan technology. As an application, we demonstrate a passively Q-switched Tm,Ho:CaLu0.1Gd0.9AlO4 (Tm,Ho:CLGA) disordered crystal laser at 2.1 μm by using the monolayer MoS2 as the saturable absorber for the first time, producing a minimum pulse width of 765 ns and a pulse repetition rate of 36 kHz. Our results demonstrate that large-scale monolayer MoS2 is a promising candidate for the MIR photonic applications.
Highlights
The mid-infrared (MIR) spectrum ranging from 2 to 20 μm has diverse applications such as bio-photonics and medical photonics, absorption spectroscopy, environmental monitoring and security, and free-space communications [1]
Our results demonstrate that large-scale monolayer MoS2 is a promising candidate for the MIR photonic applications
We have demonstrated the application of large-scale monolayer MoS2 for the MIR photonic applications
Summary
The mid-infrared (MIR) spectrum ranging from 2 to 20 μm has diverse applications such as bio-photonics and medical photonics, absorption spectroscopy, environmental monitoring and security, and free-space communications [1]. In comparison with the previous results shown, the monolayer MoS2 thin film used in our work exhibits stronger nonlinear optical response, such as larger modulation depth and lower saturation intensity. This indicates that the as-grown monolayer MoS2 by the PVD method could be a potential saturable absorber for Q-switched lasers around 2 μm. In comparison with the few-layered MoS2, the monolayer MoS2 possesses more point defects because of the stronger quantum confinement effect caused by size reduction and more nonstoichiometric ratio These point defects including atomic vacancy defects and antisite defects will form a large number of defect energy levels, which may result in a strong nonlinear SA to mid-infrared lasers. The nonlinear refractive index n2 of monolayer MoS2 at 2 μm is −25 ± 0.6 × 10−4 cm MW−1
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