Researchers in Shanghai Institute of Optics and Fine Mechanics (SIOM) of the Chinese Academy of Sciences (CAS), carried out systematic investigation on the nonlinear absorption and integrated photonics applications of molybdenum sulfide selenide (MoSSe) nanosheets. The related research results have been published in Optics Express on Aug. 29, 2022.

In recent decades, two-dimensional (2D) materials have attracted great attention and been widely used in many fields. It is fundamental but significant to study the intrinsic characteristics and further realize the controllable modification engineering of these optical and physical properties in 2D materials. MoSSe is a ternary TMD alloy with a structure similar to MoS₂ in that a Mo layer is sandwiched between the S and Se layers. MoSSe has new physical properties such as higher lattice thermal conductivity, greater carrier mobility, and enhanced piezoelectric effects, owing to the breaking of the symmetry of the MoS₂ structure and existence of out-of-plane dipoles.

In this work, the researchers systematically investigated the wavelength and pulse duration dependence of the saturation absorption response of MoSSe nanosheets under a 380 fs pulsed laser at 1040/520nm and a 6 ns pulsed laser at 1064/532nm using an open-aperture Z-scan technique. Then the ground state and excited state absorption cross sections were calculated using fast and slow saturation models. The results show that the nonlinear optical response of MoSSe in the visible range is better than that in the near infrared range, and the nonlinear optical response in the 6ns pulse is better than that in the 380fs pulse. In addition, we design and optimize a slits waveguide modulator operating at 1550nm wavelength by combining MoSSe with an integrated photonic system. We find that Re (neff) can change 1.04×10^-3 and the loss does not change significantly, indicating that it is a phase modulator with good performance.

The systematic study of the inherent nonlinear optical properties of MoSSe nanosheets and the potential of integrated optical applications provides experimental and theoretical guidance for the development of MoSSe-based optoelectronic devices, and also provides enlightenment for the nonlinear optical testing of other 2D materials.

Figure 1. Nonlinear transmission of MoSSe dispersions depends on the incident light intensity, fitted by a fast SA model (a, b) under ns laser and a slow SA model (c, d) under fs laser. (Image by SIOM)

Article website:
https://doi.org/10.1364/OE.465566