Few-Layer Tin Sulfide: A Promising Black-Phosphorus-Analogue 2D Material with Exceptionally Large Nonlinear Optical Response, High Stability, and Applications in All-Optical Switching and Wavelength Conversion

As an analogue compound of black phosphorus, a new 2D semiconducting few-layer SnS is successfully synthesized, and its nonlinear optical response is investigated. It is shown that its nonlinear refractive index and third-order nonlinear susceptibility are measured as n(2) approximate to 10(-5) (cm(2) W-1) and chi((3))(monolayer) approximate to 10(-10) (e.s.u.), respectively. By taking advantage of such a large Kerr nonlinearity, an all-optical switching technique based on few-layer SnS is realized through modulating the propagation of the signal beam by another controlling beam. The achievement of all-optical switching indicates that few-layer SnS could be developed as an excellent optical material for all-optical signal processing. More importantly, a conceptually new and reliable information conversion system based on spatial cross-phase modulation in few-layer SnS, that is, the transmission and conversion of a sequence of bit information from one wavelength channel to the other, is presented. The contributions reveal potential applications of few-layer SnS as a new type of optical information material, and it is therefore anticipated that SnS and other IV-VI compound-based 2D nanomaterials could find promising applications in photonic devices such as optical modulators, optical switches, detectors, etc.