Rapid and High Sensitivity Imaging of Two-dimensional Materials by Stimulated Raman Scattering Microscopy*

Raman microscopy has been widely used to characterize phonon vibration in two dimensional materials. It enables us to gain insight into the information of sample thickness, doping and strain effect. However, Raman mapping by spontaneous Raman microscopy is often hindered by limited sensitivity and imaging speed. Here, we bring the stimulated Raman scattering (SRS) for the first time in characterizing two dimensional hexagonal-boron nitride. We found that SRS offers background free and greater sensitivity imaging than spontaneous Raman scattering (SR), second harmonic generation (SHG) and four-wave-mixing(FWM). The SRS signal shows good linearly dependence on layer number. What is more, it enables rapid imaging that is thousand times faster than SR mapping. Our result shows great potential of SRS in the study of two dimensional materials.