The helicity of Raman scattered light: principles and applications in two-dimensional materials

Raman spectroscopy has been not only a technique for characterizing the composition and lattice structure of materials, but also a platform to explore the electron-photon and electron-phonon couplings. When excited by circularly polarized light, the Raman scattered light can carry a spin angular momentum ± ħ , which adds a new degree of freedom to study the Raman scattering process. This review explains the principles of the helicity of Raman scattered light excited by circular polarization, and introduces the recent advances in the fundamentals and applications of helicity-resolved Raman scattering in two dimensional (2D) materials, including the assignment of overlapped Raman modes, the characterization of exciton-phonon coupling and the application in chiral optics. We hope that this review will give a comprehensive understanding of the helicity selection rule in the Raman scattering process and inspire more exploration on the applications of the helicity of Raman scattered light.