Abstract
Wavelength, polarization and orbital angular momentum of light are important degrees of freedom for processing and encoding information in optical communication. Over the years, the generation and conversion of orbital angular momentum in nonlinear optical media has found many novel applications in the context of optical communication and quantum information processing. With that hindsight, here orbital angular momentum conversion of optical vortices through second-harmonic generation from only one atomically thin WS2 monolayer is demonstrated at room temperature. Moreover, it is shown that the valley-contrasting physics associated with the nonlinear optical selection rule in WS2 monolayer precisely determines the output circular polarization state of the generated second-harmonic vortex. These results pave the way for building future miniaturized valleytronic devices with atomic-scale thickness for many applications such as chiral photon emission, nonlinear beam generation, optoelectronics, and quantum computing.
Highlights
Wavelength, polarization and orbital angular momentum of light are important degrees of freedom for processing and encoding information in optical communication
The valley-dependent circular polarization second-harmonic generation (SHG) selection rule arises from the crystal rotational symmetry requirement for the conservation of total angular momentum during the photon-lattice interaction
By performing the circular polarization-resolved SHG spectroscopy, we observe that the valley-dependent circular polarization SHG selection rule remains almost intact off the exciton resonance at room temperature and it is not affected by intervalley scattering processes
Summary
Wavelength, polarization and orbital angular momentum of light are important degrees of freedom for processing and encoding information in optical communication. It will be exciting to explore the nonlinear optical beam generation and conversion process from a TMDC monolayer at room temperature.
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