Abstract:We propose and experimentally demonstrate that a metasurface consisting of Pancharatnam-Berry phase optical elements can enable the full control of optical spin-to-orbital angular momentum conversion. Our approach relies on the critical interference between the transmission and reflection upon the metasurface to create actively tunable and controllable conversion with a high output via coherent control of the two incident beams.The introduced control methodology is general and could be an important step toward the development of functional optical devices for practical applications.

An approach to reversibly control the curling and unfolding of graphene hybrid materials by porphyrin interactions on the basal planes of graphene has been developed, and the curled graphene hybrid materials have enhanced photoelectrochemical and optical limiting performance.

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Spin-to-orbital angular momentum conversion and orbital angular momentum conservation in the harmonic generation process have been extensively investigated. However, very few studies have focused on the spin angular momentum (SAM) conservation in the nonlinear optical process. Herein, we investigate the SAM characteristics of the second-harmonic waves with weakly focused elliptically polarized vortex beams (EPVBs). It is shown that the chirality of the second-harmonic wave is always opposite to that of the fundamental wave. Moreover, the absolute value of SAM satisfies the conservation law in the second-harmonic process generated by weakly focused EPVBs. The results are in good agreement with the experimental observations.