Circularly polarized optical vortices are known to possess spin and angular momenta dependent on the degree of circular polarization and topological charge. And it is expected to rotate when circularly polarized optical vortices are irradiated on nanoscale materials possessing electric susceptibility. This phenomenon can be understood from the time average of optical Lorentz force and when applying the electromagnetic field of arbitrary optical vortex, the direction of rotational force is not dependent on the frequency of incident light that has been confirmed by previous studies. Therefore, the rotational force can be induced by white light with common rotation axis. And it means that can convert sunlight into circularly polarized optical vortices, which has the merit of being an increase in light intensity and renewable energy. In addition, if it is possible to exert rotational motion on the object only by light irradiation, it is possible to rotate a nanoscale gear without requiring an electric circuit. In this study, in order to generate a white light optical vortex with circular polarization, a computer generated hologram (CGH) with structural birefringence was fabricated by electron beam lithography. The CGH exhibits a beam splitting property, in which arbitrary polarized light is split to a transparent light and two diffracted beams with mutually opposite handedness. By extracting a diffracted beam, a circularly polarized white light optical vortex beam was obtained. And the interaction between the generated optical vortex and a matter is investigated.
Ryotaro Suzuki, Hiroshi Nagayama, and Daisuke Barada, "Spin and orbital angular momentum control of polarized optical vortex beams using a computer-generated hologram with structural birefringence (Conference Presentation)," Proc. SPIE 10549, Complex Light and Optical Forces XII, 105490I (Presented at SPIE OPTO: January 31, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2291623.5751542199001.
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