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Monday, February 15, 2016

Constructive spin-orbital angular momentum coupling can twist materials to create spiral structures in optical vortex illumination

Daisuke Barada, Guzhaliayi Juman, Itsuki Yoshida, Katsuhiko Miyamoto, Shigeo Kawata, Seigo Ohno and Takashige Omatsu

It was discovered that optical vortices twist isotropic and homogenous materials, e.g., azo-polymer films to form spiral structures on a nano- or micro-scale. However, the formation mechanism has not yet been established theoretically. To understand the mechanism of the spiral surface relief formation in the azo-polymer film, we theoretically investigate the optical radiation force induced in an isotropic and homogeneous material under irradiation using a continuous-wave optical vortex with arbitrary topological charge and polarization. It is revealed that the spiral surface relief formation in azo-polymer films requires the irradiation of optical vortices with a positive (negative) spin angular momentum and a positive (negative) orbital angular momentum (constructive spin-orbital angular momentum coupling), i.e., the degeneracy among the optical vortices with the same total angular momentum is resolved.

DOI

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