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Proceedings Paper

Experimental realization of high-efficiency switchable optical OAM state generator and transformer
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Paper Abstract

We introduce a high efficiency method to control orbital angular momentum (OAM) using a novel diffractive optical element - switchable forked polarization gratings (FPGs). We successfully fabricated the element and realized electric-optical switching of the OAM state. Unlike other approaches, this OAM manipulation requires no mechanical parts or expensive instruments. It is achieved by complex and locally periodic alignment of a nematic liquid crystal (LC) layer acting on the Pancharatnam-Berry phase. We have recently introduced fixed FPG with photo-aligned liquid crystal polymer as a highly efficient OAM state controller. We now report on our experimental implementation of electrically switchable FPGs based on liquid crystal cell. The local anisotropy is obtained by photo-alignment and liquid crystal technology. The spatial patterning is achieved by polarization holography. An applied voltage field on the cell can switch the element between an OAM generating/transforming mode and a transmissive mode. The diffraction behavior and OAM conversion behavior with respect to polarization, wavelength, and external voltage are characterized. Our current samples showed diffraction efficiency of 95% and switching time of approximately 3 ms. Because they are very efficient, thin, and easily tailored via holographic fabrication, switchable FPGs are ideal elements to implement enhanced control of OAM in high capacity information applications, among others.

Paper Details

Date Published: 14 September 2011
PDF: 9 pages
Proc. SPIE 8130, Laser Beam Shaping XII, 81300F (14 September 2011); doi: 10.1117/12.894474
Show Author Affiliations
Yanming Li, North Carolina State Univ. (United States)
Jihwan Kim, North Carolina State Univ. (United States)
Michael J. Escuti, North Carolina State Univ. (United States)

Published in SPIE Proceedings Vol. 8130:
Laser Beam Shaping XII
Andrew Forbes; Todd E. Lizotte, Editor(s)

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