Electrically switchable optical vortex generated by a computer-generated hologram recorded in polymer-dispersed liquid crystals

Y. J. Liu; X. W. Sun

doi:10.1117/12.760327

29 January 2008 Electrically switchable optical vortex generated by a computer-generated hologram recorded in polymer-dispersed liquid crystals

Y. J. Liu, X. W. Sun

Author Affiliations +

Proceedings Volume 6911, Emerging Liquid Crystal Technologies III; 69110M (2008) https://doi.org/10.1117/12.760327
Event: Integrated Optoelectronic Devices 2008, 2008, San Jose, California, United States

Abstract

Photopolymerization offers a single-step and rapid formation of different kinds of structures in polymer-dispersed liquid crystals (PDLCs) for various applications. Here we investigate the fabrication of a computer-generated hologram in PDLCs to generate an electrically switchable optical vortex. First, a computer-generated hologram was numerically designed and then transferred to a transparency as a photomask. The photomask has an effective area of 1 × 1 cm² with a resolution of 25 μm and a pattern containing almost parallel lines with a fork-like bifurcation at the vortex core. Then the photomask was clipped onto a cell filled with PDLC materials, and subjected to a collimated Ar⁺ laser (514.5 nm) beam. The intensity impinged on the photomask was about 12 mW/cm². The optimal exposure time was 2 min in our experiment judged from the fading of the photoinitiator (rose bengal) color. Due to the photopolymerization induced phase separation between polymer and liquid crystal, an index modulation was formed between the polymer-rich and liquid crystal-rich regions. The structures inside the cell were examined under an optical microscope. A good optical vortex beam with high fidelity was reconstructed using a collimated He-Ne laser beam (543 nm). The diffraction efficiency was estimated to be about 13 - 17%. With a suitable voltage applied, the reconstructed optical vortex beam can be switched due to the index change between the polymer and liquid crystal. The experimental results show promising applications of PDLC materials in optical trapping.

Citation Download Citation

Y. J. Liu and X. W. Sun "Electrically switchable optical vortex generated by a computer-generated hologram recorded in polymer-dispersed liquid crystals", Proc. SPIE 6911, Emerging Liquid Crystal Technologies III, 69110M (29 January 2008); https://doi.org/10.1117/12.760327

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