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Proceedings Article

Electrically controlled lens and prism using nanoscale polymer-dispersed and polymer-networked liquid crystals

[+] Author Affiliations
Yun Hsing Fan, Hongwen Ren, Shin Tson Wu

School of Optics/Univ. of Central Florida (USA)

Proc. SPIE 5289, Liquid Crystal Materials, Devices, and Applications X and Projection Displays X, 63 (May 28, 2004); doi:10.1117/12.526148
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From Conference Volume 5289

  • Liquid Crystal Materials, Devices, and Applications X and Projection Displays X
  • Liang-Chy Chien; Ming H. Wu
  • San Jose, CA | January 18, 2004

abstract

Inhomogeneous nanoscale polymer-dispersed liquid crystal (PDLC) devices having gradient nanoscale droplet distribution were fabricated. This gradient refractive index nanoscale (GRIN) PDLC film was obtained by exposing the LC/ monomer with a uniform ultraviolet (UV) light through a patterned photomask. The monomer and LC were mixed at 70: 30 wt% ratio. The area exposed to a weaker UV intensity would produce a larger droplet size, and vice versa. Owing to the nanoscale LC droplets involved, the GRIN PDLC devices are highly transparent in the whole visible region. The gradient refractive index profile can be used as switchable prism gratings, Fresnel lens, and positive and negative lenses with tunable focal lengths. Such a GRIN PDLC device is a broadband device and independent of light polarization. The diffraction efficiency of the lens is controllable by the applied voltage. The major advantages of the GRIN PDLC devices are in simple fabrication process, polarization-independent, and fast switching speed, although the required driving voltage is higher than 100 Vrms. To lower the driving voltage, the technique of polymer-networked liquid crystal (PNLC) has been developed. The PNLC was also produced by exposing the LC/monomer mixture with a uniform UV light through a patterned photomask. However, the monomer concentration in PNLC is only around 2-5 wt%. The formed PNLC structure exhibits a gradient polymer network distribution. The LC in the regions stabilized by a higher polymer concentration exhibits a higher threshold voltage. By using this technique, prism grating, tunable electronic lens and Fresnel lens have been demonstrated. The driving voltage is around 10 Vrms. A drawback of this kind of device is polarization dependence. To overcome the polarization dependence, stacking two orthogonal homogeneous PNLC lens is considered.

© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Citation

Yun Hsing Fan ; Hongwen Ren and Shin Tson Wu
"Electrically controlled lens and prism using nanoscale polymer-dispersed and polymer-networked liquid crystals", Proc. SPIE 5289, Liquid Crystal Materials, Devices, and Applications X and Projection Displays X, 63 (May 28, 2004); doi:10.1117/12.526148; http://dx.doi.org/10.1117/12.526148


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