Electrically Tunable Fresnel Lens in Twisted-Nematic Liquid Crystals Fabricated by a Sagnac Interferometer

This paper presents an electrically tunable Fresnel lens in a twisted nematic liquid crystal cell fabricated by using a Sagnac interferometer. When the Fresnel-patterned green beam, formed by the Sagnac interferometer, is irradiated on the azo-dye doped liquid crystal mixture, the azo-dye molecules...

Full description

Saved in:
Bibliographic Details
Published in:Polymers 2019-09, Vol.11 (9), p.1448
Main Authors: Huang, Bing-Yau, Lin, Tsung-Hsien, Jhuang, Tian-Yi, Kuo, Chie-Tong
Format: Article
Language:English
Subjects:
Alignment
Alternating current
Crystal structure
Crystals
Diffraction efficiency
Dyes
Efficiency
Fresnel lenses
Glass substrates
Interferometers
Lasers
Linear polarization
Liquid crystals
Nematic crystals
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:This paper presents an electrically tunable Fresnel lens in a twisted nematic liquid crystal cell fabricated by using a Sagnac interferometer. When the Fresnel-patterned green beam, formed by the Sagnac interferometer, is irradiated on the azo-dye doped liquid crystal mixture, the azo-dye molecules undergo - photoisomerization and then generate the photo-alignment effect in the bright (odd) zones. The director of the liquid crystal molecules in the odd zones reorients the direction perpendicular to the polarization direction of the linearly polarized green beam. The various structures of liquid crystals in the odd and even zones will result in a phase difference and thus, a Fresnel lens can be generated. The experimental results show that the proposed Fresnel lens has a high diffraction efficiency of 31.5% under an applied alternating-currents (AC) voltage. The focal length of the Fresnel lens can also be tuned by thermally erasing the photo-alignment effect of the azo dyes and rewriting by a different Fresnel-like pattern.
ISSN:2073-4360
2073-4360
DOI:10.3390/polym11091448