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Proceedings Paper

Novel devices with photosensitive elements
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Paper Abstract

Liquid Crystal (LC) devices with photosensitive elements have incredible scope for creating unique photo-induced optical devices. The use of azobenzene based materials, which undergo a trans-cis isomerisation when irradiated with light of a specific wavelength, is firmly established in LC research. The trans conformation is an elongated rod-like shape, similar to LC mesogens, whilst the cis conformation is closer to a spherical (bent) shape, disrupting to the LC order. When these materials are doped into LC materials they are able to produce light induced responses, and therefore their application to photo-switchable optics and devices is undeniable. In this research paper the light induced order modification, rather than light induced reorientation, is utilized to produce an all-optical switchable laser protection device. Upon irradiation of an azo-doped LC system with a continuous, low power (0.5 mW), laser threat (λ=405 nm) the transcis photoisomerisation process is triggered. This results in the trans-cis conformal shape change, lowering of the LC order, and causing the system to switch from the LC nematic phase (transmitting between crossed polarisers) to the isotropic liquid phase (blocking/dark between crossed polarisers). The optical properties of the azo-doped LC materials have been characterized and the response time dependence on azo-dopant concentration, system temperature, and laser threat intensity is thoroughly investigated.

Paper Details

Date Published: 1 March 2019
PDF: 7 pages
Proc. SPIE 10941, Emerging Liquid Crystal Technologies XIV, 109410C (1 March 2019); doi: 10.1117/12.2515807
Show Author Affiliations
Ethan I. L. Jull, Univ. of Leeds (United Kingdom)
Helen F. Gleeson, Univ. of Leeds (United Kingdom)

Published in SPIE Proceedings Vol. 10941:
Emerging Liquid Crystal Technologies XIV
Liang-Chy Chien; Dirk J. Broer; Igor Muševič; Byoungho Lee, Editor(s)

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