11 March 2015 Fast-response IR spatial light modulators with a polymer network liquid crystal
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Proceedings Volume 9384, Emerging Liquid Crystal Technologies X; 93840N (2015) https://doi.org/10.1117/12.2081955
Event: SPIE OPTO, 2015, San Francisco, California, United States
Abstract
Liquid crystals (LC) have widespread applications for amplitude modulation (e.g. flat panel displays) and phase modulation (e.g. beam steering). For phase modulation, a 2π phase modulo is required. To extend the electro-optic application into infrared region (MWIR and LWIR), several key technical challenges have to be overcome: 1. low absorption loss, 2. high birefringence, 3. low operation voltage, and 4. fast response time. After three decades of extensive development, an increasing number of IR devices adopting LC technology have been demonstrated, such as liquid crystal waveguide, laser beam steering at 1.55μm and 10.6 μm, spatial light modulator in the MWIR (3~5μm) band, dynamic scene projectors for infrared seekers in the LWIR (8~12μm) band. However, several fundamental molecular vibration bands and overtones exist in the MWIR and LWIR regions, which contribute to high absorption coefficient and hinder its widespread application. Therefore, the inherent absorption loss becomes a major concern for IR devices. To suppress IR absorption, several approaches have been investigated: 1) Employing thin cell gap by choosing a high birefringence liquid crystal mixture; 2) Shifting the absorption bands outside the spectral region of interest by deuteration, fluorination and chlorination; 3) Reducing the overlap vibration bands by using shorter alkyl chain compounds. In this paper, we report some chlorinated LC compounds and mixtures with a low absorption loss in the near infrared and MWIR regions. To achieve fast response time, we have demonstrated a polymer network liquid crystal with 2π phase change at MWIR and response time less than 5 ms.
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Fenglin Peng, Fenglin Peng, Haiwei Chen, Haiwei Chen, Suvagata Tripathi, Suvagata Tripathi, Robert J. Twieg, Robert J. Twieg, Shin-Tson Wu, Shin-Tson Wu, } "Fast-response IR spatial light modulators with a polymer network liquid crystal", Proc. SPIE 9384, Emerging Liquid Crystal Technologies X, 93840N (11 March 2015); doi: 10.1117/12.2081955; https://doi.org/10.1117/12.2081955
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