npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041
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Article

Research Paper

New Physics: Sae Mulli 2016; 66: 223-230

Published online February 29, 2016 https://doi.org/10.3938/NPSM.66.223

Copyright © New Physics: Sae Mulli.

Analysis of the Optical Properties of Right-handed and Left-handed Cholesteric Liquid Crystals by Using Coupled Wave Theory

결합 파동 이론에 의한 좌선성 및 우선성 콜레스테릭 액정의 광학 특성 분석

Chang Min PARK, Gun Yeup KIM, Chong Hoon KWAK*

Department of Physics, Yeungnam University, Gyeongsan 38541, Korea

Correspondence to:chkwak@ynu.ac.kr

Received: December 14, 2015; Revised: January 29, 2016; Accepted: January 30, 2016

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We investigate the optical polarization properties of right- and left-handed cholesteric liquid crystals (RH-CLC and LH-CLC), which are composed of dextrorotatory (R1011) or levorotatory (S811) chiral dopants in a host nematic liquid crystal (ZLI3462).  By adopting the coupled wave theory, we present the analytic formulae for the transmittance and the reflectance in a selective Bragg diffraction region, and our comparison of the results with experimental data showed good agreements. The central wavelengths of the Bragg diffraction region were found to be blue shifted with increasing doping concentration, irrespective of dextrorotatory and levorotatory chiral dopants. The estimated helical twisting powers of the chiral dopants are $\beta(R1011)$ $\simeq$ 42.3 wt%$\mu$m$^{-1}$ and $\beta(S811)$ $\simeq$ 10.0 $\pm$ 0.5 wt%$^{-1}\mu$m$^{-1}$.

Keywords: Cholesteric liquid crystal, Coupled wave theory, Chirality, Birefringence

네마틱 액정 (ZLI3462)에 각각 우선성 (R1011)과 좌선성 (S811) 카이랄 도펀트로 구성된 우선성 및 좌선성 콜레스테릭 액정의 편광 특성을 연구하였다. 결합 파동 이론으로부터 선택적 Bragg 회절 영역에서 투과율과 반사율에 대한 해석 해를 구하고 실험결과와 비교하여 좋은 결과를 얻었다. 좌선성과 우선성 카이랄 도펀트의 종류와 무관하게 카이랄 도펀트의 양이 증가할수록 Bragg 회절 영역의 중심 파장이 청색편이 (blue shift)하였다. 구한 카이랄 도펀트들의 나선 회전력은 $\beta(R1011)\simeq$ 42.3 wt%$\mu$m$^{-1}$와 $\beta(S811)\simeq$ 10.0 $\pm$ 0.5 wt%$^{-1}\mu$m$^{-1}$이다.

Keywords: 콜레스테릭 액정, 결합 파동 이론, 키랄성, 복굴절

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