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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 20 — Sep. 27, 2010
  • pp: 21169–21182

Determination of azimuthal anchoring strength in twisted nematic liquid crystal cells using heterodyne polarimeter

Tsung-Chih Yu, Yu-Lung Lo, and Rei-Rong Huang  »View Author Affiliations


Optics Express, Vol. 18, Issue 20, pp. 21169-21182 (2010)
http://dx.doi.org/10.1364/OE.18.021169


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Abstract

Two external-field-free methods are presented for measuring the azimuthal anchoring strength in twisted nematic liquid crystal (TNLC) cells. For asymmetrical TNLC samples, the twist angle is derived from the phase of the detected signal in a phase-sensitive heterodyne polarimeter and is then used to calculate the weak anchoring strength directly. The measurement resolution which is found to be about 0.01μJ/m2 makes the present method sensitive enough for the LC-based bio-sensing application. Using the proposed method, the weak azimuthal anchoring strength of a composite liquid crystal mixture (40% LCT-061153 + 60% MJO-42761) in contact with a plasma-alignment layer is found to be 7.19 μJ/m2. For symmetrical TNLC samples, the liquid crystals are injected into a wedge cell, and the two-dimensional distributions of the twist angle and cell gap are extracted from the detected phase distribution using a genetic algorithm (GA). The azimuthal anchoring strength is then obtained by applying a fitting technique to the twist angle vs. cell gap curve. Utilizing the proposed approach, it is shown that the strong anchoring strength between a rubbed polyimide (PI) alignment layer and E7 liquid crystal is around 160 μJ/m2 while that between a rubbed PI alignment layer and MLC-7023 liquid crystal is approximately 32 μJ/m2.

© 2010 OSA

OCIS Codes
(120.2130) Instrumentation, measurement, and metrology : Ellipsometry and polarimetry
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(120.5060) Instrumentation, measurement, and metrology : Phase modulation
(160.3710) Materials : Liquid crystals

ToC Category:
Instrumentation, Measurement, and Metrology

History
Original Manuscript: June 21, 2010
Revised Manuscript: September 5, 2010
Manuscript Accepted: September 14, 2010
Published: September 22, 2010

Citation
Tsung-Chih Yu, Yu-Lung Lo, and Rei-Rong Huang, "Determination of azimuthal anchoring strength in twisted nematic liquid crystal cells using heterodyne polarimeter," Opt. Express 18, 21169-21182 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-20-21169


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