Estimation of order parameter of a liquid crystal variable retarder using Haller's approximation

Area of Science:

• Optics and Photonics
• Materials Science
• Astronomy Instrumentation

Background:

• Polarimeters for solar observations utilize liquid crystal variable retarders (LCVRs) for polarization modulation.
• LCVR retardance is sensitive to both voltage and temperature, with temperature fluctuations degrading measurement accuracy.

Purpose of the Study:

• To calibrate LCVRs concerning temperature variations.
• To investigate the temperature and voltage dependence of key liquid crystal parameters.

Main Methods:

• Calibration of LCVR retardance against temperature.
• Estimation of critical exponent (β), maximum retardance (δ₀), and order parameter (S) using Haller's approximation.
• Analysis of parameter dependence on applied voltage.

Main Results:

• LCVRs were calibrated, and critical parameters were estimated.
• The order parameter (S) exhibits a linear relationship with temperature, modulated by voltage.
• The change in order parameter with temperature varies linearly with voltage between 1-7 V.

Conclusions:

• Accurate calibration of LCVRs against temperature is crucial for precise polarimetric measurements in solar observations.
• Understanding the interplay between temperature, voltage, and liquid crystal order parameter enhances instrument stability.
• The observed linear dependence offers a pathway for real-time compensation of temperature-induced errors.