Fabrication of liquid-crystal retarders for solar polarimetry: A facile method

Abstract

A high-precision polarimeter for simultaneous multi-line spectropolarimetric Sun observations is under development at Indian Institute of Astrophysics. Towards this end, we plan to use liquid-crystal retarders as the polarization modulators. A prototype liquid-crystal variable retarder (LCVR) is fabricated and characterized. A solution-processed method is adapted to fabricate the LCVR using commercially available E7 nematic liquid-crystal material. Thickness of the alignment layer of the LC retarder was optimized to achieve uniformity. The fabricated LCVR demonstrates spatial uniformity of retardance comparable to a commercial waveplate. The device is found to have a low-range of operational voltage of <20 V and a very short response time of <1 ms. Also, the device shows consistent operational stability.