Pre-twisted hybrid LC polarization rotator with ultra-broadband and low-voltage operation

초록

We report an ultra-broadband and voltage-tunable polarization rotator based on a hybrid aligned nematic (HAN) liquid crystal cell with an intentional pre-twisted configuration. By employing a rubbing angle of-130 degrees between the planar and vertical alignment layers, an initial twist angle of-30 degrees is formed even in the absence of an external field. Applying a vertical electric field gradually lowers the polar angle of the LC molecules while preserving their azimuthal twist, thereby increasing their contribution to polarization rotation. The proposed structure achieves a continuous rotation of the polarization vector from 0 degrees to 90 degrees over a wavelength range of 200-2000 nm with a degree of linear polarization (DoLP) exceeding 0.9. Compared with previous approaches, this design operates at a significantly lower driving voltage (-10 V) and eliminates the need for patterned electrodes, enhancing its compatibility with large-area and low-cost fabrication. The optical response is supported by director simulations and Jones matrix calculations, highlighting the physical mechanisms underlying its broadband and tunable polarization control.

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