Broadband polarization rotation in liquid crystals: principles, twisted nematic architectures, and design guidelines

초록

Broadband polarization rotators are key optical components for applications in imaging, spectroscopy, optical communication, and emerging photonic systems. Conventional approaches based on waveplates or Faraday rotators often suffer from strong wavelength dependence, bulky configurations, or limited tunability. Liquid crystals (LCs) offer an attractive alternative owing to their intrinsic birefringence and electrical controllability. This review focuses on broadband polarization rotation in LCs, with an emphasis on twisted nematic (TN)-based architectures. The fundamental principles of polarization rotation via the waveguiding mechanism in twisted structures are first summarized, followed by a review of conventional TN configurations and their inherent limitations. Recent advances in voltage-induced TN architectures, including asymmetrically anchored planar TN cells and pre-twisted hybrid aligned nematic (HAN) cells, are then discussed. The structure-property relationships governing broadband operation, driving voltage, and polarization fidelity are analyzed, and practical design guidelines are presented. This review provides a unified framework for understanding the operating principles, structural classifications, and design strategies of broadband LC polarization rotators.

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