Advance in light filtering technology has implications for LCD screens, lasers and beyond

Light waves can oscillate with their back-and-forth motion oriented along different directions, where its polarization describes the nature of this orientation. A traditional polarizer, like a lens from polarized sunglasses, filters out light oscillating along all but one direction. The filtered light is referred to as polarized light.

"An enormous challenge was how to solve the design and fabrication of vector polarizers to tailor the light beams and satisfy the requirements of various applications," said Hui-Tian Wang, an author of the study. Wang's group achieved a design that can tailor light intensity, phase and polarization. "The vector polarizer can significantly improve the generation efficiency of vector light beam and may be conducive to achieving a high-performance vector laser."

These advancements can be used to improve a variety of optical systems. In super-resolution microscopy, for instance, manipulating polarization can be used to achieve far-field focusing beyond normal diffraction limitations.

The physicists increased polarizer efficiency and flexibility by using a new liquid-crystal-based design that relies on birefringence, where specific polarizations are filtered based on their refractive indexes. Wang explained that they customized the orientation of liquid crystal molecules by using stringent photo-alignment techniques. They determined the dichroic dye film structure within the thin glass compartment before adding the liquid crystal.

The new vector polarizers also feature manufacturing advantages. "They are flexibly designed and easily fabricated, and have the advantages of the large-size complex structures and the broadband [light waves] operation," Wang said. "However, the vector polarizer we proposed still needs some improvements. For example, we need to improve its alignment quality, i.e., the quality of generated light beams. We also need to improve the spatial resolution for controlling the orientation of liquid crystal molecules."

Wang is particularly excited about this vector polarizer's ability to generate new polarized light states, which he hopes to use in developing novel applications. As an example, entangled vector photon states could be used in developing technology for quantum communications.

This work was supported by the National key R&D Program of China (2017YFA0303800, 2017YFA0303700), AFOSR (FA9550-14-1-0279), the National Natural Science Foundation of China (11534006, 11774183, 11674184), and the Natural Science Foundation of Tianjin (16JC2DJC31300). The researchers acknowledge the support by Collaborative Innovation Center of Extreme Optics.

The article, "Dielectric broadband meta-vector-polarizers based on nematic liquid crystal," is authored by Gui-Geng Liu, Yun-Han Lee, Yuge Huang, Zheyuan Zhu, Guanjun Tan, Meng-Qiang Cai, Ping-Ping Li, Dan Wang, Yongnan Li, Shuo Pang, Chenghou Tu, Shin-Tson Wu and Hui-Tian Wang. The article appeared in APL Photonics Dec. 12, 2017.