Abstract
In the past two decades, polarization gratings (PGs) have attracted intensive attention due to the high-efficient diffraction and polarization selectivity properties. On one hand, the one-dimensional (1D) PGs have been investigated widely and adapted to various applications. On the other hand, optical signal manipulation stimulates the development of multibeam optical devices. Therefore, the development of two-dimensional (2D) PGs is in demand. This review summarizes the research progress of 2D PGs. Different designs and fabrication methods are summarized, including assembling two 1D polarization patterns, a 2D holographic lithography by polarization interference and a micro-pixelated electric field stimulated 2D liquid crystal (LC) structure. Both experiments and analyses are included. The design strategy, diffraction property, merits and demerits are discussed and summarized for the different methods.
Highlights
Light polarization is a key parameter of light
Different from traditional diffraction gratings using a binary liquid crystal (LC) structure, the polarization gratings (PGs) requires a fine patterning of LC directors, whose fabrication costs and time requirements are highly based on methods such as micro-rubbing and imprinting [8,9]
The 2D PG provides great potentiality for 2D nonmechanical beam steering with a single optical element. The compactness makes it competitive for applications in augmented reality (AR) and virtual reality (VR) systems, where multiple diffraction angles are necessary for eye tracking and EyeBOX enlarging [58,59]
Summary
Light polarization is a key parameter of light. Various applications, such as biomimetics, imaging system and quantum communication, have been developed rapidly based on this feature [1,2,3,4,5]. The square web of disclinations pattern (b) and diffraction efficiency (c) with the applied ac voltage. With a proper applied electric field, the diffraction gave a similar property as in References [30,31], since the LC directors were aligned vertically in the bulk, and the 2D grating behaved as two cross-assembled 1D PGs. It is noted that the above discussion was based on the premise of strong surface anchoring. The diffraction pattern changed with the different grating behaved as two cross-assembled 1D PGs. It is noted that the above discussion was based on the premise of strong surface anchoring.
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