Abstract
Recently, diverse twisting structures have been discovered to be a potential approach to design liquid crystal polarization gratings and lenses (LCPGs and LCPLs) with a high diffraction efficiency, broad bandwidth, wide view, and large diffraction angle. In this review, we divide these twisting structures into two main types, namely, multi-layer twisting structures with phase compensation and twisting structures forming Bragg diffraction. We found that multi-layer twisting structure LCPGs and LCPLs presented a broader bandwidth and a wider view angle by phase compensation. While for transmissive or reflective Bragg LCPGs, a large diffraction angle with high diffraction efficiency could be achieved. Based on the theoretical analysis in the review, potential research directions on novel twisting structures were prospected.
Highlights
Since the geometrical phase [1,2,3] was proposed in 1956, a new degree of freedom was provided to modulate the phase, amplitude, polarization and wave front of light waves.Many kinds of geometrical phase devices have been discovered and researched over the years
LCPLs with we found that the twisting structures, which work in different methods [7,14], are well ture
In order to achieve a large-angle diffraction with high efficiency, another form of grating diffraction, i.e., Bragg diffraction, needs to be considered
Summary
Since the geometrical phase [1,2,3] was proposed in 1956, a new degree of freedom was provided to modulate the phase, amplitude, polarization and wave front of light waves. Yin [13,14] and Li et al [12] studied polarized volume lens (PVLs) These reflective introduced transmissive Bragg PGs based on single and dual-layer twisting structures with can be applied in various fields like wearable displays. From those works reported large diffraction angles. Yishi Weng et al [7,9,10] studied Bragg gratings and reflective we foundvolume that the twisting structures, which work in different polarized gratings (PVGs) with high efficiency and large diffraction methods angle. LCP with multi-layer twisting structures, which provide a better performance in terms of LCPLs with high efficiency, large-angle diffraction generated by twisting stru broadband and wideview angle. Several kinds of reflective and transmissive devices are expounded
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