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Liquid crystal superstructures or metasurfaces based on Pancharatnam−Berry (PB) phase have made remarkable progress in all‐optical image processing due to the advantages of miniaturization, integration, and multi‐dimensional light field modulation. However, conventional static PB phase devices are usually not tunable and with a single function. Here, based on the tunability of the moiré effect, the wavelength‐independent effect of the PB phase, and the principle of retardation compensation, an ultra‐broadband multifunction moiré‐PB doublet lens is designed, which can realize optical edge imaging with a tunable resolution ranging from 13.2 to 57.2 µm and ultra‐broadband conventional and polarimetric imaging to meet the requirement of multiple functionalities and system integration. In addition, edge feature extraction or edge imaging of low‐contrast biological samples is also realized. Benefiting from the characteristics of miniaturization, switchable multiple imaging functions, and real‐time parallel processing, this method may expand the practicability of modern optical image processing, microscopic imaging, and biomedicine. [ABSTRACT FROM AUTHOR]

Planar liquid crystal (LC) optics has attracted increasing attention with the development of photoalignment technology. However, current LC devices suffer from single optical manipulation, which hinders the implementation of the device's multifunctionality and light integration. Here, combining the orientation degeneracy and rotation multiplexing scheme, several LC elements are proposed for multichannel image displays through a simple single‐cell design. The first design shows the gray‐image multiplexing at the sample surface, which displays two independent binary gray images without crosstalk in two information channels. The second design shows that the amplitude and phase of incident light can be manipulated separately, and a far‐field holographic image is further integrated into the LC device to achieve tri‐channel display. Both the Fraunhofer and Fresnel holograms are considered, and the experiment results agree well with the theoretical designs. Furthermore, the electrical tunability of the LC molecule is demonstrated, and the images can be turned on and off by controlling the voltage. The proposed strategy significantly increases the information capacity without the cost of complex design and fabrication and has promising prospects in multichannel image display, optical anticounterfeiting, encryption, etc. [ABSTRACT FROM AUTHOR]

This study proposed a novel method based on self-interference polarisation pantograph (SiPPer) for fabricating Pancharatnam-Berry (PB) devices. The SiPPer method was composed of a standard Cassegrainian system and a polarization patterned template. Based on the self-interference effect between the ordinary and extraordinary components after the birefringence template, all the polarization information were losslessly transferred to the focal plane on which a photosensitive polarization sample was placed. All PB devices are compatible with this method, including polarization grating, q-plate, q-lens, etc. The SiPPer method indeed lowers the requirement on the exposing source, particularly on the parameters of coherence length and linewidth. To verify and evaluate the properties of the SiPPer method, two typical examples, liquid crystal polarization grating and q-plate, were designed and fabricated according to the standard processing. And the experimental results showed fabulous agreement with the theoretical simulation results. [ABSTRACT FROM AUTHOR]

Planar optical elements have attracted widespread attentions because of their precise light modulation. Liquid crystals (LCs) are well known for their applications in the current displaying field, and show great potential in planar optical elements with the development and innovation of LC micro-operation technology. However, previous researches on LC elements mainly involved only one type of optical manipulation, which inevitably limited the functional diversity. In this work, we propose a multifunctional LC element which integrates the surface display into a binary-phase focusing lens by controlling the complex amplitude of the incident light. The light modulation of the anisotropic LC molecule satisfies a sinusoidal variation, which can be regarded as the combination of a continuous amplitude modulation and a binary phase modulation. The element with millimeter size is then fabricated, and the experimental measurements agree well with our design with a high-definition surface pattern and high-quality optical focusing/imaging performance. Furthermore, as the complex amplitude modulation changes from sine to cosine function after rotating the sample by 45°, a bifocal lens with two different focal lengths is also demonstrated. We expect the proposed multifunctional LC elements can find applications in information multiplexing, image displaying, etc. [ABSTRACT FROM AUTHOR]

As a fundamental material in the current mainstream display technology, liquid crystal (LC) exhibits excellent properties including controllable and reconfigurable LC orientation, high‐efficiency pure‐phase modulation, active tunability, etc., and becomes one of the most attractive candidates for the development of next‐generation flat optical devices. Current LC elements are suffering from the single functionality as only one type of the optical manipulation is involved. Integrating several functions together brings great flexibility and high integration but remains an urgent task. Here, flat LC elements are proposed to simultaneously accomplish near‐field display and far‐field holography. The anisotropic nature of the LC allows a complex amplitude modulation with a sinusoidal variation, promising a continuous amplitude change, and a binary phase modulation. Specifically, several two‐channel LC elements are experimentally demonstrated, which simultaneously generate a grayscale pattern at sample surface and project an independent holographic image in the far field. Furthermore, the position and spatial multiplexing methodologies are introduced to further improve the information capacity. The proposed LC elements with simple anisotropic structure and large fabrication size can empower the multifunctional design and have promising prospects in information multiplexing, image displaying, data storage, etc. [ABSTRACT FROM AUTHOR]

Edge imaging is now an efficient way capable of demonstrating boundary features of an object, which is widely applied in optical imaging, robot vision. In this article, we propose an electrically regulated wedge liquid crystal (LC) cell for edge imaging based upon the combination of the large birefringence of LC and its electro-optic tunable characteristic, and its imaging principle of this element has been theoretically analysed. The experimental results wonderfully manifest that this method can achieve broadband edge imaging and realise real-time mode switch between edge image and original image which can be controlled by a proper voltage. We also demonstrate that the function for achieving electrically controllable resolution is feasible in theory. [ABSTRACT FROM AUTHOR]

In this paper, we extended the methods for fabricating phase-integrated liquid crystal optical elements by interfering of orthogonal circularly polarised beams with different PB phase and generalised those methods as Pancharatnam-Berry (PB) phase interference theory. The generalised theory exhibits two kinds of interference ways. The first way takes place when various PB optical elements (PBOEs) are sequentially illuminated by a linearly polarised light in half-wave condition. The second way happens when the first PBOE is illuminated by a circularly polarised light in quarter-wave condition while the following PBOEs are in half-wave condition. The fabrication of fork polarisation gratings based on this generalised theory is used to confirm the two different interference ways. The generalised theory can better describe the interference of orthogonal circularly polarised beams with different PB phase and can be widely used for fabricating phase-integrated liquid crystal optical elements using existing PB phase device, which may promote the development and extensive applications of the PBOEs. [ABSTRACT FROM AUTHOR]

Liquid crystal (LC) circular polarization gratings (PGs), also known as Pancharatnam–Berry (PB) phase deflectors, are diffractive waveplates with linearly changed optical anisotropy axes. Due to the high diffraction efficiency, polarization selectivity character, and simple fabrication process, photoalignment LC PGs have been widely studied and developed especially in polarization management and beam split. In this review paper, we analyze the physical principles, show the exposure methods and fabrication process, and present relevant promising applications in photonics and imaging optics. [ABSTRACT FROM AUTHOR]