Pancharatnam-Berry Phase Lens Research Articles

Colorful multi-plane augmented reality display with dynamically tunable reflective Pancharatnam-Berry phase lens.

Reflective cholesteric liquid crystal (CLC) Pancharatnam-Berry phase lens (PBL) devices have attracted significant attention in augmented reality (AR) display due to their wide spectral and angular response bandwidths, high diffraction efficiency, and polarization selectivity. However, currently reported CLC reflective PBLs are either limited by monochrome display or suffers from complicated design for colorful display. Herein, we demonstrate a colorful multi-plane AR display system with dynamically tunable reflective PBL. The reflective PBL is fabricated by polymer-stabilized cholesteric liquid crystal (PSCLC) that provides dynamical and continuous tunability of color and focal length by direct current (DC) voltage. A proof-of-concept colorful multi-plane AR device is demonstrated, where over 90% diffraction efficiency at desired wavelength has been obtained. The proposed simple, compact, and light AR display system capable of color-imaging with multi-depth shows great application potential in the vehicle-mounted head-up display (HUD).

Chromatic aberration measurement of liquid crystal Pancharatnam Berry phase lens by a RGB full-Stokes imaging polarimeter

Pancharatnam Berry (PB) phase optical elements can manipulate local polarization state of light in the cross-sectional plane by addressing an additional PB phase relating to the orientation of the optical axis of the waveplate-like structure. However, chromatic aberration including spectrum-dependent retardation and diffraction efficiency limits their applications in the field of visible broadband imaging and display. In this article, the chromatic aberration of a liquid crystal (LC) PB phase lens was measured by a home-built RGB full-Stokes imaging polarimeter. The chirality conversion efficiency and depolarization at RGB wavelengths can be calculated from the measured Stokes vectors. Our experiments show that even the spectrum-dependent retardation exists, the measured PB phase lens has a uniform and high diffraction efficiency in the visible band. Affected by the local LC molecule, the input polarization of RGB light was rotated in varying degrees, but the focusing or defocusing manipulation to the right- or left-hand circular polarization, originated from the PB phase, results in fixed focal lengths for different colors. Our experiments show that the LC-based PB phase lens is suitable for the visible broadband applications.

Chromatic aberration correction in bi-focal augmented reality display by the multi-layer Pancharatnam-Berry phase lens.

Chromatic aberration is a main obstacle for the commercial application of augmented reality displays. The current digital and optical compensation methods of reducing the chromatic aberration suffer from processing time, power consumption or complex design. Here, a simple strategy of chromatic aberration correction in bi-focal augmented reality near-eye display based on multi-layer Pancharatnam-Berry phase lens has been demonstrated and verified by experimental results. The multi-layer Pancharatnam-Berry phase lens, as a part of optical combiner, is fabricated by three liquid crystal polymer phase lenses with central wavelength in red, green, and blue, respectively. The multi-layer Pancharatnam-Berry phase lens can effectively reduce the chromatic aberration in both convex and concave mode of bi-focal augmented reality system, where the color breakup of virtual images captured in bi-focal augmented reality display is significantly alleviated. Comparing to the value of ΔK = 1.3 m-1 in single green Pancharatnam-Berry phase lens, the multi-layer Pancharatnam-Berry phase lens system significantly reduce the ΔK to 0.45 m-1 with reduction of 65.4%, which finally decreases the longitudinal chromatic aberration and improve the quality of images. The proposed broadband multi-layer Pancharatnam-Berry phase lens can benefit augmented reality displays and find widespread application in the near-eye displays.

Doubling the optical efficiency of VR systems with a directional backlight and a diffractive deflection film.

We demonstrate an approach to double the optical efficiency of virtual reality (VR) systems based on a directional backlight and a diffractive deflection film (DDF). The directional backlight consists of a commercial collimated light-emitting diode (LED) array and a two-layer privacy film, while the DDF is a three-domain Pancharatnam-Berry (PB) phase lens. Such a PB phase lens was fabricated by the zone exposure and spin-coating method. The focal length of each domain is designed according to the imaging optics of the VR system. Our approach works well in both Fresnel and "pancake" VR systems. We also build the corresponding models in LightTools, and the simulation results are in good agreement with experiment. In experiment, we achieved a 2.25x optical efficiency enhancement for both systems, which agrees with the simulation results (2.48x for Fresnel and 2.44x for "pancake" systems) well. Potential application for high efficiency VR displays is foreseeable.

Aberration-corrected full-color holographic augmented reality near-eye display using a Pancharatnam-Berry phase lens.

We present a full-color holographic augmented reality near-eye display using a Pancharatnam-Berry phase lens (PBP lens) and its aberration correction method. Monochromatic and chromatic aberrations of the PBP lens are corrected by utilizing complex wavefront modulation of the holographic display. A hologram calculation method incorporating the phase profile of the PBP lens is proposed to correct the monochromatic aberration. Moreover, the chromatic aberration is corrected by warping the image using the mapping function obtained from ray tracing. The proposed system is demonstrated with the benchtop prototype, and the experimental results show that the proposed system offers 50° field of view full-color holographic images without optical aberrations.

Voltage-controlled liquid crystal Pancharatnam-Berry phase lens with broadband operation and high photo-stability.

Pancharatnam-Berry phase optical elements (PBOEs) have received much attention due to their ability to generate complex structured light or to manipulate the shape of a light beam. This work demonstrates a tunable liquid crystal (LC) Pancharatnam-Berry (LCPB) lens using a simple and cost-effective PB phase hologram optical setup and thermal polymerization to form an irreversible photo-patterning alignment layer. The LCPB lens with high photo-stability supports ultra-broadband operation and provides a diffraction efficiency of ∼90% throughout the visible spectral range, achieved by applying the appropriate voltages. The LCPB lens functions as a convex or a concave lens, depending on the handedness of the circularly polarized incident light, so its image reduction and magnification functions are demonstrated, and its photo-stability is characterized. The fabrication of the proposed LC PBOEs is simpler and more cost-effective than previous methods, and the irreversible photo-patterning alignment layer that is formed by thermal polymerization allows larger operational bandwidths, supporting new applications.

Compact Augmented Reality Combiner Using Pancharatnam-Berry Phase Lens

A compact augmented reality (AR) combiner using Pancharatnam-Berry phase (PBP) lens and holographic optical element (HOE) is proposed. PBP lens is activated as a convex lens or a concave lens according to the polarization state of the input light wave. By using this characteristic, a thin AR eyepiece with a large numerical aperture (NA) is constructed. The AR eyepiece operates as a convex lens for the input light with a right-handed circular polarization state and operates as a transparent plate for the left-handed circularly polarized light. In order to adopt this AR eyepiece to the AR combiner, a chromatic aberration should be compensated. To resolve the chromatic aberration, HOE which diffracts the light rays with different profiles according to the input wavelength is designed. By combining this HOE with the AR eyepiece and a light guide, a compact AR combiner providing a wide field of view (FOV) is designed. A prototype of the proposed AR combiner is presented along with experimental results and analysis.

Practical Chromatic Aberration Correction in Virtual Reality Displays Enabled by Cost‐Effective Ultra‐Broadband Liquid Crystal Polymer Lenses

AbstractChromatic aberration (CA) is a critical issue in immersive virtual reality displays. The current digital compensation method can reduce the CA by pre‐processing the image contents but at the cost of extra memory space, processing time, and power consumption. Moreover, it is not possible to digitally compensate the CA within each color channel. Here, a practical optical approach is presented to correct the CAs, including the sub‐channel ones, in the virtual reality system, whose functionality is verified by both ray‐tracing analysis and experimental results. In this device, a compact ultra‐broadband Pancharatnam‐Berry phase lens (PBL) with complex axial molecular structure is fabricated and then hybridized with a refractive Fresnel lens. Due to their opposite chromatic dispersion, the system's CA is significantly reduced. To eliminate ghost image from the zero‐order leakage of PBL, a broadband circular polarizer is implemented to block the stray light. As a result, clear image within the entire 100° field‐of‐view is achieved. The proposed large‐size cost‐efficient broadband wide‐view flat optics can practically benefit not only virtual reality displays but also general imaging systems for practical applications and scientific research.

Manipulating longitudinal photonic spin Hall effect based on dynamic and Pancharatnam-Berry phase

Photonic spin Hall effect is generally described as a spin-dependent splitting. Previous studies have focused on the transverse spin-dependent splitting of light field. In this work, a method of manipulating the longitudinal photonic spin Hall effect which is based on dynamic and Pancharatnam-Berry phase is proposed. The theoretical analysis demonstrates that the lens group consisting of a Pancharatnam-Berry phase lens and a dynamic lens has two spin-dependent foci. Firstly, because Pancharatnam-Berry phase is spin-dependent, the left- and right-handed circularly polarized component can respectively acquire a Pancharatnam-Berry phase with opposite sign when a linearly polarized light beam passes through the Pancharatnam-Berry phase lens with phase retardation <inline-formula><tex-math id="M90">\begin{document}${\text{π}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20182004_M90.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20182004_M90.png"/></alternatives></inline-formula>. It leads one circularly polarized component to be focused and the other diverged. This is essentially the spin-dependent splitting of light field in momentum space, which is caused by Pancharatnam-Berry phase. And then, an ordinary lens is inserted behind the Pancharatnam-Berry phase lens to introduce a dynamic phase modulation. Due to dynamic phase being spin-independent, the constructed lens group can focus the photons with different spin states at different focal points longitudinally under the appropriate conditions. In other words, the lens group has two spin-dependent focal points. The two focal points split the photons with different spin states in the longitudinal direction. The longitudinal spin-dependent splitting is dependent on the focal lengths of the two lens and the distance between the two lenses. By changing the three parameters, arbitrary longitudinal spin-dependent splitting can be obtained. Lastly, an experimental system is set up to verify the theoretical results. The relationship between the spin-dependent splitting and the distance between the two lenses is measured. By introducing a Glan laser polarizer and a quarter wave-plate, the circularly polarized chirality of the light field at the focal point is also measured. These experimental results are all in good agreement with the theoretical analyses. These results are helpful in understanding the physical origin of photonic spin Hall effect and developing novel photonic devices based on photonic spin Hall effect.

Polarization-independent Pancharatnam-Berry phase lens system.

The conventional liquid crystal-based Pancharatnam-Berry (PB) phase lens exhibits distinct polarization selectivity, manifesting opposite optical power to circularly polarized light with opposite handedness. Here, a polarization-independent liquid crystal PB lens system is theoretically predicted and experimentally verified. Such a lens system consists of at least four PB lenses, with specific distances in between them. This enables the PB lens to be applied in polarization-independent optical systems.

Liquid crystal Pancharatnam-Berry phase lens with spatially separated focuses

ABSTRACTIn this paper, we proposed and fabricated a liquid crystal (LC) lens with spatially separated focuses via liquid crystal photoalignment technology. The novel lens is an integration of the polarisation grating and conventional LC lens. The two focuses of that new lens, one of which is real while the other is virtual, can be spatially separated. When combined with normal convex lens and illuminated by a linearly polarised beam, the two emergent light beams become all convergent and the two focuses are separated in three-dimension space. Moreover, the focal lengths of the lens system can be artificially controlled by adjusting the distance between our new lens and the conventional lens. Our results achieve the potential of LC lens’ application in imaging devices such as multifocal cameras, bifocal eyeglasses and so on.

Compact photonic spin filters

In this letter, we propose and experimentally demonstrate a compact photonic spin filter formed by integrating a Pancharatnam-Berry phase lens (focal length of ±f) into a conventional plano-concave lens (focal length of −f). By choosing the input port of the filter, photons with a desired spin state, such as the right-handed component or the left-handed one, propagate alone its original propagation direction, while the unwanted spin component is quickly diverged after passing through the filter. One application of the filter, sorting the spin-dependent components of vector vortex beams on higher-order Poincaré sphere, is also demonstrated. Our scheme provides a simple method to manipulate light, and thereby enables potential applications for photonic devices.

44-3: Nanoscopic Patterned Photo-alignment for Electrically Switchable Liquid Crystal Pancharatnam-Berry Phase Diffractive Lens

In this paper, we disclosed the realization of a nano-structured alignment patterning for thin film Pancharatnam-Berry phase (PBP) diffractive lens by the use of polarized light converter technology. High optical quality switchable liquid crystal PBP lens with F number of 20, a diffraction efficiency of 93 % at 532 nm wavelength, with a low operating voltage of 5 V and a switching response time of 8 ms has been demonstrated.

Optical integration of Pancharatnam-Berry phase lens and dynamical phase lens

In the optical system, most elements such as lens, prism, and optical fiber are made of silica glass. Therefore, integrating Pancharatnam-Berry phase elements into silica glass has potential applications in the optical system. In this paper, we take a lens, for example, which integrates a Pancharatnam-Berry phase lens into a conventional plano-convex lens. The spin states and positions of focal points can be modulated by controlling the polarization states of the incident beam. The proposed lens has a high transmission efficiency, and thereby acts as a simple and powerful tool to manipulate spin photons. Furthermore, the method can be conveniently extended to the optical fiber and laser cavity, and may provide a route to the design of the spin-photonic devices.

Photonic spin filter with dielectric metasurfaces.

We propose a photonic spin filter whose structure is similar to that of conventional spatial filter, but the two plano-convex lenses are replaced by Pancharatnam-Berry phase ones. The dielectric metasurface with high transmission and conversion efficiency is designed to work as Pancharatnam-Berry phase lens. The photonic spin filter can sort desired spin photons from the input beam with mixed spin states, and thereby facilitate possible applications in spin-based photonics.

Paper No S1.4: “Continuous” Nanoscale Patterned Photoalignment for Thin Film Pancharatnam‐Berry Phase Diffractive Lens

AbstractIn this paper, we disclosed the realization of a “continuous” nano‐structured alignment patterning for thin film Pancharatnam‐Berry phase (PBP) diffractive lens by the use of spatially linear polarized light converter technology. High optical quality thin liquid crystal polymer (LCP) film PBP lens with F number of 45.4 and a diffraction efficiency of 95.5%, operating in blue visible region has been demonstrated. The concave and convex polarization dependent property of the lens can be clearly observed by human eye, which is attractive in many display applications, for example, bifocal lens for eye glasses; camera zoom system; and polarization imaging.