Pancharatnam-Berry Phase Research Articles

Switchable Pancharatnam-Berry Phases in Heterogeneously Integrated THz Metasurfaces.

The Pancharatnam-Berry (PB) phase has revolutionized the design of metasurfaces, offering a straightforward and robust method for controlling wavefronts of electromagnetic waves. However, traditional metasurfaces have fixed PB phases determined by the orientation of their individual elements. In this study, an innovative structural design and integration scheme is proposed that utilizes vanadium dioxide, a phase-change material, to achieve thermally controlled dynamic PB phase control within the metasurface. By leveraging the material's properties, this can dynamically alter the optical orientation of individual elements of the metasurface and achieve temperature-dependent local phase modulation based on the geometric phase principle. This approach, combined with advanced fabrication processing technology, paves the way for next-generation dynamic devices with customizable functions.

Liquid-crystal-based diffractive optical elements with high Pancharatnam-Berry phase accuracy for holographic displays fabricated using an optimized liquid crystal on silicon device

A rapid and accurate photoalignment technique was proposed for the fabrication of liquid crystal Pancharatnam-Berry phase diffractive optical elements (LC PB-DOEs). The in-plane orientation of LCs was precisely manipulated through the polarized illumination of an optimized liquid crystal on silicon (LCOS) device. LCOS and thereafter spatial light modulator (SLM) can generate polarization patterns at pixel level at will. The quality of such alignment was improved significantly by minimizing the phase flicker of the phase-only LCOS SLM. This was confirmed by the increase of the measured quality of the holographic images reconstructed using our DOE in terms of structural similarity (SSIM) and peak signal-to-noise ratio (PSNR) at 30% and 5%, respectively. Furthermore, a bi-focal LC PB-lens was fabricated and used as a high quality Fourier lens in holographic display to validate the usefulness of such LC PB-DOEs. This work illustrated a ubiquitous approach of fabricating different types of lightweight and thin form factor DOEs of random phase patterns at pixel level with low cost and high throughput.

Observation of High-Order Quantum Pancharatnam-Berry Phase with Structured Photons

When a quantum system evolves so that it returns to its initial state, it will acquire a geometric phase acting as a memory of the transformation of a physical system, which has been experimentally measured in a variety of physical systems. In optics, the most prominent example is the Pancharatnam-Berry (PB) phase. Recent technological advances in phase and polarization structure have led to the discovery of high-order PB phases with structured light fields. The study on the high-order PB phase is limited in the context of elementary quantum states of light, especially in the case of photon number states. Here, we experimentally investigate the differences of high-order PB phases between single-photon and N00N states. Our results show that the PB phase, like the dynamic phase, can also be doubled under two-photon states, which can greatly improve the phase sensitivity for greater N in N00N states and high-order structured photons. This may show some implications for quantum precision measurement and quantum state engineering based on geometric phase.

Reconfigurable Generation and Spin Manipulation of Structured Beams Based on Cascaded Liquid Crystal Pancharatnam–Berry Phase Elements

Reconfigurable Generation and Spin Manipulation of Structured Beams Based on Cascaded Liquid Crystal Pancharatnam–Berry Phase Elements

Dynamic light manipulation by geometric phase metasurface incorporated to Tamm plasmon polariton structure

The paper demonstrates the ability to manipulate diffraction order intensity by combining a geometric phase (Pancharatnam–Berry phase) metasurface and a Tamm plasmon polariton based structure. This combination enables the simultaneous occurrence of resonant and non-resonant variations in the phase of the reflected light. It is shown that, when a meta-atom composed of antimony trisulfide undergoes a transition from an amorphous to a crystalline state, accompanied by a change in the polarization of the incident light, there is a redistribution of intensity between 0 and ±1 diffraction orders.

Global Selection Rules and Giant Enhanced Harmonic Generations in LiNbO3 Nonlinear Meta‐Optics

AbstractNonlinear optical metasurfaces provide nanoscale‐level control of harmonic waves, making them highly promising platforms for both fundamental research and applications in nonlinear optics. However, the traditional selection rules theory, which has long served as a guiding principle for nonlinear meta‐optics, is local and neglects the significance of meta‐atomic lattice symmetry. In addition, achieving high‐efficiency harmonic generation along with nonlinear optical Pancharatnam‐Berry (PB) phase control remains challenging. To this end, a novel global selection rule jointly determined by the symmetries of both meta‐atom and lattice is proposed. Nonlinear metasurfaces designed based on this theory enable frequency conversions forbidden by previous local selection rules. A more comprehensive relationship between the nonlinear PB phase and the meta‐atomic rotation angle is revealed. Moreover, an efficient nonlinear PB metasurface platform for second harmonic generations is first demonstrated using LiNbO3 thin films with aligned crystal orientations in a hybrid design. The normalized conversion efficiency reaches approximately two orders of magnitude higher than that of existing nonlinear PB metasurfaces working in the near‐infrared band. These findings not only shed light on the underlying mechanisms of nonlinear light‐matter interactions, but also open up exciting possibilities in terahertz, entangled photon pairs, and high harmonic generations.

Breaking of reciprocity and the Pancharatnam-Berry phase for light scattered by a disordered cold-atom cloud

Breaking of reciprocity and the Pancharatnam-Berry phase for light scattered by a disordered cold-atom cloud

Spatial momentum separation for optical vortex via phase-assembled metasurfaces

Expanding the spatial degrees of freedom is regarded to be the most innovative and effective solution for optical vortex encoding/decoding technology. A phase-assembled metasurface is proposed here to separate the momentum of the optical vortex into different spatial locations, and the incident high-order optical vortex is encoded in 18 channels. By combining both the propagation phase and the Pancharatnam-Berry (PB) phase, the fundamental Gaussian mode (solid spot) positions and other higher-order orbital angular momentum modes (hollow mode spots) positions at different channels are used to achieve the encryption of all-optical information. The scheme of grouping the mode spots on different channels into solid and hollow points greatly reduces the difficulty of encoding/decoding a high-order optical vortex. In this way, the combination of 2 incident high-order optical vortexes can represent 256 hexadecimal numbers from 00 to FF. We envision this work will open avenues for information encryption, multidimensional data storage, wavefront manipulation, and advanced orbital angular momentum detection technologies.

A Low-Profile and Ultra-Wideband Pancharatnam-Berry Coding Metasurface for High-Efficiency and Wide-Angle Circular Polarization Anomalous Reflection.

The manipulation of electromagnetic waves using metasurfaces is important in areas such as stealth and communication. In this paper, we reported on the use of an element-based polarizer for the first step, which enables the incident electromagnetic waves to integrate into the cross-polarized waves with a relative bandwidth of 88% within 15-37.1 GHz. Then, an eight-element coding metasurface based on the Pancharatnam-Berry phase is presented for circular polarization anomalous reflection. The simulated values show that our work can achieve a high-efficiency (94%) and wide-angle (70°) anomalous reflection under normal incidence. The simulated values present good agreement with the experimental values. Our work reveals the ability to manipulate the waves and electromagnetic stealth.

Influence of thermal bath on Pancharatnam-Berry phase in an accelerated frame

A uniformly accelerated atom captures Pancharatnam-Berry phase in its quantum state and the phase factor depends on the vacuum fluctuation of the background quantum fields. We observe that the thermal nature of the fields further affects the induced phase. Interestingly the induced phase captures the exchange symmetry between the Unruh and real thermal baths. This observation further supports the claim that the Unruh thermal bath mimics a real thermal bath. Moreover for certain values of system parameters and at high temperature, the phase is enhanced compared to zero temperature situation. However the required temperature to observe the phase experimentally is so high that the detection of Unruh effect through this is not possible within the current technology.

A tunable chiral metasurface useable in terahertz imaging and wavefront shaping

We proposed a tunable chiral metasurface comprising a reflective bottom layer of gold, a dielectric layer of polyimide, and a structural top layer of gold-graphene. Its main properties were studied via numerical simulations conducted using CST Studio Suite. The results indicate that, based on the chiral metasurface, we achieved dual-band circular dichroism of −0.5 and 0.77 at 0.9 THz and 1.06 THz, respectively, and complementary near-field imaging applications were realized by tuning the Fermi level (E f ) of graphene. Subsequently, exploiting the exceptional selective characteristics of circularly polarized waves using a chiral metasurface, eight chiral phase-gradient metasurfaces were constructed by rotating the chiral structure. Moreover, based on the Pancharatnam-Berry phase principle, tunable wavefront shaping applications were further realized, including anomalous reflection, vortex beams, and focusing. In anomalous reflection, the reflection angles for left-circularly polarized (LCP) and right-circularly polarized (RCP) incidences are opposite when adjusting the E f of graphene. For example, when the graphene E f is 0 eV and the LCP wave is incident at 0°, the reflection angle is −18°. Conversely, when the graphene E f is 1 eV and the RCP wave is incident at 0°, the reflection angle is 18°. In the application of vortex beams, by adjusting the E f of graphene, we achieved vortex beams with opposite topological charges under different circularly polarized incidences. In the focusing application, the incident LCP and RCP can achieve focusing and defocusing, respectively. And the graphene E f can dynamically control the focusing efficiency at the incident LCP, increasing it from 13.63% to 44.84%.

Simple and hybrid metalens with high polarization conversion efficiency for near-infrared spectrum

Thanks to their ability to control light, research on metalenses is developing rapidly. However, it is still quite difficult to design broadband metalenses with high polarization conversion efficiency. In this study, an alternative plasmonic material, aluminum-doped zinc oxide, is presented for metalens operating in near-infrared regime. We propose simple and hybrid metalenses with high polarization conversion efficiency and high transmission values that can focus efficiently in a wide near-infrared bandwidth (700–1000 nm). We design metalens consisting of subwavelength aluminum-doped zinc oxide nanoblocks based the Pancharatnam-Berry phase method and utilizing the finite-difference time-domain method. The polarization conversion efficiency (minimum 87 %) and transmission values (minimum 85 %) calculated for the metalens unit cell are higher than those previously obtained over the entire 300 nm bandwidth. In addition, we propose hybrid metalens to focus the incident beam in right and left handed circular polarized states in the studied frequency range. The presented aluminum-doped zinc oxide metalens with high polarization conversion efficiency and transmission values can find a place in the applications of near-infrared nanophotonic systems.

Design of Compact Dielectric Metalens Visor for Augmented Reality Using Spin-Dependent Supercells

Augmented reality overlays computer-generated virtual information onto real-world scenes, enhancing user interaction and perception. However, traditional augmented reality optical systems are usually large, bulky, and have limited optical performance. In this paper, we propose a novel compact monochrome reflective dielectric metalens visor with see-through properties, engineered using a periodic structure of spin-dependent supercells. The supercell, which is composed of staggered twin nanofins, provides spin-dependent destructive or constructive interference with different circularly polarized incidences. The design combines the principles of interference with the Pancharatnam–Berry phase to enhance reflection at a working wavelength of 650 nm while maintaining good transmission. Right circularly polarized light incident from the substrate side causes destructive interference, enabling the supercell to work in reflection mode, while left circularly polarized light causes constructive interference, enabling the supercell to work in transmission mode. Furthermore, the supercell-constructed metalens can achieve near-diffraction-limited reflective focusing and a broad diagonal field of view of approximately 96°. In addition, compared to transmissive metalens visors, the reflective design eliminates the need for a beam splitter, significantly reducing the size and weight of the system. Our work could facilitate the development of compact and lightweight imaging systems and provide valuable insights for augmented reality near-eye display applications.

A Broadband Multi‐Channel Metasurface for Decoupling of Phase and Polarization

AbstractDecoupling of phase and polarization is significant for multidimensional light manipulation. However, this requires traditional cascaded and parallel optical elements, resulting in a bulky and complex system. Metasurfaces can potentially replace complex optical modules as novel ultrathin planar optical elements. Herein, an ultrathin single‐layer metasurface is proposed to decouple the phase and polarization based on the Pancharatnam–Berry phase. The rotation angles of the two nanofins are employed to manipulate the phase and polarization independently, significantly simplifying the design process. Diffraction‐limited focusing with a degree of linear polarization higher than 95% is achieved for wavelengths in the 405–633 nm range. Furthermore, a metasurface can arbitrarily manipulate the relative intensity between different channels. The intensity ratio is adjusted from 0.12 to 6.62. These results will pave the way for miniaturized, integrated, and multi‐channel optical elements.

Perfect vortex beams generation based on reflective geometric phase metasurfaces

Perfect vortex beam (PVB) is a propagating light field with radial intensity distribution independent of topological charge and carrying orbital angular momentum (OAM). PVBs can be generated through the Fourier transformation of a Bessel-Gaussian (BG) beam, which traditionally requires a precisely aligned optical setup consisting of a spiral phase plate, a conical lens, and a Fourier lens. However, such traditional schemes are usually bulky and unstable. Here, we have utilized a method that differs from conventional approaches, employing metasurfaces designed as planar Pancharatnam-Berry (PB) phase elements to substitute for all the required components. Unlike traditional methods based on reflective or refractive elements, metasurface elements can significantly reduce the system's footprint. Because the use of metallic metasurfaces allows for a more flattened design plane, in this paper, we have demonstrated the generation of PVB within the 8 GHz microwave frequency band based on a single-layer metallic metasurface. The metasurface is composed of a square ring metal structure, which can serve as a half wave plate to provide the required geometric phase distribution for incident circularly polarized light to generate PVB. By rigorously optimizing the parameters of the square-ring structures, we have generated vortex beams carrying OAM with different topological charges. These vortex beams exhibit a constant radial intensity distribution, which validates their "perfect" characteristics. In addition, we also extracted the mode purity of different vortex beams, so that the mode states of different vortex beams can be distinguished. These results provide broader value for the application of perfect vortex beams in communication.

Twisted Stacking Metasurface for Complete Amplitude and Phase Control of Circularly Polarized Terahertz Waves

AbstractTerahertz (THz) metasurfaces have emerged as a powerful tool for manipulating THz wavefronts, typically achieved by adjusting various geometric parameters. In this study, an approach is introduced by incorporating interlayer coupling into twisted stacking metasurface design to completely control the amplitude and phase of circularly polarized THz waves. By leveraging the interlayer coupling effect and the Pancharatnam–Berry phase, the study achieves efficient control over transmission phase and amplitude by simply adjusting the relative twist angle between paired C‐shaped split‐ring resonators. To validate the concept, a holographic metasurface is fabricated and characterized, providing experimental evidence of its THz wavefront manipulation capabilities. This design strategy presents a versatile and tunable solution for THz wave control, promising applications in a wide range of functional devices.

Broadband Spin-Selective Wavefront Manipulations with Generalized Pancharatnam–Berry Phase Metasurface

Broadband Spin-Selective Wavefront Manipulations with Generalized Pancharatnam–Berry Phase Metasurface

Broadband high-efficiency meta-holography from all-dielectric quasi-continuous metasurfaces

The compactness and particular optical design make metasurface a competitive candidate for holographic display and storage. Recently, the selection and optimization for the used metasurface structures and types have become research spots. Now the most researched and demonstrated meta-holograms are often based on discrete structures, which can achieve high efficiency but comparatively narrow working bandwidths or a wide wavelength range but low power efficiency. Therefore, contemporary meta-holograms struggle for realizing simultaneous broadband and high efficiency. In this paper, all-dielectric quasi-continuous metasurfaces composed of nanostrips are introduced to expand the operating bandwidth for high efficiency meta-holography. Benefiting from the associated Pancharatnam–Berry phase, the nanostrips with spatially orientation angles continuous changes can realize arbitrary phase modulation. For the first time, the average power efficiency of a meta-hologram is experimentally measured to be 56.63% over a broad wavelength band ranging from 500 to 1000 nm. In addition, based on this kind of all-dielectric quasi-continuous nanostrips, we also design and experimentally achieve multicolor three-dimensional (3D) holographic images. Actually, such all-dielectric quasi-continuous methodology proposed here can be used to design other functional meta-devices, including optical metalens, nanoprinting, and information encryption.

Quarter-wave Pancharatnam-Berry phase gradient liquid crystal-enabled dual-polarization optical edge detection.

Here, we present a novel, to the best of our knowledge, optical edge detection scheme that can be operated in both linear and circular polarization modes, leveraging an optical spatial differentiator constructed by quarter-wave Pancharatnam-Berry (P-B) phase gradient element. After explaining the theoretical mechanism, we utilize a quarter-wave P-B phase liquid crystal polarization grating to validate the dual-polarization optical edge detection capability. We demonstrate that the orientation of linear polarization and the spin of circular polarization dictate the transition between edge and bright-field images. Besides, the linear and circular polarization modes exhibit broadband and monochromatic responsive properties, respectively. This mechanism, dependent on wavelength and polarization, holds promise for applications in color image processing, chiral sensing imaging, and polarization-entangled quantum imaging.

Switchable Terahertz Metasurfaces for Spin-Selective Absorption and Anomalous Reflection Based on Vanadium Dioxide.

Conventional chiral metasurfaces are constrained by predetermined functionalities and have limited versatility. To address these constraints, we propose a novel chirality-switchable terahertz (THz) metasurface with integrated heating control circuits tailored for spin-selective anomalous reflection, leveraging the phase-change material vanadium dioxide (VO2). The reversible and abrupt insulator-to-metal phase transition feature of VO2 is exploited to facilitate a chiral meta-atom with spin-selectivity capabilities. By employing the Pancharatnam-Berry phase principle, complete 2π reflection phase coverage is achieved by adjusting the orientation of the chiral structure. At the resonant frequency of 0.137 THz, the designed metasurface achieves selective absorption of a circularly polarized wave corresponding to the state of the VO2 patches. Concurrently, it reflects the circularly polarized wave of the opposite chirality anomalously at an angle of 28.4° while maintaining its handedness. This chirality-switchable THz metasurface exhibits promising potential across various applications, including wireless communication data capacity enlargement, polarization modulation, and chirality detection.