Metasurface Holography Research Articles

Low‐Profile Electromagnetic Holography by Using Coding Fabry–Perot Type Metasurface with In‐Plane Feeding

AbstractMetasurface holography has been well studied due to its features that are superior to the traditional holographic technologies. However, high profiles of the reflection‐ and transmission‐type configurations in the metasurface holography restrict its applications. On the other hand, digital coding metasurfaces have received great attention recently because they build a link between the information theory and surface electromagnetic fields, which also bring new viewpoint and convenience for digital computational holography. Here, a real low‐profile holographic method is proposed using a leaky‐type 2‐bit coding Fabry–Perot metasurface with in‐plane feeding in the microwave frequency. For constructing the metasurface hologram, the weighted Gerchberg–Saxton algorithm is presented to modulate the energy proportion of focal points by adjusting the phase distribution. As proof of concept, some typical metasurface holograms are demonstrated in microwave experiments at the height of 35 mm (≈3 wavelengths), which show good agreement with theoretical analyses and full‐wave simulations. The design method can be easily extended to the millimeter wave and terahertz bands.

Ultra-broadband metasurface holography via quasi-continuous nano-slits

Metasurface holography has attracted growing interest in the optical fields, owing to its potentiality in various applications such as the high-capacity data storage and three-dimensional imaging with large viewing angle. However, most reported metasurface holograms consist of discrete meta-atoms, which limit the broadband performances of the holographic devices. In this paper, a metasurface hologram, composed of quasi-continuous nano-slits, is demonstrated to realize high-efficiency and broadband holographic images with both simulation and experiment. The quasi-continuous metasurface hologram proposed here can effectively expand the working bandwidth, especially when the characteristic dimension of the meta-hologram is at deep-subwavelength scale. We anticipate that the proposed approach could greatly promote the applications of metasurface, such as flat lens, vortex beam generator and optical storage.

Trichromatic and Tripolarization-Channel Holography with Noninterleaved Dielectric Metasurface

Metasurfaces hold great potentials for advanced holographic display with extraordinary information capacity and pixel sizes in an ultrathin flat profile. A dual-polarization channel to encode two independent phase profiles or spatially multiplexed meta-holography by interleaved metasurfaces are captivated popular solutions to projecting multiplexed and vectorial images. However, the intrinsic limit of orthogonal polarization-channels, their crosstalk due to coupling between meta-atoms, and interleaving-induced degradation of efficiency and reconstructed image quality set great barriers for sophisticated meta-holography from being widely adopted. Here we report a noninterleaved TiO2 metasurface holography, and three distinct phase profiles are encoded into three orthogonal polarization bases with almost zero crosstalk. The corresponding three independently constructed intensity profiles are therefore assigned to trichromatic (RGB) beams, resulting in high-quality and high-efficiency vectorial meta-holography in the whole visible regime. Our strategy presents an unconventionally advanced holographic scheme by synergizing trichromatic colors and tripolarization channels, simply realized with a minimalist noninterleaved metasurface. Our work unlocks the metasurface's potentials on massive information storage, polarization optics, polarimetric imaging, holographic data encryption, etc.

Quantitatively Correlated Amplitude Holography Based on Photon Sieves

AbstractAs an excellent holographic information carrier, metasurface holograms possess the advantages of subwavelength footprint, leading to large field of view and high resolution. Meanwhile, intelligent algorithms should be developed to fully exploit the flexible modulation properties provided by metasurfaces. Here, two amplitude holograms with quantitatively correlation are realized using the photon sieve as the amplitude modulation device. A new iterative algorithm is developed to obtain the amplitude profiles of the two holograms with correlation, which can make the two profiles mutually connect by simply adding/erasing dynamic pixels. Two photon sieves composed of nanoholes arrays are fabricated to demonstrate the feasibility of the scheme. This amplitude holography method can operate throughout the entire visible and near‐infrared wavelength regions with polarization independence, and it is expected to achieve switchable metasurface holography with the development of materials science. Such scheme promises to be applied in compact data storage, dual pattern recognition, optical encryption, and so on.

When metasurface meets hologram: principle and advances

Holography has numerous applications because of its capability of arbitrary wavefront modulation. Computer-generated holograms (CGHs) take it a big step forward. Conventional holography engineers the wavefront via phase accumulation, suffering from large size, low resolution, and small viewing angle. Metasurfaces, ultrathin two-dimensional metamaterials with subwavelength features, can manipulate the amplitude, phase, and polarization of the light, solving the above issues. In this review, advances of holography, CGH algorithms, and the principles of various metasurfaces are presented. Metasurface holography, realized by encoding the hologram in the metasurface, is investigated. Information multiplexing methods of metasurface holograms, including wavelength-multiplexed, polarization-multiplexed, complex amplitude modulated, nonlinear, and dynamic metasurfaces, are presented. The challenges and outlook of metasurface holograms are discussed.

Recent advances in metasurface hologram technologies (Invited paper)

Since Leith and Upatnieks demonstrated the first optical hologram in 1964, hologram technology has attracted a great deal of interest in a wide range of optical fields owing to its potential use in future optical applications such as holographic imaging and optical data storage. Although there have been considerable efforts to develop holographic technologies using conventional optics, critical issues still hinder future development. Recently, metasurfaces composed of artificially fabricated subwavelength structures have been considered as novel holographic devices that show an unprecedented ability to control electromagnetic waves. In this review, we outline the recent progress in metasurface holography. A general introduction to several types of metasurface holography categorized based on their physics and application is provided. Then, our personal perspective on the future of this field is discussed.

Metasurface holography: from fundamentals to applications

AbstractHolography has emerged as a vital approach to fully engineer the wavefronts of light since its invention dating back to the last century. However, the typically large pixel size, small field of view and limited space-bandwidth impose limitations in the on-demand high-performance applications, especially for three-dimensional displays and large-capacity data storage. Meanwhile, metasurfaces have shown great potential in controlling the propagation of light through the well-tailored scattering behavior of the constituent ultrathin planar elements with a high spatial resolution, making them suitable for holographic beam-shaping elements. Here, we review recent developments in the field of metasurface holography, from the classification of metasurfaces to the design strategies for both free-space and surface waves. By employing the concepts of holographic multiplexing, multiple information channels, such as wavelength, polarization state, spatial position and nonlinear frequency conversion, can be employed using metasurfaces. Meanwhile, the switchable metasurface holography by the integration of functional materials stimulates a gradual transition from passive to active elements. Importantly, the holography principle has become a universal and simple approach to solving inverse engineering problems for electromagnetic waves, thus allowing various related techniques to be achieved.

Multi-focus lens based on metasurface holography

A broadband multi-focus lens based on metasurface holography in the far-infrared region is designed. By designing 8 C-shaped resonant rings, when linearly polarized light waves are incident normally to this set of resonators, cross-polarized component of transmitted light will form the phase shift from 0 to 2π, meanwhile the amplitude transmittance remains constant. Full-wave simulation was utilized to verify anomalous refraction properties when linearly polarized light waves irradiated this set of resonators vertically. The phase distribution of multi-focus lens was obtained by adopting the computer-generated hologram (CGH) method. According to arranged resonant rings based on the calculated phase distribution, a squared multi-focus lens based on metasurface was obtained. Simulation for the designed lens was conducted. Results show a good multi-focusing performance at the central frequency 28 THz in the focal length of 108 μm.

Phase and magnitude constrained metasurface holography at W-band frequencies.

Holographic optics are an essential tool for the control of light, generating highly complex and tailored light field distributions that can represent physical objects or abstract information. Conceptually, a hologram is a region of space in which an arbitrary phase shift and amplitude variation are added to an incident reference wave at every spatial location, such that the reference wave will produce a desired field distribution as it scatters from the medium. Practical holograms are composed of materials, however, which have limited properties that constrain the possible field distributions. Here, we show it is possible to produce a hologram with continuous phase distribution and a non-uniform amplitude variation at every point by leveraging resonant metamaterial elements and constraining the hologram's pixels to match the elements' resonant behavior. We demonstrate the viability of the resonant metamaterial approach with a single layer, co-polarized holographic metasurface that produces an image at millimeter wavelengths (92.5 GHz) despite the elements' limited phase range and coupled amplitude dependency.

Spin and wavelength multiplexed nonlinear metasurface holography.

Metasurfaces, as the ultrathin version of metamaterials, have caught growing attention due to their superior capability in controlling the phase, amplitude and polarization states of light. Among various types of metasurfaces, geometric metasurface that encodes a geometric or Pancharatnam–Berry phase into the orientation angle of the constituent meta-atoms has shown great potential in controlling light in both linear and nonlinear optical regimes. The robust and dispersionless nature of the geometric phase simplifies the wave manipulation tremendously. Benefitting from the continuous phase control, metasurface holography has exhibited advantages over conventional depth controlled holography with discretized phase levels. Here we report on spin and wavelength multiplexed nonlinear metasurface holography, which allows construction of multiple target holographic images carried independently by the fundamental and harmonic generation waves of different spins. The nonlinear holograms provide independent, nondispersive and crosstalk-free post-selective channels for holographic multiplexing and multidimensional optical data storages, anti-counterfeiting, and optical encryption.

Highly anisotropic metasurface: a polarized beam splitter and hologram.

Two-dimensional metasurface structures have recently been proposed to reduce the challenges of fabrication of traditional plasmonic metamaterials. However, complex designs and sophisticated fabrication procedures are still required. Here, we present a unique one-dimensional (1-D) metasurface based on bilayered metallic nanowire gratings, which behaves as an ideal polarized beam splitter, producing strong negative reflection for transverse-magnetic (TM) light and efficient reflection for transverse-electric (TE) light. The large anisotropy resulting from this TE-metal-like/TM-dielectric-like feature can be explained by the dispersion curve based on the Bloch theory of periodic metal-insulator-metal waveguides. The results indicate that this photon manipulation mechanism is fundamentally different from those previously proposed for 2-D or 3-D metastructures. Based on this new material platform, a novel form of metasurface holography is proposed and demonstrated, in which an image can only be reconstructed by using a TM light beam. By reducing the metamaterial structures to 1-D, our metasurface beam splitter exhibits the qualities of cost-efficient fabrication, robust performance, and high tunability, in addition to its applicability over a wide range of working wavelengths and incident angles. This development paves a foundation for metasurface structure designs towards practical metamaterial applications.