Design Of Holograms Research Articles

Metasurface orbital angular momentum holography

Allowing subwavelength-scale-digitization of optical wavefronts to achieve complete control of light at interfaces, metasurfaces are particularly suited for the realization of planar phase-holograms that promise new applications in high-capacity information technologies. Similarly, the use of orbital angular momentum of light as a new degree of freedom for information processing can further improve the bandwidth of optical communications. However, due to the lack of orbital angular momentum selectivity in the design of conventional holograms, their utilization as an information carrier for holography has never been implemented. Here we demonstrate metasurface orbital angular momentum holography by utilizing strong orbital angular momentum selectivity offered by meta-holograms consisting of GaN nanopillars with discrete spatial frequency distributions. The reported orbital angular momentum-multiplexing allows lensless reconstruction of a range of distinctive orbital angular momentum-dependent holographic images. The results pave the way to the realization of ultrahigh-capacity holographic devices harnessing the previously inaccessible orbital angular momentum multiplexing.

Faceted Fresnel DOEs creating the perception of a floating 3D virtual object under divergent illumination

An approach for the optimization and fabrication of a phase-only faceted Fresnel type diffractive optical element (FDOE) creating 3D virtual object is proposed. The FDOE is a transmissive Fresnel type DOE array, which produces the perception of a customized floating 3D virtual object behind the FDOE when illuminated with a divergent monochromatic Light Emitter Diode (LED) source. Each DOE unit of the FDOE is optimized by a modified iterative Fourier transform algorithm (M-IFTA). Every unit of the FDOE locally deflects the incident light to the same position to form a designated view in the target plane. The FDOE is fabricated using our home-built parallel writing photo-lithography machine. Numerical simulations and optical experiments are performed to verify the proposed design method. This work may find important applications in the advanced design of optical security hologram and anti-counterfeiting component.

Systematic design of multiplexed-acoustic-metasurface hologram with simultaneous amplitude and phase modulations

We propose a multiplexed-acoustic-metasurface hologram that can project multiple predesigned images at different frequencies. We demonstrate the generation of fourfold acoustic holographic images by one metasurface at 3500, 4500, 5500, and 6500 Hz, respectively, and discuss their fundamental physics. We uncover the design of this acoustic hologram which simultaneously realizes multiplexing and modulations of amplitude and phase. The proposed metasurface unit cell is composed of multiple acoustic resonant cavities leading to the multiplexing effect. We consider here both leaky and intrinsic losses, which provide simultaneous controllable manipulations of amplitude and phase. These proposed strategies significantly increase the degree of freedom of the classical metasurfaces, which may open up additional avenues for multifunctional compact acoustic devices.

Anti-counterfeiting improved by new hologram design

Anti-counterfeiting improved by new hologram design

High-Resolution Tunable Filter With Flexible Bandwidth and Power Attenuation Based on an LCoS Processor

High-resolution optical filters and wavelength selective switches are the essential components in the current and next-generation dynamic optical networks. A high-resolution programmable filter for telecom application is proposed and experimentally demonstrated based on a 4 k phase-only liquid crystal on silicon (LCoS) spatial light modulator. The tuning resolution, bandwidth, and power attenuation for each wavelength channel can be modulated independently by remote software control. For each channel, the center wavelength is tuned in the step of 7.5 $ \pm$ 1 pm and the 3 dB bandwidth achieves from 10 GHz to 3 THz. Furthermore, by multi-casting hologram design techniques for an LCoS, the power attenuation is adjusted from 0 dB to 30 dB with the step of 0.1 dB. The insertion loss is less than 6 dB across the entire C -band and 1.8 dB of it can be further improved by adopting an LCoS chip with smaller reflection loss.

Pursuing High Quality Phase-Only Liquid Crystal on Silicon (LCoS) Devices

Fine pixel size and high-resolution liquid crystal on silicon (LCoS) backplanes have been developed by various companies and research groups since 1973. The development of LCoS is not only beneficial for full high definition displays but also to spatial light modulation. The high-quality and well-calibrated panels can project computer generated hologram (CGH) designs faithfully for phase-only holography, which can be widely utilized in 2D/3D holographic video projectors and components for optical telecommunications. As a result, we start by summarizing the current status of high-resolution panels, followed by addressing issues related to the driving frequency (i.e., liquid crystal response time and hardware interface). LCoS panel qualities were evaluated based on the following four characteristics: phase linearity control, phase precision, phase stability, and phase accuracy.

Multiwavelength Multiplexing Hologram Designed Using Impedance Metasurfaces

We propose a method to generate microwave holograms using impedance metasurfaces for multiple simultaneous wavelengths. For recent impedance hologram designs in the microwave band, radiation from leaky waves can be controlled in the far field by creating holograms based on the interference of reference and object waves at a specific frequency. In our design, we vary only one physical dimension in the unit cell to simultaneously satisfy the requirement of impedance distribution for two frequencies in the same aperture. Two excitation ports are used to simultaneously generate the beams at 17 and 20 GHz. The simulation and measurement results show a very good agreement, confirming the validity of the proposed design method. The new low-profile holographic leaky-wave antenna has potential applications in designing multifrequency communication and radar systems.

Self-processing photopolymer materials for versatile design and fabrication of holographic sensors and interactive holograms

The aim of this paper is to discuss the benefits as well as the limitations of utilizing photopolymer materials in the design of holograms that are responsive to changes in their environment, such as changes in the concentration of a specific substance, temperature, and pressure. Three different case studies are presented, including both surface and volume phase holograms, in order to demonstrate the flexibility in the approach of utilizing holographic photopolymers for the design of sensors and interactive optical devices. First, a functionalized surface relief hologram is demonstrated to operate as an optical sensor for the detection of metal ions in water. The sensitivity and selectivity of the sensor are investigated. The second example demonstrates a volume transmission hologram recorded in a temperature-sensitive photopolymer and the memory effects of its exposure to elevated temperature. Finally, a pressure-sensitive reflection hologram that changes color under application of pressure is characterized, and its potential application in document authentication is described.

Analytical design for computer-generated Fourier holograms of shaded multi-polygonal three-dimensional objects

ABSTRACTWe report here on design and computer simulation of computer-generated holograms for three dimensional (3D) imaging and display. Angular spectrum of general polygon patches was calculated in closed analytical form that includes angular dependence of the intensity and linear gradient of phase at each polygon. Special attention was paid to reduction of the dynamic range in the amplitude transmittance of the hologram by proper random choices of slopes and initial phases of each polygon. Numerical computer simulation results proved that our polygon-patched design demonstrates halftones of object shades and shows expected sharp focusing of different parts of the reconstructed 3D images in their different cross-sections.

Linear solutions to metamaterial volume hologram design using a variational approach.

Multiplex volume holograms are conventionally constructed by the repeated exposure of a photosensitive medium to a sequence of external fields, each field typically being the superposition of a reference wave that reconstructs the hologram and the other being a desired signal wave. Because there are no sources of radiation internal to the hologram, the pattern of material modulation is limited to the solutions to Helmholtz's equation in the medium. If the three-dimensional structure of the medium could be engineered at each point rather than limited to the patterns produced by standing waves, more versatile structures may result that can overcome the typical limitations to hologram dynamic range imposed by sequentially superimposing holograms. Metamaterial structures and other synthetic electromagnetic materials offer the possibility of achieving high medium contrast engineered at the subwavelength scale. By posing the multiplex volume holography problem as a linear medium design problem, we explore the potential improvements that such engineered synthetic media may provide over conventional multiplex volume holograms.

Dynamic shaping of orbital-angular-momentum beams for information encoding.

Shaping complex fields with a digital micromirror device (DMD) has attracted much attention recently due to its potential application in optical communication and microscopy. In this paper, we present an optimized Lee method to achieve dynamic shaping of orbital-angular-momentum (OAM) beams using a binary DMD. An error diffusion algorithm is introduced to enhance the accuracy for binary-amplitude hologram design, making it possible to achieve high fidelity wavefront shaping while retaining a high resolution. As a proof of concept, we apply this method to create different classes of OAM beams. The numerical simulations verify that a fidelity of F > 0.985 can be achieved for all the test OAM fields with fully independent phase and amplitude modulation. Moreover, we experimentally demonstrate the dynamic shaping of different OAM beams including pure modes and mixed modes with a switching rate of up to 17.8 kHz. On this basis, accurate information encoding into the generated multiplexed OAM beams is accomplished, which provides access to high speed classical and quantum communications that employ spatial mode encoding.

Iterative pixelwise approach applied to computer-generated holograms and diffractive optical elements.

This paper presents a novel approach to optimizing the design of phase-only computer-generated holograms (CGH) for the creation of binary images in an optical Fourier transform system. Optimization begins by selecting an image pixel with a temporal change in amplitude. The modulated image function undergoes an inverse Fourier transform followed by the imposition of a CGH constraint and the Fourier transform to yield an image function associated with the change in amplitude of the selected pixel. In iterations where the quality of the image is improved, that image function is adopted as the input for the next iteration. In cases where the image quality is not improved, the image function before the pixel changed is used as the input. Thus, the proposed approach is referred to as the pixelwise hybrid input-output (PHIO) algorithm. The PHIO algorithm was shown to achieve image quality far exceeding that of the Gerchberg-Saxton (GS) algorithm. The benefits were particularly evident when the PHIO algorithm was equipped with a dynamic range of image intensities equivalent to the amplitude freedom of the image signal. The signal variation of images reconstructed from the GS algorithm was 1.0223, but only 0.2537 when using PHIO, i.e., a 75% improvement. Nonetheless, the proposed scheme resulted in a 10% degradation in diffraction efficiency and signal-to-noise ratio.

Design, fabrication and characterization of Computer Generated Holograms for anti-counterfeiting applications using OAM beams as light decoders

In this paper, we present the design, fabrication and optical characterization of computer-generated holograms (CGH) encoding information for light beams carrying orbital angular momentum (OAM). Through the use of a numerical code, based on an iterative Fourier transform algorithm, a phase-only diffractive optical element (PO-DOE) specifically designed for OAM illumination has been computed, fabricated and tested. In order to shape the incident beam into a helicoidal phase profile and generate light carrying phase singularities, a method based on transmission through high-order spiral phase plates (SPPs) has been used. The phase pattern of the designed holographic DOEs has been fabricated using high-resolution Electron-Beam Lithography (EBL) over glass substrates coated with a positive photoresist layer (polymethylmethacrylate). To the best of our knowledge, the present study is the first attempt, in a comprehensive work, to design, fabricate and characterize computer-generated holograms encoding information for structured light carrying OAM and phase singularities. These optical devices appear promising as high-security optical elements for anti-counterfeiting applications.

Coherent field propagation between tilted planes.

Propagating electromagnetic light fields between nonparallel planes is of special importance, e.g., within the design of novel computer-generated holograms or the simulation of optical systems. In contrast to the extensively discussed evaluation between parallel planes, the diffraction-based propagation of light onto a tilted plane is more burdensome, since discrete fast Fourier transforms cannot be applied directly. In this work, we propose a quasi-fast algorithm (O(N3 log N)) that deals with this problem. Based on a proper decomposition into three rotations, the vectorial field distribution is calculated on a tilted plane using the spectrum of plane waves. The algorithm works on equidistant grids, so neither nonuniform Fourier transforms nor an explicit complex interpolation is necessary. The proposed algorithm is discussed in detail and applied to several examples of practical interest.

Optimal Design of Grid-Based Binary Holograms for Matter-Wave Lithography

Grid based binary holography (GBH) is an attractive method for patterning with light or matter waves. It is an approximate technique in which different holographic masks can be used to produce similar patterns. Here we present an optimal design method for GBH masks that allows for freely selecting the fraction of open holes in the mask from below 10% to above 90%. Open-fraction is an important design parameter when making masks for use in lithography systems. The method also includes a rescaling feature that potentially enables a better contrast of the generated patterns. Through simulations we investigate the contrast and robustness of the patterns formed by masks generated by the proposed optimal design method. It is demonstrated that high contrast patterns are achievable for a wide range of open-fractions. We conclude that reaching a desired open-fraction is a trade-off with the contrast of the pattern generated by the mask.

Full-Color Plasmonic Metasurface Holograms.

Holography is one of the most attractive approaches for reconstructing optical images, due to its capability of recording both the amplitude and phase information on light scattered from objects. Recently, optical metasurfaces for manipulating the wavefront of light with well-controlled amplitude, phase, and polarization have been utilized to reproduce computer-generated holograms. However, the currently available metasurface holograms have only been designed to achieve limited colors and record either amplitude or phase information. This fact significantly limits the performance of metasurface holograms to reconstruct full-color images with low noise and high quality. Here, we report the design and realization of ultrathin plasmonic metasurface holograms made of subwavelength nanoslits for reconstructing both two- and three-dimensional full-color holographic images. The wavelength-multiplexed metasurface holograms with both amplitude and phase modulations at subwavelength scale can faithfully produce not only three primary colors but also their secondary colors. Our results will advance various holographic applications.

61-4: Holographic Diffuser Design for Multi-band Beam Shaping

Holographic diffuser with designed beam shaping functionality is of significance for various applications in lighting and display industry. We investigate the efficient optimization on a Computer Generated Hologram (CGH) design, to enable the holographic diffuser for multi-band beam shaping. Both synthetic and experimental demonstrations are presented.

用于高精度非球面面形检测的计算全息图的设计

用于高精度非球面面形检测的计算全息图的设计

Optimal design of tilt carrier frequency computer-generated holograms to measure aspherics.

Computer-generated holograms (CGHs) provide an approach to high-precision metrology of aspherics. A CGH is designed under the trade-off among size, mapping distortion, and line spacing. This paper describes an optimal design method based on the parametric model for tilt carrier frequency CGHs placed outside the interferometer focus points. Under the condition of retaining an admissible size and a tolerable mapping distortion, the optimal design method has two advantages: (1)separating the parasitic diffraction orders to improve the contrast of the interferograms and (2)achieving the largest line spacing to minimize sensitivity to fabrication errors. This optimal design method is applicable to common concave aspherical surfaces and illustrated with CGH design examples.

Spiral phase plates with radial discontinuities for the generation of multiring orbital angular momentum beams: fabrication, characterization, and application

A design of spiral phase plates for the generation of multiring beams carrying orbital angular momentum (OAM) is presented. Besides the usual helical profile, these phase plates present radial π-discontinuities in correspondence of the zeros of the associated Laguerre polynomials. Samples were fabricated by electron beam lithography over glass substrates coated with a polymethylmethacrylate resist layer. The optical response was analyzed and the purity of the generated beams was investigated in terms of Laguerre-Gaussian modes contributions. The far-field intensity pattern was compared with theoretical models and numerical simulations, while the expected phase features were confirmed by interferometric analysis with a Mach-Zehnder setup. The high quality of the output beams confirms the applicability of these phase plates for the generation of high-order OAM beams with nonzero radial index. An application consisting of the design of computer-generated holograms encoding information for light beams carrying phase singularities is presented and described. A numerical code based on an iterative Fourier transform algorithm has been developed for the computation of phase-only diffractive optical element for illumination under OAM beams. Numerical analysis and preliminary experimental results confirm the applicability of these devices as high-security optical elements for anticounterfeiting applications.