Holographic Research Articles

AI-driven pseudo-light source for achieving high coherence and low speckle noise simultaneously in dual-wavelength digital holographic microscopy

Digital holography, a promising technology for optical imaging, is limited by the fundamental challenge of speckle noise when based on coherent lasers. These approaches often compromise either coherence, affecting surface depth measurement capabilities, or introduce excessive noise, degrading image clarity. To eliminate this trade-off, this study introduces a novel solution based on an AI-driven pseudo-light source that simultaneously achieves high coherence and low speckle noise in holographic imaging. Consisting of conditional generative adversarial networks, the AI model was trained on paired holograms from both highly coherent laser light and partially coherent quantum dot (QD)-based light sources to generate holograms that mimicked the low-noise characteristics of QD-based light while retaining the high coherence length of laser. The effectiveness of the pseudo-light source was validated through holographic observations on a reflective 8.0-µm-deep specimen. Compared to the laser, the AI-driven pseudo-light source achieved substantial improvement in interference pattern clarity and reduced speckle noise contrast from 0.602 to 0.0873. Moreover, the standard deviation of the surface depth distribution was notably reduced from 215.3 nm to 44.7 nm. Quantitative phase evaluations further confirmed the preservation of accurate phase information in the generated holograms, verifying the successful reconstruction of the three-dimensional specimen structure.

The Performance of The Opening Ceremony of the 2022 Beijing Winter Olympics

This study adopts research methods such as literature review and interview to analyze the performance of the opening ceremony of the 2022 Beijing Winter Olympics. The study focuses on the Olympic concept, duration, national culture, AI use, optical application, stage design, fireworks performance, venue selection, and the relationship with technological development. give the result as follows1. Simplicity, beauty, modernity. Showcasing three themes, namely China's pursuit and longing for world peace, "Faster, Higher, Stronger, and more united", and "Together towards the future".2. The blessing of technology is more important than any previous Olympic opening ceremony performance. Human screen dance technology, holographic projection technology, AI technology empowerment, 3D lighting stage technology, double-sided screen technology, laser engraving technology, and irregular screen technology will be the main means of empowering the Olympic opening ceremony performance.3.The color scheme of the opening ceremony of the Beijing Winter Olympics is mainly cold, which blends harmoniously with the emphasis on ice and snow in the Winter Olympics.4.The development and utilization of ethnic elements in the opening ceremony performance of this Winter Olympics are reasonable and appropriate, mainly including Chinese paintings, Chinese totems, Chinese stories, Chinese proverbs, Chinese characters, Chinese clothing, etc.5.The selection of the performance venue for the opening ceremony at the National Stadium of China seems somewhat conservative.6.Reduced the fixed construction stage and replaced it with a variable and mobile stage. Technological stage. The use of LED screens makes the performance more diverse.7.The ignition ceremony highlights the ice and snow of the Winter Olympics, showcases the subtle fire in a low-key manner, highlights the theme, and also embodies the concept of low-carbon environmental protection8.The opening ceremony performance of this Winter Olympics focuses more on sports performances, downplaying artistic performances and highlighting sports characteristics. Performed by ordinary citizens, primary, secondary, and high school students, as well as young people from all over the world, emphasizing the need for everyone to come together.

Printable Spin-Multiplexed Metasurfaces for Ultraviolet Holographic Displays.

Multiplexed ultraviolet (UV) metaholograms, which are capable of displaying multiple holographic images from a single-layer device, are promising for enhancing tamper resistance and functioning as optical encryption devices. Despite considerable interest in optical security, the commercialization of UV metaholograms encounters obstacles, such as high-resolution patterning and material choices. Here, we realize spin-multiplexed UV metaholograms using a high-throughput printable platform that incorporates a zirconium dioxide (ZrO2) particle-embedded resin (PER). Utilizing ZrO2 PER, which is transparent and exhibits a refractive index of approximately 1.8 at 320 nm, we fabricated a single device capable of encoding dual holographic information depending on polarization states is fabricated. We demonstrate UV metaholograms achieving efficiencies of 56.23% with left circularly polarized incident beams and 57.28% with right circularly polarized incident beams. These multiplexed UV metaholograms fabricated using a one-step platform enable real-world applications in anticounterfeiting and encryption.

A customizable digital holographic microscope

We propose a compact, portable, and low-cost holographic microscope designed for the characterization of micrometric particles suspended in a liquid. This system is built around a commercial optical microscope by substituting its illumination source (a light-emitting diode) with a collimated laser beam. Similarly, a quartz flow cell replaces the microscope glass slide using a 3D-printed custom mount. With the hardware presented in this paper, the holographic imaging of the electromagnetic fields emitted by the particles that intercept the laser beam achieves a resolution close to that of optical microscopes but with a greater depth of field. Several morphological and optical features can be extracted from the holograms, including particle projected section, aspect ratio, and extinction cross-section. Additionally, we introduce a remote system control that enables users to process the acquired holograms on a remote computational device. This work provides a comprehensive description of the methodology of image processing in holographic microscopy and a series of validation measurements conducted using calibrated particles. This technique is suitable for the characterization of airborne particles found in snow, firn, and ice; here we report experimental results obtained from Alpine ice cores.

Recent Advances in Geometric Phase Metasurfaces: Principles and Applications

AbstractThe concept of geometric phase traversing numerous domains in physics and has been a continuous source of fascination and inspiration for researchers. Despite the extensive research surrounding geometric phase from decades, advances in technology continue to yield novel theories, innovative devices, and captivating applications, extending even to the realm of subwavelength scales. This review article provides a comprehensive exploration of geometric phase metasurfaces, delving into their design principles and categorizing them based on materials properties. In addition, multi‐fold and reconfigurable metasurfaces based on geometric principle are further explored with their unique capabilities and potential impact on a diverse range of applications, including beam steering, lensing, polarization conversion, and holographic imaging. By examining the state‐of‐the‐art in geometric phase metasurfaces, insights are aimed to offer into their current capabilities and limitations. Finally, the prospects and challenges are discussed that lie ahead for this promising field, paving the way for future advancements and innovations.

Metasurface-Embedded Contact Lenses for Holographic Light Projection.

Contact lenses have been instrumental in vision correction and are expected to be utilized in augmented reality (AR) displays through the integration of electronic and optical components. In optics, metasurfaces, an array of sub-wavelength nanostructures, have offered optical multifunctionality in an ultra-compact form factor, facilitating integration into various imaging, and display systems. However, transferring metasurfaces onto contact lenses remains challenging due to the non-biocompatible materials of extant imprinting methods and the structural instability caused by the swelling and shrinking of the wetted surface. Here, a biocompatible method is presented to transfer metasurfaces onto contact lenses using hyaluronic acid (HA) as a soft mold and to allow for holographic light projection. A high-efficiency metahologram is obtained with an all-metallic 3D meta-atom enhanced by the anisotropy of a rectangular structure, and a reflective background metal layer. A corrugated metal layer on the HA mold is supported with a SiO2 capping layer, to avoid unwanted wrinkles and to ensure structural stability when transferred to the surface of pliable and wettable contact lenses. Biocompatible method of transferring metasurfaces onto contact lenses promises the integration of diverse optical components, including holograms, lenses, gratings and more, to advance the visual experience for AR displays and human-computer interfaces.

High-security holographic display with content and copyright protection based on complex amplitude modulation

The computer-generated hologram provides an approach to modulate the coherent wavefront and has been widely applied in holographic displays. In the actual application, holograms need to be transmitted through the network, which results in the illegal acquisition and malicious manipulation of holographic images. Therefore, it is necessary to develop a practical method to protect the content and copyright of holographic images. In this paper, we develop a high-security holographic display method based on complex amplitude modulation. In our proposed method, the complex hologram of a holographic image is decomposed into two phase-only holograms, one of which is designed as the ciphertext, and the other is regarded as the key. As a result, the holographic image can be reconstructed only when the ciphertext and the key are paired, which boosts the security of the holographic image. Meanwhile, the copyright of the holographic image is protected via a watermark that is embedded in the ciphertext in the form of a hologram. Due to the simultaneous use of encryption and watermark technology, our proposed method could transmit holographic images at a high security level, and has great potential to be applied in holographic displays in the future.

Holographic interferometric vibration measurement based on photorefractive crystal in diffusion mode

A dynamic holographic vibration measurement system based on a photorefractive crystal of BSO in diffuse mode without the need for an external electric field, which allows for simultaneous measurement of in-plane and out-of-plane high-frequency vibrations, is studied theoretically and experimentally in this work. By adjusting the polarization state of the reference beam, the system introduces a necessary additional phase shift of π/2 to achieve highly sensitive and linear demodulation of small phase-to-intensity vibration signals. Both theoretical analysis and experimental results confirm the system's practicality and safety, demonstrating its ability to accurately detect vibrations without the risks associated with high-voltage drift mode operation. Furthermore, some factors that affect measurement sensitivity were analyzed. The results of measuring in-plane and out-of-plane vibrations showcase the system's superior performance in measuring submicron magnitude vibrations at the MHz level.

Parallel detection structure exploiting the extrinsic information from the serial detection in the holographic data storage system

Parallel detection structure exploiting the extrinsic information from the serial detection in the holographic data storage system

Compact common-path polarization holography for measurement of the Jones matrix of polarization-sensitive materials

A compact common-path off-axis digital holographic imaging method is proposed utilizing polarization-angular-multiplexing for Jones matrix measurement. Our method employs a common-path off-axis configuration to capture multiplexed off-axis interferograms generated by orthogonally polarized object beams and a reference beam on a monochrome CCD camera. The modulation of the fringe direction is achieved by two homemade retro-reflector mirrors, allowing for the retrieval of the Jones matrix distribution of transparent specimens through a matrix-division algorithm. The stable common-path design and the expansive camera field of view facilitate the extraction of spatially resolved Jones matrix parameters. The feasibility of this method was validated through experiments involving standard objects and polarization-sensitive materials, conducted at both general and microscopic scales. Our system completed polarization imaging of cancerous tissues, unequivocally demonstrating its extraordinary potential in medical pathology diagnostics.

Universal constraints on energy flow and SYK thermalization

We study the dynamics of a quantum system in thermal equilibrium that is suddenly coupled to a bath at a different temperature, a situation inspired by a particular black hole evaporation protocol. We prove a universal positivity bound on the integrated rate of change of the system energy which holds perturbatively in the system-bath coupling. Applied to holographic systems, this bound implies a particular instance of the averaged null energy condition. We also study in detail the particular case of two coupled SYK models in the limit of many fermions using the Schwinger-Keldysh non-equilibrium formalism. We solve the resulting Kadanoff-Baym equations both numerically and analytically in various limits. In particular, by going to low temperature, this setup enables a detailed study of the evaporation of black holes in JT gravity.

Anti-noise performance analysis in amplitude-modulated collinear holographic data storage using deep learning

In an amplitude-modulated collinear holographic data storage system, optical system aberration and experimental noise due to the recording medium often result in a high bit error rate (BER) and low signal-to-noise ratio (SNR) in directly read detector data. This study proposes an anti-noise performance analysis using deep learning. End-to-end convolutional neural networks were employed to analyze noise resistance in encoded data pages captured by the detector. Experimental results demonstrate that these networks effectively correct system imaging aberrations, detector light intensity response, holographic storage medium response non-uniformity, and defocusing noise from the recording objective lens. Consequently, the BER of reconstructed encoded data pages can be reduced to 1/10 of that from direct detection, while the SNR can be increased more than fivefold, enhancing the accuracy and reliability of data reading in amplitude holographic data storage systems.

Experimental analysis of ice crystal size–velocity correlation in icing wind tunnel with digital holographic particle tracking velocimetry

The ice crystal icing in aero-engines poses a significant threat to aircraft flight safety, and investigating the correlation between ice crystal size and velocity in icing wind tunnels is essential for correlating ground tests with flight conditions. In this paper, a digital holographic particle tracking velocimetry system is developed and integrated with an icing wind tunnel, and the ice crystal size and velocity are simultaneously measured in experiments at four different wind speeds. The velocity difference between the ice crystal and wind has been experimentally observed, and it increases with both the ice crystal size and wind speed. The normalized velocities of the ice crystals by the wind speeds decrease with size, and the maximum velocity difference in the experiments reaches 28% of the wind speed. Additionally, quantitative correlations between ice crystal size and normalized velocity based on the power function and polynomial model are established. The relationship between the particle Reynolds number of ice crystal and size is also analyzed, resulting in the development of a model based on the power function, and the power index ranges from 1.51 to 1.64. These findings will provide valuable assistance in the calibration and commissioning of the ice crystal simulation system in icing wind tunnels, as well as in exploring the correlation between ground icing tests and flight and in developing corresponding models.

High-resolution Holographic Image Reconstruction Based on Deep Learning

High-resolution Holographic Image Reconstruction Based on Deep Learning

High-efficiency, broadband, and low-crosstalk 3D holography by multi-layer holographic-lens integrated metasurface

High-efficiency, broadband, and low-crosstalk 3D holography by multi-layer holographic-lens integrated metasurface

Holographic entanglement entropy of disk in insulator/superconductor transition with logarithmic nonlinear electrodynamics

We explore the holographic phase transition with logarithmic nonlinear electrodynamics in the backgrounds of the AdS soliton away from the probe limit. We disclose the properties of phases by the holographic entanglement entropy of disk for the scalar operators. We find that the holographic entanglement entropy is a useful tool to probe the critical chemical potential and the order of the phase transition in the system. In the superconductor phase, the holographic entanglement entropy for scalar operator <O+> has a non-monotonic behavior as the chemical potential increases, while the entanglement entropy for operator <O−> decreases monotonously. With the increase of the logarithmic nonlinear factor b, the holographic entanglement entropy becomes bigger for both scalar operators <O±>. Furthermore, the insulator/superconductor phase transition probed by the entanglement entropy in the holographic system is characterized only by the chemical potential and is independent of the logarithmic nonlinear electrodynamics.

Speckle noise suppression of a reconstructed image in digital holography based on the BM3D improved convolutional neural network

In digital holographic measurement, when light waves pass through inhomogeneous media or surfaces, speckle noise is generated, resulting in random, granular light and dark spots in the hologram, which greatly reduces the image quality. Therefore, in order to improve the image quality of holographic reconstruction, a noise reduction method based on the BM3D improved convolutional neural network (CNN) is proposed in this paper. Firstly, the similarity and important statistical information between blocks can be obtained by using BM3D. Then, the denoising convolutional neural network (DnCNN) is used to learn the relationship between the noise of a large number of samples and the noise image, and further purify the image to retain the details for a better denoising effect. Finally, a reflective off-axis digital holographic optical path system is constructed to collect the holograms of the test samples, and the reconstructed images are obtained by the Fresnel diffraction method to constitute a dataset with the simulated holographic reconstructed images to validate the proposed method in this paper, compared to the other methods, such as DnCNN, convolutional blind denoising network (CBDNet), BM3D, and Wiener filtering. The experimental results of qualitative and quantitative analyses show that the proposed method combines the advantages of traditional algorithms and deep learning, significantly enhances the robustness of the system, optimizes the denoising performance, and preserves the details of the reconstructed image to the greatest extent.

A comprehensive review of quality of experience for emerging video services

The recent advances in multimedia technology have significantly expanded the range of audio–visual applications. The continuous enhancement of display quality has led to the emergence of new attributes in video, such as enhanced visual immersion and widespread availability. Within media content, the video signals are presented in various formats including stereoscopic/3D, panoramic/360°and holographic images. The signals are also combined with other sensory elements, such as audio, tactile, and olfactory cues, creating a comprehensive multi-sensory experience for the user. The development of both qualitative and quantitative Quality of Experience (QoE) metrics is crucial for enhancing the subjective experience in immersive scenarios, providing valuable guidelines for system enhancement. In this paper, we review the most recent achievements in QoE assessment for immersive scenarios, summarize the current challenges related to QoE issues, and present outlooks of QoE applications in these scenarios. The aim of our overview is to offer a valuable reference for researchers in the domain of multimedia delivery.

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.

Holographic Einstein rings of a black hole with a global monopole

The global monopole solutions which give rise to quite unusual physical phenomena have captured considerable attention. In this paper, we study the Einstein ring of the spherically symmetric AdS black hole solution with a global monopole based on the AdS/CFT correspondence. With the help of the given response function of the QFT on the boundary, we construct the holographic images of the black hole in the bulk. Our results exhibit the absolute amplitude of total response function |⟨O⟩|\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$|\\langle \\mathcal {O}\\rangle |$$\\end{document} increases with the decrease of the monopole parameter b and the temperature T. And the frequency ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\omega $$\\end{document} of the Gaussian source will also increase the absolute amplitude. These parameters also affects the Einstein ring. With the change of the observation position, this ring will change from the concentric stripe to a luminosity-deformed ring, or light points. And the monopole parameter has an effect on the brightness and the position of Einstein ring. All these results imply that the holographic images can be used as an effective tool to distinguish different types of black holes for fixed wave source and optical system. These theoretical proposal opens a door to gravitational phenomena on strongly correlated material. Therefore, the holographic Einstein ring is of great theoretical and experimental significance for our research. In theory, it provides us a new way to find a necessary condition for the existence of the dual black hole. And experimentally speaking, if we can realize suitable targets for observing AdS black holes successfully, we would be able to observe Einstein rings by tabletop experiments when we apply localized sources on such materials and measure their responses.