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Diffractive optical elements (DOEs) represent a revolutionary advancement in modern optics, offering unparalleled versatility and efficiency in various applications. Their significance lies in their ability to manipulate light waves with intricate patterns, enabling functionalities beyond what traditional refractive optics can achieve. DOEs find widespread use in fields such as laser beam shaping, holography, optical communications, and imaging systems. By precisely controlling the phase and amplitude of light, DOEs can generate complex optical structures, correct aberrations, and enhance the performance of optical systems. Moreover, their compact size, lightweight nature, and potential for mass production make them indispensable in designing compact and efficient optical devices for diverse industrial and scientific applications. From improving the performance of laser systems to enabling innovative display technologies, DOEs continue to drive advancements in modern optics, promising even more exciting possibilities in the future. In this review, the critical importance of DOEs is illuminated and explore their profound implications in the contemporary era. [ABSTRACT FROM AUTHOR]

Diffractive optical elements (DOEs) enable precise control over the direction and filtering of light, making them common components in spectrometers, waveguides, and sensors. There is great interest in tunable and sub‐micron diffractive optical elements in flexible photonics and for responsive structural colors. Here this study presents sub‐micron tunable diffraction gratings produced by patterning a liquid crystal elastomer (LCE). The intrinsic anisotropic deswelling of the liquid crystal elastomer enables sub‐micron (707 nm) pitch structures to be produced from a micron‐scale (1040 nm) surface relief grating. Using atomic force microscopy (AFM) and diffraction measurements, a thermal pitch tunability is demonstrated of +212 nm (+31%) or −322 nm (−33%) over a temperature range of 215 °C depending on grating orientation. A mechanical pitch tunability is demonstrate of +1110 nm by applying strains of up to 157% to the liquid crystal elastomer. The height of the diffraction grating is preserved over strain due to the negative Poisson‐ratio, or "auxetic", behavior exhibited by this chosen family of the liquid crystal elastomers. This report opens the possibility of using LCEs to facilitate flexible sub‐micron diffractive optical elements, with a high degree of tunability for sensing and structural color applications. [ABSTRACT FROM AUTHOR]

The article provides an overview of advanced micro- and nano-scale photonics research in Asia, highlighting recent progress and innovations in this rapidly evolving field. Topics discussed include cutting-edge developments in optical devices, novel fabrication methods, and advancements in energy-efficient building materials.

Multifunctionality, integration, and miniaturization are the mainstream trends in modern device development. However, optical display and depth perception, essential for innovative applications like intelligent driving and mixed reality, are typically achieved separately in complex and bulky optical systems. Metasurfaces, ultrathin artificial optical surfaces with strong light–matter interaction capabilities at the nanoscale, offer a versatile platform for creating multifunctional, highly integrated, and miniaturized devices by fully exploring spatial multiplexing and utilizing variables like location, polarization, and frequency. In this study, a multifunctional metasurface that integrates meta‐holography with Dammann gratings is presented. By engineering the phase profile, the device can display specific holographic images in the Fresnel region while simultaneously producing a high‐density spot cloud with over 37 000 spots covering the entire half space. As a proof‐of‐concept, a projection and reconstruction experiment is performed to elaborate its potential for retrieving three‐dimensional (3D) spatial information of real scenarios. The simultaneous generation of display and point cloud holds significant promise for applications in cutting‐edge imaging technologies such as intelligent driving and robot vision. [ABSTRACT FROM AUTHOR]

In the expanding fields of mobile technology and augmented reality, there is a growing demand for compact, high‐fidelity spectral imaging systems. Traditional spectral imaging techniques face limitations due to their size and complexity. Diffractive optical elements (DOEs), although helpful in reducing size, primarily modulate the phase of light. Here, an end‐to‐end computational spectral imaging framework based on polarization‐multiplexed metalens is introduced. A distinguishing feature of this approach lies in its capacity to simultaneously modulate orthogonal polarization channels. When harnessed in conjunction with a neural network, it facilitates the attainment of high‐fidelity spectral reconstruction. Importantly, the framework is intrinsically fully differentiable, a feature that permits the joint optimization of both the metalens structure and the parameters governing the neural network. The experimental results presented herein validate the exceptional spatial‐spectral reconstruction performance, underscoring the efficacy of this system in practical, real‐world scenarios. This innovative approach transcends the traditional boundaries separating hardware and software in the realm of computational imaging and holds the promise of substantially propelling the miniaturization of spectral imaging systems. [ABSTRACT FROM AUTHOR]

With the advancement of computational imaging, a large number of spectral imaging systems based on encoding–decoding have emerged, among which phase‐encoding spectral imaging systems have attracted widespread interest. Conventional phase‐encoding systems suffer from severe image degradation and limited light throughput. To address these challenges and achieve video‐rate spectral imaging with high spatial resolution and spectral accuracy, a novel optical system based on diffractive‐refractive hybrid optics is proposed. Here, a diffractive optical element is employed to perform imaging and dispersion functions, while a rear lens is used to shorten the system's back focal length and reduce the size of the point spread function. Meanwhile, convolutional neural network‐based spectral reconstruction algorithms are employed to reconstruct the spectral data cubes from diffraction blurred images. A compact, cost‐effective, and portable prototype has been constructed, demonstrating the capability to acquire and reconstruct 30 spectral data cubes per second, each with dimensions of 1080×1280×43${1080 \times 1280 \times 43}$ in the spectral range of 480–900 nm with a 10 nm spectral interval. The optical system has the potential to broaden the application scope of phase‐encoding spectral imaging systems in various scenarios. [ABSTRACT FROM AUTHOR]

To meet the spatial perception requirements for autonomous ship navigation in common scenarios such as ocean navigation, port entry and exit, and lock passage, commercial vehicle-mounted LiDAR technology falls short of demands in aspects such as sensing distance, field of view, angular resolution, and spatial sampling density. This paper proposes a hundred-beam-scale LiDAR scheme based on large-field-of-view diffractive beam splitting and a fiber array for echo reception and presents an in-depth investigation of the angular nonuniformity of diffractive beam splitting and the microradian-scale alignment for such hundred-beam-scale large-field-of-view LiDAR. This paper considers a combination of split-beam transmission based on a high-order diffractive optical element (DOE) and echo reception based on a high-precision fiber-optic line array. The nonlinear angular characteristics of the DOE are deduced and analyzed for a large field of view. The units of the receiving fiber-optic array are designed to offset the influence of the angular nonlinearity of the DOE, ensuring high-precision receiver–transmitter alignment of the hundred-beam-scale LiDAR for beams at any order of diffraction and helping to reduce system errors. The above-described LiDAR system has undergone laboratory testing and practical engineering verification, and it provides a new optical solution for LiDAR systems at the hundred-beam scale with a large field of view, a small divergence angle, and high sampling density. The presented system achieves a registration accuracy of 66.5 μrad with 128 beams and a 10-degree field of view, greatly improving signal reception efficiency. Such LiDAR systems have a wide range of applications, including space docking, target identification, lunar and planetary exploration, and ground-based vehicle-mounted LiDAR. [ABSTRACT FROM AUTHOR]

We consider the problem of designing a diffractive neural network (DNN) consisting of a set of sequentially placed phase diffractive optical elements (DOEs) and intended for the optical solution of several given classification problems at different operating wavelengths, so that each classification problem is solved at the corresponding wavelength. The problem of calculating the DNN is formulated as the problem of minimizing a functional that depends on the functions of the diffractive microrelief height of the DOEs constituting the DNN and represents the error in solving the given classification problems at the operating wavelengths. We obtain explicit and compact expressions for the derivatives of this functional, and using them, we formulate a gradient method for the DNN calculation. Using this method, we design DNNs for solving the following three classification problems at three different wavelengths: the problem of classifying handwritten digits from the MNIST database, the problem of classifying fashion products from the Fashion MNIST database, and the problem of classifying ten handwritten letters from the EMNIST database. The presented simulation results of the designed DNNs demonstrate the high performance of the proposed method. [ABSTRACT FROM AUTHOR]

Usually, optical tweezers for trapping atoms or nanoparticles are based on the focusing of a Gaussian laser beam (GB). The optical trap is characterised by its longitudinal stability (LS), expressed as the ratio of the backward axial gradient and the forward scattering forces. Replacing the GB with a LGp0 beam (one central peak surrounded by p rings) does not improve the LS because the on-axis intensity distribution is the same whatever the mode order p. However, it has been recently demonstrated that a restructured LGp0 beam can improve greatly the LS. In this paper, we consider the restructuring of a LGp0 beam when passing through a simple binary diffracting optical element called a circular π-plate (CPP). For a particular radius of the dephasing zone of the CPP, it is found that the LS is multiplied by a factor corresponding to a relative increase of about 220% to 320%. [ABSTRACT FROM AUTHOR]

The capability to use extreme ultraviolet (EUV) light for generating transient gratings (TGs) has enabled the study of thermoelastic and magnetic dynamics at the nanoscale, in thin solid samples and surfaces, without the need of specially modifying them. However, the current mirror-based setup for generating EUV TG limits both its extension to the soft x-ray photon energy range and the attainment of few femtosecond time-resolution. Here we propose to overcome these limitations with an alternative experimental scheme based on diffractive optical elements that has become feasible with the current technology. In addition, some aspects of the discussed setup may facilitate the implementation of the EUV TG approach at table-top high-harmonic generation sources. [ABSTRACT FROM AUTHOR]

Background: Indocyanine green (ICG) exhibits robust absorption near 800 nm. Aims: To examine the clinical effects of combining ICG with a 785 nm picosecond laser for treating photo‐aged skin. Patient/Methods: A 785 nm 600 picosecond laser was used on the facial area of 16 female patients with Fitzpatrick skin type III and IV (mean age: 58.44 ± 5.24 years) after applying 0.0125% ICG cream. A total of 3000 shots were administered in diffractive optical element mode at a pulse energy of 200 mJ and frequency of 10 Hz. Hyperpigmented lesions were treated using the Zoom handpiece set at a spot size of 3–4 mm, pulse energy of 60–120 mJ, and frequency of 3–7 Hz. Patients underwent five sessions of treatment at intervals of 1–2 weeks. Wrinkles, pores and pigmented lesions were assessed at the initial assessment and 4 weeks after the final treatment using the Modified Fitzpatrick Wrinkle Scale and 10‐point visual analog scale, respectively. Skin biopsy of the postauricular area was performed on two consenting patients. Results: Significant improvements in wrinkles (p = 0.02), pores (p = 0.034), and hyperpigmentation (p = 0.036) were observed, along with increased patient subjective improvement. Adverse effects were transient and well‐tolerated. Hematoxylin and eosin and Masson's trichrome staining revealed increased and thickened dermal collagen fibers. Immunohistochemical staining revealed increased expression of collagen I and III throughout the papillary and upper reticular dermis, along with diffuse increase of STRO‐1 in the dermis. Conclusions: The combined application of a 785 nm picosecond laser and ICG yielded promising clinical outcomes for treating photo‐aged skin in Asian patients with Fitzpatrick skin type III and IV. [ABSTRACT FROM AUTHOR]

Optical computing has been proven to have the ability to process information with ultra‐high speed. Here, an all‐optical feature extraction system via sparse representation (AFE‐SR) is introduced. The AFE‐SR, which is achieved by multiple diffractive optical elements (DOEs), can realize the recognition of generated physical fields with the speed of light. The sparse representation simplifies the target and improves the recognition accuracy. With the mathematical analysis principle of sparse optical features extraction and optical integration, the identification accuracy of the generation of physical fields is 100% in 2100 frames of the experimental videos. The application field of optical computing systems is extended to state recognition. [ABSTRACT FROM AUTHOR]

We introduce an information-hiding camera integrated with an electronic decoder that is jointly optimized through deep learning. This system uses a diffractive optical processor, which transforms and hides input images into ordinary-looking patterns that deceive/mislead observers. This information-hiding transformation is valid for infinitely many combinations of secret messages, transformed into ordinary-looking output images through passive light-matter interactions within the diffractive processor. By processing these output patterns, an electronic decoder network accurately reconstructs the original information hidden within the deceptive output. We demonstrated our approach by designing information-hiding diffractive cameras operating under various lighting conditions and noise levels, showing their robustness. We further extended this framework to multispectral operation, allowing the concealment and decoding of multiple images at different wavelengths, performed simultaneously. The feasibility of our framework was also validated experimentally using terahertz radiation. This optical encoder-electronic decoder-based codesign provides a high speed and energy efficient information-hiding camera, offering a powerful solution for visual information security. [ABSTRACT FROM AUTHOR]

Phase imaging is widely used in biomedical imaging, sensing, and material characterization, among other fields. However, direct imaging of phase objects with subwavelength resolution remains a challenge. Here, we demonstrate subwavelength imaging of phase and amplitude objects based on all-optical diffractive encoding and decoding. To resolve subwavelength features of an object, the diffractive imager uses a thin, high-index solid-immersion layer to transmit high-frequency information of the object to a spatially-optimized diffractive encoder, which converts/encodes high-frequency information of the input into low-frequency spatial modes for transmission through air. The subsequent diffractive decoder layers (in air) are jointly designed with the encoder using deep-learning-based optimization, and communicate with the encoder layer to create magnified images of input objects at its output, revealing subwavelength features that would otherwise be washed away due to diffraction limit. We demonstrate that this all-optical collaboration between a diffractive solid-immersion encoder and the following decoder layers in air can resolve subwavelength phase and amplitude features of input objects in a highly compact design. To experimentally demonstrate its proof-of-concept, we used terahertz radiation and developed a fabrication method for creating monolithic multi-layer diffractive processors. Through these monolithically fabricated diffractive encoder-decoder pairs, we demonstrated phase-to-intensity (P → I) transformations and all-optically reconstructed subwavelength phase features of input objects (with linewidths of ~ λ/3.4, where λ is the illumination wavelength) by directly transforming them into magnified intensity features at the output. This solid-immersion-based diffractive imager, with its compact and cost-effective design, can find wide-ranging applications in bioimaging, endoscopy, sensing and materials characterization. [ABSTRACT FROM AUTHOR]

Speckle pattern-based remote vibration monitoring has recently become increasingly valuable in industrial, commercial, and medical applications. The dynamic and random nature of speckle patterns offers practical applications for imaging and measurement systems. The speckle pattern is an interference pattern generated by light scattered from a rough surface onto a remote plane. It is typically sensed using area scan cameras (2D), which are limited to framerates of 2–4 kHz and can only capture a small region of interest (ROI). In this work, we propose a technique that enables the capture of synthetic 2D speckle patterns using a 1D high-acquisition-rate sensor and a diffractive optical element (DOE) to produce image replicas. The multiple replicas are scanned by the 1D sensor simultaneously at different spatial positions. This method provides an ability to sense remote vibrations in all directions, contrary to the case with a simple 1D sensing system. [ABSTRACT FROM AUTHOR]

Quasi-continuous-phase metasurfaces overcome the side effects imposed by high-order diffraction on imaging and can impart optical parameters such as amplitude, phase, polarization, and frequency to incident light at sub-wavelength scales with high efficiency. Structured-light three-dimensional (3D) imaging is a hot topic in the field of 3D imaging because of its advantages of low computation cost, high imaging accuracy, fast imaging speed, and cost-effectiveness. Structured-light 3D imaging requires uniform diffractive optical elements (DOEs), which could be realized by quasi-continuous-phase metasurfaces. In this paper, we design a quasi-continuous-phase metasurface beam splitter through a vector iterative Fourier transform algorithm and utilize this device to realize structured-light 3D imaging of a target object with subsequent target reconstruction. A structured-light 3D imaging system is then experimentally implemented by combining the fabricated quasi-continuous-phase metasurface illuminated by the vertical-cavity surface-emitting laser and a binocular recognition system, which eventually provides a new technological path for the 3D imaging field. [ABSTRACT FROM AUTHOR]

Diffractive optical elements (DOEs) provide significant advantages over refractive optical elements due to their flexible design capabilities, leading to increasing usage in electro-optical systems. When the transmission function of diffractive lenses can be known analytically, determining the point spread function (PSF) becomes straightforward. However, in cases where analytical transmission equations cannot be derived, a general approach is necessary. In this study, we propose a new method that can be applied to any type of DOE to determine the numerical PSF. The simulation results are then compared to analytical and numerical methods. The findings of this research make significant contributions to the advancement of diffractive lenses by addressing the challenge of designing and analyzing these diffractive lenses. By offering a general approach for determining the PSF, the modulation transfer function (MTF) of the elements can also be determined by the proposed approach, even when the specific transmission function is difficult to ascertain. This study provides important contributions to the development of DOEs. [ABSTRACT FROM AUTHOR]

Diffractive neural networks (DNNs) are emerging as a new machine learning hardware based on optical diffraction with parallel and high‐throughput information processing. The optical inputs to DNNs are spatially modulated by propagating through passive diffractive layers that work in succession to achieve an inference. Herein, visible wavelength classification using single‐ and two‐layer DNNs fabricated using direct laser writing is demonstrated. The proposed DNN approach accepts the point spread function of two different wavelengths modeled after a microscope objective as the input and modulates the input field toward the target detector for classification. Of the three models trained to classify different wavelength pairs, the highest performance observed is for the classification of 561 and 785 nm, achieving over 90% accuracy. This work demonstrates the potential of all‐optical artificial neural networks for applications requiring visible wavelengths, from visible light beam shaping to spectral analysis and optical imaging. [ABSTRACT FROM AUTHOR]

Reflective LCDs have a great advantage of low power consumption, but the brightness is not consistently sufficient because ambient light is used as a light source. To increase light efficiency, we combined reflective LCDs and the Pancharatnam‐Berry deflector (PBD), a diffractive optical element that controls the propagation of incident light. We confirmed that on‐axis brightness is increased by 2.2 times against the incident collimated light from a polar angle of 30° when compared to a reflective LCD without PBD. [ABSTRACT FROM AUTHOR]

Diffractive Optical Elements (DOEs) are indispensable tools across numerous technological domains due to their capacity to manipulate light with sophistication and versatility. Their compact dimensions, lightweight nature, and compatibility with diverse materials render DOEs as prime candidates for integration into various optical systems, spanning from consumer electronics to state‐of‐the‐art scientific devices. Thus, DOEs stand as essential catalysts in technological advancement, facilitating innovation and unlocking new applications across a broad spectrum of disciplines. In this comprehensive review paper, Numerous types of DOEs widely acknowledge for their efficacy in both free space optics and imaging applications are delved. Beyond mere enumeration, their practical applications, elucidating their transformative impact on these fields are carefully examined. Furthermore, the challenges encountered in their implementation are dissected, paving the way for insightful discussions on future trajectories and advancements. [ABSTRACT FROM AUTHOR]

We present an azimuthal-rotation-controlled dynamic nanoinscribing (ARC-DNI) process for continuous and scalable fabrication of asymmetric nanograting structures with tunable periods and shape profiles. A sliced edge of a nanograting mold, which typically has a rectangular grating profile, slides over a polymeric substrate to induce its burr-free plastic deformation into a linear nanopattern. During this continuous nanoinscribing process, the "azimuthal angle," that is, the angle between the moving direction of the polymeric substrate and the mold's grating line orientation, can be controlled to tailor the period, geometrical shape, and profile of the inscribed nanopatterns. By modulating the azimuthal angle, along with other important ARC-DNI parameters such as temperature, force, and inscribing speed, we demonstrate that the mold-opening profile and temperature- and time-dependent viscoelastic polymer reflow can be controlled to fabricate asymmetric, blazed, and slanted nanogratings that have diverse geometrical profiles such as trapezoidal, triangular, and parallelogrammatic. Finally, period- and profile-tunable ARC-DNI can be utilized for the practical fabrication of diverse optical devices, as is exemplified by asymmetric diffractive optical elements in this study. [ABSTRACT FROM AUTHOR]

Nanoparticles (NPs) generated by pulsed‐laser ablation in liquids (PLAL) have benefited many key applications due to their versatility, enlarged surface area, and high purity. However, scaling up NPs production represents one of the main requisites to commercialize this technology. The established upscaling strategy demands high power and repetition rate laser source with fast scanning systems, which are not widely available and costly. Herein, a cost‐effective alternative is proposed, the addition of static diffractive optical elements to achieve parallel processing through the multi‐beam PLAL (MB‐PLAL). In MB‐PLAL, the optimum repetition rate is reduced to compensate laser energy splitting, hence achieving a higher interpulse distance, reducing pulse shielding, and increasing NPs productivity. MB‐PLAL with 11 beams reached a factor 4 productivity increase for iron–nickel alloy (Fe50Ni50) NPs compared to the single‐beam setup (0.4–1.6 g h−1), and a factor 3 increase for gold (Au) NPs (0.32–0.94 g h−1). The scalability of the proposed MB‐PLAL technique setup is confirmed by Au and Fe50Ni50 NPs productivity experiments using 1, 6, and 11 beams, showing a linear increase in productivity. [ABSTRACT FROM AUTHOR]

An improved algorithm for diffractive optical element (DOE) with high imaging quality is proposed in this paper. The algorithm is designed based on amplitude division between signal and noise regions, further subdivides the noise region into two distinct parts. The image quality in the signal region will be effectively improved by employing a partition-constraint strategy, which imposes amplitude freedom on the first noise region while enforcing strict amplitude constraints on the second noise region. The principle of the algorithm, simulation analysis, and experimental results are presented. The simulation and experimental results demonstrate that the algorithm is feasible. [ABSTRACT FROM AUTHOR]

High-order cylindrical vector beams possess flexible spatial polarization and exhibit new effects and phenomena that can expand the functionality and enhance the capability of optical systems. However, building a general analytical model for highly focused beams with different polarization orders remains a challenge. Here, we elaborately develop the vector theory of high-order cylindrical vector beams in a high numerical aperture focusing system and achieve the vectorial diffraction integrals for describing the tight focusing field with the space-variant distribution of polarization orders within the framework of Richards–Wolf diffraction theory. The analytical formulae include the exact three Cartesian components of electric and magnetic distributions in the tightly focused region. Additionally, utilizing the analytical formulae, we can achieve the gradient force, scattering force, and curl-spin force exerted on Rayleigh particles trapped by high-order cylindrical vector beams. These results are crucial for improving the design and engineering of the tightly focused field by modulating the polarization orders of high-order cylindrical vector beams, particularly for applications such as optical tweezers and optical manipulation. This theoretical analysis also extends to the calculation of complicated optical vortex vector fields and the design of diffractive optical elements with high diffraction efficiency and resolution. [ABSTRACT FROM AUTHOR]

The ability of liquid crystal to self‐organize into complicated structures can be harnessed in applications such as thin film optical devices, diffraction gratings or smart windows. In this work we focus on liquid crystal layers in contact with one or two substrates that have been patterned by photoalignment. This leads to geometric phase gratings, in which the phase of transmitted or reflected light depends on the location on the substrate. It has been shown that geometric phase gratings with uniform rotation can achieve very high diffraction efficiencies (>90%) for incident light that is circularly polarized. [ABSTRACT FROM AUTHOR]

Diffractive deep neural networks (D2NNs) have brought significant changes in many fields, motivating the development of diverse optical computing components. However, a crucial downside in the optical computing components is employing diffractive optical elements (DOEs) which were fabricated using commercial 3D printers. DOEs simultaneously suffer from the challenges posed by high-order diffraction and low spatial utilization since the size of individual neuron is comparable to the wavelength scale. Here, we present a design of D2NNs based on all-dielectric metasurfaces which substantially reduces the individual neuron size of net to scale significantly smaller than the wavelength. Metasurface-based optical computational elements can offer higher spatial neuron density while completely eliminate high-order diffraction. We numerically simulated an optical half-adder and experimentally verified it in the terahertz frequency. The optical half-adder employed a compact network with only two diffraction layers. Each layer has a size of 2 × 2 cm2 but integrated staggering 40,000 neurons. The metasurface-based D2NNs can further facilitate miniaturization and integration of all optical computing devices and will find applications in numerous fields such as terahertz 6G communication, photonics integrated circuits, and intelligent sensors. [ABSTRACT FROM AUTHOR]

A rapid and robust method to fabricate transmission diffractive optical elements in the visible wavelengths is presented. By additive manufacturing of a polymeric photo-resin using 2-photon lithography followed by encasing of the structure in another resin with similar refractive index, the height of the structure can be made much larger, thus trading-off fabrication height for refractive index difference of the two materials. After adjusting for resin shrinkage, different diffractive optical element designs including an m = 1 vortex plate, and Laguerre-Gaussian beams with azimuthal and radial indices of (1,1), (1,2), and (2,1) were demonstrated. Experimental results show intensity patterns matching that of simulations, including size and features, although some aberration was observed, possibly due to fabrication tolerance errors or beam misalignment. This technique adds to the toolkit of micro-optics fabrication methods using additive manufacturing and 3D printing, and it would be beneficial for rapid prototyping and integration with miniaturised systems.

Abstract Optical imaging techniques provide low-cost, non-radiative images with high spatiotemporal resolution, making them advantageous for long-term dynamic observation of blood perfusion in stroke research and other brain studies compared to non-optical methods. However, high-resolution imaging in optical microscopy fundamentally requires a tight optical focus, and thus a limited depth of field (DOF). Consequently, large-scale, non-stitched, high-resolution images of curved surfaces, like brains, are difficult to acquire without z-axis scanning. To overcome this limitation, we developed a needle-shaped beam optical coherence tomography angiography (NB-OCTA) system, and for the first time, achieved a volumetric resolution of less than 8 μm in a non-stitched volume space of 6.4 mm × 4 mm × 620 μm in vivo. This system captures the distribution of blood vessels at 3.4-times larger depths than normal OCTA equipped with a Gaussian beam (GB-OCTA). We then employed NB-OCTA to perform long-term observation of cortical blood perfusion after stroke in vivo, and quantitatively analyzed the vessel area density (VAD) and the diameters of representative vessels in different regions over 10 days, revealing different spatiotemporal dynamics in the acute, sub-acute and chronic phase of post-ischemic revascularization. Benefiting from our NB-OCTA, we revealed that the recovery process is not only the result of spontaneous reperfusion, but also the formation of new vessels. This study provides visual and mechanistic insights into strokes and helps to deepen our understanding of the spontaneous response of brain after stroke.

Optical imaging techniques provide low-cost, non-radiative images with high spatiotemporal resolution, making them advantageous for long-term dynamic observation of blood perfusion in stroke research and other brain studies compared to non-optical methods. However, high-resolution imaging in optical microscopy fundamentally requires a tight optical focus, and thus a limited depth of field (DOF). Consequently, large-scale, non-stitched, high-resolution images of curved surfaces, like brains, are difficult to acquire without z-axis scanning. To overcome this limitation, we developed a needle-shaped beam optical coherence tomography angiography (NB-OCTA) system, and for the first time, achieved a volumetric resolution of less than 8 μm in a non-stitched volume space of 6.4 mm × 4 mm × 620 μm in vivo. This system captures the distribution of blood vessels at 3.4-times larger depths than normal OCTA equipped with a Gaussian beam (GB-OCTA). We then employed NB-OCTA to perform long-term observation of cortical blood perfusion after stroke in vivo, and quantitatively analyzed the vessel area density (VAD) and the diameters of representative vessels in different regions over 10 days, revealing different spatiotemporal dynamics in the acute, sub-acute and chronic phase of post-ischemic revascularization. Benefiting from our NB-OCTA, we revealed that the recovery process is not only the result of spontaneous reperfusion, but also the formation of new vessels. This study provides visual and mechanistic insights into strokes and helps to deepen our understanding of the spontaneous response of brain after stroke. [ABSTRACT FROM AUTHOR]

In this paper, liquid-crystal spatial light modulators are presented for precise dynamic manipulation of coherent light fields in space, which are used in diffractive optoelectronic and optical data processing systems. In addition, this paper presents the results of the temporal dynamics study of the HoloEye PLUTO‑2 VIS-016 liquid-crystal spatial light modulator for light field rate modulation analysis. Experiments using binary phase computer-generated holograms and binary focusing phase diffractive optical elements are performed. The time characteristics of the modulator response are determined from the experimental data. Displaying the diffraction structure model on the screen of the spatial light modulator results in a rise time of the diffraction efficiency of 146 ms, and switching to a new model leads to a decay time of 97 ms. The obtained results allow implementing the dynamic generation of an alternating diffraction field at 2 Hz update frequency with −16 dB interference level. Increasing the frequency of updating diffraction structure models increases the level of interframe noise in the generated diffraction field, and when updating with the frequency indicated in the specification, separating the generated distributions is virtually impossible. From the presented results, the studied modulator model can be applied for high-precision formation of complex diffraction fields with a frame update rate lower than stated. Determining the actual frame rate from the rise and decay times of diffraction efficiency allows correctly determining the minimum operating time of an information optical system with a liquid-crystal spatial light modulator. [ABSTRACT FROM AUTHOR]

The traditional multi-line laser calibration method relies primarily on calibrating the spatial plane equations of multiple laser lines and reconstructing the multi-line laser in three dimensions through the plane equation and camera parameters. In traditional methods, the multi-line laser is projected as a straight line by default, but in reality, the laser line projected by the multi-line laser is not a plane due to the Diffractive Optical Element (DOE). Instead, it is a surface with a certain curvature in space. During the production process, the multi-line laser experiences significant distortion because of the DOE projecting at a large angle. Consequently, if traditional methods are used, accurate calibration of the multi-line laser cannot be achieved. To address this issue, this paper introduces a new calibration algorithm for multi-line laser based on a spatial quadric equation. By calibrating the spatial quadric equation of the multi-line laser, the spatial characteristics of the laser can be accurately captured. The algorithm involves projecting a crossed 7-line laser onto a calibration plate and changing the position of the calibration plate while capturing images. This allows for obtaining the spatial three-dimensional coordinates of each laser line in the camera coordinate system. Next, spatial quadric equations are fitted for each laser line based on the three-dimensional coordinates. Finally, 3D reconstruction is performed using the quadratic surface parameters of the multi-line laser and camera parameters. The results from 3D reconstruction demonstrate that, compared to traditional laser calibration methods based on planes, the proposed algorithm achieves higher calibration accuracy. It also improves the number of successful binocular multi-line laser matches and overall accuracy. [ABSTRACT FROM AUTHOR]

An important challenge in industrial laser ablation is laser-induced damage. In this study, reduced damage was achieved through the transition of the laser distribution from a Gaussian beam to a top-hat beam using diffractive optical elements (DOE), which overcome inhomogeneous irradiation. The higher peak fluence of a Gaussian beam far exceeded the ablation threshold and led to severely melted silicon at a higher depth covering the polished texture. The top-hat beam, with uniform irradiation, had a superior ablation characteristic and created a uniform square opening with the shallow melted silicon in the lift-off process. Thus, its effective minor carrier lifetime was 15.35% less at an ablated area fraction of 2% after re-passivation because of the decreased damage. After optimizing the ablation pattern with a top-hat beam, the local contacts improved the average open-circuit voltage (Voc) and short-circuit current (Isc) values of the cells due to the decreased damage and the uniform openings, but the damage induced by a Gaussian beam was too deep and can be partly restored under back surface field (BSF) formation. The overall increment in Isc and Voc enhanced the average efficiency by 0.05% of the absolute value for the PERC cells and 0.03% of the absolute value for bi-facial PERC cells. [ABSTRACT FROM AUTHOR]

Pulsed laser ablation in liquids (PLAL) is a versatile technique to produce high-purity colloidal nanoparticles. Despite considerable recent progress in increasing the productivity of the technique, there is still significant demand for a practical, cost-effective method for upscaling PLAL synthesis. Here we employ and unveil the fundamentals of multi-beam (MB) PLAL. The MB-PLAL upscaling approach can bypass the cavitation bubble, the main limiting factor of PLAL efficiency, by splitting the laser beam into several beams using static diffractive optical elements (DOEs). A multimetallic high-entropy alloy CrFeCoNiMn was used as a model material and the productivity of its nanoparticles in the MB-PLAL setup was investigated and compared with that in the standard single-beam PLAL. We demonstrate that the proposed multi-beam method helps to bypass the cavitation bubble both temporally (lower pulse repetition rates can be used while keeping the optimum processing fluence) and spatially (lower beam scanning speeds are needed) and thus dramatically increases the nanoparticle yield. Time-resolved imaging of the cavitation bubble was performed to correlate the observed production efficiencies with the bubble bypassing. The results suggest that nanoparticle PLAL productivity at the level of g/h can be achieved by the proposed multi-beam strategy using compact kW-class lasers and simple inexpensive scanning systems. [ABSTRACT FROM AUTHOR]

Diffractive optical elements (DOE) are integral components for lightweight and ultra‐thin optical elements due to their ability to manipulate light efficiently and accurately. However, conventional DOEs are static and cannot be altered after fabrication, which hinders their adaptability to changing requirements. To overcome this limitation, the potential of surface patterning on azobenzene thin films to fabricate reconfigurable DOEs is investigated. Using holographic lithography, surface topographies with sinusoidal surface relief gratings (SRG) are created and the superposition of up to 80 SRGs with high accuracy and minimal information loss in subsequent inscriptions is demonstrated. This is enabled by a surface patterning tool combining holographic lithography and digital holographic microscopy. Reconfigurable and adaptive optical elements can improve the efficiency of optical coupling and increase the sensitivity and selectivity of sensors, especially in applications such as near‐eye displays and plasmonic sensors. These results demonstrate the ability to create complex azobenzene‐based DOEs for advanced photonic applications, where the ability to alter optical elements is of high importance. [ABSTRACT FROM AUTHOR]

This article focuses on generation of diffractive optical elements (DOEs) and computer holograms for forming three-dimensional (3D) images. We intend to analyze the possibilities of increasing (1) the speed of generation of DOEs, and (2) the quality of 3D objects created by the DOEs generated. For this, four methods of optical element generation are analyzed, which are based on division of 3D objects into plane layers. We assess the quality of 3D-object image reconstruction and the resource intensity of the methods with respect to synthesis of DOEs. We conduct a computer simulation of reconstruction of images of 3D objects via the generated DOEs. In optical experiments on formation of 3D objects, the DOEs generated are displayed on a liquid crystal spatial light modulator. We experimentally establish that the method of parallel computation of plane layers and the method of nonconvex optimization are optimum for formation of 3D objects vis-à-vis quality of their reconstruction. Taking into account the computational resource intensity of the considered methods, the iterative method of parallel computation of plane layers yielded the optimal DOE generation results in terms of reconstruction quality-to-synthesis speed ratio. The possibility of fast formation of high-quality 3D objects comprising dozens of layers has been demonstrated, which can be used in high-resolution 3D video communication systems. [ABSTRACT FROM AUTHOR]

Spatial-structured longitudinal light beams are optical fields sculpted in three-dimensional (3D) space by diffractive optical elements. These beams have been recently suggested for use in improving several imaging capabilities, such as 3D imaging, enhancing image resolution, engineering the depth of field, and sectioning 3D scenes. All these imaging tasks are performed using coded aperture correlation holography systems. Each system designed for a specific application is characterized by a point spread function of a different spatial-structured longitudinal light beam. This article reviews the topic of applying certain structured light beams for optical imaging. [ABSTRACT FROM AUTHOR]

Background and Objectives: Fractional ablative resurfacing techniques are preferred treatments for facial rejuvenation of aged skin. This study was performed to investigate the cutaneous effects of using a fractional picosecond laser at 1064 nm with a diffractive lens. Methods: The penetration depth according to the location of the handpiece tip was evaluated using an acrylic panel. Laser induced optical breakdown (LIOB) and cutaneous damage were observed after hematoxylin and eosin staining in guinea pigs. Collagen formation was evaluated using Victoria staining, Masson's trichrome (MT) staining, and immunohistochemical staining for collagen type III. Results: The penetration depth for LEVEL 1 was 499.98–935.23 μm (average: 668.75 ± 182.84 μm); the LIOB cavity area was 1664.17 ± 650.52 μm2. The penetration depth of LEVEL 2 was 257.12–287.38 μm (average: 269.77 ± 14.55 μm) with an LIOB cavity area of 1335.85 ± 214.41 μm2. At LEVEL 3, that was 36.17–53.69 μm (average: 52.15 ± 20.81 μm) and the LIOB cavity area was 1312.67 ± 1069.12 μm2. No epidermal tissue damage was observed and collagen formation was observed from day 14 under all conditions. Conclusion: Diffractive optical element (DOE) lens arranged laser treatment system controlled the position of LIOB occurrence and an irradiating area. [ABSTRACT FROM AUTHOR]

3D-printed blocks with drop coating could work as diffraction gratings while the layer stepping serves as the grooves of the gratings. This paper reports 3D-printed diffraction gratings coated with different resins. A collimated laser with a wavelength of 520 nm passed through the gratings and generated diffraction patterns. Optical path differences and surface profiles of the samples were measured to analyze the mechanism of the diffraction phenomenon. The as-printed samples had a grating height of about 8 µm induced by layer stepping, which could not generate clear diffraction patterns because of too large optical path difference. After being coated with different resins on the surfaces, the printed samples generated diffraction patterns. We experimentally showed that the magnitude of optical path differences became close to the wavelength of the laser and that the diffraction phenomenon was mainly caused by the difference in the refractive indices between the as-printed part and the drop-coated part. This novel method enables low-cost 3D printers to fabricate diffractive optical elements for visible light. [ABSTRACT FROM AUTHOR]

Laser processing is a versatile tool that enhances smart materials for diverse industries, allowing precise changes in material properties and customization of surface characteristics. It drives the development of smart materials with adaptive properties through laser modification, utilizing photothermal reactions and functional additives for meticulous control. These laser-processed smart materials form the foundation of 4D printing that enables dynamic shape changes depending on external influences, with significant potential in the aerospace, robotics, health care, electronics, and automotive sectors, thus fostering innovation. Laser processing also advances photonics and optoelectronics, facilitating precise control over optical properties and promoting responsive device development for various applications. The application of computer-generated diffractive optical elements (DOEs) enhances laser precision, allowing for predetermined temperature distribution and showcasing substantial promise in enhancing smart material properties. This comprehensive overview explores the applications of laser technology and nanotechnology involving DOEs, underscoring their transformative potential in the realms of photonics and optoelectronics. The growing potential for further research and practical applications in this field suggests promising prospects in the near future. [ABSTRACT FROM AUTHOR]

Nanoparticles (NPs) generated by pulsed‐laser ablation in liquids (PLAL) have benefited many key applications due to their versatility, enlarged surface area, and high purity. However, scaling up NPs production represents one of the main requisites to commercialize this technology. The established upscaling strategy demands high power and repetition rate laser source with fast scanning systems, which are not widely available and costly. Herein, a cost‐effective alternative is proposed, the addition of static diffractive optical elements to achieve parallel processing through the multi‐beam PLAL (MB‐PLAL). In MB‐PLAL, the optimum repetition rate is reduced to compensate laser energy splitting, hence achieving a higher interpulse distance, reducing pulse shielding, and increasing NPs productivity. MB‐PLAL with 11 beams reached a factor 4 productivity increase for iron–nickel alloy (Fe50Ni50) NPs compared to the single‐beam setup (0.4–1.6 g h−1), and a factor 3 increase for gold (Au) NPs (0.32–0.94 g h−1). The scalability of the proposed MB‐PLAL technique setup is confirmed by Au and Fe50Ni50 NPs productivity experiments using 1, 6, and 11 beams, showing a linear increase in productivity.

It was demonstrated that optical modulation together with simultaneous terahertz (THz) imaging application enables an increase in contrast by an order of magnitude, thereby illustrating the technique as a convenient contactless tool for characterization of graphene deposited on high-resistivity silicon substrates. It was shown that the single- and double-layer graphene can be discriminated and characterized via variation of THz image contrast using a discrete frequency in a continuous wave mode. Modulation depth of 45% has been reached, and the contrast variation from 0.16 up to 0.23 is exposed under laser illumination for the single- and double-layer graphene, respectively. The technique was applied in the development and investigation of graphene-based optical diffractive elements for THz imaging systems. [ABSTRACT FROM AUTHOR]

Interrogation of subcellular biological dynamics occurring in a living cell often requires noninvasive imaging of the fragile cell with high spatiotemporal resolution across all three dimensions. It thereby poses big challenges to modern fluorescence microscopy implementations because the limited photon budget in a live-cell imaging task makes the achievable performance of conventional microscopy approaches compromise between their spatial resolution, volumetric imaging speed, and phototoxicity. Here, we incorporate a two-stage view-channel-depth (VCD) deep-learning reconstruction strategy with a Fourier light-field microscope based on diffractive optical element to realize fast 3D super-resolution reconstructions of intracellular dynamics from single diffraction-limited 2D light-filed measurements. This VCD-enabled Fourier light-filed imaging approach (F-VCD), achieves video-rate (50 volumes per second) 3D imaging of intracellular dynamics at a high spatiotemporal resolution of ~180 nm × 180 nm × 400 nm and strong noise-resistant capability, with which light field images with a signal-to-noise ratio (SNR) down to -1.62 dB could be well reconstructed. With this approach, we successfully demonstrate the 4D imaging of intracellular organelle dynamics, e.g., mitochondria fission and fusion, with ~5000 times of observation. A super-resolution light-field imaging method enables video-rate 3D imaging of intracellular dynamics beyond diffraction limit and with strong noise-resistant capability. [ABSTRACT FROM AUTHOR]

Orbital angular momentum (OAM) encoding is a promising technique to boost data transmission capacity in optical communications. Most recently, azobenzene films have gained attention as a versatile tool for creating and altering OAM-carrying beams. Unique features of azobenzene films make it possible to control molecular alignment through light-induced isomerization about the azo bond. This feature enables the fabrication of diffractive optical devices such as spiral phase plates and holograms by accurately imprinting a phase profile on the incident light. By forming azobenzene sheets into diffractive optical elements, such as spiral phase plates, one can selectively create OAM-carrying beams. Due to the helical wavefront and phase variation shown by these beams, multiple distinct channels can be encoded within a single optical beam. This can significantly increase the data transmission capacity of optical communication systems with this OAM multiplexing technique. Additionally, holographic optical components made from azobenzene films can be used to build and reconstruct intricate wavefronts. It is possible to create OAM-based holograms by imprinting holographic designs on azobenzene films, which makes it simpler to control and shape optical beams for specific communication requirements. In addition, azobenzene-based materials can then be suitable for integration into optical communication devices because of their reconfigurability, compactness, and infrastructure compatibility, which are the main future perspectives for achieving OAM-based technologies for the next generation, among other factors. In this paper, we see the possible use of azobenzene films in the generation and modification of OAM beams for optical communications through light-induced isomerization. In addition, the potential role of azobenzene films in the development of novel OAM-based devices that paves the way for the realization of high-capacity, OAM-enabled optical communication networks are discussed. [ABSTRACT FROM AUTHOR]

Photoanisotropic materials, in particular azodyes and azopolymers, have attracted significant research interest in the last decades. This is due to their applications in polarization holography and 4G optics, enabling polarization-selective diffractive optical elements with unique properties, including circular polarization beam-splitters, polarization-selective bifocal lenses, and many others. Numerous methods have been applied to increase the photoinduced birefringence of these materials, and as a result, to obtain polarization holographic elements with a high diffraction efficiency. Recently, a new approach has emerged that has been extensively studied by many research groups, namely doping azobenzene-containing materials with nanoparticles with various compositions, sizes, and morphologies. The resulting nanocomposites have shown significant enhancement in their photoanisotropic response, including increased photoinduced birefringence, leading to a higher diffraction efficiency and a larger surface relief modulation in the case of polarization holographic recordings. This review aims to cover the most important achievements in this new but fast-growing field of research and to present an extensive comparative analysis of the result, reported by many research groups during the last two decades. Different hypotheses to explain the mechanism of photoanisotropy enhancement in these nanocomposites are also discussed. Finally, we present our vision for the future development of this scientific field and outline its potential applications in advanced photonics technologies. [ABSTRACT FROM AUTHOR]

Concentric circular gratings are diffractive optical elements useful for polarization-independent applications in photonics and plasmonics. They are usually fabricated using a low-throughput and expensive electron beam lithography technique. In this paper, concentric circular gratings with selectable pitch values were successfully manufactured on thin films of azobenzene molecular glass using a novel laser interference lithography technique utilizing Bessel beams generated by a combined lens–axicon configuration. This innovative approach offers enhanced scalability and a simplified manufacturing process on larger surface areas compared to the previously reported techniques. Furthermore, the plasmonic characteristics of these concentric circular gratings were investigated using conventional spectrometric techniques after transferring the nanostructured patterns from azobenzene to transparent gold/epoxy thin films. In addition, the real-time imaging of surface plasmon resonance colors transmitted from the concentric circular gratings was obtained using a 45-megapixel digital camera. The results demonstrated a strong correlation between the real-time photographic technique and the spectroscopy measurements, validating the efficacy and accuracy of this approach for the colorimetric studying of surface plasmon resonance responses in thin film photonics. [ABSTRACT FROM AUTHOR]

Laser structuring of graphite anodes substantially improves the electrochemical performance of lithium-ion batteries by facilitating lithium-ion diffusion through the electrode coatings. However, laser structuring is not yet established in industrial battery production due to limited knowledge of its ablation behavior and a low processing rate. This publication addresses these issues with a combination of experimental and theoretical approaches. In a comprehensive process study with picosecond pulsed laser radiation, the influence of various laser parameters on the obtained structure geometries, i.e., the hole diameters and depths, was examined. Wavelengths of 532 and 355 nm combined with pulse bursts and fluences of approximately 10 J cm−2 eventuated in favorable hole geometries with a high aspect ratio. Compared to singlebeam laser structuring, a nearly tenfold reduction in the processing time was achieved by beam splitting with a diffractive optical element without compromising structure geometries or mechanical electrode integrity. The experimental findings were used to model the scalability of electrode laser structuring, revealing the significant influence of the hole pattern and distance on the potential processing rate. Ultrashort pulsed laser powers in the kilowatt regime were found to be necessary to laser-structure electrodes at industrial processing rates resulting in estimated costs of roughly 1.96 $/kWh. The findings support the industrialization of laser electrode structuring for commercial lithium-ion battery production. [ABSTRACT FROM AUTHOR]

Astrophysical lensing has typically been studied in two regimes: diffractive optics and refractive optics. Previously, it has been assumed that the Fresnel scale, RF , is the relevant physical scale that separates these two regimes. With the recent introduction of Picard–Lefschetz theory to the field of lensing, it has become possible to generalize the refractive description of discrete images to all wave parameters, and, in particular, exactly evaluate the diffraction integral at all frequencies. In this work, we assess the regimes of validity of refractive and diffractive approximations for a simple one-dimensional lens model through comparison with this exact evaluation. We find that, contrary to previous assumptions, the true separation scale between these regimes is given by |$R_F/\sqrt{\kappa }$|⁠ , where κ is the convergence of the lens. Thus, when the lens is strong, refractive optics can hold for arbitrarily small scales. We also argue that intensity variations in diffractive optics are generically small, which has implications for the study of strong diffractive interstellar scintillation. [ABSTRACT FROM AUTHOR]

Nickel-based superalloy (DZ411), which has excellent physical and mechanical properties at high temperature, is widely used in the manufacture of high-temperature components in the aerospace field. Laser processing is an advanced special processing technology that can be used to improve the surface properties of nickel-base superalloys. In this paper, a new laser processing technology was investigated by using the line spot formed by the adjustment of diffractive optical elements. The influence of defocus amount on the line spot ablation of nickel-based superalloy was analyzed. The characteristic sizes, surface morphologies, and elements distribution of line spot ablation were observed. The results show that the groove ablated by the line spot is the longest at the focused position, while the narrowest and deepest groove is produced at the − 0.5 mm defocus position instead of the focused position, which is caused by the plasma shielding effect. And the machining trace of the groove processed at the − 0.5 mm defocus position is the most uniform one and rich in Ni at the center of the groove, making the − 0.5 mm defocus position the most suitable machining position. Under the observation of the electron scanning microscope, the grooves ablated by the line spot in the focus and the nearby areas are relatively flat. As the defocus amount increases, the irregular spherical melts begin to appear in the center of the groove formed by the line spot ablation. Thermal cracks occur on the workpiece surface at the position where the defocus amount is too large. EDS analysis shows that the vicinity of Al, Ti, and Ta elements in the focus increased significantly, and it is easy to form intermetallic compounds with Ni in the matrix. The edge of the line spot is in full contact with the air, resulting in obvious oxidation of the material, and the Al element is significantly increased. According to this data, it is speculated that Al2O3 oxide protective film is formed in this specific area. This work can provide guidance for the process optimization of line spot high efficiency processing of nickel-based superalloys. [ABSTRACT FROM AUTHOR]

Diffractive optical elements (DOEs) fundamentally provide the possibility to simultaneously utilize multiple orders for different imaging functions within a system. However, to take advantage of this property, it is necessary to tailor the assignment of specific wavelengths or wavelength ranges with high diffraction efficiency to specific diffraction orders. To achieve this wavelength-selective assignment to different orders, simple diffractive profile shapes are not suitable; instead, multilayer DOEs are required. In this study, we conducted theoretical, scalar investigations on the diffraction efficiency of triple-layer double-relief DOEs for the purpose of tailored wavelength selectivity. Specific materials such as nanocomposites, layer materials, and high-refractive-index liquids with strong dispersion were included, in addition to inorganic glasses, to enable wide design freedom for wavelength selectivity across multiple orders. To simultaneously account for both positive and negative orders, specific material combinations featuring intersecting or touching dispersion curves were utilized. For various material combinations, we calculated significantly different efficiency profiles for multiple orders by varying the relief depths. Further, we discuss the possibility of fine-tuning the efficiency profiles by using high-index liquids as an intermediate layer between two solid profiles, whose dispersion properties can be varied continuously or at least in small steps. [ABSTRACT FROM AUTHOR]

Quasi-continuous-phase metasurfaces overcome the side effects imposed by high-order diffraction on imaging and can impart optical parameters such as amplitude, phase, polarization, and frequency to incident light at sub-wavelength scales with high efficiency. Structured-light three-dimensional (3D) imaging is a hot topic in the field of 3D imaging because of its advantages of low computation cost, high imaging accuracy, fast imaging speed, and cost-effectiveness. Structured-light 3D imaging requires uniform diffractive optical elements (DOEs), which could be realized by quasi-continuous-phase metasurfaces. In this paper, we design a quasi-continuous-phase metasurface beam splitter through a vector iterative Fourier transform algorithm and utilize this device to realize structured-light 3D imaging of a target object with subsequent target reconstruction. A structured-light 3D imaging system is then experimentally implemented by combining the fabricated quasi-continuous-phase metasurface illuminated by the vertical-cavity surface-emitting laser and a binocular recognition system, which eventually provides a new technological path for the 3D imaging field.