The combination of polarization and phase singularities in structured light fields can lead to various transformations in their structure. This enables the control of different characteristics of such structured light. In this paper, we numerically investigate the possibility of controlling the distribution of spin angular momentum (SAM) density in optical vortex (OV) beams with partially transformed cylindrical polarization. We examine the effects of the degree of transformation of cylindrical polarization and the topological charge of the OV beam on SAM distributions in both the focal and out-of-focal planes. Experimental studies conducted using a polarization video camera confirmed the polarization transformations. The results obtained enhance the understanding of the phase-polarization transformations that occur during the propagation and focusing of structured light, which can be beneficial in the fields of laser manipulation and the laser processing of photosensitive materials.

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.

A high-efficiency method for the light curves formation using sector generalized spiral phase plates is proposed. It is possible to change not only the phase gradient value but also its direction in different sections of the curve. This provides the ability to control the orbital angular momentum and the transverse energy flow density of the formed beam.

The paper presents a novel approach for a three-dimensional relief formation on Iceland spar plates using laser-induced microplasma generated from a pyrographite target via laser ablation to fabricate phase-polarization optical elements with tailored phase and polarization characteristics. Iceland spar, known for its unique optical properties, including birefringence and optical clarity, presents significant challenges in precision microfabrication due to its anisotropic structure. The study focuses on optimizing laser parameters for the erosive plasma torch formation and the subsequent etching of Iceland spar, guided by preliminary experimental investigations and energy calculations. Key factor such as the overlap coefficients in the focal spot is explored for impact on the reproducibility of etching depths and the accuracy of depth deviations, with an emphasis on precision in microfabrication. Experimental results show that the deviation accuracy of etching depths no more than 0.1 μm achieved with the optimal overlap coefficients of 0.5. Additionally, the fabrication and testing of the 4-sector phase plate on Iceland spar designed for the wavelength of 0.53 µm with etched areas providing the phase shift of π with the deviation of 0.06π (determined by the achieved etching depth deviation accuracy) are presented. The results demonstrate the potential of laser-induced microplasma as an effective tool for fabrication phase-polarization optical elements on birefringent substrates.

Diffractive optical elements (DOEs) are engineered to manipulate light through diffraction, leveraging their micro- or nano-structured surfaces to generate specific spectral characteristics. These elements can be designed to operate over a wide range of wavelengths, enabling precise control of light’s phase, amplitude, and polarization. The versatility of DOEs allows for the creation of cascaded DOEs, where multiple elements are combined to enhance functionality, such as in beam shaping or splitting applications. In 3D diffractive optics, DOEs are employed to create 3D light fields, which are essential in holography and advanced display technologies. Structural coloration, another application, employs DOEs to produce vivid colors without pigments by diffracting light into its constituent wavelengths. In image processing, DOEs can improve image quality by correcting aberrations and enhancing resolution through customized diffraction patterns. Overall, the spectral control provided by DOEs is pivotal in advancing various optical technologies and applications. In this comprehensive review, the spectral characteristics of DOEs are discussed along with their utilization in several interesting applications.

Structural health monitoring (SHM) plays a vital role in ensuring the safety, durability, and performance of civil infrastructure. This review delves into the significant advancements in optical fiber sensor (OFS) technologies such as Fiber Bragg Gratings, Distributed Temperature Sensing, and Brillouin-based systems, which have emerged as powerful tools for enhancing SHM capabilities. Offering high sensitivity, resistance to electromagnetic interference, and real-time distributed monitoring, these sensors present a superior alternative to conventional methods. This paper also explores the integration of OFSs with Artificial Intelligence (AI), which enables automated damage detection, intelligent data analysis, and predictive maintenance. Through case studies across key infrastructure domains, including bridges, tunnels, high-rise buildings, pipelines, and offshore structures, the review demonstrates the adaptability and scalability of these sensor systems. Moreover, the role of SHM is examined within the broader context of civil and urban infrastructure, where IoT connectivity, AI-driven analytics, and big data platforms converge to create intelligent and responsive infrastructure. While challenges remain, such as installation complexity, calibration issues, and cost, ongoing innovation in hybrid sensor networks, low-power systems, and edge computing points to a promising future. This paper offers a comprehensive amalgamation of current progress and future directions, outlining a strategic path for next-generation SHM in resilient urban environments.

Wearable sensors have appeared as a promising solution for real-time, non-invasive monitoring in diverse fields, including healthcare, environmental sensing, and wearable electronics. Surface-enhanced Raman spectroscopy (SERS)-based sensors leverage the unique properties of SERS, such as plasmonic signal enhancement, high molecular specificity, and the potential for single-molecule detection, to detect and identify a wide range of analytes with ultra-high sensitivity and molecular selectivity. However, it is important to note that wearable sensors utilize various sensing mechanisms, and not all rely on SERS technology, as their design depends on the specific application. This comprehensive review highlights the recent trends and advancements in wearable plasmonic sensing technologies, focusing on their design, fabrication, and integration into practical wearable devices. Key innovations in material selection, such as the use of nanomaterials and flexible substrates, have significantly enhanced sensor performance and wearability. Moreover, we discuss challenges such as miniaturization, power consumption, and long-term stability, along with potential solutions to address these issues. Finally, the outlook for wearable plasmonic sensing technologies is presented, emphasizing the need for interdisciplinary research to drive the next generation of smart wearables capable of real-time health diagnostics, environmental monitoring, and beyond.

We present a novel meta-optical element called a screw metaxicon (a particular type of diffractive spiral axicons with subwavelength grating periods) that transforms linearly polarized beams into second-order cylindrical vector beams, focusing them into a compact light spot. The screw metaxicon element combines a diffractive axicon structure with subwavelength gratings screwed/curved in different annular zones. At the same time, the screw metaxicon is unique in that it has rotational symmetry. We show that by changing the screw angle of subwavelength gratings in annular zones, we can vary the magnitude of a reverse energy flux in the generated focal spot. To implement numerical modelling of the screw metaxicon performance with different screw angles we use the Comsol Multiphysics software. A screw angle providing the maximal reverse energy flux at the focal spot is revealed.

A multi-order combined diffraction spatial filter, integrated with a set of Zernike phase functions (representing wavefront aberrations) and Zernike polynomials, enables the simultaneous formation of multiple aberration-transformed point spread function (PSF) patterns in a single plane. This is achieved using an optical Fourier correlator and provides significantly more information than a single PSF captured in focal or defocused planes—all without requiring mechanical movement. To analyze the resulting complex intensity patterns, which include 49 diffraction orders, a convolutional neural network based on the Xception architecture is employed. This model effectively identifies wavefront aberrations up to the fourth Zernike order. After 80 training epochs, the model achieved a mean absolute error (MAE) of no more than 0.0028. Additionally, a five-fold cross-validation confirmed the robustness and reliability of the approach. For the experimental validation of the proposed multi-order filter, a liquid crystal spatial light modulator was used. Optical experiments were conducted using a Fourier correlator setup, where aberration fields were generated via a digital micromirror device. The experimental results closely matched the simulation data, confirming the effectiveness of the method. New advanced aberrometers and multichannel diffractive optics technologies can be used in industry for the quality control of optical elements, assessing optical system alignment errors, and the early-stage detection of eye diseases.

Taking into account phase-polarization interactions is crucial for the formation of spatially structured laser beams. The effects that arise in this context can lead to the modulation of individual field components and the transformation of the overall light field. In this study, we investigate the impact of phase and polarization distributions with radial dependencies in polar coordinates on the longitudinal component of laser beams passing through a transmissive spatial light modulator (SLM) based on twisted nematic liquid crystals. Although the amplitude, phase, and polarization distribution of the transformed light field behind the SLM do not depend on the azimuthal angle, the structure of the longitudinal component of the field exhibits a spiral shape. By utilizing the shaped light fields and a projection lithography technique, we demonstrate the feasibility of fabricating spiral microaxicons in thin films of polarization-sensitive materials. We also show that the direction of the spiral twist and the period of the microaxicon can be controlled by manipulating the parameters of the masks displayed on the SLM. Furthermore, we demonstrate the potential for the parallel fabrication of arrays of such microelements. The results obtained show that precise laser processing of photosensitive materials requires taking into account possible phase-polarization interactions of the illuminating laser radiation. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

The increasing demand for high-speed, energy-efficient computing has propelled the development of integrated photonic logic gates, which utilize the speed of light to surpass the limitations of traditional electronic circuits. These gates enable ultrafast, parallel data processing with minimal power consumption, making them ideal for next-generation computing, telecommunications, and quantum applications. Recent advancements in nanofabrication, nonlinear optics, and phase-change materials have facilitated the seamless integration of all-optical logic gates onto compact photonic chips, significantly enhancing performance and scalability. This paper explores the latest breakthroughs in photonic logic gate design, key material innovations, and their transformative applications. While challenges such as fabrication precision and electronic–photonic integration remain, integrated photonic logic gates hold immense promise for revolutionizing optical computing, artificial intelligence, and secure communication.

Here, upon systematic studies of femtosecond-laser processing of monocrystalline Si in oxidation-preventing methanol, we showed that the electromagnetic processes dominating at initial steps of the progressive morphology evolution define the onset of the hydrodynamic processes and resulting morphology upon subsequent multi-pulse exposure. In particular, under promoted exposure quasi-regular subwavelength laser-induced periodic surface structures (LIPSSs) were justified to evolve through the template-assisted development of the Rayleigh-Plateau hydrodynamic instability in the molten ridges forming quasi-regular surface patterns with a supra-wavelength periodicity and preferential alignment along polarization direction of the incident light. Subsequent exposure promotes fusion-assisted morphology rearrangement resulting in a spiky surface with a random orientation, yet constant inter-structure distance correlated with initial LIPSS periodicity. Along with the insight onto the physical picture driving the morphology evolution and supra-wavelength nanostructure formation, our experiments also demonstrated that the resulting quasi-regular and random spiky morphology can be tailored by the intensity/polarization distribution of the incident laser beam allowing on-demand surface nanotexturing with diverse hierarchical surface morphologies exhibiting reduced reflectivity in the visible and shortwave IR spectral ranges. Finally, we highlighted the practical attractiveness of the suggested approach for improving near-IR photoresponse and expanding operation spectral range of vertical p-n junction Si photo-detector operating under room temperature and zero-bias conditions via single-step annealing-free laser nanopatterning of its surface.

We consider the inverse diffraction problem for a generalized spiral phase plate. For a given luminous curve in the focal plane, the transmission function of the plate forming this curve is calculated. It is assumed that the curve is specified analytically in polar coordinates in the form of an explicit dependence of the radius on the angle. We give the conditions imposed on the curve under which the problem certainly has a solution. Also there are examples of solving the direct problem when curves that do not satisfy these conditions are formed.

Metalenses (MLs), representing a groundbreaking paradigm shift within the realm of optics, have ushered in a transformative era in the ability to manipulate and harness the power of light. Diverging from the conventional approach reliant on curved surfaces to bend light, MLs harness intricate arrays of minuscule nanostructures to exert precise control over the phase and amplitude of incident light waves. This revolutionary technology bestows a plethora of advantages, including the creation of ultra-compact optical systems, the enhancement of focusing capabilities to unprecedented levels, and the capability to rectify optical aberrations in a significantly thinner and more lightweight form factor. MLs have discovered a multitude of applications spanning diverse fields, from imaging and photography to augmenting reality and refining medical devices. They stand as a beacon of hope for reshaping the landscape of optical systems, courtesy of their remarkable adaptability and exceptional performance. As the evolution of MLs forges ahead, they hold immense potential to transcend the boundaries of what can be accomplished in the domain of light-based technologies. This review presents the recent advances in reconfigurable MLs and their applicability to imaging systems. Metalenses signify a groundbreaking shift in optics, departing from traditional curved surfaces for light manipulation. Ongoing advancements in reconfigurable metalenses hold significant potential to expand the horizons of light-based technologies, as emphasized in this up-to-date review that delves into recent developments in their application to imaging systems.image

It is demonstrated how structured laser beams can be used to implement holographic optical tweezers for trapping and manipulating light-absorbing nano- and microparticles in the air. Two types of structured laser beams are investigated: polygon laser beams and superpositions of the Laguerre–Gauss modes with various carrier frequencies shifted relative to the propagation axis. The polygon laser beams generate arrays of optical bottle-beam traps, and the superpositions of the Laguerre–Gauss modes generate multiple light spots propagating along curved trajectories. The experiments have shown a possibility of optically trapping hundreds and thousands of airborne carbon nanoparticle agglomerations in a cuvette and passively guiding the trapped particles along a curved trajectory. The reported results can be used to develop laser manipulation systems for studying and transporting airborne nano- and microparticles.

We study the transformation of the analyzed object by a variety of spatial filters including bandpass, differential, radial filters, various types of vortex filters, and Hilbert filters. Advantages and disadvantages of different filters in terms of clarity and direction-invariance of edge extraction, as well as the energy efficiency are numerically demonstrated. Based on the results obtained, multi-order optical spatial vortex filters with different parameters are developed for simultaneously extracting contours of various object parts. We show that a multi-order filter makes it possible to form a set of images in one plane with a clearly defined contour, object corners and various parts of the contour. Numerical and experimental testing of 4- and 5-channel spatial vortex filters of various types was applied for test objects. A possibility of using the proposed filters to simultaneously highlight the edges of the entire image and various parts of the image in order to extract more features from the analyzed image is shown.

Lithography serves as a fundamental process in the realms of microfabrication and nanotechnology, facilitating the transfer of intricate patterns onto a substrate, typically in the form of a wafer or a flat surface. Grayscale lithography (GSL) is highly valued in precision manufacturing and research endeavors because of its unique capacity to create intricate and customizable patterns with varying depths and intensities. Unlike traditional binary lithography, which produces discrete on/off features, GSL offers a spectrum of exposure levels. This enables the production of complex microstructures, diffractive optical elements, 3D micro-optics, and other nanoscale designs with smooth gradients and intricate surface profiles. GSL plays a crucial role in sectors such as microelectronics, micro-optics, MEMS/NEMS manufacturing, and photonics, where precise control over feature depth, shape, and intensity is critical for achieving advanced functionality. Its versatility and capacity to generate tailored structures make GSL an indispensable tool in various cutting-edge applications. This review will delve into several lithographic techniques, with a particular emphasis on masked and maskless GSL methods. As these technologies continue to evolve, the future of 3D micro- and nanostructure manufacturing will undoubtedly assume even greater significance in various applications.

In traditional neural network designs, a multilayer perceptron (MLP) is typically employed as a classification block following the feature extraction stage. However, the Kolmogorov–Arnold Network (KAN) presents a promising alternative to MLP, offering the potential to enhance prediction accuracy. In this paper, we studied KAN-based networks for pixel-wise classification of hyperspectral images. Initially, we compared baseline MLP and KAN networks with varying numbers of neurons in their hidden layers. Subsequently, we replaced the linear, convolutional, and attention layers of traditional neural networks with their KAN-based counterparts. Specifically, six cutting-edge neural networks were modified, including 1D (1DCNN), 2D (2DCNN), and 3D convolutional networks (two different 3DCNNs, NM3DCNN), as well as transformer (SSFTT). Experiments conducted using seven publicly available hyperspectral datasets demonstrated a substantial improvement in classification accuracy across all the networks. The best classification quality was achieved using a KAN-based transformer architecture.