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Plasmonic metasurfaces, which can be considered as the two-dimensional analog of metal-based metamaterials, have attracted progressively increasing attention in recent years because of the ease of fabrication and unprecedented control over the reflected or transmitted light while featuring relatively low losses even at optical wavelengths. Among all the different design approaches, gap-surface plasmon metasurfaces – a specific branch of plasmonic metasurfaces – which consist of a subwavelength thin dielectric spacer sandwiched between an optically thick metal film and arrays of metal subwavelength elements arranged in a strictly or quasi-periodic fashion, have gained awareness from researchers working at practically any frequency regime as its realization only requires a single lithographic step, yet with the possibility to fully control the amplitude, phase, and polarization of the reflected light. In this paper, we review the fundamentals, recent developments, and opportunities of gap-surface plasmon metasurfaces. Starting with introducing the concept of gap-surface plasmon metasurfaces, we present three typical gap-surface plasmon resonators, introduce generalized Snell’s law, and explain the concept of Pancharatnam-Berry phase. We then overview the main applications of gap-surface plasmon metasurfaces, including beam-steerers, flat lenses, holograms, absorbers, color printing, polarization control, surface wave couplers, and dynamically reconfigurable metasurfaces. The review is ended with a short summary and outlook on possible future developments.

Traditional optical lenses and the corresponding imaging systems, which are based on the optical paths when light propagates inside the bulky media, usually suffer from the bulky size, Abbe-Rayleigh diffraction restricted resolution, and limited responses to different kinds of incident light. Recently, the burgeoning development of metasurfaces comprised of artificial micro- or nano-structures at the subwavelength scale has drawn more and more attentions of the scientific community due to the intriguing abilities such as efficient light-matter interactions and multi-dimensional manipulation of optical waves, which provide profound potentials to realize functional metalens with an ultrahigh numerical aperture (NA) and with super-resolution focal spots on a compact size. Here, the research motivations, the broad outline and the recent advances of planar diffractive metalens are summarized, including the principles of metalens design, the basic components of metalens, and the development of metalens systems. Various approaches to remove the focusing aberrations are presented, which is the essential condition to realize metalens objectives and microscopy. Different types of novel metalenses are revealed, such as label-free sub-resolution metalens, nonlinear metalens, artificial intelligence-aided metalens, multifunctional metalens and reconfigurable metalens. Challenges and future goals are also presented at the end the review.

Highly efficient optical diffraction can be realized with the help of micrometer-thin liquid crystal (LC) layers with a periodic modulation of the director orientation. Electrical tunability is easily accessible due to the strong stimuli-responsiveness in the LC phase. By using well-designed photoalignment patterns at the surfaces, we experimentally stabilize two dimensional periodic LC configurations with switchable hexagonal diffraction patterns. The alignment direction follows a one-dimensional periodic rotation at both substrates, but with a 60° or 120° rotation between both grating vectors. The resulting LC configuration is studied with the help of polarizing optical microscopy images and the diffraction properties are measured as a function of the voltage. The intricate bulk director configuration is revealed with the help of finite element Q-tensor simulations. Twist conflicts induced by the surface anchoring are resolved by introducing regions with an out-of-plane tilt in the bulk. This avoids the need for singular disclinations in the structures and gives rise to voltage induced tuning without hysteretic behavior.

The possibility of optical creation of quasi-periodical film structures in transparent photo-recording media by discrete moving the illumination boundary along the polymerized layer is considered. The dependence of the formed profile of the refractive index on the parameters of the photopolymer medium and the acting radiation is studied. The process of a holographic lens formation by visible light was experimentally implemented in a photopolymerizable composition based on OCM-2 with methanol.

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.

The effect of gallium doping on the structural, optical, and magneto-transport properties of the La 0.7 K 0.3 Mn (1− x ) Ga x O 3 (0 ≤  x  ≤ 0.25) ceramics in several magnetic fields (0T–3T) have been synthesized by Pechini sol–gel method. The Rietveld refinements data revealed that all the samples have a rhombohedral structure with the space group R3 ̅c. The SEM images recorded at different magnification levels reveal uniform grain shapes with flat surfaces. The optical properties indicated that the band gap of La 0.7 K 0.3 Mn (1− x ) Ga x O 3 (0 ≤  x  ≤ 0.25) ceramics was shifted from 3.2 to 3.08 eV with dopant concentration. The magnetic study confirmed that our compounds exhibit a ferromagnetic–paramagnetic transition in the vicinity of the Curie temperature Tc. Moreover, in the electrical part, the resistivity decreased with the Ga content and the metal–insulator transition temperature ( T M-I ) reached room temperature for x  = 0.125 under a magnetic field of 3 T . On the other hand, the magnetoresistance (MR) and temperature coefficient of resistance (TCR) increased with the doping of Ga until a significant maximum (MR = 88%, TCR = 8% K −1 ) around metal–insulator transition T M-I  = 300 K for x  = 0.125 with a magnetic field of 3T.

The roll-to-plate (R2P) hot-embossing process is a newly developed molding technique for the high-throughput, high-efficiency fabrication of large-area microstructured optical elements. However, this technology is limited to flat surfaces, because the thickness of the freeform optical plate varies constantly due to its specific optical design, while the roll stays cylindrical during rolling. Therefore, we developed a new profile-tunable roll with several groups of semiconductor heater/coolers (SHCs) attached around the inside wall of the roll. These SHCs can achieve tunable roll profiles at desirable positions by regulating the current for the semiconductor and then the roll temperature, thereby producing optics with a selected freeform. In this paper, the circumferential bulging profiles and corresponding roll temperature fields were thoroughly investigated under various heater/cooler layouts and roll sizes. A circumferential finite element model of the profile-tunable roll was established using the finite element software MSC.MARC 2020 and then verified on the experimental platform. In addition, the fundamental relationship between the bulging values and temperature distributions of the roll and parameters, such as the outer diameter and inner diameter of the roll, the temperature of the semiconductor heater/cooler, and the single piece influence angle, was eventually established. This paper offers a unique fabrication method for high-volume optical freeform plates at extremely low cost and builds a foundation for further research on the axial deformation and temperature distribution of the developed roll for freeform optics and R2P hot-embossing experiments for freeform optical components.

The widespread use of electron beam technology in optoelectronic instrumentation is constrained by the limited data on the critical values of the parameters of the electron beam (density of thermal effect of the beam, the time of this effect, etc.) on the optical elements of devices of various geometric shapes (flat, rectangular and curvilinear elements, etc.), the excess of which leads to the destruction of their surface layers (the appearance of cracks, chips, cavities, violation of surface flatness, etc.). Currently, the ranges of change for these parameters for flat plates, rectangular bars, cylindrical and spherical elements have been determined. However, the studies mentioned are absent for optical elements in the form of plates of double curvature, widely used in integral and fiber optics, microoptics and other areas of optoelectronic instrumentation. The work is devoted to the development of mathematical models of the thermal effect of an electron beam on optical elements in the form of plates of double curvature, that allow with a relative error of 5... 7 % to determine the critical ranges of changes in its parameters (density of thermal effect, time of its action), the excess of which leads to a deterioration in the physical and mechanical properties of the surface layers in the elements up to their destruction. This allows to prevent possible deterioration of technical and operational characteristics at the stage of manufacturing devices with the usage of electron beam technology.

Perovskite solar cells (PSCs) are introduced to photovoltaic field as a promising alternative to conventional silicon solar cells because of having low fabrication cost, flexible structure and thin thickness, yet with some environmental concerns of having metal cations. In this paper, we discuss the effect of using SiO 2 nanospheres front surface grating as one of the light trapping techniques on the performance of the PSC and how this trapping method enhances the power conversion efficiency without further need of increasing perovskite absorber layer thickness. A 3D finite element method solver is employed to simulate the proposed solar cell structure and to obtain its optical and electrical properties, and then, we optimize both of the size and the periodicity of the nanospheres grating. Results show that maximum efficiency of the proposed model of PSC with frontal surface grating is 26.06 % , with short circuit current density of 31.6 m A / cm 2 , while the efficiency of flat surface PSC is 21.9 % , meaning that the power conversion efficiency is improved by 4.16 % in case of surface grated cell. The maximum value of output power observed in grated surface PSC is 26.058 m W / cm 2 , about 4.158 m W / cm 2 higher than its value for the flat surface one mentioned in the previously published relevant literature.

Achromatic multilevel diffractive lenses (AMDLs) represent a breakthrough in flat optics by overcoming chromatic aberration with practical manufacturability. This review examines their evolution from concepts to state-of-the-art devices (2016-2025), analyzing design methods, fabrication, limitations, and applications. We trace the development from zone plates to free-form AMDLs, highlighting the shift from analytical to computational design. The review explores inverse optimization algorithms like direct binary search and global optimization for achieving broadband achromatic performance. Manufacturing advances are categorized, from lithography for centimeter-scale devices to emerging techniques such as 3D printing and laser direct writing. Theoretical analysis establishes fundamental trade-offs between lens diameter, numerical aperture, bandwidth, and efficiency. We compare AMDLs with achromatic metalenses to outline the advantages and trade-offs of each paradigm. Furthermore, we examine the integration of artificial intelligence in AMDL design, from correction algorithms to end-to-end optimization. This synergy of computational optics, advanced manufacturing, and machine learning enables compact, high-performance optical systems for consumer electronics, scientific instrumentation, and photonic technologies, providing engineers with key insights and future research directions.