Search Results (165)

Three-dimensional (3D) microscopic imaging is indispensable for fundamental scientific research and clinical medical diagnosis. Given that conventional widefield optical microscopy and standard confocal microscopy fail to realize high-magnification, full-color, real-time stereoscopic imaging simultaneously, we herein propose a single-optical-path 3D microscopic framework enabled by liquid crystal polarization gratings (LCPGs). The LCPG integrated at the sample plane performs polarization-dependent beam splitting to generate paired left and right viewing channels. These two disparity-bearing view channels share a unified imaging optical path compatible with commercial upright microscopes, wherein an active liquid crystal cell modulates temporal view switching for sequential camera acquisition. We further construct a white-light microscopic platform supporting integrated reflection and transmission imaging modes. Two customized LCPGs with lattice periods of 72.6 μm and 56.9 μm are fabricated, offering angular view separations of 0.84° and 1.07°, respectively. Both gratings achieve ±1st-order diffraction efficiencies above 97% with polarization crosstalk not exceeding 0.8%. The developed system acquires paired left-right images with valid binocular disparity, which can be reconstructed into intuitive stereoscopic perceptions via a 3D display monitor. This LCPG-based optical architecture upgrades standard upright microscopes to compact dual-view stereoscopic imaging systems, while fully inheriting the native merits of white-light illumination and high-magnification microscopic observation. Full article

Thin sections are fundamental tools in mineralogy, petrography, archaeometry, paleontology, and heritage science, allowing for the microscopic study of mineral assemblages, rock textures, ceramic fabrics, and fossil microstructures. Although thin-section preparation is often presented as a standardized technical procedure, the quality and interpretative reliability of the final section depend strongly on material behavior, laboratory equipment, bonding and thinning procedures, thickness-control criteria, and operator decisions made during preparation. This paper examines thin-section preparation as a process of methodological calibration, understood as the material-specific adjustment of preparation decisions in order to preserve the microstructural features required for subsequent interpretation. The study combines an overview of current preparation practice with documented hands-on workflows from academic and heritage-oriented thin-section laboratories. Two case studies are used to develop the calibration framework. The first concerns silicified fossil wood and marly carbonate samples prepared at the Department of Geology, University of Patras, Greece, using water-cooled cutting, epoxy bonding under heat and pressure, machine-assisted and manual thinning, micrometer-based thickness monitoring, and optical assessment adapted to carbonate-rich samples. The second concerns archaeological ceramics, fossiliferous limestone, oolitic limestone, and coherent lithic/sedimentary samples prepared at the INSTAP Study Center for East Crete, Greece, where preparation decisions included mounting-face selection, cleaning, vacuum impregnation where required, controlled lapping, and transmitted/polarized-light quality assessment. Together, the case studies show that equivalent preparation stages require different operational decisions according to hardness, brittleness, porosity, cohesion, fossil content, ceramic fabric, and intended analytical purpose. Preparation-induced features such as microcracks, smearing, surface relief, detachment, or loss of weak fabrics may be misread as primary geological, technological, taphonomic, or conservation-related features if preparation choices are not properly considered. Framed in this way, thin-section preparation is positioned as a foundational first step in heritage material characterization, on which the reliability of subsequent optical, electron-optical, and microanalytical methods directly depends. Full article

Domain walls (DWs) are ubiquitous topological defects in two-dimensional (2D) ferroelectric materials, yet their static role in optoelectronic transport remains unclear. Here, we address this issue using first-principles quantum-transport calculations on monolayer ferroelectric In₂Se₃ p–i–n junctions. Contrary to the conventional view that defects degrade device performance, only specific static DW configurations—not all—can significantly enhance photocurrent. We examine two thermodynamically stable configurations (the Initial and Final states) and one saddle-point configuration (the Transition state) along the polarization-switching pathway. The Initial state yields a photocurrent density of 10.91 μA·mm⁻², about 1.80 times that of the single-domain device, while the Final state reaches 8.39 μA·mm⁻², corresponding to an increase of ~37%. By comparison, the thermodynamically unstable Transition state gives a lower value of 5.92 μA·mm⁻², indicating strong configuration selectivity. Analysis shows that the observed behavior can be qualitatively rationalized by the combined effects of optical absorption, carrier separation induced by DW-driven electrostatic-potential redistribution, and preserved conduction-channel continuity for carrier extraction. These findings provide a microscopic basis for understanding configuration-selective photocurrent enhancement by static domain walls in short-channel 2D ferroelectric devices. Full article

With the advent of the big data era, traditional storage technologies struggle to meet the demands for long-term, secure, and cost-effective preservation of massive amounts of information. Collinear holographic storage technology has emerged as a strong contender for next-generation optical storage due to its high storage density, rapid parallel transmission, and exceptional reliability. Among various storage materials, phenanthraquinone-doped poly(methyl methacrylate) (PQ/PMMA) photopolymer has garnered significant attention for its negligible photo-induced volume shrinkage, low cost, controllable thickness, and polarization-sensitive holographic response properties. However, the material’s limited photosensitivity, low polarization response, and poor optical uniformity severely constrain its application in high-speed recording and multidimensional multiplexing holographic systems. This paper reviews the primary methods and strategies employed over the past five years to enhance the holographic performance of PQ/PMMA photopolymer materials, based on the microscopic physicochemical mechanisms underlying traditional and polarization holography, including chemical modification, nanoscale doping, mechanical control, etc. Through a systematic review of these research advances, this paper aims to provide theoretical foundations and technical references for developing high-performance PQ/PMMA photopolymer materials suitable for collinear holographic storage. Full article

Multimode fibers with core diameters of 50 μm and 62.5 μm are the core media for short-distance, low-cost, and high-bandwidth optical transmission scenarios. Currently, the detection of their end-face defects is still mainly based on manual microscopic inspection. Most of the existing machine vision detection schemes are aimed at polarization-maintaining fibers (POL), which are easily interfered with by impurities and have insufficient accuracy and efficiency. This study introduces the information entropy in information theory as a constraint for feature selection, proposes the WGMOS digital image detection method, and optimizes the entire process of image acquisition, correction, filtering, adaptive segmentation, and feature extraction. By minimizing the information entropy of background noise and maximizing the information content of defect features, interference is suppressed. Experiments show that compared with the POL detection method, this scheme can exclude more impurities, with the image equalization value increased by ≥38.20% and the signal-to-noise ratio increased by ≥6.0%. It can achieve efficient and accurate detection of multimode fiber end-face defects. Full article

In this work, a comprehensive first-principles investigation of the electronic, magnetic, and optical properties of pristine and Fe-, Co-, and Ni-doped MoS₂ monolayers is presented within the framework of density functional theory. Substitutional transition-metal doping at the Mo site is shown to induce spin-polarized impurity states within the pristine band gap, leading to significant modifications of the electronic structure, including metallic, semimetallic, or half-metallic behavior depending on the dopant species. The calculated spin-resolved band structures and projected density of states reveal a strong hybridization between the dopant $3d$ orbitals and the Mo-$4d$/S-$3p$ states, giving rise to sizable magnetic moments and dopant-dependent exchange splitting. When spin–orbit coupling is included, the combined effect of exchange interactions and relativistic effects leads to an effective valley splitting at the K and $K^{\prime }$ points, whose magnitude and sign depend sensitively on the chemical nature of the dopant. Optical properties are analyzed within a linear-response framework, showing pronounced dopant-induced modifications of the optical spectra. While the pristine monolayer exhibits well-defined excitonic features, transition-metal substitution introduces low-energy optical transitions associated with impurity-related states. Consequently, the exciton binding energies estimated from the difference between the electronic and optical gaps are interpreted as effective measures of dopant-induced perturbations to optical transitions, rather than as quantitative many-body excitonic binding energies in the strict sense. These results provide microscopic insight into the interplay between magnetism, spin–orbit coupling, and optical response in doped MoS₂ monolayers, highlighting the potential of transition-metal substitution as a route to engineer spin- and valley-dependent phenomena in two-dimensional materials. Full article

This study investigates the hydrophobic properties of hexamethyldisiloxane (HMDSO)-based coatings deposited by atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD). The objective of this procedure is to enable the extraction of molded components from the mold cavity. The test specimen geometry employed in the present investigation were made of tool steel 1.2311, a material that is frequently utilized in industrial applications. A series of experiments was conducted to assess the coating performance. Initially, surface energy measurements based on contact angle analysis were performed to determine the polar and dispersive surface components. Finally, energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscope (SEM) images are used to perform an exact measurement of the elemental composition and an optical comparison of the surface. The results of the work indicate that the material composition on the surface of silicon and oxygen is of particular importance. In addition, the results indicate that the use of argon as a carrier gas has a positive effect on reducing surface energy and increasing the contact angle to water drops. Full article

We report a highly sensitive label-free optical biosensor based on nematic liquid crystals, for the detection of proteins. The principles of biosensing are based on the change in the liquid crystal alignment induced by biomolecules adsorbed on the cell inner surface, which can be easily detected with a polarizing optical microscope. Although this approach is well-known, we propose here an experimental strategy that allows us to reach a detection limit of the order of 10⁻¹³ g/mL, orders of magnitude higher than the one reported in the literature for similar biosensors. Furthermore, our method leads to assessing a well-defined, specific dependence of protein concentration on cell birefringence, for rapid quantitative biosensing. The proposed biosensor can additionally be used for the detection of antibodies. Full article

Polymer films and polymer blend films are widely used as functional materials; however, their photophysical behavior cannot be fully explained solely by bulk properties such as relative permittivity or glass transition temperature. In this study, we investigate how local polymer microenvironments regulate fluorescence responses by employing two strongly emissive solvatochromic dyes—FπPCM, a D–π–A-type π-conjugation-extended fluorene dye, and PK, a D–π–A-type pyrene dye—as molecular probes. The photophysical properties of these dyes were systematically examined in a series of transparent polymer matrices, including polystyrene, polycarbonate, poly(methyl methacrylate), poly(vinyl chloride), triacetylcellulose, poly(butyl methacrylate), and poly(2-ethyl-2-oxazoline). Polymer films containing the dyes were prepared by solution casting from homogeneous polymer–dye solutions onto quartz substrates followed by solvent evaporation. Both dyes exhibited polymer-dependent variations in fluorescence wavelength, quantum yield, and lifetime, reflecting not only differences in polymer polarity but also local chain packing and specific dye–polymer interactions. Fluorescence lifetime analysis of PS/POz blend films revealed microscopic heterogeneity even in miscible systems, quantitatively captured using averaged lifetime parameters. Temperature-dependent fluorescence measurements further demonstrated that thermal history and structural relaxation significantly influence local polymer environments. In particular, ratiometric fluorescence analysis of PMMA/PBMA blend films enabled reproducible temperature sensing over a wide range from 30 to 120 °C, despite an overall negative temperature response. These results establish solvatochromic dyes as versatile optical probes for evaluating local polymer microenvironments and highlight their potential for polymer-state monitoring and fluorescence-based temperature-sensing applications. Full article

Parylene C films are subjected to inadequate corrosion resistance due to their relatively low adhesion and structural defects. To address this challenge, the CVD Parylene C film (10 μm thick) was composited with Al₂O₃ film (30 nm thick) prepared with atomic layer deposition (ALD) technology in this work. Optical microscopic results indicate uniform thickness of the films and the reduced adhesion of Parylene C based thick films. SEM-EDX and AFM results show that the composite films have more blurred mounds morphology than the individual films, and Al₂O₃ film decreases the surface roughness of Parylene C film; compared with the single-layer film, the R_a value of the bilayer film decreased by approximately 6%. XPS, FTIR and XRD analyses confirm the structural components of Al₂O₃ and Parylene C films and the annealing effect of ALD process on Parylene C film. Tafel polarization and electrochemical impedance spectroscopy tests reveal that the 304-Parylene C–Al₂O₃ system exhibits the optimal corrosion resistance; its corrosion current density (i_corr) is 8.099 × 10⁻⁵ μA/cm² and the ALD Al₂O₃ thin film uniformly coats the Parylene C film, enhancing its physical barrier and chemical passivation under corrosive conditions. Full article

Topological 3D Dirac semimetals are characterized by bulk Dirac cone band crossings and nontrivial topological surface states, giving rise to a wealth of exotic physical properties and attracting considerable attention in recent years. Understanding the nonequilibrium dynamics of Dirac semimetals in micro-size provides critical guidance for the design of micro- and nanoscale optoelectronic and ultrafast photonic devices. In this work, we employ time-resolved microscopic transient spectroscopy to investigate the nonequilibrium photocarrier and lattice dynamics in microcrystalline Dirac semimetal NiTe₂, a prototypical 3D Dirac semimetal. Following photoexcitation at 390 nm, the transient reflectivity kinetics of NiTe₂ can be well described with a triple-exponential decay function. The fastest relaxation component occurs on a sub-picosecond timescale and increases with pump fluence, which originates from electron-optical phonon coupling. An intermediate relaxation process with a characteristic time of ~8 ps is attributed to electron–hole recombination, while a slower decay component on the order of ~20–30 ps can be assigned to the anharmonic decay of optical phonons into acoustic phonons. Polarization-resolved measurements reveal nearly in-plane isotropic transient responses, which are insensitive to the polarization of probe light. These findings contribute to the physical insights for the development of future photonics and optoelectronic devices based on topological Dirac semimetals. Full article

Microscopes have long been an important tool for paleontology, but most researchers use biological microscopes that are designed for transmitted light illumination. Micropaleontology has traditionally involved investigations of individual organisms (e.g., foraminifera, radiolarian and diatoms), or fossil pollen. Optical microscopy can also be a useful method for the study of macrofossils. Polarized light illumination, long a mainstay of geological research, has largely been missing from paleontology investigations. However, adapting a standard microscope for polarized light is not a difficult task. The preparation of mineralized fossils as petrographic thin sections greatly expands the possibilities for microscopic examination of macrofossils. Scanning electron microscopy (SEM) has long been used for the study of fossils, most commonly for observing individual microfossils or anatomical features of larger organisms. X-ray fluorescence analysis (SEM/EDS), a standard method for geology research, has had minimal use by paleontologists, but it is a method that merits wider acceptance. This paper emphasizes inexpensive methods for researchers who want to expand their microscopy horizons without needing deep funding or access to specialized facilities. Full article

Three painted valuable wood sculptures from conventual collections in Apulia (Southern Italy), made between the beginning of the 17th century and the first half of the 18th century, were studied to shed light on the pictorial materials and techniques of the Neapolitan Baroque sculpture in Southern Italy. A multi-analytical approach was implemented using integrated micro-invasive techniques, including polarized light microscopy (PLM) in ultraviolet (UV) and visible (VIS) light, scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), Fourier-Transform Infrared (FTIR) spectroscopy, and pyrolysis–gas chromatography/high-resolution mass spectrometry (Py-GC/HRMS). The stratigraphic sequences were microscopically identified, and the pictorial layers were discriminated on the basis of optical features, elemental compositions, and mapping. Organic components were detected by FTIR as lipids and proteinaceous compounds for binders, while terpenic resins were detected as varnishes. Accordingly, PY-GC/HRMS identified siccative oils, animal glue, egg, and colophony. The results allowed the identification of the painting techniques used for the pictorial films and the ground preparation layers and supported the distinction between original and repainting layers. The results of this multi-analytical approach provide insights into Baroque wooden sculpture in Southern Italy and offers information to support restorers in conservation works. Full article

This work presents the development of a Z-depth system for Confocal Raman Spectroscopy (CRS), which allows for the acquisition of Raman spectra both at the surface and at depth profile in heterogeneous samples. The proposed CRS system consists of the coupling of a commercial 785 nm Raman Probe Bifurcated (RPB) with a 20x/0.40 infinity plan achromatic polarizing microscope objective, a Long Working Distance (LWD) of 1.2 cm, and a 50 μm core-multimode optical fiber used as a pinhole filter. With this implementation, it is possible to achieve both a high spatial resolution of approximately 16.2 μm and a spectral resolution of ∼14 cm⁻¹, which is determined by the FWHM of the thin 1004 cm⁻¹ Raman profile band. The system is configured to operate within 400–1800 cm⁻¹ spectral windows. The implementation of a system of this nature offers a favorable cost–benefit ratio, as commercial CRS is typically found in high-cost environments such as cosmetics, pharmaceutical, and biological laboratories. The proposed system is low-cost and employs a minimal set of optical components to achieve functionality comparable to that of a confocal Raman microscope. High signal-to-noise ratio (SNR) Raman spectra (∼660.05 at 1447 cm⁻¹) can be obtained with short integration times (∼25 s) and low laser power (30–35 mW) when analyzing biological samples such as in vivo human fingernails and fingertips. This power level is significantly lower than the exposure limits established by the American National Standards Institute (ANSI) for human laser experiments. Raman spectra were recorded from the surface of both the nails and fingertips of three volunteers, in order to characterize their biological samples at different depths. The measurements were performed in 50 μm steps to obtain molecular structural information from both surface and subsurface tissue layers. The proposed CRS enables the identification of differences between two closely spaced, centered, and narrow Raman bands. Additionally, broad Raman bands observed at the skin surface can be deconvolved into at least three sub-bands, which can be quantitatively characterized in terms of intensity, peak position, and bandwidth, as the confocal plane advances in depth. Moreover, the CRS system enables the detection of subtle, low-intensity features that appear at the surface but disappear beyond specific depth layers. Full article

In recent years, structured light with novel propagation properties has attracted great attention. Among these structured beams, the Airy beam is one of the most representative and widely used beams. In this paper, we propose a kind of quadruple Gaussian Airy beam (QGAB) with fourfold symmetry. The QGAB is designed by the combination of Gaussian and Airy functions, and the polarization of the QGAB can be either singular or space-variant. We experimentally generate the QGABs and further study the propagation characteristics of the QGABs with different polarization states. The QGAB enriches the family of the structured beams, and the autofocusing and self-healing properties can be applied in regions such as optical communications, optical microscopes, and optical tweezers. Full article