Search Results (259)

With the widespread application of optical technology in numerous fields, the polarization performance of transmissive optical components has become increasingly crucial. The extinction ratio, an important indicator for evaluating their polarization characteristics, holds great significance for its precise detection. Aiming at the measurement of the extinction ratio of a transparent component, this study proposes a measurement method for solving the extinction ratio based on measuring the Mueller matrix of the transparent component. The purpose is to analyze the worst position of the extinction ratio of the transmissive component. The extinction ratio of the sample is obtained according to the phase retardation derived from the Stokes vector of the incident light and the Mueller matrix of the optical component, and a theoretical analysis and simulation of this method are carried out. The simulation results verify the feasibility of the theoretical derivation of this method. To further verify the accuracy of the measurement method, experimental verification is conducted. A standard transparent sample with a phase retardation of 13 nm is selected for actual measurement. The data of independent experiments on the transparent sample under different powers are analyzed, and the extinction ratio of the transparent sample is further obtained. When using this method, the relative error is less than 2%, indicating good accuracy. Full article

Pollinating fig wasps (Agaonidae) engage in an obligate mutualism with Ficus species, which is mediated by host-specific chemical cues. However, the role of visual perception in host recognition remains poorly understood, particularly because of a lack of structural studies of their compound eyes. We investigated the ocular morphology of female Ceratosolen gravelyi (exclusive pollinator of F. semicordata) using scanning/transmission electron microscopy. The oval apposition eyes contain 228–263 ommatidia, which are asymmetrically distributed between the left and right eyes. Each ommatidium comprises a biconvex corneal lens overlying a tetrapartite eucone crystalline cone; proximal cone cells reveal an interlaced labyrinth. Pigment cells encapsulate each ommatidium, and numerous pigment granules and mitochondria are present in both pigment and retinular cells. Nine retinular cells comprise a unit, with eight photoreceptors (R1–R8) forming the rhabdom from the cone base to the basal matrix; a ninth cell replaces R8 in the apical third of the rhabdom. Optical metrics, including F-number (1.1°), acceptance angle (10.0°), and ommatidial sensitivity (0.26 µm²/sr), indicate diurnal activity in bright environments. These adaptations suggest that their eyes are critical for processing visual cues during host interactions, which advances our understanding of multimodal sensory integration in fig–wasp mutualism. Full article

The CASTRIP process is an innovative method for producing flat rolled low-carbon and low-alloy steel at very thin thicknesses. By casting steel close to its final dimensions, enormous savings in time and energy can be realized. In this paper, an ultra-high-strength low-alloy corrosion-resistant steel was produced through the CASTRIP process. Microstructure and properties were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser confocal microscopy (LSCM), electron backscattered diffraction (EBSD), and tensile testing. The results show that the microstructure is mainly composed of polygonal ferrite, bainite ferrite, and acicular ferrite. The bainite ferrite forms parallel lath bundles nucleating at austenite grain boundaries, propagating perpendicularly into the parent grains. The acicular ferrite exhibits a cross-interlocked morphology preferentially nucleating at oxide/sulfide inclusions. Microstructural characterization confirms that the phase transformation of acicular ferrite and bainite ferrite introduces high-density dislocations, identified as the primary strengthening mechanism. Under the CASTRIP process, corrosion-resistant elements such as Cu, P, Sb, and Nb are completely dissolved in the matrix without grain boundary segregation, thereby contributing to solid solution strengthening. Full article

Nanostructures obtained as a by-product of the electrochemical synthesis of ZrO₂ nanotube membranes have scarcely received any attention despite their enormous potential. This is mainly due to their size properties, morphology, and composition. In the present work, these nanostructures are characterized, and their potential application as an additive in PVA-based coatings is analyzed. The characterization was performed by X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction. The results showed that the nanostructures consist of tubular fragments generated during the formation of the ZrO₂ membrane, with a dimension of 626.74 nm in width, a length of 1906.39 nm, and a clear cubic structure. The ZrO₂-PVA coating, which is prepared by using the spin coating technique, presented a uniform and homogenous particle distribution, which was later confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. The optical transparency and thermal resistance were evaluated through UV-Vis spectroscopy and thermogravimetric analysis, showing that the incorporation of ZrO₂ as an additive improved its UV absorption properties and thermal stability during the pyrolysis stage. The results suggest that the ZrO₂ nanostructures enhance the thermal and protective properties of the PVA-based coatings by acting as physical barriers and stabilizers within the polymer matrix. Full article

The influence of multiwall carbon nanotube (MWCNT) reinforcements on electrochemical corrosion investigations at varying NaCl concentrations (0.4 M, 0.6 M, 0.8 M, 1 M) of Mg-Zn-Ce nanocomposites is studied in this work. The Mg-Zn-Ce/MWCNT nanocomposites were developed by using an ultrasonication-assisted hybrid stir–squeeze (UHSS) casting method with different MWCNT concentrations (0, 0.4, 0.8, 1.2 wt.%) in a Mg-Zn-Ce magnesium alloy matrix. The microstructural characterizations shown using X-ray diffraction revealed the presence of secondary phases (MgZn₂, Mg₁₂Ce), T-phase (Mg₇Zn₃RE), α-Mg, and MWCNT peaks. Optical microscopy results showed grain refinement in the case of nanocomposites. Transmission electron microscope studies revealed well-dispersed MWCNT, indicating the good selection of processing parameters. The uniform dispersion of MWCNTs was achieved due to a hybrid stirring mechanism along with transient cavitation, ultrasonic streaming, and squeeze effect. The higher E_corr value of −1.39 V, lower I_corr value (5.81 µA/cm²), and lower corrosion rate of 0.1 mm/Yr (↑77%) were obtained by 0.8% nanocomposite at 0.4 M NaCl concentration, when compared to the monolithic alloy. The Mg(OH)₂ passive film formation on 0.8 wt.% nanocomposite was denser, attributed to the refined grains. At higher NaCl concentration, the one-dimensional morphological advantage of MWCNT helped to act as a barrier for further Mg exposure to excessive Cl⁻ attack, which reduced the formation of MgCl₂. Therefore, the UHSS-casted Mg-Zn-Ce/MWCNT nanocomposites present a good potential as sacrificial anodes for use in a wide range of industrial applications. Full article

Photoelectrochromic devices, which combine light-induced color change with energy-efficient optical modulation, have attracted significant attention for applications such as smart windows, displays, and optical sensors. However, achieving high optical modulation, fast switching speeds, and long-term stability remains a major challenge. In this study, we explore the structural and photoelectrochromic enhancements in tungsten oxide (WO₃) films achieved by doping with molybdenum disulfide quantum dots (MoS₂ QDs) and grapheneoxide–molybdenum disulfide quantum dots (GO–MoS₂ QDs) for advanced photoelectrochromic devices. X-ray diffraction (XRD) analysis revealed that doping with MoS₂ QDs and GO–MoS₂ QDs leads to a reduction in the crystallite size of WO₃, as evidenced by the broadening and decrease in peak intensity. Transmission Electron Microscopy (TEM) confirmed the presence of characteristic lattice fringes with interplanar spacings of 0.36 nm, 0.43 nm, and 0.34 nm, corresponding to the planes of WO₃, MoS₂, and graphene. Energy-Dispersive X-ray Spectroscopy (EDS) mapping indicated a uniform distribution of tungsten, oxygen, molybdenum, and sulfur, suggesting homogeneous doping throughout the WO₃ matrix. Scanning Electron Microscopy (SEM) analysis showed a significant decrease in film thickness from 724.3 nm for pure WO₃ to 578.8 nm for MoS₂ QD-doped WO₃ and 588.7 nm for GO–MoS₂ QD-doped WO₃, attributed to enhanced packing density and structural reorganization. These structural modifications are expected to enhance photoelectrochromic performance by improving charge transport and mechanical stability. Photoelectrochromic performance analysis showed a significant improvement in optical modulation upon incorporating MoS₂ QDs and GO–MoS₂ QDs into the WO₃ matrix, achieving a coloration depth of 56.69% and 70.28% at 630 nm, respectively, within 10 min of 1.5 AM sun illumination, with more than 90% recovery of the initial transmittance within 7 h in dark conditions. Additionally, device stability was improved by the incorporation of GO–MoS₂ QDs into the WO₃ layer. The findings demonstrate that incorporating MoS₂ QDs and GO–MoS₂ QDs effectively modifies the structural properties of WO₃, making it a promising material for high-performance photoelectrochromic applications. Full article

Creep tests of Super304H austenitic steel were carried out at 700 °C under different stresses. The samples were characterized by an optical microscope (OM), scanning electron microscope (SEM) and a transmission electron microscope (TEM). The results show that high-temperature creep promotes the precipitation of the M₂₃C₆, secondary MX carbide, σ phase, Cu-rich phase and Z phase. These fine precipitates improve both the matrix and grain boundary strength. Furthermore, the precipitation sequence of these second phases relates to the stress level during elevated temperature testing. The rapid precipitation of the σ phase is also observed at high stress levels, whereby fast growth at triangle boundaries notably deteriorates grain boundary strength. Conversely, the presence of dispersed fine MX precipitates under low-stress conditions during long-term creep should contribute significantly to microstructure stability and long-term creep strength. Despite the absence of homogeneous cavities observed on the grain boundary when subjected to creep for over 20,000 h, the decrease in grain boundary strength was explained from another aspect by analyzing the change in low angle grain boundary during creep. Full article

Yb_xEr_yZnO thin films with a low concentration (x = 5%, y = 0, 1, 3%) were made on glass substrates using the spray pyrolysis method. The films were characterized through the use of specific techniques to investigate their structural, optical, and electrical properties. The XRD structural analysis of the films revealed that they are polycrystalline with a hexagonal wurtzite structure and a preferential orientation in the (002) direction. The optical characterization of the co-doped layers in the range of 200 to 800 nm revealed that co-doping had a significant impact on the values of transmission. A well-defined peak in the infrared domain centered around 980 nm was observed in photoluminescence measurements. This peak signifies the transition between the electronic levels ²F_5/2 (ground state) and ²F_7/2 (excited state), proving that photons are efficiently transferred between the ZnO matrix and the Yb³⁺ ion. All layers exhibited n-type conduction and an electrical resistivity decrease to 6.0 × 10⁻² Ω cm according to Hall effect measurements at room temperature. Full article

Today, flexible and lightweight electronics are regarded as a viable alternative to conventional rigid and heavy devices in various application fields. In the optoelectronic area, organic semiconductors offer advantages such as high absorption coefficients, low processing temperatures, mechanical flexibility and compatibility with plastic substrates, while inorganic nanostructures provide good electronic properties and high thermal stability. Thus, composite films with enhanced properties can be achieved by inserting inorganic nanostructures within organic layers. In this research work, CuS nanoparticles were prepared by wet chemical precipitation and then added to an organic mixture containing poly(3-hexylthiophene) (P3HT) and N,N-bis-(1-dodecyl)perylene-3,4,9,10 tetracarboxylic diimide (AMC14), a chemically synthesized semiconductor, for fabricating hybrid composite films by matrix assisted pulsed laser evaporation (MAPLE) on indium tin oxide/poly(ethylene terephthalate) (ITO/PET) flexible substrates. A comparative assessment of the morphological, compositional, optical and electrical properties of the composite (P3HT:AMC14:CuS) and organic (P3HT:AMC14) layers was performed to evaluate their applicability in the photovoltaic cells. The transmission and emission spectra of the composite films are dominated by the optical features of AMC14, a perylene diimide derivative compound used as acceptor. In the case of devices based on MAPLE deposited composite layer fabricated on ITO/PET substrates, the electrical measurements carried under illumination revealed an improvement in the open circuit voltage parameter emphasizing their potential applications in the flexible device area. Full article

Due to a lower InN bandgap $\mathrm{e}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y} {\mathrm{E}}_{\mathrm{g}}~0.7 \mathrm{e}\mathrm{V}$, ${\mathrm{I}\mathrm{n}}_{\mathrm{x}}{\mathrm{G}\mathrm{a}}_{1-\mathrm{x}}\mathrm{N}/\mathrm{S}\mathrm{a}\mathrm{p}\mathrm{p}\mathrm{h}\mathrm{i}\mathrm{r}\mathrm{e}$ epifilms are considered valuable in the development of low-dimensional heterostructure-based photonic devices. Adjusting the composition x and thickness d in epitaxially grown films has offered many possibilities of light emission across a wide spectral range, from ultraviolet through visible into near-infrared regions. Optical properties have played important roles in making semiconductor materials useful in electro-optic applications. Despite the efforts to grow ${\mathrm{I}\mathrm{n}}_{\mathrm{x}}{\mathrm{G}\mathrm{a}}_{1-\mathrm{x}}\mathrm{N}$/Sapphire samples, no x- and d-dependent optical studies exist for ultrathin films. Many researchers have used computationally intensive methods to study the electronic band structures ${\mathrm{E}}_{\mathrm{j}}\left(\overrightarrow{\mathrm{k}}\right),$ and subsequently derive optical properties. By including inter-band transitions at critical points from ${\mathrm{E}}_{\mathrm{j}}\left(\overrightarrow{\mathrm{k}}\right)$, we have developed a semiempirical approach to comprehend the optical characteristics of InN, GaN and ${\mathrm{I}\mathrm{n}}_{\mathrm{x}}{\mathrm{G}\mathrm{a}}_{1-\mathrm{x}}\mathrm{N}$. Refractive indices of ${\mathrm{I}\mathrm{n}}_{\mathrm{x}}{\mathrm{G}\mathrm{a}}_{1-\mathrm{x}}\mathrm{N}$ and sapphire substrate are meticulously integrated into a transfer matrix method to simulate d- and x-dependent reflectivity $\mathrm{R}\left(\mathrm{E}\right)$ and transmission $\mathrm{T}\left(\mathrm{E}\right)$ spectra of nanostructured ${\mathrm{I}\mathrm{n}}_{\mathrm{x}}{\mathrm{G}\mathrm{a}}_{1-\mathrm{x}}\mathrm{N}/\mathrm{S}\mathrm{a}\mathrm{p}\mathrm{p}\mathrm{h}\mathrm{i}\mathrm{r}\mathrm{e}$ epifilms. Analyses of $\mathrm{R}\left(\mathrm{E}\right)$ and $\mathrm{T}\left(\mathrm{E}\right)$ have offered accurate x-dependent shifts of energy gaps for ${\mathrm{I}\mathrm{n}}_{\mathrm{x}}{\mathrm{G}\mathrm{a}}_{1-\mathrm{x}}\mathrm{N}$ (x = 0.5, 0.7) in excellent agreement with the experimental data. Full article

The transmittance characteristics and the band structure of photonic heterostructures consisting of four distinct dielectric materials are analyzed using the transfer matrix method. An enhanced band structure of such crystals is discovered. It is shown that the band structure is strongly influenced by the arrangement of unit cells in the periodic building blocks of the crystals. The transmission spectra are evaluated for varying layer thicknesses and incident angles to investigate their impact on wave propagation. The symmetrical results for periodicities, sub-layer thickness, and oblique incident angles indicate robust bandgaps with blue shifting and enhanced transmission. Moreover, the periodicity in different cases, followed by the period, has also shown to have a great impact on the emergence of multiple bandgaps. The photonic bandgap and frequency are associated with the lattice elements of the unit cell, shifting naturally as a fundamental property of the structure, which has been achieved by the alteration of unit cells. Hence, the proposed photonic heterostructures offer significant potential for developing efficient band-stop and band-pass filters, facilitating their use in multi-functional integrated optical circuits within the Terahertz spectrum. Full article

The Talbot effect concerns the periodic self-imaging along an optical axis of a free-space optical field that is periodic in an initial transverse plane. It may be modeled by a shift-invariant linear system, fully characterized by the convolution of its impulse response. Self-imaging at integer and fractional Talbot distances of point sources on a regular grid in free space may then be represented by a transmission matrix that is circulant, symmetric, and persymmetric. The free-space Talbot effect may be mapped to the Talbot effect in a multimode waveguide by imposing the anti-symmetry of the mirror-like sidewalls created by the tight confinement of light within a high-index contrast multimode waveguide. The position of the anti-symmetry axis controls the distribution of discrete lattice points in a unit cell. For different distributions, interesting features such as conditional flexibility in the placement of access ports without altering amplitude and phase relationships, omitting ports without power penalty, closed form uneven splitting ratios, and offset access ports can be derived from the MMI coupler. As a specific example, a simple $2\times 2$ MMI coupler is shown to provide a power-splitting ratio related to the golden ratio $\phi$. The structure is amenable to planar photonic integration on any high-index contrast platform. The predictions of the theory are confirmed by simulation and verified by experimental measurements on a golden ratio MMI coupler fabricated using an SOI process. Full article

Cutting-edge wear is inevitable in the cutting process of the knife. Studying the relationship between the performance of the knife and the cutting-edge wear is conducive to optimizing the design of the knife and increasing its service life. The micro-morphology of the cutting edge during the cutting process was systematically characterized by optical microscopy (OM) and scanning electron microscopy (SEM). The strength of the material matrix was characterized by nanoindentation, and the microstructure of the material was characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The influence of different microstructures and geometry parameters of the cutting edge on edge wear was investigated. The experimental results show that the cutting knife longevity decreases with the increase in the edge angle. When the edge angle is 19°, the durability of knives 1# and 2# is 747.5 mm and 826.8 mm; when the edge angle is 29°, the durability of knives 1# and 2# is 377.8 mm and 486.8 mm. Under the same edge angle, the durability of knife 2# is higher, mainly due to its higher hardness and the presence of more micro-scale M23C6 carbides and nano-scale MC carbides. The edge wear process can be divided into two stages. In the initial wear stage, the edge curling phenomenon occurs, which is the plastic deformation of the edge. In the stable wear stage, plowing and stacking of worn materials are observed, which is the abrasive wear process. Full article

In the simulation of partially coherent light propagation within optical systems utilizing the Wigner function, the constraints imposed by the Fourier transform necessitate that the dimensions of the input and output matrices remain congruent. Consequently, the extent of the image plane is dictated by the dimensions of the light source matrix and the propagation distance. For optical systems of greater complexity, such simulations are highly memory-intensive. This paper innovatively incorporates the displacement theorem of the chirp z-transform and integrates it with the Wigner function. This approach affords enhanced flexibility in the simulation of partially coherent light transmission, enabling the targeted simulation of regions of interest within the frequency domain of the optical system, thereby significantly improving simulation efficiency. The efficacy of this novel method is demonstrated through the simulation of a Wigner transmission algorithm based on the chirp z-transform, applied to an RC (Ritchey–Chrétien) telescope system. The RC telescope, known for its optical design that minimizes aberrations and provides high-quality imaging, serves as a critical foundation for the simulation. The resultant simulations exhibit a high degree of consistency with traditional methods while offering increased flexibility, thus corroborating the validity and effectiveness of the proposed approach. Full article

In the presented work, erbium fiber lasers operating in the pulsed mode with a nonlinear element containing a vanadium oxide saturable absorber are demonstrated. The structure of the saturable absorber is based on a segment of thinned silica fiber coated with a thin-film vanadium oxide by the method of metalorganic chemical vapor deposition. A fiber laser scheme is demonstrated that allows controlling the transmission of the internal cavity of the resonator during laser generation and deposition of a thin film. We have demonstrated a method for obtaining and annealing nanocoatings with laser generation control. We controlled the laser output parameters directly during the synthesis of the saturable absorber material. Vanadium oxides obtained in the work demonstrated the Mott–Paierls phase transition practically at room temperature. In this work, the optical characteristics of the output radiation of a fiber laser with a saturable absorber were measured. At temperatures above 70 °C, the coatings demonstrate a passive Q-switch with a repetition rate of 38 kHz and a pulse duration of 3.8 μs. At temperatures below the phase transition, a short-term mode-locking mode occurs. The transmission jump at a wavelength of about 1350 nm during structural rearrangement was 24%. For comparison, VO₂ nanopowder in a polydimethylsiloxane elastomer matrix was used as a saturable absorber material. The nanopowder modulator made it possible to obtain pulses with a frequency of 27 kHz and a duration of about 7.2 μs. Full article