Optical Structure Research Articles

A Novel Investigation on Propagation of Envelop Optical Soliton Structure Through a Dispersive Medium in the Nonlinear Whitham–Broer–Kaup Dynamical Equation

A Novel Investigation on Propagation of Envelop Optical Soliton Structure Through a Dispersive Medium in the Nonlinear Whitham–Broer–Kaup Dynamical Equation

An ultrawide field-of-view pinhole compound eye using hemispherical nanowire array for robot vision.

Garnering inspiration from biological compound eyes, artificial vision systems boasting a vivid range of diverse visual functional traits have come to the fore recently. However, most of these artificial systems rely on transformable electronics, which suffer from the complexity and constrained geometry of global deformation, as well as potential mismatches between optical and detector units. Here, we present a unique pinhole compound eye that combines a three-dimensionally printed honeycomb optical structure with a hemispherical, all-solid-state, high-density perovskite nanowire photodetector array. The lens-free pinhole structure can be designed and fabricated with an arbitrary layout to match the underlying image sensor. Optical simulations and imaging results matched well with each other and substantiated the key characteristics and capabilities of our system, which include an ultrawide field of view, accurate target positioning, and motion tracking function. We further demonstrate the potential of our unique compound eye for advanced robotic vision by successfully completing a moving target tracking mission.

Fluorescent small molecule donors.

Small molecule donors (SMDs) play subtle roles in the signaling mechanism and disease treatments. While many excellent SMDs have been developed, dosage control, targeted delivery, spatiotemporal feedback, as well as the efficiency evaluation of small molecules are still key challenges. Accordingly, fluorescent small molecule donors (FSMDs) have emerged to meet these challenges. FSMDs enable controllable release and non-invasive real-time monitoring, providing significant advantages for drug development and clinical diagnosis. Integration of FSMDs with chemotherapeutic, photodynamic or photothermal properties can take full advantage of each mode to enhance therapeutic efficacy. Given the remarkable properties and the thriving development of FSMDs, we believe a review is needed to summarize the design, triggering strategies and tracking mechanisms of FSMDs. With this review, we compiled FSMDs for most small molecules (nitric oxide, carbon monoxide, hydrogen sulfide, sulfur dioxide, reactive oxygen species and formaldehyde), and discuss recent progress concerning their molecular design, structural classification, mechanisms of generation, triggered release, structure-activity relationships, and the fluorescence response mechanism. Firstly, from the large number of fluorescent small molecular donors available, we have organized the common structures for producing different types of small molecules, providing a general strategy for the development of FSMDs. Secondly, we have classified FSMDs in terms of the respective donor types and fluorophore structures. Thirdly, we discuss the mechanisms and factors associated with the controlled release of small molecules and the regulation of the fluorescence responses, from which universal guidelines for optical properties and structure rearrangement were established, mainly involving light-controlled, enzyme-activated, reactive oxygen species-triggered, biothiol-triggered, single-electron reduction, click chemistry, and other triggering mechanisms. Fourthly, representative applications of FSMDs for trackable release, and evaluation monitoring, as well as for visible in vivo treatment are outlined, to illustrate the potential of FSMDs in drug screening and precision medicine. Finally, we discuss the opportunities and remaining challenges for the development of FSMDs for practical and clinical applications, which we anticipate will stimulate the attention of researchers in the diverse fields of chemistry, pharmacology, chemical biology and clinical chemistry. With this review, we hope to impart new understanding thereby enabling the rapid development of the next generation of FSMDs.

High-sensitivity vector magnetic field sensor based on a V-shaped multimode-no-core-multimode fiber structure.

This work proposes and investigates a bent multimode-no-core-multimode optical fiber structure for vector magnetic field sensing applications. The bent no-core fiber (NCF) serves as the sensing area, and the gold film is deposited on its surface to excite the surface plasmon resonance effect. Due to the strong evanescent field of the unclad and bent NCF, the as-fabricated sensor exhibits a high sensitivity of 5630 nm/RIU in the refractive index range of 1.36-1.39. Magnetic fluid is employed as the magneto-sensitive material for magnetic field sensing, exhibiting a high magnetic field intensity sensitivity of 5.74 nm/mT and a high magnetic field direction sensitivity of 0.22 nm/°. The proposed sensor features a simple structure, low cost, point sensing, and excellent mechanical performance.

Photovoltaic spatial gap solitons in biased photorefractive optical lattices

We investigate the existence and characteristics of spatially confined optical gap solitons within an optical lattice embedded in a biased bulk photovoltaic photorefractive crystal. The Floquet-Bloch theory is used to analyze the uniform lattice and derive the optical lattice band structure. In the photonic band gaps, which are typically opaque to light transmission, the photorefractive nonlinearity permits the formation of solitons. The paraxial Helmholtz equation is set up and solved thereby discovering single hump and double hump soliton states in both band gaps. Interestingly, we have not found any multi peak solitons to exist in this particular case. We examine the characteristics of these gap solitons, finding that the soliton width (an indicator of nonlinearity) and intensity depend on their location within the band gap. We find that the magnitude of the external electric field profoundly affects the gap soliton characteristics. Additionally, the Vakhitov-Kolokolov (VK) criterion, perturbation analysis and numerical techniques are used to analyze the stability of the various types of the spatial gap solitons in both the band gaps.

Comparative study on effect of pomegranate peel powder as natural preservative and chemical preservatives on quality and shelf life of muffins

This research aims to investigate the potential of utilizing pomegranate peel powder (PPP) as a natural preservative in muffin preparation. Pomegranate peel is a rich source of bioactive compounds, including phenolics, flavonoids, and tannins, which possess high antioxidant and antimicrobial properties. The In-Vitro antifungal activity of pomegranate peel powder (8% PPP), potassium sorbate (0.1% PS) and calcium propionate (0.5% CP) was assessed against Penicillium sp. and Aspergillus sp. using poison food technique. The PPP showed the anti-fungal activity by delaying the growth of microorganism on media plate similar to the PS and CP. The effect of utilization of PPP on quality characteristics of muffins were compared with the muffins with chemical preservatives (0.1% PS and 0.5% CP). The viscosity and specific gravity of batter significantly increased from 7.98 to 11.87 Pa s and 1.089–1.398 respectively on addition of 8% PPP. The optical microscopic structure of PPP added batter revealed the decrease in the number of air cells from 24 to 12 with radius range of 6.42–72.72 μm and area range of 511.03–15,383.17 µm2. The functional properties of flour with PPP had higher water absorption capacity, foaming stability, emulsification activity and emulsion stability than others. The addition of PPP significantly increase the weight (32.83 g), and decrease the height (31.3 mm), volume (61.43 cm3), specific volume (1.67 cm3/g) and baking loss (10.19%). The 418.36% increase in fibre content, 14.46% and 18.46% decrease in carbohydrates and energy value was observed in muffin with 8% PPP as compared to control respectively. The total phenols was increased from 0.92 to 12.5 mg GAE/100 g, total tannin from 0.2 to 8.27 mg GAE/100 g, In-vitro antioxidant activity by DPPH from 6.97 to 29.34% and In-vitro antioxidant activity by FRAP from 0.497 to 2.934 mg AAE/100 g in muffins added with 8% PPP. The muffin with PPP was softer than control and muffin with 0.1% PS. The addition of PPP resulted to improve in muffin texture but taste slightly bitter. During the storage of muffins at room temperature (27–30 °C), the moisture content of muffin with PPP was reduced from 17.04 to 13.23% which was higher than the rest of the treatments. Similarly, the hardness of sample with PPP was higher than the sample with 0.5% CP, but lowers than control and sample with 0.1% PS throughout the storage period. The results suggest that pomegranate peel powder can be successfully used as a natural preservative in place of chemical preservatives in muffins, to extend the shelf life. This study provides the opportunity to use PPP as functional ingredient and natural preservative in different bakery products.

Effects of Vanadium Doping on the Optical Response and Electronic Structure of WS2 Monolayers

Abstract2D dilute magnetic semiconductors have been recently reported in transition metal dichalcogenides doped with spin‐polarized transition metal atoms, for example vanadium‐doped WS2 monolayers, which exhibit room‐temperature ferromagnetic ordering. However, a broadband characterization of the electronic band structure of these doped WS2 monolayers and its dependence on vanadium concentration is still lacking. Therefore, power‐dependent photoluminescence, resonant four‐wave mixing, and differential reflectance spectroscopies are performed here to study optical transitions close to the A exciton energy of vanadium‐doped WS2 monolayers at three different doping levels. Instead of a single A exciton peak, vanadium‐doped samples exhibit two photoluminescence peaks associated with transitions from a donor‐like level and the conduction band minima. Moreover, resonant Raman and second‐harmonic generation experiments reveal a blueshift in the B exciton energy but no energy change in the C exciton after vanadium doping. Density functional theory calculations show that the band structure is sensitive to the Hubbard U correction for vanadium, and several scenarios are proposed to explain the two photoluminescence peaks around the A exciton energy region. This work provides the first broadband optical characterization of these 2D dilute magnetic semiconductors, shedding light on the novel and tunable electronic features of V‐doped WS2 monolayers.

2D Free-Standing GeS1-xSex with Composition-Tunable Bandgap for Tailored Polarimetric Optoelectronics.

Germanium-based monochalcogenides (i.e., GeS and GeSe) with desirable properties are promising candidates for the development of next-generation optoelectronic devices. However, they are still stuck with challenges, such as relatively fixed electronic band structure, unconfigurable optoelectronic characteristics, and difficulty in achieving free-standing growth. Herein, it is demonstrated that two-dimensional (2D) free-standing GeS1-xSex (0 ≤ x ≤ 1) nanoplates can be grown by low-pressure rapid physical vapor deposition (LPRPVD), fulfilling a continuously composition-tunable optical bandgap and electronic band structure. By leveraging the synergistic effect of composition-dependent modulation and free-standing growth, GeS1-xSex-based optoelectronic devices exhibit significantly configurable hole mobility from 6.22 × 10-4 to 1.24 cm2V-1s⁻1 and tunable responsivity from 8.6 to 311 AW-1 (635nm), as x varies from 0 to 1. Furthermore, the polarimetric sensitivity can be tailored from 4.3 (GeS0.29Se0.71) to 1.8 (GeSe) benefiting from alloy engineering. Finally, the tailored imaging capability is also demonstrated to show the application potential of GeS1-xSex alloy nanoplates. This work broadens the functionality of conventional binary materials and motivates the development of tailored polarimetric optoelectronic devices.

Structure and morphology of chars and activated carbons obtained from thermal treatment of coal and biomass origin materials, including their wastes: Results from the ICCP Microscopy of Carbon Materials Working Group

This paper describes the evaluation of petrographic textures in char and activated carbon derived from coal, coal by-products and biomass, formed during carbonization and activation processes. This work represents the results of interlaboratory exercises from 2016 to 2022 of the Microscopy of Carbon Materials Working Group in Commission III of the International Committee for Coal and Organic Petrology. The interlaboratory exercises were run on photomicrograph samples. For textural characterization of carbon materials, the existing American Society for Testing and Materials (ASTM) classification system for metallurgical coke was applied. Morphological differences were evaluated in 29 carbon material types, including 22 char samples, and 7 activated carbon (AC) samples obtained experimentally using conventional direct/indirect and microwave heating technologies. This approach gives an extended view on the identification of microporous carbons, and how a certain heat treatment develops a certain optical texture and structure in a raw material. The requested evaluation of carbon materials was related to their porosity, origin, extent, and characteristics, which are particular to each carbon material type. Because carbon matrices can form a wide range of optical textures during heat treatment it is important to demonstrate which carbon occurrences will have a crucial role in industrial applications dominated by adsorption phenomena.The interlaboratory exercises included 17 participants from 14 laboratories. Four sets of digital black and white and colour photomicrographs were distributed, which in total comprised 184 fields of different types of carbon material. The results were evaluated based on four levels: (i) optical texture (isotropic/anisotropic), (ii) optical type and size (punctiform, mosaic, fiber, ribbon, domain), iii) morphology (porous, non-porous/massive), and (iv) particle origin (precursor type).The statistical method applied to evaluate the results was based on “raw agreement indices”. Comparative analyses of the average values of the level of overall agreement showed homogeneity in the results, the mean value was 89%, with a minimum value of 87% and a maximum value of 91% for those who participated in at least three out of four exercises.

Off-Axis Co-Optical Path Large-Range Line Scanning Chromatic Confocal Sensor

This article proposes a line scanning chromatic confocal sensor to solve the problem of limited chromatic confocal measurement due to the small measurement range and low measurement efficiency in the industrial inspection process. To obtain an extensive dispersion range, the advantages of a simple single-axis structure are combined with the advantages of a large luminous flux of a biaxial structure. Considering large-scale measurement, our sensor uses off-axis rays to limit the illumination path and imaging path to the same optical path structure. At the same time, the field of view is expanded, and a symmetrical structure is adopted to provide a compact optical path and improve space utilization. The simulation and physical system test results shows that the sensor scanning line length is 12.5 mm, and the axial measurement range in the 450 nm to 750 nm band is better than 20 mm. The axial resolution of the detector is ±1 µm combined with the subpixel centroid extraction data processing method, and the maximum allowable tilt angle for specular reflection samples is ±7°. The thicknesses of transparent standard flat glass and the wet collagen membrane are measured. The maximum average error is 1.3 µm, and the relative error is within 0.7%. The constructed sensor is of great significance for rapidly measuring the three-dimensional profile, flatness, and thickness in the fields of transparent biological samples, optics, micromechanics, and semiconductors.

Thulium-doped titanate-germanate glasses for infrared photonics

In this paper, we performed a comparative spectroscopic analysis of Tm3+-doped glasses based on GeO2-BaO-Ga2O3 (GBG) and TiO2-GeO2-BaO-Ga2O3 (TGBG) to achieve broadband luminescence at 1.8 μm. Glasses were prepared at different doping concentrations (0.05 mol% and 1mol%) in order to investigate the effect of Tm3+ ions as well as host composition (GeO2:TiO2 molar ratios) on near-IR luminescence properties. We report on the hypersensitivity of the transition 3H6 → 3F4 of Tm3+ in a series of titanate-germanate glasses, which was shifted to longer wavelengths with increasing TiO2 concentration. The relative intensity of the main near-IR emission band corresponding to the 3F4 → 3H6 (1.8 μm) transition of Tm3+ was 4.8-fold enhanced for glass with molar ratio GeO2:TiO2 = 1:5 compared to GBG glass system. We observed the luminescence quenching phenomena for samples containing more than 0.5 mol% of Tm3+ ions. The calculated spectroscopic parameters, such as measured luminescence lifetime (τm) and the quantum efficiency (η), were discussed and compared to the different laser glasses. Importantly, luminescence decay curves have been examined using the Inokuti-Hirayama model. Additionally, the correlation between optical properties and local structure in glasses was well evidenced by Raman spectroscopy. The proposed strategy, in combination with various chemical composition of glass host activated by various Tm2O3 concentration, might be beneficial for modern near-infrared photonics.

A Real-Time Monitoring Method for Selective Laser Melting of TA1 Materials Based on Radiation Detection of a Molten Pool

Selective laser melting (SLM) technology is a promising additive manufacturing technology. However, due to the numerous influencing factors in this complex process, a reliable real-time method is needed to monitor the forming process of SLM. The molten pool is the smallest forming unit in the SLM process, the consistency of which can effectively reflect the quality of the printing process. By using a coaxial optical path structure and a compound amplifier circuit, high-speed acquisition of molten pool radiation can be realized. Next, single factor analysis and orthogonal experimentation were used to investigate the influence levels of key process parameters on the radiation of molten pool. In addition, numerical simulation was carried out with the same parameter setting schemes, the results of which are consistent with those in radiation detection experiments. It is shown that the laser power has the greatest effect on the radiation of the molten pool, while the scanning speed and the hatch spacing have little effect on the radiation. Finally, the positioning experiment involving the small hole structure was carried out, and the experimental results showed that the device could accurately locate the position coordinates of the given hole structure.

Effects of Static Electric Fields on the Excitations of Silver Nanowire Dimers.

We theoretically studied the introduction of static electric fields to Ag10 nanowire dimer systems, including the effects of this field on optical absorption characteristics and the orbitals responsible for these excitations. Linear-response time-dependent density functional theory computations were performed on three distinct dimer systems: end-to-end, parallel, and 90° angle dimer systems separated by a closest interparticle distance of 7.0 Å. The calculations were performed in the presence of a 0.1 V/Å electric field strength applied in the z and y directions. The orientation of the dimer system and the direction of the applied static electric field each play a significant role in the resulting absorption spectra and the electronic structure of the nanowires. As a result, a dimer system can exhibit a blue shift for the longitudinal excitation and a red shift for the transverse excitation in the presence of one direction of the static electric field but not for the other direction. Notably, the electron density shifts from one nanowire to the other in the presence of the static electric field. Changes in optical characteristics and electronic structure suggest that the usage of a static electric field with a particular spatial configuration of nanowires provides a way to tune the optical properties of the system.

Computational Study of the Effect of the Size-Dependent Dielectric Functions of Gold Nanomaterials on Optical Properties

The effect of size on the optical properties of gold nanomaterials has been studied using the theoretical Drude–Sommerfield model. The real and imaginary parts of the dielectric function of bulk as a function of wavelength due to free electron contribution and the real and imaginary parts of the dielectric function of nanogold materials as a function of wavelength due to free electron and bond electron contribution are calculated. The real and imaginary parts of the dielectric function of bulk as a function of wavelength due to the free electron contribution graph and The real and imaginary parts of the dielectric function of nanogold materials as a function of wavelength due to free electron and bond electron contributions are plotted. As we observed from the graphs, the real dielectric functions of both bulk and nanogold materials are inversely proportional to wavelength. The imaginary part of the dielectric function of bulk gold materials is independent of wavelength. At high wavelengths, the size of the gold nanomaterial is highly influenced by both real and imagined dielectric functions at high waves. As the wavelength increases, the effect of the size on the dielectric function also increases. The size-dependent dielectric function of nanomaterials is highly influenced by their optical properties and electrical structure.

Influence of initial temperature of water analyte on the readings of optical sensors based on surface plasmon resonance

The analysis of additional aspects of thermal influence on the sensory effect of the three-layer optical structure “prism - gold nanolayer - water” was continued. Here, the influence of the initial temperature of the “gold nanolayer - water” system on the surface plasmon resonance wavelength change is studies. It was established that the change in the value of the sensor effect along the wavelength of the surface plasmon resonance in the range of initial temperatures from 20 °C to 25 °C is insignificant. With an increase in the initial temperature to ∼100 °C, the change in the surface plasmon resonance wavelength can reach 0.75%, and is fixed experimentally.

Comparative study on the effects of chitosan, carrageenan, and sodium alginate on the film-forming properties of fish skin gelatin

Polysaccharides are commonly used to improve the film-forming properties of gelatin due to their wide range of sources, safety, and edible properties. However, there has been no systematic study comparing the effects of different polysaccharides on the film-forming properties of gelatin. Effects of chitosan, carrageenan, and sodium alginate on the optical properties, mechanical properties, thermal stability, hydrophilicity, and structure properties of gelatin films were systematically compared. Adding chitosan effectively reduced the ultraviolet transmittance of gelatin film. With an increase in chitosan concentration from 2 g/L to 8 g/L, the melting transition temperature (Tm) of gelatin film increased from 74 °C to 101 °C. Additionally, water vapor permeability decreased from 2.2 ± 0.23 (g.mm)/m2.h.kpa to 1.2 ± 0.18 (g.mm)/m2.h.kpa and water solubility decreased from 75% to 66%. Adding carrageenan and sodium alginate respectively increased the Tm of gelatin film to 92 °C and 84 °C; however, their addition reduced hydrophobicity and elongation at break for gelatin films. X-ray diffraction results suggested good compatibility between gelatin and all three polysaccharides while Fourier transform infrared spectrum results confirmed hydrogen bond interaction between gelatin and polysaccharides with a more orderly structure observed in gelatin films after adding polysaccharides.

Improving the error compensation capability in self-mixing interferometry

A scheme to improve the error compensation capability in self-mixing interferometry is proposed. Two beams of different frequencies are used as the measurement and reference light to compensate for the error. The short-term drift of the system is 12 nm and the long-term drift is 59 nm, and the experimental results show the effectiveness of the compensation. The performance is also evaluated, and the linearity of the frequency measurement can reach the order of 10−5, and the maximal standard deviation of the amplitude precision is 4.31 nm. The optical structure of this scheme is simple, the optical paths of measurement and reference light are easy to adjust, and the system has high robustness, which can be used as a sensor for real-time monitoring in practical engineering.

“Visible range curvature fiber-optic sensor with low strain-temperature dependence”

This manuscript introduces and demonstrates a visible curvature fiber optic sensor using an all-fiber Mach-Zehnder interferometer. The all-fiber interferometer was constructed using an in-line optical fiber sandwich structure, utilizing fibers specifically designed for the visible range. We demonstrate the reproducibility of the curvature sensor fabricating several distinct interferometers. These devices were subjected to curvature testing, exhibiting suitable wavelength shifts and achieving a maximal sensitivity of −10.44 nm/m−1. The hysteresis analysis shows minimal path deviation, and the statistical ANOVA analysis reveals a consistent mean trend with a minimal Prob > F value of 9.30472 × 10−55. Consequently, the hysteresis analysis indicates that the error in the curvature direction has a minimal impact on the measurement, and the low Prob > F value ensures that the curvature measurements cannot overlap. Then, accurate and high reproducibility of the curvature measurements can be expected. The results validate that the optical fiber structure is among the limited approaches to phase modulation interference within the visible range, representing a competitive alternative for curvature measurement.

Continuous optical zoom telescopic system based on liquid lenses

Telescopes play an essential important role in the fields of astronomical observation, emergency rescue, etc. The traditional telescopes achieve zoom function through the mechanical movement of the solid lenses, usually requiring refocusing after magnification adjustment. Therefore, the traditional telescopes lack adaptability, port-ability and real-time capability. In this paper, a continuous optical zoom telescopic system based on liquid lenses is proposed. The main components of the system consist of an objective lens, an eyepiece, and a zoom group composed of six pieces of liquid lenses. By adjusting the external voltages on the liquid lenses, the zoom telescopic system can achieve continuous optical zoom from ∼1.0× to ∼4.0× operating with an angular resolution from 28.648" to 19.098", and the magnification switching time is ∼50ms. The optical structure of the zoom telescopic system with excellent performance is given, and its feasibility is demonstrated by simulations and experiments. The proposed system with fast response, portability and high adaptability is expected to be applied to astronomical observation, emergency rescue and so on.

Humidity sensing characteristics of compact coupled optical fiber structure by microsphere and tapered capillary tube

In this paper, an optical fiber humidity sensor has been proposed based on the coupling structure using BaTiO3 microsphere and conical cavity of capillary pigtail. The sensitive material polyvinyl alcohol (PVA) was coated near the coupling region of microsphere and conical cavity to improve its sensing performance. The humidity sensitivity has been demonstrated to be 0.09 dBm/%RH based on intensity demodulation technique. The morphological parameters of the coupling structure are further optimized to obtain the maximum sensitivity of −0.297 dBm/%RH. Compared with other microsphere based optical fiber sensors, the sensor has the advantages of compact structure, simple manufacture, low production cost, high sensitivity and good stability.