Optical Transmission Properties Research Articles

Predicting Optical Properties of NiO Films Fabricated by RF Magnetron Sputtering: A Machine Learning Approach

NiO films with different thicknesses (100, 150, 200, 250, 300 and 400nm) were grown on glass substrates using the RF Magnetron sputtering method and their optical transmittance properties were analysed with a spectrophotometer. An innovative aspect of this work was the application of machine learning techniques used to derive new insights from experimental data. Four different machine learning algorithms -ANFIS, Artificial Neural Networks (ANN), Support Vector Machines (SVM) and Gaussian Process Regression (GPR)- were tested. While the models were trained using films of different thicknesses, a randomly selected 75% of the whole dataset was used for model testing and the remaining 25% of the films were used for testing the models. Among these, ANN and GPR models were found to be the most successful models. Using these models, the energy band gaps were estimated at 1nm intervals and the values ranged from approximately 3.50eV to 3.76eV.

Near-Surfaces and Bulk Modification of Silicone Rubber under UV- and Vacuum UV-Irradiation Using Excimer and Hg Lamps.

The surface properties of silicone rubber can be modified by irradiation with light from the vacuum ultraviolet (VUV) spectral range of less than 200 nm. After VUV-irradiation at 185 nm with a low-pressure mercury (Hg) lamp, a reduction in residual-dust-coverage (PA fibers) of up to 80% was found. At the same time, the long wavelength UV-radiation at 254 nm of the Hg lamp causes a reduction in the optical transmission properties of the silicone bulk. The near-surface and bulk modification of optically highly transparent silicone rubber was analyzed using XPS, ATR, transmission measurements, and investigations into the reduction of the residual-dust-coverage. A comparison was made between a Hg lamp and an excimer lamp at 172 nm. The results provide valuable information for selecting the appropriate irradiation source, depending on the desired spectral range for a given application. The results indicate that excimer lamps should be preferred for optical applications in the UV-spectral range, while Hg lamps are equally suitable for applications in the visible spectral range despite low transmission losses of less than 0.5%. The irradiation dose data were obtained using a ray tracing simulation as part of these investigations to overcome limitations of UV-sensors, such as their accelerated aging and angular dependence.

(Invited) In-Situ Observation of Silicon Solution Growth: Observation Principle and Effect of Al Addition to Si-Cr Solvent

The in-situ interface observation of silicon carbide (SiC) solution growth effectively elucidates various phenomena occurring at the growth front. To investigate this observation technique from the perspective of the optical transmission properties of SiC, the optical absorption properties of 3C-, 4H-, and 6H-SiC were measured over a wide range of temperatures. The obtained absorption properties indicate the optical conditions necessary for in-situ observation and the possibility of identifying different polytype inclusions. Furthermore, the effect of Al addition to the Si-Cr solvent on the SiC growth interface, where Al addition is known to be effective for growing high-quality SiC, was investigated by in situ observations. It was clarified that the presence of Al suppressed the formation of step pinning, resulting in preventing the formation of bunching steps and subsequent roughening of the growth interface.

High-fidelity decryption technology for visual cryptography based on incoherent optical polarization XNOR operation

In this paper, we propose an optical high-fidelity decryption technology for Visual Cryptography (VC) based on incoherent optical polarization exclusive NOR (XNOR) operation. The plaintext image is divided into two binary ciphertexts by the Random-Grid-based Visual Secret Sharing (RGVSS) algorithm. These ciphertexts are printed onto the polarizing films with orthogonal polarization. The P- and S-polarizing pixels in the polarizing films represent the “black” and “white” pixels of the ciphertexts, respectively. Due to the optical transmission property of polarizing film, the pixel in the decrypted image appears bright only when the stacked pixels for the two ciphertexts have the same polarizing orientation. High-fidelity image decryption is then achieved. The proposed technology has been successfully demonstrated through simulation and experimentation. Thanks to its advantages of no pixel expansion, incoherent illumination, being free of computer assistance, and flexibility of ciphertext carriers, this method provides a broad prospect for convenient, large-format, high-fidelity information recovery applications for VC.

Impact of incremental zinc-oxide incorporation on optical, magnetic, mechanical and photon transmission properties of K2O, SrF2, PbO containing borate-glasses

This study examines the radiation shielding properties of borate glass systems, with a focus on the simultaneous enhancement of optical, mechanical, and magnetic characteristics. The glass composition is represented by formula (55-x)B2O3+25PbO+10SrF2+10K2O + xZnO (where x: 0.0–10.0 mol%). By manipulating the ZnO concentration, we aimed to investigate its role as a radiation attenuator and its effects on the glass's optical, mechanical, and magnetic properties. Using traditional melt-quenching techniques, we produced the glass samples and examined their density, molar volume, linear attenuation coefficients (GLAC), mean free paths (GMFP), half-value layers (GHVL), and optical and magnetic properties. Our findings demonstrate that higher ZnO concentrations lead to a significant increase in density and a corresponding decrease in molar volume, thereby enhancing the glasses' ability to shield against gamma radiation. The radiation attenuation analysis revealed that increasing ZnO content substantially improves GLAC values across the energy range of 356–1333 keV. Additionally, ZnO incorporation decreases the optical bandgap, shifting the UV absorption edge to shorter wavelengths and enhancing UV dielectric capacity. Magnetic properties were assessed using vibrating sample magnetometer (VSM) measurements, showing a strong correlation between ZnO content and the effective atomic number (Zeff). It can be concluded that ZnO not only contributes to radiation shielding but also modifies the electronic structure of the glass, impacting its optical absorption properties.

Mechanically robust and self-cleaning antireflective coatings for photovoltaic modules

As the conversion efficiency of solar cells approaches its theoretical upper limit, the importance of photon management in enhancing photovoltaic modules performance becomes paramount. One promising approach involves the application of antireflective coatings to the surface of the photovoltaic glass to improve its transmittance. However, balancing mechanical durability, self-cleaning characteristics, and optical performance for photovoltaic applications remains challenging. This study focuses on synthesizing a composite coating through the sol-gel method, aiming to achieve high optical transmittance and superior mechanical properties. Hollow silica nanoparticles (HSN) are employed to achieve a reduced refractive index, while a composite sol of zirconium dioxide (ZrO2) and titania (TiO2) is utilized to enhance mechanical strength and hydrophilicity. The prepared composite coatings demonstrate notable improvements, with the photovoltaic transmittance (TPV) increasing from 88.31 % to 94.03 % in the 300–1100 nm wavelength range, with peak transmittance reaching 98.01 %. Additionally, the coatings exhibited a pencil hardness rating of 3H alongside exceptional abrasion resistance, affirming their potential for enduring practical deployment. When compared to uncoated glass, modules integrated with these composite coatings showed a significant increase in short-circuit current density (JSC) by 1.28 mA cm-2 and in photoelectric conversion efficiency (PCE) by 0.70 %. These results highlight the composite coatings' capacity to enhance the conversion efficiency of photovoltaic modules significantly. By attempting to prepare anti reflective coatings with high mechanical strength and self-cleaning properties, this study is expected to make a valuable contribution to the advancement of sustainable and durable solar cell technology.

On the potential of Transparent Rare-Earth-Free ZnAl2O4 Ceramics targeted at the UV-C to UV-B emission

Materials capable of emitting in the ultraviolet UV-C to UV-B spectral range have received considerable attention due to their potential applications in biophotonics, plant lighting, optical cleaning, sterilization, and disinfection. However, progress in the development of phosphors that emit in this short-wavelength range has been relatively sluggish. Most UV-C phosphors developed to date are based on hosts doped with the rare-earth cation Pr3+ due to its bright UV luminescence originating from the 4f15d1 → 4f2 interconfigurational transitions. In this study, we explore how the UV emission can be tailored to different wavelength ranges by developing rare-earth-free materials. Specifically, we demonstrate that UV-C to UV-B emission can be achieved in transparent ZnAl2O4 – based ceramics. For the first time, such transparent ceramics have been successfully produced with the help of reactive spark plasma sintering with SiO2 or LiF additives, which modified the process of grain growth resulting in an increase in the average grain size from 250 nm to 4 µm. Moreover, these additives also improved the optical transmission properties, with in-line transmission measurements at a wavelength of 550 nm reaching values of 50 % and nearly 65 % in the infrared region. Depending on the addition of SiO2 and LiF, the excitation by photons with energy exceeding 6.2 eV has generated the deep UV emission peaks in the range from 230 to 300 nm. Based on the analysis of the results of luminescence spectroscopy and EPR studies, the observed UV-C emission is suggested to originate from the excitons localised near oxygen vacancies. The number of vacancies is the highest in undoped ZnAl2O4 ceramics, whereas adding SiO2 and LiF suppresses their number and modifies their local environment due to changes in charge compensation, which in turn allows tuning the spectral position of the UV-C band. The quantum yield of the UV-C emission reached 5 % for undoped ZnAl2O4 ceramics. The sintered ZnAl2O4 transparent ceramic shows a versatile solution for next-generation rare-earth-free deep-UV devices.

Cryomilling-assisted high purity β-chitin extraction from Uroteuthis edulis pens

We report on the extraction of β-chitin from pens (or Gladius) of Uroteuthis edulis, a squid species prevalent in the Pacific coastal regions of East Asia. In particular, we employ cryogenic mechanical grinding (or cryomilling) as a pre-treatment process for the raw squid pens. We show that the cryomilling step enables an effective pulverization of the raw materials, which facilitates the removal of protein residues allowing the extraction of high-purity β-chitin with a high acetylation degree (∼97 %) and crystallinity (∼82 %). We also demonstrate that the Uroteuthis edulis extract β-chitin affords a free-standing film with excellent optical transmittance and mechanical properties.

Transparent Glass Composite Scintillator with High Crystallinity for Efficient Thermal Neutron Detection

AbstractThe sensitive and rapid detection of thermal neutrons holds significant importance in various fields such as energy utilization, medical treatment, and national defense. However, the available thermal neutron scintillator is difficult to reach this target, mainly limited by the optical and scintillating performance. Herein, the in situ crystallization strategy of glass to construct scintillation glass composites for efficient thermal neutron detection is proposed. The congruent crystallization of the hybridized alkali earth silicate glass system may not only achieve high crystallinity, but also will keep the refractive indexing matching between the precipitated crystal and precursor glass phases. The prepared glass composites feature high luminescence efficiency, optical transmission and excellent neutron response properties. These factors collectively contribute to the robust neutron scintillation performance with a light output of ≈36 000 photons/neutron, which represents the highest value among glass‐based scintillators. Moreover, the composite configuration brings about the additional function of thermal neutron and γ‐ray discrimination. By using this composite scintillator, the neutron detector is constructed and demonstrates its application for detecting thermal neutron and distinguishing it from γ‐ray in an online way. The studies prove that glass composites with high crystallinity are expected to be promising candidates for a new generation of multifunctional neutron detectors.

Fluorine atom substituted aromatic polyimides: Unlocking extraordinary dielectric performance and comprehensive advantages

Low-dielectric polymers face prominent development challenges at high frequency. Particularly, the relationship between the high-frequency dielectric loss and polymer structures remains not clear enough. Besides, the strategies for achieving low dielectric loss usually have to scarify other important materials properties, e.g., heat resistance or dimensional stability. Herein, fluorine-containing aromatic polyimides were systematically investigated. Among them, simple fluorine atom (-F) substituted polyimides exhibit remarkable low dielectric loss at high frequency (10 GHz) as well as comprehensive advantages, including near-zero thermal expansion coefficient, extremely high thermal decomposition stability, high optical transmittance and excellent mechanical properties. The fundamental mechanisms of low dielectric loss are fully discussed. Benefiting from the unique electric effect and compact size of -F group, -F substituted polyimides display low dipolar density and strongly restricted dipolar motion, contributing to a reduced permanent dipolar polarization loss. Moreover, the concept of induced dipolar polarization was introduced to illustrate the nontrivial impact of F-substituted effect on conjugated electron cloud polarization loss in aromatic polymer system. This work not only provides valuable insights for understanding the mechanism of dielectric loss at high frequency for aromatic polymers, but also opens up broader application possibilities of polyimides in microelectronic and wireless communications industries.

Al2O3/SnC heterostructure: Physical properties, regulation effect and device design

Two van der Waals (vdW) heterostructures between Al2O3 and SnC monolayers are constructed by the Generalised Lattice Matching (GLM) method. We calculate the elastic constants of monolayers and heterostructure and find that the heterostructures show larger Young’s modulus (220−234) N/m compared with Al2O3 (SnC), the reasonable Poisson’s ratio is about 0.3 and gravity-induced bending is the order of 104, which is comparable to graphene. The electronic properties, optical absorption coefficient and transmission properties of the heterostructure also have been investigated. Some important discoveries can be obtained: The Al2O3/SnC heterostructure shows an indirect bandgap (Eg) semiconductor with 1.70 eV and type II band arrangement when the ferroelectric polarization of Al2O3 points to SnC. While the polarization direction of Al2O3 is opposite, the Eg is zero. The physical properties are manipulated by some conditions (strain and electric field), leading to transitioning between Type II and I semiconductors, semiconductors and metal can be experienced. Moreover, the heterostructures prefer the higher light adsorption coefficient (105 cm−1) compared to monolayers. The transport properties of the Al2O3/SnC linked by two silicene electrodes show an excellent tunnel electroresistance (TER) effect with 108, moreover, the negative differential resistance (NDR) effect and switching effect also can be observed.

Enhancing Liquid Crystal Properties through Nanoparticle Doping: A Mini Review

Liquid crystals doped with nanoscale particles have recently acquired popularity, improving their capabilities and applications. The impact of doping metallic and metal-oxide nanoparticles as well as other nanoparticles in liquid crystals is presented in this brief review. Silver nanoparticles (Ag NPs) have an effect on phase transitions, molecular alignment and electrical properties such as threshold voltage and response time. The optical tilt and electro-optical characteristics of gold nanoparticles (Au NPs) are improved. Metal-oxide nanoparticles such as MgO, ZnO, Al2O3, CuO and SiO2 enhance dielectric properties, mitigate screening effects, increase birefringence, and reduce light leakage. Doping carbon nanotubes (CNTs) influences impedance, optical transmittance and electro-optical properties. The review aims to study the effects of nanoparticle doping on liquid crystal features such as phase transitions, molecular alignment, electrical and optical properties, dielectric behavior, and impedance. A better understanding of these modifications can lead to more applications for liquid crystal in areas such as sensors, displays, optoelectronics, and photovoltaics.

Synthesis of novel Cu/Fe based benzene Dicarboxylate (BDC) metal organic frameworks and investigations into their optical and electrochemical properties

In the recent past Metal-organic frameworks (MOFs) based thin films have demonstrated superior performance in various technological applications such as optical and optoelectronic devices, electrochemical energy storage, catalysis, and sensing. Herein we report tuning the optical performance of stable complexes using Cu and Fe metal ions with carboxylate benzene dicarboxylic (BDC), leading toward the formation of novel MOF structures. The formation of Cu-BDC and Fe-BDC were confirmed by XRD and SEM studies. The thermal stability of two MOFs was investigated, indicating that, the Cu-BDC is more stable than Fe-BDC. Further, the optical properties were investigated in the wavelength range 325–1100 nm, and the Fe-BDC exhibited greater optical transmission properties than Cu-BDC by 33 %, as investigated by Wemple-DiDomenico and Tauc models. The dispersion parameters related to optical studies for Cu-BDC were better in comparison to Fe-BDC, which could be attributed to the increase in Cu valence electrons due to an increase in the number of cations. The electrochemical behavior in terms of CV measurements shows the presence of pseudo capacitance in both Fe-BDC and Cu-BDC MOFs. The improved CV performance of Cu-BDC MOF suggests that it could be used as a storage material. This work successfully demonstrates the tailoring of optical properties related to MOF thin films through the formation of stable complexes using BDC as a potential material for the fabrication of OLED's and Solar cells. The improved CV performance suggests that these MOF based materials could be used as anodes in fabrication of batteries or supercapacitors.

Optical pressure sensor based on Fano resonance in a coupled resonator system

Optical pressure sensor plays a very important role in micro deformation detection, environmental monitoring, and medical fields. However, the quantitative relationship between the applied pressure and the optical response of the resonator before and after deformation is difficult to obtain. In this paper, a coupled resonator system based on metal-insulator-metal waveguide for optical pressure sensor is proposed. The mechanical properties of the system and the optical transmission properties before and after applied pressure are analyzed in detail by using the finite element method. Simulation results show that the maximum deformation of the resonator has a simple linear relationship with the applied pressure. We give a direct definition of the sensitivity of the optical pressure sensor. And based on the Fano resonance phenomenon caused by the coupling the slot cavity with the groove cavity, the optical pressure sensor with a sensitivity of 6.75 nm/MPa is achieved. In addition, we add stub resonator to obtain double Fano resonance phenomenon, and with the change of external pressure, the two Fano line types show different change laws. Specifically, a suitable pressure value can make a double Fano resonance become a single Fano resonance. The special features of our suggested structure are applicable to detecting optical property changes under different pressures, chemical high pressure experimental measurement and study of chemical reaction kinetics process.

Macro- and micro-structural manifestation and engineering of large-size polycrystalline ZnSe

Polycrystalline ZnSe materials with sizes of 100 mm were grown by the CVD method, and their constitution structures and defects were investigated to analyze the influence of the preparation conditions on the optical transmission properties of the materials.

INFLUENCE OF ASPECT RATIO OF TEMPO-OXIDIZED CELLULOSE NANOFIBERS (TOCNs) FROM WOOD PULP ON POLYMERIC MEMBRANE PROPERTIES

The incorporation of TEMPO-oxidized cellulose nanofibers (TOCNs) derived from wood pulp resulted in an improvement in the characteristics of polymeric membranes made up of poly (methyl vinyl ether maleic acid)/PMVEMA and poly (ethylene glycol)/PEG. The membranes were constructed, and TOCNs were included in the formulation at a rate of 5 wt%. TOCNs were categorized as either short or long, depending on the aspect ratio measurement. According to the findings of the research, the various lengths of TOCNs resulted in variances in the optical transmittance properties, contact angles, and whiteness level of the membranes, in addition to a little variation in the tensile and thermal properties of the material. When compared to short TOCNs, long TOCNs offer somewhat improved performance in terms of optical transmittance, whiteness level, tensile characteristics, and thermal stability. The results of this study reveal the significance of the morphology of nanocellulose in determining the properties of the composite that includes it. Thus, the characteristics of the target membrane were greatly influenced by nanocellulose morphology.

Transparent electromagnetic absorption film derived from the biomass derivate

Electromagnetic wave absorption materials featuring small thicknesses and wide effective absorption bandwidth (EAB) are highly required for next-generation portable devices, wearable electronics, and blooming military applications. However, traditional EM particle absorbents, such as carbon-based, magnetic metal-based, and MXene-based materials are always visible black, which severely hinders their utilization as microwave-stealth smart window alternatives. Therefore, it is a critical challenge to fabricate flexible windows simultaneously possessing high optical transmittance and excellent EM wave absorption properties. Herein, we prepared a transparent wood composite with an optical transmittance value of more than ∼83% through a delignification and polymer composite immersion method. The delignification process could remove the light-absorbing lignin component, and the transparent woods were realized by immersing the delignified wood into refractive-index-matched pre-polymerized acrylamide (AM) including minor silver nanowires, carbon nanotubes, and reduced graphene oxides. In addition, due to the presence of numerous polarization centers originating from hydrophilic functional groups and conductive fillers, the transparent wood composite showed superior EM absorption performance, and EAB can reach 9.5 GHz, almost occupying the whole X band (8.2–12.4 GHz) and Ku band (12.4–18 GHz) at a thickness of 2.0 mm. Furthermore, the transparent wood presented a great insulative thermal performance with a low thermal conductivity of 0.45 W m−1 K−1 (half of common glass). The developed transparent wood composites offered significant potential as smart energy-efficient windows with the expectation to survive military equipment and alleviate EM pollution.

Stretchable polydimethylsiloxane/aligned electrospun cellulose acetate nanofibers composites with high transparency and fracture resistance

AbstractPolydimethylsiloxane (PDMS) is recognized as an excellent stretchable substrate in wearable electronics, due to its desirable properties such as tensile properties, transparency, thermal stability, non‐toxicity, and good biocompatibility. However, its limited fracture toughness and susceptibility to cracking significantly reduce the material's overall durability. In this study, the solution casting method was applied to prepare the nanofibers composites combined stretchable PDMS and aligned electrospun cellulose acetate (CA) to improve its mechanical properties and keep its transparency. The results showed that composites containing 3 wt% loadings of electrospun CA nanofibers exhibited a light transmittance exceeding 85% within the visible light range. Specifically, the PDMS/CA‐400 composites exhibited maximum improvements in comparison to pure PDMS. Notably, the tensile strength increased significantly from 2.1 to 3.0 MPa, while the toughness increased from 0.93 to 2.49 MJ/m3. In addition, the tensile strength of PDMS/CA‐400 composites with pre‐cut cracks increased from 0.2 to 1.4 MPa, and the fracture toughness increased from 14.78 to 174.42 kJ/m3, which were respectively 7 and 12 times compared to pure PDMS. Scanning electron microscope images showed that PDMS formed good interfacial interaction with CA nanofibers. This study introduces a novel method utilizing electrospun nanofibers to create transparent and fracture‐resistant stretchable composites, offering promising enhancements for the durability of wearable electronic devices.Highlights Explore the impact of the speed of receiving rollers on the degree of fiber arrangement. PDMS/CA‐400 composite material shows good light transmittance and high fracture resistance. The tight interface between the fiber and the matrix improves the optical transmission and mechanical properties of the composite materials.

Structure, optical and magnetic properties of PVA/CuO/CoFe2O4 nanocomposite films for flexible magneto-electronic applications

Pure polyvinyl alcohol (PVA) and its nanocomposites with CuO and/or CoFe2O4 films have been prepared with different weights of ≤ 5 %. The structure of the films shows an orthorhombic phase of semi-crystalline polymer for PVA, a monoclinic phase for CuO, and a cubic phase of CoFe2O4 in nanocomposite films with particle sizes ≤ 25.5 nm, as determined by the XRD technique. Surface morphology by TEM of representative films shows the crystalline structure and nanoparticles and nanorods of individual CuO and/or CoFe2O4 compounds. The optical transmission and reflection properties of films have been measured, and the optical band gap has been estimated, showing that variable values (1.4–4 eV) can be controlled by controlling the percentage of CuO and/or CoFe2O4 in films. Magnetic investigation shows diamagnetic behavior for PVA and paramagnetic behavior for PC1, PC3, while PC5 has a very weak ferromagnetic response. Whereas nanocomposites with different contents of CoFe2O4 exhibit smooth ferromagnetic behavior with increasing Ms values. Ferromagnetic behavior has been confirmed via a convex Arrott–Belov–Kouvel plot. The improvement of magnetic properties makes the prepared films suitable to be used in various fields, such as antenna system miniaturization and flexible magneto-electronic applications.

Effect of rapid thermal annealing treatment on up-conversion luminescence in Er3+/Yb3+ co-doped NaYF4 oxy-fluoride glass-ceramics

The heat-treatment plays a decisive role in the process of crystal phase precipitation and the microscopic features of the fluoride particles, which determines the optical transmittance and up-conversion luminescence (UCL) properties. In this work, we successfully synthesized Er3+/Yb3+ co-doped UCL transparent oxy-fluoride glass-ceramics (GCs) by precipitation of NaYF4 nanoparticles using a rapid thermal annealing (RTA) treatment with ultra-high heating rate (100 K/s). The particle sizes of NaYF4 nanoprecipitation inside glass-ceramic is only 4–5 nm, which is much smaller than the 40–50 nm particle sizes obtained using normal-heating treatment. The GCs with ultra-small particle sizes provided a very high optical transmittance that is close to that of all-amorphous glass, but the intensity of UCL was similar to that of a sample prepared using a slower heating rate. Finally, under different heat treatment conditions the Er3+/Yb3+ co-doped NaYF4 transparent GCs with different particle sizes can be produced, the color and intensity of UCL were controllable.