Optical Index Research Articles

Stemflow dissolved organic matter in mixed temperate forests: temporal and interspecific variation of optical indices and development of a stemflow-specific PARAFAC model

Stemflow is a conduit for the transport of canopy-derived dissolved organic matter (DOM) to the forest floor. This study examined the character of stemflow DOM for four tree species over four phenophases (leafless, emergence, leafed, and senescence for deciduous species and leafed-winter, emergence, leafed- spring/summer, and senescence for coniferous species) occurring in temperate forests; namely, Betula lenta L. (sweet birch), Fagus grandifolia Ehrh. (American beech), Liriodendron tulipifera L. (yellow poplar), and Pinus rigida Mill. (pitch pine). American beech exhibited the lowest average specific UV absorbance at 254 nm (SUVA254) values, while yellow poplar displayed the highest values. SUVA254 values were largest in senescence and smallest in emergence. The spectral slope ratio was lower for pitch pine than the deciduous tree species. Humification index (HIX) values decreased across all species during the emergence phenophase. The developed and validated stemflow-specific four-component parallel factor analysis (PARAFAC) model demonstrated the combined influence of interspecific and temporal fluctuations on the composition of humic and protein-like substances within stemflow. By separating and examining stemflow DOM independent of throughfall, our study provides fresh insights into the spatiotemporal dynamics of stemflow inputs to near-trunk soils that may inform hot spots and hot moments theories.

Copper Distribution and Binding Affinity to Size-Fractioned Dissolved and Particulate Organic Matter in River Sediment

This study investigated the distribution of copper in sediment dissolved and particulate organic matter (DOM and POM) based on their size. The DOM and alkaline extracted POM (AEOM) were separated into five size fractions using a cross-flow ultrafiltration (CFUF) system. The results showed that Cu mass was mainly distributed in the low molecular weight (<1 kDa, LMW) fraction of the DOM with an average range of 78.1–83.1%. Conversely, the high molecular weight (1 kDa–0.45 μm, HMW) AEOM fraction had a higher distribution of Cu mass with an average range of 92.6–93.3%. The Cu and AEOM binding affinity ratios (CuBAAEOM) ranged from 17.0 to 149.6 μmol/g-C in site-1 and from 20.6 to 143.7 μmol/g-C in site-2. The HMW CuBAAEOM ratios were significantly higher than the LMW ratios. The Cu and DOM binding affinity ratios (CuBADOM) ranged from 5.6 to 358.6 μmol/g-C and 17.2 to 126.6 μmol/g-C in site-1 and site-2, respectively. However, the LMW CuBADOM ratios were significantly higher than the HMW ratios. Optical indices suggested that the AEOM had more aromaticity and terrestrial and allochthonous contributions than the DOM. The optical indices were significantly correlated with the CuBAAEOM ratios but weakly correlated with the CuBADOM ratios. Sediment exchange between POM and DOM may affect copper distribution. DOM has a low-molecular-weight composition, while POM retains high-molecular-weight organic matter.

Effect of Chain Orientation on Coupling of Optical and Mechanical Anisotropies of Polymer Films

Polymer films have broad applications in different industries with specific requirements for their optical and mechanical properties. In mass production, processing conditions during film formation that apply forces and motions in various directions to the film tend to manifest preferred molecular chain orientation in the film microstructure, which unavoidably produces optical and mechanical anisotropies. In this paper, we investigate the effect of such macromolecular orientations on the optical and mechanical anisotropies of several polymer films, including polystyrene, poly(methyl methacrylate), poly(ethylene terephthalate), poly(ethylene naphthalate), poly(ether ether ketone), poly(ether sulfones), poly(ethylene chlorotrifluoroethylene), poly(phenylsulfone), and polycarbonate, at temperatures well below their respective glass transitions (Tg). The film mechanical responses, including elasticity, yielding, and post-yield behaviors, were obtained for the in- and out-of-plane directions utilizing tensile and nanoindentation testing methods, respectively. In addition, the net chain orientation within the films was evaluated by birefringence through analyzing the film optical refractive indices, which were verified and complemented by wide-angle X-ray scattering (WAXS) measurements. The results reveal a considerable quantitative correlation between the birefringence and the degree of elastic anisotropy and a qualitative correlation between the chain orientation and the film post-yield tensile instability (necking). These observations corroborate the interrelationship between the microstructure of polymer films and their optical and mechanical properties. In addition, they emphasize that process conditions can be selected to tune the optical and mechanical anisotropies to best serve the material performance in specific devices. We also propose an empirical equation to approximate the out-of-plane film stiffness based upon the optical and in-plane mechanical properties.

Deterministic quasi-continuous tuning of phase-change material integrated on a high-volume 300-mm silicon photonics platform

Programmable photonic integrated circuits (PICs) consisting of reconfigurable on-chip optical components have been creating new paradigms in various applications, such as integrated spectroscopy, multi-purpose microwave photonics, and optical information processing. Among many reconfiguration mechanisms, non-volatile chalcogenide phase-change materials (PCMs) exhibit a promising approach to the future very-large-scale programmable PICs, thanks to their zero static power and large optical index modulation, leading to extremely low energy consumption and ultra-compact footprints. However, the scalability of the current PCM-based programmable PICs is still limited since they are not directly off-the-shelf in commercial photonic foundries now. Here, we demonstrate a scalable platform harnessing the mature and reliable 300 mm silicon photonic fab, assisted by an in-house wide-bandgap PCM (Sb2S3) integration process. We show various non-volatile programmable devices, including micro-ring resonators, Mach-Zehnder interferometers and asymmetric directional couplers, with low loss (~0.0044 dB/µm), large phase shift (~0.012 π/µm) and high endurance (>5000 switching events with little performance degradation). Moreover, we showcase this platform’s capability of handling relatively complex structures such as multiple PIN diode heaters in devices, each independently controlling an Sb2S3 segment. By reliably setting the Sb2S3 segments to fully amorphous or crystalline state, we achieved deterministic multilevel operation. An asymmetric directional coupler with two unequal-length Sb2S3 segments showed the capability of four-level switching, beyond cross-and-bar binary states. We further showed unbalanced Mach-Zehnder interferometers with equal-length and unequal-length Sb2S3 segments, exhibiting reversible switching and a maximum of 5 (N+1,N=4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N+1,N=4$$\\end{document}) and 8 (2N,N=3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${2}^{N},N=3$$\\end{document}) equally spaced operation levels, respectively. This work lays the foundation for future programmable very-large-scale PICs with deterministic programmability.

Pressure-driven semiconducting to metallic transition in francium tin trihalides perovskite with improved optoelectronic performance: A DFT study

The objective of our study was to analyze the mechanical, magnetic, elastic, electrical, and optical characteristics of the halide-based perovskite FrSnX3 (X = Cl, Br, and I) at hydrostatic pressures ranging from 0 to 6 GPa. We conducted this analysis using first-principles calculations based on density functional theory. The thermodynamic and mechanical stability of the complex FrSnX3 (X = Cl, Br, and I) were calculated based on its formation enthalpy and elastic constant characteristics. The compound was found to be ductile and stable. FrSnCl3, FrSnBr3, and FrSnI3 are all classified as semiconductors according to band calculations. Their respective bandgaps are 1.046, 0.675, and 0.485 eV, respectively. These values remain constant when hydrostatic pressure is not applied. The bandgap and density of states of the three halides were examined to observe their variations with increasing induced pressure. The bandgaps of FrSnCl3, FrSnBr3, and FrSnI3 were measured to be 0 eV at pressures of 6, 4, and 2 GPa, respectively. In addition, a comprehensive study was conducted on the optical properties of cubic perovskites FrSnX3 (X = Cl, Br, and I) under different hydrostatic pressures ranging from 0 to 6 GPa. The investigation focused on analyzing the optical absorption, reflectivity, and refractive index, as well as the imaginary and real components of the dielectric functions. Under high pressure, the compound exhibited higher absorption capabilities for all compounds within the 10–13 eV range, transforming into a conductor. This property makes it well-suited for utilization in the UV spectrum. Chlorine exhibits the greatest absorption among all chemicals, whereas iodine demonstrates the least absorption. The reflectance values of all compounds range from 12% to 16% and increase with increasing pressure. At the energy level of zero, the refractive index’s real component ranges from 1.25 to 1.7, and it increases with increasing pressure. Chlorine has a relatively low refractive index compared to iodine. Bromine has the most pronounced variance. The dielectric characteristics typically vary from 4.5 to 7.5 F/m. As pressure increases, the charge storage capacities of all compounds increase. However, among these compounds, iodine has the highest capacity, while chlorine (Cl) has the lowest. The hydrostatic pressure applied to the structure FrSnX3 (X = Cl, Br, and I) causes it to become harder and more ductile. This is evident from the increasing values of the bulk, Young’s, and shear modulus, as well as the elastic constants (C11 and C12). We optimized the band structure and density of states by aligning the electrons in a co-linear location and assessed the magnetic properties. The diamagnetic characteristic of the FrSnX3 compound (where X = Cl, Br, and I) remained unchanged when subjected to increasing pressure. The results indicate that the perovskite material has exceptional absorption properties, indicating a change in its behavior from a transistor to a metal. The numerical findings highlight the potential applications of this material in photovoltaic cells, ultraviolet light absorbers, and optoelectronic devices.

The structural, magnetic, optoelectronic, and mechanical characteristics of NaGeX3 perovskites under pressure for soler-cell applications

This study examines the physical properties of germanium-based halide perovskite through Density Functional Theory (DFT) computations. The physical, optical, mechanical, and magnetic properties of NaGeX3 (X = Cl, Br, and I) were examined with the effects of hydrostatic pressure applied externally. The compounds were subjected to pressure variations ranging from 0 to 5 GPa. The results indicate a decrease in the band gap from the infrared to the visible spectrum. For NaGeCl3, NaGeBr3, and NaGeI3 the band gap decreased from 0.766 eV, 0.497 eV, and 0.400 eV to 0 eV, respectively, indicating the metallic behavior. The mechanical properties of NaGeX3 (X = Cl, Br, and I) demonstrate that for all three compounds, Bulk Modulus (B), Shear Modulus (G), Young’s Modulus (E), Poisson’s ratio (ν), and Pugh’s ratio B/G all increase with increasing pressure. It demonstrates that all these NaGeX3 (X = Cl, Br, I) compounds are ductile in nature. The compounds are determined to be diamagnetic based on their magnetic property investigation, which reveals no notable changes in behavior up to 5 GPa of rising pressure. To gain a better understanding of the properties of the material when incident light strikes its surface, researchers also looked in at optical absorption, reflectivity, dielectric constants, refractive index, conductivity, and loss functions. Pressure-induced NaGeX3 perovskite compounds, where X = Cl, Br, and I, show an increase in dielectric constant as pressure rises, suggesting a decrease in charge carrier recombination rates and a possibility for higher optoelectronic device efficiency. For all NaGeX3 compounds (where X = Cl, Br, and I), the maximum absorption coefficient peaks are located around 3 eV, indicating that increasing pressure increases optical conductivity. Additionally, they have significantly low reflectance throughout the visible spectrum and very narrow band gap, which indicates significant absorption and the possibility of effective Near-Infrared (NIR) Sensors, photodetector etc applications.

Optical nonlinear refractive index study by Z-scan technique of GOQDS dispersed in an aqueous solution

Optical nonlinear refractive index study by Z-scan technique of GOQDS dispersed in an aqueous solution

A Diamond Universe

Cosmology is currently facing some major challenges. In addition to dark matter and dark energy, the issue of ‘impossible’ galaxies has been brought to the fore by the James Webb Telescope. Something simple eludes us, and the various problems mentioned are interrelated. Our proposition is that, on the cosmological scale, it is appropriate to take a value of the speed of light c_c lower than its standard value c_0 in vacuum. This defines an optical index n_c=c_0 /c_c. We account for this ‘refringence’ by a Shapiro effect extended to the scale of the universe (use of Schwarzschild metric), described by its average density ρ_u and its equivalent gravitational radius R_u. Remarkably, universes with indices greater than two are entirely conceivable, and their characteristics are close to those we determine for our own. The velocities v of celestial objects are estimated from redshifts in ratios of the type v/c, where the speed c of light is usually taken to be equal to c_0. With an equal v/c ratio (all things considered, only the v/c ratio has any meaning), dividing c_0 by a certain factor α lowers the velocities v without postulating the existence of dark matter nor dark energy. Taking into account the problems cited earlier suggests a value of α close to 2.4. We are led to a lengthening of the age of the universe: it could reach 33 billion years. This would allow it to host in its relatively young phases objects that are already old and structured.

Corneal densitometry in Chinese adults with healthy corneas: associations with sex, age, ocular metrics, and optical characteristics

BackgroundStandardized corneal densitometry (CD) values in large samples of healthy Chinese individuals are scarce. Therefore, we aimed to determine the standard CD values using a Scheimpflug camera in healthy corneas, investigate the correlations of sex, age, and ocular parameters with corneal density, and explore the impact of corneal density on the forward scattering and optical quality of the eye.MethodsThis retrospective observational study involved 990 healthy Chinese individuals, including 494 males and 496 females (mean age: 23.88 ± 6.90 years). The CD values at various depths and radial areas of 0–12 mm were measured using a Scheimpflug camera. Densitometric measurements were expressed in standardized grayscale units (GSU). The optical scatter index (OSI), modulation transfer function cutoff values (MTFcutoff), and Strehl’s ratio (SR) were also determined using an optical quality analysis system.ResultsThe average CD within a 12 mm diameter area was 16.26 ± 1.35 GSU. The highest and lowest optical densities at different depths were observed in the anterior (21.41 ± 2.16 GSU) and posterior (12.00 ± 1.01 GSU) layers, respectively (P < 0.001). Similarly, the maximum and minimum optical densities at different radial areas were observed in the 10–12 mm (14.09 ± 0.93 GSU) and 2–6 mm (25.93 ± 4.77 GSU) circles, respectively (P < 0.001). There was no significant difference in the average CD within a 12 mm diameter area between males and females (P > 0.05). However, upon adjusting for age, central corneal thickness (CCT), corneal curvature, white-to-white (WTW) corneal diameter, and axial length, females exhibited a greater average CD within the 12 mm diameter and in the 6–10 mm and 10–12 mm circles than males. Age-related changes in CD were evident, except in the 2–6 mm circle. CCT, corneal curvature, WTW corneal diameter, and partial depth correlated with CD in the radial area, and CD in different areas correlated with the OSI, MTFcutoff, and SR (P < 0.05).ConclusionsThis study provides the normative CD measurement data of Chinese adults with healthy corneas, emphasizing the significance of sex, age, CCT, corneal curvature, and WTW corneal diameter in CD evaluation. Notably, elevated CD can lead to increased forward scattering within the eye, thereby affecting the optical quality.

Nonlinear optical properties of KnCl (n = 2–7) superalkali clusters

The lowest energy structures along with the low lying isomer, stabilities, electronic properties, optical properties and nonlinear optical responses of KnCl (n = 2–7) clusters were studied within the density functional theory. The second order energy difference, dissociation energy and GH-L (HOMO–LUMO gap) point out that KnCl (n = 3, 5, 7) clusters are more stable. The calculated adiabatic ionization energies (AIE) for the KnCl (n = 2–6) clusters are in agreement with the measured ionization energies. The optical properties, namely optical electronegativity and refractive index, depends on the GH-L energy values. The K atom capped planar rhombus geometry of the K4Cl causes the noticeable vibrational frequency shift compared to the rest of IR spectra of the clusters. The first static hyperpolarizability (β o) values are in the range of 2.33 × 103 –2.87 × 104 au and the second static hyperpolarizability varies between 5.74 × 106 au and 38.9 × 106 au for the cluster. The nonlinear optical response is due to the superalkali nature of KnCl (n = 2–7) clusters. From computed β vec values, the hyperpolarizability has projection on the dipole moment vector for the superalkalis except the K2Cl and K5Cl. The absorption spectra point out that KnCl (n = 6–7) clusters can be suitable as a NLO material since they have transparency in the deep UV region (λ< 300 nm).

A novel investigation into strain-induced changes in the physical properties and solar cell performances of lead-free Ca3NCl3 perovskite

The first-principle calculations were employed to analyze the structural, thermodynamic, electronic, optical, and mechanical properties of calcium-based halide perovskites, Ca3NCl3, under pressure variations from +6 % to −6%. The Ca3NCl3 materials are thermodynamically and dynamically stable, as indicated by the negative final enthalpy values obtained under pressures ranging from −6% to +6 %. The charge density maps confirm the existence of both ionic and covalent bonding features. The unstressed Ca3NCl3 has a direct bandgap of 1.66 eV with PBE functions, 2.32 eV with HSE functions and 1.48 eV with spin-orbit coupling (SOC) at the Γ point. When subjected to compressive strain, the bandgap reduces to 1.37 eV(PBE), 1.93 eV(HSE) and 1.08 eV(SOC) at −6% strain, causing a redshift in absorption coefficient peaks. Conversely, under tensile strain, the bandgap slightly rises to 1.92 eV(PBE), 2.60 eV(HSE) and 1.73 eV(SOC) at +6 % strain, resulting in a blueshift in absorption coefficient peaks. The Ca3NCl3 materials show enhanced optical absorption, loss function, conductivity, dielectric function, refractive index and reflectivity under applied pressure, making them more appropriate for use in solar absorbers, surgical tools, and optoelectronic devices. The investigation of the mechanical properties reveals that the Ca3NCl3 perovskite is mechanically stable. Moreover, with rising pressure (tensile to compressive), elastic constants, elastic moduli, ductility, machinability index, bulk modulus, shear modulus, pugh's ratio, young modulus and anisotropy all rise. The photovoltaic (PV) performance of novel cell configurations, featuring Ca3NCl3 as an absorber and CdS as an Electron Transport Layer (ETL), was systematically studied using the SCAPS-1D simulator. This structure achieved a maximum power conversion efficiency (PCE) of 20.88 %, with a current density (JSC) of 19.184 mAcm−2, a voltage (VOC) of 1.22 V, and a fill factor (FF) of 89.06. The valuable findings from our simulations will aid in the experimental design of an efficient Ca3NCl3-based new inorganic perovskite solar cell in the near future.

Enhanced Spectrum Resolution of Optical Fiber Refractive Index Sensors Based on Single-Arm Fiber-Optic Tapered Probe

Enhanced Spectrum Resolution of Optical Fiber Refractive Index Sensors Based on Single-Arm Fiber-Optic Tapered Probe

Structural, Optical, and Thermal Properties of PVA/SrTiO3/CNT Polymer Nanocomposites.

Successful preparation of PVA/SrTiO3/CNT polymer nanocomposite films was accomplished via the solution casting method. The structural, optical, and thermal properties of the films were tested by XRD, SEM, FTIR, TGA, and UV-visible spectroscopy. Inclusion of the SrTiO3/CNT nanofillers with a maximum of 1 wt% drastically improved the optical and thermal properties of PVA films. SrTiO3 has a cubic crystal structure, and its average crystal size was found to be 28.75 nm. SEM images showed uniform distribution in the sample with 0.3 wt% of SrTiO3/CNTs in the PVA film, while some agglomerations appeared in the samples of higher SrTiO3/CNT content, i.e., at 0.7 and 1.0 wt%, in the PVA polymer films. The inclusion of SrTiO3/CNTs improved the thermal stability of PVA polymer films. The direct and indirect optical band gaps of the PVA films decreased when increasing the mass of the SrTiO3/CNTs, while the single-oscillator energy (E0) and dispersion energy (Ed) increased. The films' refractive indices were gradually increased upon increasing the nanofillers' weight. In addition, improvements in the optical susceptibility and nonlinear refractive indices' values were also obtained. These films are qualified for optoelectronic applications due to their distinct optical and thermal properties.

Exploring the spectroscopic and I‑V‑T characteristics advancements of cadmium zinc tungsten phosphate diode

This research accomplished the growth of cadmium zinc tungsten phosphate (CZWP) thin films on both glass and p-Si substrates, employing the sol–gel spin coating method. The sol–gel technique offers a versatile and controlled approach for fabricating nanomaterials with tailored properties. The structural and morphological analyses, conducted through XRD and FE-SEM, provided comprehensive insights into the nature of the films. The optical properties, absorbance behavior, energy gap, refractive indices, dielectric, conductivity, and electronegativity, underwent meticulous examination through UV–Vis spectroscopy. The X-ray diffraction analysis of the zinc cadmium tungsten phosphate diode reveals diffraction lines indicative of a nanostructure featuring a monoclinic-phase Zn2P2O7 and Cd3P6O28. Furthermore, SEM analysis confirms a nanoporous morphology with a nanograpes-like structure in the successful crystalline structure of the cadmium zinc tungsten phosphate nanostructure. The optical absorption studies, covering a wavelength range from 190 to 1500 nm, unveiled both direct and indirect energy band gaps, measuring 4.14 and 3.77 eV, respectively. A rigorous analysis of the I-V-T characteristics for the CZNP/p-Si junction in dark mode led to the identification of key parameters, including the transport ideality factor, barrier height, and series resistance.

Study of mechanical, optoelectronic, and thermoelectric properties of Rb2ScAuZ6 (Z = Br, I) for energy harvesting applications

In the current article, the structural, mechanical, optoelectronic, and thermoelectric properties of Rb2ScAuZ6 (Z = Br, I) have been predicted using the density functional theory (DFT) approach. The tolerance factor, phonopy, and formation energy analysis validated the structural, dynamic, and thermodynamic stability of Rb2ScAuBr6 and Rb2ScAuI6, respectively. Likewise, the investigated elastic properties concluded that both materials exhibit mechanical stability and possess ductile characteristics. The directional-dependent elastic moduli revealed the anisotropy features. The indirect bandgaps determined by TB-mBJ approximation are 2.1 eV and 1.6 eV for Rb2ScAuBr6 and Rb2ScAuI6, respectively. Optical absorption, reflectivity, refractive index, and dielectric constants have been assessed in the energy range between 0 and 6 eV to ensure efficient absorption in the visible spectrum. Both materials have appropriate optical parameters for utilization in photovoltaic systems. Further, using the BoltzTraP code, the thermoelectric properties have been calculated to evaluate the thermoelectric efficiency. Both perovskites have lower lattice and electronic thermal conductivity, a higher Seebeck coefficient, and a higher figure of merit, making them ideal candidates for thermoelectric applications.

Crossover from Linear to Quadratic Electro-optic Behavior in BaTiO_{3} and (Ba, Sr)TiO_{3} Solid Solution.

We derive a numerical method based on coupled density functional theory and effective Hamiltonian schemes to calculate the linear and quadratic electro-optic response of ferroelectrics at finite temperature and in different frequency ranges. By applying the developed method to BaTiO_{3}, we successfully resolve apparent discrepancies in the experimental literature that reported a linear or quadratic electro-optic response when visible or terahertz radiation was employed to measure the optical index, respectively. We further demonstrate that (and explain why), in the case of the Ba_{1-x}Sr_{x}TiO_{3} disordered solid solutions, structural phase transitions not only lead to larger linear electro-optic constants, as previously demonstrated in the literature, but also significantly enhance the quadratic electro-optic constants.

A comparative study of ZnO, AZO, TiO2, Sb2O3, and SnO2 nanomaterials coated SPR based fiber optic refractive index sensors for chemical sensing application

This paper presents a comprehensive investigation of Surface Plasmon Resonance (SPR) based fiber optic sensors tailored for precise detection of refractive index (RI) variations in acetone and ethanol solutions. The sensor probe design incorporates a nanostructure comprising a metal layer (Ag, Al, or Cu) and a metal oxide sensing layer (ZnO, AZO, TiO2, Sb2O3, SnO2) over the fiber core. Employing the Transfer Matrix Method (TMM), optimal layer thicknesses were determined, with a combination of 50 nm Ag and 20 nm metal oxide demonstrating maximum sensitivities. The sensor probes were fabricated using the Radio Frequency (RF) sputtering technique, and their uniformity, elemental composition, and optical properties were assessed through Field Emission Scanning Electron Microscope (FESEM) and ellipsometer analyses.The sensor response of the probes is 12 %, 7.1 %, 10.8 %, 6.08 %, and 11.34 % for acetone and 11.9 %, 9.2 %, 12 %, 7.89 %, and 12.48 % for ethanol. Sensitivities ranged from 2.7 nm/v% to 2.84 nm/v% for acetone and 1.90 nm/v% to 3.02 nm/v% for ethanol, with the SnO2-coated probe exhibiting the highest sensitivity. Further sensitivity enhancement was achieved by introducing a bimetal layer (50 nm Ag/5 nm Sb/20 nm SnO2), resulting in a 15 % increase for ethanol compared to the Ag/SnO2-based SPR probe.

Exploration of the optical characteristics in sol-gel synthesized europium-doped zinc oxide thin films for potential optoelectronic use: a comprehensive characterization approach

Abstract In this study, we present our findings on the spin coated pure Zinc-Oxide (ZnO) nanowire arrays and Europium doped ZnO (Eu3+: ZnO) nanostructure thin films. These arrays were grown on soda lime (silica) coated glass substrate. We conducted a comprehensive analysis of the structural and optical properties of the as-synthesized nanostructures. The characterization techniques included x-ray Diffraction, FESEM Analysis, Raman Spectroscopy, Photoluminescence and UV–vis Analysis. The XRD findings indicate the incorporation of Europium (Eu3+) into the ZnO crystalline lattice, potentially replacing Zn2+ ions. This doping with Europium (Eu3+) led to a reduction in crystalline size, as determined by Scherrer’s equation decreasing from 48 nm to 28 nm demonstrates a decrease in defects within the films. Raman Shift analysis revealed changes in the optical properties of films with inclusion of Europium in host matrix. Photoluminescence studies demonstrated a distinctive 5D0 to 7F2 transition arising from the Eu3+ ions, observed at approximately 612 nm. We have thoroughly examined the optical characteristics of both Europium-doped and pure ZnO thin films through a systematic study. The optical properties were assessed by analyzing the absorption spectra (220–600 nm) and transmission spectra within the wavelength range of 200 to 1200 nm. The film exhibited an impressive 80% transparency, particularly noteworthy for window layer application. The refractive index (n), extinction coefficient (k) and all other associated parameters were found to be impacted by the doping of Europium. The refractive index dispersion relation has been explored using a single oscillator model. Furthermore, the non-linear optical susceptibility (χ 3) and non-linear refractive index were computed using semi-empirical relationships based on the linear optical parameters. The Europium (Eu3+) doping in ZnO led to an increase in the χ 3 value elevating it from 4.07 × 10–1° to 5.91 × 10–1° e.s.u. These findings suggest that Europium-doped ZnO nanostructures have the potential to be a promising platform for the development of efficient multispectral light-emitting diodes (LED’s) and optical devices.

Enhanced Efficiency of Silicon Solar Cell by New Salophen Complexes Embedded PMMA as Light Concentrators

The Schiff base N,N-bis(salicylidene)-o-phenylenediamine (salophen) was prepared by the condensation of salicylaldehyde with o-phenylenediamine in ethanol solution. Two new Zn(II) and Ni(II) salophen complexes, were synthesized, fully characterized by infrared (IR), 1H NMR spectroscopic measurements, UV–Vis spectra, photoluminescence (PL), and X-ray diffraction (XRD). The prepared complexes were used as phosphors to fabricate complexes/PMMA slab-based luminescent solar concentrators (LSC). The thermal stability of pure and doped PMMA polymer was examined by differential scanning calorimetry. Various parameters such as the optical energy gap, refractive index, AC and DC conductivity, dielectric constant, dielectric loss, Urbach energy, fluorescence quantum yield, and Stokes shift have been calculated and discussed. Optical absorption is carried out in wavelength region 200–900 nm at room temperature before and after the samples have been exposed to sunlight for up to 8 h. Photodegradation studies showed that the Zn(II) complex/PMMA LSC has the lowest rate of degradation compared with Ni(II) complex/PMMA LSC with the same concentration (0.06% weight). I–V characteristics of the photovoltaic devices with and without collectors were examined. The PV cell coupled with LSC shows an increase in maximum efficiency by about 50% compared to the normal one. This indicates that the proposed technique is very useful for improving the efficiency of solar cells.

Impact of Alpha Rays on the Optoelectronic Properties of Epoxy Resin Thick Films

Irradiated epoxy thick films are important for optical properties and may be used in many optical applications. This study aims to evaluate the effect of alpha irradiation on the optical and structural properties of epoxy thick films. Epoxy resin films were prepared by mixing epoxy resin (A) with hardener (B) at a mixing ratio of 3:1. Thus, specific thick films with thicknesses of 0.7 mm,0.8 mm and 1 mm were manufactured. Using visible and ultraviolet spectroscopy is one of the most important methods for studying polymers band gaps and electrical properties. The absorbance and transmittance spectra were used to investigate the optical properties of epoxy coatings of different thicknesses over a wavelength range of 300 nm–900 nm. Optical properties, such as absorption coefficient, refractive index, extinction coefficient, real dielectric constant, imaginary dielectric and optical band gap, were measured. The results show that the epoxy thick films have good optical transparency in the low-wavelength region. The results showed that increasing the thickness of the resin films decreased the optical energy gap and refractive index while increasing the absorption and extinction coefficients. In comparison, the effect of irradiation on an epoxy film of thickness 1 mm leads to an increase in the transmittance spectrum and energy gap and a decrease in the optical constants. The Fourier-transform infrared (FTIR) spectrum of the films was examined and showed the types of chemical bonds of the epoxy films before and after irradiation.