Optical Parameters Research Articles

Optical, Mechanical and Dielectric Characterization of 5-(3,4,5-Trimethoxybenzyl) Pyrimidine-2,4-Diamine (Trimethoprim- An Antibiotic Drug) Single Crystal

Objectives: To evaluate the optical properties of the trimethoprim (TMP) single crystal. Methods: 5-(3, 4, 5- trimethoxybenzyl) pyrimidine-2-4-diamine known as trimethoprim (TMP), a single crystal is a well-known antibiotic drug, was grown by the slow evaporation method. Findings: The TMP unit cell parameters were confirmed by single crystal X-ray diffraction. Functional groups of TMP crystal was confirmed by Fourier transform infrared spectral analysis. The optical spectrum shows the wide transparency window of TMP which is the prerequisite for NLO material. The band gap is calculated as 4.10 eV from Tauc’s plot. The various optical constants like extinction coefficient, refractive index and reflectance were calculated from the transmittance spectrum data. The optical and electrical parameters like optical conductivity, electrical conductivity and susceptibility of the single crystal of TMP were determined from the UV spectrum. The fluorescence spectrum shows the presence of a sharp intense peak at 690 nm indicates red emission and a weak peak observed at 480 nm indicates blue emission. The Vickers hardness study shows the grown crystal belongs to the soft type single crystal with Meyer’s index (n) of 2. The yield strength of the crystal was calculated. Dielectric constant and dielectric loss are measured as a function of frequency. The laser damage threshold of the TMP crystal was measured using an Nd: YAG laser with a wavelength of 1064 nm. Novelty: The various studies show that the TMP crystal possesses excellent optical properties and can be used for opto-electronics device fabrication. Keywords: Unit cell, Transmittance, Emission, Hardness, Dielectric constant and loss

Investigation of structural, electronic, and optical properties of halide perovskites with different amide cations: A first-principles approach

Hybrid halide perovskites (CH3NH3PbI3) have emerged as an appealing candidate in photovoltaic devices due to their low-cost fabrication and remarkable optical and electronic properties. However, the commercial applications of these perovskites are limited by their instability due to the rapid rotation and orientation of methylammonium cation (CH3NH3+), and interaction with PbI2 lattice at high temperatures. Since CH3NH3+ can deteriorate structural stability of MAPbI3 perovskites, it is possible to use molecular cation design and substitution as a mechanism to enhance the stability and remove this limitation. We here investigate the effect of replacing this cation with other organic cations (HCOHNH2PbI3 (FPbI3), CH3COHNH2PbI3 (AcPbI3), and NH2COHNH2PbI3 (UPbI3)) in order to enhance the performance of the perovskites, while also keeping the band gap energy (Eg) in an appropriate range for solar cell applications. The calculations are performed using the full potential linearized augmented plane wave method, providing lattice parameters and the formation energy of the proposed perovskites. Our results indicate that AcPbI3 perovskite outperforms the other structures in terms of various optical parameters, such as the absorption coefficient, optical conductivity, and reflectance. The optical and electronic band gaps of the AcPbI3 structure and its resonance form (Ac'PbI3) are found to be in agreement with each other, proposing them as optically tunable hybrid perovskites in emerging solar cells.

Unveiling the structural and optoelectronic properties of (P, Bi, Sb)-doped GaAs by first- principles calculations

In this work, we investigate the influence of M substitutions (M = P, Bi, and Sb) on the structural, electronic, and optical properties of gallium arsenide, GaM x As1-x for x=0,0.25,0.50,0.75,1.0 using density functional theory (DFT). We have observed that the cubic symmetry of the semiconductors in conserved, and lattice constants show a linear behavior with dopant concentration, according to Vegard’s law. Specifically, the lattice constants increased for Bi and Sb dopants, whilst decreased for P dopants. Furthermore, the bulk modulus decreased with an increase in M-concentration for all M-doped systems. The energy analysis showed that the P-doped system was the most stable system. In terms of the electronic band structure, all M-doped compounds exhibited a direct electronic band gap. The P-doped system showed a wide band gap, while the Sb-doped systems displayed a narrow band gap, both compared to pristine GaAs. The Bi-doped system showed metallic-like behavior. To gain insights into the linear optical properties of the GaM x As1-x compounds, we calculated the real and imaginary parts of the dielectric function, as well as other optical parameters such as the absorption coefficient, refractive index, extinction coefficient, and reflectivity. The results showed that P doping leads to a blue-shift in the optical absorption coefficient, while Bi and Sb doping lead to a red-shift. These findings provide valuable theoretical insights for the potential application of GaM x As1-x semiconductors in photovoltaics and optoelectronic devices.

Ultraviolet active novel chalcogenides AScSe2 (A= K, Cs): The structural, optoelectronic, mechanical, vibrational, and thermodynamical properties for energy harvesting applications

It is essential nowadays to investigate some unique and appropriate materials for optoelectronic applications. We deliberate here for the first time, the structural, optoelectronic, mechanical, vibrational, and thermodynamical properties of hexagonal structured selenium-based ternary chalcogenides AScSe2 (A = K, Cs) by using Perdew-Burke-Ernzerhof Generalized-Gradient-Approximation (PBE-GGA). The lattice angles for these materials are found as α = β = 90° and γ = 120°. KScSe2 is optimized with lattice parameters a = b = 4.3 (Å), c = 7.81 (Å) whereas, CsScSe2 is relaxed at a = b = 4.43 (Å) and c = 8.51 (Å). The hybrid Heyd-Scuseria-Ernzerhof (HSE06) functional overestimates the lattice parameters to the extent that for KScSe2 these are found as a = b = 4.92 (Å), c = 7.10 (Å) and for CsScSe2 a = b = 5.15 (Å), c = 7.09 (Å). The energy band gap confirms the semiconducting nature of these materials. Born's criteria endorses the mechanical stability of these materials. Moreover, the temperature dependence of thermodynamic potentials and specific heat at constant volume is also determined using the harmonic approximation. The negative value of free energy ensures their thermodynamical stability. The vibrational modes are calculated by plotting the phonon dispersion and the vibrational density of states (VDOS) where infrared (IR) and Raman spectroscopy are used to characterize the vibrational modes. The optical parameters are examined at a smearing value of 0.5 eV that portray good absorptivity of the incident light from the Ultraviolet (UV) region. Thus, these materials may be potential ones to be utilized for energy harvesting applications via photovoltaic.

Influence of ZnMn2O4/CuCo2O4 nano-fillers on the optical and electrical properties PVA/CMC/PEG blended polymers

(1-x)ZnMn2O4/xCuCo2O4 samples were synthesized by the co-precipitation method while polyvinyl alcohol/carboxymethyl cellulose/polyethylene glycol (PVA/CMC/PEG) blended polymer were fabricated by the casting method. Rietveld refinement analysis was used to determine the crystallite size and phase percentages for each composition were determined for all samples. The morphology and structure of PVA/CMC/PEG/(1-x)ZnMn2O4/xCuCo2O4 blends were examined using scanning electron microscopy and x-ray diffraction techniques. The reflectance and transmittance spectra were examined for blended polymers using a diffused reflectance spectrophotometer. Using LCR meter, the prepared blend films' dielectric properties were evaluated. When the blend is loaded with 0.9ZnMn2O4/0.1CuCo2O4, the lowest transmittance values (29–47 %) in the visible region are reached. As the CuCo2O4 doping levels became 10 % in the filler, the smallest direct and indirect energy gap values of 5.4 and (4.47, 1.9, 1.65) eV were attained, respectively. The linear and nonlinear optical parameters affected by the amount of CuCo2O4 in the filler samples. The optical conductivity of the doped blend reached its maximum value at x = 0.15. The CIE chromaticity diagrams revealed that the blends have varying degrees of blue color. The addition of (1-x)ZnMn2O4/xCuCo2O4 fillers improves the energy storage capability of the blends without raising the energy dissipation. The highest value of AC conductivity was achieved with the blend containing 0.9ZnMn2O4/0.1CuCo2O4. Nyquist plot revealed that the ionic conductivity increased as a result of doping. The obtained results suggest that the doped PVA/CMC/PEG/(1-x)ZnMn2O4/xCuCo2O4 blends might be used in a variety of industrial applications, including solar cell technology.

Investigation of structural, morphological, optical and electronic properties of Cu-doped PbS thin films: a comparative experimental and theoretical study

Thin film technology has emerged as a cornerstone in optoelectronics, enabling the fabrication of compact, lightweight devices with enhanced performance and efficiency through precise control of the nanoscale thicknesses of functional materials. The current study explores the impact of copper (Cu) doping (3.125%, 6.25%, and 12.5%) on lead (Pb) sites in PbS to examine the structural, morphological, electronic, optical, and thermoelectric characteristics, employing both experimental and theoretical approaches. Polycrystalline thin films of PbS are deposited by spin coating technique on glass substrates. The XRD study discloses the cubic crystal structure of pristine and Cu-doped PbS with nominal variation in d-spacing. Surface morphological investigations reveal that Cu-doping transforms the coffee beans like grains to nanoplates that significantly affect the surface homogeneity and porosity. The tuning of band structure in the visible range, 1.64–2.21 eV is witnessed in the band structure analysis. Moreover, the experimental results are complemented by a theoretical study using WIEN2k software. Theoretical study exhibits the direct bandgap nature and with the incorporation of Cu, it increases from 0.89 to 2.11 eV. The density of states spectra for Cu-doped PbS exhibits strong hybridization between p-states of Pb and S, and d-states of Cu. Optical findings demonstrate significant variations in the absorption spectrum, which result in modifications in the optical energy band gap and peculiar optical parameters of doped samples. At room temperature, the increase in electrical conductivity (σ/τ) from 0.2 × 1020 (Ω.m.s)−1 for PbS to 0.3 × 1020, 3.1 × 1020 and 7.8 × 1020 (Ω.m.s)−1, thermal conductivity from 0.25 × 1014 W m.K.s−1 to 0.30 × 1014, 2.4 × 1014 and 5.2 × 1014 W m.K.s−1 and decrease in Seebeck coefficient from 72 to 35, 13 and 8 μV/K with the inclusion of Cu up to 3.125, 6.25 and 12.5% offer the potential for advancing thermoelectric technology. This could lead to improved efficiency and practical utilization in energy harvesting and waste heat recovery.

Linear and nonlinear optical studies on successfully mixed vanadium oxide and zinc oxide nanoparticles synthesized by sol–gel technique

Abstract In this study, V2O5, 5ZnO/10V2O5, and ZnO, 10ZnO/10V2O5 nanocomposites were synthesized by the sol–gel method. The sol–gel technique is an important process for the fabrication of advanced oxide materials with desirable catalytic, optical, and structural properties. The varieties and flexibilities of sol–gel techniques help in preparing materials with extremely specific properties. For the presented samples, three types of phases were assessed. The average crystalline size of V2O5, 5ZnO/10V2O5 and ZnO, 10ZnO/10V2O5 nanocomposites were found to be 25, 26, 14.5, and 15.5 nm, respectively. SEM images showed three different shapes of semi-tube, semi-spherical, and semi-flower. The pure samples of V2O5 and ZnO showed semi-tube shapes. 5ZnO/10V2O5 shows a spherical shape with average dimeter of 0.6 µm. Strong dependence of the direct optical band gap was observed on different compositions that varied within the range of (2.33–2.73 eV). Conversely, the indirect values varied within the range of 2.119–2.35 eV. On the other hand, 10ZnO/10V2O5 has semi flower shape with different layers. Optical parameters, such as optical band gap, extension coefficient, tails of localized states, and refractive index, were gauged for these nanocomposites. In addition, the mean refractive index of ZnO is lower than that of V2O5, with differences observed between 5ZnO/10V2O5 and 10ZnO/10V2O5 nanocomposites.

Theoretical study of optoelectronic, elastic and mechanical properties of gallium modified barium titanate (Ba1-xGaxTiO3) perovskite ceramics by DFT

In this report, we study the gallium modified Barium titanate (Ga-BTO) Ba1-xGaxTiO3 with (x = 50 %) perovskite ceramics, which have not been synthesized experimentally to date. The density functional theory-based full potential linear augmented plane wave has been employed to determine the optoelectronic, elastic, and mechanical properties of pure and modified BaTiO3. Completely relaxed 2 × 2× 2 of primitive five atoms’ cells has been used for calculations. A large cut-off energy of 120 Ry has been used to eliminate the basics of plane wave-indicating wave functions. The influence of substitution of Ga on electronic structure and optical parameters such as reflectivity, refractivity, dielectric function, optical conductivity, extinction, and absorption coefficients are analyzed and elucidated with TDOS and PDOS. The Ga modified BTO manifests a forbidden energy gap of 1.84 eV. The static dielectric constant Ɛ1(o) has values of 8.8 and 100 for pure and modified compounds respectively. Ga dopant improved the polarizing power of BTO and for the doped BTO imaginary part, Ɛ2(ω)showed a prominent peak located at 3.9 eV. The optical properties show that perovskite compound substituted with Ga is a good absorber in the ultraviolet region and the modified material has a small value of reflectivity and static refractive index 12.2. The general profiles of optical spectra of modified BaTiO3 display highly desirable features like the prominent peaks of optical conductivity obtained at 4.2 and 5.8 eV for modified BTO that make it a promising candidate for optoelectronic and spintronics. Ga-modified BTO has higher ductility, modulus (169.96 GPa), and anisotropy (2.949) than pure BTO found by analyzing their elastic and mechanical properties.

Exploring relationships among landfill leachate parameters through multivariate analysis for monitoring purposes.

Elucidating the properties of landfill leachate and the relationships among leachate parameters is crucial for efforts to determine appropriate landfill leachate monitoring activity and management strategies. This study investigated the physical, chemical and optical parameters of leachate in an old Japanese landfill over a 13-month period. The parameters were explored based on their relationships with the maximum fluorescence (Fmax) of three components (microbial humic-like C1, terrestrial humic-like C2 and protein-like C3) deconvoluted from excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis. Dissolved organic carbon (DOC), chemical oxygen demand (COD), Cl- and SO42- concentrations and pH ranged from 2.6 to 38.2 mg C L-1, 9 to 324 mg L-1, 14 to 972 mg L-1, 26 to 1554 mg L-1 and 6.9 to 11.6, respectively. Linear regression analysis suggested that the Fmax values of C2 and C3 represented DOC, whereas the Fmax value of C2 alone could serve as a COD indicator. Hierarchical cluster analysis and principal component analysis were employed to successfully categorise leachate samples based on their locations. Higher dissolved organic matter levels were observed in leachate within the old disposal area, whereas elevated levels of inorganic components such as SO42- and Cl- were found in leachate collected from the extended disposal area and at a treatment facility. Statistical analysis provides crucial tools for assessing and managing various areas of a landfill, supporting targeted and effective waste management strategies.

Elastic Moduli, and Estimations of Some Physical, Thermal, and Optical Parameters of Ge-Se-As Glassy Systems with Improved Mechanical Strength

Employing the melt quench approach, glassy systems with the chemical composition Ge30Se(70-x)Asx have been synthesized. As the amount of arsenic increases, various physical, mechanical, thermal, optical parameters and some other aspects of elastic moduli have been assessed. The XRD pattern shows the amorphous characteristics of the inspected materials. The density of the glasses increases from 4.32 to 4.61 g-cm-3 whereas the molar volume declines from 19.32 to 18.62 cm3 mol-1 as the concentration of arsenic increases. The measured values of the ultrasonic velocities have been used to measure the elastic properties, such as the Shear, and longitudinal strains, Bulk modulus, Young's modulus, and Poisson's ratio of the synthesized glasses. The upsurge in the values of elastic moduli indicated the upgrading in the elastic properties of the materials. The outcomes are interpreted in terms of a profound structural change brought about by molecular rearrangement, which regulates the glass’s physical characteristics. The optical band gap energies are found to decrease from 2.17 to 1.86 eV due to the increase in Urbach energies from 040 to 0.64 eV with the incorporation of arsenic atom. The obtained results indicate the perspective of the as-synthesized thermally stable materials to be used in optoelectronic devices.

Exploring the optical and electrical features of PVA/CMC/PPy/MWCNTs blended polymers

The objective of this study is to create nanocomposite films using polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (CMC), polypyrrole (PPy) and Multi-walled carbon nanotubes (MWCNTs). These nanocomposites show potential for use in a range of optoelectronics devices. The structure and morphology of PVA/CMC/PPy/x wt % MWCNTs blends were explored using X-ray diffraction and scanning electron microscope techniques. In the visible range, the transmittance lowered from 78 to 87 % (PVA/CMC/PPy blend) to 3–5 % (x = 0.25 wt % MWCNTs). The transmittance in the UV range decreased significantly, approaching zero, for the blend containing 0.25 wt % MWCNTs. The material improves the absorption of UV–visible light and efficiently prevents the penetration of UV–visible light. When the concentration of MWCNTs reached 0.05 in the doped blend, the reflectance value improved considerably. The addition of MWCNTs to the PVA/CMC/PPy composite leads to a reduction in the optical bandgap values. The lowest direct and indirect band gaps are (4.98, 4.36) eV and (4.52, 3.19, 2.68, 1.18) eV, respectively, accomplished when the MWCNTs content was 0.2 wt %. A blend containing 0.15 wt % MWCNTs resulted in the highest values of refractive index and nonlinear optical parameters. In the visible light spectrum, the blend with 0.25 wt% MWCNTs had the best optical conductivity values. Doped blends can be used in optoelectronic or photocatalytic applications depended on the amount of MWCNTs doped. The current-voltage characteristics and logarithm of the current density and square root of the electric field strength of PVA/CMC/PPy/x wt % MWCNTs blended polymers at various temperatures were investigated.

Profiling of particulate matter transport flux based on dual-wavelength lidar and ensemble learning algorithm.

Transport flux (TF) is a significant particulate matter (PM) characteristic. This paper introduces an advanced dual-wavelength polarization aerosol and wind lidar (Wind Flux 3000) capable of independently observing the PM TF. The PM TF observation capability, which allows for simultaneous aerosol and wind measurements, was achieved by integrating a Mie-polarization particle lidar module and a coherent Doppler wind lidar module into a single lidar system. The primary measurement products of the Wind Flux 3000 include particulate extinction coefficient at 532 nm and 1550 nm, volume linear depolarization ratio at 532 nm (δp,532), wind speed (WS), wind direction (WD), vertical speed (VS), turbulence intensity (TI) and mixing layer height (MLH), retrieved by physical and proven algorithms. The PM concentration scales with the measured optical parameters and is also impacted by other environmental or meteorological parameters. Under the framework of the potential relationship between the PM concentration and the above parameters, the PM2.5 and PM10 concentration retrieval models were established using the stacking method of the ensemble learning technique; the models were trained using the in-situ data as true values, while the signal-to-noise ratio (SNR) at 1550 nm, δp,532, WS, WD, VS, the standard deviation of VS, TI, MLH provided by the Wind Flux 3000, as well as the relative humidity and temperature from ERA5, the hours of the day, and a "dust day" flag were used as inputs. The R2, RMSE, and MAE for the comparison between the predicted and true values of the PM2.5 test set are 0.857, 13.52 µg · m- 3, 9.16 µg · m- 3, and those of the PM10 test set are 0.926, 24.75 µg · m- 3, 14.39 µg · m- 3, respectively. The performance of the PM2.5 and PM10 concentration retrieval ensemble models is better than that of individual machine learning algorithms and better than that of the linear model. On 15th March 2023, a strong southeastward dust transport process with dust plume deposition was observed at Qingdao by the Wind Flux 3000. The analyses of the dust event demonstrated the Wind Flux 3000's ability to evaluate the transports of PM quantitatively.

The role of Bi incorporation on the optical dispersion parameters of binary Se–In chalcogenide glass films as encouraging materials for photovoltaic implementations

The bulk form of Se78In(22-x)Bix (x = 0, 4, 8, and 12 at.%) was produced with melt-quench technology. Subsequently, thin films of these compositions were produced through the thermal evaporation method under vacuum conditions. Analysis via diffraction of X-rays confirmed the disordered character of the resulting films. The refractive index (n) and extinction coefficient (k) were computed using optical transmission T(λ) and reflection R(λ) data. Analysis of optical constants revealed that the optical energy gap Egopt decreases while the Urbach tail Eu augments as the Bi content increases. Other related constants were determined and investigated in relation to variations in Bi content. The outcomes of our study were compared with those published previously. Non-linear parameters were calculated and discussed for the investigated films.

Longitudinal changes of funduscopic optic disc size, color and cup-to-disc ratio in school children

BackgroundTo investigate the relationship between changes in the optic disc size and color, cup-to-disc (C/D) ratio, and axial elongation in schoolchildren.MethodsA prospective cohort study was performed in 75 right eyes of elementary school students for six years (from 8.5 to 14.5 years old). In the first and last year, all participants underwent optical axial length measurement and color fundus photography. The optic disc color was calculated by dividing the intensity of red by the sum of the intensity of red, green, and blue. The optic disc area was calculated by modifying the number of pixels according to Bennett’s formula. The C/D ratio was calculated by dividing the vertical cup diameter by vertical optic disc diameter. Wilcoxon signed rank test was used to compare these optic disc parameters and axial length in the first and last year.ResultsMean axial length in the last year (24.82 mm) was significantly longer than that in the first year (23.34 mm). Likewise, the mean optic disc size was significantly smaller in the last year (41,946 pixels) than that in the first year (46,144 pixels). The mean optic disc color in the last year (0.49) was significantly more reddish than that in the first year (0.46), while the mean C/D ratio in last year (0.50) was significantly smaller than that in first year (0.52).ConclusionsDuring the period from 8.5 years to 14.5 years of age, both the optic disc size and C/D ratio became smaller, while the color became more red.

Structural, optical, and morphological evaluation of PVA/Bi-Ni oxide-rGO nanocomposite casted films for optical devices applications

Herein, the polyvinyl alcohol (PVA) films doped with various concentrations of Bi2O3-NiO-rGO (BNG) nanoparticles were prepared through casting method. BNG nanoparticles were synthesized first using the co-precipitation method and then loaded into the polymer matrix. Various techniques like X-ray diffraction, Raman spectroscopy, and optical microscopes were used to determine the PVA’s structure after BNG nanoparticle additives. The thermal stability of the PVA’s film after the additive BNG nanoparticles was examined using the DSC technique. Furthermore, the optical parameters including bandgap energy (Eg), Urbach energy (EU), refractive index (n), optical conductivity, and optical dielectric constants were investigated via the absorbance and transmission data recorded using UV-visible spectroscopy. In addition, the photoemission spectra of the PVA matrix were determined after the inclusion of BNG nanoparticles. The Eg value decreases from 5.57 eV to 3.94 eV and from 4.8 eV to about 1.98 eV for direct and indirect transitions, respectively. While the EU value increases from 0.39 eV for pure PVA to about 3.23 eV for PVA: 4%BNG. The refractive index grows with the insertion of BNG to the PVA from 1.387 for pure PVA to about 5.157 for PVA: 4%BNG, which is a good suggestion for optical glasses applications. In addition, the increase in optical dielectric constants and optical conductivity with rising the BNG nanoparticle concentrations in the PVA matrix was confirmed. Such enhancement suggests the use of prepared samples in optical device applications.

Choroidal Vascularity Index and Subfoveal Choroidal Thickness in Rheumatoid Arthritis Assessed with Enhanced-Depth Imaging Optical Coherence Tomography

ABSTRACT Purpose To evaluate the effects of rheumatoid arthritis (RA) on choroidal vascularity index (CVI) and subfoveal choroidal thickness (SFCT). Methods The study included 56 eyes of 56 rheumatoid arthritis patients and 65 eyes of 65 age- and sex-matched healthy normal participants. CVIs of all participants were measured by transferring enhanced depth imaging optical coherence tomography (EDI-OCT) images to the image J program that is software used for image binarization and compared between the 2 groups. SFCT, central macular thickness (CMT) and optic disc parameters of all participants were measured with spectral domain OCT and compared. Results The mean CVI values of the RA and control groups were 65.9 ± 1.52 and 68.56 ± 1.62, respectively, and were significantly lower in the RA group (p = 0.001). Mean SFCT values of the RA and control groups were 290.11 ± 15.18 and 332.88 ± 11.04, respectively, and SFCT was significantly lower in the RA group (p = 0.001). RA patients have thin SFCT and low CVI. There was no significant difference between the two groups in terms of CMT and optic disc parameters. Conclusion RA patients have lower CVI and thinner SFCT than healthy participants.

Structural, optical and electrical conduction characteristics of PMMA/PVAc/TBAI blended polymers

This study aims to create tetra-n-butylammonium iodide (TBAI) doped poly(methyl methacrylate) (PMMA)/polyvinyl acetate (PVAc) blended polymers for utilize in a diversity of optoelectronic applications. By the casting technique, the films of (PMMA/PVAc/x wt % TBAI) were formed. The structure and morphology characteristics of the blended materials were studied using X-ray diffraction and scanning electron microscopy techniques. The optical transmittance declined to a minimum value when the blend was loaded with 38 wt % TBAI. The blend containing 38 % TBAI exhibits the highest reflectance values in the visible range. The lowest direct optical bandgap energies (4.20 eV) and indirect optical bandgap energies (3.71 eV, 3.13 eV) were achieved when TBAI reached 38 wt%. The addition of TBAI leads to an enhancement of the refractive index values of PMMA/PVAc in the visible spectrum. The effect of TBAI doping amount on the optical dielectric constant, energy loss functions, optical conductivity, nonlinear optical parameters and emitted color of the host blend was explored. The maximum values of the optical dielectric constant and energy loss functions were achieved after the TBAI level reached 38 wt%. The three non-linear optical (NLO) parameters for PMMA/PVAc blended polymers were enhanced as the amount of TBAI increased. An increase in voltage (V) or temperature results in a significant increase in electric current (I). Raising the amount of TBAI doping also caused the electric current to rise irregularly, with the exception of the blend with x = 11 %, where it fell. The samples exhibited the non-ohmic characteristics of the current-voltage (I–V) properties. The conduction mechanism of all blended materials was studied in detail. Finally, the outcomes supported the optical and electric properties studies, which suggested that a range of nanoelectronics applications could make use of the PMMA/PVAc/x weight percent TBAI blended polymers.

Crop yield estimation at different growing stages using a synergy of SAR and optical remote sensing data

Crop yield forecasting is an essential component of crop production assessment, impacting people at the global scale down to the level of individual farms. Until now, yield forecasting has predominantly relied on optical data, particularly the maximum value of vegetation indexes. However, this approach only presents a short forecasting window, and it is essential to obtain yield estimates as early as possible in the growing season and then further improve forecasting even after the vegetation index has reached its peak. So far, optical satellite data at high-temporal resolution (1–3 days) has been actively used for real time crop yield monitoring, whereas fewer operational models make a use of synthetic aperture radar (SAR). In this study, we explore whether SAR data can capture distinct aspects of crop dynamics, providing new insights for yield estimation depending on the crop's phenological stage. We assess the efficiency of dual- (Sentinel-1) and quad-polarimetric (UAVSAR, RADARSAT-2) data to explain inter-field crop yield variability for corn, soybean, and rice over a test area in Arkansas, US (258 fields, 2019). We used optical imagery acquired by Planet/Dove-Classic, Sentinel-2, and Landsat 8, to establish a baseline performance of satellite-based indicators to explain yield variability and assess dual- and quad-polarimetric SAR data for crop yield assessment. In terms of polarimetric indexes, the results showed that in general the results for rice were mostly stable and better than the other crops (R2adj ∼ 0.4 on average). The best results were obtained for the Sentinel-1 VHasc with R2adj = 0.47 and RADARSAT-2 phase difference with R2adj = 0.45. The results for corn performed the least with an R2adj <0.35 for all the indexes. The results for soybeans were more variable and were highly correlated with certain indicators such as RADARSAT-2 HV, RADARSAT-2 Volume, and RADARSAT-2 Pauli HV with R2adj>0.4. We also investigated the day of year (DOY) with the maximum correlation between optical and SAR-derived features and the final yields for corn, soybean, and rice. The maximum correlation for optical features occurs over a short time between DOY 155 (June 4) and 185 (July 5) for corn and rice, and DOY 190 (July 9) and DOY 211 (July 30) for soybean, with these results being consistent across various optical-based sensors. On the contrary, the maximum correlation for SAR-derived features varied significantly and was between DOY 120 (April 30) to DOY 225 (August 13). A study of the time series parameters cross-correlation showed that the optical parameters were highly correlated, but the SAR parameters showed strong temporal decorrelation. We conducted a comparison between C-band and L-band to assess their sensitivity at each stage of growth. In this experiment, we determined that for low vegetation, the C band will be more useful at the beginning of the growth cycle, while the L band provides more information in later stages of growth. Using a random forest regression model combining SAR parameters with common difference vegetation index (DVI), we improved the error by 50% in comparison to the error using the (DVI) for corn, soybean, and rice.

Morphology Characterization and Refractive Index Analysis of Subsurface Ultrashort‐Pulsed Laser Modifications in ZnS

A parameter study of ultrashort pulse laser‐induced modifications in the bulk of ZnS crystals is reported. Experimental results on these modifications and their dependence on the pulse energy, writing speed, and depth are presented, with an emphasis on cross‐sectional morphology and induced refractive index changes. Localized permanent material modifications have been inscribed in the bulk of the crystal using a laser with a center emission wavelength of 2.09 μm and a pulse duration of ≈4 ps. The morphology strongly depends on the laser and optical focusing parameters, in particular, on the pulse energy and processing speed, with a significant shift in depth dependence for short pulse‐to‐pulse separations. Depending on the applied pulse energy, distortions of the lateral profile of the refractive index changes appear in the form of oscillatory features in the transverse plane relative to the inducing laser beam. The true extent of the modified material is revealed by the alternating lateral profile with largest induced negative refractive index change, Δn, of −3.88 × 10−2 ± 0.18. Such parametric insight is of critical importance for the understanding and optimization of the fabrication process and for realizing compact 3D photonic devices in the bulk of materials in a reproducible manner.

Coupled twiss parameters estimation from turn-by-turn data

Linear optics parameters are often estimated using turn-by-turn (TbT) data. In-plane beta functions, which are the most common measurement objectives, can be estimated from the amplitudes or phases of TbT data, providing an overall characterization of the linear lattice. In addition to estimating uncoupled Twiss parameters, TbT data can also be utilized for characterizing coupled linear motion. We investigate several methods for constructing a full normalization matrix at each beam position monitor (BPM). BPMs provide information on beam centroid transverse coordinates, but direct observation of transverse momenta is not available. To estimate momenta, one can use a pair of BPMs or fit data obtained from several BPMs. By using both coordinates and momenta, it is possible to fit the one-turn matrix (or its power) at each BPM, allowing for the computation of coupled Twiss parameters. Another approach involves the minimization of side peak amplitudes in the spectrum of normalized complex coordinates. Similarly, the normalization matrix can be estimated by fitting linear coupled invariants. In this study, we derive and utilize a special form of the normalization matrix, which remains non-singular in the zero coupling limit. Coupled Twiss parameters can be obtained from the normalization matrix. The paper presents the results of applying and comparing these methods to both modeled and measured VEPP-4M TbT data, demonstrating effective estimation of coupled Twiss parameters.