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Proper derivation of CH3NH3PbX3 (MAPbX3; where X = Cl−, Br−, I−) optical constants is a critical step toward the development of high‐performance perovskite devices. To date, the optical dispersions at all wavelengths have been inconsistently characterized by under‐approximating or omitting anomalous spectral features. Herein, a rigorous optical dispersion data analysis of single‐crystal MAPbBr3 involving variable‐angle spectroscopic ellipsometry data appended with transmission intensity data is presented. This approach yields a more robust derivation of the refractive index and extinction coefficient for both anomalous (absorptance) and normal (no absorptance) optical dispersion regimes. Using the derived optical constants, illustrative modeled perovskite solar cell device designs are presented in relation to nonrealistic designs prepared using representative optical constants reported in the literature. In comparison, the derived optical constants enables the modeling of layer thicknesses to maximize absorption by the active layer (MAPbBr3) and minimize parasitic optical absorptance by the nonactive layers at broad angles of incidence (≈0°–70°). This robust derivation of MAPbBr3 optical constants is expected to impact the optical dispersion data analysis of all perovskite analogs and expedite targeted development of, for example, solar cell, light‐emitting diode, photo‐ and X‐ray/γ‐ray detector, and laser system technologies. [ABSTRACT FROM AUTHOR]

Ni-doped molybdenum disulfide (MoS 2) powders at 1%, 2%, 3%, 4%, 5% and 7% of Ni are prepared by the hydrothermal method. Sophisticated analytical studies such as X-ray diffraction, Raman, TEM and photoluminescence (PL) were analyzed to predict their structural, morphological and optical properties. Effects of Ni-doping with MoS2 on crystalline structure, morphology as well their optical phenomenon were examined in detail. Ni doping on MoS2 revealed tetragonal crystal structure of the parent compound. A significant decrease in their optical energy gap (from 1.86 to 1.76 eV) was perceived with Ni doping concentration increment. PL intensity exhibited a considerable improvement with Ni-doped MoS2 samples at room temperature. From a theoretical viewpoint, the compact density matrix method is applied for Ni–MoS2 to calculate their linear and nonlinear absorption coefficients as well as refractive index modulations for undoped and Ni-doped samples at the focal points of their corresponding intra-band and inter-band transitions. Observed findings are well correlated with the practical results which prove that Ni–MoS2 layers are promoters for potential applications in optoelectronic technology. [ABSTRACT FROM AUTHOR]

This study demonstrates the use of computational methods to simulate the molecular dynamics involved in hemoglobin concentration sensing, utilizing Material Studio and the TCAD Silvaco device simulator. A non-invasive and flexible Graphene/MoS2 heterostructure has been proposed for sensing hemoglobin concentration in blood samples. The findings reveal a notable shift in the wavelength-dependent refractive index and extinction coefficient, as well as significant changes in the absorption coefficient and reflectivity of the Graphene/MoS2 heterostructure in response to different hemoglobin concentrations, specifically within an approximate range of 0.3 μm to 1 μm. Moreover, the spectral response of the heterostructure demonstrates that at a particular wavelength of approximately 600 nm, a maximum response is obtained. This wavelength can be considered optimal for detecting various levels of hemoglobin using this heterostructure. The anticipated outcome is a comprehensive understanding of the fundamental principles, ultimately resulting in the development of an exceptionally sensitive platform for detecting hemoglobin concentration. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the optical properties of ZnSe/ZnS non-concentric core–shell quantum dots (CSQDs). The numerical method used in this work is based on a combination of coordinate transformation and finite difference method (FDM) to solve the three dimensions of the Schrödinger equation. The optical properties are obtained using the compact density matrix formalism. The influence of different dimensions of the non-concentric CSQD, the position of a core material and the effect of different values of the incident optical intensity I on the optical properties of the CSQD are investigated. The results obtained indicate that the oscillator strength, absorption coefficient and refractive index changes are strongly dependent on the size of the CSQD. The magnitude of both the total absorption coefficient and the refractive index decreased as the incident optical intensity increased. In addition, the resonance peaks for the absorption coefficient and refractive index changes shift towards higher energies when we move from concentric to non-concentric core–shell quantum dots. [ABSTRACT FROM AUTHOR]

Electronic and optical properties of an exciton in the ZnSe/CdSe/ZnSe quantum well are investigated using the Razavy and Pöschl -Teller confined potentials. The theoretical investigations on exciton binding energy, oscillator strength, radiative lifetime, absorption coefficient and changes of refractive index are focused on the structural parameters of these two potentials. They are carried out using variational method and the matrix density approach. Out of two structural parameters (A and M) in the Razavy potential, M is found to be much more effective than A, similarly, λ parameter is more effective than the other parameter χ in Pöschl-Teller potential. The single quantum well becomes double quantum well when the value of A is less than the value of M. The potential asymmetry is developed if the structural parameters are altered. Further, the optical properties are strongly affected by the geometrical size, changes in the structure and the associated structural parameters. It leads to alter the optical properties drastically in the quantum well. The results are compared with the available literature and we hope that they can be used for the design of potentials for the future opto-electronic devices. [ABSTRACT FROM AUTHOR]

The compound NaBi(MoO4)2 has garnered significant interest in optoelectronic fields. This study employs spectroscopic ellipsometry to thoroughly examine the linear and nonlinear optical characteristics of NaBi(MoO4)2 crystals, offering detailed insights into their optical behavior. Our investigation presents a precise method for discerning the crystal's spectral features, revealing the spectral variations of key optical parameters such as refractive index, extinction coefficient, dielectric function, and absorption coefficient within the 1.2-5.0 eV range. Through analysis, we determined optical attributes including bandgap energy, critical point energy, and single oscillator parameters. Additionally, we explored the nonlinear optical properties of NaBi(MoO4)2, unveiling potential applications such as optoelectronic devices, frequency conversion, and optical sensors. This study enhances comprehension of optical properties of NaBi(MoO4)2, underscoring its significance in future optical and electronic advancements. [ABSTRACT FROM AUTHOR]

In this study, the optical properties of porous silicon (PSi), such as the dielectric function, absorption coefficient, bandgap, reflectivity and refractive index, were studied as a function of porosities ranging from 3% to about 40% by using a supercell model in an ab-initio pseudo-potential plane wave (PP-PW) method based on density functional theory (DFT). To validate these theoretical results, various PSi samples were prepared by varying the etching parameters to achieve similar porosities. The PSi samples were subjected to UV–vis spectrophotometry in order to measure their reflectivity. The refractive indexes predicted by DFT were compared to those obtained by the Fresnel equation and the effective medium approximation methods (EMA), particularly Bruggeman's, Looyenga's and del Rio's model (dRZW). These studies showed that the PSi dielectric constant decreases with increasing porosity, which is consistent with a decrease in the refractive index. In addition, as the porosity of PSi rises, the bandgap energy values increase, which is closely related to the decrease in the refractive index. For low porosity, DFT and Looyenga refractive indexes fit better than dRZW or Bruggeman. Furthermore, when the porosity is increased, DFT gives similar results as dRZW and is better than the Bruggeman method. Moreover, at medium porosity (28 or 40%), DFT and EMA models agree well with the experimental refractive indexes of PSi. [ABSTRACT FROM AUTHOR]

The wet-season atmosphere in the central Amazon resembles natural conditions with minimal anthropogenic influence, making it one of the rare preindustrial-like continental areas worldwide. Previous long-term studies have analyzed the properties and sources of the natural Amazonian background aerosol. However, the vertical profile of the planetary boundary layer (PBL) has not been assessed systematically. Since 2017, such a profile assessment has been possible with the 325 m high tower at the Amazon Tall Tower Observatory (ATTO), located in a largely untouched primary forest in the central Amazon. This study investigates the variability of submicrometer aerosol concentration, size distribution, and optical properties at 60 and 325 m in the Amazonian PBL. The results show significant differences in aerosol volumes and scattering coefficients in the vertical gradient. The aerosol population was well-mixed throughout the boundary layer during the daytime but became separated upon stratification during the nighttime. We also found a significant difference in the spectral dependence of the scattering coefficients between the two heights. The analysis of downdrafts and the related rainfall revealed changes in the aerosol populations before and after rain events, with absorption and scattering coefficients decreasing as optically active particles are removed by wet deposition. The recovery of absorption and scattering coefficients is faster at 325 m than at 60 m. Convective events were concomitant with rapid increases in the concentrations of sub-50 nm particles, which were likely associated with downdrafts. We found that the aerosol population near the canopy had a significantly higher mass scattering efficiency than at 325 m. There was also a clear spectral dependence, with values for λ=450 , 525, and 635 nm of 7.74±0.12 , 5.49±0.11 , and 4.15±0.11 m 2 g -1 , respectively, at 60 m , while at 325 m the values were 5.26±0.06 , 3.76±0.0 5, and 2.46±0.04 m 2 g -1 , respectively. The equivalent aerosol refractive index results, which were obtained for the first time for the wet season in the central Amazon, show slightly higher scattering (real) components at 60 m compared to 325 m of 1.33 and 1.27, respectively. In contrast, the refractive index's absorptive (imaginary) component was identical for both heights, at 0.006. This study shows that the aerosol physical properties at 60 and 325 m are different, likely due to aging processes, and strongly depend on the photochemistry, PBL dynamics, and aerosol sources. These findings provide valuable insights into the impact of aerosols on climate and radiative balance and can be used to improve the representation of aerosols in global climate models. [ABSTRACT FROM AUTHOR]

Electromagnetic scattering is a routine tool for rapid, non-contact characterization of particle media. In previous work, the interaction targets of scattering intensity, scattering efficiency, and extinction efficiency of Bessel pincer light-sheet beams were all aimed at dielectric spheres. However, most particles in nature are charged. Considering the boundary condition on a charged sphere, the beam shape coefficients (BSCs) ( p m n , q m n ) of the charged spherical particle illuminated by a Bessel pincer light-sheet beam are obtained. The extinction, scattering, and absorption efficiencies are derived under the generalized Lorenz–Mie theory (GLMT) framework. This study reveals the significant differences in scattering characteristics of Bessel pincer light-sheet beams on a charged particle compared to traditional beams. The simulations show a few apparent differences in the far-field scattering intensity and efficiencies between charged and natural spheres under the influence of dimensionless size parameters. As dimensionless parameters increase, the difference between the charged and neutral spheres decreases. The effects of refractive index and beam parameters on scattering, extinction, and absorption coefficients are different but tend to converge with increasing dimensionless parameters. When applied to charged spheres with different refractive indices, the scattering, extinction, and absorption efficiencies of Bessel pincer light-sheet beams change with variations in surface charge. However, once the surface charge reaches saturation, these efficiencies become stable. This study is significant for understanding optical manipulation and super-resolution imaging in single-molecule microbiology. [ABSTRACT FROM AUTHOR]

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Herein, we report the extraction of natural pigment curcumin from curcuma longa and their linear and third-order nonlinear optical (NLO) characteristics. The characterization techniques viz., UV–Visible absorption, FT-IR, Micro Raman and Gas Chromatography Mass Spectrum (GC–MS) are used to study the spectral characteristics of curcumin. Third-order NLO features of curcumin are studied using Z‒scan technique with a semiconductor diode laser working at 405 nm wavelength. The natural pigment exhibits negative nonlinear index of refraction resulting from self-defocusing and positive coefficient of absorption is the consequence of reverse saturable absorption (RSA). The order of nonlinear index of refraction (n2) and nonlinear coefficient of absorption (β) is measured to be 10−7 cm2/W and 10−2 cm/W, respectively. Third-order NLO susceptibility (χ(3)) and second-order hyperpolarizability (γ) of curcumin is measured to be 2.73 × 10‒7 esu and 1.67 × 10‒31 esu, respectively. A low optical limiting (OL) threshold of 0.71 mW is observed in the extracted pigment. The experimental results are supplemented by quantum mechanical calculations of the NLO parameters. The overall result finding is that curcumin extracted from curcuma longa has the potential to be novel optical candidates for photonics and optoelectronics applications. [ABSTRACT FROM AUTHOR]

Physical properties of mantle minerals are essential for comprehensive geodynamic modeling. High-pressure experiments allow measurements of physical properties but fundamental insights into their evolution with pressure are often experimentally inaccessible. Here we report the first in situ experimental determination of the optical refractive index, its wavelength-dispersion, and optical absorption coefficient of ferropericlase up to ~140 GPa at room temperature. All these properties change gradually in dominantly high-spin (below ~50 GPa) and low-spin (above ~80 GPa) ferropericlase. However, in the mixed-spin state (i.e., significant presence of both high- and low-spin iron), the index dispersion and the absorption coefficient decrease by a factor of three and ~30%, respectively. These anomalies suggest that charge transport by small polaron is reduced in mixed-spin ferropericlase, providing fundamental insights into the factor-of-three lower electrical conductivity of ferropericlase at ~50–70 GPa. [ABSTRACT FROM AUTHOR]

This work investigates the inverse coupled radiation–conduction problem for estimating thermophysical parameters and source terms by an improved grey wolf optimization (GWO). The transient coupled radiation–conduction heat transfer problem in participating slab media is solved by the finite volume method. The radiative intensities on both boundaries are adopted as known measurement information in the inverse model. To overcome the disadvantages of the original GWO algorithm, an improved grey wolf algorithm (IGWO) is developed by introducing the weight strategy and nonlinear factors. Three benchmark functions are adopted to prove that the IGWO has a faster convergence speed and higher estimation accuracy than the original one. The IGWO is applied to inverse the thermophysical parameters and source terms based on the coupled radiation–conduction model; the results indicate that the IGWO is accurate and effective for estimating refractive index, absorption coefficient, and source terms. [ABSTRACT FROM AUTHOR]

In this work, we study the electric and magneto-optical absorption coefficients (ACs) and relative refractive index changes (RRICs) in W x Mo 1 − x S2 ternary alloys under the control of tungsten contents using the compact density matrix approach. With the influence of external electric and magnetic fields, the results show that there are a series of resonant peaks for both intra-band and inter-band transitions. With an increase in W-concentration and electric and magnetic fields, the resonant peaks give a blue (red) shift and reduce (increase) their amplitudes. These results suggest a potential application of monolayer W x Mo 1 − x S2 in future nanoscale electronic and magneto-optical devices. [ABSTRACT FROM AUTHOR]

The effects of environmental properties on the linear and nonlinear response of Bromothymol blue (BTB) were studied. The role of the optical band gap and dielectric constant, as well as thermal conductivity, on the optical properties of the BTB molecule and the BTB complex with cetyl trimethyl ammonium bromide (CTAB) were discussed using a Z-scan instrument with a wavelength of 532 nm and power of 80 mW, a spectrophotometer, and FT-IR spectra. The orders of the nonlinear absorption coefficient, β, and the nonlinear refractive index, n2, of BTB were obtained as 10−7 cm/W and 10−12 cm2/W, respectively. The main factor in the appearance of β is reverse saturable absorption. It was observed that an enhancement of up to 5 times in the dielectric constant of the environment caused a reduction of about 6 times in the nonlinear absorption and about 2 times in the nonlinear refraction coefficient of the solution. Moreover, the CTAB complex can reduce the optical band gap of BTB by 0.7 eV and also absorbs light in the 600 to 700 nm wavelength. Therefore, it is a promising candidate for photodynamic therapy. Results of DFT calculations performed via the B3LYP method and the 6-311G(d,p) basis show an enhancement of the dipole moment of BTB with an increase in the dielectric constant of the environment. [ABSTRACT FROM AUTHOR]

This article reports the nonlinear refractive index (n2) and nonlinear absorption coefficient (β) of acid blue 129 (AB 129) dye-doped polyvinyl alcohol (PVA) thin film with different dye concentrations using Z-scan technique. The experimental technique consists of a continuous wave laser with 5 mW power working at 635 nm wavelength. The normalized transmittance curve suggests that the dye-doped polymer film exhibits a self-defocusing nonlinear index of refraction and a large nonlinear absorption coefficient ascribed to the behaviour of reverse saturable absorption. The order of third-order NLO susceptibility of the sample is estimated to be 10‒5 esu. The dye-doped polymer films show a low-limiting threshold of 0.15 kW cm–2 at 0.04 mM dye concentration and believed that the prepared thin film is a suitable candidate for application in optical limiting. The self-diffraction pattern is observed at far-field and estimated the nonlinear refractive index of the thin film using this technique. The results of the nonlinear refractive index of the sample obtained from the self-diffraction method are comparable with Z-scan results. [ABSTRACT FROM AUTHOR]

Herein, we report the nonlinear refractive index and nonlinear absorption coefficient of anthraquinone dye (disperse blue 14)-doped polymer film using a facile Z-scan technique. The Z-scan studies were carried out using a semiconductor diode laser with a constant power output of 5 mW at a wavelength of 635 nm as the source of excitation. The Z-scan technique consists of closed and open aperture methods, which revealed the self-defocusing and reverse saturable absorption mechanisms based optical nonlinearity. The third-order nonlinear optical susceptibility (χ(3)) of dye-doped polymer film was estimated to be in the order of 10–5 esu. Optical limiting (OL) behaviour of the polymer film with different dye concentrations was performed under the same experimental conditions and found to be a low OL threshold of 1.45 × 102 W cm–2 at 0.04 mM dye concentration. Self-diffraction ring pattern of the polymer film was also noticed in the far field. The overall results found that the dye-doped polymer film is a potential material for photonics and optoelectronics applications. [ABSTRACT FROM AUTHOR]

We provide a simple method that enables readily acquired experimental data to be used to predict whether or not a candidate molecular material may exhibit strong coupling. Specifically, we explore the relationship between the hybrid molecular/photonic (polaritonic) states and the bulk optical response of the molecular material. For a given material, this approach enables a prediction of the maximum extent of strong coupling (vacuum Rabi splitting), irrespective of the nature of the confined light field. We provide formulae for the upper limit of the splitting in terms of the molar absorption coefficient, the attenuation coefficient, the extinction coefficient (imaginary part of the refractive index) and the absorbance. To illustrate this approach, we provide a number of examples, and we also discuss some of the limitations of our approach. [ABSTRACT FROM AUTHOR]

In this study, titanium dioxide (TiO2) nanoparticles are combined with a mixture of polymers (polyvinylalcohol PVA, polyethylene-glycol PEG and polyvinylpyrrolidone PVP). Titanium dioxide (TiO2) NPs was formulation by sol-gel process, nanocomposites were prepared with concentration (1, 5, 10, 15, 20 and 25 wt%). TiO2 NPs after subjecting them to a calcination process at a temperature of about 400 °C and 700 °C and polymer blend of different concentrations (PVA various wt%, PEG constant wt% and PVP constant wt%). A UV-Vis spectrometer was used to determine the optical constants of the prepared-samples. Absorption coefficient, extinction coefficient, refractive-index and optical energy-gap were calculated, it was noticing of absorption coefficient values in calcination 400 °C for 25 wt% TiO2 NPs higher than that of other samples. The refractive index of TiO2 at 700 °C is higher than that of 400 °C due to the different crystalline structure of rutile. The optical energy band gap was determined and it was discovered to decrease from 5.16 eV for (1 wt% TiO2) blended with (PVA 84 wt%, PEG 10 wt% and PVP 5 wt%) up to 3.51 eV (25 wt% TiO2) with concentrations of (PVA 60 wt%, PEG 10 wt% and PVP 5 wt%) as matrix. At a higher calcination temperature of 700 °C, TiO2 transitions from the anatase phase to the rutile phase, this change in crystal structure has a significant effect on the value optical dielectric constant real part (εr) which is (16.06). The findings have important ramifications for possible uses these nanocomposites to enable reuse of the photocatalysts, thus extending their useful life. [ABSTRACT FROM AUTHOR]

The magnetocaloric and optical properties of Dy2MnNiO6 (DMNO) were investigated using first-principles calculations and Monte Carlo simulations. The calculated magnetic exchange interactions reveal ferromagnetic couplings between the magnetic ions. The Mn-Ni interactions in DMNO are found to be long-range ferromagnetic, indicating the localization of 3d-orbitals in the presence of 4f orbitals. The analysis of the density of states, suggesting a strong ferromagnetic superexchange interaction between Mn and Ni, which is mediated by the oxygen ions. DMNO exhibits a maximum entropy change and relative cooling power are found. DMNO displays a strong frequency dependence, characterized by a high static refractive index. The real dielectric function is notably high, reflecting the refractive index measured at low frequencies. The absorption coefficient in the visible and near-infrared regions is relatively low. Conversely, its high reflectivity in these regions suggests a reflective property. [ABSTRACT FROM AUTHOR]

β-Heptasubstituted porphyrins [MTPP(NO2)X6; M = 2H, NiII, CuII, and ZnII; X = Br, Ph, and PE] were synthesized and their third-order nonlinear optical (NLO) properties explored using the single-beam Z-scan technique with femtosecond, MHz pulses in the visible range. The three-photon absorption (γ), thirdorder nonlinear optical susceptibility (χ³), three-photon absorption cross-section (σ3), and nonlinear refractive index (n2) have been determined from theoretical fits with experimental results. The sign and magnitude of the nonlinear refractive index (n2) have been obtained from the closed-aperture experiment while the three-photon absorption coefficient and three-photon absorption cross-section were determined from the open-aperture experiment. The magnitudes of the 3PA and σ3 extended in the range of (2.7-3.4) × 10-23 cm³ W-2 and (5.5-7.0) × 10-78 cm6 s², respectively. The higher magnitude of the NLO coefficients ensures their utility in optical and photonic applications. [ABSTRACT FROM AUTHOR]

We report the wavelength dependencies of the two-photon absorption coefficients β as well as the nonlinear refractive index n2 of undoped β-Ga2O3 single crystal in the spectral range 350–515 nm (0.51 < Ephoto/Eg < 0.75). Femtosecond Z-scan measurements show that n2 decreases monotonically toward the shortwave side, while the maximum value of n2 is 5.0 × 10−19 m2/W near half of the bandgap, Eg. Interestingly, a second upward trend in β was observed when the incident photon energy is larger than 0.6Eg, indicating the impact of additional inter-band transitions with higher energy. A higher-energy band-to-band transition around 6.0 eV was determined by both femtosecond nondegenerate two-photon absorption spectroscopy and ab initio calculations. Our results could provide guidance for designing nonlinear β-Ga2O3 photonic devices in the UV-visible spectral range. [ABSTRACT FROM AUTHOR]

The present work intended to report the synthesis of newly designed donor-acceptor complexes of the pyrimidine-based system namely TAPHIA 1 and TAPHIA 2, which are symphonized to give the NLO properties. The methodologies adopted for both complexes were different and hence influenced their geometrical properties. The synthesized complexes were characterized using different techniques including SCXRD, FTIR, UV, PXRD, and TGA to confirm their formation. The SCXRD analysis revealed that TAPHIA 1 was crystallized in the Pca21 space group in an orthorhombic system while TAPHIA 2 was crystallized in the P21/c space group in a monoclinic system. The third-order NLO properties of both complexes were explored using the Z-Scan technique by employing a continuous wave (CW) diode laser of 520 nm. The third-order NLO parameters including nonlinear refractive index (n2), nonlinear absorption coefficient (β) and nonlinear optical susceptibility (χ (3)) were calculated at different powers; 40, 50 and 60 mW at fixed solution concentration (10 mM) for both the complexes. Moreover, the experimental properties including NLO, FTIR, and UV were well corroborated with theoretical results obtained at the B3LYP-D3/6-31++G(d,p) level of theory. The analysis of the theoretical and experimental properties of both complexes suggests that TAPHIA 2 is a better applicant to be employed in optical devices than TAPHIA 1 due to the enhanced ability of internal charge transfer. Symphonizing effect of NLO properties exhibited by two newly synthesized donor acceptor complexes namely TAPHIA 1 and TAPHIA 2. The NLO potential of the two newly reported organic complexes were influenced by their structural properties and charge transfer ability, made them good applicants to be employed in optoelectronic field. [ABSTRACT FROM AUTHOR]

This study uses computational analysis to comprehensively investigate lead‐free organic–inorganic CH3NH3SnI3 (MASnI3)‐based perovskite solar cells (PSCs). The optoelectronic properties of MASnI3 are investigated using density functional theory with first‐principles calculations, highlighting its potential for photovoltaic applications. Key findings include the determination of a crucial bandgap (0.97 eV), identification of the onset of photon absorption at energies exceeding 2 eV, and characterization of material properties, such as the absorption and extinction coefficients, reflectivity, and refractive index. Device optimization through simulations explores parameters such as layer thickness, defect density, and different charge transport layers, resulting in a remarkable enhancement in the power conversion efficiency to 16.72%. Additionally, this study focuses on the influence of the working temperature, series resistance (Rs), and shunt resistance (Rsh) on the photovoltaic device performance. Hence, a high photovoltaic efficiency in MASnI3‐based PSCs can be achieved by carefully optimizing the device performance parameters and effectively managing the defect densities. [ABSTRACT FROM AUTHOR]

This study aims to provide a concise overview of the behavior exhibited by Sn-doped ZnO crystals using a computational technique known as density functional theory (DFT). The influence of Sn doping on the electronic, structural, and optical properties of ZnO have been explored. Specifically, the wavelength dependent refractive index, extinction coefficient, reflectance, and absorption coefficient, along with electronic band gap structure of the Sn doped ZnO has been examined and analyzed. In addition, X-ray diffraction (XRD) patterns have been obtained to investigate the structural characteristics of Sn-doped ZnO crystals with varying concentrations of Sn dopant atoms. The incorporation of tin (Sn) into zinc oxide (ZnO) has been observed to significantly impact the opto-electronic properties of the material. This effect can be attributed to the improved electronic band structure and optical characteristics resulting from the tin doping. Furthermore, the controllable structural and optical characteristics of tin-doped zinc oxide will facilitate the development of various light-sensitive devices. Moreover, the impact of Sn doping on the optoelectronic properties of ZnO is thoroughly investigated and documented. [ABSTRACT FROM AUTHOR]

In this investigation, a nanostructured Cu2O thin film absorber layer is electrodeposited, exploring the impact of varying negative applied voltages and deposition time. Notably, the Cu2O thin film demonstrated optimal absorbance at −0.95 V, contrasting sharply with a minimum at −0.97 V. The authors' findings underscore that the peak absorbance was achieved at −0.95 V, coinciding with the lowest transmittance observed after 80 min of deposition, aligning with a maximal absorption coefficient of 21 × 103 cm−1. At a deposition time of 5 min, the Cu2O thin film exhibited a noteworthy maximum Urbach energy of 2.00 eV and a minimum steepness parameter of 0.013. In contrast, the lowest Urbach energy was recorded at 0.34 eV, with the highest steepness parameter occurring at an applied voltage of 0.93 V. Furthermore, this study revealed a gradual increase in the refractive index with higher applied voltages, reaching its pinnacle at −1.5 V. These results collectively emphasize the nuanced interplay between applied voltage, deposition time and the optical properties of the nanostructured Cu2O thin film. The observed trends hold significant implications for optimizing the performance of thin film absorber layers, particularly in the context of enhancing absorbance and tailoring optical characteristics for specific applications. [ABSTRACT FROM AUTHOR]

In the work is devoted to the study of the optical properties of ZnO nanorods grown on LiNbO3 and LiNbO3:Fe (0.03 wt %) substrates. The morphology and absorption spectra of the resulting semiconductor-ferroelectric structures are analyzed. According to it, the band gap of the structures is in the range of 3.34–3.86 eV, absorption coefficients (1.9099–3.5137 for the visible region and 2.0585–4.2344 for the UV region). Refractive index calculated using various empirical formulas. [ABSTRACT FROM AUTHOR]

Herein, a comprehensive theoretical analysis of Tm‐based chalcogenides MgTm2Y4 (Y = S, Se) is performed to understand magnetic, optical, mechanical, and transport characteristics. And, Perdew–Burke–Ernzerhof generalized gradient approximation (PBEsol‐GGA) functional and modified Becke–Johnson (mBJ) potentials are employed while computing the mechanical and spin‐polarized electronic properties, respectively. The structural stability of both spinels is confirmed using formation energy and Born stability criteria. Both spinels are found exhibiting ductile nature according to the computed Pugh's and Poisson's ratios. For observing the room‐temperature ferromagnetism, Curie temperature is calculated. Furthermore, spin‐polarized electronic properties reveal that both spinels exhibit ferromagnetic nature, which is induced due to coupling among Tm‐ and S/Se‐related constituent states. The potential optoelectronic applications are suggested by computing and discussing dielectric constant, refractive index, and absorption coefficient. BoltzTraP code is used to investigate the thermoelectric features of MgTm2Y4 (Y = S, Se) in the 200–800 K temperature range. [ABSTRACT FROM AUTHOR]

NiO thin films with varied oxygen contents are grown on Si(100) and c-Al2O3 at a substrate temperature of 300 °C using pulsed dc reactive magnetron sputtering. We characterize the structure and optical properties of NiO changes as functions of the oxygen content. NiO with the cubic structure, single phase, and predominant orientation along (111) is found on both substrates. X-ray diffraction and pole figure analysis further show that NiO on the Si(100) substrate exhibits fiber-textured growth, while twin domain epitaxy was achieved on c-Al2O3, with NiO (111) ∥ A l 2 O 3 (0001) and NiO [ 1 1 ¯ 0 ] ∥ A l 2 O 3 [ 10 1 ¯ 0 ] or NiO [ 1 ¯ 10 ] ∥ A l 2 O 3 [ 2 1 ¯ 1 ¯ 0 ] epitaxial relationship. The oxygen content in NiO films did not have a significant effect on the refractive index, extinction coefficient, and absorption coefficient. This suggests that the optical properties of NiO films remained unaffected by changes in the oxygen content. [ABSTRACT FROM AUTHOR]

Pressure-induced phases of ZnO have attracted considerable attention owing to their excellent electronic and optical properties. This study provides a vital insight into the electronic structure, optical characteristics, and structural properties of the AsTi (Bi) phase of ZnO under high pressure via the DFT-based first-principles approach. The phase transformation from BN(Bk) to the Bi phase of ZnO is estimated at 16.1 GPa using local density approximation, whereas the properties are explored precisely by the hybrid functional B3LYP. The electronic structure exploration confirms that the Bi phase is an insulator with a wider direct bandgap, which expands by increasing pressure. The dielectric function evidenced that the Bi phase behaves as a dielectric in the visible region and a metallic material at 18 eV. Optical features such as the refractive index and loss function revealed the transparent nature of the Bi phase in the UV range. Moreover, the considered Bi phase is found to possess a high absorption coefficient in the ultraviolet region. This research provides strong theoretical support for the development of Bi-phase ZnO-based optoelectronic and photovoltaic devices. [ABSTRACT FROM AUTHOR]

We report on the study of far-infrared transmission in silicon carbide of 6H polytype in the region of IR active folded transverse acoustic (FTA) phonon doublet. Joint analysis of the transmittance spectra obtained at low and high resolutions is performed to determine spectral dependences of the refractive index and absorption coefficient. A dual Lorentz oscillator model is used to simulate the FTA phonon contributions to the dielectric function. The oscillator strengths and phonon lifetimes for both the components of the FTA phonon doublet in 6H-SiC are determined. At temperature decrease from 300 to 5 K, the FTA phonon lifetimes increase more than six times, while the oscillator strengths remain the same. [ABSTRACT FROM AUTHOR]

Spatially Offset Raman Spectroscopy (SORS) has extensively been studied as a non-invasive technique that can detect the internal composition below the surface of turbid samples. A critical application of SORS is to identify unknown materials behind a highly scattering obstacle, such as plastic containers. The mechanism of SORS can be generally demonstrated as the photon migration theory; the Raman photons inside deeper samples are more likely to propagate laterally. However, a comprehensive view of the SORS mechanism still needs to be improved. In this work, a numerical simulation was carried out by the Monte Carlo algorithm to investigate the characteristics of SORS being affected by the various optical properties of materials, such as scattering coefficients, absorption coefficients, and refractive index. The key characteristics of SORS, such as detection depth, optimal offset, and signal intensity, were systematically analyzed in a monolayer medium and a bilayer medium. These findings provide important additional information on SORS theory and have important implications for the development of SORS as a reliable analytical tool in various fields, including biomedical research and environmental monitoring. [ABSTRACT FROM AUTHOR]

This paper reports the use of Raman and time-domain terahertz spectroscopy to ascertain the potential of antibiotic cefixime drug which is widely used for curing bacterial infections and obtained from different pharmaceuticals companies. The indigenously designed terahertz spectrometer between 0.1–2.8 THz range was employed for recording of time domain spectra of drug molecules. The refractive index, absorption coefficients and absorbance strength of this drug in THz domain were also ascertained. THz-Raman spectra simultaneously helps to characterize the crystalline nature of cefixime.s and its chemical composition and effect and concentration of its principal ingredients. The Raman spectra of these drugs molecules was recorded for cross verification of previous experimental findings. Finally, we have identified the absorbance strength of two important ingredients, i. e., sulpha pyridine and sulpha thiazoles and specific absorbance of these ingredients was ascertained in THz domain to quantify the concentration per milligram level between 0.5 and 0.8 THz range. The obtained results reveal that concentration of these two ingredients varies from sample to sample. It help to determine the efficacy and side effects of the drugs produced from different manufacturers. [ABSTRACT FROM AUTHOR]

The Z-scan instrument was used to study the nonlinear optical (NLO) properties of the derivatives of 3,3′-biindole 2,2′(1H,1′H)-dione, with different substitutions such as bromine, methyl, and phenyl groups. Specifically, the nonlinear absorption coefficient, β, nonlinear refraction index, n 2 , have been extracted and reverse saturation absorption and self-defocusing phenomena were investigated. It is observed that the presence of bromine in the compound structure can reduce the NLO properties. The reduction of dipole moment with bromine substitutions in the compound structure was confirmed with the quantum calculation. The NLO properties of the biindole derivatives related to the thermo-optic coefficient and dipole moment of the compound. Overall, our findings indicate that the biindole derivatives are promising candidates for NLO absorption materials. [ABSTRACT FROM AUTHOR]

A thin-film (215 nm) of indigo dye has been deposited on a polymer substrate (polyacetate) using thermal evaporation. The structure of the prepared film has been investigated using X-ray diffraction, showing X-ray amorphous or fine nanocrystalline nature. Analysis of the absorption coefficient in the strong absorption regions shows two indirect optical transitions with energy gaps (2.45 and 1.64 eV) in addition to the energy gap of the substrate (3.5 eV). Values of the refractive index have been calculated using four different methods. The average refractive index values near the first and second absorption edges are 2.525 and 2.871, respectively. The average values of the optical dielectric constant near the two corresponding edges are 6.377 and 8.064. Furthermore, the corresponding values of the nonlinear optical susceptibilities and nonlinear refractive index are in the same order of magnitude as other promising organic materials. This recommends indigo-thin films for flexible organic electro-optical applications. [ABSTRACT FROM AUTHOR]

We present experimental and theoretical evidence demonstrating the Mie resonance effect in the terahertz (THz) range, utilizing Fe3O4/Kerosene ferrofluid. Our findings indicate a significant and rapid change in the complex refractive indices at 0.5 THz with an increase in the magnetic field strength. Moreover, we observed a prominent absorption peak at 0.5 THz in transmittance and absorption coefficient measurements, corresponding to a magnetic field intensity of 178.0 mT. This phenomenon occurs due to the adjustment of particle spacing, leading to resonance under different magnetic field conditions. These research results hold immense potential in advancing the development of magneto-optical THz modulators for imaging and communication applications. [ABSTRACT FROM AUTHOR]

This numerical study scrutinizes the impact of both the thickness of layers and an externally applied magnetic field on the optical absorption coefficient and alterations in the refractive index pertaining to the intersubband optical transition (1-2) within an asymmetric double parabolic structure, utilizing GaAs/AlGaAs quantum wells as a basis. Energy levels and their corresponding wave functions have been ascertained through the use of the shooting method. The findings of this investigation suggest a pronounced sensitivity of the optical absorption coefficient and changes in the refractive index to the thickness of the layers and the applied external magnetic field. It has been observed that the intensification of the magnetic field results in a resonant peak position shifting towards higher energy values, whereas the thickness of the layers exerts an influence on the resonance peak magnitude. The insights derived from this study hold considerable potential for application, particularly in the development of optical devices predicated on intersubband electronic transitions. [ABSTRACT FROM AUTHOR]

This work systematically studies the electronic and optical properties of H-terminated armchair silicene nanoribbon (HASiNR) for oxygen (O2) adsorption using first-principles calculations. The results show that the most stable site for O2 adsorption is the edge of the ribbon, which possesses relatively low adsorption energy of −2.46 eV, indicating good stability. Particularly, the adsorption energy decreases gradually with the increase of the oxygen concentration. It was also found that the direct bandgap of HASiNR can be effectively tuned by changing the adsorption concentration of O2 gas. Additionally, the analysis of the density of states shows that the adsorption of O2 on HASiNR is chemisorption due to the apparent charge transfer from the ribbon to O2 gas. Besides, the work function, absorption coefficient and refractive index of the HASiNR are sensitive to O2 gas adsorption. Therefore, our studies prove that oxygen gas adsorption allows the HASiNR to modulate its electronic and optical properties. [ABSTRACT FROM AUTHOR]

The full potential linearized augmented plane wave (FP-LAPW) approach based on the density functional theory (DFT) is employed to know the effect of Co doping on the electronic, optical, and magnetic characteristics of BaTi1-xCoxO3 at x= 8.33%, 16.66%, 25%, and 50%. The computed spin-polarized electronic band structure (BS) and the density of states (DOS) elucidate that the BaTi1-xCoxO3 compound has a ferromagnetic semiconductor behavior at all doping concentrations. The results indicate that the magnetic moment in BaTi1-xCoxO3 is found due to the p-d hybrid orbitals of Co. Moreover, the optical features of the Co-doped BTO compound are evaluated by analyzing the refractive index, reflectivity, absorption coefficient, optical conductivity, and dielectric constant under different concentrations. The outcomes revealed that the BaTi1-xCoxO3 compound is a good candidate for spintronics and optoelectronic applications. [ABSTRACT FROM AUTHOR]

Spectroscopic microtomography provides the ability to perform 4D (3D structural and 1D chemical) imaging of a thick microscopic specimen. Here, we demonstrate spectroscopic microtomography in the short-wave infrared (SWIR) wavelength using digital holographic tomography, which captures both the absorption coefficient and refractive index. A broadband laser in tandem with a tunable optical filter allows us to scan the wavelength from 1100 to 1650 nm. Using the developed system, we measure human hair and sea urchin embryo samples. The resolution estimated with gold nanoparticles is 1.51 μ m (transverse) and 1.57 μ m (axial) for the field of view of 307 × 246 μ m 2 . The developed technique will enable accurate and efficient analyses of microscopic specimens that have a distinctive absorption or refractive index contrast in the SWIR range. [ABSTRACT FROM AUTHOR]

Structural, electronic, magnetic and optical properties of orthorhombic perovskite PrMn1-xFexO3 (0 ≤ x ≤ 1) have been performed using first-principles density functional calculations. We focused on Mn-rich, Fe-rich and intermediate compounds in ferromagnetic and antiferromagnetic spin ordering. Our results show the ferromagnetic semiconductor behavior in PrMn0.5Fe0.5O3 due to the Fe3+–O–Mn3+ ferromagnetic super-exchange interaction, while half-metallic antiferromagnetic behavior in Mn-rich and Fe-rich compounds due to the Mn–O–Mn and Fe–O–Fe interactions. The absorption coefficient α ω , reflectivity R ω and the refractive index n ω of pure and mixed PrMn1-xFexO3 perovskites are also discussed. [ABSTRACT FROM AUTHOR]

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In this research, Zn(1−x)CrxAl2O4 (x = 0.00, 0.05, 0.10, 0.20) nanoparticles were prepared by a simple and green chemistry synthesis using gelatin as a polymerization agent. X-ray diffraction technique and scanning electron microscopy imaging were used to analyze the structural and morphological properties of the samples. X-ray diffraction results revealed that all samples were polycrystalline and crystallized in a cubical spinel phase. With increasing the x from 0.00 to 0.20, the main Bragg peaks shift to smaller angles, and the crystallite size and energy bandgap of samples decrease as well. The nonlinear absorption coefficient, β, and nonlinear refractive index, n2, of Zn(1−x)CrxAl2O4 were meticulously studied by the Z-scan approach. The orders of n2 and β are 10−7 and 10−4 cm/W, respectively. The saturable absorption and the self-defocusing effect are the main factors in the appearance of β and n2, respectively. The experimental results confirmed that increasing the percentage of Cr caused nonlinear coefficients to increase. [ABSTRACT FROM AUTHOR]

The present work reports the influence of selenium replacement by bismuth on the nonlinear optical parameters of ternary Se85-xTe15Bix (x=0, 1, 2, 3, 4, 5 atomic %) chalcogenide thin films. Calculation of nonlinear refractive index (n2), two-photon absorption coefficient (β2) and third-order susceptibility (χ(3)) by well known Z-scan technique with femtosecond laser pulses were done. The Z-scan spectra for Se85-xTe15Bix upto Bi= 4 atomic % results in self-focusing behavior of n2 is positive while for Bi=5 atomic % n2 is negative. The behavior of n2 by using different physical parameters are exlpained. The comparison of experimental and theoretical values of n2 with pure silica are also studied. The presence of the valley at focus in open aperture Z-scan graph demonstrates strong reverse saturable absorption. The figure of merit (FOM) for the Se-Te-Bi chalcogenide thin films is found to be less than 1 and are beneficial for all-optical switch devices. [ABSTRACT FROM AUTHOR]

Triple-layered structures, containing gold nanoparticles (AuNP), namely AuNP(6 nm)–Al2O3(1.5 nm)–PdO(17 nm), sample #1, and AuNP(6 nm)–Al2O3(13 nm)–PdO(17 nm), sample #2, were obtained on glass substrates. A significant difference in the structure of their absorption spectra in the vicinity of the plasmon resonance of gold nanoparticles indicates a dependence on the mutual influence of the AuNP and PdO layers on the thickness of the Al2O3 insulating layer. Optical cubic nonlinearity (OCN) parameters, namely n2, Reχ(3), and Imχ(3), were determined for nanosecond pulsed laser excitation at λ = 1064 nm (τp = 15 ns) and λ = 532 nm (τp = 9 ns). It is shown that under 1064 nm excitation: (i) the sign of the refractive nonlinearity of the structures depends on the way they are illuminated in a Z-scan experiment, being positive when the laser beam impinges from the AuNP side (geometry A) and negative if the beam falls from the PdO side (geometry B); (ii) the nonlinear index of refraction n2 = 2.5 × 10–7 cm2/W of the structure #1 with a 1.5 nm thick Al2O3 layer is significantly larger than n2 = 0.9 × 10–7 cm2/W of the structure #2 with a 13 nm Al2O3 layer; (iii) the refractive nonlinearity of triple-layer structures is larger than that of double-layer structures AuNP-Al2O3; (iv) both double and triple-layer structures demonstrate moderate non linear absorption (β ~ 10–2 cm/W), probably due to two-photon transitions between the d and sp bands of AuNP. For 532 nm excitation, the refractive nonlinearity of the triple layer structures is negative with |n2|~ 10–6 cm2/W irrespective of the geometry of the Z-scan experiment. For both samples #1 and #2 with different thickness of Al2O3 the value of |n2| is sufficiently larger than one for separate PdO film. This may be explained by the strong influence of interaction of processes in the AuNP and conductive PdO layers. The nonlinear absorption coefficient β is negative (saturable absorption) in AuNP-Al2O3 structures and positive in AuNP-Al2O3-PdO structures. [ABSTRACT FROM AUTHOR]