Linear Absorption Coefficient Research Articles

Electric field-induced electronic structure and intersubband transitions of a hydrogen molecular ion in a gaussian-type quantum ring

In this work, the influence of an external electric field on the electronic structure and intersubband transitions of a singly ionized double-donor system in a GaAs quantum ring defined by Gaussian-type potentials is investigated theoretically. Within the framework of the effective mass approach, the two-dimensional diagonalization method is used for the solution of the Schrödinger equation to obtain the eigen energies and corresponding wave functions. Numerical results reveal that the electronic energy spectrum and the linear optical absorption coefficient of the ring are remarkably affected by the strength of the lateral electric field, internuclear distance and parameters defining the confinement potential. Also, it has been shown that beyond the anti-crossing point, the wave functions exchange their symmetries without mixing, which is a characteristic feature of energy-level anti-crossing.

Novel zinc and gallium nanocomposites for protecting against green laser radiation

In the present communication, binary (ZnO:Ga2O3- 1:1 (ZGO), ZnO:Ga2O3- 2:1 (GaZn))/ternary (EZG (Eu2O3: ZnO: Ga2O3 (1:1:1)), MZG (MgO: ZnO: Ga2O3 (1:1:1)) NCs are synthesized by Piperbetle leaves extract as a reducing agent followed by calcination at 600 °C for 3 h. The Bragg reflections confirms the formation of single phase cubic symmetry with Fd3m space group in ZGO NCs whereas reflections related individual metal oxides are observed in the GaZn, EZG and MZG NCs. The irregular size and shaped nanoparticles are observed in all the synthesized NCs. The tuned band gap was found to be in the range of 3.08 to 3.11 eV. The optical nonlinearity of the specimens was analyzed using the open aperture Z-scan technique. The material demonstrated reverse saturable absorption attributed to a two-photon absorption (2PA) process. The non linear absorption coefficient follows the order MZG > GaZn > ZGO > EZG. However, the optical limiting threshold follows the order ZGO > GaZn > MZG > EZG NCs with increase in energy band gap. These outcomes distinctly indicate the superior potential of GaZn binary NCs for optical limiting applications. This characteristic is advantageous for shielding sensors and the human eye, safeguarding them against the detrimental effects of intense green laser radiation.

Radiation attenuation properties of yttrium lithium borate glasses

As the glass is used in a variety of fields, it is vital to test it on radiation shielding purposes. In this article, the radiation attenuation properties of examined glasses by replacing Li2O for Y2O3 have been investigated. The samples formulated as 72B2O3–(28-x)Li2O–xY2O3 (where x = 0,2,4,8,12 mol%). The parameters of linear absorption coefficients (LAC) and other parameters of half value layer (HVL), mean free path (MFP), tenth value layer (TVL) and effective atomic numbers were calculated. It was found that when Li2O is replaced to Y2O3, the radiation shielding properties of glasses increment.

Tunability of the nonlinear optical absorption in a GaAs/Ga0.7 Al0.3 As spherical quantum dots under external factors

We theoretically studied the linear, third-order nonlinear and total optical absorption coefficient changes of a typical GaAs/Al0.3Ga0.7As quantum dot system under the influence of hydrostatic pressure and temperature. The influence of hydrostatic pressure and temperature on the system is treated within the framework of effective mass. In this method, the relative changes of linear and nonlinear absorption coefficients are obtained by using density matrix method and iterative method. In addition, we also reveal the mechanism of the influence of hydrostatic pressure and temperature on the nonlinear optical properties, which is of great significance for us to better understand the causes. We have shown that hydrostatic pressure and temperature change the effective mass, resulting in significant changes in the linear and nonlinear optical properties of the system. In addition, we also reveal the mechanism of the influence of effective mass on the nonlinear optical properties, which is of great significance for us to better understand the causes.

Influence of external magnetic field on intraband transitions in lens-shaped quantum dot

Intraband linear and nonlinear optical absorption in a strongly oblate lens-shaped Ge/Si quantum dot in the presence of an axial magnetic field was theoretically studied. Quantum transitions are considered in the heavy hole subband, when the scalar effective mass approximation is correct. The linear and nonlinear absorption coefficients, refractive index changes and the second harmonic generation coefficient were determined. The influence of the effects of temperature, size quantization and magnetic field on the behavior of the above parameters was revealed.

Investigation on the Micro-Grinding Induced Crystallographic Variations of Nine Different Clinkers

Although clinker has been used for many years, complicated mineralogical properties of clinker pose challenges for the precise quantification. In this study, the mineralogical and crystallographic properties of nine different clinkers according to grinding procedures were investigated. With the dry-grinding for 2 h, particle size reduction to 3 μm of median particle size with a substantial phase transition to an amorphous phase observed, to which alite (C3S) mainly contributed to the transition. Meanwhile, the crystallographic properties of the clinker phases were barely changed during the wet-grinding. In the wet-grinding program, the amount of ferrite solid solution (C4AF) with a high linear absorption coefficient was not underestimated. Furthermore, well-corrected preferred orientation effect on C3S was positively contributed to the analysis result of clinkers with the wet-grinding. Hence, it was suggested that the crystallographic effects observed in the wet-grinding program could produce more reliable results in phase analysis for the clinkers.

Anomalous variations of optical properties in the vicinity of level anti-crossing in InAs/GaAs conical quantum dot nanowire

The present study focuses on the investigation of the linear and nonlinear optical properties corresponding to electronic transitions in the vicinity of Level Anti-Crossing (LAC) points from a theoretical perspective. The system under consideration is an InAs conical quantum dot embedded in an infinite GaAs nanowire. The special configuration of the system leads to repeatedly LAC points in the energy spectrum of the system, three of which are considered here. The findings indicate a forward-backward shift in the energy location of the linear and non-linear Absorption Coefficient (AC) around the LAC. On the other hand, it is demonstrated that in this vicinity, AC for the transition to one of the crossing levels vanishes while that of the other maximizes. It is also found that, save for the lowest transition, the nonlinear component has essentially little share of the total AC, nearly for all incident photon energies, due to the limited and low values of the transition dipole moment.

Optical properties of spherical quantum dot using screened Kratzer potential

Here we investigate the optical properties of a spherical quantum dot using the screened Kratzer potential. The density matrix formalism is employed to study refractive index changes, along with linear and nonlinear optical absorption coefficients. To this effect, the radial Schrödinger equation is solved using the Nikiforov–Uvarov functional analysis method, resulting in analytical expressions for the energy eigenvalues and the associated eigen functions. Effects of dot size, potential parameters, and screening length on these properties are analyzed in detail for a GaAs quantum dot. The obtained results reveal that the optical response of the system is highly sensitive to the dot size and potential parameters, and thus it can be tuned accordingly. The impact of external magnetic and Aharonov–Bohm flux fields on the optical properties of the GaAs quantum dot is also discussed. The findings of this study may provide useful insights in design and optimization of quantum dot-based optoelectronic devices.

Accurate Determination of the Low-Light-Level Absorption of DUV-Fused Silica at 193 nm with Laser Calorimetry

The low-light-level absorption coefficient of OH-contained and H2-impregnated synthetic fused silica material in 193 nm optical lithography application is determined via a laser calorimetry measurement. The fluence and repetition rate dependences of the absorptances of the deep ultraviolet (DUV)-fused silica samples with different thickness are measured. The measured dependences are fitted to a theoretical model, taking into consideration the generation and annealing of laser irradiation induced defects. The surface absorption, the low-light-level linear absorption coefficient, as well as the nonlinear absorption coefficient of the fused silica material are accurately determined via the fitting. The low-light-level linear absorption coefficients determined via the fluence dependence and the repetition rate dependence are in good agreement, demonstrating the reliability of the measured low-light-level absorption coefficient, which is the key parameter to the determination of the internal transmission of the DUV-fused silica material used in the 193 nm optical lithography.

Peculiar band geometry induced giant shift current in ferroelectric SnTe monolayer

The bulk photovoltaic effect (BPVE) occurs when homogeneous noncentrosymmetric materials generate photocurrent or photovoltage under illumination. The intrinsic contribution to this effect is known as the shift current effect. We calculate the shift current conductivities of the ferroelectric SnTe monolayer using first-principles methods. Our results reveal a giant shift-current conductivity near the valley points in the SnTe monolayer. More remarkably, the linear optical absorption coefficient at this energy is very small, resulting in an enormous Glass coefficient that is four orders of magnitude larger than that of BaTiO3. To understand these giant shift-current effects, we employ a three-band model and find that they arise from the nontrivial energy band geometries near the valley points, where the shift-vector diverges. This serves as a prominent example highlighting the crucial role of band geometry in determining the fundamental properties of solids.

Investigation of linear and nonlinear optical properties in quantum dots: Influence of magnetic and AB flux fields

In the present work, analytical expressions for the energy eigenvalues and eigen functions are obtained by solving the radial Schrödinger equation for inverse quadratic Hellmann plus Yukawa (IQHY) potential using Nikiforov-Uvarov functional analysis method. As an application part of this work, expressions for the linear and third-order nonlinear absorption coefficients and refractive index changes are computed to study the optical properties of the spherical GaAs quantum dots. We extend the investigation of the IQHY potential by incorporating the effects of magnetic and Aharonov–Bohm (AB) flux fields. Our results reveal that the optical properties of the GaAs quantum dots are strongly influenced by variations in the dot radius, potential height and intensity of incident photons. Specifically, we observe that the introduction of magnetic and AB flux fields significantly alters the energy eigenvalues and eigenfunctions, leading to distinct optical characteristics. The results of present study are found in consistent with other theoretical studies available in the literature.

A Study on The Optical Properties of Long-Infrared Intraband Transitions of Quadruple Gaas/Alxga1-Xas Quantum Well Under Applied Electric Field

Semiconductor-emitting/absorbing infrared devices are in the common interest of the scientific and industrial community due to their broad application in these fields. GaAs/AlGaAs based devices are one of the most studied semiconductor heterostructures. In this study, I have aimed to design GaAs/AlGaAs quantum well (QW) semiconductor heterostructures to emit/absorb in the long infrared region and studied the optical properties. To do that, I have designed a quadruple QW, which is composed of GaAs/Al0.44Ga0.56As QW and quantum barriers (QB). I have solved the time-independent Schrödinger equation using the finite element method-based matlab code under effective mass approximation. The wave functions and corresponding energy eigenvalues are obtained for varied electric field (EF) intensities. I have shown that our design can operate up to 80 kV/cm, which is the limit for first bounded energy eigenstates. It is observed that E_32 transition provides long-infrared emission/absorption corresponding to the 0.12-0.14 eV transition energy and it is constant with increased EF intensity. In addition, it is seen that the overlap of the wave functions is increasing with EF intensity which enhances radiative transition in the structure. I have calculated the linear absorption coefficient and refractive index change. I have observed that the absorption coefficient of E_32 transition is increasing with EF intensity while E_31 is decreasing and E_21 is constant. As a last, I have shown that EF intensity has a minor effect on refractive index change.

Методика визначення показникА поглинання світла мікрочастинками ПОРОШКУ Люмінофора YAG:Сe3+ та її технологічне забезпечення

The development of methods for photometric control of turbid media based on YAG:Ce3+ phosphor (luminophore) microcrystals in transparent matrices requires solving a number of technological problems in the manufacture of self-supporting films of the composite material, adequate measurement of their optical properties and calculation of the corresponding values of absorption indices. This general problem is solved in this work by developing original measuring equipment, elaborating a number of technological protocols and a calculation algorithm based on modelling in the concept of a composite film of a dispersion medium. It is proved that the production of a suspension of microparticles of YAG:Ce3+ powder in epoxy resin at reduced pressure using an original turbine microstirrer allows to obtain a homogeneous and degassed suspension with a low rate of solid particle deposition, efficient light absorption of excitation radiation and an increased level of quantum yield of luminescence. A methodology for manufacturing self-supporting films from the obtained suspension has been developed. Such films are characterised by a low scatter of colourimetric parameters on the surface due to their high spatial homogeneity. 5 ml of the suspension is enough to produce a set of 30 flat-parallel films with an area of up to 1 cm2 and a thickness of 110÷600 µm with an error not exceeding ±3 µm. On the basis of the matrix spectroradiometer НAAS-2000, a photometric measuring setup was developed and created, which, in addition to the spectroradiometer, includes an optical module and an LED blue light source with λmax= 456 nm to excite the luminescence of the light-converting composition layers. The elements of the optical module ensure that the solid angle of the source radiation corresponds to the numerical aperture of the receiver (Ω = 0.126 steradian) in the form of the end window of the fibre-optic cable of the spectroradiometer and cause the transmission of the image on a 1:1 scale. An algorithm for determining the volumetric and linear absorption coefficients of a microcrystal-averaged YAG:Ce3+ phosphor powder under conditions corresponding to the isotropic scattering mechanism was proposed and worked out. Calculations in the composite film model, which takes into account the effects of light absorption and reflection by individual microcrystals in the volume of a transparent matrix, using the results of experimental measurements, allowed us to establish the values of the volume and linear absorption coefficients of the size-averaged (5.3 μm) YAG:Ce3+ microcrystal, which are 774 cm-1 and 129 cm-1, respectively.

X-ray photoemission and absorption spectroscopy of a hypervalent iodine compound, 2-iodosobenzoic acid

To apply a hypervalent iodine compound, 2-iodosobenzoic acid (IBA), to a protecting group of X-ray activated caged compounds, X-ray photoemission and absorption spectroscopy of IBA were performed. The photoemission spectrum of IBA in the valence band region included a component originating from the π*-like orbitals of I-C and I-O. Such characteristic electronic structures may cause the reactivities of IBA. The linear absorption coefficients of the peaks in the iodine K-edge energy region were 38.8, 40.0, and 39.41 cm−1 at around 33.18, 33.23, and 33.32 keV, respectively. Those contribute to discussing reactions of IBA induced by the iodine K-shell excitations quantitatively.

Validating experimental data for attenuation coefficients of developed polymer composites in shielding applications through Monte Carlo simulation

Abstract The widespread use of composites in an ionizing environment raises durability concerns, particularly when performance is required over a longer period, in a radiation environment. The goal of this study was to measure the attenuation coefficient for the polymer composite developed for the radiation shielding application and validate it with the well-known Monte Carlo simulation. A radiation-hardened epoxy resin was developed in the laboratory by utilizing various compositions which is capable of being employed as a shielding material in a nuclear environment. To develop a radiation-hardened layer, to some extent, raised the density of the material, using suitable fillers. Polymer stabilizers were used single or in combination. The specimens were irradiated to determine the developed material’s shielding properties. The prepared composites’ radiation absorption is evaluated using an absorption coefficient. Experiments with gamma radiation using an Am Be Neutron source were conducted to determine the linear absorption coefficient. Monte Carlo simulation was utilized to predict the absorption coefficient for developed composites and the results were compared with experimental data.

Linear and nonlinear electric and magneto-optical absorption coefficients and relative refractive index changes in WxMo1−xS2 monolayer: Role of tungsten contents

In this work, we study the electric and magneto-optical absorption coefficients (ACs) and relative refractive index changes (RRICs) in W[Formula: see text]Mo[Formula: see text]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[Formula: see text]Mo[Formula: see text]S2 in future nanoscale electronic and magneto-optical devices.

Linear and nonlinear optical absorption coefficients in InGaN/GaN quantum wells: Interplay between intense laser field and higher-order anharmonic potentials

This computational investigation delves into the electronic and optical attributes of InGaN/GaN nanostructures subjected to both harmonic and anharmonic confinement potentials, coupled with the influence of a nonresonant intense laser field (ILF). The theoretical framework incorporates higher-order anharmonic terms, specifically quartic and sextic terms. The solutions to the Schrödinger equation have been computed employing the finite element method and the effective mass theory. Moreover, linear and third-order nonlinear optical absorption coefficients are derived via a density matrix expansion. Our analysis reveals the feasibility of manipulating electronic and optical properties by adjusting confinement potential parameters, system attributes, and laser field intensity. In addition, the ILF induces remarkable modifications, characterized by reduced resonance peak amplitudes and a blue shift in absorption coefficients. Intriguingly, regardless of potential harmonicity, the impact of incident electromagnetic intensity is notably more pronounced in the absence of the ILF. These findings hold significant promise for advancing theoretical predictions, providing valuable insights into the intricate interplay between confinement potentials, laser fields, and their effects on electronic and optical behaviors within nanostructures.

Measuring the linear optical absorption coefficient by interferometry and the thermal lensing effect: a numerical analysis

We report on a pump-probe thermal lensing method for measuring the linear absorption coefficient of liquids by using interferometry and numerical analysis. The method is based on interferograms generated when a localized photothermal effect is induced in the sample. The photothermal effect itself is induced by a pump beam impinging on a sample located on-axis of the probe beam, which is one of the paths of a Mach-Zehnder interferometer. A digital camera is employed as the acquisition device allowing the capture and storage of the experimental data. During the experiment, a total of three photographs are taken and stored on a personal computer, and by using an algorithm, the numerical analysis is done. Numerical analysis is subsequently used to calculate the photothermal phase difference and the normalized spatial distribution of the pump beam irradiance. Plotting the phase difference as a function of the spatial distribution of the pump beam produces a linear dependence from which the linear absorption coefficient is obtained. The sensitivity of the method (λ/1500) is validated using ethanol, methanol, and carbon disulfide.

Computational investgation of the optical properties of GaAs/Ga0.7Al0.3 Core/Shell Thin Film for optoelectronic Applications: under tuned external field and impurity effects

This study provides valuable insights into the optical properties of GaAs/Ga0.7Al0.3As core/shell quantum disks, including optical transitions, oscillator strength, linear optical absorption coefficient, and refractive index. We investigate these properties by employing the finite difference method. The Schrödinger equation has been solved within the effective-mass theory. However, our results reveal that adjustments in core/shell radii and electric field direction induce red-shifted resonance peaks, accompanied by improved magnitudes. Furthermore, strategically placing impurities within the core–shell region substantially enhances these optical properties. These discoveries carry the potential to catalyze groundbreaking progress and unveil fresh opportunities for technological innovation in the realm of nanostructured semiconductor devices.

Measurement of Non-Linear Optical Absorption of PVC/TiO2 Nanocomposite via Z-Scan Technique for Optical Limiting

Abstract: This research focuses on PVC/TiO2 nanocomposites in the form of thin films in order to expand our understanding of photonics technology. For fabrication of the thin films, the casting method was used with nanocomposites composite were developed by mixing TiO2 nanoparticles with Polyvinyl Chloride (PVC) as the polymer matrix. The absorbance parameters were determined using spectral analysis, and the linear absorption coefficient was computed. A single beam Z-scan technique was used to evaluate the nonlinear refractive index and nonlinear absorption coefficient via a CW diode pumped solid state (DPSS) laser (Coherent Verdi-V5, 532 nm) was employed as the excitation laser at 50mW. Peak absorption was detected at 280 nm with increasing absorption observed as the proportion of TiO2 nanoparticles increased. The nonlinear absorption coefficient was found at (0.5342, 1.3585,1.5999, and 0.0253) 1ݔ 10−5 cm/W. All of the sample morphology resulting poor structure which then affect the NLO absorption of the materials. However, with the positive value of NLO absorption, they appear to be promising candidates for optical limiting applications.