Total Refractive Index Research Articles

Evaluation of the external electric- and magnetic field-driven Mathieu quantum dot’s optical observables

In this study, for the first time, the total refractive index changes (TRICs) and total absorption coefficients (TACs) of the quantum dot including the Mathieu potential confinement formed by the InxGa1−xAs/GaAs heterostructure under the influence of external electric and magnetic fields are theoretically investigated. The spectra and eigenfunctions of the Mathieu quantum dot are obtained using the effective mass approximation by forming a tridiagonal matrix formalism. The iterative method and compact-density-matrix formalism are used together to examine the nonlinear optical properties of the Mathieu quantum dot. Throughout the study, the effects on the TRICs and TACs of the external electric and magnetic field, as well as the In concentration and confinement width, are probed. Considering the strong and weak regimes of the external electric and magnetic fields, their alternatives to the structural parameters in terms of optical properties are also evaluated. The increment of the In concentration causes the quantum dot encompassment to turn into the opposite character after a certain radial distance. This result may be remarkable in terms of experimental applications. Under certain conditions, the incident optical intensities photons on the structure are determined at the limit values. As well as determining the functional range of the Mathieu quantum dot in terms of the TRICs and TACs characters, using both structure parameters and external fields and as a function of the incident photon energy, the determination of the optimum for these characters is an important theoretical gain in terms of providing a prediction for experimental studies.

Formulation and Evaluation of Expectorant activity of Poly Herbal Cough Syrup from Traditional Medicinal Plant extracts of North East India

Poly Herbal formulation composed of multi components which produce synergistic effect apart from boost up of body natural immunity. Plants material may contains polysaccharide, mucilage and tannin which are responsible for the synergism of “active principles”. The Poly herbal cough syrup was prepared by mixing of extracts from five different plants namely Ocimum sanctum, Adhatoda vasica, Cinnamomum verum, Cardamomum subulatum and Ephedra sinica in a syrupy base. The evaluation of the formulation was done by determining different physical parameters such as pH, surface tension, total solid content, specific gravity, viscosity, refractive index and expectorant activity of the cough preparation was done on phenol red induced mice model. The pH, surface tension, total solid content, specific gravity, viscosity and refractive index were found to be 4.82, 54.32 dynes/cm, 38.20% w/v, 1.324 (at 250C), 4.68cp and 1.43 respectively. There was a significant increase (P<0.001) in expectorant activity of the formulation at the doses of 300mg/kg and 600mg/kg as compared to the control group. So the herbal formulation could be used to alleviate mucous secretion from bronchial tract.

Regulation of optical properties by applied external fields for a quantum well with Hulthen potential

In this present study, the effects of electric, magnetic, and non-resonant intense laser field (ILF) on the linear, third-order nonlinear, and total optical absorption coefficients (TOACs) and relative refractive index changes (RRICs) of GaAs quantum well, having Hulthen confinement potential, were theoretically investigated. In addition, the dependence of the nonlinear optical properties in the structure on the optical intensity of incident photon and the inverse relaxation time was also calculated. To do this research, firstly the energy eigenvalues and eigenfunctions of the structure were calculated by using the effective mass and envelope function approaches. By using these calculated subband energy levels and wave functions belonging to these levels, the nonlinear optical properties of the system were obtained via the iterative method, within the compact density matrix approach framework. The obtained numerical results show that the optical properties of the considered system depend on the externally applied fields. With the applied external electric and magnetic field, the peak positions of TOACs and RRICs shift to higher energies, and the peak magnitudes increase. The high-frequency ILF applied to the structure shifts the peak positions of TOACs and RRICs initially towards higher energies and then towards lower energies and their peak sizes increase. These results show that the optical properties of the system can be adjusted purposively by changing the magnitude of applied external fields.

Terahertz laser field manipulation on the electronic and nonlinear optical properties of laterally-coupled quantum well wires.

An intense terahertz laser field is shown to actively manipulate the electronic states, as well as the linear and nonlinear optical absorption coefficients, of the laterally-coupled quantum well wires (LCQWWs). The laser-dressed quantum states of the LCQWWs are achieved using the non-perturbative Floquet method and the two-dimensional diagonalization technique under the effective mass approximation. We have demonstrated that the intense terahertz laser field induces a strong deformation of the confinement potential configuration of the LCQWWs, thus pronouncedly dressing the energy levels and wave functions. An unambiguous picture is depicted for the evolution of the laser-dressed quantum states with the increase of the laser-dressed parameter characterizing the strength of the laser-dressed effect. On this basis, the resonant peak positions of the linear and nonlinear optical absorption coefficients feature a blue shift followed by a red shift with an increase of the laser-dressed parameter. Furthermore, the evolution of the peak values for the linear and third-order nonlinear optical absorption coefficients as a function of the laser-dressed parameter is comprehensively discussed. Moreover, in contrast to the case without intense terahertz laser field, the peak values of the linear, third-order nonlinear, and total optical absorption coefficients can be obviously enhanced at the same frequency position by manipulating the appropriate laser-dressed parameter. A similar feature can be found in the linear, third-order nonlinear, and total refractive index changes. Our findings are conducive to the implementation of the expected quantum states and nonlinear optical effects in the LCQWWs, paving the way for new designs in tunable optical switches, infrared photo-detectors and infrared modulators.

Oxidative Stability of Avocado and Peanut Oils Under Different Heating Temperatures

The objective of this research was to investigate the effect of heating temperature on the quality parameters of avocado and peanut oils subjected to heating. Vegetable oils were heated at varying temperatures (110, 140, 170, 200 and 230�C for 30 min) to follow quality alterations. Levels of peroxide value, iodine value, thiobarbituric acid reactive substances, total polar compounds, refractive index, free acidity, and fatty acids composition were determined to measure the extent of lipid oxidation. Peroxide value was significantly (p [ 0.001) influenced by heating temperature in the case of peanut oil. Iodine value decreased significantly (p [ 0.01) in both oils with the increase in heating temperature due to the decrease of the unsaturation degree. Avocado oil showed the smallest increase in thiobarbituric acid reactive substances and total polar compounds during heat treatment. The fatty acids profile of peanut oil was rich in polyunsaturated fatty acids with a level of 42%, followed by monounsaturated fatty acids with about 36%. The heat treatment of oils has produced changes in unsaturated fatty acids, these have undergone isomerization from cis to trans form. The increases of heating temperature up to 230�C significantly deteriorated the quality of peanut oil, but to a lesser extent the one of avocado oil.

The Total Absorption Coefficient and Refractive Index Change of a Spherical Quantum Dot in the Confinement Radial Potential

The Total Absorption Coefficient and Refractive Index Change of a Spherical Quantum Dot in the Confinement Radial Potential

A Reversible Moisture-Responsive Plasmonic Color-Raman and Transmittance Modulation Device by Dispersing Hyaluronan-Functionalized Ag into Nanofibers.

Plasmonic physical color generation, which mostly depends on selective absorption, creates unique colors by light transmission and scattering. Based on this, regulating plasmon and transparency with external stimulation is a promising approach for fabricating optical devices with enhanced visual displays; however, few studies have addressed the implementation of dual-optical modulation. In addition, developing a color response to environmental stimuli through the highly shape-sensitive plasmon depth modulation has long remained a significant challenge once the nanostructure is determined. Some stimulations also require high amounts of electricity, which can be costly. In this study, strategically designed hyaluronan-functionalized triangular silver nanoparticles (AgNPs) were embedded in polyvinyl alcohol-polyethylene nanofiber films to achieve a breakthrough in the moisture-responsive dual-optical modulation of the plasmonic color-Raman and transparency. Switchable colors that are reversible were induced in plasmon-resonance-modulation AgNPs via moisture stimulation, adjusting the expansion-tunable dielectric constant of hyaluronan-functionalized AgNPs and varying the electron density due to electron transfer. Furthermore, a moisture gradient was used to decrease the Raman scattering and increase the photoluminescence, which is a significant demonstration of smart-plasmonic evolution. This effect occurred due to the gradual transition from plasmon-driven photoluminescence quenching to photoluminescence enhancement as the interval of the Ag and hyaluronic acid molecules was increased. The transparency of the composite film was also dynamically regulated by turning moisture on/off. This occurred because of the significant difference in hygroscopic expansion between hyaluronan and the nanofibers, which generated a large variation in the total refractive index and caused changes in the surface roughness.

Optical Properties of Gaas/Alxga1-xas Superlattice Under E-Field for Quantum Cascade Laser Application

Optical properties of GaAs/AlxGa1-xAs superlattice are studied dependent on quantum well thickness of gain region and doping density of injector layers underperformed electric field. Conduction band alignment of the superlattice is obtained by using effective mass approximation. 1d-Schrodinger formula is solved by using FDM. Intersubband transition energies, linear (nonlinear and total) absorption coefficients and linear (nonlinear and total) refractive index changes are plotted under applied electric field intensity. Intersubband transition energy of electron from second excited state to first excited state shows 147 meV. It is found that -45 kV/cm electric field intensity and 5 nm layer thickness of last quantum well of the gain region are the best values for studied structure. After that, linear absorption coefficient is investigated dependent on carrier number in the injector region under electric field. It is found that carrier number over 5 𝑥 1016 𝑐𝑚−2 can causes huge internal absorption of the radiative emission obtained in gain region due to increase in linear absorption coefficient by factor 10. As a conclusion, total absorption coefficient and total refractive index change are calculated for optimized parameters.

Linear and nonlinear refractive index changes in monolayer MoSe2

In this work, we study the linear, the third-order nonlinear, and the total refractive index changes (RICs) caused by both intra- and inter-band transitions in monolayer MoSe2 in the presence of a magnetic field by using the compact density matrix approach. The results show that RICs display the blue-shift behavior with the increase of the magnetic field. The Zeeman fields do not affect the peak positions but reduce slightly peak intensities. Besides, the strong spin-orbit coupling in monolayer MoSe2 causes a significant difference in the peak due to spinning up and down. The RICs due to intra-band transition display only one peak in the THz range, while the inter-band spectra show a series of peaks in the near-infrared optical range, making monolayer MoSe2 be a promising candidate for novel optoelectronic applications.

Optical properties of a GaAs quantum well with new type of hyperbolic confinement potential: Effect of structure parameters and intense laser field

In this present study, we have investigated theoretically the effect of structure parameters (η and κ) and high-frequency intense laser field (ILF) on the linear and nonlinear optical properties of a GaAs quantum well (QW) with new type of hyperbolic confinement potential. Within the framework of the effective-mass and parabolic band approximations, we have computed the confined subband energy levels and their corresponding densities of probability by using the diagonalization method. Besides, we evaluated the total optical absorption coefficients (TOACs) and total refractive index changes (TRICs). The obtained numerical findings show that an increase of the η (κ) structure parameter causes an increase (decrease) in amplitude in TOACs and a blue (red) shift of the resonance energy spectrum. In addition, with the increase of the ILF, the resonance energy spectrum shifts to blue, while the amplitude of TOACs (TRICs) increased (decreased). We think that the obtained these results can be useful in the design of new device’s generation employed in optoelectronic domain.

Non-resonant intense laser field effect on the nonlinear optical properties associated to the inter- and intra-band transitions in an anharmonic quantum well submitted to electric and magnetic field

Simultaneous effects of electric, magnetic, and non-resonant intense laser field on the nonlinear optical properties of a GaAs quantum well with an anharmonic confinement potential profile are theoretically investigated. Energy eigenvalues and eigenfunctions of the system are determined using the diagonalization method within the framework of the effective mass and parabolic band approximation. Nonlinear optical properties associated to the inter and intra band transitions are evaluated. Our numerical results for the intra-band response show that the resonance peak positions of the total optical absorption coefficients and relative refractive index changes shift towards higher energy levels (blueshift) by increasing the strength of the applied external electric, magnetic, and non-resonant intense laser field. The analysis of inter-band (electron-heavy hole) transitions reveals that the optical coefficients has a pronounced redshift induced by the electric field while a blueshift is caused by the magnetic and laser signals. It is seen that the nonlinear optical properties of such structures can be adjusted according to the purpose by changing the external perturbations and could be used in new optoelectronic device designs.

Physical and Rheological Properties of Poly-floral Honey from the Iraqi Kurdistan Region and the Effect of Temperature on its Viscosity

Aims: In this study, the physical and rheological properties of three poly-floral honey samples collected from different places in the Kurdistan region were determined. Methods: The honey samples were analyzed for pH, free acidity, total ash content, moisture content, refractive index, soluble solids (Brix), electrical conductivity, volume expansion, density, specific heat capacity, surface tension, and rheological properties. The pH and free acidity of the honey samples varied from 4.10 to 4.81 to 30 to 62 mEq/kg, respectively. The total ash content ranged from 0.166 to 0.408%. The moisture content, soluble solids, and refractive index ranged from 15.60 to 16.60 g/100 g, 83.40 to 84.40, and 1.4998 to 1.5023, respectively. The electrical conductivity ranged from 40.896 to 44.471 mS/cm. The linear relationship between the electrical conductivity and the ash content was also calculated in this investigation. The volumetric expansion coefficient of the honey samples varied from 6.0098x10-4 to 6.69942x10-4 mm3/K. The density ranged from 1.42125995 to 1.45501137 g/cm3. The specific heat capacity varied from 2448.078 to 2575.004 J/kg.K. The surface tension varied from 0.2178 to 0.2282 N/m. The apparent viscosity was measured by Brookfield Viscometer, and the dynamic viscosity was measured by HAAKE Falling Ball Viscometer, after changing the temperature from 293 to 323 K. Results and Discussion: The honey samples of lower moisture content showed a greater increase in their apparent and dynamic viscosities. Arrhenius model was used to describe the effect of temperature on the honey viscosity. This model was used to determine the activation energy. Other rheological properties such as kinematic viscosity and fluidity, were also determined. Conclusion: All the honey samples behaved as Newtonian fluids in the whole temperature range.

Theoretical investigation of linear and nonlinear optical properties in an heterostructure based on triple parabolic barriers: Effects of external fields

In this work, we have investigated theoretically the impact of intense laser, electric and magnetic fields on the linear and nonlinear optical properties of a quantum well heterostructure containing triple parabolic barriers (GaAs/AlGaAs). Within the framework of the effective-mass and parabolic band approximations, we have computed the confined lowest energy levels and their corresponding densities of probability, through the use of a finite difference technique to solve the corresponding differential equation. Besides, we evaluate the total optical absorption (TOACs) and relative refractive index change (RRICs) coefficients. The obtained findings show that an increase of the intensity of the intense laser field produces a blue shift at first and then a red shift of the TOACs and RRICs. A specific value of the laser field separating the two kinds of signal displacements is outlined. Contrarily to the intense laser field, an increment of the external static electric and magnetic fields induces only a blue shift in the variation of the TOACs and RRICs. In addition, we have discussed in detail the variation of diagonal and non-diagonal matrix elements which are responsible on the variation of the amplitudes of the TOACs and RRICs. We think that the obtained results can be useful in the design of new device's generation employed in optoelectronic domain.

Physicochemical properties of Walnuts (Juglans regia L.) shells and kernels growing in different locations in Kurdistan region-Iraq

Some physicochemical properties of walnut shell, kernel and oil of fifteen samples of walnut grown in different locations in Kurdistan region-Iraq were determined. Three principal dimensions such as length, width and thickness, volume and projected area of walnut and its kernels were measured using image processing technique. Based on three principal dimensions, some dimensional properties including geometric mean diameter, arithmetic mean diameter, sphericity, volume and surface area of the nuts and kernels were calculated. Also gravimetric properties of nuts and kernels such as true density of nuts and kernels were studied. Furthermore other physical properties such as weight of nut, weight of kernel, percentage yield of walnut, total oil content, ash contents, moisture contents, pH value, relative density and refractive index of the oils were also determined. The variations in physical properties such as size dimensions, arithmetic mean diameter, geometric mean diameter, unit mass, sphericity, surface area, true density and volume of shells and kernel of walnuts as a function of the moisture content were determined. With an increase in the moisture content, the surface area, sphericity, true density and volume of shells and kernel of walnuts increased. In addition, the oil yields from the kernels had ranged between 36.07% to 70.24%. The moisture contents of shells and kernels ranged between 6.34% to 10.11% and 3.68% to 5.62%, respectively; and the ash content of kernels were ranged between 0.94% to 2.2%. On the other hand, the refractive index of oils were determined between 1.4734 and 1.4767, pH-values of kernel oils were ranged between 6.23 and 7.02 and the relative density were determined between 0.9746 and 0.9801. Finally the present study was showed that the walnut kernels in Kurdistan region did not show any considerable significant variations with reference to their physical and chemical properties.

Optical response of plasma processed quantum dot under the external fields

AbstractWe investigate theoretically the total refractive index changes (TRICs) and the total absorption coefficients (TACs) of two‐electron Gaussian quantum dot (TEGQD) including Gaussian potential confinement generated by GaAs/GaAlAs heterostructure, embedded in Debye and quantum plasma environments modeled by the more general exponential cosine screened Coulomb (MGECSC) potential, under the influence of the external electric and magnetic field. The wave equation is solved within the effective mass approach framework by using Runge–Kutta–Fehlberg method in order to obtain the subband spectra and the electronic wave functions of TEGQD. Nonlinear optical response of TEGQD is obtained through the compact‐density‐matrix formalism within the iterative method. The effects of both Debye and quantum plasma environments in the strong and weak regimes of the external fields are considered and compared throughout the study. The potents of the external electric field, the external magnetic field, the quantum dot width, the barrier height, and the plasma screening on TRICs and TACs resonant frequencies and amplitudes are analyzed. In addition to these analyses, the alternatives to each parameter effects of the model are also elucidated. TRICs and TACs analyze are carried out in a plasma‐free environment, and thus the function of environments with plasma compared to that without plasma is better explained. Thanks to all these reviews, it is elucidated how to and at what ranges perform in terms of the incident photon energy of TEGQD's optimum for TRICs and TACs characters by using plasma, and in which cases it will be an alternative to the external field and geometrical encompassing.

Optical analysis of quantum dot with velocity‐dependent potential

AbstractIn this study, for the first time, the velocity‐dependent potential (VDP) effects on the total refractive index changes (TRICs) and the total absorption coefficients (TACs) of the parabolic quantum dot with spherical confinement, generated by GaAs/GaAlAs heterostructure, are comprehensively investigated. In order to obtain the subband energy spectra and the electronic wave function of the quantum dot system, the wave equation is numerically solved due to the VDP's complexity by using Runge‐Kutta‐Fehlberg method within the effective mass approximation. The nonlinear optical specifications of the quantum dot with velocity‐dependent potential (QDVDP) are analyzed using the compact density matrix formalism within the framework of the iterative method. To investigate the optical specifications of QDVDP, the isotropic form factor of VDP is taken into consideration as the harmonic oscillator type, F(r) = γρ0r2 (being γ and ρ0 are constants). Optical analysis is also executed for parabolic encompassing under the influence of VDP, as well as VDP, analyzing for TRICs and TACs of QDVDP, for which the result is quite a change compared to cases without VDP due to the symmetry‐breaking repercussion on system confinement of VDP. The main motivation of the present study is to clearly distinguish VDP effects on optical properties of the quantum dot, carrying out an analysis on optimal range and alternative parameter for optical properties.

Theoretical modeling of inter-sublevel optical properties of a ZnSe/ZnSxSe1-x and ZnSe/ZnSxSe1-x/ZnS core/shell and core/shell/shell quantum dot

In this work, we have modelling a ZnSe/ZnSxSe1-x and ZnSe/ZnSxSe1-x/ZnS core/shell and core/shell /shell quantum dot (QDs) respectively in the intent to study the effect of the second shell ZnS on the electronic and optical properties. To solve the three dimensional Schrödinger equation, we have used a theoretical method which is combined the coordinate transformation and the finite difference method (FDM). We have evaluated the influence of ZnS shell material, first on the energy eigenvalues and on the transition lifetime, then on the linear, non-linear and total absorption coefficient and refractive index changes. The first linear and third order nonlinear susceptibilities are also investigated.

Control of electronic and optical properties of a laser dressed double quantum dot molecule by lateral electric field

We study the confined states of a molecule formed by two laterally coupled quantum dots. The static electric field and incident plane wave laser field are considered with different polarization. The respective Shrödinger equation is obtained in the framework of the high-frequency limit of Floquet theory. It is shown that the electric field has a qualitative impact on the spatial symmetry of electronic states. An in-depth study of electric and laser field combined effects show a strong correlation between them. Additionally, we show that the linear, nonlinear and total optical absorption coefficients and relative refractive index of the considered structure can be effectively tuned by changing electric field strength and intense laser field parameter. Our results indicate the possibility of controlling the optical response of double quantum dots molecule for future applications in nanostructure-based quantum information science.

Optical intersubband properties of a core–shell semiconductor–topological insulator quantum dot described by θ-electrodynamics

The optical properties of a spherical topological insulator embedded concentrically in a single-electron system consisting of a core-shell GaAs quantum dot are analyzed, when the system is under a uniform external magnetic field. The topological insulator's magnetoelectric response is computed in the effective framework of $\theta$-electrodynamics, which allows analytical calculations for the induced electric and magnetic potentials by Green's Function method. The GaAs Hamiltonian is constructed in the effective-mass approximation, and its corresponding Schr\"odinger equation is numerically solved through the Lagrange-mesh method. We compute the total absorption coefficients and refractive index changes given by the non-linear iterative density matrix formalism up to third order. Our results show that the presence of the magnetoelectric material causes new dipolar transitions otherwise not allowed. Also, an enhancement of the photon absorption is found when the incident light polarization is oriented parallel to the external magnetic field, in comparison with perpendicular polarization. Moreover, we report an appreciable blue shift in the optical functions when the values of the $\theta$-parameter are increased. These results can be useful for indirect experimental measures of the magnetoelectric polarizability which is proportional to the QED fine-structure constant $\alpha$.

Influence of malt modification and the corresponding macromolecular profile on palate fullness in cereal-based beverages

The sensory attribute palate fullness of cereal-based beverages was shown to be affected by polymeric compounds and their macromolecular profile. During malting, the enzymatic degradation of polymers is technologically controlled by the malting parameters, namely the degree of steeping, germination time, and germination temperature. The macromolecular profile of a fermented cereal-based beverage consists of non-fermentable substance classes. Therefore, the macromolecular composition of a final beverage is originally dominated by the raw material, if conventional production methods are used. We investigated the influence of different cytolytic and proteolytic malt modifications on the macromolecular profile of lactic acid-fermented cereal-based beverages (a strain was selected that did not produce exopolysaccharides) and their resultant effect on the sensory perception of the attributes of palate fullness and mouthfeel. Asymmetrical-flow field-flow fractionation coupled with multi-angle light-scattering detection and refractive index detection is an analytical tool for macromolecular characterization to indicate differences in the macromolecular profile, molar mass, and molar mass distribution. The beverages produced using different modified malts demonstrated a considerable variation in their final composition, particularly in the composition of their macromolecular compounds. A higher level of malt modification led to a decrease in the high-molar-mass fraction and a consequent shift toward fractions with a lower molar mass. Malts produced from barley with increased crude protein contents resulted in a greater range within the macromolecular profile. The variation of germination time significantly influenced the number average molar mass, the total refractive index detection (dRI) peak area, and the high-molar-mass fraction, which contained cell wall polysaccharides (60–1200 kDa). The perception of the intensity of palate fullness was significantly correlated with specific macromolecular fractions, which were influenced by the malting parameter degree of steeping and the resultant modification. The perception of the mouthfeel descriptor watery varied significantly for different crude protein contents. Our results are beneficial for a targeted design of beverage composition based on the macromolecular profile by an improved selection of raw materials and malting technology.