Total Absorption Coefficient Research Articles

The total absorption coefficient and refractive index change of a spherical quantum dot in the confinement radial potential

We have systematically investigated the linear, third-order nonlinear, total absorption coefficients and refractive index change of the spherical quantum dot in the confinement potential family V(r)=Ar2−Br+Crκ by solving the radial Schrödinger equation with the Numerov method in case of the effective mass approximation for the allowed transition of the ground state (1s) to first excited state (2p). We examine the dependencies of the total absorption coefficient and refractive index change on the confinement potential parameters for varying incident photon energy and relaxation times. Our results demonstrate that the absorption coefficients and the change in refractive index strongly depend on the confining potential parameters non-linearly representing various intersubband transitions of quantum dots. We find that increasing the parameter B in the Coulomb plus harmonic oscillator potential or decreasing the parameter A in the Kratzer plus harmonic oscillator potential, the total absorption coefficient and refractive index change shift to higher photon energies.

On the measurement of remote sensing reflectance by a traditional above-water approach in small water bodies.

Small water bodies are an important part of the Earth's freshwater system, protecting biodiversity and providing ecosystem services. Because of various surrounding features, it is unknown to what extent we can obtain accurate remote-sensing reflectance (Rrs) of such an environment by the conventional above-water approach (AWA). In this study, we used both AWA and the skylight-blocked approach (SBA) side-by-side to measure Rrs in a typical small water body. It was found that the variation of Rrs in the UV-blue domain from AWA is around 50% and is inconsistent with the variation of the total absorption coefficient (at) obtained from water samples; on the contrary, the variation of Rrs obtained from SBA is highly consistent, with a coefficient of variation under ∼5%. These results highlight the large uncertainties in the measured Rrs from AWA due to the complexity of such an environment and further echo the robustness of SBA to measure Rrs in the field, even in such challenge environments.

The effect of structure parameters and static electric field on the nonlinear optical properties of triple InGaAs/GaAs quantum well

Optical properties of InxGa1-xAs/GaAs triple QW are studied for different quantum well thicknesses and external electric fields. The effective mass approximation is used to calculate the band alignment of the structure. The finite difference method (FDM) is applied to solve the 1D- Schrödinger equation. Intersubband energies and the total optical absorption coefficients (TOACs) and total relative refractive index changes (RRICs) are numerically calculated under the applied external electric field. The structure parameters and applied electric field cause the separation of the energy levels and variation of the dipole moment matrix elements. These separations are responsible for the resonant peak shifts. It is shown that the varied structure parameters and external electric field cause red or blue shifts in the resonant peak position of TOAC and RRIC coefficients.

Investigation of linear and nonlinear optical absorption coefficients and refractive index changes of a zigzag quantum well with structure parameters and applied external fields

In this study, we have investigated some linear and nonlinear optical properties of GaAs/GaAlAs zigzag quantum well structures under different electric and magnetic field intensities. We also examined the effect of adjustable structural parameters as well as width on the optical response of the system. The diagonalization method has been the tool to numerically solve the effective mass approximation Schrödinger equation obtaining the energy levels and related wave functions needed to evaluate the expressions of linear, third-order nonlinear, and total optical absorption coefficients and relative refractive index changes derived within the compact density matrix method. Results show that the optical response becomes blue-shifted with the applied electric and magnetic fields’ increment.

Spatiotemporal variability in bio-optical characteristics of the southwestern tropical Indian Ocean during boreal summer: Biophysical influences

The bio-optical characteristics of the surface ocean play a pivotal role in radiative transfer and photosynthetic carbon fixation. To examine spatiotemporal variability of bio-optical properties in the tropical Indian Ocean, a 10-day time-series comparative study was made at one fixed and 3 variable stations in the southwestern tropical Indian Ocean (SWTIO), and 4-stations in the Equatorial Indian Ocean (EIO) during June 2014. A total of 24 hyperspectral radiometer profiles were collected along with physicochemical parameters and phytoplankton pigments analysis. A negative sea level anomaly (SLA), higher precipitation, a more stable mixed layer, and higher buoyancy frequency (N2) were observed in SWTIO compared to EIO. The deep chlorophyll maxima (DCM) in SWTIO were characterised by deep biomass maxima (DBM) whereas in the EIO it was due to deep photoacclimation maxima (DAM). The photosynthetically available radiation (PAR) profiles were obtained by integrating downwelling irradiance from 400 to 700 nm suggesting that the SWTIO had a greater abundance of optically active substances (OAS) than the EIO. Surface chlorophyll a (Chl-a) was found to have significant relationships with phytoplankton absorption coefficient (aph(443)). Chl-a-specific phytoplankton absorption coefficients (a*ph(443)), total absorption coefficient (at(443)), and particulate backscattering (bbp(555)) were also related to Chl-a implying that the phytoplankton was in growth/active phase. The time-series variability of the phytoplankton and changes in the photosynthetic pigments (PSP) to photoprotective pigments (PPP) ratio at SWTIO suggested phytoplankton community shift during 5th to 7th days. Microplankton percent-abundances showed distinct linear relationships with Chl-a and bbp(555) implying that carbon fixation per unit Chl-a was higher in microplankton than in nano and picoplankton at SWTIO. The in situ Chl-a, aph(443), adg(443), Kd(490) and C¯pd were used to validate the various empirical algorithms available as well as the satellite-retrieved data. The MODIS and VIIRS data correlated moderately. This study would help towards improving regional optimized algorithms for OAS and provide a baseline understanding of the scale of variability of primary production and carbon flux from space. In addition, this would contribute valuable bio-optical data from an under-sampled geographical area.

Spectral features and optical absorption of vertically stacked V-groove quantum wires

The spectral features and the linear, nonlinear, and total optical absorption coefficients of two realistic mathrm {GaAs/Ga}_{1-x}{mathrm{Al}}_x{mathrm{As}} vertically stacked V-groove quantum wires confining electronic states were theoretically studied. The compact density matrix formalism and the finite element method were used as solution frameworks. The influence of the barrier width, inter-sidewall angle, the crescent thickness of the stack, and the influence of a static electric field on the energy spectrum and the optical coefficients is addressed. Increasing the crescent thickness (inter-sidewall angle) leads to a reduction (non-monotonous increase) of the energy values, while the presence of a static electric field leads to controllable stark-like patterns. In all cases, anti-crossing points are reported. By increasing the crescent thickness, inter-sidewall angle, or barrier width, a non-monotonous blue-/red-shift of the resonant peaks of the optical absorption is observed. In addition, the results in asymmetric/symmetric vertically coupled V-groove quantum wire systems suggest that the quantum tunneling phenomenon can be linked to the enhancement of the total optical absorption due to the possibility of the generation of dipole moments by higher electron mobility. Thus, optical fields oriented along the growth direction enhance the optical absorption. Furthermore, the absorption coefficient maximum is drastically modified by varying the inter-sidewall angle, and even the evolution tendency can be inverted due to the anti-crossing points in the energy spectra. Since the obtained resonant peaks are located below 20 meV in the spectra, the analyzed system could be interesting for exploring and designing new Terahertz devices.

The nonlinear optical properties of GaAs/GaAlAs triple quantum well: Role of the electromagnetic fields and structural parameters

Being relevant to the field of device applications, multiple semiconductor quantum wells are systems that exhibit remarkable optical and electronic properties. These can be properly tuned by suitably modifying the composition, structural parameters, and the application of external probes. Here, the electronic and optical properties of a GaAs/GaAlAs triple quantum well have been investigated under the influence of applied electric and magnetic fields, as well as the change of well and barrier widths. We have used the diagonalization method to numerically solve the Schrödinger equation under the effective mass approximation for obtaining the subband energy levels and related electronic wave functions. The expressions used for evaluating linear, third-order nonlinear, and total optical absorption coefficients (TOACs) and relative refractive index changes (RRICs) were previously derived within the compact density matrix method. According to our results, whilst an increment in the applied electric field causes a red shift in TOACs and RRICs, a blue shift of the optical responses occurs with increasing the applied magnetic field. Besides, a blue shift is observed as well by changing the width of the central well (LwL), whilst a red shift is noticed when changing left and right wells (LwL and LwR) and barrier (LbL and LbR) widths for zero fields. We believe that our study could make a contribution to designing new quantum-well-based optoelectronic devices.

Nonlinear optical characteristics of thermodynamic effects- and electric field-triggered Mathieu quantum dot

In this work, the total refractive index (TRICs) and total absorption coefficients (TACs) of a spherical quantum dot with the Mathieu potential encompassement, generated by using InxGa1−xAs/GaAs heterostructure, and including hydrogenic impurity in its center, under the influence of the temperature, hydrostatic pressure and external electric field are investigated. The compact density matrix formalism and the iterative method are employed to compute the nonlinear optical features. The relevant eigenvalue equation of the Mathieu quantum dot (MQD) is solved by constructing a tridiagonal matrix formalism, within the effective mass approach. As well as the response of TRICs and TACs to external parameters, the alterations concerning structure parameters such as doping concentration and restriction width are also examined. To the best of our knowledge, the external influences and structural parameters on the optical specifications of MQD containing the central impurity are theoretically taken into consideration, for the first time, in the present work. Determining the optimality of optical properties arising from structural and external parameter changes is crucial in terms of providing a theoretical basis for the experimental production and practical use of MQD.

Concentrations and light absorption properties of PM2.5 organic and black carbon based on online measurements in Lanzhou, China

To elucidate the variations in mass concentrations of organic carbon (OC) and black carbon (BC) in PM2.5 and their light absorption characteristics in Lanzhou, we conducted one-year online measurements by using a newly developed total carbon analyzer (TCA08) coupled with an aethalometer (AE33) from July 2018 to July 2019. The mean OC and BC concentrations were 6.4 ± 4.4 and 2.0 ± 1.3 µg/m3, respectively. Clear seasonal variations were observed for both components, with winter having the highest concentrations, followed by autumn, spring, and summer. The diurnal variations of OC and BC concentrations were similar throughout the year, with daily two peaks occurring in the morning and evening, respectively. A relatively low OC/BC ratio (3.3 ± 1.2, n = 345) were observed, indicating that fossil fuel combustion was the primary source of the carbonaceous components. This is further substantiated by relatively low biomass burning contribution (fbiomass: 27.1% ± 11.3%) to BC using aethalometer based measurement though fbiomass value which increased significantly in winter (41.6% ± 5.7%). We estimated a considerable brown carbon (BrC) contribution to the total absorption coefficient (babs) at 370 nm (yearly average of 30.8% ± 11.1%), with a winter maximum of 44.2% ± 4.1% and a summer minimum of 19.2% ± 4.2%. Calculation of the wavelength dependence of total babs revealed an annual mean AAE370-520 value of 4.2 ± 0.5, with slightly higher values in spring and winter. The mass absorption cross-section of BrC also exhibited higher values in winter, with an annual mean of 5.4 ± 1.9 m2/g, reflecting the impact of emissions from increased biomass burning on BrC concentrations.

Effects of hydrostatic pressure and temperature on the nonlinear optical properties of GaAs/GaAlAs zigzag quantum well

ABSTRACT We have examined theoretically how the temperature and the hydrostatic pressure affect the total optical absorption coefficients, the total refractive index changes, and the second harmonic generation coefficients for GaAs/GaAlAs zigzag quantum well structure. The diagonalisation method and the effective mass approximation have been used to obtain the numerical solution of the Schrödinger equation and energy levels, respectively. The analytical expressions of the optical properties were obtained by using the compact density matrix and iterative methods. When the temperature (hydrostatic pressure) is increased, the resonant peaks’ positions of the total optical absorption coefficients and the relative refractive index changes are shifted to higher energies/blueshift (lower energies/red-shift) with amplitude increment (decrement). Additionally, the resonant peak position of the second harmonic generation coefficient shifts to higher energies/blueshift (lower energies) and also decrease (increase) in magnitude with increasing temperature (hydrostatic pressure).

Quantitative Evaluation of the Phase Function Effects on Light Scattering and Radiative Transfer in Dispersed Systems

The light scattering properties of particles play important roles in radiative transfer in many dispersed systems, such as turbid atmosphere, ocean water, nanofluids, composite coatings and so on. As one of the scattering property parameters, the scattering phase functions of particles are strongly dependent on the particle size, size distribution, and morphology, as well as on the complex refractive indices of the particles and surrounding media. For the sake of simplicity, the empirical phase function models are widely used in many practical applications. In this work, we focus on the radiative transfer problem in dispersed systems composed of spherical particles, and give quantitative analyses of the impact of scattering phase functions on the radiative transfer process. We fit the scattering phase functions of four different types of practical dispersed systems using four previously proposed empirical phase function models, including the Henyey–Greenstein (HG) model, Cornette Shanks (CS) model, Reynold and McCormick (RM) model and two-term Reynolds–McCormick (TTRM) model. By comparing the radiative transfer characteristics (i.e., hemispherical reflectance, hemispherical transmittance and total absorptance) of dispersed layers calculated using the Monte Carlo method, the relative errors caused by using the empirical phase functions are systematically investigated. The results demonstrate that the HG, CS and RM models cause obvious errors in the calculation of hemispherical reflectance in many cases. Meanwhile, the induced errors show no obvious regularity, but are related to the particle size and layer optical thickness. Due to the good fitting effect in both forward and backward directions, the TTRM model provides significantly higher performances in fitting the phase functions of all considered cases than the widely used single-term parametrizations. Moreover, for different particle sizes and layer optical thicknesses, the induced errors of the TTRM model in radiative transfer characteristics are very small, especially for the case of polydisperse particles. Our results can be used to guide the design, analysis and optimization of dispersed systems in practical optics and photonics applications.

Effects of Applied Magnetic Field on the Optical Properties and Binding Energies Spherical GaAs Quantum Dot with Donor Impurity.

The screened modified Kratzer potential (SMKP) model is utilized to scrutinize the impacts of an applied magnetic field (MF) on the binding energies and linear and nonlinear optical properties spherical GaAs quantum dot with donor impurity (DI). To accomplish this goal, we have used the diagonalization method to numerically solve the Schrödinger equation under the effective mass approximation for obtaining the electron energy levels and related electronic wave functions. The expressions used for evaluating linear, third-order nonlinear, and total optical absorption coefficients and relative refractive index changes were previously derived within the compact density matrix method. It has been shown here that the MF and DI impacts the characteristics of the absorption coefficients and the refractive index changes. This study’s results will find application in optoelectronics and related areas.

Remote Estimation of the Particulate Phosphorus Concentrations in Inland Water Bodies: A Case Study in Hongze Lake

Phosphorus is the most important nutrient associated with lake eutrophication and changes in cyanobacterial blooms, and particulate phosphorus (PP) is the main form of phosphorus found in highly turbid inland waters. Therefore, it is urgent to monitor PP concentrations in inland water bodies. In this study, we take Hongze Lake as the research area and establish a semianalytical model to estimate PP concentrations based on the total particle absorption coefficient (ap); the mean absolute percentage error (MAPE) and root-mean-square error (RMSE) values, which indicate the model accuracy, were 14.90% and 0.009 mg/L, respectively. In addition, the construction process and parameter selection criteria of the remote sensing-based PP concentration estimation model were derived using remote sensing data obtained at different spectral resolutions. Sentinel 3 Ocean and Land Color Instrument (OLCI) and Landsat 9 Operational Land Imager version 2 (OLI-2) data were selected as representatives to verify the accuracy of the model; compared to these two datasets, the MAPE values of the models were 16.32% and 26.84%, respectively, while the RMSE values were 0.010 mg/L and 0.014 mg/L, respectively. Finally, the models were applied to Sentinel 3 OLCI and Landsat 9 OLI-2 images obtained on 16 January 2022. The results show that the spatiotemporal distributions of PP concentrations in Hongze Lake estimated from these two images were relatively consistent, but the OLI data reflected overestimations and underestimations in some areas. These research results provide a new methodology for estimating PP concentrations through remote sensing methods and help to further improve the accuracy of remotely sensed PP concentration estimations in inland water bodies.

Linear and nonlinear optical properties in spherical quantum dots: Modified Möbius squared potential

The optical properties of quantum dots (QDs) in modified Möbius squared (MMS) potential are studied. To obtain the energy expressions and the wave functions, we solved the Schrödinger equation by using Nikiforov-Uvarov (NU) method. We investigated the linear, third-order nonlinear and total absorption coefficients (AC) and refractive index changes (RIC) using the density matrix. The numerical results show that the structure parameters and optical intensity have a strong influence on AC and RIC.

Phenomena of Absorption of Soft and Hard Components of Space Rays in the Atmosphere in Yerevan Conditions

The article examines the angular distribution of cosmic ray intensity and identifies the triads using two different empirical formulas for their distribution. The total absorption coefficient of soft and hard components was measured.

The impact of hydrostatic pressure and temperature on the binding energy, linear, third-order nonlinear, and total optical absorption coefficients and refractive index changes of a hydrogenic donor impurity confined in GaAs/AlxGa1−xAs double quantum dots

The impact of hydrostatic pressure and temperature on the binding energy, linear, third-order nonlinear, and total optical absorption coefficients and refractive index changes of a hydrogenic donor impurity confined in GaAs/AlxGa1−xAs double quantum dots

Charge-current generations and optical specifications of Gaussian quantum dot with energy-dependent potential

We consider the energy-dependent quantum dot with GaAs/GaAlAs Gaussian potential encompassment. Depending on the experimental or theoretical results for different types of interactions, the energy dependency can also be chosen as quadratic, fractional or any other type. The solutions of the wave equation for the energy-dependent Gaussian quantum dot are performed numerically by employing the Runge-Kutta-Fehlberg method. The optical specifications of the structure are examined by using the compact-density-matrix formalism within iterative method. The total refractive index changes, the total absorption coefficients, the charge-currents and the induced magnetic fields are studied for different values of the energy dependency parameter.

An optical water classification and quality control model (OC_QC model) for spectral diffuse attenuation coefficient

Spectral diffuse attenuation coefficient of down-welling irradiance (Kd(λ)) is a fundamental optical parameter for water color and of significance for heat budget calculation, photosynthesis modeling and carbon sequestration. Uncertainties exist in both in situ measured and satellite derived Kd(λ), therefore, evaluation of its data quality is essential. In addition, optical water classification of Kd(λ) is still limited. To address these issues, we proposed an optical water classification and quality control model (OC_QC model) based on a globally collected high-quality in situ Kd(λ) data. The model consists of the reference Kd(λ) spectra for 7 optical water types (OWT, ranging from clear open ocean water to highly turbid water) and a scoring system. An individual Kd(λ) spectrum can be assigned an OWT and quality control score (QC score) with this model. The performance of the OC_QC model is tested with independent in situ Kd(λ) spectra from the turbid coastal water (Bohai Sea) and clear oceanic water (Indian Ocean). Questionable or erroneous Kd(λ) spectra can be identified, suggesting the model’s robustness. The model was also evaluated with the Medium Resolution Imaging Spectrometer (MERIS) Level-2 and the Moderate Resolution Imaging Spectroradiometer (MODIS) Level-3 Kd(λ) data in the Bohai Sea, Yellow Sea, East China Sea and South China Sea. Satellite derived maps clearly showed the spatial and temporal variations of OWTs and QC scores, and the regions of low-quality Kd(λ) were reasonably extracted. Global maps of Kd(λ)-based optical water types and corresponding QC scores were also obtained with OC_QC model. With the quality controlled Kd(λ) data, the retrieval accuracy of Secchi disk depth was improved. The retrieval accuracies of Chlorophyll-a concentration and total seawater absorption coefficient were also improved with the Kd(λ) optical water classification based algorithms. The OC_QC model would be valuable for evaluating Kd(λ) data (especially the operational global Kd(λ) products), investigation of water optical properties, and development and merging of bio-optical algorithms.

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.

Optical absorption in core-shell quantum antidot under applied co-directed electric and magnetic fields

Using the matrix diagonalization method within the effective mass approximation and the rectangular potential profile, we investigate optical absorption coefficients (OAC) in the core-shell quantum antidot (QAD) Al0.3Ga0.7 As/GaAs/Al0.3Ga0.7 As in the presence of applied co-directed electrical and magnetic fields. The electric field effect on the electron wave functions, energy spectrum, oscillator strength of the intersubband electronic transitions is calculated for different size of QAD core and different value of the magnetic field induction. The total, linear and nonlinear optical absorption coefficients in QAD are obtained by considering 1 s-1p and 1p-1d electron quantum transitions as functions of the incident photon energy.