Set Of Optical Parameters Research Articles

Computational Investigation of Structural, Electronic and Optical Properties of Ternary Chalcogenide TLGaQ2 Monoclinic Compounds: a First Principle Study

Purpose: This paper aim to investigate and predict by simulation the impact of the substitution of Q-site atom (Q꞊S, Se) on the TIGaQ2 monoclinic compounds for the first time, along the three main polarizations of the incident wave directions [100], [010] and [001]. Theoretical Framework: This study focuses mainly on ternary chalcogenide compounds TlGaQ2 (Q= S, Se) from ABQ2 family to highlight the objective resources aimed at promising prospects offered for them. Design/Methodology/Approach: A series of ab-initio calculations based on the (PW+PP) method within the density functional theory DFT framework were carried out with CASTEP code for the simulation of their physical properties (structural, electronic-optical). The exchange correlation potential was treated within the generalized gradient approximation (GGA) implemented in the CASTEP code and expressed by the PBE functional. Findings: The equilibrium lattice parameters are in good agreement with the available experimental results. The calculated band structure shows that are direct bandgap semiconductor nature 1.92eV (1.41eV) for TlGaS2 and TlGaSe2 respectively with a great potential for photovoltaic solar cell absorber materials. A set of optical parameters were calculated including the complex dielectric function, the reflective index, reflectivity, the absorption coefficient and loss function. The optical properties obtained revealed very interesting optical properties exhibiting strong optical absorption in UV range up to (~2x105cm-1) for both compounds making them appropriate for photovoltaic solar-cell absorber materials. Furthermore, low reflectivity and energy loss function are shown within in the visible and ultraviolet energy range, allowing them to be promising materials in several optoelectronics applications likes photosensitive devices. Implications: All these findings results show a successful accurately prediction for chalcogenide materials behavior and will be helpful for future studies allowing a better understanding of their potential applications in modern photovoltaic technologies as well as within UV ranges for optoelectronics applications.

Optical Characteristics of Rectangular Cross-Section Torus Waveguide

The rectangular cross-section waveguide made of PMMA is designed to efficiently transfer solar radiation from the source to the receiver, whether it be a (solar cell or a thermal reservoir) by the total internal reflection of the radiation within the waveguide. The waveguide is designed with a torus, like the letters U and S, which provides greater flexibility to reach previously inaccessible areas with traditional waveguide shapes. To design the waveguide, the simulation program (ANSYS Zemax OpticStudio 2022) uses the analysis tool in the program (detector viewer). The optical efficiency of the system was calculated by varying a set of optical parameters, such as the radius of curvature of the waveguide, the width of the entrance aperture, and the angle of rotation. The results showed that the designed (U) model offers more design flexibility than the (S) model, enabling greater geometric freedom in solar system design and providing greater diversity in design based on its intended purpose without significantly affecting the efficiency of the system.

A Lightweight Neural Network for Spectroscopic Ellipsometry Analysis

AbstractEllipsometry is a widely used technique in thin film characterizations. To extract the optical properties of the films from the measured data, regression data fitting techniques have been developed that iteratively find a set of optical parameters that best fit the observations. However, this iterative process often faces challenges in converging to the correct solution, and it can be time‐consuming. To address these issues, an 8‐bit quantized lightweight method of neural network analysis for spectroscopic ellipsometry are proposed. This method features compact neural network modules to enhance speed and efficiency. The effectiveness of the approach through experimental verification is validated on a diverse range of material films, including metals, semiconductors, and dielectrics. The approach is fully automatic and lightweight, which offers a new perspective on balancing predictive accuracy with limited computational resources. This method holds the potential to achieve automatic, rapid, and high‐throughput optical characterization of films, facilitating real‐time quality monitoring for repeatable high‐precision film manufacturing.

End-to-end sensor and neural network design using differential ray tracing.

In this paper we propose a new method to jointly design a sensor and its neural-network based processing. Using a differential ray tracing (DRT) model, we simulate the sensor point-spread function (PSF) and its partial derivative with respect to any of the sensor lens parameters. The proposed ray tracing model makes no thin lens nor paraxial approximation, and is valid for any field of view and point source position. Using the gradient backpropagation framework for neural network optimization, any of the lens parameter can then be jointly optimized along with the neural network parameters. We validate our method for image restoration applications using three proves of concept of focus setting optimization of a given sensor. We provide here interpretations of the joint optical and processing optimization results obtained with the proposed method in these simple cases. Our method paves the way to end-to-end design of a neural network and lens using the complete set of optical parameters within the full sensor field of view.

Half metallic ferromagnetism and optoelectronic characteristics of V doped BaTiO3compound: a DFT study

The effect of vanadium (V) doping with various concentrations (x= 12.50%, 25%, 50%, 75%) on the physical properties ofBaTiO3perovskite is examined using the spin polarized theory.The electronic band structure (BS) for both states reveal that all Ba0.875V0.125TiO3, Ba0.75V0.25TiO3,Ba0.5V0.5TiO3 and Ba0.25V0.75TiO3 compounds are half-metallic ferromagnetic (HMF) materials. The results showed that V play a significant role in the HMF behavior ofBa1-xVxTiO3compound. In addition, the magnetic characteristics confirm the integer values of magnetic moment of all mentioned compounds. In optical properties, reflectivity R (ω), optical absorption α (ω), dielectric function ɛ (ω), extinction coefficient k (ω), and refractive index n (ω) are also calculated. The complete set of optical parameters suggests the use of mentioned material in the visible-ultra violet optoelectronics devices. Based on the half metallic (HM) results of V doped BaTiO3 is capable for spintronics applications.

Determination of the complex refractive index of compound semiconductor alloys for optical device modelling

In this paper a method is presented to accurately and quickly interpolate a dataset of the complex refractive index of arbitrary compound semiconductors. The method is based on a parameter morphing algorithm which maps critical points of two endpoint materials with known optical parameter sets onto each other. Every desired intermediate material composition can be interpolated if the composition dependence of the band gap is known for the given material system. The accuracy and stability of the proposed procedure is validated experimentally using spectral ellipsometry and reflection measurements. Test samples of two III–V semiconductor material systems, AlGaAs and GaInAsP, with various compositions were grown using metalorganic vapour phase epitaxy and the morphed parameter sets are compared to corresponding measurement results. Modelling the absorption of a solar cell device and comparing it to the external quantum efficiency is presented as an application example of this method. The interpolation method is demonstrated to be a powerful tool for optical and electro-optical modelling of semiconductor structures if parameters of the complex refractive index are not available for the exact material composition.

First Principle Insight into the Structural, Optoelectronic, Half Metallic, and Mechanical Properties of Cubic Perovskite NdInO3

The structural, optoelectronic, magnetic, and elastic properties of cubic perovskite NdInO3 have been analyzed by spin-polarized density functional theory. The computed values of total energies of the optimized systems reveal that ferromagnetic phase is energetically stable rather than paramagnetic phase of cubic NdInO3 compound. Furthermore, the spin-polarized band structure and density of states elucidate the half metallic nature of the studied material due to a different response of both spin channels; spin-up electrons illustrate metallic character, while spin-down electrons display a direct band gap (M–M) semiconducting behavior. The elastic parameters indicate anisotropic and brittle characteristics; further, the total magnetic moment of the cubic NdInO3 perovskite (3 μB) is mainly due to the Nd site with very feeble contribution of In and O atoms. The complete set of optical parameters demonstrate that cubic NdInO3 is active in visible–ultraviolet region. Based on these results, NdInO3 is categorized as a half metallic ferromagnetic compound, which might be used in spintronics and optoelectronic devices.

Determination of the complete set of optical parameters of micron-sized polycrystalline CH3NH3PbI3−xClx films from the oscillating transmittance and reflectance spectra

The complete set of optical parameters of micron-sized polycrystalline CH3NH3PbI3−xClx films deposited by the vacuum co-evaporation of lead iodide and methylammonium chloride is determined by analysis of oscillating optical transmittance and reflectance spectra in the wavelength range 400–1000 nm. It is shown that for a medium and weak absorption region the envelope method is valid for the extraction of refractive index, extinction and absorption coefficient when is using only transmittance spectra. As well thickness of the film is determined from transmittance and reflectance spectra with interference-effect. The absorption coefficient for the strong absorption region and optical band gap (direct transition at Eopt = 1.62 eV) are calculated based on transmittance and reflectance spectra by using conventional approximated formulas.

Topological complexity of photons' paths in biological tissues.

In the present contribution, three means of measuring the geometrical and topological complexity of photons' paths in random media are proposed. This is realized by investigating the behavior of the average crossing number, the mean writhe, and the minimal crossing number of photons' paths generated by Monte Carlo (MC) simulations, for different sets of optical parameters. It is observed that the complexity of the photons' paths increases for increasing light source/detector spacing, and that highly "knotted" paths are formed. Due to the particular rules utilized to generate the MC photons' paths, the present results may have an interest not only for the biomedical optics community, but also from a pure mathematical point of view.

Freeform off-axis optical system with multiple sets of performance integrations

Freeform optical surfaces make it possible and feasible to design systems with novel functions. In this Letter, a new type of freeform system with multiple sets of performance integrations is proposed, for the first time to the best of our knowledge. The system can operate at different optical parameters for different imaging demands. A movable aperture stop is used in the system for switching between the working areas suited for different sets of optical parameters. A construction method for integrated freeform surfaces is proposed herein, which considers multiple object-image relationships simultaneously. By this method, three integrated freeform systems were designed with different novel functions. This Letter adds more variety to the design of freeform off-axis systems.

Converting the signal-recycling cavity into an unstable optomechanical filter to enhance the detection bandwidth of gravitational-wave detectors

Current and future interferometeric gravitational-wave detectors are limited predominantly by shot noise at high frequencies. Shot noise is reduced by introducing arm cavities and signal recycling, however, there exists a tradeoff between the peak sensitivity and bandwidth. This comes from the accumulated phase of signal sidebands when propagating inside the arm cavities. One idea is to cancel such a phase by introducing an unstable optomechanical filter. The original design proposed in [Phys.~Rev.~Lett.~{\bf 115},~211104 (2015)] requires an additional optomechanical filter coupled externally to the main interferometer. Here we consider a simplified design that converts the signal-recycling cavity itself into the unstable filter by using one mirror as a high-frequency mechanical oscillator and introducing an additional pump laser. However, the enhancement in bandwidth of this new design is less than the original design given the same set of optical parameters. The peak sensitivity improvement factor depends on the arm length, the signal-recycling cavity length, and the final detector bandwidth. For a 4~km interferometer, if the final detector bandwidth is around 2~kHz, with a 20~m signal-recycling cavity, the shot noise can be reduced by 10 decibels, in addition to the improvement introduced by squeezed light injection. We also find that the thermal noise of the mechanical oscillator is enhanced at low frequencies relative to the vacuum noise, while having a flat spectrum at high frequencies.

Исследование упругого рассеяния ионов 15N на ядрах 9Be при Elab=18,75 МэВ

In present work, we measured the angular distributions of elastic scattering of 15N ions on 9Be nuclei at an energy of Elab = 18.75 MeV in the range of angles θ cm from 43 ° to 164 °. The extraction of 15N ion beams was carried out at the Nur-Sultan branch of the INP RK on the DC-60 cyclotron. The particles were detected in the framework of the ∆Е-Е technique using the silicon surface-barrier detectors dE and E from ORTEC, the thickness of which was 8 and 300 microns, respectively. 9Be films with a thickness of about 31 μg / cm2 were used as targets. The purpose of this work was to obtain new data on the parameters of the optical potential for the 15N + 9Be system.The obtained data were analyzed using the Fresco and DFPOT codes, within the framework of the optical model (OM) and the duble folding  method as a result of which several sets of optical parameters were obtained.

Reconstructing Van Gogh\u2019s palette to determine the optical characteristics of his paints

The colors of Field with Irises near Arles, painted by Van Gogh in Arles in 1888, have changed considerably. To get an idea of how this painting, as well as other works by Van Gogh, looked shortly after their production, the Revigo (Re-assessing Vincent van Gogh’s colors) research project was initiated. The aim of this project was to digitally visualize the original colors of paintings and drawings by Vincent van Gogh, using scientific methods backed by expert judgement where required. We adopted an experimental art technological approach and physically reconstructed Van Gogh’s full palette of oil paints, closely matching those he used to paint Field with Irises near Arles. Sixteen different paints were reconstructed, among which the most light-sensitive pigments and linseed oil, which is prone to yellowing, were produced according to 19th century practice. The resulting pigments and oils were chemically analyzed and compared to those used by Van Gogh. The ones that resembled his paints the most were used in the paint reconstructions. Other pigments were either obtained from the Cultural Heritage Agency’s collection of historical pigments, or purchased from Kremer Pigmente. The reconstructed paints were subsequently used to calculate the absorption K and scattering S parameters of the individual paints. Using Kubelka–Munk theory, these optical parameters could in turn be used to determine the color of paint mixtures. We applied this method successfully to digitally visualize the original colors of Field with Irises near Arles. Moreover, the set of optical parameters presented here can similarly be applied to calculate digital visualizations of other paintings by Van Gogh and his contemporaries.

Asymptotic theory of circular polarization memory.

We establish a quantitative theory of circular polarization memory, which is the unexpected persistence of the incident circular polarization state in a strongly scattering medium. Using an asymptotic analysis of the three-dimensional vector radiative transfer equation (VRTE) in the limit of strong scattering, we find that circular polarization memory must occur in a boundary layer near the portion of the boundary on which polarized light is incident. The boundary layer solution satisfies a one-dimensional conservative scattering VRTE. Through a spectral analysis of this boundary layer problem, we introduce the dominant mode, which is the slowest-decaying mode in the boundary layer. To observe circular polarization memory for a particular set of optical parameters, we find that this dominant mode must pass three tests: (1)this dominant mode is given by the largest, discrete eigenvalue of a reduced problem that corresponds to Fourier mode k=0 in the azimuthal angle, and depends only on Stokes parameters U and V; (2)the polarization state of this dominant mode is largely circular polarized so that |V|≫|U|; and (3)the circular polarization of this dominant mode is maintained for all directions so that V is sign-definite. By applying these three tests to numerical calculations for monodisperse distributions of Mie scatterers, we determine the values of the size and relative refractive index when circular polarization memory occurs. In addition, we identify a reduced, scalar-like problem that provides an accurate approximation for the dominant mode when circular polarization memory occurs.

Influence of the size and skin thickness of apple varieties on the retrieval of internal optical properties using Vis/NIR spectroscopy: A Monte Carlo-based study

Visible/near-infrared spectroscopy is a well-established method to measure optical properties of tissues, assuming that a light propagation model can be used to recover absorption and reduced scattering coefficients from non-invasive probing. Spectroscopic measurements have achieved success in non-destructive assessment of apple optical properties and quality attributes. However, the spectroscopy of apples must consider the size of the fruit and the presence of the thin skin layer that surrounds the flesh, to correctly read the signals acquired on the boundary. In this research, the fruit was modelled as a two layer spherical structure with various radii and finite thickness of the upper skin layer. Monte Carlo computations were performed to generate time-resolved reflectance and spatially-resolved reflectance measurements. Simulated data were then fitted using a procedure based on Levenberg–Marquardt algorithm with specific semi-infinite models. The errors in the retrieved optical properties of the flesh (absorption coefficient μa, and reduced scattering coefficient μ′s) were studied as functions of apple radius, skin thickness, and source–detector distance, for given optical parameter sets assigned to the flesh and the skin. The results suggest that the time-resolved reflectance spectroscopy may probe optical properties of the flesh regardless of the skin layer, when a sufficient source–detector distance (15mm) is used for the measurements. Similar results were found in case of using the spatially resolved spectroscopy, because measurements extend up to 15–29mm by steps of 1mm or 2mm. The computations also show that the curvature of the boundary has noticeable effect on the errors in the retrieved optical coefficients of the flesh. However, results from time-resolved spectroscopy are more influenced by the size of apples, compared with the spatially-resolved spectroscopy.

Red and NIR light dosimetry in the human deep brain

Photobiomodulation (PBM) appears promising to treat the hallmarks of Parkinson’s Disease (PD) in cellular or animal models. We measured light propagation in different areas of PD-relevant deep brain tissue during transcranial, transsphenoidal illumination (at 671 and 808 nm) of a cadaver head and modeled optical parameters of human brain tissue using Monte-Carlo simulations. Gray matter, white matter, cerebrospinal fluid, ventricles, thalamus, pons, cerebellum and skull bone were processed into a mesh of the skull (158 × 201 × 211 voxels; voxel side length: 1 mm). Optical parameters were optimized from simulated and measured fluence rate distributions. The estimated μeff for the different tissues was in all cases larger at 671 than at 808 nm, making latter a better choice for light delivery in the deep brain. Absolute values were comparable to those found in the literature or slightly smaller. The effective attenuation in the ventricles was considerably larger than literature values. Optimization yields a new set of optical parameters better reproducing the experimental data. A combination of PBM via the sphenoid sinus and oral cavity could be beneficial. A 20-fold higher efficiency of light delivery to the deep brain was achieved with ventricular instead of transcranial illumination. Our study demonstrates that it is possible to illuminate deep brain tissues transcranially, transsphenoidally and via different application routes. This opens therapeutic options for sufferers of PD or other cerebral diseases necessitating light therapy.

TH‐A‐18C‐01: Design Optimization of Segmented Scintillators for Megavoltage Cone‐ Beam CT

Purpose:Active matrix flat‐panel imagers incorporating thick, segmented scintillators for megavoltage cone‐beam CT (MV CBCT) imaging have demonstrated strong potential for facilitating soft‐tissue visualization at low, clinically practical doses. In order to identify scintillator design parameters that optimize performance for this purpose, a modeling technique which includes both radiation and optical effects and which lends itself to computationally practical implementation has been developed and explored.Methods:A hybrid modeling technique, based on Monte Carlo event‐by‐event simulation of radiation transport and separate determination of optical effects, was devised as an alternative to computationally prohibitive event‐by‐ event simulations of both radiation and optical transport. The technique was validated against empirical results from a previously reported 1.13 cm thick, 1.016 mm element‐to‐element pitch BGO scintillator prototype. Using this technique, the contrast‐to‐noise ratio (CNR) and spatial resolution performance of numerous scintillator designs, with thicknesses ranging from 0.5 to 6 cm and pitches ranging from 0.508 to 1.524 mm, were examined.Results:CNR and spatial resolution performance for the various scintillator designs demonstrate complex behavior as scintillator thickness and pitch are varied – exhibiting a clear trade‐off between these two imaging metrics up to a thickness of ˜3 cm. Based on these results, an optimization map highlighting those regions of design that provide a balance between these metrics was created. The map indicates that, for a given set of optical parameters, scintillator thickness and pitch can be judiciously chosen to maximize performance without resorting to thicker, more costly scintillators.Conclusion:Modeling radiation and optical effects in thick, segmented scintillators through use of a hybrid modeling technique provides a practical way to gain insight as to how to optimize the performance of such devices for radiotherapy imaging. Assisted by such modeling, the development of practical designs should greatly facilitate low‐dose, soft tissue visualization through MV CBCT imaging.This project was supported in part by NIH grant R01 CA051397.

Optimization of the design of thick, segmented scintillators for megavoltage cone-beam CT using a novel, hybrid modeling technique.

Active matrix flat-panel imagers (AMFPIs) incorporating thick, segmented scintillators have demonstrated order-of-magnitude improvements in detective quantum efficiency (DQE) at radiotherapy energies compared to systems based on conventional phosphor screens. Such improved DQE values facilitate megavoltage cone-beam CT (MV CBCT) imaging at clinically practical doses. However, the MV CBCT performance of such AMFPIs is highly dependent on the design parameters of the scintillators. In this paper, optimization of the design of segmented scintillators was explored using a hybrid modeling technique which encompasses both radiation and optical effects. Imaging performance in terms of the contrast-to-noise ratio (CNR) and spatial resolution of various hypothetical scintillator designs was examined through a hybrid technique involving Monte Carlo simulation of radiation transport in combination with simulation of optical gain distributions and optical point spread functions. The optical simulations employed optical parameters extracted from a best fit to measurement results reported in a previous investigation of a 1.13 cm thick, 1016 μm pitch prototype BGO segmented scintillator. All hypothetical designs employed BGO material with a thickness and element-to-element pitch ranging from 0.5 to 6 cm and from 0.508 to 1.524 mm, respectively. In the CNR study, for each design, full tomographic scans of a contrast phantom incorporating various soft-tissue inserts were simulated at a total dose of 4 cGy. Theoretical values for contrast, noise, and CNR were found to be in close agreement with empirical results from the BGO prototype, strongly supporting the validity of the modeling technique. CNR and spatial resolution for the various scintillator designs demonstrate complex behavior as scintillator thickness and element pitch are varied--with a clear trade-off between these two imaging metrics up to a thickness of ~3 cm. Based on these results, an optimization map indicating the regions of design that provide a balance between these metrics was obtained. The map shows that, for a given set of optical parameters, scintillator thickness and pixel pitch can be judiciously chosen to maximize performance without resorting to thicker, more costly scintillators. Modeling radiation and optical effects in thick, segmented scintillators through use of a hybrid technique can provide a practical way to gain insight as to how to optimize the performance of such devices in radiotherapy imaging. Assisted by such modeling, the development of practical designs should greatly facilitate low-dose, soft tissue visualization employing MV CBCT imaging in external beam radiotherapy.

Modelling the propagation of radiation in inhomogeneous media using computations on graphical processors

This paper discusses a number of questions that arise when the propagation of optical radiation in biological tissues is calculated. Results of the modelling are obtained for media with various sets of optical parameters, including a six-layer model of human skin. An approach is presented for increasing the computational efficiency of the method that is used.

An Aquaculture Water Checker--design and Manufacture

A real-time, mobile aquaculture water checker is presented. The configuration of double integrating spheres is developed for simultaneously measuring backward scattering $R_d$, forward scattering $T_d$ and transmitted light $T_c $. Based on Kubelka-Munk model, a set of optical parameters including absorption coefficient $\mu _a $, scattering coefficient $\mu_s$ and anisotropy $g$ are calculated. The obtained results for diluted milk standard samples with different milk concentrations and aquaculture water samples with different densities of Psexdo-Nitzschia-delicatissium algae are also reported.