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Photoacoustic temperature imaging based on multi-wavelength excitation
摘要： Building further upon the high spatial resolution offered by ultrasonic imaging and the high optical contrast yielded by laser excitation of photoacoustic imaging, and exploiting the temperature dependence of photoacoustic signal amplitudes, this paper addresses the question whether the rich information given by multispectral optoacoustic tomography (MSOT) allows to obtain 3D temperature images. Numerical simulations and experimental results are reported on agarose phantoms containing gold nanoparticles and the effects of shadowing, reconstruction flaws, etc. on the accuracy are determined.
关键词： photoacoustic imaging,absorption coefficient,finite difference,multispectral optoacoustic tomography
更新于2025-11-14 15:30:11
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Theoretical model of absorption coefficient of an inhomogeneous MPP absorber with multi-cavity depths
摘要： Micro-perforated panel (MPP) absorber has been known as an alternative absorber to classical porous material given its facile installation, long durability, environmental friendliness and attractive appearance. Extensive studies of MPP absorber proposing the improvement of its absorption frequency bandwidth have been published. This study presents a MPP absorber introduced with inhomogeneous perforations and with multi-cavity depths. The MPP is divided into two sub-area, where each area has different hole diameter, perforation ratio and a separated backed cavity depth. The acoustic impedance is modelled using electrical equivalent circuit and the absorption coefficient is calculated under normal-incidence of sound. It is found that the inhomogeneous MPP can have good bandwidth of absorption by designing the sub-MPP of smaller perforation ratio with large hole diameter and the one having the larger perforation ratio with smaller hole diameter. The absorption bandwidth can be conveniently controlled by adjusting the cavity depth of each sub-MPP. The results from the experimental work show good agreement with the theoretical model.
关键词： Micro-perforated panel,Inhomogeneous MPP,Absorption coefficient,Acoustics
更新于2025-09-23 15:23:52
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Non-destructive inspection of food and technical oils by terahertz spectroscopy
摘要： Quality control and non-destructive monitoring are of notable interest of food and pharmaceutical industries. It relies on the ability of non-invasive inspection which can be employed for manufacturing process control. We hereby apply terahertz (THz) time-domain spectroscopy as non-destructive technique to monitor pure and degraded oils as well as hydrocarbon chemicals. Significant differences in the spectra of refractive index (RI) and absorption coefficient arising from the presence of ester linkages in the edible and technical oils were obtained. Explicit increase from 1.38 to 1.5 of the RI in all THz spectrum range was observed in hydrocarbons and mono-functional esters with the increase of molar mass. This fact is in contrast of RI dependence on molar mass in multi-functional esters, such as Adipate or vegetable oils, where it is around 1.54. Degradation products, Oleic Acid (OA) and water in particular, lead only to some changes in absorption coefficient and RI spectra of vegetable oils. We demonstrate that complex colloidal and supramolecular processes, such as dynamics of inverse micelles and oil hydrolysis, take part during oil degradation and are responsible for non-uniform dependence of optical properties on extent of degradation.
关键词： absorption coefficient,terahertz spectroscopy,oils,degradation,non-destructive inspection,refractive index
更新于2025-09-23 15:23:52
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Thin Films of Barium Strontium Titanate from the Viewpoint of Light-Based Applications
摘要： In this paper we report results from optical transmittance spectroscopy complemented with data on structure from XRD measurements to determine optical properties of a series of as-deposited and annealed (at 900 °C) BaSrTiO3 (BST) thin films deposited by RF magnetron sputtering. The members of the series differ by the substrate temperature and additional oxygen to accompany argon in the deposition chamber. The perovskite structure with weak preferred (110) orientation was detected for annealed BST thin films whilst the as-deposited films were amorphous. Dispersive optical properties – refractive indices, absorption coefficients and optical band gaps were determined from transmittance spectra. After annealing refractive indices increase to prove the densification of material accompanied by the thickness shrinkage. Optical band gaps calculated either by Tauc procedure or determined as iso-absorption levels are also found to be deposition dependent.
关键词： absorption coefficient,thin films,barium strontium titanate,refractive index,optical band gap
更新于2025-09-23 15:23:52
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Inspecting human colon adenocarcinoma cell lines by using terahertz time-domain reflection spectroscopy
摘要： Techniques to inspect and analyze human colorectal cancer cell lines by using terahertz time-domain attenuated total reflection spectroscopy (THz TD-ATR) were investigated. The characteristics of THz absorption spectra of two colorectal cancer cell lines DLD-1 and HT-29 in aqueous solutions with different concentrations were studied. Different spectral features were observed compared to normal cell line. Identification results based on different parameters including absorption coefficient, refractive index, real and imaginary parts of complex permittivity, dielectric loss tangent were discussed. This research may be promising for quick and instant inspection of liquid samples by using THz time-domain spectroscopy in medical applications.
关键词： Absorption coefficient,Dielectric loss tangent,Terahertz time-domain attenuated total reflection spectroscopy,DLD-1 cell line,Cancer identification,HT-29 cell line
更新于2025-09-23 15:23:52
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To the Theory of the Polarized Radiation Absorption in a Semiconductor (001) Quantum Well
摘要： The paper considers absorption of linearly polarized radiation in a semiconductor size-quantized well related to optical transitions both between the branches of light and heavy holes and between the size-quantized subbands. Main features of the light absorption in an infinitely deep symmetric well are elucidated. These features are characterized by intraband absorption of light and associated with the direct optical transitions of holes between the subbands of the semiconductor valence band formed due to the size quantization.
关键词： optical transition,semiconductor,size quantization,light absorption coefficient,polarized light,holes
更新于2025-09-23 15:23:52
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Defects anomaly in cobalt-doped ZnO nanostructures using optical and charge transient analysis
摘要： The significant effect of electrically active defects present in the device, which limits the carrier mobility, generated due to cobalt doping via the co-precipitation technique in a ZnO matrix, has been investigated on the basis of its structural, optical and charge transient behaviours. The variations observed in the absorbance and extinction coefficients as a function of wave length reveal the presence of defect states, a range of localized states and structural disorder. The presence of a non-uniform trap centre density in the material has been measured on the basis of different operational modes in charge-deep level transient spectroscopic analysis. A disparity of such a kind in the structures at the nanoscale will provide for a remarkable approach to improve the performance and reliability of the smart electronic, optoelectronics, photonics and sensing devices.
关键词： absorption coefficient,ZnO,Defect density,Q-DLTS,Nano structures,extinction coefficient
更新于2025-09-23 15:22:29
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Optical Characteristics of Zinc Oxide Films on Glass Substrates
摘要： An algorithm is developed for solving the inverse problem of multiangular spectrophotometry of a layer on a plane-parallel substrate of finite thickness using s- and p-polarized waves. It allows the dispersive properties of the layer and substrate to be studied both far from and in the vicinity of the resonant wavelengths. The dispersive properties of layers of pure and Al-doped ZnO on glass substrates are investigated using it. It is shown that doping shifts the absorption band maximum to shorter wavelength and decreases the refractive index of the material. The applicability limits of known approximate expressions for determining the spectral dependence of the absorption coefficient of a layer from spectrophotometric data are estimated.
关键词： band gap,refractive index and absorption coefficient,multiangular spectrophotometry,ZnO
更新于2025-09-23 15:22:29
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Binding energy and optical absorption of donor impurity states in “12-6” tuned GaAs/GaAlAs double quantum well under the external fields
摘要： We have investigated the binding energies of the s-symmetric ground and first excited shallow donor impurity states and the total 1s → 2s absorption coefficient, including the first and third order corrections, in "12-6" tuned GaAs/GaAlAs double quantum well as a function of the impurity position, size of the structure, and the electric and magnetic field intensities. The obtained results show that the electronic and optical properties of tuned GaAs/GaAlAs double quantum well can be adjustable by an appropriate choice of the sample geometry, material parameters and applied external fields which will lead to new potential applications in optoelectronics.
关键词： Double quantum well,Absorption coefficient,Electric and magnetic field,Donor impurity
更新于2025-09-23 15:21:21
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Influence of the energy dependence of the absorption coefficient on the solar energy conversion efficiency
摘要： In most cases, when the ef?ciencies of a single or multi-gap (with intermediate bands) solar cell are evaluated, the energy dependence of the absorption coef?cients is ignored. In this work we will evaluate the range of optical thickness and average absorption coef?cients in which this dependence should be considered. For this study we use different absorption coef?cients generated randomly as a function of the energy. In many practical cases, the ef?ciencies are lower than those expected.
关键词： optical thickness,energy dependence,intermediate-band solar cells,solar energy conversion efficiency,absorption coefficient
更新于2025-09-23 15:21:21