Absorption Of Optical Radiation Research Articles

Photodynamic treatment of malignant melanoma with structured light: in silico Monte Carlo modeling.

In this report, we propose a novel strategy for the photodynamic approach to the treatment of melanoma, aiming to mitigate the excessive absorption and consequent thermal effects. The cornerstone of this approach is an innovative structured illumination technique that optimizes light delivery to the tissue. The methodology of this in silico study involves the development of an optical model of human skin with the presence of melanoma and an accurate simulation technique of photon transport within the complex turbid scattering medium. To assess the effectiveness of our proposed strategy, we introduced a cost function reflecting the irradiated volume and optical radiation absorption within the target area/volume occupied by malformation. By utilizing the cost function, we refine the offset illumination parameters for a variety of target system parameters, ensuring increased efficiency of photodynamic therapy. Our computer simulation results introduce a promising new path towards improved photodynamic melanoma treatments, potentially leading to better therapeutic outcomes and reduced side effects. Further experimental validation is needed to confirm these theoretical advancements, which could contribute towards revolutionizing current melanoma photodynamic treatment methodologies.

Remote sensing inversion study of total organic carbon concentration in Karst Plateau Lakes–Taking Pingzhai reservoir as an example

Currently, the inversion of remote sensing satellite images of water environment indicators mostly stays in the indicators with active optical characteristics, while there is less research on the inversion of most water quality indicators with non-optical activity properties, weak scattering and absorption of optical radiation, the size of their concentration has little effect on the spectral characteristics of the water body, such as TOC(Total Organic Carbon). In this paper, based on Pingzhai Reservoir, a dammed river in the karst mountainous area, the inversion model of TOC concentration was established based on BP neural network (BPNN) and sentinel-2 satellite remote sensing images. The results showed that the single bands with high correlation with the measured TOC concentration data were two vegetation red-edge bands B6 (740 nm) and B7 (783 nm) and one NIR band B8 (842 nm), and finally b7, b6 + b7, b7 + b8, b7 × b8 were selected as the input layers of BPNN for modeling through the combination of the bands, and their Pearson’s coefficients were −0.667, −0.656, −0.655, − 0.675.The inverse model established could reach a minimum RMSE of 0.235 mg/L and a maximum R 2 of 0.889, which was superior to that of the conventional empirical model. Demonstrate the feasibility of a TOC inversion method based on Sentinel-2 data and BPNN to monitor TOC concentrations in Pingzhai Reservoir. The study successfully established a BP neural network inversion model of TOC concentration in Pingzhai Reservoir with low error, meanwhile, we analyzed the correlation between common water quality indicators and TOC in the reservoir, in which TOC showed significant positive correlation with WT and significant negative correlation with TN and EC, with Pearson’s coefficients of 0.655, −0.666, and −0.393, respectively. The article provides scientific theoretical foundation and technical support for water quality protection of water sources.

Remote Determination of Wool Color

Analysis of the financial condition of the sheep industry is partly due to the low color purity of sheared wool, in the absence of animal selection to form sheep flocks with the same stripe color and the creation of conditions that would make it impossible to mix animals in flocks with different colors. To enable the above objectives to be achieved, theoretical studies of the conditions of reflection and absorption of optical radiation by the wool coat of animals were carried out, for which purpose the model of the incident ray interacting with the surface of sheep wool was improved and studied. The role of the reflected flux in diffuse scattering on individual wool layers is determined and a model of the reflected flux in the presence of local internal inhomogeneities is developed. The obtained functional dependences characterizing both the reflected and scattered light made it possible to formulate the requirements regarding technical implementation of the proposed method of flock formation by wool color.

Photo-sensitive Structures with Cascade Radiation Concentrators Based on Colloidal Quantum Dots of Metal Chalcogenides

Introduction . The problem of increasing the efficiency of existing photodetectors and creating their new types attracts much research attention. Among new photodetector types are photosensitive structures based on cascade concentrators, whose operational principle involves the absorption of optical radiation followed by its reemission at a longer wavelength and radiation concentration onto a highly efficient small-area photodetector. The absorption and re-emission spectra of each cascade layer depend on the characteristics of the material used. Сolloidal quantum dots are among the most promising materials for cascade layers due to their manufacturing technology, which provides for accurate control over the photoluminescence maximum position. It seems highly relevant to develop and to study photosensitive structures with cascade concentrators of various shapes based on CdS, CdSe/ZnS, and PbS colloidal quantum dots. Aim . To develop photosensitive structures with a wide-range sensitivity spectrum based on concentrators containing arrays of metal chalcogenide CQDs and to study their characteristics. Materials and methods . Cascade photosensitive structures were manufactured based on layers made of polymethyl methacrylate and layers of colloidal quantum dots embedded in a polystyrene matrix. Results . Three-layer concentrators were manufactured with different colloidal quantum dots in each concentrator layers. A 22 % increase in the output power was observed for a three-layer cascade structure based on different cascade layer materials compared to a similar structure using a single layer concentrator. Conclusion . The conducted studies showed an increase in the efficiency of photosensitive structures with a cascade concentrator based on colloidal quantum dots of various types (CdS, CdSe/ZnS, and PbS) in the cascade layers.

Growth of TiO2–CdO coated films: A brief study for optoelectronic applications

Current work reports the deposition of pure and TiO2 doped CdO printed films on glass substrate via cost-effective screen-printing method and then sintered at 550 °C for 10 min. The pure TiO2, CdO and TiO2–CdO coated films were used to investigate the structural, morphological and opto-electrical properties by different analytical techniques. X-ray diffraction pattern of polycrystalline doped analogue confirms the existence of TiO2 anatase phase and cubic phase of CdO with a maximum diffraction of (101) plane. Surface morphology is derived from scanning electron microscopy finding out porous images along with EDS results to confirm the desired composition. The spectra of UV–Vis diffused reflectance spectroscopy and photoluminescence absorbance peaks show a red shift due to change in reflectance. IR transmittance spectra recorded in 4000-400 cm−1 region exhibits the stretching modes of O–Ti–O and Cd–O groups present in these samples. The current vs. voltage (IV) characteristics and direct current conductivity measurement shows p-n junction diode behaviour. All the parameters were calculated and described in-depth, including structural, optical and electrical properties. The obtained results suggest that TiO2–CdO thick film could be used in optoelectronic applications due to the shift in optical radiation absorption to visible region, reduction in recombination rate of charge carriers and increase in electrical conductivity.

Optical absorption in a waveguide based on an n-type AlGaAs heterostructure

Free carrier absorption of optical radiation in layers of an AlGaAs/GaAs heterostructure is studied by the method of probe radiation coupling in order to determine the absorption cross section parameter in the AlGaAs material with a high (22%) aluminium concentration. For this purpose, we have fabricated special samples based on AlGaAs/GaAs heterostructures simulating an n-type-doped laser waveguide with carrier concentrations in the range 5 × 1016 − 3 × 1017 cm−3. The doping profile and the composition and thickness of layers are measured and the temperature and spectral dependences of the absorption coefficient are studied. It is shown that an increase in temperature and in the probe wavelength leads to an increase in the absorption in the heterostructure layers.

Application of optical narrow-band mirrors in sensor of concentration of dust in coal mines

The article presents a new design of the sensor for measuring dust, which is based on the effect of absorption of optical radiation passing through the dust layer. Fundamentally new is the use of a powerful low-cost LED, the spectral part of the radiation range required for measurement of which is formed by the structure of auxiliary reflective optical interference filters. A technique based on the introduced stability criterion of the synthesized interference coating is developed, which makes it possible to study the transformation of the spectra with real errors in the film thicknesses.

Experimental technique for studying optical absorption in waveguide layers of semiconductor laser heterostructures

We report a technique for studying the absorption of optical radiation in layers of a semiconductor heterostructure by the method of probe radiation coupling. The studies are carried out using specially made isotype samples based on AlGaAs/GaAs, simulating an n-type doped laser waveguide with a concentration of 1017 – 1018cm−3. The main features of the experimental setup and calculation methods are described. A high (up to 95%) efficiency of light coupling into the waveguide and an error in measuring the absorption coefficient at a level of 0.1 cm−1 are achieved. The possibilities of studying the polarisation and temperature dependences of radiation absorption by free carriers are experimentally demonstrated. It is shown that with an increase in temperature in the range 25 – 85°C, the absorption in the samples increases by 15%.

Peculiarities of light absorption by spherical microcapsules

We address the peculiarities of optical radiation absorption in a poly-layer spherical microparticle which simulates an inorganic/organic poly-shell absorbing microcapsule with a water-based cargo. By means of the finite-difference time-domain technique, the spatial distribution of absorbed light power in microcapsules of various sizes and internal structure is numerically simulated. We have engineered the optimal structure of a capsule that provides for light absorption enhancement and consists of a strong refracting transparent coating and an absorbing layer which covers a liquid core. The proposed multi-layer microcapsule prototype provides for a manifold increase in the absorbed light power density in comparison with usual single-layer absorbing capsule. We show that for wavelength-scale microcapsules it is optimal to use a material with the refractive index larger than 2 as an outer shell, for example, titanium dioxide. The highest values of the absorbed power density can be obtained in microcapsules with absorbing shell thickness of approximately λ/10. When laser radiation is scattered by a dimer constituted by two identical absorbing microcapsules the absorbed power density can be maximized by choosing proper dimer spatial configuration. In the case of strongly absorbing particles, the absorption density is maximal if the distance between capsules is about one capsule diameter. For weakly absorbing particles, light absorption increases when particles in the capsule are in geometrical shades of each other.

Secondary Electron Cloaking with Broadband Plasmonic Resonant Absorbers

Scanning electron microscopy (SEM) is one of the most powerful tools for nanoscale inspection and imaging. It is broadly used for biomedicine, materials science, and nanotechnology, enabling spatial resolution beyond the optical diffraction limit. In SEM, a high-energy electron beam illuminates a specimen, and the emitted secondary electrons are routed to a positively biased, synchronized detector for image creation. Here, for the first time, we experimentally demonstrate a cloaking of metallic objects from a secondary electron image. We make a metallic disc with a diameter of 300 nm almost invisible to a secondary electron detector with <5 nm spatial resolution. The secondary electron cloaking is based on broadband optical radiation absorption in the near field. Our secondary electron images are in good agreement with full-wave numerical solution of Maxwell's equations at optical frequencies, confirming the concept of secondary electron cloaking based on broadband optical radiation absorption.

Optimization of optical radiation absorption by multilayer spherical microparticles

The spatial distribution and amplitude characteristics of the power absorbed inside multilayer particle-microcapsules, which consist of a liquid core and one or more polymer shells, is studied during changing the thickness and refractive index of the external shell; the position of the field localization is determined. This problem is important for the solution of practical tasks associated with opening the microcapsule shells in the appropriate spatial areas.

Study of Photosensitive Dry Films Absorption for Printed Circuit Boards by Photoacoustic Technique

In this work, the study of photosensitive dry-type films by photoacoustic technique is proposed. The dry film photoresist is resistant to chemical etching for printed circuit boards such as ferric chloride, sodium persulfate or ammonium, hydrochloric acid. It is capable of faithfully reproducing circuit pattern exposed to ultraviolet light (UV) through a negative. Once recorded, the uncured portion is removed with alkaline solution. It is possible to obtain good results in surface mount circuits with tracks of 5 mm. Furthermore, the solid resin films are formed by three layers, two protective layers and a UV-sensitive optical absorption layer in the range of 325 nm to 405 nm. By means of optical absorption of UV–visible rays emitted by a low-power Xe lamp, the films transform this energy into thermal waves generated by the absorption of optical radiation and subsequently no-radiative de-excitation occurs. The photoacoustic spectroscopy is a useful technique to measure the transmittance and absorption directly. In this study, the optical absorption spectra of the three layers of photosensitive dry-type films were obtained as a function of the wavelength, in order to have a knowledge of the absorber layer and the protective layers. These analyses will give us the physical properties of the photosensitive film, which are very important in curing the dry film for applications in printed circuit boards.

Laser-Induced Periodic Surface Structures— A Scientific Evergreen

Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon and can be generated on almost any material upon irradiation with linearly polarized radiation. With the availability of ultrashort laser pulses, LIPSS have gained an increasing attraction during the past decade, since these structures can be generated in a simple single-step process, which allows a surface nanostructuring for tailoring optical, mechanical, and chemical surface properties. In this study, the current state in the field of LIPSS is reviewed. Their formation mechanisms are analyzed in ultrafast time-resolved scattering, diffraction, and polarization constrained double-pulse experiments. These experiments allow us to address the question whether the LIPSS are seeded via ultrafast energy deposition mechanisms acting during the absorption of optical radiation or via self-organization after the irradiation process. Relevant control parameters of LIPSS are identified, and technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.

Engineering polyshell spherical microcapsules for optimal localized light absorption.

Optical radiation absorption in a polylayer spherical microparticle simulating an inorganic/organic polyshell absorbing microcapsule is considered. With the aim of the finite-difference time-domain technique, the spatial distribution of the absorbed light power in microcapsules of various sizes and internal structure is numerically calculated. For the purpose of light absorption enhancement, we have engineered the optimal structure of a capsule consisting of a strong-refracting transparent outer coating and an absorbing layer which covers a liquid core. The proposed microcapsule prototype provides for a manifold increase in the absorbed light power density in comparison with the usual single-layer absorbing capsule. We show that for light-wavelengths-scaled microcapsules it is optimal to use a material with the refractive index larger than two as an outer shell, for example, titanium dioxide (TiO2). The highest values of the absorbed power density can be obtained in microcapsules with absorbing shell thickness of approximately a tenth of a laser wavelength.

Light absorption by an atomic force microscope probe

In this paper a probe of an atomic force microscope (AFM) served as a detector of optical radiation. We investigated absorption of optical radiation in the visible range by commercially available Si and Si3N4 probes. It has been shown that the radiation in the far field is mainly absorbed in the probe tip. By scanning a laser beam with a diameter of ∼ 0.7 microns by the AFM probe, a lateral resolution of ∼ 1.5 microns was demonstrated. Numerical modeling of evanescent wave absorption by AFM probes showed enhancement of the absorption in the probes as compared with a flat surface. A Si3N4 probe more effectively absorbs the evanescent radiation.

Optimization of optical radiation absorption by multilayer spherical microparticles

Optimization of optical radiation absorption by multilayer spherical microparticles

Photo-thermal electrical resistance response of polyisoprene/nanographite composites

Laser induced photo-thermal resistance response (PTRR) of polyisoprene/nanographite (PN) composites was studied. An inverse character of photoresistance in comparison to semiconductor-like materials was observed: electrical resistance of the PN composite increases when the intensity of the laser radiation is increased. The observed response can be explained by the photo-thermal effect: if the temperature of the PN composite rises because of optical radiation absorption then the electrical resistance increases due to positive temperature coefficient of the composite. Theoretical explanation of the positive temperature coefficient effect in PN composites based on tunneling-percolation model is given.

Research of Optical Radiation Absorption Process by Soft Periodontal Tissues

Research of Optical Radiation Absorption Process by Soft Periodontal Tissues

Hydrocarbon film formed on the surface of a semiconductor irradiated by an electron beam

The rate of formation of a hydrocarbon film on the surface of a sample subjected to the action of an electron beam is studied at room temperature and in cooling a sample to the liquid nitrogen temperature. The thickness and the optical radiation transmission of such films are measured as functions of the electron beam radiation time, the sample temperature, and the level of vacuum. The film thickness is measured with atomic force microscopy. The absorption of the films is determined by comparing the cathodoluminescence intensities from a pure sample surface and from the surface covered with a film. The experimental results can be used to estimate the film formation rate as a function of the sample temperature and the vacuum and to determine the optical radiation absorption at a wavelength of 300, 360, 550, and 665 nm.

Forming a silicon nanocomposite by laser annealing in a strong oxidant medium

This paper discusses the transmission spectra of a nanocomposite created by a new electron–ion technology—low-temperature laser surface modification of a layer of nanoporous silicon in a medium of a strong gaseous oxidant. A selective-absorption effect has been detected in the IR range. It is shown that the transmission spectrum of laser-oxidized nanoporous silicon has the form of a complex curve with four local minima, lying in the wavenumber ranges 4000–2750 cm−1, 2400–2100 cm−1, 1900–1600 cm−1, and 1300–1000 cm−1. A comparison of the transmission spectra of thermally oxidized nanoporous silicon and laser-modified nanoporous silicon in a strong oxidant atmosphere made it possible to explain the selective absorption of optical radiation in the nanocomposite thus created.