17 research outputs found
Создание износостойкого покрытия с использованием непрерывного и импульсного электронного луча
В настоящей работе представлены результаты исследования влияния импульсной электронной обработки и последующего отжига на структуру и твердость покрытий из хромо-ванадиевого чугуна. Покрытия были получены методом электронно-лучевой наплавки на подложке из малоуглеродистой стали. После шлифования поверхности покрытий были обработаны локальноимпульсным сфокусированным в точку электронным пучком. Результаты исследования показали, что модифицированные зоны состоят из двух фаз. Первая фаза - пересыщенный аустенит. Вторая локально распределенные в объеме модифицированной зоны зародыши эвтектики. Результаты измерений системой NanoTest показали, что модифицированные зоны имеют низкие значения твердости. Низкие значения твердости, вероятно, обусловлено наличием значительного объема пересыщенного аустенита в модифицированной зоне. Отжиг приводит к значительному увеличению твердости модифицированных зон. В результате отжига (500°С ) пересыщенный аустенит распадается. Повышение температуры отжига до 1100°С приводит к росту и коагуляции карбидной фазы модифицированных зон
Recent Advances in Metasurface Design and Quantum Optics Applications with Machine Learning, Physics-Informed Neural Networks, and Topology Optimization Methods
As a two-dimensional planar material with low depth profile, a metasurface
can generate non-classical phase distributions for the transmitted and
reflected electromagnetic waves at its interface. Thus, it offers more
flexibility to control the wave front. A traditional metasurface design process
mainly adopts the forward prediction algorithm, such as Finite Difference Time
Domain, combined with manual parameter optimization. However, such methods are
time-consuming, and it is difficult to keep the practical meta-atom spectrum
being consistent with the ideal one. In addition, since the periodic boundary
condition is used in the meta-atom design process, while the aperiodic
condition is used in the array simulation, the coupling between neighboring
meta-atoms leads to inevitable inaccuracy. In this review, representative
intelligent methods for metasurface design are introduced and discussed,
including machine learning, physics-information neural network, and topology
optimization method. We elaborate on the principle of each approach, analyze
their advantages and limitations, and discuss their potential applications. We
also summarise recent advances in enabled metasurfaces for quantum optics
applications. In short, this paper highlights a promising direction for
intelligent metasurface designs and applications for future quantum optics
research and serves as an up-to-date reference for researchers in the
metasurface and metamaterial fields
On-chip interrogator based on Fourier Transform spectroscopy
In this paper, the design and the characterization of a novel interrogator
based on integrated Fourier transform (FT) spectroscopy is presented. To the
best of our knowledge, this is the first integrated FT spectrometer used for
the interrogation of photonic sensors. It consists of a planar spatial
heterodyne spectrometer, which is implemented using an array of Mach-Zehnder
interferometers (MZIs) with different optical path differences. Each MZI
employs a 33 multi-mode interferometer, allowing the retrieval of the
complex Fourier coefficients. We derive a system of non-linear equations whose
solution, which is obtained numerically from Newton's method, gives the
modulation of the sensor's resonances as a function of time. By taking one of
the sensors as a reference, to which no external excitation is applied and its
temperature is kept constant, about 92 of the thermal induced phase drift
of the integrated MZIs has been compensated. The minimum modulation amplitude
that is obtained experimentally is 400 fm, which is more than two orders of
magnitude smaller than the FT spectrometer resolution.Comment: 15 pages, 6 figure
Quantitative coating thickness determination using a coefficient-independent hyperspectral scattering model
Background: Hyperspectral imaging is a technique that enables the mapping of spectral signatures across a surface. It is most commonly used for surface chemical mapping in fields as diverse as satellite remote sensing, biomedical imaging and heritage science. Existing models, such as the Kubelka-Munk theory and the Lambert-Beer law also relate layer thickness with absorption, and in the case of the Kubelka-Munk theory scattering, however they are not able to fully describe the complex behavior of the light-layer interaction.
Methods: This paper describes a new approach for hyperspectral imaging, the mapping of coating surface thickness using a coefficient-independent scattering model. The approach taken in this paper is to model the absorption and scattering behavior using a developed coefficient-independent model, calibrated using reference sample thickness measurements performed with optical coherence tomography.
Results: The results show that this new model, by considering the spectral variation that can be recorded by the hyperspectral imaging camera, is able to measure coatings of 250 μm thickness with an accuracy of 11 μm in a fast and repeatable way.
Conclusions: The new coefficient-independent scattering model presented can successfully measure the thickness of coatings from hyperspectral imaging data
Plasmonic enhancement of photoacoustic-induced reflection changes
In this paper, we report on surface-plasmon-resonance enhancement of the time-dependent reflection changes caused by laser-induced acoustic waves. We measure an enhancement of the reflection changes induced by several acoustical modes, such as longitudinal, quasi-normal, and surface acoustic waves, by a factor of 10–20. We show that the reflection changes induced by the longitudinal and quasi-normal modes are enhanced in the wings of the surface plasmon polariton resonance. The surface acoustic wave-induced reflection changes are enhanced on the peak of this resonance. We attribute the enhanced reflection changes to the longitudinal wave and the quasi-normal mode to a shift in the surface plasmon polariton resonance via acoustically induced electron density changes and via grating geometry changes
Wavefront shaping through a free-form scattering object
Wavefront shaping is a technique to study and control light transport inside scattering media. Wavefront shaping is considered to be applicable to any complex material, yet in most previous studies, the only sample geometries that are studied are slabs or wave-guides. In this paper, we study how macroscopic changes in the sample shape affect light scattering using the wavefront shaping technique. Using a flexible scattering material, we optimize the intensity of light in a focusing spot using wavefront shaping and record the optimized pattern, comparing the enhancement for different curvatures and beam radii. We validate our hypothesis that wavefront shaping has a similar enhancement regardless of the free-form shape of the sample and thus offers relevant potential for industrial applications. We propose a new figure of merit to evaluate the performance of wavefront shaping for different shapes. Surprisingly, based on this figure of merit, we observe that for this particular sample, wavefront shaping has a slightly better performance for a free-form shape than for a slab shape
Quantitative coating thickness determination
The coating selected in this research was a film-forming low-gloss wood lacquer for outdoors (Transparant zijdeglanslak voor buiten, Wijzonol Bouwverven B.V.). This coating was selected because it is semi-transparent commonly used wood coating, making it a suitable coating to visualize with OCT and hyperspectral imaging. This spruce-colored coating is based on organic solvent with an alkyd binder and applied using a brush. The samples that were prepared are:
1) Coating in a very flat and reflective silicon wafer to be able to determine the refractive index of the coating.
2) Different thickness coatings applied to a thin cover glasses in order to be able to determine the K and S coefficients from the KM-model and the extinction coefficient from the LB model. In order to measure the coefficients, these cover glasses were placed on a black-and-white checkerboard, as described below.
3) One to four layers of the coating were applied to a Medium-Density Fibreboard (MDF) plate covered with acrylic gesso. This reflective non-absorbing background serves as a reference for assessing the performance of the models. The hysperspectral imaging setup used in this study consisted of an IMSPECTOR V10E (Specim©) spectral camera, operating in the 400-1000 nm range. The visible range was selected due to the main absorption characteristics of the studied coating layers which is within the range of 400-1000nm.Optical Coherence Tomography (OCT) is a suitable technique for imaging the interfaces in a semi-transparent material and is therefore a logical choice for measuring coating thickness. This technique is based on low-coherence interferometry to measure light reflections from refractive index interfaces. As shown in Fig. 5, a customized OCT system was built by using a superluminescent diode (FESL-1550-20-BTF, Frankfurt Laser Company) centered at 1550 nm with a full width at half maximum of 60 nm, resulting in a 20 µm spot size and an 11 µm theoretical axial resolution inside the coating layer (considering a refractive index of 1.5). Depth-scanning for OCT was realized by the means of an optical delay line (ODL-650,MC, OZ Optics, Ltd). Lateral scanning of a sample with an x-y translation stage (T-LS28M, Zaber Inc., Canada) allowed for a 28 mm scanning range in two directions. Obtained data were bandpass filtered and an envelope detector was used to recover the depth dependent signal
The Influence of Particle Size Distribution and Shell Imperfections on the Plasmon Resonance of Au and Ag Nanoshells
Au and Ag nanoshells are of interest for a wide range of applications. The plasmon resonance of such nanoshells is the property of interest and can be tuned in a broad spectral regime, ranging from the ultraviolet to the mid-infrared. To date, a large number of manuscripts have been published on the optics of such nanoshells. Few of these, however, address the effect of particle size distribution and metal shell imperfections on the plasmon resonance. Both are inherent to the chemical synthesis of metal nanoshells and therefore to a large extent unavoidable. It is of vital importance to understand their effect on the plasmon resonance, since this determines the scope and limitations of the technology and may have a direct impact on the application of such particles. Here, we elucidate the effect of particle size distribution and imperfections in the metal shell on the plasmon resonance of Au and Ag nanoshells. The size of the polystyrene core and the thickness of the Au and Ag shells are systematically varied to study their influence on the plasmon resonance, and the results are compared to values obtained through optical simulations using extended Mie theory and finite element method. Discrepancies between theory and practice are studied in detail and discussed extensively. Quantitative information on the minimum thickness of the metal shell, which is required to realize a satisfactory plasmon resonance of a metal nanoshell, is provided for Au and Ag
The Influence of Particle Size Distribution and Shell Imperfections on the Plasmon Resonance of Au and Ag Nanoshells
Au and Ag nanoshells are of interest for a wide range of applications. The plasmon resonance of such nanoshells is the property of interest and can be tuned in a broad spectral regime, ranging from the ultraviolet to the mid-infrared. To date, a large number of manuscripts have been published on the optics of such nanoshells. Few of these, however, address the effect of particle size distribution and metal shell imperfections on the plasmon resonance. Both are inherent to the chemical synthesis of metal nanoshells and therefore to a large extent unavoidable. It is of vital importance to understand their effect on the plasmon resonance, since this determines the scope and limitations of the technology and may have a direct impact on the application of such particles. Here, we elucidate the effect of particle size distribution and imperfections in the metal shell on the plasmon resonance of Au and Ag nanoshells. The size of the polystyrene core and the thickness of the Au and Ag shells are systematically varied to study their influence on the plasmon resonance, and the results are compared to values obtained through optical simulations using extended Mie theory and finite element method. Discrepancies between theory and practice are studied in detail and discussed extensively. Quantitative information on the minimum thickness of the metal shell, which is required to realize a satisfactory plasmon resonance of a metal nanoshell, is provided for Au and Ag