- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Measuring the Lower Critical Field of Superconductors Using Nitrogen-Vacancy Centers in Diamond Optical Magnetometry
摘要： The lower critical magnetic field, Hc1, of superconductors is measured by optical magnetometry using ensembles of nitrogen-vacancy centers in diamond. The technique is minimally invasive and allows accurate detection of the vector magnetic field with subgauss sensitivity and submicrometer spatial resolution. These capabilities are used for detailed characterization of the first vortex penetration into superconducting samples from the corners. Aided by the revised calculations of the effective demagnetization factors of actual cuboid-shaped samples, these measurements provide precise determination of Hc1 and the related absolute value of the London penetration depth, λ. We apply this method to three well-studied superconductors: optimally doped Ba(Fe1?xCox)2As2, stoichiometric CaKFe4As4, and the high-Tc cuprate YBa2Cu3O7?δ. Our results compared well with the values of λ obtained with other techniques, thus adding another noninvasive and sensitive method to measure these important parameters of superconductors.
关键词： optical magnetometry,nitrogen-vacancy centers,London penetration depth,superconductors,lower critical field
更新于2025-09-23 15:22:29
-
The relation between magnesium evaporation and laser absorption and weld penetration in pulsed laser welding of aluminum alloys: Experimental and numerical investigations
摘要： It is observed that in laser welding of aluminum alloys, magnesium can evaporate, and the weld penetration is dependent on Mg content of the alloy and Mg loss from the weld pool. In this research, it is proposed that the presence of Mg not in the base metal alloy, but rather the presence of Mg vapor in the plasma plume over the weld pool affects the laser absorption, and it is through this phenomenon that the weld profile and penetration is affected. Numerical simulation was performed to determine the relationship between the weld profile to estimate the effective laser absorption coefficient of four Al alloys and in parallel EPMA technique was used to determine the Mg losses of the weld metals. The combined analysis of the results showed that increasing the laser pulse energy (decreasing laser pulse frequency), Mg evaporation is increased, and that, in turn, increased the effective laser absorption coefficient. However, more laser power absorption does not necessarily mean more weld penetration. Laser absorption results in weld penetration, once the threshold Mg evaporation rate of 200 × ?10 6g/cm2 is passed.
关键词： Pulsed laser welding,Effective absorption coefficient,Aluminum alloys,Evaporation,Magnesium content,Penetration depth
更新于2025-09-23 15:21:01
-
3D cellular imaging in thick biological tissue with confocal detection of one-photon fluorescence in the NIR-II window
摘要： Fluorescence imaging in the second near-infrared optical window (NIR-II, 900-1700 nm) has become a technique of choice for non-invasive in vivo imaging in recent years. Greater penetration depths with high spatial resolution and low background can be achieved with this NIR-II window, owing to low autofluorescence within this optical range and reduced scattering of long wavelength photons. Here, we present a novel design of confocal laser scanning microscope tailored for imaging in the NIR-II window. We showcase the outstanding penetration depth of our confocal setup with a series of imaging experiments. HeLa cells labeled with PbS quantum dots (QDs) with a peak emission wavelength of 1276nm can be visualized through a 3.5-mm-thick layer of scattering medium, which is a 0.8% Lipofundin solution. A commercially available organic dye IR-1061 (emission peak at 1132nm), in its native form, is used for the first time, as a NIR-II fluorescence label in cellular imaging. Our confocal setup is capable of capturing optically sectioned images of IR-1061 labeled chondrocytes in fixed animal cartilage at a depth up to 800μm, with a superb spatial resolution of around 2 μm.
关键词： scattering,NIR-II,resolution,penetration depth,confocal
更新于2025-09-19 17:15:36
-
Method of Laser Thermal Image Spectroscopy for Surface Diagnostics
摘要： A new method of laser-thermal imaging spectroscopy is presented and the results of studying samples with different absorption coefficients are reported. The times required for heating the surface of these samples by laser radiation with a wavelength of 0.634 μm to a temperature exceeding the initial value by 0.3°C are calculated and compared with the experimental data. The depths of laser-radiation penetration into the surface layer of the material under the condition of external and internal reflection are calculated. The depth determines the transition region in which the energy of absorbed laser radiation transforms into the thermal energy of the substance. It is shown that the method allows the surface of materials to be studied and zones with different optical and physical-chemical properties to be studied. The method can be used to solve problems in the field of medicine, surface restoration, forensic examination and others.
关键词： defect substance,surface defects,surface heating time,spectral absorption coefficient,penetration depth of laser radiation
更新于2025-09-19 17:13:59
-
[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Experimental and numerical study on laser welding of glass using a CO2 laser and glass fiber as filler material
摘要： Automated laser welding with filler wires for bridging gaps and for connecting complex devices has been established for different metal materials. In spite of that, it is still a challenge to transfer this welding process to the brittle material glass. Therefore, glass welding is often realized through a manual process by heating the glass with a gas flame. In addition, welding of non-rotational components requires filler material for gap bridging between the joining partners, which is applied manually today. This work presents an experimental and numerical study on laser welding of fused silica using glass fiber as a filler material to bridge gaps. The goal was to achieve a defined weld penetration depth and heat affected zone which is important for the production of optical elements. Therefore, a CO2 laser heats up the glass components as well as the glass fiber within a temperature controlled welding process. The numerical investigations were used to identify the general process window for welding fused silica. Within the experimental study, the process parameters, such as the defined welding temperature, laser focal spot size, and feed rate were varied to investigate their impact on the welding outcome. In addition, the impact of the filler wire coating on the material composition of the welded component in the joint zone was investigated. Compared to the manual process, laser welding with glass fiber as a filling material leads to a highly reproducible process enabling a high automation level.
关键词： fused silica,temperature controlled welding,heat affected zone,laser welding,glass fiber,filler material,glass,CO2 laser,weld penetration depth
更新于2025-09-19 17:13:59
-
Parametric Analysis of High Power Disk Laser Welding of 5052-H32 Aluminium Alloy
摘要： High power disk laser conducting welding of 2 mm thick AA 5052-H32 was performed within a process window and optimized for improved weld quality (i.e. penetration depth). The macrostructure of the weldment was investigated for the weld penetration depth at varying processing parameters using stereo zoom optical microscopy. The significance of the single effects and interaction effects of the parameters on the weld penetration depth was determined using ANOVA. Maximum weld penetration depth (1.71 mm) was achieved at laser power of 2600 W, welding speed of 0.03 m/s and focal position of -3.75 mm. At 95% confidence, only the welding speed –focal position interaction was found to contribute significantly to the weld penetration depth. The effect of the welding speed was most noticeable at low focal position (F < -3.9), that is, when the workpiece is further away from the focus. A linear regression mathematical model predicting the penetration depth of AA 5052-H32 disk laser weldments to an accuracy of 86% was developed and validated.
关键词： AA 5052-H32 Aluminium Alloy,Optimisation,Regression Model,Disk Laser Welding,ANOVA,Penetration Depth
更新于2025-09-16 10:30:52
-
Penetration Profiles of Visible and Near-Infrared Lasers and Light-Emitting Diode Light Through the Head Tissues in Animal and Human Species: A Review of Literature
摘要： Background and objective: Photobiomodulation (PBM) therapy is a promising and noninvasive approach to stimulate neuronal function and improve brain repair. The optimization of PBM parameters is important to maximize effectiveness and tolerability. Several studies have reported on the penetration of visible-to-near-infrared (NIR) light through various animal and human tissues. Scientific findings on the penetration of PBM light vary, likely due to use of different irradiation parameters and to different characteristics of the subject such as species, age, and gender. Materials and methods: In this article, we review published data on PBM penetration through the tissues of the head in both animal and human species. The patterns of visible-to-NIR light penetration are summarized based on the following study specifications: wavelength, coherence, operation mode, beam type and size, irradiation site, species, age, and gender. Results: The average penetration of transcranial red/NIR (630–810 nm) light ranged 60–70% in C57BL/6 mouse (skull), 1–10% in BALB/c mouse (skull), 10–40% in Sprague–Dawley rats (scalp plus skull), 20% in Oryctolagus cuniculus rabbit (skull), 0.11% in pig (scalp plus skull), and 0.2–10% in humans (scalp plus skull). The observed variation in the reported values is due to the difference in factors (e.g., wavelengths, light coherence, tissue thickness, and anatomic irradiation site) used by researchers. It seems that these data challenge the applicability of the animal model data on transcranial PBM to humans. Nevertheless, two animal models seem particularly promising, as they approximate penetration in humans: (I) Penetration of 808 nm laser through the scalp plus skull was 0.11% in the pig head; (II) Penetration of 810 nm laser through intact skull was 1.75% in BALB/c mouse. Conclusions: In conclusion, it is worthwhile mentioning that since the effectiveness of brain PBM is closely dependent on the amount of light energy reaching the target neurons, further quantitative estimation of light penetration depth should be performed to validate the current findings.
关键词： optical properties,penetration depth,skull,low-level laser (light) therapy,brain tissues,transcranial photobiomodulation
更新于2025-09-12 10:27:22
-
An approach for correcting optical paths of different wavelength lasers in diffusive medium based on Monte Carlo simulation
摘要： Near-infrared spectroscopy (NIRS) generally uses multiple wavelengths of light to obtain functional information. When different wavelengths are employed together, their optical paths are different in the medium and it can potentially cause errors. In this study, we introduced an approach of correcting optical paths when laser sources are used. Laser can be approximated by a point source in a diffusive medium and its depth depends on the wavelength. By multiplying the ratio of detected weights emitted from different point sources, they are conceptually moved to the same position. Monte Carlo simulation was implemented to accumulate required data. As an example for verifying this method, optical properties of the white matter of the brain was used. All combinations of four wavelengths (400, 550, 700, and 850 nm) and six source-detector distances (0.5 mm to 3.0 mm at intervals of 0.5 mm) were simulated. Under the same example conditions, the difference between the simulation results and this method was about ‘1.28%’. The results showed that this approach is applicable to short source-detector distance conditions.
关键词： Monte Carlo simulation,Point source approximation,Near infrared spectroscopy,Light diffusion,Optical path,Penetration depth
更新于2025-09-12 10:27:22
-
[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Process control using capillary depth measurement
摘要： One important characteristics of laser beam welding is the penetration depth. Traditionally, it is determined by time-consuming and destructive cross-sectioning, but an online monitoring and eventually control system is desired. The measurement of the capillary depth in deep-penetration laser welding by optical coherence tomography (OCT), an interferometry measuring method, has been shown to be a sensing principle that allows an online in-situ measurement. It works in a wide range of industrial applications and delivers accurate data. In this paper we investigate the capability of the method and determine its restrictions.
关键词： optical coherence tomography,penetration depth,interferometry,capillary depth,laser beam welding
更新于2025-09-11 14:15:04
-
[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Investigation of Tandem-x Penetration Depth Over the Greenland Ice Sheet
摘要： Ongoing global warming causes dramatic changes globally, especially with respect to Polar Regions. In this context, digital elevation data is of high importance for most glaciological applications. In this paper, we investigate TanDEM-X penetration depth over snow and ice on the Greenland ice sheet. In particular, the relation of backscatter intensity and interferometric coherence to penetration depth of the X-band InSAR signal is explored in order to improve the reliability of TanDEM-X elevation data. The analyses showed a distinct relationship of backscatter intensity, coherence and penetration depth. In addition, the influence of the height of ambiguity of the interferometric TanDEM-X data is presented. On an experimental test site in Northern Greenland, we demonstrated the estimation of TanDEM-X penetration depth based on backscatter intensity and interferometric coherence utilizing a linear regression model.
关键词： TanDEM-X,Interferometric Synthetic Aperture Radar (InSAR),Greenland ice sheet,penetration depth
更新于2025-09-10 09:29:36