- 标题
- 摘要
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- 实验方案
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Characteristics of Ultrathin Ni Films
摘要： Conductive and transparent ultra-thin Nickel films are grown by RF sputtering on fused silica substrates. The characteristics of Ni films (thickness, refractive index, and extinction coefficient) are obtained by fitting multi-angle spectrophotometric and ellipsometric data. Films thickness inferred by X ray reflection (XRR) measurements is in good accordance with ellipsometric results. XPS analysis reveals that Ni metal phase is present in the film surface together with Ni mixed oxide phases, which explains the high electrical stability of such films.
关键词： optical measurements,ultrathin films,transparent conductive films,Ni films
更新于2025-09-23 15:23:52
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Online dimensional control of rolled steel profiles using projected fringes
摘要： Fringe projection is a versatile method for mapping the topography of surfaces. In this paper, it is used to measure the defects on the head of railroad rails while the rails are moving. Railroad rails are made by hot rolling. The quality of the finished product is generally good, but surface texture will deteriorate with increasing temperature. A method for online inspection therefore is very desirable. In the present experiment, dimensional inspection of the railroad rails was made online while moving at a speed of 1–2 m/s. Therefore, it is important to minimize the registration time. To achieve this, we apply a method of fringe location with sub-pixel accuracy that requires only a single exposure for each registration.
关键词： Fringe projection,Railroad rails,Optical measurements
更新于2025-09-23 15:21:01
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Directly photoexcited Dirac and Weyl fermions in ZrSiS and NbAs
摘要： We report ultrafast optical measurements of the Dirac line-node semimetal ZrSiS and the Weyl semimetal NbAs, using mid-infrared pump photons from 86 meV to 500 meV to directly excite Dirac and Weyl fermions within the linearly dispersing bands. In NbAs, the photoexcited Weyl fermions initially form a non-thermal distribution, signi?ed by a brief spike in the differential re?ectivity whose sign is controlled by the relative energy of the pump and probe photons. In ZrSiS, electron-electron scattering rapidly thermalizes the electrons, and the spike is not observed. Subsequently, hot carriers in both materials cool within a few picoseconds. This cooling, as seen in the two materials’ differential re?ectivity, differs in sign, shape, and timescale. Nonetheless, we ?nd that it may be described in a simple model of thermal electrons, without free parameters. The electronic cooling in ZrSiS is particularly fast, which may make the material useful for optoelectronic applications.
关键词： ultrafast optical measurements,electronic cooling,photoexcitation,Dirac line-node semimetal,thermalization,Weyl semimetal
更新于2025-09-23 15:21:01
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Upgrade the Evaluation of the Contribution of the Active Element Cross Section Geometry to the He-Ne Laser Energy Characteristics
摘要： The models for estimating the contribution of the cross section geometry to the active medium gain of the He-Ne laser have been considered in this work. Expanding the range of studied cross sections it has been found that these models were not analytical and demand the approximate calculations. Modern methods and computing tools should clarify the results of 1960–1970 and it will bring to more accurate results. Some the experimental verification was carried out only in a rectangular cross section. Our model have to complicate taking into account the field intensity distribution in the resonator.
关键词： active element cross section geometry,optical measurements,biomedicine,information optics,laser,the active medium gain,homogeneous and unhomogeneous boundary conditions
更新于2025-09-16 10:30:52
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Optical Fiber Communications (Principles and Applications) || Optical Measurements
摘要： Optical measurements are necessary to verify the operational characteristics of the optical fiber communication link. Various measurement techniques and special-purpose test equipments are employed for determining key performance parameters of the constituent components and devices including the optical fiber. It is quite obvious that optical measurements are needed at different levels of research and design, manufacturing and production of optical components and devices, installation and commissioning of optical fiber communication systems in the field. There is wide variety of optical measurement and test equipments used. These include optical power meter, optical oscilloscope and spectrum analyzer, optical time-domain reflectometer (OTDR), optical waveform analyzer, connector inspection microscope, dispersion analyzer, live fiber detector, talk-set, optical test set (combined source and power meter), etc. All these measurements are wavelength specific. Fiber attenuation and occurrence of faults in the optical fiber link is the main concern in ensuring the desired performance. There are several challenges involved with optical measurements like multiple wavelengths/channels, high optical power levels, need to carry tests remotely along with a high degree of automation.
关键词： OTDR,optical measurements,spectrum analyzer,optical power meter,optical fiber communications
更新于2025-09-12 10:27:22
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Micro Fabry-Pérot Interferometer at Rayleigh Range
摘要： The Fabry-Pérot interferometer is used in a variety of high-precision optical interferometry applications, such as gravitational wave detection. It is also used in various types of laser resonators to act as a narrow band filter. In addition, ultra-compact Fabry-Pérot interferometers are used in the optical resonators of semiconductor lasers and fiber-optic systems. In this work, we developed a micro-scale Fabry-Pérot interferometer that was constructed within the Rayleigh range of the optical focusing system. The high precision that is conventionally required for the optical parallelism and the surface accuracy of the mirrors was not so critical for this type of Fabry-Pérot interferometer. The interferometer was constructed using a gold-coated silicon microcantilever with reflectivity of 92% and a dielectric multilayer flat mirror with reflectivity of 85%. The focal spot size of the laser beam is 20 μm and the cavity length is approximately 20 μm. The finesse was measured to be approximately 25. The interferometric characteristics of the device were consistent with the theoretically calculated performance. The developed micro Fabry-Pérot interferometer has the potential to make a marked contribution to advances in optical measurements in various micro sensing system.
关键词： microcantilever,Rayleigh range,optical measurements,optical interferometry,Fabry-Pérot interferometer
更新于2025-09-10 09:29:36
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Acoustic and optical methods to infer water transparency at Time Series Station Spiekeroog, Wadden Sea
摘要： Water transparency is a primary indicator of optical water quality that is driven by suspended particulate and dissolved material. A data set from the operational Time Series Station Spiekeroog located at a tidal inlet of the Wadden Sea was used to perform (i) an inter-comparison of observations related to water transparency, (ii) correlation tests among these measured parameters, and (iii) to explore the utility of both acoustic and optical tools in monitoring water transparency. An Acoustic Doppler Current Profiler was used to derive the backscatter signal in the water column. Optical observations were collected using above-water hyperspectral radiometers and a submerged turbidity metre. Bio-fouling on the turbidity sensors optical windows resulted in measurement drift and abnormal values during quality control steps. We observed significant correlations between turbidity collected by the submerged metre and that derived from above-water radiometer observations. Turbidity from these sensors was also associated with the backscatter signal derived from the acoustic measurements. These findings suggest that both optical and acoustic measurements can be reasonable proxies of water transparency with the potential to mitigate gaps and increase data quality in long-time observation of marine environments.
关键词： optical measurements,acoustic backscatter,water transparency,Wadden Sea,turbidity
更新于2025-09-09 09:28:46