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Selection of optimal wavelengths for optical soiling modelling and detection in photovoltaic modules
摘要： Soiling impacts the photovoltaic (PV) module performance by reducing the amount of light reaching the photovoltaic cells and by changing their external spectral response. Currently, the soiling monitoring market is moving toward optical sensors that measure transmittance or reflectance, rather than directly measuring the impact of soiling on the performance of photovoltaic modules. These sensors, which use a single optical measurement, are not able to correct the soiling losses that depend on the solar irradiance spectra and on the spectral response of the monitored PV material. This work investigates methods that can improve the optical detection of soiling by extracting the full soiling spectrum profiles using only two or three monochromatic measurements. Spectral transmittance data, measured with a spectrophotometer and collected during a 46-week experimental soiling study carried out in Ja?en, Spain, was analysed in this work. The use of a spectral profile for the hemispherical transmittance of soiled PV glass is found to significantly improve the soiling detection, returning the lowest errors independently of the PV materials and irradiance conditions. In addition, this work shows that it is also possible to select the measurement wavelengths to minimize the soiling loss detection error depending on the monitored PV semiconductor material (silicon, CdTe, a-Si, CIGS and a representative perovskite). The approaches discussed in this work are also found to be more robust to potential measurement errors compared to single wavelength measurement techniques.
关键词： Soiling,Dust,Optical modelling,Photovoltaic,Spectral losses,Reliability
更新于2025-09-23 15:21:01
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Evaluation of nitric oxide laser-induced fluorescence thermometry techniques in a hypersonic boundary layer
摘要： Nitric oxide planar laser-induced fluorescence was performed to measure the wall-normal distribution of static temperature through a hypersonic boundary layer. A 10-degree half-angle wedge model was oriented at a 5-degree angle of attack in the NASA Langley 31-in Mach 10 facility, resulting in a 5-degree flow turning angle and an edge Mach number of 7.6. Nitric oxide was seeded through a spanwise slot into the boundary layer upstream of the imaging region and was excited with a pulsed ultraviolet planar laser sheet. The laser was spectrally scanned across six fluorescence transitions in the (0, 0) band of the A2Σ+–X2Π system. Eighteen thermometry methods were assessed through comparison to predictions of the temperature field from computational fluid dynamics simulations. The effect of spectral resolution and laser linewidth on measurement uncertainty was also investigated. The most accurate technique was spectral peak thermometry, which achieved an accuracy of ± 31.6 K (12.6% error relative to CFD temperature). The spectral peak thermometry technique required a minimum spectral resolution between 0.074 and 0.102 cm?1 to extract meaningful temperature information from the spectra and a maximum laser linewidth of 0.49 cm?1.
关键词： Laser linewidth,Thermometry,Spectral resolution,Planar laser-induced fluorescence,Hypersonic boundary layer,Nitric oxide
更新于2025-09-23 15:21:01
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Spectral weights of mixed coupled plasmon modes in Dirac electron systems with different dimensionality
摘要： We study the effects of coupling between plasmon modes by the long-range Coulomb electron-electron interaction for a system consisting of a two-dimensional (2D) system of Dirac electrons embedded in three-dimensional (3D) Dirac semimetal. We obtain the dispersions of coupled plasmon modes for various separations of the subsystems. The coupled modes become more separated with decreasing the separation between two subsystems as the coupling increases due to the enhanced Coulomb interaction between electrons from different subsystems. We also demonstrate how the coupling affects the spectral weights of the obtained modes in two subsystems for different separations. In the 2D subsystem both coupled modes have finite weights for small wavenumbers, while for large wavenumbers only the upper mode persists. On the other hand, in the bulk this mode takes most of the spectral weight for small wavenumbers, while for large wavenumbers the lower mode is more pronounced.
关键词： plasmon modes,Coulomb interaction,spectral weights,Dirac electron systems
更新于2025-09-23 15:21:01
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Planar multifrequency mid-IR microwave-pumped lasers
摘要： The characteristics of planar repetitively pulsed diffusion-cooled HF, DF, HF – DF, Xe, and HF – DF – Xe(Kr) lasers pumped by a microwave discharge (2.45 GHz) are studied depending on the pump pulse duration (10 – 40 ms) and repletion rate (50 – 400 Hz), as well as on the composition and pressure of the working gas mixture (30 – 200 Torr) at low (to 0.6 L s–1) gas flow rates. It is demonstrated for the first time that a HF – DF – Xe gas-discharge laser may simultaneously operate as a HF – DF chemical molecular laser and a recombination laser based on xenon atom transitions and generate broadband (octave) radiation in the range 2.0 – 4.2 mm with an average output power of 43 mW and an efficiency of 0.9 %. With substitution of xenon for krypton, lasing in a HF – DF – Kr laser is obtained at wavelengths of 2.52 – 4.15 mm. Lasing in a HF – DF laser was achieved simultaneously in two spectral regions (2.7 – 2.9 and 3.6 – 4.2 mm) with an output power of ~50 mW. It is found that a decrease in the pump pulse duration with a simultaneous increase in the pulse repletion rate for retaining the average energy deposition leads to an increase in the average output power and efficiency of the laser. At low pulse repetition rates (50 – 100 Hz) and a low gas mixture flow rate, helium buffer gas can be effectively substituted for neon. Operation of the Xe laser was achieved in the spectral range 2.03 – 3.65 mm with an average output power of 580 Mw at a pump pulse duration of 20 ms, a pulse repetition rate to 10 kHz, and a maximum efficiency of 55 %. The obtained experimental results demonstrate the possibility of creating broadband HF – DF – Xe lasers emitting in the frequency range 2 – 4 mm with a desired ratio of intensities in different spectral ranges.
关键词： gas discharge,spectral characteristics,planar HF – DF – Xe laser,multifrequency lasing
更新于2025-09-23 15:21:01
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[IEEE 2020 Systems of Signals Generating and Processing in the Field of on Board Communications - Moscow, Russia (2020.3.19-2020.3.20)] 2020 Systems of Signals Generating and Processing in the Field of on Board Communications - Spectral Efficiency and Information Transfer Rate Over Optical Fibers in Spatial Parallelism
摘要： Spatial parallelism contribution to optical fibers spectral efficiency and to signal transfer rate is being estimated. Parallelism multiplier system parameter is introduced. Using this parameter analytical expressions are constructed to determine the optical fibers spectral efficiency and information transfer rate. Examples of spatial parallelism of optical signal transmission in few-mode and multicore fibers are given.
关键词： spatial parallelism,information transfer rate,optical fiber,spectral efficiency,parallelism multiplier
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 2nd Ukraine Conference on Electrical and Computer Engineering (UKRCON) - Lviv, Ukraine (2019.7.2-2019.7.6)] 2019 IEEE 2nd Ukraine Conference on Electrical and Computer Engineering (UKRCON) - Calculation of Spectral Greena??s Function and Its Asymptotical Behavior for Sheet Electric Current in Two-Layer Dielectric Waveguide
摘要： Structures with patches placed on the interfaces in a two-layered dielectric waveguide are promising to be used in different applications at THz waves. To realize the method of moments (MoM) solution in the spectral domain spectral Green’s functions (GFs) for sheet electric currents on the interfaces of the two-layer dielectric cylindrical waveguide are needed. This paper presents the way to enhance the MoM solution efficiency by extracting an asymptotic behavior of the spectral GF which depends on two variables: the propagation constant and the azimuth index. Here asymptotic spectral GFs are constructed and calculated when electrical sheet current is placed on different interfaces.
关键词： two-layered cylindrical dielectric waveguide,spectral Green’s function,cylindrically conformal antenna
更新于2025-09-23 15:21:01
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Continuous-wave dual-wavelength operation of the in-band diode-pumped Nd:GdVO4/Nd:YVO4 composite laser with controllable spectral power ratio
摘要： Controllable continuous-wave dual-wavelength laser operation of a Nd:GdVO4/Nd:YVO4 composite crystal at 1063 and 1064 nm was demonstrated using in-band diode pumping around 912 nm. The spectral power ratio of the two laser wavelengths could be adjusted simply by controlling the pump wavelength of the laser diode via temperature. The laser produced the maximum total output power of 4.48 W. The maximum slope and optical-to-optical efficiency with respect to the absorbed pump power were 43.8% and 38.8%, respectively.
关键词： in-band diode pumping,Nd:GdVO4/Nd:YVO4 composite crystal,dual-wavelength laser,spectral power ratio,continuous-wave operation
更新于2025-09-23 15:21:01
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A Study of the Optical and Acoustic Spectral Characteristics by Laser Breakdown of Water in an Ultrasonic Field
摘要： A strong dependence of the optical breakdown in a liquid in the ultrasonic field on the amplitude and frequency of ultrasound is demonstrated. The increase in the intensity of spectral lines of potassium and oxygen during the optical breakdown is detected by the increase in the amplitude and frequency of ultrasound. At the same time, the effect of saturation is observed at high frequencies (above 200 kHz) and for high ultrasonic powers, when the growth in the intensity of spectral lines slows sharply down. This shows that there is no necessity to use high powers and frequencies of ultrasound to study the opto-acoustic effects during optical breakdown in a liquid.
关键词： ultrasound,spectral lines,optical breakdown,laser-spark spectroscopy,opto-acoustic effects
更新于2025-09-23 15:21:01
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[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Narrow Linewidth Fiber Brillouin Ring Laser for Sensing Applications
摘要： A novel tunable, stable and low-noise Brillouin ring laser layout composed of a doubly-resonant short-cavity Brillouin ring laser (DR-SC) paired with an active wavelength stabilization setup is presented in this work. Measurements of temporal signal stability, relative intensity noise, spectral linewidth and tunability range yielded a marked improvement over the long-cavity version that we have previously reported, making the new layout a promising alternative for applications in fiber sensing and other fields that require highly coherent and stable tunable sources.
关键词： relative intensity noise,fiber sensing,Brillouin ring laser,tunable sources,spectral linewidth
更新于2025-09-23 15:21:01
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Roughness of surface decorated with randomly distributed pillars
摘要： We have presented a quantitative analysis of roughness of planar surfaces decorated with randomly distributed, cylindrical pillars, disks, or cavities. We have described the roughness in terms of the surface power spectral density (PSD). First, we have derived a general equation for the PSD of such surfaces. Then, we have found the PSD for the special case of statistically isotropic, circular areas. We have demonstrated that the PSD provides quantitative information on the radius of the circular area, dimensions of the pillar, and surface coverage. We have also discussed the numerical method of extracting the parameters from experimental PSD data obtained from discrete Fourier transform of surface scanning measurements.
关键词： Fourier transform,cylindrical pillars,surface roughness,random distribution,power spectral density
更新于2025-09-23 15:21:01