- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Irreversible Photobleaching of BAC-Si in Bi/Er Co-Doped Optical Fiber under 830 nm Pumping
摘要： A novel empirical data analysis methodology based on the random matrix theory (RMT) and time series analysis is proposed for the power systems. Among the ongoing research studies of big data in the power system applications, there is a strong necessity for new mathematical tools that describe and analyze big data. This paper used RMT to model the empirical data which also treated as a time series. The proposed method extends traditional RMT for applications in a non-Gaussian distribution environment. Three case studies, i.e., power equipment condition monitoring, voltage stability analysis and low-frequency oscillation detection, illustrate the potential application value of our proposed method for multi-source heterogeneous data analysis, sensitive spot awareness and fast signal detection under an unknown noise pattern. The results showed that the empirical data from a power system modeled following RMT and in a time series have high sensitivity to dynamically characterized system states as well as observability and efficiency in system analysis compared with conventional equation-based methods.
关键词： low frequency oscillation,non-Gaussian,static voltage stability,Random matrix theory,time series analysis,data mining,condition monitoring
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Laser Cutting and Micromachining for Localized and Targeted Solar Cell Characterization
摘要： High-order mode oscillation occurred in an S-band experimental klystron with 300 MHz instantaneous bandwidth. The cause of the oscillation was analyzed and simulated. A method was proposed to suppress the oscillation through adjusting the structure and size of a resonant cavity in the tube, in which the high-order mode frequency can obviously be changed and the variation of the fundamental mode frequency is very small. Improved designs for the resonant cavity with Ansoft HFSS code and corresponding experiment have been performed, which shows that the simulation results are in good agreement with the experimental measurements. The testing result of an experimental klystron with this improved resonant cavity indicates that the high-order mode oscillation can effectively be suppressed.
关键词： klystron,suppression,High-order mode,oscillation
更新于2025-09-19 17:13:59
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Doppler-shifted laser self-mixing interferometry for enhanced detection sensitivity
摘要： Laser self-mixing interferometry (SMI) is a well-known measurement technique having been applied to the fields of geometrical quantities detection, medical treatment and industry manufacturing. Its detection sensitivity can be improved by frequency shifting towards the laser’s relaxation oscillation frequency (ROF), which has always been implemented by a pair of acousto-optic modulators (AOM). This manuscript presents a novel method based on Doppler effect for frequency shifting, which is based on a rotating disk and has the advantages of convenient adjustment and low cost. The theoretical analysis in the form of Doppler shift and time-delayed rate equations is followed, and simulative and experimental results are included to prove its validity. To our knowledge, this technique has not been used in practice till now, and the proposed structure, with these advantages, can find significant applications in designing high performance SMI sensors, and can extend SMI measurement to more kinds of non-cooperative surfaces.
关键词： Self-mixing interferometry,signal to noise ratio,Doppler shift,sensitivity,relaxation oscillation frequency
更新于2025-09-19 17:13:59
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Observation of water droplets oscillation due to laser induced Marangoni convection
摘要： In this paper, using experimental characterizations, we explore the motion of water droplets suspended in mineral oil under exposure of a focused continuous wave (CW) fiber laser beam. The laser beam exposure heats the surrounding oil medium as well. The temperature gradient generates thermocapillary (or Marangoni) convection flows. This approach uses infrared laser-induced thermocapillary-driven flow for manipulation of droplets in the range of 10 to 30 μm in diameter. The droplets are trapped in the convection flow and travel with thermocapillary convection flow (depending on the droplet sizes) along the streamline with high speed. This motion is observed at a certain critical power of the laser. The behavior of a droplet in response to thermally induced convection can be considered. we also examined the oscillatory behavior of the droplet on the xy plane. As expected, oscillation frequency/amplitude are linearly correlated to the droplet size.
关键词： Convection,Fiber laser,Marangoni force,Manipulation,Oscillation frequency,Thermocapillary,Temperature gradient
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Narrow-Linewidth Photonic Microwave Generation Based on an Optically Injected Semiconductor Laser Subject to Subharmonic Modulation
摘要： We propose and experimentally demonstrate a scheme to acquire a narrow-linewidth photonic microwave based on an optically injected semiconductor laser (OISL) modulated by a subharmonic microwave from an (OEO). The microwave optoelectronic oscillation frequency generated by the OEO is 7.62 GHz, and the period-one (P1) oscillation frequency of the OISL is close to twice of it. Through modulating the OISL by a 1/2 subharmonic microwave generated by the OEO, the photonic microwave is locked at 15.24 GHz with a 3-dB linewidth about 1 kHz and a SSB phase noise of -94 dBc/Hz at offset frequency 10 kHz.
关键词： Optically injected semiconductor laser (OISL),Subharmonic microwave modulation,Optoelectronic oscillation (OEO)
更新于2025-09-16 10:30:52
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RF Frequency Synthesizer Based on Self-Mode-Locked Multimode Lasers
摘要： Low-noise local oscillators are very important in modern communication systems. To realize a stable solution with a limited size, symmetric multimode multi-section semiconductor laser pairs are reported in this paper for building a chip-level RF synthesizer. The symmetric laser structure utilizes a shared distributed Bragg reflector (DBR) and counterpropagating laser output with the help of an external feedback circuit to achieve self-mode-locking. The achieved phase noise performance is -92 dBc/Hz at a 10 kHz offset frequency for intermodal operation at 26.4 GHz using 5 locked modes, which is a 57 dB improvement compared to the free-running case. Moreover, an RF synthesizer covering frequencies of 11-13 GHz is realized based on the achieved mode-locked system using current tuning. The related phase noise of the laser pair beat-note output is -100 dBc/Hz at a 10 kHz offset of carrier frequencies of 11-13 GHz, which is 58 dB better than the phase noise of the beat-note output without mode-locking over 11-13 GHz.
关键词： timing jitters,EAM,PM,mode-locking,phase noise,SOA,self-mode-locked,DBR,frequency synthesizer,multimode semiconductor laser,intermodal oscillation
更新于2025-09-16 10:30:52
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Process stability and parameters optimization of narrow-gap laser vertical welding with hot wire for thick stainless steel in nuclear power plant
摘要： Incomplete fusion, pore and melt sagging are common defects for multi-layer narrow-gap laser welding with filler wire in vertical positions for large and heavy structures. This investigation showed that vertical-up laser welding had a lower sensitivity to pores than vertical-down welding, whereas increasing welding speed could improve welding stability and reduce the formation possibility of pores. For laser vertical welding with hot wire, surface tension transfer mode could effectively guarantee pre-heating of filler wire and achieve a stable welding process. The keyhole stability and melt flow varied with welding directions. The melt sagging defect was usually observed and mainly caused by the concentrated laser energy, which easily led to discontinuous weld bead. Laser beam oscillation technology increased laser melting area and promoted wetting behavior of filler wire with base metal. The weld width increased and concave weld metal surface was obtained with suitable process parameters. Narrow-gap welding process could be carried out at a small defocusing position with a lower laser power, further decreasing tendency of melt slagging. The 20-mm defect-free joint was obtained by vertical-up and vertical-down narrow-gap laser oscillation welding with hot wire.
关键词： Laser vertical welding,Beam oscillation,Narrow gap welding,Large structures,Process stability
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Optical-injection-seeded Optical Frequency Comb Generation Promoted by the Sub-harmonic Modulation
摘要： Generated optical frequency combs based on recycling frequency shift have more ultrashort optical pluses and better flatness, but suffer from uncertainty of phase relationship among the comb lines and also larger carrier noise [7]. In this work, we propose a new scheme for generating optical frequency comb based on a basic optical injection system assisted by the sub-harmonic modulation, which features with the simple configuration, good flatness, tunable and flexible comb spacing and comb lines, certainty of phase relationship and lower carrier noise.
关键词： sub-harmonic modulation,optical injection,nonlinear period-one oscillation state,Optical frequency comb
更新于2025-09-16 10:30:52
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Spatial distribution measurement of acoustic cavitation bubbles by laser backscattering with confocal optics
摘要： A three-dimensional measurement method for the spatial distribution of acoustic cavitation bubbles employing laser backscattering and confocal optics is proposed. A numerical simulation of the proposed method shows that the measurement system has FWHM resolutions of 26.5 mm perpendicular to the laser axis and 1.02 mm along the laser axis. The frequency components of the output that are integer multiples of the incident ultrasound frequency can be indicators of the existence of bubbles. The experimental evaluation shows that the proposed method has three-dimensional resolution. Although the proposed method can measure the three-dimensional distribution of bubbles, it cannot decompose the quantity and activity of bubbles. Both a large number of bubbles and violent bubble oscillation enlarge the frequency components. To decompose these parameters, further study of the relationship between the bubble oscillation and the frequency spectrum is required.
关键词： Bubble oscillation,Multibubble,Laser backscattering,Spatial distribution,Acoustic cavitation
更新于2025-09-16 10:30:52
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Plasmonic Effects of Dual-Metal Nanoparticle Layers for High-Performance Quantum Dot Solar Cells
摘要： To improve quantum dot solar cell performance, it is crucial to make efficient use of the available incident sunlight to ensure that the absorption is maximized. The ability of metal nanoparticles to concentrate incident sunlight via plasmon resonance can enhance the overall absorption of photovoltaic cells due to the strong confinement that results from near-field coupling or far-field scattering plasmonic effects. Therefore, to simultaneously and synergistically utilize both plasmonic effects, the placement of different plasmonic nanostructures at the appropriate locations in the device structure is also critical. Here, we introduce two different plasmonic nanoparticles, Au and Ag, to a colloidal PbS quantum dot heterojunction at the top and bottom interface of the electrodes for further improvement of the absorption in the visible and near-infrared spectral regions. The Ag nanoparticles exhibit strong scattering whereas the Au nanoparticles exhibit an intense optical effect in the wavelength region where the absorption of light of the PbS quantum dot is strongest. It is found that these dual-plasmon layers provide significantly improved short-circuit current and power conversion efficiency without any form of trade-off in terms of the fill factor and open-circuit voltage, which may result from the indirect contact between the plasmonic nanoparticles and colloidal quantum dot films.
关键词： Quantum dot solar cell,Plasmonic effect,Near-field oscillation,Colloidal quantum dot,Light scattering
更新于2025-09-16 10:30:52