- 标题
- 摘要
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- 实验方案
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Nonlinear Optics || Optically Induced Damage and Multiphoton Absorption
摘要： A topic of great practical importance is optically induced damage of optical components. Optical damage is important because it ultimately limits the maximum amount of power that can be transmitted through a particular optical material. Optical damage thus imposes a constraint on the efficiency of many nonlinear optical processes in that it limits the maximum field strength E that can be used to excite the nonlinear response. In this context, it is worth pointing out that present laser technology can produce laser beams of sufficient intensity to exceed the damage thresholds of all known materials.
关键词： multiphoton absorption,nonlinear optical processes,laser technology,optical damage,damage thresholds
更新于2025-09-23 15:21:01
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[Lecture Notes in Computer Science] Pattern Recognition and Computer Vision Volume 11256 (First Chinese Conference, PRCV 2018, Guangzhou, China, November 23-26, 2018, Proceedings, Part I) || Damage Online Inspection in Large-Aperture Final Optics
摘要： Under the condition of inhomogeneous total internal reflection illumination, a novel approach based on machine learning is proposed to solve the problem of damage online inspection in large-aperture final optics. The damage online inspection mainly includes three problems: automatic classification of true and false laser-induced damage (LID), automatic classification of input and exit surface LID and size measurement of the LID. We first use the local area signal-to-noise ratio (LASNR) algorithm to segment all the candidate sites in the image, then use kernel-based extreme learning machine (K-ELM) to distinguish the true and false damage sites from the candidate sites, propose autoencoder-based extreme learning machine (A-ELM) to distinguish the input and exit surface damage sites from the true damage sites, and finally propose hierarchical kernel extreme learning machine (HK-ELM) to predict the damage size. The experimental results show that the method proposed in this paper has a better performance than traditional methods. The accuracy rate is 97.46% in the classification of true and false damage; the accuracy rate is 97.66% in the classification of input and exit surface damage; the mean relative error of the predicted size is within 10%. So the proposed method meets the technical requirements for the damage online inspection.
关键词： Size measurement,Damage online inspection,Classification,Laser-induced damage,Machine learning
更新于2025-09-23 15:21:01
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Development of a defect recognition algorithm for visual laser-induced damage detection
摘要： Laser-induced damage is defined as a permanent detrimental change in the characteristics of an optical element caused by a laser beam. This change can be observed by many different inspection techniques, of which optical and phase imaging microscopic techniques have superior sensitivity. However, such examinations conducted by human operators are relatively slow and subjective—so they cannot be used for online damage monitoring purposes, whereas automatic inspection systems have advantages in terms of sensitivity, reliability, and speed. In this paper we introduce a new method for the computer-aided recognition of damaged sites based on visual images taken from the sample surface by a CCD camera. The evaluation procedure is performed by a computer algorithm, which consists of exact, statistically established steps. It includes noise reduction by considering the statistical behavior of photon noise. Besides, it takes into account the spatial extent of a damage spot by nonlinear image filtering to separate damage-indicating intensity changes from random noise. This mimics the ability of the human eye to distinguish features from their surroundings. The evaluation algorithm is built of computationally less demanding mathematical operations to enable fast execution which is vital for monitoring at high repetition rates. The proposed method was tested on a sizeable dataset of images yielding 98.8% of damage detection efficiency. It was also compared to a generally used visual laser damage detection procedure, which has a success rate of 88.6%. This yields one order of magnitude reduction in the number of undetected damaged sites.
关键词： image filter,Chebyshev’s theorem,laser-induced damage,machine vision,poisson noise
更新于2025-09-23 15:21:01
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Using differential spread laser infrared thermography to detect delamination and impact damage in CFRP
摘要： In this paper, the feasibility of differential spread laser infrared thermography (DSLIT) to detect delamination and impact damage in carbon fiber reinforced polymer (CFRP) is investigated. The proposed method can significantly eliminate the influence of the uneven laser energy distribution and improve the detectability of laser infrared thermography. First, numerical simulation is carried out following the procedure of DSLIT to verify the feasibility of this method. Secondly, through experiments on the detection of defects both in practical aviation CFRP and common CFRP, the feasibility of DSLIT is confirmed. For the common CFRP, this technique has excellent performance: a defect at a depth of 2.5 mm was detected successfully, with the width-to-depth ratio reaches to 2.4. Comparatively speaking, the defect detection results for the aviation CFRP are not as good as those for the common CFRP. However, defects at a depth of 1.125 mm were detected, with the width-to-depth ratio reaching 2.67. In addition, defects caused by a low-velocity impact in practical aviation CFRP were successfully detected. Finally, the thermal data were processed by image processing methods such as sequence differential preprocessing (SDP), phase analysis (PA) and principal component analysis (PCA) to enhance the defect imaging results.
关键词： Laser infrared thermography,Delamination,Impact damage,Differential processing,Aviation CFRP
更新于2025-09-23 15:21:01
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Residual stress analysis of thin film photovoltaic cells subjected to massive micro-particle impact
摘要： Residual stresses play a crucial role in both light-electricity conversion performances and the lifespan of photovoltaic (PV) cells. In this paper, the residual stress of triple junction cells (i.e. GaInP/GaInAs/Ge) induced by laser-driven massive micro-particle impact is analyzed with a novel method based on backscattering Raman spectroscopy. The impact process, which induces damage to the PV cells and brings the residual stress, is also investigated by optical microscopy (OM) and Scanning Electron Microscopy (SEM). The results show that the PV cells would exhibit various damage patterns. At the same time, strong residual stresses up to hundreds of MPa introduced in the damaged PV cells after impact have been analysis, providing an effective perspective to better understand the damage behavior and residual stress features of PV cells during their service life.
关键词： Damage behavior,Residual stress,Photovoltaic cells,Micro-particle impact,Raman spectroscopy
更新于2025-09-23 15:21:01
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Structural dynamics in proteins induced by and probed with X-ray free-electron laser pulses
摘要： X-ray free-electron lasers (XFELs) enable crystallographic structure determination beyond the limitations imposed upon synchrotron measurements by radiation damage. The need for very short XFEL pulses is relieved through gating of Bragg diffraction by loss of crystalline order as damage progresses, but not if ionization events are spatially non-uniform due to underlying elemental distributions, as in biological samples. Indeed, correlated movements of iron and sulfur ions were observed in XFEL-irradiated ferredoxin microcrystals using unusually long pulses of 80 fs. Here, we report a femtosecond time-resolved X-ray pump/X-ray probe experiment on protein nanocrystals. We observe changes in the protein backbone and aromatic residues as well as disulfide bridges. Simulations show that the latter’s correlated structural dynamics are much slower than expected for the predicted high atomic charge states due to significant impact of ion caging and plasma electron screening. This indicates that dense-environment effects can strongly affect local radiation damage-induced structural dynamics.
关键词： plasma electron screening,radiation damage,ion caging,structural dynamics,protein nanocrystals,X-ray free-electron lasers
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Desynchronization of Pulsed Driving in the Formation of Soliton Kerr Frequency Combs
摘要： MRED is a Python-language scriptable computer application that simulates radiation transport. It is the computational engine for the on-line tool CRèME-MC. MRED is based on c++ code from Geant4 with additional Fortran components to simulate electron transport and nuclear reactions with high precision. We provide a detailed description of the structure of MRED and the implementation of the simulation of physical processes used to simulate radiation effects in electronic devices and circuits. Extensive discussion and references are provided that illustrate the validation of models used to implement specific simulations of relevant physical processes. Several applications of MRED are summarized that demonstrate its ability to predict and describe basic physical phenomena associated with irradiation of electronic circuits and devices. These include effects from single particle radiation (including both direct ionization and indirect ionization effects), dose enhancement effects, and displacement damage effects. MRED simulations have also helped to identify new single event upset mechanisms not previously observed by experiment, but since confirmed, including upsets due to muons and energetic electrons.
关键词： single event upset,single event effects,total ionizing dose,radiation effects,Displacement damage,Monte Carlo,radiation transport,MRED
更新于2025-09-23 15:21:01
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[IEEE 2018 International Conference on Radiation Effects of Electronic Devices (ICREED) - Beijing, China (2018.5.16-2018.5.18)] 2018 International Conference on Radiation Effects of Electronic Devices (ICREED) - Study on the Tracking & Pointing Accuracy Degeneration of Optical Communication System for CMOS Sensor Irradiation Damage
摘要： The CMOS sensor in space optical communication system may generate irradiation-induced noise, leading to deviation of image centroid. Based on test data, simulated defect spots have been used for calculating the value by grey-level centroid algorithm. It shows that both the amount and position of defect pixels contribute to deviation of image centroid and the accuracy decreasing.
关键词： tracking & pointing accuracy,CMOS sensor,optical communication,gray centroid algorithm,irradiation damage
更新于2025-09-23 15:21:01
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Proton-induced displacement damage in ZnO thin film transistors: Impact of damage location
摘要： We have investigated the displacement damage (DD) effect on the electrical characteristics of ZnO thin film transistors (TFTs) based on its location of origin in the device structure. The area subjected to the maximum proton dose induces a maximum DD effect in that particular location. ZnO TFTs with two different passivation layer thicknesses were prepared to obtain maximum proton dose distribution in either the ZnO channel layer or ZnO/SiO2 interface. The devices were irradiated by a proton beam with an energy 200 keV and 1 × 1014 protons/cm2 fluence. Transport of Ions in Matter (TRIM) simulation, followed by calculation of depth distribution of the nonionizing energy loss (NIEL), illustrated different proton dose distribution profiles and NIEL profiles along the depth of the device for these two types of samples. The sample with the maximum proton dose peaks at the ZnO/SiO2 interface exhibited a significant degradation in device electrical characteristics as compared to the negligible degradation of the sample when the maximum proton dose was absorbed in the ZnO layer. Therefore, the investigation into the radiation hardness of proton-irradiated ZnO TFTs is non-trivial since the displacement damage induces drastic changes on the device characteristics based on the damage location.
关键词： ZnO,NIEL,Displacement damage,Thin-film transistors,Proton radiation effects
更新于2025-09-23 15:21:01
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Different material modifications in laser-induced damage of optical films in air and vacuum environments
摘要： A combination study of material modifications for the catastrophic laser-induced damage by 12 ns, 1064 nm laser pulse irradiation was investigated in air and vacuum environments. The samples were observed by optical microscope, scanning electron microscopy, laser micro-Raman spectroscopy, photoluminescence spectrum; moreover 2D numerical calculations were performed. According to our results, vacuum pumping induced higher laser field intensities, accompanying with more absorption of laser energy in the laser-induced damage process. All of these resulted in the material melting and subsequent re-solidification in the laser-damaged core in vacuum. While, in the air conditions, plasma expanding due to material heating and associated thermal expansion induced a large stress field, which caused the material deformation and formation of delamination and crack in the laser-damage region.
关键词： Vacuum,Photoluminescence spectrum,Laser-induced damage,Laser micro-Raman spectroscopy
更新于2025-09-23 15:21:01