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Laser-Damage Attack Against Optical Attenuators in Quantum Key Distribution
摘要： Many quantum key distribution systems employ a laser followed by an optical attenuator to prepare weak coherent states in the source. Their mean photon number must be precalibrated to guarantee the security of key distribution. Here we experimentally show that this calibration can be broken with a high-power laser attack. We test four fiber-optic attenuator types used in quantum key distribution systems, and find that two of them exhibit a permanent decrease in attenuation after laser damage. This results in higher mean photon numbers in the prepared states and may allow an eavesdropper to compromise the key.
关键词： laser damage,optical attenuator,quantum key distribution,security
更新于2025-09-19 17:13:59
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Non-Contact Damage Detection under Operational Conditions with Multipoint Laservibrometry
摘要： Scanning laser–Doppler vibrometry (SLDV) can localize and visualize damages in mechanical structures. In order to enable scanning, it is necessary to repeat the vibration. Therefore, this technique is not suited to detect emerging hazards in working machinery that change the vibration behavior. A common technique for such cases is monitoring the vibration excited by machine operation with accelerometers. This technique requires mechanical coupling between sensors and the measurement object, which in?uences the high-frequency vibration responses. However, in the low-frequency range, local damages do not shift resonances or distort operational de?ection shapes (ODS) signi?cantly. These alterations in the vibration behavior are tiny and hard to detect. This paper shows that multipoint laservibrometry (MPV) with laser excitation can measure these e?ects e?ciently, and it further demonstrates that damages in?uence ODSs at frequencies above 20 kHz much stronger than at frequencies below 20 kHz. In addition, ODS-based damage indices are discussed; these are highly sensitive to minute visible changes of the ODSs. In order to enhance the sensitivity of hazard detection, the response vector assurance criterion value is computed and evaluated during operation. The capabilities and limitations of the methodology on the example of a cantilever with manually emerging damage are demonstrated.
关键词： structural health monitoring,multipoint laser-Doppler vibrometer,operational de?ection shape,operational condition,damage detection,laser–Doppler vibrometry,non-destructive testing,laser ablation
更新于2025-09-19 17:13:59
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[Laser Institute of America ICALEO? 2014: 33rd International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - San Diego, California, USA (October 19–23, 2014)] International Congress on Applications of Lasers & Electro-Optics - Laser microjet? cutting of up to 3 mm thick sapphire
摘要： The Laser Microjet? is a world-wide patented technology which uses ns-laser pulses which is guided to the work piece in a water jet. The sample is therefore cooled by the water and thermal damage during cutting is reduced which is relevant for metals and semiconductor materials. For the case of sapphire cutting this leads to lower thermal load of the samples and therefore no cracking during cutting. Sapphire cutting was until now not possible with the Laser Microjet? although it is used for micro machining of a lot of other materials like semiconductors, metals, diamond and ceramics. Cutting up to 3 mm thick sapphire with parallel walls with a roughness of < 0.5 μm and a kerf width of < 100 μm is achieved. The cutting speed of up to 0.1 mm/s for 1 mm samples has been achieved. The cut samples exhibit parallel walls which is a big advantage of the Laser Microjet? technology compared to other laser cutting technologies, not only for sapphire. The edges at the front side exhibit high quality with a radius of curvature of less than 20 μm and without any chipping. The back side quality still needs to be improved although chips with less than < 20 μm are already achievable. For laser cutting of sapphire high peak intensities are required in order to reach sufficient high absorption of the laser radiation and achieve material ablation. The process is not yet fully understood. It is expected that the water jet interaction with the material plays an important role together with laser light-material interaction. The geometry of the kerf of the work piece has a strong influence on the cutting process. Water jet interruptions due to e.g. non planar surfaces lead to loss of energy on the way to the work piece and therefore interruption of the absorption and ablation process. That is why certain processing strategies are necessary to achieve cutting for samples with the thickness of 3 mm. We expect to be able to cut even thicker samples of > 5 mm as well as further improve the backside edge quality in the future.
关键词： high peak intensities,thermal damage reduction,water jet coupled laser,Laser Microjet?,sapphire cutting
更新于2025-09-19 17:13:59
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Corneal Inlay Damage After Cosmetic Laser Treatment of the Eyelid With Long-Pulsed Nd:YAG Laser
摘要： IMPORTANCE Protective eyewear or corneal shields are recommended during cosmetic facial laser treatment. OBJECTIVE To describe the occurrence of corneal inlay damage following treatment to the eyelids and face with an Nd:YAG laser. DESIGN, SETTING, AND PARTICIPANTS This observational case report includes a single incident case cared for at a tertiary care center. A 58-year-old man who had undergone bilateral uncomplicated myopic laser in situ keratomileusis surgery in 2003 and corneal inlay implant in the nondominant left eye in 2013 experienced decreased visual acuity (VA) and pain in the left eye after the application of 2 passes of the Nd:YAG laser to his face and both eyelids for facial tightening. At presentation, the uncorrected VA was counting fingers OS and 20/20 OD. Slitlamp biomicroscopy showed a corneal epithelial defect overlying a deformed corneal inlay, peripheral scattered pigmentary deposits, corneal haze, and brown discoloration of the lamellar pocket of the inlay. He underwent explant of the inlay and debridement 48 hours later because of deteriorating VA and increasing corneal haze. EXPOSURE Application of long-pulsed Nd:YAG laser at 1064 nm to the middle one-third of both upper eyelids and the periorbital region in a man with a corneal inlay implant. Corneal shields were not worn during the procedure. The peak penetration depth of this laser system is approximately 4 mm. The mean (SD) thickness of the upper eyelid in Asian eyes is 1.127 (0.238) mm. MAIN OUTCOMES AND MEASURES Improvement of corneal inlay damage. RESULTS In this 58-year-old man, 3 months after the inlay explant, the intrastromal discoloration had resolved. There was still residual corneal haze, but the patient was able to achieve a best-corrected VA of 20/25 OS for distance and J3 (Snellen equivalent, 20/30) OS for near. CONCLUSIONS AND RELEVANCE Although the exact cause and effect cannot be determined from a single case, our findings suggest that a history of corneal inlay implant should be asked about prior to any long-pulsed Nd:YAG laser treatment to the periorbital skin and eyelids. Furthermore, these findings suggest that laser treatment to the eyelids should be avoided and that protective eyewear or corneal shields are recommended during cosmetic facial laser treatment in all patients.
关键词： corneal inlay damage,Nd:YAG laser,corneal shields,cosmetic laser treatment,protective eyewear
更新于2025-09-19 17:13:59
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Comparison of A 1940 nm Thulium-Doped Fiber Laser and A 1470 nm Diode Laser for Cutting Efficacy and Hemostasis in A Pig Model of Spleen Surgery
摘要： Partial and total splenectomies are associated with a high risk of substantial blood loss. Lasers operating at wavelengths strongly absorbed by water have the potential to improve hemostasis and cut while providing a narrow zone of thermal damage. The aim of this study is to compare a thulium-doped fiber laser (TDFL) emitting a wavelength of 1940 nm and a diode laser (DL) operating at 1470 nm for spleen surgery in a pig model. A partial splenectomy and spleen incisions were made in 12 animals using the two laser devices. The hemostasis was evaluated visually during surgeries. Post-mortem and histopathological evaluations were done on days 0, 7, and 14 following surgery. Neither TDFL nor DL caused bleeding on day 0 or delayed bleeding. On day 14, pale streaks at the site of incision were slightly wider after cutting with DL than with TDFL. Histological analysis revealed a carbonized zone with exudation and a deeper zone of thermal tissue damage on day 0. The width of the thermal changes was 655.26 ± 107.70 μm for TDFL and 1413.37 ± 111.85 μm for DL. On day 7, a proliferation of fibroblasts and splenocytes was visible, as well as a formation of multinucleated giant cells adjacent to the residues of carbonization. The zone of thermal damage was broader for DL (1157.5 ± 262.77 μm) than for TDFL (682.22 ± 116.58 μm). On day 14, cutting sites were filled with connective and granulation tissues with the residues of carbonization. The zone of thermal damage was narrower for TDFL (761.65 ± 34.3 μm) than for DL (1609.82 ± 202.22 μm). Thus, both lasers are efficient in spleen surgery, providing good hemostasis. However, TDFL produces a narrower zone of thermal damage, which suggests its better efficiency for spleen surgery, especially when performing more precise procedures.
关键词： thulium-doped fiber laser (1940 nm),pig model of spleen surgery,diode laser (1470 nm),thermal damage zone,partial splenectomy,hemostasis
更新于2025-09-19 17:13:59
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Intramolecular Charge Transfer in 5-Halogen Cytidines Revealed by Femtosecond Time-resolved Spectroscopy
摘要： Ultraviolet radiation induced damage to DNA/RNA can lead to chemical modifications to the nucleosides and understanding the excited states involved is the key to reveal the mechanism of those reactions. 5-Halogen cytidines are metabolized DNA/RNA nucleoside byproducts that exhibit very important biological functions in the process of nucleic acid methylation as well as DNA/RNA damage repairing. However, despite the accumulation of knowledge about their biological functions, effect of halogen substitution on the excited states of canonical nucleoside have not received much attention. In this work, excited-state dynamics of 5-fluorocytidine, 5-chlorocytidine and 5-bromocytidine is investigated. Excitation at 295 nm results a bifurcation event that leads to sub-picosecond decay to ground state and population of intramolecular charge transfer states which have several to tens of picosecond lifetimes. The results elucidate the general excited state relaxation pathways in 5-halogen cytidines and the intrinsic charge transfer state may affect the halogen bonding that stabilizes DNA and protein structures when 5-halogen cytidines are excited.
关键词： Excited-state dynamics,Femtosecond Time-resolved Spectroscopy,DNA/RNA damage,5-Halogen Cytidines,Intramolecular Charge Transfer
更新于2025-09-19 17:13:59
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High-repetition-rate laser-induced damage of indium tin oxide films and polyimide films at a 1064 nm wavelength
摘要： Experiments and thermal modeling of indium tin oxide transparent conductive thin film and polyimide alignment thin film coated on fused silica substrates damaged with a 1064 nm high-repetition-rate laser are described. High-repetition-rate laser irradiation results in damaged morphologies of the bulge at low laser power density and formation of a pit in the center of the bulge at higher laser power density. The damage process that is consistent with the observations as a function of laser power density and irradiation time is related to thermal effect. Simulation of the temperature-rise by exposure to high-repetition-rate laser describes the thermal effect with different pulse oscillation.
关键词： high-repetition-rate laser,polyimide,laser-induced damage,thermal modeling,indium tin oxide
更新于2025-09-19 17:13:59
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A hybrid deep learning architecture for classification of microscopic damage on National Ignition Facility laser optics
摘要： Accurately classifying microscopic damage helps automate the repair and recycling of National Ignition Facility optics and informs the study of damage initiation and growth. This complex 12-class problem previously required human experts to distinguish and label the various damage morphologies. Finding image analysis methods to extract and calculate distinguishing features would be time consuming and challenging, so we sought to automate this task by using convolutional neural networks (CNNs) pretrained on the ImageNet database to take advantage of its automated feature discovery and extraction. We compared three model architectures on this dataset and found the one with highest overall accuracy, 99.17%, was a novel hybrid architecture, one in which we removed the final decision-making layer of the deep learner and replaced it with an ensemble of decision trees (EDT). This combines the power of feature extraction by CNNs with the decision-making strength of EDT. The accuracy of the hybrid architecture over the deep learning alone is shown to be significantly improved. Furthermore, we applied this novel hybrid architecture to an entirely different dataset, one containing images of repaired damage sites, and improved on the previously published findings, also with a demonstrably significant increase in accuracy over using the deep learner alone.
关键词： machine learning,laser optic damage,deep learning,automation
更新于2025-09-19 17:13:59
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Ultrahigh Resolution Pulsed Laser-Induced Photoacoustic Detection of Multi-Scale Damage in CFRP Composites
摘要： This paper presents a photoacoustic non-destructive evaluation (pNDE) system with an ultrahigh resolution for the detection of multi-scale damage in carbon fiber-reinforced plastic (CFRP) composites. The pNDE system consists of three main components: a picosecond pulsed laser-based ultrasonic actuator, an ultrasound receiver, and a data acquisition/computing subsystem. During the operation, high-frequency ultrasound is generated by pulsed laser and recorded by an ultrasound receiver. By implementing a two-dimensional back projection algorithm, pNDE images can be reconstructed from the recorded ultrasound signals to represent the embedded damage. Both potential macroscopic and microscopic damages, such as surface notches and delamination in CFRP, can be identified by examining the reconstructed pNDE images. Three ultrasonic presentation modes including A-scan, B-scan, and C-scan are employed to analyze the recorded signals for the representation of the detected micro-scale damage in two-dimensional and three-dimensional images with a high spatial resolution of up to 60 μm. Macro-scale delamination and transverse ply cracks are clearly visualized, identifying the edges of the damaged area. The results of the study demonstrate that the developed pNDE system provides a non-destructive and robust approach for multi-scale damage detection in composite materials.
关键词： composites,non-destructive testing,photoacoustic,multi-scale,ultrasonic representation,embedded damage
更新于2025-09-19 17:13:59
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Restoration of Steam Turbine Last Stage Rotor Blades by Laser Surfacing
摘要： Technology is provided for restoring erosion damaged rotor blades of the last stages of steam turbine low-pressure cylinders (LPC) using laser-powder surfacing and application of an erosion-resistant coating. For this method there is typically low heat input into the blade basic metal, which improves its restoration reliability. Results are obtained for comprehensive experimental studies on specimens and blades, confirming the high quality of welded joints obtained by laser surfacing of nickel alloy proposed for restoring the blade profile of blade steels éI961-Sh and 15Kh11MF-Sh, and application of a stellite-6 erosion-resistant coating. The possibility is concluded of using the laser-powder surfacing method during refurbishment of steam turbine LPC rotor blades.
关键词： blade restoration,erosion damage,rotor blades,steam turbine,laser-powder surfacing
更新于2025-09-16 10:30:52