The Experts below are selected from a list of 3720 Experts worldwide ranked by ideXlab platform
Stefan Nolte - One of the best experts on this subject based on the ideXlab platform.
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Enhancing precision in fs-Laser Material Processing by simultaneous spatial and temporal focusing
Light: Science & Applications, 2014Co-Authors: Robert Kammel, Roland Ackermann, Jens Thomas, Jörg Götte, Stefan Skupin, Andreas Tünnermann, Stefan NolteAbstract:Splitting an ultrashort pulse into its constituent colors prior to focusing can result in more precise and better-confined Materials Processing. Robert Kammel and co-workers used a grating to split a stream of 50 fs pulses from an amplified infrared mode-locked Laser into spectrally separated beamlets. This beam was focused in a water cell using a parabolic mirror in order to confirm the effectiveness of the scheme for pulse energies of up to 8 µJ. Numerical simulations and experiments show that this approach strongly confines the intensity to the resulting focal spot and reduces unwanted nonlinear side effects such as self-focusing, filamentation and supercontinuum generation. The researchers say that their work should lead to improvements in the high-precision Processing deep inside of transparent Materials and could be particularly beneficial for ophthalmic fs surgery. In recent years, femtosecond (fs)-Lasers have evolved into a versatile tool for high precision micromachining of transparent Materials because nonlinear absorption in the focus can result in refractive index modifications or Material disruptions. However, when high pulse energies or low numerical apertures are required, nonlinear side effects such as self-focusing, filamentation or white light generation can decrease the modification quality. In this paper, we apply simultaneous spatial and temporal focusing (SSTF) to overcome these limitations. The main advantage of SSTF is that the ultrashort pulse is only formed at the focal plane, thereby confining the intensity distribution strongly to the focal volume and suppressing detrimental nonlinear side effects. Thus, we investigate the optical breakdown within a water cell by pump-probe shadowgraphy, comparing conventional focusing and SSTF under equivalent focusing conditions. The plasma formation is well confined for low pulse energies
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Enhancing precision in fs-Laser Material Processing by simultaneous spatial and temporal focusing
Light: Science & Applications, 2014Co-Authors: Robert Kammel, Roland Ackermann, Jens Thomas, Jörg Götte, Stefan Skupin, Andreas Tünnermann, Stefan NolteAbstract:In recent years, femtosecond (fs)-Lasers have evolved into a versatile tool for high precision micromachining of transparent Materials because nonlinear absorption in the focus can result in refractive index modifications or Material disruptions. However, when high pulse energies or low numerical apertures are required, nonlinear side effects such as self-focusing, filamentation or white light generation can decrease the modification quality. In this paper, we apply simultaneous spatial and temporal focusing (SSTF) to overcome these limitations. The main advantage of SSTF is that the ultrashort pulse is only formed at the focal plane, thereby confining the intensity distribution strongly to the focal volume and suppressing detrimental nonlinear side effects. Thus, we investigate the optical breakdown within a water cell by pump-probe shadowgraphy, comparing conventional focusing and SSTF under equivalent focusing conditions. The plasma formation is well confined for low pulse energies
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enhancing precision in fs Laser Material Processing by simultaneous spatial and temporal focusing
Light-Science & Applications, 2014Co-Authors: Robert Kammel, Stefan Nolte, Roland Ackermann, Jens Thomas, Jörg Götte, Stefan Skupin, Andreas TünnermannAbstract:In recent years, femtosecond (fs)-Lasers have evolved into a versatile tool for high precision micromachining of transparent Materials because nonlinear absorption in the focus can result in refractive index modifications or Material disruptions. However, when high pulse energies or low numerical apertures are required, nonlinear side effects such as self-focusing, filamentation or white light generation can decrease the modification quality. In this paper, we apply simultaneous spatial and temporal focusing (SSTF) to overcome these limitations. The main advantage of SSTF is that the ultrashort pulse is only formed at the focal plane, thereby confining the intensity distribution strongly to the focal volume and suppressing detrimental nonlinear side effects. Thus, we investigate the optical breakdown within a water cell by pump-probe shadowgraphy, comparing conventional focusing and SSTF under equivalent focusing conditions. The plasma formation is well confined for low pulse energies <2 µJ, but higher pulse energies lead to the filamentation and break-up of the disruptions for conventional focusing, thereby decreasing the modification quality. In contrast, plasma induced by SSTF stays well confined to the focal plane, even for high pulse energies up to 8 µJ, preventing extended filaments, side branches or break-up of the disruptions. Furthermore, while conventional focusing leads to broadband supercontinuum generation, only marginal spectral broadening is observed using SSTF. These experimental findings are in excellent agreement with numerical simulations of the nonlinear pulse propagation and interaction processes. Therefore, SSTF appears to be a powerful tool to control the Processing of transparent Materials, e.g., for precise ophthalmic fs-surgery.
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femtosecond vs picosecond Laser Material Processing
Laser Technik Journal, 2010Co-Authors: Andreas Tuennermann, Stefan Nolte, Jens LimpertAbstract:Laser Materials Processing has been an intensive research topic since the invention of the Laser. nowadays, Lasers are used as efficient and qualified tools in many industrial processes, like heavy industrial cutting, hardening, and welding. however, as the miniaturization of components and devices is progressing, finer structures are required. here, the flexible Laser Processing with conventional Laser sources is typically limited by thermal or mechanical damage (melting, formation of burr and cracks, changes in the morphology etc.), which is especially true if metals have to be processed. In order to overcome these limitations and to minimize collateral damage various research activities based on the use of ultrashort Laser pulses with picosecond or femtosecond duration have been started in the early 1990s (e.g. [1–8]).
Peter G. Kazansky - One of the best experts on this subject based on the ideXlab platform.
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Harnessing non-reciprocity and polarization spatio-temporal couplings in ultrafast Laser Material Processing
Nonlinear Optics, 2017Co-Authors: Peter G. Kazansky, Aabid Patel, Ausra Cerkauskaite, Rokas Drevinskas, Yuri Svirko, Vladmir T. Tikhonchuk, Charles G. DurfeeAbstract:The puzzles of non-reciprocity and anisotropic photosensitivity in ultrafast Laser Material Processing are revealed. Non-paraxial polarization spatio-temporal coupling is demonstrated as a new degree of freedom in light-matter interaction.
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Dataset for Non-Paraxial Polarization Spatio-Temporal Coupling in Ultrafast Laser Material Processing
2017Co-Authors: Aabid Patel, Peter G. KazanskyAbstract:Dataset supporting the article Non-Paraxial Polarization Spatio-Temporal Coupling in Ultrafast Laser Material Processing by Aabid Patel, Vladmir T. Tikhonchuk, Jingyu Zhang, and Peter G. Kazansky in Laser and Photonics Review
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Harnessing polarization spatio-temporal coupling: A new degree of freedom in ultrafast Laser Material Processing
2015 Conference on Lasers and Electro-Optics (CLEO), 2015Co-Authors: Aabid Patel, Martynas Beresna, Peter G. KazanskyAbstract:Polarization spatio-temporal coupling reveals new degree of freedom in ultrafast Laser Material Processing. Control of modification in fused silica is demonstrated with the use of prism compressors and polarization azimuth of ultrashort pulse Laser beam.
Jyoti Mazumder - One of the best experts on this subject based on the ideXlab platform.
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ranked feature based Laser Material Processing monitoring and defect diagnosis using k nn and svm
Journal of Manufacturing Processes, 2020Co-Authors: Jyoti Mazumder, Jaewoong ParkAbstract:Abstract In this study, an in-situ monitoring system was developed using a spectrometer for Laser welding on galvanized steel. The spectrometer monitored the emission spectra generated from Laser-induced plasma for the purpose of classifying welding defects because the plasma generated during the Laser welding process contains a considerable amount of information about the on-going process. Temporal features extracted from the emission spectra were used for in-situ monitoring. In order to extract the best features, Fisher’s criterion was adopted to rank and select the features. The monitoring performance of a photodiode and spectrometer were compared by using the selected features. The emission spectrum proved to be a better feature than the photodiode signal. Additionally, the emission spectrum was combined with statistical properties such as mean, root mean square, standard deviation, peak, skewness, and kurtosis to increase the classification rate. The ranking of the emission spectra depended on the statistical features. The k-nearest neighbors (k-NN) algorithm and support vector machine (SVM) algorithm were used as classifiers of the ranked features. Three groups, which are sound welding, underfill defect and bead separation defect, were successfully classified for quality assurance.
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role of zinc coating at liquid vapor interface during Laser Material Processing of zinc coated steel
Journal of Applied Physics, 2013Co-Authors: Jyoti MazumderAbstract:In Laser Material Processing, one of the major interests is characterizing interfacial phenomena induced by thermal phase changes of Materials. The interfacial characteristics in the Laser Processing of multi-coated Materials show different behaviors compared to those of single Material Processing. The difference in thermo-physical properties of the coated and primary Materials induces the contrasting characteristics of multiple interfacial phenomena including temperature, recoil pressure, capillary force, and thermo capillary force. The influence of coating layer to the interfacial physics evolutions is difficult to be modeled mathematically when the Laser beam penetrates the multi-coated Material layer by layer. This paper addresses the role of the zinc coating at the liquid-vapor interface during the Laser Processing of zinc coated steel, as a representative case of multi-coated Materials. Computational modules incorporating the zinc layers were established and selectively applied at the locations wher...
Yuri Svirko - One of the best experts on this subject based on the ideXlab platform.
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Harnessing non-reciprocity and polarization spatio-temporal couplings in ultrafast Laser Material Processing
Nonlinear Optics, 2017Co-Authors: Peter G. Kazansky, Aabid Patel, Ausra Cerkauskaite, Rokas Drevinskas, Yuri Svirko, Vladmir T. Tikhonchuk, Charles G. DurfeeAbstract:The puzzles of non-reciprocity and anisotropic photosensitivity in ultrafast Laser Material Processing are revealed. Non-paraxial polarization spatio-temporal coupling is demonstrated as a new degree of freedom in light-matter interaction.
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Laser Material Processing with tightly focused cylindrical vector beams
Applied Physics Letters, 2016Co-Authors: Rokas Drevinskas, Yuri Svirko, Martynas Beresna, Jingyu Zhang, Mindaugas Gecevicius, A G Kazanskii, P. G. KazanskyAbstract:We demonstrate a comprehensive modification study of silica glass, crystalline silicon, and amorphous silicon film, irradiated by tightly focused cylindrical vector beams with azimuthal and radial polarizations. The evidence of the longitudinal field associated with radial polarization is revealed by second harmonic generation in z-cut lithium niobate crystal. Despite the lower threshold of ring-shaped modification of silicon Materials, the modification in the center of single pulse radially polarized beam is not observed. The phenomenon is interpreted in terms of the enhanced reflection of longitudinal component at the interface with high-index contrast, demonstrating that the longitudinal component is inefficient for the flat surface modification. Enhanced interaction of the longitudinal light field with silicon nanopillar structures produced by the first pulse of double-pulse irradiation is also demonstrated.
Rokas Drevinskas - One of the best experts on this subject based on the ideXlab platform.
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Harnessing non-reciprocity and polarization spatio-temporal couplings in ultrafast Laser Material Processing
Nonlinear Optics, 2017Co-Authors: Peter G. Kazansky, Aabid Patel, Ausra Cerkauskaite, Rokas Drevinskas, Yuri Svirko, Vladmir T. Tikhonchuk, Charles G. DurfeeAbstract:The puzzles of non-reciprocity and anisotropic photosensitivity in ultrafast Laser Material Processing are revealed. Non-paraxial polarization spatio-temporal coupling is demonstrated as a new degree of freedom in light-matter interaction.
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Laser Material Processing with tightly focused cylindrical vector beams
Applied Physics Letters, 2016Co-Authors: Rokas Drevinskas, Yuri Svirko, Martynas Beresna, Jingyu Zhang, Mindaugas Gecevicius, A G Kazanskii, P. G. KazanskyAbstract:We demonstrate a comprehensive modification study of silica glass, crystalline silicon, and amorphous silicon film, irradiated by tightly focused cylindrical vector beams with azimuthal and radial polarizations. The evidence of the longitudinal field associated with radial polarization is revealed by second harmonic generation in z-cut lithium niobate crystal. Despite the lower threshold of ring-shaped modification of silicon Materials, the modification in the center of single pulse radially polarized beam is not observed. The phenomenon is interpreted in terms of the enhanced reflection of longitudinal component at the interface with high-index contrast, demonstrating that the longitudinal component is inefficient for the flat surface modification. Enhanced interaction of the longitudinal light field with silicon nanopillar structures produced by the first pulse of double-pulse irradiation is also demonstrated.
