Glass welding by ultra-short pulsed(USP)lasers is a piece of technology that offers high strength joints with hermetic sealing.The joints are typically formed in glass that is transparent to the laser by exploiting no...Glass welding by ultra-short pulsed(USP)lasers is a piece of technology that offers high strength joints with hermetic sealing.The joints are typically formed in glass that is transparent to the laser by exploiting nonlinear absorption effects that occur under extreme conditions.Though the temperature reached during the process is on the order of a few 1000°C,the heat affected zone(HAZ)is confined to only tens of micrometers.It is this controlled confinement of the HAZ during the joining process that makes this technology so appealing to a multitude of applications because it allows the foregoing of a subsequent tempering step that is typically essential in other glass joining techniques,thus making it possible to effectively join highly heat sensitive components.In this work,we give an overview on the process,development and applications of glass welding by USP lasers.展开更多
Within this work,we present a system for the measurement of the three-dimensional(3D)trajectories of spatters and entrained particles during laser powder bed fusion(L-PBF)of metals.It is comprised of two ultrahigh-spe...Within this work,we present a system for the measurement of the three-dimensional(3D)trajectories of spatters and entrained particles during laser powder bed fusion(L-PBF)of metals.It is comprised of two ultrahigh-speed cameras and a reconstruction task specific processing reconstruction algorithm.The system enables an automated determination of 3D measures from the trajectories of a large number of tracked particles.Ambiguity evolving from an underdetermined geometrical situation induced by a two-camera setup is resolved within the tracking using a priori knowledge of L-PBF of metals.All processing steps were optimized to run on a graphics processing unit to allow the processing of large amounts of data within an appropriate time frame.The overall approach was validated by a comparison of the measurement results to synthetic images with a known 3D ground truth.展开更多
Background: Since 2004, zebrafish have become the state-of-the-art, in vivo model for biomedical research due to their genetic and physiological homology with humans, inexpensive high-quantity breeding, and quick deve...Background: Since 2004, zebrafish have become the state-of-the-art, in vivo model for biomedical research due to their genetic and physiological homology with humans, inexpensive high-quantity breeding, and quick development in a highly-controlled environment suitable for longitudinal studies. New Method: To fully utilize the zebrafish model, a novel, automated, high-throughput system was designed. Shoals of five zebrafish were placed in 16 tanks and automatically fed over two days for a total of 16 training sessions. Color LED lights were used as the stimulus for each shoal coinciding with the release of food for a duration of 20 seconds. This system was tested on two age groups: 6- and 11-month-old. Results: After three training sessions, the median height of the school in the tank during stimulus was significantly higher than that of the naïve fish during the first training session. All subsequent training sessions demonstrated similar behaviour. A decline in memory retention, as defined by a reduction in the median height during light stimulus (i.e. no simultaneous food delivery), was observed 8 days post training. Comparison with existing methods: The high-throughput nature of this system allows for simultaneous training of 16 tanks of fish under identical conditions without human interaction and provides a means to rapidly assess their learning and memory behaviours. Conclusion: Results provide a baseline for understanding the normal cognitive processes of learning and memory retention in zebrafish. This work paves the way for future studies on the impacts of therapeutic agents on these cognitive processes.展开更多
This paper focuses on the preparation of a new extended set of calibrations of cooling rate(fictive temperature)in fused silica determined by inelastic light scattering and its subsequent use to characterize the local...This paper focuses on the preparation of a new extended set of calibrations of cooling rate(fictive temperature)in fused silica determined by inelastic light scattering and its subsequent use to characterize the local cooling rate distribution in ultra-short pulsed(USP)laser modification.In order to determine the thermal history(e.g.cooling rate and fictive temperature)of fused silica,high-resolution inelastic light-scattering experiments(Raman and Brillouin spectroscopy)were investigated.Calibrations were performed and compared to the existing literature to quantify structural changes due to a change of fictive temperature.Compared to existing calibrations,this paper provides an extension to lower and higher cooling rates.Using this new set of calibrations,we characterized a USP laser modification in fused silica and calculated the local fictive temperature distribution.An equation relating the fictive temperature(Tf)to cooling rates is given.A maximum cooling rate of 3000 K min-1 in the glass transition region around 1200℃ was deduced from the Raman analysis.The Brillouin observations are sensitive to both the thermal history and the residual stress.By comparing the Raman and Brillouin observations,we extracted the local residual stress distribution with high spatial resolution.For the first time,combined Raman and Brillouin inelastic light scattering experiments show the local distribution of cooling rates and residual stresses(detailed behavior of the glass structure)in the interior and the surrounding of an USP laser modified zone.展开更多
Light plays a central role in many applications.The key to unlocking its versatility lies in shaping it into the most appropriate form for the task at hand.Specifically tailored refractive index modifications,directly...Light plays a central role in many applications.The key to unlocking its versatility lies in shaping it into the most appropriate form for the task at hand.Specifically tailored refractive index modifications,directly manufactured inside glass using a short pulsed laser,enable an almost arbitrary control of the light flow.However,the stringent requirements for quantitative knowledge of these modifications,as well as for fabrication precision,have so far prevented the fabrication of light-efficient aperiodic photonic volume elements(APVEs).Here,we present a powerful approach to the design and manufacturing of light-efficient APVEs.We optimize application-specific three-dimensional arrangements of hundreds of thousands of microscopic voxels and manufacture them using femtosecond direct laser writing inside millimeter-sized glass volumes.We experimentally achieve unprecedented diffraction efficiencies up to 80%,which is enabled by precise voxel characterization and adaptive optics during fabrication.We demonstrate APVEs with various functionalities,including a spatial mode converter and combined intensity shaping and wavelength multiplexing.Our elements can be freely designed and are efficient,compact,and robust.Our approach is not limited to borosilicate glass but is potentially extendable to other substrates,including birefringent and nonlinear materials,giving a preview of even broader functionalities,including polarization modulation and dynamic elements.展开更多
The spectral dispersion of ultrashort pulses allows the simultaneous focusing of light in both space and time,which creates socalled spatiotemporal foci.Such space–time coupling may be combined with the existing holo...The spectral dispersion of ultrashort pulses allows the simultaneous focusing of light in both space and time,which creates socalled spatiotemporal foci.Such space–time coupling may be combined with the existing holographic techniques to give a further dimension of control when generating focal light fields.In the present study,it is shown that a phase-only hologram placed in the pupil plane of an objective and illuminated by a spatially chirped ultrashort pulse can be used to generate threedimensional arrays of spatio-temporally focused spots.By exploiting the pulse front tilt generated at focus when applying simultaneous spatial and temporal focusing(SSTF),it is possible to overlap neighboring foci in time to create a smooth intensity distribution.The resulting light field displays a high level of axial confinement,with experimental demonstrations given through two-photon microscopy and the non-linear laser fabrication of glass.展开更多
This article presents and analyses the modular architecture and capabilities of CODE-DE(Copernicus Data and Exploitation Platform–Deutschland,www.code-de.org),the integrated German operational environment for accessi...This article presents and analyses the modular architecture and capabilities of CODE-DE(Copernicus Data and Exploitation Platform–Deutschland,www.code-de.org),the integrated German operational environment for accessing and processing Copernicus data and products,as well as the methodology to establish and operate the system.Since March 2017,CODE-DE has been online with access to Sentinel-1 and Sentinel-2 data,to Sentinel-3 data shortly after this time,and since March 2019 with access to Sentinel-5P data.These products are available and accessed by 1,682 registered users as of March 2019.During this period 654,895 products were downloaded and a global catalogue was continuously updated,featuring a data volume of 814 TByte based on a rolling archive concept supported by a reload mechanism from a long-term archive.Since November 2017,the element for big data processing has been operational,where registered users can process and analyse data themselves specifically assisted by methods for value-added product generation.Utilizing 195,467 core and 696,406 memory hours,982,948 products of different applications were fully automatically generated in the cloud environment and made available as of March 2019.Special features include an improved visualization of available Sentinel-2 products,which are presented within the catalogue client at full 10 m resolution.展开更多
基金The authors gratefully acknowledge support by the Graduate School in Advanced Optical Technologies(SAOT)of the Friedrich–Alexander-University of Erlangen–Nürnberg,and the Bayerisches Laserzentrum GmbH.
文摘Glass welding by ultra-short pulsed(USP)lasers is a piece of technology that offers high strength joints with hermetic sealing.The joints are typically formed in glass that is transparent to the laser by exploiting nonlinear absorption effects that occur under extreme conditions.Though the temperature reached during the process is on the order of a few 1000°C,the heat affected zone(HAZ)is confined to only tens of micrometers.It is this controlled confinement of the HAZ during the joining process that makes this technology so appealing to a multitude of applications because it allows the foregoing of a subsequent tempering step that is typically essential in other glass joining techniques,thus making it possible to effectively join highly heat sensitive components.In this work,we give an overview on the process,development and applications of glass welding by USP lasers.
基金The authors gratefully acknowledge funding by the Erlangen Graduate School in Advanced Optical Technologies(SAOT)and by the German Research Foundation(DFG)in the framework of a German excellence initiative.We also thankfully acknowledge the GPU seeding grant for researchers by Nvidia Corp.
文摘Within this work,we present a system for the measurement of the three-dimensional(3D)trajectories of spatters and entrained particles during laser powder bed fusion(L-PBF)of metals.It is comprised of two ultrahigh-speed cameras and a reconstruction task specific processing reconstruction algorithm.The system enables an automated determination of 3D measures from the trajectories of a large number of tracked particles.Ambiguity evolving from an underdetermined geometrical situation induced by a two-camera setup is resolved within the tracking using a priori knowledge of L-PBF of metals.All processing steps were optimized to run on a graphics processing unit to allow the processing of large amounts of data within an appropriate time frame.The overall approach was validated by a comparison of the measurement results to synthetic images with a known 3D ground truth.
文摘Background: Since 2004, zebrafish have become the state-of-the-art, in vivo model for biomedical research due to their genetic and physiological homology with humans, inexpensive high-quantity breeding, and quick development in a highly-controlled environment suitable for longitudinal studies. New Method: To fully utilize the zebrafish model, a novel, automated, high-throughput system was designed. Shoals of five zebrafish were placed in 16 tanks and automatically fed over two days for a total of 16 training sessions. Color LED lights were used as the stimulus for each shoal coinciding with the release of food for a duration of 20 seconds. This system was tested on two age groups: 6- and 11-month-old. Results: After three training sessions, the median height of the school in the tank during stimulus was significantly higher than that of the naïve fish during the first training session. All subsequent training sessions demonstrated similar behaviour. A decline in memory retention, as defined by a reduction in the median height during light stimulus (i.e. no simultaneous food delivery), was observed 8 days post training. Comparison with existing methods: The high-throughput nature of this system allows for simultaneous training of 16 tanks of fish under identical conditions without human interaction and provides a means to rapidly assess their learning and memory behaviours. Conclusion: Results provide a baseline for understanding the normal cognitive processes of learning and memory retention in zebrafish. This work paves the way for future studies on the impacts of therapeutic agents on these cognitive processes.
基金The authors gratefully acknowledge support by the Deutsche Forschungsgemeinschaft through the Grant Nos.Ho1691/8-1 I Li2713/4-1 | Schm2115/62-1,the Graduate School in Advanced Optical Technologies(SAOT)of the Friedrich-Alexander-Universitat Erlangen-Nurnberg and the QSIL GmbH Quarzschmelze Ilmenau.
文摘This paper focuses on the preparation of a new extended set of calibrations of cooling rate(fictive temperature)in fused silica determined by inelastic light scattering and its subsequent use to characterize the local cooling rate distribution in ultra-short pulsed(USP)laser modification.In order to determine the thermal history(e.g.cooling rate and fictive temperature)of fused silica,high-resolution inelastic light-scattering experiments(Raman and Brillouin spectroscopy)were investigated.Calibrations were performed and compared to the existing literature to quantify structural changes due to a change of fictive temperature.Compared to existing calibrations,this paper provides an extension to lower and higher cooling rates.Using this new set of calibrations,we characterized a USP laser modification in fused silica and calculated the local fictive temperature distribution.An equation relating the fictive temperature(Tf)to cooling rates is given.A maximum cooling rate of 3000 K min-1 in the glass transition region around 1200℃ was deduced from the Raman analysis.The Brillouin observations are sensitive to both the thermal history and the residual stress.By comparing the Raman and Brillouin observations,we extracted the local residual stress distribution with high spatial resolution.For the first time,combined Raman and Brillouin inelastic light scattering experiments show the local distribution of cooling rates and residual stresses(detailed behavior of the glass structure)in the interior and the surrounding of an USP laser modified zone.
基金supported by the Austrian Science Fund(FWF),grant no.I3984-N36the Engineering and Physical Sciences Research Council(EPSRC),grant no.R004803/01the German Research Foundation(DFG),grant no.409765270。
文摘Light plays a central role in many applications.The key to unlocking its versatility lies in shaping it into the most appropriate form for the task at hand.Specifically tailored refractive index modifications,directly manufactured inside glass using a short pulsed laser,enable an almost arbitrary control of the light flow.However,the stringent requirements for quantitative knowledge of these modifications,as well as for fabrication precision,have so far prevented the fabrication of light-efficient aperiodic photonic volume elements(APVEs).Here,we present a powerful approach to the design and manufacturing of light-efficient APVEs.We optimize application-specific three-dimensional arrangements of hundreds of thousands of microscopic voxels and manufacture them using femtosecond direct laser writing inside millimeter-sized glass volumes.We experimentally achieve unprecedented diffraction efficiencies up to 80%,which is enabled by precise voxel characterization and adaptive optics during fabrication.We demonstrate APVEs with various functionalities,including a spatial mode converter and combined intensity shaping and wavelength multiplexing.Our elements can be freely designed and are efficient,compact,and robust.Our approach is not limited to borosilicate glass but is potentially extendable to other substrates,including birefringent and nonlinear materials,giving a preview of even broader functionalities,including polarization modulation and dynamic elements.
基金supported through funding from the Erlangen Graduate School in Advanced Optical Technologies(SAOT)by the German Research Foundation(DFG)in the framework of the German excellence initiative,the Leverhulme Trust(RPG-2013-044)the European Research Council(ERC)under the Horizon 2020 research and innovation programme(grant agreement no.695140).
文摘The spectral dispersion of ultrashort pulses allows the simultaneous focusing of light in both space and time,which creates socalled spatiotemporal foci.Such space–time coupling may be combined with the existing holographic techniques to give a further dimension of control when generating focal light fields.In the present study,it is shown that a phase-only hologram placed in the pupil plane of an objective and illuminated by a spatially chirped ultrashort pulse can be used to generate threedimensional arrays of spatio-temporally focused spots.By exploiting the pulse front tilt generated at focus when applying simultaneous spatial and temporal focusing(SSTF),it is possible to overlap neighboring foci in time to create a smooth intensity distribution.The resulting light field displays a high level of axial confinement,with experimental demonstrations given through two-photon microscopy and the non-linear laser fabrication of glass.
基金funding from the German Federal Ministry of Transport and Digital Infrastructure(BMVI).
文摘This article presents and analyses the modular architecture and capabilities of CODE-DE(Copernicus Data and Exploitation Platform–Deutschland,www.code-de.org),the integrated German operational environment for accessing and processing Copernicus data and products,as well as the methodology to establish and operate the system.Since March 2017,CODE-DE has been online with access to Sentinel-1 and Sentinel-2 data,to Sentinel-3 data shortly after this time,and since March 2019 with access to Sentinel-5P data.These products are available and accessed by 1,682 registered users as of March 2019.During this period 654,895 products were downloaded and a global catalogue was continuously updated,featuring a data volume of 814 TByte based on a rolling archive concept supported by a reload mechanism from a long-term archive.Since November 2017,the element for big data processing has been operational,where registered users can process and analyse data themselves specifically assisted by methods for value-added product generation.Utilizing 195,467 core and 696,406 memory hours,982,948 products of different applications were fully automatically generated in the cloud environment and made available as of March 2019.Special features include an improved visualization of available Sentinel-2 products,which are presented within the catalogue client at full 10 m resolution.
