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This PDF file contains the front matter associated with SPIE Proceedings Volume 8611, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.
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Micro and Nano Manipulation of Cells, Optical Transfection
Femtosecond photoporation is an optical, non-invasive method of injecting membrane impermeable substances
contained within the surrounding medium into cells. The technique typically addresses individual cells in a static
monolayer. While this gives excellent selectivity, it can be time consuming or impractical to treat larger samples. We
build on previous work using a microfluidic platform, which allows for a suspension of cells to be dosed with
femtosecond light as they flow through a microfluidic channel. A reusuable quartz chip is designed with an 's'-bend with facilitates the delivery of a 'non-diffracting' femtosecond Bessel beam along the centre of the channel. By implementing off-chip hydrodynamic focusing, cells are confined to the central region of the channel and pass along the Bessel beam core where they are photoporated. This new parallel approach allows for higher flow rates to be used compared to the previous, orthogonal, design whilst maintaining the necessary dwell time in the Bessel beam core. Optical injection of the cell membrane impermeable stain propidium iodide has been successful with two cell lines. These have yielded viable injection efficiencies of 31.0±9.5% Chinese hamster ovary cells (CHO-K1) and 20.4±4.2% human promyelocytic cells (HL60) with a cell throughput of up to 10 cells/second. This marks an order of magnitude increase compared to the previous microfluidic design.
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We demonstrate the use of femtosecond optical transfection for the genetic manipulation of human embryonic stem
cells. Using a system with an SLM combined with a scanning mirror allows poration of both single-cell and colony-formed human embryonic stem cells in a rapid and targeted manner. In this work, we show successful transfection
of plasmid DNA tagged with fluorescent reporters into human embryonic stem cells using three doses of focused
femtosecond laser. A significant number of transfected cells retained their undifferentiated morphological feature of
large nucleus with high nucleus to cytoplasmic ratio, 48h after photoporation. Furthermore, DNA constructs driven
by different types of promoters were also successfully transfected into human embryonic stem cells using this technique.
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Tissue and Surgical Applications of Ultrashort Pulse Lasers
Femtosecond lasers are a versatile tool to process transparent materials like glasses, polymers or ophthalmic tissue.
However, when focusing pulses of several μJ into the material, the high intensity near the laser focus leads to undesired nonlinear side effects like self-focusing and filamentation, resulting in an increased length of the induced plasma or the fragmentation of the breakdown volume. To overcome this limitation, we studied the influence of simultaneous spatial and temporal focusing (SSTF) on the laser induced optical breakdown (LIOB) in water. For this purpose, the incoming laser pulse is spectrally separated by a grating stretcher setup and recompressed by the focusing optics. Due to the increased pulse duration outside of the laser focus, the nonlinear laser-material interaction is confined to the focal region. We investigated the formation of the plasma and the resulting disruption in water by shadow imaging. With conventional focusing (τ = 70 fs, NA = 0.1) self-focusing, filamentation and breakup of the disruption volume was observed for pulse energies > 2 μJ, leading to a breakdown length of ~ 800 μm at a pulse energy of 8 μJ. With SSTF the axial length of the breakdown is significantly reduced by a factor of ~ 2. Plasma formation and the resulting disruption stay within the focal region. No self-focusing could be observed for pulse energies up to 8 μJ. Therefore, SSTF appears to be a promising tool to induce photodisruptions in transparent materials even with low numerical aperture, e.g. for precise fs-laser surgery within the posterior segment of the eye.
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In this contribution we present the motivations underlying the introduction of harmonic nanoparticles, i.e. second harmonic contrast agents for nonlinear microscopy. Their properties will be discussed in the light of various biological applications including imaging of stem cells and rare event detection in physiological media.
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The fast development of laser techniques, in particular, the generation of ultrashort femtosecond and even attosecond
pulses opens new frontiers and various experimental tools for biomedical applications. The combination of pulse
shaping and optimal control is a very promising tool based on coherent manipulation of wavepackets on an ultrafast time scale. It already has successfully been applied for optimal dynamic discrimination (ODD) experiments of biomolecules like free amino acids and flavins which are indistinguishable by spectroscopic means. This approach can be extended toward to label free cellular imaging and detection of chemical or biological substances.
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We present evidence of random lasing from the fluorescent protein DsRed2. Lasing is achieved using a random 1D cavity in the simplest possible multiple scattering geometry, in which a solution containing purified DsRed2 protein placed in a layered random medium is optically excited in the direction perpendicular to the plane of random layers. Lasing was observed with both nanosecond and femtosecond pump pulses. Pumping with ultrashort pulses resulted in a lasing threshold three orders of magnitude lower than that found for nanosecond pumping.
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Ultrashort pulse lasers with pulse duration on the level of 100 fs can be used for à variety of interesting applications that rely on multiphoton processes or ultrafast dynamics. Up to now, this field was reserved to Ti:sapphire-based laser systems that exhibit a quite complex laser architecture and relatively low laser efficiency. This may be an important reason why such applications could not yet penetrate into large scale industrial applications. We have realized an Yb-doped tungstate-based regenerative amplifier in innovative amplifier architecture. We succeeded to produce 106-fs-pulses at 70μJ and 140 fs at 40 μJ pulse energy, respectively. The average power is on the level of several Watts. The optimized management and exploitation of dispersive and nonlinear effects during the amplification process inside the regenerative amplifier cavity enabled the generation of such short pulses with excellent temporal quality and in an extremely simple and robust laser architecture that is well suited for industrial environments. Applying the same amplifier architecture to an Yb:YAG thin disk regenerative amplifier enabled the generation of pulses as short as 360-fs at high pulse energies exceeding 200 μJ and high average powers of more than 30 W.
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Broadband light sources provide a significant benefit for optical coherence tomography (OCT) imaging
concerning the axial resolution. Light sources with bandwidths over 200 nm result in an axial resolution up to 2
microns. Such broad band OCT imaging can be achieved utilizing super continuum (SC) light sources. The main
important disadvantage of commercial SC light sources is the overall size and the high costs. Therefore, the use
of SC light sources in small OCT setups and applications is limited. We present a new small housing and costeffective
light source, which is suitable for OCT imaging. The used light source has dimensions of 110 x 160 x
60 mm and covers a wavelength range from 390 nm up to 2500 nm.
The light source was coupled in a dual band OCT system. The light is guided into the interferometer and split in
reference and sample beam. The superimposed signal is guided to the spectrometer unit, which consists of two
spectrometers. This spectrometer system separates the light. One band centered at 800 nm with a full bandwidth
of 176 nm and a second band centered at 1250 nm with a full spectral width of 300 nm was extracted. The 800
nm interference signal is detected by a silicon line scan camera and the 1250 nm signal by an indium gallium
arsenide linear image sensor.
In this test measurement a plastic foil was used as a sample, which is composed of several plastic film layers.
Three dimensional images were acquired simultaneous with the dual band OCT setup. The images were acquired
at an A-scan rate of 1 kHz. The 1 kHz A-line rate was chosen because so far the optical power of the light source
is not optimal for high speed OCT imaging. The source provides 2 mW in the range of 390 nm to 800 nm and 25
mW in the range from 390 nm to 1650 nm. Furthermore, we coupled the light source by a 50:50 optical fiber
coupler, which also reduces the overall optical power of the light source within the OCT setup.
Nevertheless, we demonstrated that this new small-package and cost-effective light source is very suitable to
carry out OCT imaging. The use of this light source can open up new OCT applications, which require OCT
setups with very high axial resolution and small footprint.
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The most established technique for the identification at biometric access control systems is the human fingerprint. While every human fingerprint is unique, fingerprints can be faked very easily by using thin layer fakes. Because commercial fingerprint scanners use only a two-dimensional image acquisition of the finger surface, they can only hardly differentiate between real fingerprints and fingerprint fakes applied on thin layer materials. A Swept Source OCT system with an A-line rate of 20 kHz and a lateral and axial resolution of approximately 13 μm, a centre wavelength of 1320 nm and a band width of 120 nm (FWHM) was used to acquire fingerprints and finger tips with overlying fakes. Three-dimensional volume stacks with dimensions of 4.5 mm x 4 mm x 2 mm were acquired. The layering arrangement of the imaged finger tips and faked finger tips was analyzed and subsequently classified into real and faked fingerprints. Additionally, sweat gland ducts were detected and consulted for the classification. The manual classification between real fingerprints and faked fingerprints results in almost 100 % correctness. The outer as well as the internal fingerprint can be recognized in all real human fingers, whereby this was not possible in the image stacks of the faked fingerprints. Furthermore, in all image stacks of real human fingers the sweat gland ducts were detected. The number of sweat gland ducts differs between the test persons. The typical helix shape of the ducts was observed. In contrast, in images of faked fingerprints we observe abnormal layer arrangements and no sweat gland ducts connecting the papillae of the outer fingerprint and the internal fingerprint. We demonstrated that OCT is a very useful tool to enhance the performance of biometric control systems concerning attacks by thin layer fingerprint fakes.
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Laser scanners are essential for scientific research, manufacturing, defense, and medical practice. Unfortunately, often times the speed of conventional laser scanners (e.g., galvanometric mirrors and acousto-optic deflectors) falls short for many applications, resulting in motion blur and failure to capture fast transient information. Here, we present a novel type of laser scanner that offers roughly three orders of magnitude higher scan rates than conventional methods. Our laser scanner, which we refer to as the hybrid dispersion laser scanner, performs inertia-free laser scanning by dispersing a train of broadband pulses both temporally and spatially. More specifically, each broadband pulse is temporally processed by time stretch dispersive Fourier transform and further dispersed into space by one or more diffractive elements such as prisms and gratings. As a proof-of-principle demonstration, we perform 1D line scans at a record high scan rate of 91 MHz and 2D raster scans and 3D volumetric scans at an unprecedented scan rate of 105 kHz. The method holds promise for a broad range of scientific, industrial, and biomedical applications. To show the utility of our method, we demonstrate imaging, nanometer-resolved surface vibrometry, and high-precision flow cytometry with real-time throughput that conventional laser scanners cannot offer due to their low scan rates.
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We demonstrate the use of Double-Blind Frequency-Resolved Optical Gating implemented in Polarization-Gate geometry to measure two pulses at very different center wavelength (400nm and 800nm) simultaneously on a single-shot. Complex pulse pair with Time-Bandwidth-Product of 1.1 and 6.2 are measured and retrieved.
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Frequency Resolved Optical Gating (FROG) uses the ultrafast laser pulse to interrogate itself for full characterization;
that is, no reference pulse is used to obtain the full intensity and phase of the input ultrafast laser pulse. Crosscorrelation FROG (X-FROG) cross-correlates a known ultrafast laser pulse with an unknown ultrafast laser pulse to characterize the unknown pulse allowing wider wavelength ranges of ultrafast laser pulses as well as more complex
ultrafast laser pulses to be characterized. We present a new X-FROG algorithm, based on the principal components
generalized projections (PCGP) algorithm that is fast, robust, and simple.
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We study multi-shot intensity-and-phase measurements of unstable trains of ultrashort pulses using spectral-phase interferometry for direct electric-field reconstruction (SPIDER), second harmonic generation (SHG) frequency-resolved optical gating (FROG), polarization gate (PG) FROG, and cross-correlation FROG (XFROG). An analytical calculation suggests that SPIDER cannot indicate instability in pulse trains well. Simulations confirm this and demonstrate that SPIDER only measures the coherent artifact. Further, the presence of instability cannot be distinguised from benign misalignment effects in SPIDER. FROG methods suggest instability by exhibiting clear disagreement between measured and retrieved traces.
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The temporal self-reconstruction of pulsed Bessel-like needle beams was studied. Arrays of nondiffracting sub-7-fs
needle beams were shaped from Ti:sapphire oscillator pulses by programming multiple axicons in a phase-only spatial
light modulator. Defined distortions in the time domain were induced by local spectral filtering. By differently shading
parts of selected sub-beams, the self-reconstruction was analyzed under variable conditions. Pulse duration maps were measured with two-dimensional second order autocorrelation based on the Shack-Hartmann sensor principle of
wavefront division. Completely distorted pulses were found to have a pulse duration of > 13 fs whereas partially
distorted sub-beams returned to pulse durations close to the initial ones. Specific applications are proposed.
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The development of an Yb-doped distributed Bragg reflector (DBR) waveguide laser fabricated in phosphate glass using the femtosecond laser direct-write technique is reported. The laser has the slope efficiency of 31% with the output power up to 81 mW at a pump power level of 378 mW. A theoretical model for the waveguide laser (WGL) is presented which gives emphasis to transverse integrals to investigate the energy distribution in a homogenously doped glass which is opposed to the fiber laser. The model was validated with experiments comparing a DBR WGL, and then used to study the influence of distributed rare earth dopants on the performance of such lasers. Approximately 15% of the pump power was absorbed by the doped “cladding” in the femtosecond laser inscribed Yb doped WGL case.
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Sub-wavelength structures are a crucial ingredient for modern optics. A class of ultrashort laser pulse induced, selforganized modifications in bulk transparent materials have attracted particular interest in recent years. Despite the multitude of potential applications of these so-called “nanogratings”, their underlying structure on the nanometer scale has been the subject of intensive debate throughout the decade since their discovery: Are they merely continuous modulation patterns of the material density, or do they consist of a substructure of hollow cavities? As nanogratings are embedded within the bulk material the conventional visualization technique relies on polishing and subsequent etching to excavate the modifications. However, such invasive sample preparation effectively erases sub-100 nm features. Moreover, they only provide access to two-dimensional cross sections. To overcome these limitations, we employed small angle X-ray scattering (SAXS), focused ion beam (FIB) milling and scanning electron microscopy (SEM) to reveal the underlying three-dimensional structure of nanogratings. Our results show that small cavities are the primary constituents of the nanogratings. These cavities grow predominantly during the first 100 laser pulses and reach a final size of about 30x200x300 nm3. Prolonged exposure to laser pulses increases the absolute number of cavities. Their threedimensional arrangement forms characteristic periodic planes of nanogratings.
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The “quill effect" describes a directional phenomenon encountered during ultrafast laser fabrication. Even in homogeneous and isotropic materials, fabrication effects can depend on the direction of focus translation. The directionality has been attributed to pulse front tilt, leading to a spatiotemporal asymmetry in the focus. We use adaptive optics to control pulse front tilt and demonstrate controllable quill effect writing in fused silica using a femtosecond laser. Through adaptive control of the intensity profile, we also confirm that inhomogeneous pupil illumination causes similar directional effects. We show dynamic control of ultrashort pulses and directional effects during fabrication.
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High average power, high repetition rate femtosecond lasers with μJ pulse energies are increasingly used for bio-medical and material processing applications. With the introduction of femtosecond laser systems such as the SpiritTM platform developed by High Q Lasers and Spectra-Physics, micro-processing of solid targets with femtosecond laser pulses have obtained new perspectives for industrial applications [1]. The unique advantage of material processing with subpicosecond lasers is efficient, fast and localized energy deposition, which leads to high ablation efficiency and accuracy in nearly all kinds of solid materials. The study on the impact of the laser processing parameters on the removal rate for transparent substrate using femtosecond laser pulses will be presented. In particular, examples of micro-processing of poly-L-lactic acid (PLLA) - bio-degradable polyester and XensationTM glass (Schott) machined with SpiritTM ultrafast laser will be shown.
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3D laser microfabrication inside narrow band gap solids like semiconductors will require the use of long wavelength
intense pulses. We perform an experimental study of the multiphoton-avalanche absorption yields and thresholds with tightly focused femtosecond laser beams at wavelengths: 1.3μm and 2.2μm. For comparisons, we perform the experiments in two very different materials: silicon (semiconductor, ∼1.1 eV indirect bandgap) and fused silica (dielectric, ∼9 eV direct bandgap). For both materials, we find only moderate differences while the number of photons required to cross the band gap changes from 2 to 3 in silicon and from 10 to 16 in fused silica.
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Ultrafast Laser Micromachining I: Fundamentals: Joint Session with Conferences 8607 and 8611
This paper reports the studies on time-resolved laser induced breakdown spectroscopy (LIBS) of plasmas produced by a
femtosecond (fs) fiber laser. The temporal behavior of specific ion and neutral emission lines of different materials
(metals, glasses and semiconductors) has been characterized. Sub-spot-size craters are generated with near threshold
pulse energy and it shows the potential for further improved spatial resolution using fs laser for LIBS application. The
decay between the continuum plasma emission and the atomic emission were used as a means to maximize the signal-tonoise
ratio (SNR) of the atomic emission lines for different materials. The SNR can be improved by more than one order
of magnitude with optimal delay and gating. This fiber laser based LIBS can lead to a more compact, reliable, low-cost
and field-deployable detection system for versatile and rapid analysis of chemical and special explosive materials.
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Ultrafast laser are well known to provide cold ablation on metals at near-threshold fluence and low repetition rate.
However increasing the repetition rate from multi-kHz to MHz may produce a heat accumulation in the target depending on both the scanning speed and the material properties. This potentially leads to two effects: enhanced ablation efficiency as well as increased heat affected zone. To identify potentials and limitations while maintaining highest processing quality is the main objective of this paper and a key issue for many industrial applications. We present some comprehensive results on the influence of both repetition rate and pulse duration on the ablation efficiency. This investigation is performed using a new generation of high power Ytterbium doped fiber ultrafast laser with a tunable pulse duration ranging from 350fs to 10ps and with repetition rate going from 250kHz to 2MHz. The output power is up to 40 watt. The effect of both parameters above on ablation efficiency of Al, Cu and Mo is discussed with respect to removal rate measurement and SEM analysis.
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Ultrafast Laser Micromachining II: Fundamentals: Joint Session with Conferences 8607 and 8611
Electron beam guns with approximately 10 kW power are used for drying printing colors. As exit window for the
electrons, 15 μm thin Titanium films are used, their thickness is at the current limit for industrial rolling processes.
Thinner exit windows would increase the electron’s transmission and therefore reduce the required acceleration voltage,
power consumption, shielding against X-rays and in the end machine and processing costs. The Titanium films should
locally be thinned to about 5 μm, in the ranges of 3 mm diameter.
Ultra-short laser pulses are well known for high precision micro structuring, as they offer small heat effect zones.
We optimized the processing parameters and the ultra-short laser ablation of thin Titanium foils to achieve high
manufacturing velocity and quality of the surface structure.
Experiments with single pulse laser ablation and different spot diameter were conducted to find a connection between
spot diameter and ablation threshold. The experiments show no dependency of the thresholds on the laser spot diameter..
First Experiments with different parameters were conducted to structure a three dimensional geometry in thin Titanium
foils.
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The transient behavior of the laser lift-off of thin molybdenum films, initiated by glass substrate side irradiation with a
660 fs laser pulse, is investigated in the picosecond range. For this purpose, a pump-probe microscopy setup is utilized to measure the transient relative reflectivity change in the center of the irradiated spot at the molybdenum/glass interface, which enables an interferometric observation of the shock wave propagation in the glass. In addition, a transient simulation of the electron and lattice temperature was performed. The results suggest that ultrafast heating initiates a shock wave in the molybdenum and the glass when the laser pulse has reached maximum intensity. At 10 ps, a confined phase explosion adds further momentum, and the Mo layer is caused to bulge.
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Ultrafast Laser Micromachining III: Joint Session with Conferences 8607 and 8611
We report on the welding of fused silica with bursts of ultrashort laser pulses. The bursts consist of ultrashort laser pulses with a repetition rate of 9.4 MHz. However, the time between the laser bursts is about 10 μs, which reduces the maximal temperature rise. Micrographs and simulations show that the molten structures are enlarged while using laser bursts. In addition, the usage of bursts instead of continuous pulse trains reduces the laser induced stress. By optimizing the burst frequency and repetition rate we were able to achieve a breaking resistance of up to 96% of the bulk material, which is significantly higher than in conventional high repetition rate laser bonding.
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Ultrafast Laser Micromachining IV: Joint Session with Conferences 8607 and 8611
We investigate the influence of the ambient pressure on the hole formation process during percussion drilling of silicon by applying an in-situ imaging technique. In this study the pressure is varied from atmospheric conditions down to medium vacuum of 10 !bar. Drilling was performed using an ultrashort pulse system providing 8 ps pulses with up to 125 μJ at 1030 nm. At this wavelength, the ablation behavior of silicon is comparable to metals. At the beginning of the drilling process, we observe an increased drilling efficiency by 40% already for a moderate pressure decrease to 100 mbar. The formation of an ideally shaped hole lasts for approximately 200 pulses instead of only 100 as for atmospheric conditions and therefore leads to 3 times the depth at this point. The effect can be enhanced by increasing the pulse energy, but not by decreasing pressure further. However, the number of pulses till the end of the drilling process is extended by decreasing the pressure further. For a low ambient pressure of 10 μbar, this is accompanied by an increase of the maximum achievable depth of more than 100%. Simultaneously the hole shape changes from a few ends and bulges at atmospheric conditions to numerous branches over the complete lower part of the hole at low pressure. This drilling behavior can be attributed to a better removal of ablated particles from the hole capillary with decreasing pressure, which leads to lower scattering losses for the pulse propagation inside the hole.
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In this paper, a novel method based on multichannel time delay estimation with linear fitting correction for laser time-of-flight (TOF) measurement is described. The laser TOF measurement system is constructed with a laser source, a stop receiver channel, a reference receiver multichannel, an ADC sampling unit and a digital signal processing unit. Limited by the sampling rate, the precision of laser TOF measurement is restricted no more than the ADC sampling period in conventional methods. As this problem is considered, multi-channel correlation time delay estimation with linear fitting correction is devised. It is shown that the measuring precision is better than 2ns with multi-channel time delay estimation and not influenced by SNR. The experimental results demonstrate that the proposed method is effective and stable.
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In this paper, we characterize the femtosecond laser filament-fringes in titanium. In order to fabricate regular arrays of filaments, we place either a pinhole or a beam shaper in the optical path of the femtosecond laser beam that originates linear diffraction of the laser beam. Soda-lime glass is used as Kerr medium to produce the filaments. As a consequence, the intensity distribution of the laser beam is modulated and fringe type of filament distributions is evident. The suitable control over the size of the diaphragms (pinhole or beam shaper) leads us to adjust the shape, orientation, and number of filaments in each irradiated spots in titanium sample. By properly adjusting the diameter of a pinhole that was placed in the optical path, we are successful in forming a single filament in titanium. By using these single filaments, we fabricated high aspect ratio periodic holes in the titanium surface by moving the translation stage in both horizontal and vertical directions. The period of the holes in the horizontal direction is controlled by varying the scanning speed, whereas the period in the vertical direction is controlled by varying the vertical scanning step. We strongly believe that, filamentation technology described in this paper will have applications in forming a variety of micro/nano-structures in various materials.
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High-speed video imaging was used to study the dynamic behavior of cavitation bubbles induced by a continuous wave (CW) laser into highly absorbing droplets water containing copper nitrate (CuNO4). The droplet lays horizontally on a glass surface and the laser beam (λ=975 nm) propagates vertically from underneath, across the glass and into the droplet. This beam is focused ζ=400 μm above the glass-liquid interface in order to produce the largest bubble as possible (Rmax ~ 1mm). In our experiment the thermocavitation bubbles are always in contact with the substrate, taking a hemispherical shape, regardless of where the laser focal point is, as opposed to the other methods that involved nano and picosecond laser pulses, where bubbles may nucleate and grow within the bulk of the fluid. We focus on the liquid jet which emerges out the droplet at velocities of about 3 m/s, due to the acoustic pressure wave (APW) emitted immediately after the bubble collapse, and after it breaks up into a secondary droplet or droplets depending of the droplet’s volume, showing an alternative way of droplet generator that is simplest, light and cheaper. The dynamics of cavitation bubbles in confined geometries (drops) offers a rich hydrodynamic and the liquid jet generated after the bubble collapse could be used like acoustic waveguide, as was showed by Nicolas Bertin et. al.
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In this paper, we present the investigation results on laser-induced structural modifications in a BK7 glass sample
(OHARA, S-BSL7) by use of a femtosecond laser and a CO2 laser system. A femtosecond fiber laser system (wavelength: 1.06 μm, pulse duration: 250 fs) generates 1 MHz ultrashort laser pulses with a pulse energy up to 2 μJ, and a CO2 laser system generates CW (continuous wave) laser beam with a wavelength of 10.6 μm. Both laser beams were simultaneously irradiated on a BK7 glass substrate (30 mm × 5 mm × 0.7 mm thick). The structural modifications regions were created by translating the glass sample perpendicular to the laser axis with a distance of 1 mm and a scan speed of 0.1 mm/s. The dependence of structural modifications on the laser energy of femtosecond laser pulses and the power of CO2 laser beam were investigated. The results have demonstrated that the refractive index change region with the width of 3 μm was created with simultaneously irradiation of two laser beams although the structural modification regions, which were produced with only femtosecond laser pulses, were surface ablation. And the surface ablation regions were changed to the refractive index change regions as the energy of CO2 laser beam increase to more than 2W.
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Laser Powder Deposition (LDP) techniques are being adopted within aerospace and automotive manufacturing to
produce innovative precision components. Non-destructive techniques (NDT) for detecting and quantifying flaws within these components enables performance and acceptance criteria to be verified, improving product safety and reducing ongoing maintenance and product repair costs. In this work, software enabled techniques are presented for in-process analysis of NDT laser ultrasonic signals and pulsed laser thermography images of sequential metallic LPD layers. LPD tracks can be as thin as 200μm while deposited at a rate of 500 mm/min, requiring ultrafast inspection and processing times. The research developed analysis algorithms that allow senior engineers to develop inspection templates and profiles for in-process inspection, as well as an end-to-end, user friendly interface for engineers to perform complete manual Laser Ultrasonic or Laser Thermographic inspections. Several algorithms are offered to quantify the flaw size. location and severity. The identified defects can be imported into a sentencing engine which then automatically compares analysis results against the user defined acceptance criteria so that the manufacturing products can be verified. Where both laser ultrasonic and laser thermographic NDT data is available further statistical tools could increase the confidence level of the inspection decision.
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