Showing papers in "Journal of Laser Micro Nanoengineering in 2014"
TL;DR: In this paper, the selectivity of laser-induced etching of single line modifications is investigated for a variation of repetition rate, pulse duration, pulse energy and feed rate for etching with KOH.
Abstract: Selective, laser-induced etching (SLE) is a process which offers the possibility of machining hollow volumes into transparent materials with a huge freedom of geometry in 3D. Every 3D structure consists of single lines of laser-induced modifications. The knowledge of selectivity for etching of these single lines of modification is crucial to identify stable process windows for the machining of completely integrated, complex 3D structures. The selectivity of laser-induced etching of single line modifications is investigated in this study for a variation of repetition rate, pulse duration, pulse energy and feed rate for etching with KOH.
74 citations
TL;DR: In this article, a hybrid microoptical component consisting of an aspherical and a conical lens integrated into a single monolithic element has been fabricated at the end face of a fiber using the technique of direct laser writing of photopolymers.
Abstract: A novel method to overcome the problem of accurately centering microoptical components built by direct laser writing on the tip of a single mode optical fiber is presented, and it includes employing mode field expansion. A hybrid microoptical component consisting of an aspherical and a conical lens integrated into a single monolithic element has been fabricated at the end-face of a fiber using the technique of direct laser writing of photopolymers. The optical performance of the fabricated microstructures has been measured experimentally. We show that optical properties of Gaussian and Bessel beams can be easily tuned by adjusting the geometrical parameters of fiber-tip microoptical elements. In addition, we experimentally demonstrate the increase of propagation distance of a Bessel beam five-fold, using the fabricated microoptical element. This improvement in the fabrication method of fiber-tip microoptical elements can be used in the manufacturing of integrated micro-optical devices for optical tweezing, laser micromachining and long focal depth optical systems.
37 citations
TL;DR: In this article, two different fabrication techniques using femtosecond filaments generated in water which is in contact with the transparent sample were demonstrated, which yielded holes made in soda-lime and fused silica glass samples which had thickness up to 1 mm.
Abstract: Microfabrication of transparent materials using femtosecond laser pulses has showed good potential towards industrial application. Maintaining pulse energies above the critical self-focusing limit produced filaments that were used for micromachining purposes. This article demonstrates two different fabrication techniques using femtosecond filaments generated in water which is in contact with the transparent sample. Both methods yielded through holes made in soda-lime and fused silica glass samples which had thickness up to 1 mm. These fabricated holes have an aspect ratio close to 20; moreover, the fabrication time is of the order of tens of seconds.
34 citations
TL;DR: In this article, the authors present recent developments in spatial modulation of laser radiation for welding the material combination of copper and steel in the field of battery welding and discuss the influence of the modulation amplitude.
Abstract: Lithium-ion battery cells are being increasingly used as energy storage devices for electrically powered vehicles on account of their high energy density. 18650-type cells provide an ideal solution thanks to their low price and ready availability. Compared with large-format cells, however, these cells have low capacity, which is why several individual cells have to be connected in parallel to create larger cells or suitable battery packs. In these cases, overlap welding is commonly used to join a copper current collector and battery can – the negative pole – made out of nickel-plated DC04 steel. The major challenge in welding batteries is melting both parts without damaging the can and causing the electrolyte to leak. Spatial modulation can be used to control weld depth very precisely. In this paper, we present recent developments in spatial modulation of laser radiation for welding the material combination of copper and steel in the field of battery welding and discuss the influence of the modulation amplitude. Also, we show the extent to which tensile strength influences the joint and the electrical resistance.
28 citations
TL;DR: In this article, a femtosecond direct laser writing system was supplemented by a machine vision to relocate the sample between different fabrication steps, and the resulting 3D microstructured scaffolds were used for cell studies and tissue engineering applications.
Abstract: Summary form only given. We present direct laser fabrication of 3D microstructured scaffolds consisting out of a few polymeric materials owning different biological properties. Direct laser writing in photo/thermo-sensitive materials using ultra short light pulses of high repetition laser provides unmatched flexibility in controllable 3D microstructuring in a variety of bio-materials [1], as well as manufacturing throughput empowers overall structure size of more than 1 mm3, making it an attractive method to fabricate scaffolds for cell studies and tissue engineering applications [2, 3]. In this work, a femtosecond direct laser writing system was supplemented by a machine vision [4] to relocate the sample between different fabrication steps.
28 citations
TL;DR: In this paper, the laser-induced forward transfer technique was used to print at high-speed long lines of metallic nanoparticle ink at velocities up to 4 m/s.
Abstract: We use the laser-induced forward transfer technique to print at high-speed long lines of metallic nanoparticle ink. A picosecond laser emitting at 343 nm with a repetition rate of 500 kHz is used to realize series of droplets and continuous lines by varying the distance between successive laser pulses. We find this latter parameter to be critical to obtain droplets of good quality, and use a time-resolved imaging technique to study its effects on the ink ejection. Single pass, two-pass and three-pass laser printing have been investigated. We have printed millimeter-long continuous silver lines of 20 mu m width and thinner than 500 nm, at velocities up to 4 m/s. This work demonstrates the feasibility of using high repetition rate laser for the fast and reliable printing of conductive lines.
22 citations
TL;DR: In this paper, a combination of a spatial light modulator (SLM) and a galvanometer scanner with an infrared nanosecond fiber laser was used to fabricate microstructures.
Abstract: Rapid method to fabricate microstructures using a combination of a spatial light modulator (SLM) and a galvanometer scanner with an infrared nanosecond fiber lasers is studied. Here the SLM is used as a computer generated hologram which can be applied to modify laser pulses intensity distribution virtually almost arbitrary. SLM is used to separate nanosecond pulses into the several spots so that multiple spots can be machined simultaneously with a fast ablation rate. In this paper it is shown that the micro-machining speeds that can be realized using a combination of the SLM and the scanner, are not always possible to realize using merely scanner. It is shown that about 0.6 million spots per second can be ablated in silicon using this combination.
18 citations
TL;DR: In this article, the formation of periodic grating structures on a titanium surface irradiated by a double-pulse beam with a time delay of 160 fs was demonstrated on a Ti surface.
Abstract: The formation of periodic grating structures has been demonstrated on a titanium surface irradiated by a double-pulse beam with a time delay of 160 fs. The first-pulse fluence FPP was varied and always kept below the threshold FTH = 60 mJ/cm 2 for forming periodic grating structures on Ti and the delayed pulse fluence FLP was kept above FTH. The grating structure interspaces were 0.5λL to 0.85λL and decreased with FPP for all values of FLP. This tendency suggests that variation in surface plasma density, which is associated with the fluence of the first pulse, led to variation of the grating interspaces. We found that the interspaces produced by double-pulse irradiation agreed relatively well with those produced by single-pulse irradiation and those predicted by a parametric decay model. To visualize the surface plasma wave induced by the femtosecond laser, two-dimensional particle-in-cell simulation was conducted for a preformed plasma on a metal. The simulation results suggest that the preformed plasma density led to the variation in the grating interspaces.
17 citations
TL;DR: In this paper, the structural color in 3D woodpile photonic crystal structures fabricated by femtosecond direct laser write (DLW) lithography in photoresist was obtained due to spectral regions with high optical reflectivity associated with higher photonic bands well above the fundamental (lowest frequency) photonic stop gap.
Abstract: We report realization of structural color in 3D woodpile photonic crystal structures fabricated by femtosecond direct laser write (DLW) lithography in photoresist. The structural color in the fabricated samples was obtained due to spectral regions with high optical reflectivity associated with higher photonic bands well above the fundamental (lowest frequency) photonic stop gap, which allowed realization of visible colors without the need to reduce the lattice period. This advantage facilitates easier and faster DLW fabrication, and can be exploited for realization of structural color materials for various applications, for example optical environmental sensing.
16 citations
TL;DR: Laser direct-write (LDW) techniques based on laser-induced forward transfer of functional materials offer unique advantages and capabilities for the rapid prototyping of electronic, optical and sensor elements as opposed to other digital printing processes like inkjet as mentioned in this paper.
Abstract: Laser direct-write (LDW) techniques based on laser-induced forward transfer (LIFT) of functional materials offer unique advantages and capabilities for the rapid prototyping of electronic, optical and sensor elements as opposed to other digital printing processes like inkjet. LIFT processes have been applied to the fabrication of a wide variety of microelectronic elements such as interconnects, passive components, antennas, sensors, power sources and embedded circuits. Overall, LDW techniques are highly adaptable digital microfabrication processes in terms of materials versatility, substrate compatibility and range of writing speed, scale and resolution. This article will describe the unique advantages and capabilities of LIFT-based processes when used in conjunction with fluids and nanopastes, discuss their applications and consider their future for printing electronics.
16 citations
TL;DR: In this paper, a laser grooving on back surface of Si substrate by an infrared femtosecond laser was studied, where the laser was focused at the back of the Si substrate.
Abstract: Silicon (Si) is widely used material in microelectronics, MEMS, photonics and more. Although Si is not transparent for commonly used processing lasers in near infrared to ultraviolet spectral range, the light at low energy than its band gap energy should be transmit through Si substrate. Using a short pulse laser in this wavelength range, non-linear machining of Si should be performed just like non-linear processing of transparent materials by conventional lasers. In this study, we have been studied a laser grooving on back surface of Si substrate by an infrared femtosecond laser. The laser was focused at the back of the Si substrate. The top surface of the Si showed no change while morphology of back surface changes into aggregation of small particles, the size of which is about 500 nm. From cross sectional view of the Si substrate, a structural change was observed in regions close to the focus position. Raman spectra indicate that the single crystal Si was transformed into amorphous and poly-crystal Si in irradiated region. Although machining for the back surface of the Si is quite difficult, machining of the grooves of few micrometers was achieved in the laser-assisted wet etching using KOH solution.
TL;DR: In this paper, a double-pulse laser-induced dot transfer technique was proposed to realize on-demand deposition of functional oxide microdots under room-temperature atmospheric conditions, where the first pulse was irradiated to preheat an oxide source film, and the second pulse was more tightly focused on the same position to deposit an oxide microdot onto a receiver substrate.
Abstract: We have newly developed a double-pulse laser-induced dot transfer technique to realize ondemand deposition of functional oxide microdots under room-temperature atmospheric conditions. In our double-pulse system, the first pulse was irradiated to preheat an oxide source film, and then the second pulse was more tightly focused on the same position to deposit an oxide microdot onto a receiver substrate. As a model case, indium tin oxide microdots with much smaller lateral dimensions than the laser focal area were reproducibly arrayed on a silica glass substrate by the doublepulse process, while there were microdot vacancies at a rate of approximately 30 % in the case of a single-pulse process without preheating. In order to explore the effect of double-pulse, laser-induced temperature distribution was also investigated from a finite elemental approach.
TL;DR: In this article, a mid-infrared resonant ablation of polymethyl methacrylate (PMMA) is presented, employing nanosec-ond laser pulses tunable between 3 and 4 microns.
Abstract: Laser ablation proved to be a reliable micro-fabrication technique for patterning and structuring of both thin film and bulk polymer materials. In most of the industrial applications ultra-violet (UV) laser sources are employed, however they have limitations such as maintenance costs and practical issues. As an alternative and promising approach, mid-infrared resonant laser ablation (RIA) has been introduced, in which the laser wavelength is tuned to one of the molecular vibrational transi-tions of the polymer to be ablated. Consequently, the technique is selective in respect of processing a diversity of polymers which usually have different infrared absorption bands. In this paper, we present mid-infrared resonant ablation of PolyMethyl MethAcrylate (PMMA), employing nanosec-ond laser pulses tunable between 3 and 4 microns. This RIA nanosecond laser set-up is based on a commercial laser at 1064 nm pumping a singly resonant Optical Parametric Oscillator (OPO) built around a Periodically-Poled Lithium Niobate (PPLN) crystal with several Quasi-Phase Matching (QPM) periods. RIA has been successfully demonstrated for structuring bulk PMMA, and selective patterning of PMMA thin films on a glass substrate has been implemented.
TL;DR: In this article, the authors reviewed the emerging fabrication techniques for transparent materials such as glass and crystal that use focused ultra-short laser pulses from the viewpoint of functionalities of the products to be integrated into a future photonic system.
Abstract: The emerging fabrication techniques for transparent materials such as glass and crystal that use focused ultra-short laser pulses will be reviewed from the viewpoint of functionalities of the products to be integrated into a future photonic system. The devices include waveguide and waveguide couplers, mirrors and lenses, filters and holograms. The future photonic system may consist of many functional subsystems which are connected through transparent gates or windows. Welding technique may play an important role for this system integration. The welding technique for transparent materials using ultra-short laser pulses will also be reviewed along with applications to hermetic sealing. The author presents experimental results on the temperature dynamics. The author will also discuss on an idea connecting the relaxation of internal stress and the high index change and a role of the void and its motion in the fabrication process. The bright near future and challenges of the glass processing techniques with ultrafast lasers will briefly be touched on.
TL;DR: In this paper, the polarization-dependent anisotropy of the laser induced nanostructures inside SiO2 and GeO2 glass was demonstrated, which is controllable by the femtosecond double-pulse configuration.
Abstract: We demonstrate the polarization-dependent anisotropy of the laser induced nanostructures inside SiO2 and GeO2 glass. Such nanostructures show form birefringence which is controllable by the femtosecond double-pulse configuration. In the case of SiO2 glass, we have also demonstrate polarization imaging filter based on the linear dichroism for the visible light ranging from 400 to 800 nm. While, in the case of GeO2 glass, the decomposition of constituent elements according to increase in laser energy was also observed.
TL;DR: In this paper, an advanced micro-stereo-lithography process combined with single photon polymerization and aerosol jet printing technology was developed to facilitate layer based photo-polymerized structuring by layer on a non-flat surface, which is not possible by conventional macroor microstereolithography.
Abstract: We have developed an advanced micro-stereo-lithography process combined with single photon polymerization and aerosol jet printing technology to facilitate layer based photo-polymerized structuring by layer on a non-flat surface, which is not possible by conventional macroor microstereolithography. The aerosolized photo-sensitive polymer retains its photo-curable characteristics (compared with its original liquid state). The photo-polymerization using UV laser irradiation achieved 6 μm in the horizontal resolution, while aerosol jet printing technology achieved 0.6 μm in the vertical resolution, individually. By means of this process we successfully produced 2D and 3D structures, and a straight-line photo-polymerized structure was produced on a non-flat surface.
TL;DR: In this paper, high-PRF (pulse repetition frequency) femtosecond laser systems were combined with fast galvanometer scanner systems to increase the volume ablation rate of zirconium oxide and stainless steel.
Abstract: This paper discusses results obtained in highspeed laser micro processing of zirconium oxide ceramic and stainless steel. High-PRF (pulse repetition frequency) femtosecond laser systems were joined together with fast galvanometer scanner systems. A high average laser power (31.7 W) and fast scan speeds (17.1 m/s) were applied in order to increase material removal. The influence of average laser power, laser energy and repetition rate on both the volume ablation rate and the machining quality was studied. The maximum volume ablation rate for zirconium oxide was 70.3 µm³ per pulse, obtained with pulses of 5.9 µJ energy and 1.02 MHz. It is demonstrated that material removal on zirconium oxide will be strongly affected by heat. Stainless steel was irradiated with a maximum laser power of 31.7 W and various repetition rates. The maximum material removal rate was found to be 6.8 mm³ / min, achieved with laser pulses of 0.85 J/cm² fluence. The feasibility of the highspeed laser technology in micro processing is verified by machining examples. In addition, a demonstrator of 80 x 80 mm² was machined with a processing rate as high as 25 cm² / min.
TL;DR: In this paper, a comprehensive axisymmetric model, including a two-temperature model, phase change models for rapid melting and evaporation, and a phase explosion model for ejecting metastable liquid and vapor, was developed to simulate the laser material ablation process.
Abstract: Thermal ablation of copper films by a single Ti:Sapphire femtosecond laser pulse of wavelength 800 nm and duration 100 fs was investigated experimentally and theoretically. The laser experiments were performed; the ablation depth and crater profiles were measured for laser fluences up to 1037 J/cm. A comprehensive axisymmetric model, including a two-temperature model, phase change models for rapid melting and evaporation, and a phase explosion model for ejecting metastable liquid and vapor, was developed to simulate the laser material ablation process. The simulated ablation depths and crater profiles agree well with the experimental measurements.
TL;DR: In this paper, the ablation characteristics and ablation thresholds are identified for single and multiple irradiation of the lens material by picosecond pulses and the results are used for quantification of the incubation effect.
Abstract: Material processing by ultra-short pulsed laser ablation is an attractive approach for various applications. In this paper we present our studies on cutting of medical polymers used for intraocular lenses (IOL). To achieve best results the ablation characteristics and the ablation thresholds are identified for single and multiple irradiation of the lens material by picosecond pulses. The results are used for quantification of the incubation effect. Furthermore, cutting experiments are carried out and thereby different damage types can be observed. A process window is developed containing the regions of the respective types of damages and backed up by theoretical considerations.
TL;DR: In this article, the flexural strength was measured using a 3-point bending test and the results revealed that among the experimental parameters the laser focus position has the highest influence on the flexuric strength, reducing it by 63 MPa.
Abstract: mm 2 with the flexural strength being measured using a 3 point bending test. Based on a design of experiments approach the results reveal that among the experimental parameters the laser focus position has the highest influence on the flexural strength, reducing it by 63 MPa. Cutting alumina at 300 mm/s yields a flexural strength of 395 MPa, which is significantly lower as compared with reference samples produced by scribe and break having a flexural strength of 520 MPa. Yet, a comparable flexural strength of 311 MPa using a CO2 laser is achieved at only 20 mm/s. To cut small contours, digital modulation of the fiber laser output power is employed leading to a flexural strength of 506 MPa at 1 mm/s and 469 MPa at 10 mm/s. Further results show that additional outer contours can halve the flexural strength and the lack of rounding reduces the flexural strength further. Inner contours especially with corners are also decreasing the flexural strength drastically while an inner circle causes only low strength reduction.
TL;DR: Shamim et al. as discussed by the authors proposed a method to improve the performance of the KAIST Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), which is a part of the Korean National Institute of Advanced and Advanced Photonics Research Institute (APRI).
Abstract: *1 Electronics and Communication Engineering Discipline, School of Science, Engineering and Technology, Khulna University, Khulna 9208, Bangladesh *2 R&D Center, Samsung Corning Precision Materials, 1320-10 Seocho-dong, Seocho-gu, Seoul, Republic of Korea. *3 Advanced Photonics Research Institute (APRI), Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712, Republic of Korea *4 Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea E-mail: shamim@kaist.ac.kr
TL;DR: This work applied two-photon polymerization to fabricate threedimensional microenvironments composed of a matrix arrangement of microstructures with distinct spacing to evaluate the growth of Michigan Cancer Foundation-7 (MCF-7) cells.
Abstract: Studies of cell development in artificial microenvironments can contribute to understanding a series of physiological mechanisms that might be influenced by geometrical features of the microenvironment itself. In this work we applied two-photon polymerization to fabricate threedimensional microenvironments composed of a matrix arrangement of microstructures (circular and square cross-sections pillars) with distinct spacing. Such microenvironments were used to evaluate the growth of Michigan Cancer Foundation-7 (MCF-7) cells that are commonly used as a model system to investigate fundamental aspects of the tumor biology. Our results reveal that the cell density decreases as the distance between structures in the environment is increased. Additionally, cell growth shows slightly better results for the microenvironments composed of circular crosssection structures.
TL;DR: In this paper, the authors used a combination of a 4ω Nd:YAG laser and a phase mask, which is simpler than the conventional method using a 2ω cw Ar laser and the Lloyd mirror interferometer.
Abstract: We have developed a simplified technique to fabricate tilted fiber Bragg gratings (TFBGs) for simultaneous measurement of the refractive index and temperature of liquids in biochemical and medical applications. We used a combination of a 4ω Nd:YAG laser and a phase mask, which is simpler than the conventional method using a 2ω cw Ar laser and a Lloyd mirror interferometer. The peak of the cladding mode of the TFBG shifted to the longer wavelength side as the refractive index of liquid increased. Furthermore, both the peak of the cladding mode and that of the core mode shifted to the longer wavelength side as the temperature of liquid increased. We found that a refractive index from 1 to 1.41, and a temperature from 293 to 353 K could be measured with a single probe of the fabricated TFBGs.
TL;DR: In this article, a femtosecond laser and a spatial light modulator (SLM) were used to reduce the recording pulse energy and interlayer crosstalk by correcting spherical aberration.
Abstract: A storage system using fused silica is a promising way to store historically valuable data permanently. To increase recording capacity, we studied the recording and reading conditions for a multilayer sample. The 26-layer sample, which had a recording capacity equivalent to that of a digital versatile disc (DVD), was made with a femtosecond laser and a spatial light modulator (SLM). The recording pulse energy and interlayer crosstalk were reduced by correcting spherical aberration. The sample was evaluated and read with an optical microscope. The signal-to-noise ratio (SNR) criterion of 15 dB was satisfied in all 26 layers by using signal processing. Thermal resistance at 1,000 °C for 120 minutes was demonstrated, suggesting a semi-permanent lifetime.
TL;DR: In this article, the authors demonstrate the grayscale modifications of an anodized aluminium plate by using ultra-short laser pulses, and the results on influence of laser marking process parameters on the blackness of marking obtained are presented.
Abstract: In this work, we demonstrate the grayscale modifications of an anodized aluminium plate by using ultra-short laser pulses. The measurement and analysis results on influence of the laser marking process parameters on the blackness of marking obtained are presented. The study was conducted for the aluminium plate with the transparent anodizing Al2O3 coating by using a commercially available industrial picosecond laser and galvanometer scanner. The grayscale of marking was changed by scanning the laser beam focused at the boundary of the coating and aluminium sheet without damaging the transparent coating. The scanning speed and mean laser power was varied in order to enhance the blackness of the marking. It was determined experimentally how various process parameters, such as the laser power, pulse repetition rate, irradiation time per square millimetre affected the luminance Y´ of the grayscale obtained. The grayscale modifications starting from 40 % grey (untreated sample) to 93 % grey were achieved without damaging the protective Al2O3 coating.
TL;DR: In this article, single and multiple laser pulse hole drilling in fused silica has been carried out using a CO2 laser system operating at 10.6 μm, and the results are compared against the predictions of a numerical model.
Abstract: Single and multiple laser pulse hole drilling in fused silica have been carried out using a CO2 laser system operating at 10.6 μm. Laser pulse duration, pulse energy and number of pulses impinging on the silica plate have been measured in-situ for drilled holes. Hole depths, diameter and volume have been measured using a fluorescent confocal microscope and the results are compared against the predictions of a numerical model. This model considers surface evaporation as the main material removal mechanism. For the case of single pulse drilling, the depth and volume of the drilled holes are predicted accurately and the discrepancy between the model and experiments are observed to be less than 10%.
TL;DR: In this article, a CW fiber laser was used to reduce the electrical resistance of the TiO2 film by changing the temperature of the laser focusing spot area on the film, which is a useful method to create the oxygen deficiencies in local area of the film.
Abstract: Titanium dioxide (TiO2) film has photocatalytic properties and good biocompatibility. To expand the film application, formation of oxygen deficiencies in the film was one of the useful methods. Electrical resistance of the film can be decreased due to oxygen deficiencies formation. The local heating process in vacuum is a useful method to create the oxygen deficiencies in local area of the film. Electrical resistance might be locally decreased by local heating with a CW fiber laser. In our experiment, the films were irradiated with the laser in vacuum. Control of temperature on the film was very important for reducing the electrical resistance. Therefore, temperature monitoring of the laser focusing spot area on the film was performed. Temperature of the laser focusing spot area was increased as the laser intensity was increased. Then, the electrical resistance of the laser focusing spot area was decreased as the laser intensity was increased. Thus, electrical resistance of the laser focusing spot area was decreased as temperature of the laser focusing spot area was increased. These results indicated that electrical resistance of the laser focusing spot area was controlled by changing temperature on the laser focusing spot area.
TL;DR: A method for determining the interference contrast by measuring the virtual shift of the ablation threshold and proves to be a useful tool for characterization of the interference pattern.
Abstract: Multi-Beam-Interference (MBI) is a promising approach for the direct nano structuring of surfaces. An important characteristic of MBI is the interference contrast which describes the modulation depth of the intensity distribution. While theoretical calculation for the interference contrast exists in literature, no actual measurement in experiments is documented. In this paper we present a method for determining the interference contrast by measuring the virtual shift of the ablation threshold. This virtual shift is caused by the modified intensity distribution via interference. At first, the theoretical basis for the measuring method is introduced, secondly the method is tested with a two beam interference setup used for direct structuring of surfaces. The measuring method shows consistent results and proves to be a useful tool for characterization of the interference pattern.
TL;DR: In this article, a single shot pump and probe reflective imaging using a soft x-ray laser probe was used to avoid the timing error due to the jitter, and a posteriori correction technique was adopted by simultaneous measurement of timing between the probe and pump pulses for every single shot.
Abstract: Femtosecond laser ablation processes on platinum, gold, and tungsten were observed by the single shot pump and probe reflective imaging using a soft x-ray laser probe. To avoid the timing error due to the jitter, we adopted a posteriori correction technique by simultaneous measurement of timing between the pump and probe pulses for every single shot, using a soft x-ray streak camera. A clear difference was found in the temporal behavior of the dynamical response of the soft x-ray reflectivity depending on the irradiated laser fluence in these three materials. On the other hand, the narrow dark rings were found in Pt and W, while an additional bright ring was found outside the dark disk in Au. Our result gives the experimental data comparable with various numerical simulations.