An improved three-dimensional two-temperature model for multi-pulse femtosecond laser ablation of aluminum

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jinping; Chen, Yuping, E-mail: ypchen@sjtu.edu.cn; Hu, Mengning; Chen, Xianfeng [State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China)

2015-02-14

In this paper, an improved three-dimensional two-temperature model for multi-pulse femtosecond laser ablation of aluminum was proposed and proved in our experiment. Aiming to achieve hole-drilling with a high ratio of depth/entrance diameter in vacuum, this model can predict the depth and radius of the drilled holes precisely when employing different laser parameters. Additionally, for multi-pulse laser ablation, we found that the laser fluence and number of pulses are the dominant parameters and the multi-pulse ablation threshold is much lower than the single-pulse one, which will help to obtain high-quality holes.

Single and double long pulse laser ablation of aluminum induced in air and water ambient

International Nuclear Information System (INIS)

Akbari Jafarabadi, Marzieh; Mahdieh, Mohammad Hossein

2017-01-01

Highlights: • Laser ablation of aluminum target by single and double pulse (∼ 5 ns delay) in ambient air and distilled water • Comparing with air, in ambient water, plasma confinement results in higher crater depth. • In comparison with single pulse laser ablation, the absorption of the laser pulse energy is higher for double pulse regime. • As a result of ablated material expansion, the crater depth is decreased if the target is placed at lower depth. - Abstract: In this paper, single pulse and double pulse laser ablation of an aluminum target in two interaction ambient was investigated experimentally. The interaction was performed by nanosecond Nd:YAG laser beam in air and four depths (i.e. 9, 13, 17, and 21 mm) of distilled water ambient. The irradiation was carried out in single and collinear double pulse configurations in both air and liquid ambient. Crater geometry (depth and diameter) was measured by an optical microscope. The results indicated that the crater geometry strongly depends on both single pulse and double pulse configurations and interaction ambient. In single pulse regime, the crater diameter is higher for all water depths compared to that of air. However, the crater depth, depend on water depth, is higher or lower than the crater depth in air. In double pulse laser ablation, there are greater values for both crater diameters and crater depths in the water.

Applications of ultra-short pulsed laser ablation: thin films deposition and fs/ns dual-pulse laser-induced breakdown spectroscopy

International Nuclear Information System (INIS)

Teghil, R; De Bonis, A; Galasso, A; Santagata, A; Albano, G; Villani, P; Spera, D; Parisi, G P

2008-01-01

In this paper, we report a survey of two of the large number of possible practical applications of the laser ablation performed by an ultra-short pulse laser, namely pulsed laser deposition (PLD) and fs/ns dual-pulse laser-induced breakdown spectroscopy (DP-LIBS). These applications differ from those using just longer pulsed lasers as a consequence of the distinctive characteristics of the plasma produced by ultra-short laser beams. The most important feature of this plasma is the large presence of particles with nanometric size which plays a fundamental role in both applications.

Water spray assisted ultrashort laser pulse ablation

International Nuclear Information System (INIS)

Silvennoinen, M.; Kaakkunen, J.J.J.; Paivasaari, K.; Vahimaa, P.

2013-01-01

Highlights: ► We show the novel method to use multibeam processing with ultrashort pulses efficiently. ► Sprayed thin water layer on ablation zone enhances ablation rate and quality. ► In some cases this method also enables ablation of the deeper and straighter holes compared to ones made without the water layer. ► Method also makes possible to directly write features without the self-organizing structures. - Abstract: We have studied femtosecond ablation under sprayed thin water film and its influence and benefits compared with ablation in the air atmosphere. These have been studied in case of the hole and the groove ablation using IR femtosecond laser. Water enhances the ablation rate and in some situations it makes possible to ablate the holes with a higher aspect ratio. While ablating the grooves, the water spray allows using the high fluences without the generation of the self-organized structures.

LASER ABLATION OF MONOCRYSTALLINE SILICON UNDER PULSED-FREQUENCY FIBER LASER

Directory of Open Access Journals (Sweden)

V. P. Veiko

2015-05-01

Full Text Available Subject of research. The paper deals with research of the surface ablation for single-crystal silicon wafers and properties of materials obtained in response to silicon ablation while scanning beam radiation of pulse fiber ytterbium laser with a wavelenght λ = 1062 nm in view of variation of radiation power and scanning modes. Method. Wafers of commercial p-type conductivity silicon doped with boron (111, n-type conductivity silicon doped with phosphorus (100 have been under research with a layer of intrinsical silicon oxide having the thickness equal to several 10 s of nanometers and SiO2 layer thickness from 120 to 300 nm grown by thermal oxidation method. The learning system comprises pulse fiber ytterbium laser with a wavelenght λ = 1062 nm. The laser rated-power output is equal to 20 W, pulse length is 100 ns. Pulses frequency is in the range from 20 kHz to 100 kHz. Rated energy in the pulse is equal to 1.0 mJ. Scanning has been carried out by means of two axial scanning device driven by VM2500+ and controlled by personal computer with «SinMarkТМ» software package. Scanning velocity is in the range from 10 mm/s to 4000 mm/s, the covering varies from 100 lines per mm to 3000 lines per mm. Control of samples has been carried out by means of Axio Imager A1m optical microscope Carl Zeiss production with a high definition digital video camera. All experiments have been carried out in the mode of focused laser beam with a radiation spot diameter at the substrate equal to 50 μm. The change of temperature and its distribution along the surface have been evaluated by FLIR IR imager of SC7000 series. Main results. It is shown that ablation occurs without silicon melting and with plasma torch origination. The particles of ejected silicon take part in formation of silicon ions plasma and atmosphere gases supporting the plasmo-chemical growth of SiO2. The range of beam scanning modes is determined where the growth of SiO2 layer is observed

Ablation of silicon with bursts of femtosecond laser pulses

Science.gov (United States)

Gaudiuso, Caterina; Kämmer, Helena; Dreisow, Felix; Ancona, Antonio; Tünnermann, Andreas; Nolte, Stefan

2016-03-01

We report on an experimental investigation of ultrafast laser ablation of silicon with bursts of pulses. The pristine 1030nm-wavelength 200-fs pulses were split into bursts of up to 16 sub-pulses with time separation ranging from 0.5ps to 4080ps. The total ablation threshold fluence was measured depending on the burst features, finding that it strongly increases with the number of sub-pulses for longer sub-pulse delays, while a slowly increasing trend is observed for shorter separation time. The ablation depth per burst follows two different trends according to the time separation between the sub-pulses, as well as the total threshold fluence. For delays shorter than 4ps it decreases with the number of pulses, while for time separations longer than 510ps, deeper craters were achieved by increasing the number of subpulses in the burst, probably due to a change of the effective penetration depth.

Pulsed-laser ablation of co-deposits on JT-60 graphite tile

International Nuclear Information System (INIS)

Sakawa, Youichi; Watanabe, Daisuke; Shibahara, Takahiro; Sugiyama, Kazuyoshi; Tanabe, Tetsuo

2007-01-01

Pulsed laser ablation of the co-deposits on a JT-60 open-divertor tile using the fourth harmonic of a 20 ps-Nd: YAG laser has been investigated. With increasing the laser intensity, three regions, non-ablation region (NAR), weak-ablation region (WAR), and strong-ablation region (SAR) were distinguished. Transition from NAR to WAR and WAR to SAR occurred at the threshold laser intensity for laser ablation and that for strong ionization of carbon atoms, respectively. The ablation accompanied desorption of H 2 and C 2 H 2 , with minor contribution of other hydrocarbons, while production of H 2 O was small. In NAR and WAR the number of the hydrogen desorbed by the laser irradiation was less than that of hydrogen retained in the ablated volume, while in SAR it was much larger, owing to thermal desorption of hydrogen gas from the region surrounding the ablated volume. For the ablative removal of hydrogen isotopes, SAR is more desirable because of higher removal efficiency and less production of hydrocarbons

Pulsed-laser ablation of co-deposits on JT-60 graphite tile

Energy Technology Data Exchange (ETDEWEB)

Sakawa, Youichi [Institute of Laser Engineering, Osaka University, Yamadaoka, Suita, Osaka 565-0871 (Japan)]. E-mail: sakawa-y@ile.osaka-u.ac.jp; Watanabe, Daisuke [Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Shibahara, Takahiro [Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Sugiyama, Kazuyoshi [Interdisciplinary School of Engineering Science, Kyushu University, Fukuoka, Fukuoka 812-8581 (Japan); Tanabe, Tetsuo [Interdisciplinary School of Engineering Science, Kyushu University, Fukuoka, Fukuoka 812-8581 (Japan)

2007-08-01

Pulsed laser ablation of the co-deposits on a JT-60 open-divertor tile using the fourth harmonic of a 20 ps-Nd: YAG laser has been investigated. With increasing the laser intensity, three regions, non-ablation region (NAR), weak-ablation region (WAR), and strong-ablation region (SAR) were distinguished. Transition from NAR to WAR and WAR to SAR occurred at the threshold laser intensity for laser ablation and that for strong ionization of carbon atoms, respectively. The ablation accompanied desorption of H{sub 2} and C{sub 2}H{sub 2}, with minor contribution of other hydrocarbons, while production of H{sub 2}O was small. In NAR and WAR the number of the hydrogen desorbed by the laser irradiation was less than that of hydrogen retained in the ablated volume, while in SAR it was much larger, owing to thermal desorption of hydrogen gas from the region surrounding the ablated volume. For the ablative removal of hydrogen isotopes, SAR is more desirable because of higher removal efficiency and less production of hydrocarbons.

Laser pulse guiding and electron acceleration in the ablative capillary discharge plasma

International Nuclear Information System (INIS)

Kameshima, T.; Kotaki, H.; Kando, M.; Daito, I.; Kawase, K.; Fukuda, Y.; Homma, T.; Esirkepov, T. Zh.; Chen, L. M.; Kondo, S.; Bobrova, N. A.; Sasorov, P. V.; Bulanov, S. V.

2009-01-01

The results of experiments are presented for the laser electron acceleration in the ablative capillary discharge plasma. The plasma channel is formed by the discharge inside the ablative capillary. The intense short laser pulse is guided over a 4 cm length. The generated relativistic electrons show both the quasimonoenergetic and quasi-Maxwellian energy spectra, depending on laser and plasma parameters. The analysis of the inner walls of the capillaries that underwent several tens of shots shows that the wall deformation and blistering resulted from the discharge and laser pulse effects.

Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Geohegan, D.B.

1994-09-01

Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume.

Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition

International Nuclear Information System (INIS)

Geohegan, D.B.

1994-01-01

Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume

Simulation of the impact of refractive surgery ablative laser pulses with a flying-spot laser beam on intrasurgery corneal temperature.

Science.gov (United States)

Shraiki, Mario; Arba-Mosquera, Samuel

2011-06-01

To evaluate ablation algorithms and temperature changes in laser refractive surgery. The model (virtual laser system [VLS]) simulates different physical effects of an entire surgical process, simulating the shot-by-shot ablation process based on a modeled beam profile. The model is comprehensive and directly considers applied correction; corneal geometry, including astigmatism; laser beam characteristics; and ablative spot properties. Pulse lists collected from actual treatments were used to simulate the temperature increase during the ablation process. Ablation efficiency reduction in the periphery resulted in a lower peripheral temperature increase. Steep corneas had lesser temperature increases than flat ones. The maximum rise in temperature depends on the spatial density of the ablation pulses. For the same number of ablative pulses, myopic corrections showed the highest temperature increase, followed by myopic astigmatism, mixed astigmatism, phototherapeutic keratectomy (PTK), hyperopic astigmatism, and hyperopic treatments. The proposed model can be used, at relatively low cost, for calibration, verification, and validation of the laser systems used for ablation processes and would directly improve the quality of the results.

Determination of ablation threshold for composite resins and amalgam irradiated with femtosecond laser pulses

International Nuclear Information System (INIS)

Freitas, A Z; Samad, R E; Zezell, D M; Vieira Jr, N D; Freschi, L R; Gouw-Soares, S C

2010-01-01

The use of laser for caries removal and cavity preparation is already a reality in the dental clinic. The objective of the present study was to consider the viability of ultrashort laser pulses for restorative material selective removal, by determining the ablation threshold fluence for composite resins and amalgam irradiated with femtosecond laser pulses. Lasers pulses centered at 830 nm with 50 fs of duration and 1 kHz of repetition rate, with energies in the range of 300 to 770 μJ were used to irradiate the samples. The samples were irradiated using two different geometrical methods for ablation threshold fluence determinations and the volume ablation was measured by optical coherence tomography. The shape of the ablated surfaces were analyzed by optical microscopy and scanning electron microscopy. The determined ablation threshold fluence is 0.35 J/cm 2 for the composite resins Z-100 and Z-350, and 0.25 J/cm 2 for the amalgam. These values are half of the value for enamel in this temporal regime. Thermal damages were not observed in the samples. Using the OCT technique (optical coherence tomography) was possible to determine the ablated volume and the total mass removed

Cutting and skin-ablative properties of pulsed mid-infrared laser surgery.

Science.gov (United States)

Kaufmann, R; Hartmann, A; Hibst, R

1994-02-01

Pulsed mid-infrared lasers allow a precise removal of soft tissues with only minimal thermal damage. To study the potential dermatosurgical usefulness of currently available systems at different wavelengths (2010-nm Thulium:YAG laser, 2100-nm Holmium:YAG laser, 2790-nm Erbium:YSGG laser, and 2940-nm Erbium:YAG laser) in vivo on pig skin. Immediate effects and wound healing of superficial laser-abrasions and incisions were compared with those of identical control lesions produced by dermabrasion, scalpel incisions, or laser surgery performed by a 1060-nm Nd:YAG and a 1060-nm CO2 laser (continuous and superpulsed mode). Best efficiency and least thermal injury was found for the pulsed Erbium:YAG laser, leading to ablative and incisional lesions comparable to those obtained by dermabrasion or superficial scalpel incisions, respectively. In contrast to other mid-infrared lasers tested, the 2940-nm Erbium:YAG laser thus provides a potential instrument for future applications in skin surgery, especially when aiming at a careful ablative removal of delicate superficial lesions with maximum sparing of adjacent tissue structures. However, in the purely incisional application mode pulsed mid-infrared lasers, though of potential usefulness in microsurgical indications (eg, surgery of the cornea), do not offer a suggestive alternative to simple scalpel surgery of the skin.

Comparison of the laser ablation process on Zn and Ti using pulsed digital holographic interferometry

Energy Technology Data Exchange (ETDEWEB)

Amer, E., E-mail: eynas.amer@ltu.se [Department of Applied Physics and Mechanical Engineering, Lulea University of Technology, SE-971 87 Lulea (Sweden); Gren, P.; Kaplan, A.F.H.; Sjoedahl, M. [Department of Applied Physics and Mechanical Engineering, Lulea University of Technology, SE-971 87 Lulea (Sweden); El Shaer, M. [Department of Engineering Physics and Mathematics, Faculty of Engineering, Zagazig University, Zagazig (Egypt)

2010-05-01

Pulsed digital holographic interferometry has been used to compare the laser ablation process of a Q-switched Nd-YAG laser pulse (wavelength 1064 nm, pulse duration 12 ns) on two different metals (Zn and Ti) under atmospheric air pressure. Digital holograms were recorded for different time delays using collimated laser light (532 nm) passed through the volume along the target. Numerical data of the integrated refractive index field were calculated and presented as phase maps. Intensity maps were calculated from the recorded digital holograms and are used to calculate the attenuation of the probing laser beam by the ablated plume. The different structures of the plume, namely streaks normal to the surface for Zn in contrast to absorbing regions for Ti, indicates that different mechanisms of laser ablation could happen for different metals for the same laser settings and surrounding gas. At a laser fluence of 5 J/cm{sup 2}, phase explosion appears to be the ablation mechanism in case of Zn, while for Ti normal vaporization seems to be the dominant mechanism.

Femtosecond laser ablation of silver foil with single and double pulses

CSIR Research Space (South Africa)

Roberts, DE

2009-01-01

Full Text Available The average ablation depth per pulse of silver foil by 130 fs laser pulses has been measured in vacuum over a range of three orders of magnitude of pulse fluence up to 900 J cm-2. In addition, double pulses with separations up to 3.4 ns have been...

Advances in laser ablation of materials

International Nuclear Information System (INIS)

Singh, R.K.; Lowndes, D.H.; Chrisey, D.B.; Fogarassy, E.; Narayan, J.

1998-01-01

The symposium, Advances in Laser Ablation of Materials, was held at the 1998 MRS Spring Meeting in San Francisco, California. The papers in this symposium illustrate the advances in pulsed laser ablation for a wide variety of applications involving semiconductors, superconductors, metals, ceramics, and polymers. In particular, advances in the deposition of oxides and related materials are featured. Papers dealing with both fundamentals and the applications of laser ablation are presented. Topical areas include: fundamentals of ablation and growth; in situ diagnostics and nanoscale synthesis advances in laser ablation techniques; laser surface processing; pulsed laser deposition of ferroelectric, magnetic, superconducting and optoelectronic thin films; and pulsed laser deposition of carbon-based and polymeric materials. Sixty papers have been processed separately for inclusion on the data base

Synthesis of higher diamondoids by pulsed laser ablation plasmas in supercritical CO2

International Nuclear Information System (INIS)

Nakahara, Sho; Stauss, Sven; Kato, Toru; Terashima, Kazuo; Sasaki, Takehiko

2011-01-01

Pulsed laser ablation (wavelength 532 nm; fluence 18 J/cm 2 ; pulse width 7 ns; repetition rate 10 Hz) of highly oriented pyrolytic graphite was conducted in adamantane-dissolved supercritical CO 2 with and without cyclohexane as a cosolvent. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp 3 -hybridized carbons similar to diamond structures. The synthesis of diamantane and other possible diamondoids consisting of up to 12 cages was confirmed by gas chromatography-mass spectrometry. Furthermore, gas chromatography-mass spectrometry measurements of samples before and after pyrolysis treatment indicate the synthesis of the most compact decamantane, namely, superadamantane. It is thought that oxidant species originating from CO 2 during pulsed laser ablation might lead to the selective dissociation of C-H bonds, enabling the synthesis of low H/C ratio molecules. Therefore, laser ablation in supercritical CO 2 is proposed as a practical method for synthesizing diamondoids.

Characteristics of Droplets Ejected from Liquid Propellants Ablated by Laser Pulses in Laser Plasma Propulsion

International Nuclear Information System (INIS)

Zheng Zhiyuan; Gao Hua; Fan Zhenjun; Xing Jie

2014-01-01

The angular distribution and pressure force of droplets ejected from liquid water and glycerol ablated by nanosecond laser pulses are investigated under different viscosities in laser plasma propulsion. It is shown that with increasing viscosity, the distribution angles present a decrease tendency for two liquids, and the angular distribution of glycerol is smaller than that of water. A smaller distribution leads to a higher pressure force generation. The results indicate that ablation can be controlled by varying the viscosity of liquid propellant in laser plasma propulsion

Optical properties of Germanium nanoparticles synthesized by pulsed laser ablation in acetone

Directory of Open Access Journals (Sweden)

Saikiran eVadavalli

2014-10-01

Full Text Available Germanium (Ge nanoparticles (NPs are synthesized by means of pulsed laser ablation of bulk germanium target immersed in acetone with ns laser pulses at different pulse energies. The fabricated NPs are characterized by employing different techniques such as UV-visible absorption spectroscopy, photoluminescence, micro-Raman spectroscopy, transmission electron microscopy (TEM and field emission scanning electron microscopy (FESEM. The mean size of the Ge NPs is found to vary from few nm to 40 nm with the increase in laser pulse energy. Shift in the position of the absorption spectra is observed and also the photoluminescence peak shift is observed due to quantum confinement effects. High resolution TEM combined with micro-Raman spectroscopy confirms the crystalline nature of the generated germanium nanoparticles. The formation of various sizes of germanium NPs at different laser pulse energies is evident from the asymmetry in the Raman spectra and the shift in its peak position towards the lower wavenumber side. The FESEM micrographs confirm the formation of germanium micro/nanostructures at the laser ablated position of the bulk germanium. In particular, the measured NP sizes from the micro-Raman phonon quantum confinement model are found in good agreement with TEM measurements of Ge NPs.

Identification of photoacoustic transients during pulsed laser ablation of the human temporal bone: an experimental model.

Science.gov (United States)

Wong, B J; Dickinson, M R; Berns, M W; Neev, J

1996-12-01

Laser ablation of hard tissues during neurotologic operations has been accomplished with continuous-wave (CW) lasers in the visible and midinfrared spectrum. The mechanism of ablation at these wavelengths is secondary to photothermal-induced tissue destruction. As a result, significant thermal damage to surrounding tissue may occur. Pulsed ultraviolet (UV) lasers have been suggested as an alternative to the argon, KTP-532, and CO2 lasers currently used in clinical practice. The pulse length of Excimer lasers are considerably shorter than the thermal diffusion time of bone tissue, and as a consequence thermal injury is minimal. This makes pulsed lasers an attractive tool for tissue ablation in the ear: in essence a "cold knife." However, the short pulse width of Excimer lasers (typically 10-150 ns) can create large thermoelastic stresses in the ablation specimen. This study identifies the presence of these photoacoustic waves during the Excimer laser treatment of the cadaveric human temporal bone. A XeCl (lambda = 308 nm, tau p = 12 ns) excimer laser was used to ablate hard tissue surrounding the oval window and facial ridge with energies of 75, 45, 25, and 12 mJ/pulse. Spot size was estimated to be 0.5 mm2. Custom high-frequency polyvinyldifluoride (PVDF) piezoelectric film transducers were fabricated and attached to the promontory, round window niche, and facial ridges. The signals were amplified using a low-noise preamplifier and recorded on a digitizing oscilloscope. Photoacoustic waves were clearly identified. Notably, large acoustic waves were measured on the promontory and on both sides of the facial ridge. The implications and clinical relevance of these findings is discussed and compared to findings obtained from a model system.

Temperature response of biological materials to pulsed non-ablative CO2 laser irradiation

NARCIS (Netherlands)

Brugmans, M. J.; Kemper, J.; Gijsbers, G. H.; van der Meulen, F. W.; van Gemert, M. J.

1991-01-01

This paper presents surface temperature responses of various tissue phantoms and in vitro and in vivo biological materials in air to non-ablative pulsed CO2 laser irradiation, measured with a thermocamera. We studied cooling off behavior of the materials after a laser pulse, to come to an

Pulsed laser ablation and deposition of niobium carbide

International Nuclear Information System (INIS)

Sansone, M.; De Bonis, A.; Santagata, A.; Rau, J.V.; Galasso, A.; Teghil, R.

2016-01-01

Highlights: • We have deposited in vacuum niobium carbide films by fs and ns PLD. • We have compared PLD performed by ultra-short and short laser pulses. • The films deposited by fs PLD of NbC are formed by nanoparticles. • The structure of the films produced by fs PLD at 500 °C corresponds to NbC. - Abstract: NbC crystalline films have been deposited in vacuum by ultra-short pulsed laser deposition technique. The films have been characterized by transmission and scanning electron microscopies and by X-ray diffraction. To clarify the ablation–deposition mechanism, the plasma produced by the ablation process has been characterized by optical emission spectroscopy and fast imaging. A comparison of the results with those obtained by ns pulsed deposition of the same target has been carried out.

Ultra-short laser pulse ablation using shear-force feedback: Femtosecond laser induced breakdown spectroscopy feasibility study

International Nuclear Information System (INIS)

Samek, Ota; Kurowski, Andre; Kittel, Silke; Kukhlevsky, Sergei; Hergenroeder, Roland

2005-01-01

This work reports on a feasibility study of proximity ablation using femtosecond pulses. Ultra-short pulses were launched to a bare tapered optical fiber and delivered to the sample. The tip-sample distance was controlled by means of shear-force feedback. Consequently, ablation craters with submicrometer dimensions were obtained. Potential analytical applications for Laser Induced Breakdown Spectroscopy (LIBS) technique, such as e.g. inclusions in steel or bio cells, are suggested

Investigation of different liquid media and ablation times on pulsed laser ablation synthesis of aluminum nanoparticles

International Nuclear Information System (INIS)

Baladi, Arash; Sarraf Mamoory, Rasoul

2010-01-01

Aluminum nanoparticles were synthesized by pulsed laser ablation of Al targets in ethanol, acetone, and ethylene glycol. Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) images, Particle size distribution diagram from Laser Particle Size Analyzer (LPSA), UV-visible absorption spectra, and weight changes of targets were used for the characterization and comparison of products. The experiments demonstrated that ablation efficiency in ethylene glycol is too low, in ethanol is higher, and in acetone is highest. Comparison between ethanol and acetone clarified that acetone medium leads to finer nanoparticles (mean diameter of 30 nm) with narrower size distribution (from 10 to 100 nm). However, thin carbon layer coats some of them, which was not observed in ethanol medium. It was also revealed that higher ablation time resulted in higher ablated mass, but lower ablation rate. Finer nanoparticles, moreover, were synthesized in higher ablation times.

Investigation of different liquid media and ablation times on pulsed laser ablation synthesis of aluminum nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Baladi, Arash [Materials Engineering Department, Tarbiat Modares University, Jalal Al Ahmad, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Sarraf Mamoory, Rasoul, E-mail: rsarrafm@modares.ac.ir [Materials Engineering Department, Tarbiat Modares University, Jalal Al Ahmad, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of)

2010-10-01

Aluminum nanoparticles were synthesized by pulsed laser ablation of Al targets in ethanol, acetone, and ethylene glycol. Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) images, Particle size distribution diagram from Laser Particle Size Analyzer (LPSA), UV-visible absorption spectra, and weight changes of targets were used for the characterization and comparison of products. The experiments demonstrated that ablation efficiency in ethylene glycol is too low, in ethanol is higher, and in acetone is highest. Comparison between ethanol and acetone clarified that acetone medium leads to finer nanoparticles (mean diameter of 30 nm) with narrower size distribution (from 10 to 100 nm). However, thin carbon layer coats some of them, which was not observed in ethanol medium. It was also revealed that higher ablation time resulted in higher ablated mass, but lower ablation rate. Finer nanoparticles, moreover, were synthesized in higher ablation times.

On the angular dependence of focused laser ablation by nanosecond pulses in solgel and polymer materials

Science.gov (United States)

George, D. S.; Onischenko, A.; Holmes, A. S.

2004-03-01

Focused laser ablation by single laser pulses at varying angles of incidence is studied in two materials of interest: a solgel (Ormocer 4) and a polymer (SU8). For a range of angles (up to 70° from normal), and for low-energy (<20 μJ), 40 ns pulses at 266 nm wavelength, the ablation depth along the direction of the incident laser beam is found to be independent of the angle of incidence. This allows the crater profiles at oblique incidence to be generated directly from the crater profiles at normal incidence by a simple coordinate transformation. This result is of use in the development of simulation tools for direct-write laser ablation. A simple model based on the moving ablation front approach is shown to be consistent with the observed behavior.

Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation

Science.gov (United States)

Kim, Beop-Min; Feit, Michael D.; Rubenchik, Alexander M.; Gold, David M.; Darrow, Christopher B.; Marion, John E., II; Da Silva, Luiz B.

1998-05-01

Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using an ultrashort pulse laser. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so bone tissue is selectively ablated while preserving the spinal cord.

Boundary conditions for 3D dynamic models of ablation of ceramics by pulsed mid-infrared lasers

Energy Technology Data Exchange (ETDEWEB)

Vila Verde, A. [Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Ramos, Marta M.D. [Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal)]. E-mail: marta@fisica.uminho.pt

2005-07-15

We present and discuss a set of boundary conditions (BCs) to use in three-dimensional, mesoscopic, finite element models of mid-infrared pulsed laser ablation of brittle materials. These models allow the study of the transient displacement and stress fields generated at micrometer scales during and after one laser pulse, where using conventional BCs may lead to some results without physical significance that can be considered an artefact of the calculations. The proposed BCs are tested and applied to a micrometer-scale continuous model of human dental enamel under CO{sub 2} radiation (10.6 {mu}m, 0.35 {mu}s pulse, sub-ablative fluence), giving rise to the following results: the highest stress is obtained at the irradiated surface of the model, at the end of the laser pulse, but afterwards it decreases rapidly until it becomes significantly lower than the stress in a region 2.5 {mu}m deep in the model; a thermally induced vibration in the material is predicted. This non-intuitive dynamics in stress and displacement distribution cannot be neglected and has to be considered in dynamic laser ablation models, since it may have serious implications in the mechanisms of ablation.

Selective ablation of dental enamel and dentin using femtosecond laser pulses

International Nuclear Information System (INIS)

Lizarelli, R F Z; Costa, M M; Carvalho-Filho, E; Bagnato, V S; Nunes, F D

2008-01-01

The study of the interaction of intense laser light with matter, as well as transient response of atoms and molecules is very appropriated because of the laser energy concentration in a femtosecond optical pulses. The fundamental problem to be solved is to find tools and techniques which allow us to observe and manipulate on a femtosecond time scale the photonics events on and into the matter. Six third human extracted molars were exposed to a femtosecond Ti:Sapphire Q-switched and mode locked laser (Libra-S, Coherent, Palo Alto, CA, USA), emitting pulses with 70 fs width, radiation wavelength of 801 nm, at a constant pulse repetition rate of 1 KHz. The laser was operated at different power levels (70 to 400 mW) with constant exposition time of 10 seconds, at focused and defocused mode. Enamel and dentin surfaces were evaluated concerned ablation rate and morphological aspects under scanning electron microscopic. The results in this present experiment suggest that at the focused mode and under higher average power, enamel tissues present microcavities with higher depth and very precise edges, but, while dentin shows a larger melt-flushing, lower depth and melting and solidification aspect. In conclusion, it is possible to choose hard or soft ablation, under lower and higher average power, respectively, revealing different aspects of dental enamel and dentin, depending on the average power, fluence and distance from the focal point of the ultra-short pulse laser on the tooth surface

Nanosecond pulsed laser ablation of brass in a dry and liquid-confined environment

Science.gov (United States)

Bashir, Shazia; Vaheed, Hamza; Mahmood, Khaliq

2013-02-01

The effect of ambient environment (dry or wet) and overlapping laser pulses on the laser ablation performance of brass has been investigated. For this purpose, a Q-switched, frequency doubled Nd:YAG laser with a wavelength of 532 nm, pulse energy of 150 mJ, pulse width of 6 ns and repetition rate of 10 Hz is employed. In order to explore the effect of ambient environments, brass targets have been exposed in deionized water, methanol and air. The targets are exposed for 1000, 2000, 3000 and 4000 succeeding pulses in each atmosphere. The surface morphology and chemical composition of ablated targets have been characterized by using Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM) and Attenuated Total Reflection (ATR) techniques. In case of liquid environment, various features like nano- and micro-scale laser-induced periodic surface structures with periodicity 500 nm-1 μm, cavities of size few micrometers with multiple ablative layers and phenomenon of thermal stress cracking are observed. These features are originated by various chemical and thermal phenomena induced by laser heating at the liquid-solid interfaces. The convective bubble motion, explosive boiling, pressure gradients, cluster and colloid formation due to confinement effects of liquids are possible cause for such kind of features. The metal oxides and alcohol formed on irradiated surface are also playing the significant role for the formation of these kinds of structure. In case of air one huge crater is formed along with the redeposition of sputtered material and is ascribed to laser-induced evaporation and oxide formation.

Improving adhesion of copper/epoxy joints by pulsed laser ablation

KAUST Repository

Hernandez, Edwin

2015-10-19

The purpose of the present work is to analyze the effect of pulsed laser ablation on copper substrates (CuZn40) deployed for adhesive bonding. Surface pre-treatment was carried using an Yb-fiber laser beam. Treated surfaces were probed using Scanning Electron Microscopy (SEM) and X-Ray Photoelectron Spectroscopy (XPS). The mechanical performance of CuZn40/epoxy bonded joints was assessed using the T-peel test coupon. In order to resolve the mechanisms of failure and adhesive penetration within surface asperities induced by the laser treatment, fracture surfaces were surveyed using SEM. Finite element simulations, based on the use of the cohesive zone model of fracture, were carried out to evaluate the variation of bond toughness. Results indicated that the laser ablation process effectively modifies surface morphology and chemistry and enables enhanced mechanical interlocking and cohesive failure within the adhesive layer. Remarkable improvements of apparent peel energy and bond toughness were observed with respect to control samples with sanded substrates.

Improving adhesion of copper/epoxy joints by pulsed laser ablation

KAUST Repository

Hernandez, Edwin; Alfano, Marco; Lubineau, Gilles; Buttner, Ulrich

2015-01-01

The purpose of the present work is to analyze the effect of pulsed laser ablation on copper substrates (CuZn40) deployed for adhesive bonding. Surface pre-treatment was carried using an Yb-fiber laser beam. Treated surfaces were probed using Scanning Electron Microscopy (SEM) and X-Ray Photoelectron Spectroscopy (XPS). The mechanical performance of CuZn40/epoxy bonded joints was assessed using the T-peel test coupon. In order to resolve the mechanisms of failure and adhesive penetration within surface asperities induced by the laser treatment, fracture surfaces were surveyed using SEM. Finite element simulations, based on the use of the cohesive zone model of fracture, were carried out to evaluate the variation of bond toughness. Results indicated that the laser ablation process effectively modifies surface morphology and chemistry and enables enhanced mechanical interlocking and cohesive failure within the adhesive layer. Remarkable improvements of apparent peel energy and bond toughness were observed with respect to control samples with sanded substrates.

Effect of dry and wet ambient environment on the pulsed laser ablation of titanium

International Nuclear Information System (INIS)

Ali, Nisar; Bashir, Shazia; Umm-i-Kalsoom,; Akram, Mahreen; Mahmood, Khaliq

2013-01-01

Surface and structural properties of the laser irradiated titanium targets have been investigated under dry and wet ambient environments. For this purpose KrF Excimer laser of wavelength 248 nm, pulse duration of 20 ns and repetition rate of 20 Hz has been employed. The targets were exposed for various number of laser pulses ranging from 500 to 2000 in the ambient environment of air, de-ionized water and propanol at a fluence of 3.6 J/cm 2 . The surface morphology, chemical composition and crystallographical analysis were performed by using Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD), respectively. For both central and peripheral ablated areas, significant difference in surface morphology has been observed in case of dry and wet ambient conditions. Large sized and diffused grains are observed in case of dry ablation. Whereas, in case of wet ablation, small sized, and well defined grains with distinct grain boundaries and significantly enhanced density are revealed. This difference is ascribed to the confinement effects of the liquid. The peripheral ablated area shows redeposition in case of dry ablation whereas small sized grain like structures are formed in case of wet ablation. EDS analysis exhibits variation in chemical composition under both ambient conditions. When the targets are treated in air environment, enhancement of the oxygen as well as nitrogen content is observed while in case of de-ionized water and propanol only increase in content of oxygen is observed. X-ray diffraction analysis exhibits formation of oxides and nitrides in case of air, whereas, in case of de-ionized water and propanol only oxides along with hydrides are formed. For various number of laser pulses the variation in the peak intensity, crystallinity and d-spacing is observed under both ambient conditions.

Study on the ablation threshold induced by pulsed lasers at different wavelengths

International Nuclear Information System (INIS)

Torrisi, L.; Borrielli, A.; Margarone, D.

2007-01-01

A study of the effects induced by pulsed laser ablation on different materials as a function of the laser wavelength is presented. In particular the ablation at low laser fluence, of the order of 10 8 -10 10 W/cm 2 with ns pulse width, is investigated experimentally on different metals, semiconductors and polymers. Two theoretical models, explain the experimental results about the fluence threshold value measurements, as depending on the laser wavelength are discussed. The photothermal process is valid for the estimation of the threshold fluence for IR and visible radiation, both inducing thermal heating in metals and semiconductors through the photon-free electron energy transfer. This model is not valid for polymers. The photochemical process is valid for the estimation of the threshold fluence for UV radiation, which photon energy is higher with respect to the chemical binding energy. This radiation induces chemical bond breaking in insulators and scission and cross linking effects can be produced. This last model is not valid for metals and semiconductors

Ablation spot area and impulse characteristics of polymers induced by burst irradiation of 1 μm laser pulses

Science.gov (United States)

Tsuruta, Hisashi; Dondelewski, Oskar; Katagiri, Yusuke; Wang, Bin; Sasoh, Akihiro

2017-07-01

The ablation spot area and impulse characteristics of various polymers were experimentally investigated against burst irradiation of Nd: YLF laser pulses with a pulse repetition frequency of 1 kHz, wavelength of 1047 nm, temporal pulse width of 10 ns, and single-pulse fluence of 6.1 J/cm2 to 17.1 J/cm2. The dependences of ablation area on the pulse energy from 0.72 to 7.48 mJ and the number of pulses from 10 pulses to 1000 pulses were investigated. In order to characterize their impulse performance as a function of fluence, which should not depend on ablation material, an effective ablation spot area was defined as that obtained against aluminum, 1050 A, as the reference material. An impulse that resulted from a single burst of 200 pulses was measured with a torsion-type impulse stand. Various impulse dependences on the fluence, which were not readily predicted from the optical properties of the material without ablation, were obtained. By fitting the experimentally measured impulse performance to Phipps and Sinko's model in the vapor regime, the effective absorption coefficient with laser ablation was evaluated, thereby resulting in three to six orders of magnitude larger than that without ablation. Among the polymers examined using polytetrafluoroethylene (PTFE) as the best volume absorbers, the highest momentum coupling coefficient of 66 μNs/J was obtained with an effective absorption coefficient more than six times smaller than that of the other polymers.

Femtosecond laser ablation and cutting technology on PMP foam

International Nuclear Information System (INIS)

Song Chengwei; Li Guo; Huang Yanhua; Du Kai; Yang Liang

2013-01-01

The femtosecond laser ablation results of PMP foam (density of 90 mg/cm 3 ) were analyzed. The laser pulses used for the study were 800 nm in wavelength, 50 fs in pulse duration and the repetition rate was 1000 Hz. The ablation threshold of the foam was 0.91 J/cm 2 when it was shot by 100 laser pulses. The impacts of laser power, the pulse number and the numerical aperture of the focusing objective on the crater diameter were obtained. In the same femtosecond laser machining system, comparing with the ablation shape into copper foil, the important factor causing the irregular shape of the ablation region was verified that there were many different sizes and randomly distributed pores inside PMP foam. The carbonation phenomenon was observed on the edge of the ablated areas when the sample was ablated using high laser power or/and more laser pulses. Thermal effect was considered to be the causes of the carbonation. A new method based on coupling laser beam to cut thickness greater than 1 mm film-foam with femtosecond laser was proposed. Using this method, the femtosecond laser cutting thickness was greater than 1.5 mm, the angle between the cutting side wall and the laser beam optical axis might be less than 5°, and the cutting surface was clean. (authors)

Wavelength dependence of the single pulse femtosecond laser ablation threshold of indium phosphide in the 400-2050 nm range

International Nuclear Information System (INIS)

Borowiec, A.; Tiedje, H.F.; Haugen, H.K.

2005-01-01

We present single pulse femtosecond laser ablation threshold measurements of InP obtained by optical, scanning electron, and atomic force microscopy. The experiments were conducted with laser pulses 65-175 fs in duration, in the wavelength range from 400 to 2050 nm, covering the photon energy region above and below the bandgap of InP. The ablation thresholds determined from depth and volume measurements varied from 87 mJ/cm 2 at 400 nm to 250 mJ/cm 2 at 2050 nm. In addition, crater depths and volumes were measured over a range of laser fluences extending well above the ablation threshold

Time resolved optical emission spectroscopy of cross-beam pulsed laser ablation on graphite targets

International Nuclear Information System (INIS)

Sangines, R.; Sanchez Ake, C.; Sobral, H.; Villagran-Muniz, M.

2007-01-01

Cross-beam pulsed laser ablation with two delayed lasers is performed on two perpendicular graphite targets. The time delay between lasers is varied by up to 5 μs, and physical changes on the second plasma, due to the interaction with the first generated one, are determined by time resolved optical emission spectroscopy

Femtosecond laser ablation of dentin

International Nuclear Information System (INIS)

Alves, S; Vilar, R; Oliveira, V

2012-01-01

The surface morphology, structure and composition of human dentin treated with a femtosecond infrared laser (pulse duration 500 fs, wavelength 1030 nm, fluences ranging from 1 to 3 J cm -2 ) was studied by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The average dentin ablation threshold under these conditions was 0.6 ± 0.2 J cm -2 and the ablation rate achieved in the range 1 to 2 µm/pulse for an average fluence of 3 J cm -2 . The ablation surfaces present an irregular and rugged appearance, with no significant traces of melting, deformation, cracking or carbonization. The smear layer was entirely removed by the laser treatment. For fluences only slightly higher than the ablation threshold the morphology of the laser-treated surfaces was very similar to the dentin fracture surfaces and the dentinal tubules remained open. For higher fluences, the surface was more porous and the dentin structure was partially concealed by ablation debris and a few resolidified droplets. Independently on the laser processing parameters and laser processing method used no sub-superficial cracking was observed. The dentin constitution and chemical composition was not significantly modified by the laser treatment in the processing parameter range used. In particular, the organic matter is not preferentially removed from the surface and no traces of high temperature phosphates, such as the β-tricalcium phosphate, were observed. The achieved results are compatible with an electrostatic ablation mechanism. In conclusion, the high beam quality and short pulse duration of the ultrafast laser used should allow the accurate preparation of cavities, with negligible damage of the underlying material. (paper)

Spectroscopic studies on diamond like carbon films synthesized by pulsed laser ablation

Energy Technology Data Exchange (ETDEWEB)

Panda, Madhusmita; Krishnan, R., E-mail: krish@igcar.gov.in; Ravindran, T. R.; Das, Arindam; Mangamma, G.; Dash, S.; Tyagi, A. K. [Material Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam - 603102, Tamil Nadu (India)

2016-05-23

Hydrogen free Diamond like Carbon (DLC) thin films enriched with C-C sp{sup 3} bonding were grown on Si (111) substrates at laser pulse energies varying from 100 to 400 mJ (DLC-100, DLC-200, DLC-300, DLC-400), by Pulsed Laser Ablation (PLA) utilizing an Nd:YAG laser operating at fundamental wavelength. Structural, optical and morphological evolutions as a function of laser pulse energy were studied by micro Raman, UV-Vis spectroscopic studies and Atomic Force Microscopy (AFM), respectively. Raman spectra analysis provided critical clues for the variation in sp{sup 3} content and optical energy gap. The sp{sup 3} content was estimated using the FWHM of the G peak and found to be in the range of 62-69%. The trend of evolution of sp{sup 3} content matches well with the evolution of I{sub D}/I{sub G} ratio with pulse energy. UV-Vis absorption study of DLC films revealed the variation of optical energy gap with laser pulse energy (1.88 – 2.23 eV), which matches well with the evolution of G-Peak position of the Raman spectra. AFM study revealed that roughness, size and density of particulate in DLC films increase with laser pulse energy.

Growth of epitaxial thin films by pulsed laser ablation

International Nuclear Information System (INIS)

Lowndes, D.H.

1992-01-01

High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs

Synthesis of Uranium-di-Oxide nano-particles by pulsed laser ablation in ethanol and their characterisation

International Nuclear Information System (INIS)

Kumar, Aniruddha; Prasad, Manisha; Shail, Shailini

2015-01-01

The importance of actinide based nano-structures is well known in the area of biology, nuclear medicine, and nuclear industry. Pulsed laser ablation in liquid is recognised as an attractive technique for production of nano-structures of different metals and metal oxides with high purity. In this paper, we report synthesis of uranium-di-oxide nano particles by pulsed laser ablation in ethanol. The second harmonic emission of an electro- optically Q-switched nano-second Nd-YAG laser was used as the coherent source here. The structural and optical properties of the fabricated Uranium-di-oxide nano- particles were investigated by XRD, SEM, TEM, EDX and UV- Vis-NIR spectrophotometry. The mean size of the particles was found to be dependent on the laser ablation parameters. XRD and TEM analysis confirmed the phase of the synthesised material as pure crystalline Uranium-di- oxide with Face Centred Cubic structure. UV- Vis- NIR absorption spectra of the colloidal solution show high absorption in the UV regime. (author)

Femtosecond laser ablation and nanoparticle formation in intermetallic NiAl

Energy Technology Data Exchange (ETDEWEB)

Jorgensen, David J., E-mail: davidjjorgensen@engr.ucsb.edu; Titus, Michael S.; Pollock, Tresa M.

2015-10-30

Highlights: • The single-pulse fs laser ablation threshold of NiAl is 83 mJ/cm{sup 2}. • The transition between low- and high-fluence ablation regimes is 2.8 J/cm{sup 2}. • A bimodal size distribution of nanoparticles is formed with fs laser ablation. • Smaller nanoparticles are enriched in Al during pulsed fs laser ablation. • The target surface is depleted in Al during pulsed fs laser ablation. - Abstract: The ablation behavior of a stoichiometric intermetallic compound β-NiAl subjected to femtosecond laser pulsing in air has been investigated. The single-pulse ablation threshold for NiAl was determined to be 83 ± 4 mJ/cm{sup 2} and the transition to the high-fluence ablation regime occurred at 2.8 ± 0.3 J/cm{sup 2}. Two sizes of nanoparticles consisting of Al, NiAl, Ni{sub 3}Al and NiO were formed and ejected from the target during high-fluence ablation. Chemical analysis revealed that smaller nanoparticles (1–30 nm) tended to be rich in Al while larger nanoparticles (>100 nm) were lean in Al. Ablation in the low-fluence regime maintained this trend. Redeposited material and nanoparticles remaining on the surface after a single 3.7 J/cm{sup 2} pulse, one hundred 1.7 J/cm{sup 2} pulses, or one thousand 250 mJ/cm{sup 2} pulses were enriched in Al relative to the bulk target composition. Further, the surface of the irradiated high-fluence region was depleted in Al indicating that the fs laser ablation removal rate of the intermetallic constituents in this regime does not scale with the individual pure element ablation thresholds.

Combination of Q-switched and quasi long-pulsed 1064-nm Nd:YAG laser, non-ablative 1450-nm diode laser, and ablative 10 600-nm carbon dioxide fractional laser for enlarged pores.

Science.gov (United States)

Cho, Sung Bin; Noh, Seongmin; Lee, Sang Ju; Kang, Jin Moon; Kim, Young Koo; Lee, Ju Hee

2010-07-01

Currently, there is no gold standard for the treatment of enlarged facial pores. In this report, we describe a patient with enlarged nasal pores which were treated with a combination of a non-ablative 1450-nm diode laser, a Q-switched and quasi long-pulsed 1064-nm Nd:YAG laser, and an ablative 10 600-nm carbon dioxide fractional laser system. Four months after the final treatment, the condition of the patient's pores had markedly improved, and the patient was satisfied with the results.

TiO{sub 2} nanoparticles obtained by laser ablation in water: Influence of pulse energy and duration on the crystalline phase

Energy Technology Data Exchange (ETDEWEB)

Giorgetti, E., E-mail: emilia.giorgetti@fi.isc.cnr.it [Istituto dei Sistemi Complessi (ISC) CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Muniz Miranda, M.; Caporali, S. [Dipartimento di Chimica “Ugo Schiff”, Università di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino (Italy); Canton, P. [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari, Via Torino, 30170 Venezia-Mestre (Italy); Marsili, P. [Istituto dei Sistemi Complessi (ISC) CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Dipartimento di Fisica, Università di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa (Italy); Vergari, C.; Giammanco, F. [Dipartimento di Fisica, Università di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa (Italy)

2015-09-15

Highlights: • Laser ablation of Ti in water at 1064 nm and comparison of ns and ps temporal regimes. • Structural and spectroscopic characterization of the colloids: TiO{sub 2} is the predominant phase. • Determination of an energy window where ps ablation produces more anatase than rutile. • Modelling of the experimental dependence of anatase/rutile yield on pulse length and energy. - Abstract: We fabricated Ti oxide nanoparticles by laser ablation of a Ti target in doubly deionized water with ps or ns pulses at a laser wavelength of 1064 nm. Electron microscopy, Raman, X-ray diffraction and X-ray photoelectron spectroscopy showed that, while with ns pulses the dominant oxide phase is rutile, with ps pulses anatase is the most abundant form in an intermediate energy window centered around 25 mJ per pulse. This experimental behavior can be described by a theoretical model which calculates the pressure and temperature evolution of the ablated material and, from this, the rutile and anatase yield.

Influence of the shielding effect on the formation of a micro-texture on the cermet with nanosecond pulsed laser ablation.

Science.gov (United States)

Yuan, Jiandong; Liang, Liang; Jiang, Lelun; Liu, Xin

2018-04-01

The degree of laser pulse overlapping in a laser scanning path has a significant impact on the ablation regime in the laser machining of a micro-texture. In this Letter, a nanosecond pulsed laser is used to prepare the micro-scaled groove on WC-8Co cermet under different scanning speeds. It is observed that as the scanning speed increases, the ablated trace morphology in the first scanning pass transits from a succession of intermittent deep dimples to the consecutive overlapped shallow pits. The test result also indicates that ablated trace morphology with respect to the low scanning speed stems from a plume shielding effect. Moreover, the ablation regime considering the shielding effect in micro-groove formation process is clarified. The critical scanning speed that can circumvent the shielding effect is also summarized with respect to different laser powers.

Spot size and pulse number dependence of femtosecond laser ablation thresholds of silicon and stainless steel

Energy Technology Data Exchange (ETDEWEB)

Armbruster, Oskar; Naghilou, Aida [University of Vienna, Department of Physical Chemistry, Währinger Straße 42, A-1090 Vienna (Austria); Kitzler, Markus [TU Wien, Photonics Institute, Gusshausstraße 27-29, A-1040 Vienna (Austria); Kautek, Wolfgang, E-mail: wolfgang.kautek@univie.ac.at [University of Vienna, Department of Physical Chemistry, Währinger Straße 42, A-1090 Vienna (Austria)

2017-02-28

Highlights: • Influence of laser spot size and pulse number on the ablation of solids. • An extended defect model describes the dependence of the threshold fluence on the basis of high and low density defects. • Successfully applied to silicon and stainless steel. - Abstract: Laser spot size and pulse number are two major parameters influencing the ablation of solids. The extended defect model describes the dependence of the threshold fluence on the basis of high and low density defects. This model was successfully applied to silicon and stainless steel. It is demonstrated that heat accumulation cannot describe the experimental results.

Studies on perovskite film ablation and scribing with ns-, ps- and fs-laser pulses

Science.gov (United States)

Bayer, Lukas; Ye, Xinyuan; Lorenz, Pierre; Zimmer, Klaus

2017-10-01

Hybrid organic-inorganic perovskites attract much attention due to their exceptional optoelectronic properties, in particular for photovoltaic (PV) applications. The accurate, high-speed and reliable patterning of the PV films is required for perovskite solar modules fabrication. Laser scribing provides these characteristics needed for industrial fabrication processes. In this work, the laser ablation and scribing of perovskite layers (CH3NH3PbI3: MAPbI3) with different laser sources (ns-, ps-, fs-laser pulses with wavelengths of 248 nm to 2.5 µm) were systematically investigated. The perovskite material was irradiated from both the film side and the substrate (rear side) side to study and compare the particular processes. The patterning results of the perovskite film can be classified into (1) regular laser ablation, (2) thin-film delamination lift-off process, and (3) lift-off with thermal modifications. A particular process, the localised lift-off of single grains from the perovskite film, has been observed and is discussed in relation to the thin-film lift-off process. Ablation and ablation-related mechanisms provide good conditions for laser scribing of the perovskite layer required for module interconnection via P2.

Appearance property and mechanism of plume produced by pulsed ultraviolet laser ablating copper

International Nuclear Information System (INIS)

Huang Qingju; Li Fuquan; Wang Honghua

2008-01-01

Time-resolved measurements of plume emission spectra by pulsed ultraviolet laser ablating copper in neon were analyzed, and the photographs of plume from laser ablating copper were taken. The experimental results show that plume has different colours in different ranges. At low pressure the centre layer and middle layer colours of plume are mixed colour, and the outer layer colours of plume are yellow and green. At middle pressure the centre layer and middle layer colours of plume are white, and the outer layer colour of plume is pea green. At high pressure the centre layer and middle layer colours of plume are white, and the outer layer colour of plume is faintness green. The plume range is pressed with the rising of ambient gas pressure, and the range colour gets thin with the rising of ambient gas pressure. The plume excitation radiation mechanism in pulsed ultraviolet laser ablating copper was discussed. The primary excitation radiation mechanism in plume is electron collision energy transfer and atom collision energy transfer at low pressure and middle pressure, and it is electrons Bremsstrahlung and recombination excitation radiation of electron and ion at high pressure. The model can be used to explain the experimental result qualitatively. (authors)

Heat generation caused by ablation of dental hard tissues with an ultrashort pulse laser (USPL) system.

Science.gov (United States)

Braun, Andreas; Krillke, Raphael Franz; Frentzen, Matthias; Bourauel, Christoph; Stark, Helmut; Schelle, Florian

2015-02-01

Heat generation during the removal of dental hard tissues may lead to a temperature increase and cause painful sensations or damage dental tissues. The aim of this study was to assess heat generation in dental hard tissues following laser ablation using an ultrashort pulse laser (USPL) system. A total of 85 specimens of dental hard tissues were used, comprising 45 specimens of human dentine evaluating a thickness of 1, 2, and 3 mm (15 samples each) and 40 specimens of human enamel with a thickness of 1 and 2 mm (20 samples each). Ablation was performed with an Nd:YVO4 laser at 1,064 nm, a pulse duration of 9 ps, and a repetition rate of 500 kHz with an average output power of 6 W. Specimens were irradiated for 0.8 s. Employing a scanner system, rectangular cavities of 1-mm edge length were generated. A temperature sensor was placed at the back of the specimens, recording the temperature during the ablation process. All measurements were made employing a heat-conductive paste without any additional cooling or spray. Heat generation during laser ablation depended on the dental hard tissue (enamel or dentine) and the thickness of the respective tissue (p dental hard tissues, heat generation has to be considered. Especially during laser ablation next to pulpal tissues, painful sensations and potential thermal injury of pulp tissue might occur.

On-the-fly depth profiling during ablation with ultrashort laser pulses: A tool for accurate micromachining and laser surgery

International Nuclear Information System (INIS)

Lausten, Rune; Balling, Peter

2001-01-01

A method for accurate depth profiling of a region subjected to ablation with ultrashort laser pulses is demonstrated. Time-gated imaging of the backscattered radiation from the ablation region is performed in a geometry, which allows the depth along a chosen axis on the sample to be determined with a single measurement. The profiling system has a spatial resolution of a few micrometers and applications are promoted by the fact that the measurement is performed with the same pulse that undertakes ablation. This also indicates that the method is inherently suited for in situ on-the-fly measurements. Copyright 2001 American Institute of Physics

Influence of the laser pulse repetition rate and scanning speed on the morphology of Ag nanostructures fabricated by pulsed laser ablation of solid target in water

Science.gov (United States)

Nikolov, A. S.; Balchev, I. I.; Nedyalkov, N. N.; Kostadinov, I. K.; Karashanova, D. B.; Atanasova, G. B.

2017-11-01

Nanostructures of noble metal were produced by pulsed laser ablation in liquid. A solid Ag target was immersed in double distilled water and a CuBr laser in a master oscillator—power amplifier configuration oscillating at 511 nm and emitting pulses with duration of 30 ns at a repetition rate of up to 20 kHz was employed to produce different colloids. The impact was studied of the laser pulse repetition rate and the beam scanning speed on the morphology of the nanostructures formed. Further, the optical extinction spectra of the colloids in the UV/VIS range were measured and used to make an indirect assessment of the changes in the shape and size distribution of the nanostructures. The transmission values in the near UV range were used to estimate the efficiency of the ablation process under the different experimental conditions implemented. A visualization of the nanostructures was made possible by transmission electron microscopy (TEM). The structure and phase composition of the nanoparticles were studied by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), while the alteration of the target surface caused by the impact of the high-repetition-rate laser illumination was investigated by X-ray photoelectron spectroscopy (XPS). The optimal conditions were determined yielding the highest efficiency in terms of amount of ablated material.

Secondary plasma formation after single pulse laser ablation underwater and its advantages for laser induced breakdown spectroscopy (LIBS).

Science.gov (United States)

Gavrilović, M R; Cvejić, M; Lazic, V; Jovićević, S

2016-06-07

In this work we present studies of spatial and temporal plasma evolution after single pulse ablation of an aluminium target in water. The laser ablation was performed using 20 ns long pulses emitted at 1064 nm. The plasma characterization was performed by fast photography, the Schlieren technique, shadowgraphy and optical emission spectroscopy. The experimental results indicate the existence of two distinct plasma stages: the first stage has a duration of approximately 500 ns from the laser pulse, and is followed by a new plasma growth starting from the crater center. The secondary plasma slowly evolves inside the growing vapor bubble, and its optical emission lasts over several tens of microseconds. Later, the hot glowing particles, trapped inside the vapor cavity, were detected during the whole cycle of the bubble, where the first collapse occurs after 475 μs from the laser pulse. Differences in the plasma properties during the two evolution phases are discussed, with an accent on the optical emission since its detection is of primary importance for LIBS. Here we demonstrate that the LIBS signal quality in single pulse excitation underwater can be greatly enhanced by detecting only the secondary plasma emission, and also by applying long acquisition gates (in the order of 10-100 μs). The presented results are of great importance for LIBS measurements inside a liquid environment, since they prove that a good analytical signal can be obtained by using nanosecond pulses from a single commercial laser source and by employing cost effective, not gated detectors.

Green synthesis of selenium nanoparticles by excimer pulsed laser ablation in water

OpenAIRE

O. Van Overschelde; G. Guisbiers; R. Snyders

2013-01-01

Pure selenium nanoparticles were successfully synthesized by Liquid Phase - Pulsed Laser Ablation (LP-PLA) in de-ionized water. Excimer laser (248 nm) operating at low fluence (F ∼ 1 J/cm2) was used to generate colloidal solutions of selenium nanoparticles. The obtained selenium nanoparticles were characterized by UV-visible spectroscopy, Raman spectroscopy, Dynamic Light Scattering, and Transmission Electron Microscopy. We describe the multi-modal size distributions generated and use the cen...

Investigation of excimer laser ablation threshold of polymers using a microphone

Energy Technology Data Exchange (ETDEWEB)

Krueger, Joerg; Niino, Hiroyuki; Yabe, Akira

2002-09-30

KrF excimer laser ablation of polyethylene terephthalate (PET), polyimide (PI) and polycarbonate (PC) in air was studied by an in situ monitoring technique using a microphone. The microphone signal generated by a short acoustic pulse represented the etch rate of laser ablation depending on the laser fluence, i.e., the ablation 'strength'. From a linear relationship between the microphone output voltage and the laser fluence, the single-pulse ablation thresholds were found to be 30 mJ cm{sup -2} for PET, 37 mJ cm{sup -2} for PI and 51 mJ cm{sup -2} for PC (20-pulses threshold). The ablation thresholds of PET and PI were not influenced by the number of pulses per spot, while PC showed an incubation phenomenon. A microphone technique provides a simple method to determine the excimer laser ablation threshold of polymer films.

Low-threshold ablation of enamel and dentin using Nd:YAG laser assisted with chromophore with different pulse shapes

Science.gov (United States)

Bonora, Stefano; Benazzato, Paolo; Stefani, Alessandro; Villoresi, Paolo

2004-05-01

Neodimium laser treatment has several drawbacks when used in the hard tissue cutting, because of the low absorption of the dental tissues at its wavelength. This investigation proved that the Nd:YAG radiation is a powerful ablation tool if it is used with the dye assisted method. Several in vitro tests on enamel and dentin were accomplished changing some laser parameters to have different pulse shapes and durations from 125μs up to 1.4ms. The importance of short time high power peaks, typical of crystal lasers, in the ablation process was investigated. The pulse shapes were analyzed by their intensity in space and time profiles. A first set of results found the optimum dye concentration be used in all the following tests. Furthermore the ablation threshold for this technique was found for each different pulse shapes and durations. A low energy ablation method was found to avoid temperature increase and surface cracks formation. In vitro temperature analysis was reported comparing the differences between no dye application laser treatment and with a dye spray applied. A strong reduction of the temperature increase was found in the dye assisted method. A discussion on the general findings and their possible clinical applications is presented.

Thin solid films deposited by pulsed laser ablating spray

International Nuclear Information System (INIS)

Song Guangle

2002-01-01

The fabricating technique of thin solid films deposited by pulsed laser ablating spray is a new technique. The background from which it came into being and the process of its evolution were briefly described. According to relative documents, basic principle of the technique was dwelt on. Based on the latest documents, the status quo, including the studying abroad and home, was discussed in detail. The advantages, shortcomings, prospect of its utility, the significance of studying as well as critic problems were summarized. Some proposal was suggested

Investigations on pulsed laser ablation of Sn at 1064 nm wavelength

Energy Technology Data Exchange (ETDEWEB)

Torrisi, L [Dipartimento di Fisica, Universita di Messina, Ctr. Papardo 31, 98166 S. Agata, Messina (Italy); Margarone, D [Dipartimento di Fisica, Universita di Messina, Ctr. Papardo 31, 98166 S. Agata, Messina (Italy)

2006-11-01

A Nd:Yag laser operating at 1064 nm, 900 mJ maximum pulse energy and 9 ns pulse duration, is employed to irradiate solid tin targets placed in a high vacuum (10{sup -7} mbar). The Sn plasma produced on the target surface is investigated with different analysis techniques, such as ion collectors, mass quadrupole spectrometry, electron microscopy and surface profilers. Measurements of ablation threshold, ablation yield, atomic and molecular emission, ion and neutral emission are reported. A time-of-flight technique is employed to calculate the velocity and the kinetic energy of the ion emission from the plasma. The angular distributions of the ejected ion species and of their kinetic energy are strongly peaked along the normal to the target surface. A valuation of the electric field generated inside the non-equilibrium plasma is given and discussed.

Ablation of CdTe with 100 μs Nd:YAG laser pulses: dependence on target preparation method

International Nuclear Information System (INIS)

Rzeszutek, J.; Savchuk, V.; Oszwaldowski, M.

2008-01-01

The results of experimental studies of the ablation of CdTe with a pulsed Nd:YAG laser (wavelength 1064 nm) performed with 100 μs pulses and repetition time of 35 Hz are presented for the pulse energy range from 0.13 to 0.25 J. The main goal is to elucidate the dependence of the ablation process on the target preparation method. The investigation of the vapour stream intensity and chemical composition and their evolution with time are performed with a quadrupole mass spectrometer synchronized with the laser pulses. These studies are performed for three kinds of targets: a target made of CdTe bulk crystal (BC target), a target made of CdTe fine powder pressed under the pressure of 700 atm (PP target), and a target made of loose CdTe powder (N-PP target). The applicability of these targets for obtaining high quality CdTe thin films is determined. The best chemical composition of the vapour stream can be obtained with the BC target. A major drawback of this target is the energetic threshold for ablation with Nd:YAG laser and resulting delay in the ablation process above the threshold. The advantage of powder targets over BC target is the lack of any ablation threshold or delay. Weaker angular dependence of the particle emission (associated with the surface roughness), if confirmed in further experiments, can be the most important advantage of PP and N-PP targets. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

KrF laser ablation of a polyethersulfone film: Effect of pulse duration on structure formation

International Nuclear Information System (INIS)

Pazokian, Hedieh; Selimis, Alexandros; Stratakis, Emmanuel; Mollabashi, Mahmoud; Barzin, Jalal; Jelvani, Saeid

2011-01-01

Polyethersulfone (PES) films were processed with KrF laser irradiation of different pulse durations (τ). Scanning electron microscopy (SEM) and Raman spectroscopy were employed for the examination of the morphology and chemical composition of the irradiated surfaces, respectively. During ablation with 500 fs and 5 ps pulses, localized deformations (beads), micro-ripple and conical structures were observed on the surface depending on the irradiation fluence (F) and the number of pulses (N). In addition, the number density of the structures is affected by the irradiation parameters (τ, F, N). Furthermore, at longer pulse durations (τ = 30 ns), conical structures appear at lower laser fluence values, which are converted into columnar structures upon irradiation at higher fluences. The Raman spectra collected from the top of the structures following irradiation at different pulse durations revealed graphitization of the ns laser treated areas, in contrast to those processed with ultra-short laser pulses.

Computational modeling of ultra-short-pulse ablation of enamel

Energy Technology Data Exchange (ETDEWEB)

London, R.A.; Bailey, D.S.; Young, D.A. [and others

1996-02-29

A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 sec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

Heating effect of substrate of pulsed laser ablation deposition technique towards the orientation of carbon microstructure

International Nuclear Information System (INIS)

Choy, L.S.; Irmawati Ramli; Noorhana Yahya; Abdul Halim Shaari

2009-01-01

Full text: Carbon thin film has been successfully deposited by second harmonic Nd:YAG pulsed laser ablation deposition, PLAD. The topology and morphology of the deposited layers was studied by scanning electron microscopy (SEM) whereas emission dispersion X-ray (EDX) was used to determine the existence of elements that constitutes the microstructure. Substrate heated at 500 degree Celsius during the laser ablation showed the most homogenous lollipop microstructure as compared to mainly pillars of microstructure ablated at lower substrate temperature. It is found that this also avoid further diffusion of carbon into catalyst in forming iron carbide. (author)

Pulsed Er:YAG- and 308 nm UV-excimer laser: an in vitro and in vivo study of skin-ablative effects

Energy Technology Data Exchange (ETDEWEB)

Kaufmann, R.; Hibst, R.

1989-01-01

Using a pulsed XeCl excimer laser (308 nm) and a pulsed Er:YAG laser (2,940 nm), we investigated skin ablation as a function of pulse number, radiant energy, and repetition rate. In vitro analysis of lesions performed in freshly excised human skin were consistent with in vivo results obtained from experiments on pig skin. Pulsed 308 nm laser radiation caused considerable nonspecific thermal tissue injury followed by an inflammatory reaction and impaired healing of lesions in vivo. These findings were especially pronounced with higher repetition rates, which would be required for efficient destruction of larger lesions. On the other hand, the 2.94 microns Er:YAG laser radiation produced clean and precise lesions with only minimal adjacent injury. In vivo skin ablation caused intraoperative bleeding with deeper penetration. The Er:YAG laser offers a promising surgical tool for careful removal of superficial epidermal lesions, if higher repetition rates, and an appropriate laser beam delivery system are available for clinical use.

Size properties of colloidal nanoparticles produced by nanosecond pulsed laser ablation and studying the effects of liquid medium and laser fluence

International Nuclear Information System (INIS)

Mahdieh, Mohammad Hossein; Fattahi, Behzad

2015-01-01

Highlights: • Colloidal aluminum- and titanium-based nanoparticles fabricated by laser ablation. • Various liquid environments and laser fluences were applied as variable parameters. • Physical characteristics of liquid medium influence ablation process and nanoparticle formation. • Size properties of prepared nanoparticles depend on liquid medium and laser fluence. • Ablation of both metals in ethanol results in nanoparticles with smaller size. - Abstract: In this paper, pulsed laser ablation method was used for synthesis of colloidal nanoparticles of aluminum and titanium targets in distilled water, ethanol, and acetone as liquid environments. Ultraviolet–visible (UV–vis) absorption spectrophotometer and scanning electron microscope (SEM) were used for characterization of produced nanoparticles. Using image processing technique and analyzing the SEM images, nanoparticles’ mean size and size distribution were achieved. The results show that liquid medium has strong effect on size properties of produced nanoparticles. From the results, it was found that ablation of both metal targets in ethanol medium leads to formation of smaller size nanoparticles with narrower size distributions. The influence of laser fluence was also investigated. According to the results, higher laser fluence produces larger mean size nanoparticles with broader size distribution

Size properties of colloidal nanoparticles produced by nanosecond pulsed laser ablation and studying the effects of liquid medium and laser fluence

Energy Technology Data Exchange (ETDEWEB)

Mahdieh, Mohammad Hossein, E-mail: mahdm@iust.ac.ir; Fattahi, Behzad

2015-02-28

Highlights: • Colloidal aluminum- and titanium-based nanoparticles fabricated by laser ablation. • Various liquid environments and laser fluences were applied as variable parameters. • Physical characteristics of liquid medium influence ablation process and nanoparticle formation. • Size properties of prepared nanoparticles depend on liquid medium and laser fluence. • Ablation of both metals in ethanol results in nanoparticles with smaller size. - Abstract: In this paper, pulsed laser ablation method was used for synthesis of colloidal nanoparticles of aluminum and titanium targets in distilled water, ethanol, and acetone as liquid environments. Ultraviolet–visible (UV–vis) absorption spectrophotometer and scanning electron microscope (SEM) were used for characterization of produced nanoparticles. Using image processing technique and analyzing the SEM images, nanoparticles’ mean size and size distribution were achieved. The results show that liquid medium has strong effect on size properties of produced nanoparticles. From the results, it was found that ablation of both metal targets in ethanol medium leads to formation of smaller size nanoparticles with narrower size distributions. The influence of laser fluence was also investigated. According to the results, higher laser fluence produces larger mean size nanoparticles with broader size distribution.

Physical mechanisms of SiNx layer structuring with ultrafast lasers by direct and confined laser ablation

International Nuclear Information System (INIS)

Rapp, S.; Heinrich, G.; Wollgarten, M.; Huber, H. P.; Schmidt, M.

2015-01-01

In the production process of silicon microelectronic devices and high efficiency silicon solar cells, local contact openings in thin dielectric layers are required. Instead of photolithography, these openings can be selectively structured with ultra-short laser pulses by confined laser ablation in a fast and efficient lift off production step. Thereby, the ultrafast laser pulse is transmitted by the dielectric layer and absorbed at the substrate surface leading to a selective layer removal in the nanosecond time domain. Thermal damage in the substrate due to absorption is an unwanted side effect. The aim of this work is to obtain a deeper understanding of the physical laser-material interaction with the goal of finding a damage-free ablation mechanism. For this, thin silicon nitride (SiN x ) layers on planar silicon (Si) wafers are processed with infrared fs-laser pulses. Two ablation types can be distinguished: The known confined ablation at fluences below 300 mJ/cm 2 and a combined partial confined and partial direct ablation at higher fluences. The partial direct ablation process is caused by nonlinear absorption in the SiN x layer in the center of the applied Gaussian shaped laser pulses. Pump-probe investigations of the central area show ultra-fast reflectivity changes typical for direct laser ablation. Transmission electron microscopy results demonstrate that the Si surface under the remaining SiN x island is not damaged by the laser ablation process. At optimized process parameters, the method of direct laser ablation could be a good candidate for damage-free selective structuring of dielectric layers on absorbing substrates

Time-resolved investigations of the non-thermal ablation process of graphite induced by femtosecond laser pulses

Energy Technology Data Exchange (ETDEWEB)

Kalupka, C., E-mail: christian.kalupka@llt.rwth-aachen.de; Finger, J. [Chair for Laser Technology LLT, RWTH Aachen University, Aachen 52074 (Germany); Reininghaus, M. [Chair for Laser Technology LLT, RWTH Aachen University, Aachen 52074 (Germany); Fraunhofer Institute for Laser Technology ILT, Steinbachstraße 15, Aachen 52074 (Germany)

2016-04-21

We report on the in-situ analysis of the ablation dynamics of the, so-called, laser induced non-thermal ablation process of graphite. A highly oriented pyrolytic graphite is excited by femtosecond laser pulses with fluences below the classic thermal ablation threshold. The ablation dynamics are investigated by axial pump-probe reflection measurements, transversal pump-probe shadowgraphy, and time-resolved transversal emission photography. The combination of the applied analysis methods allows for a continuous and detailed time-resolved observation of the non-thermal ablation dynamics from several picoseconds up to 180 ns. Formation of large, μm-sized particles takes place within the first 3.5 ns after irradiation. The following propagation of ablation products and the shock wave front are tracked by transversal shadowgraphy up to 16 ns. The comparison of ablation dynamics of different fluences by emission photography reveals thermal ablation products even for non-thermal fluences.

The influence of laser-particle interaction in laser induced breakdown spectroscopy and laser ablation inductively coupled plasma spectrometry

International Nuclear Information System (INIS)

Lindner, Helmut; Loper, Kristofer H.; Hahn, David W.; Niemax, Kay

2011-01-01

Particles produced by previous laser shots may have significant influence on the analytical signal in laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma (LA-ICP) spectrometry if they remain close to the position of laser sampling. The effects of these particles on the laser-induced breakdown event are demonstrated in several ways. LIBS-experiments were conducted in an ablation cell at atmospheric conditions in argon or air applying a dual-pulse arrangement with orthogonal pre-pulse, i.e., plasma breakdown in a gas generated by a focussed laser beam parallel and close to the sample surface followed by a delayed crossing laser pulse in orthogonal direction which actually ablates material from the sample and produces the LIBS plasma. The optical emission of the LIBS plasma as well as the absorption of the pre-pulse laser was measured. In the presence of particles in the focus of the pre-pulse laser, the plasma breakdown is affected and more energy of the pre-pulse laser is absorbed than without particles. As a result, the analyte line emission from the LIBS plasma of the second laser is enhanced. It is assumed that the enhancement is not only due to an increase of mass ablated by the second laser but also to better atomization and excitation conditions favored by a reduced gas density in the pre-pulse plasma. Higher laser pulse frequencies increase the probability of particle-laser interaction and, therefore, reduce the shot-to-shot line intensity variation as compared to lower particle loadings in the cell. Additional experiments using an aerosol chamber were performed to further quantify the laser absorption by the plasma in dependence on time both with and without the presence of particles. The overall implication of laser-particle interactions for LIBS and LA-ICP-MS/OES are discussed.

The influence of laser-particle interaction in laser induced breakdown spectroscopy and laser ablation inductively coupled plasma spectrometry

Science.gov (United States)

Lindner, Helmut; Loper, Kristofer H.; Hahn, David W.; Niemax, Kay

2011-02-01

Particles produced by previous laser shots may have significant influence on the analytical signal in laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma (LA-ICP) spectrometry if they remain close to the position of laser sampling. The effects of these particles on the laser-induced breakdown event are demonstrated in several ways. LIBS-experiments were conducted in an ablation cell at atmospheric conditions in argon or air applying a dual-pulse arrangement with orthogonal pre-pulse, i.e., plasma breakdown in a gas generated by a focussed laser beam parallel and close to the sample surface followed by a delayed crossing laser pulse in orthogonal direction which actually ablates material from the sample and produces the LIBS plasma. The optical emission of the LIBS plasma as well as the absorption of the pre-pulse laser was measured. In the presence of particles in the focus of the pre-pulse laser, the plasma breakdown is affected and more energy of the pre-pulse laser is absorbed than without particles. As a result, the analyte line emission from the LIBS plasma of the second laser is enhanced. It is assumed that the enhancement is not only due to an increase of mass ablated by the second laser but also to better atomization and excitation conditions favored by a reduced gas density in the pre-pulse plasma. Higher laser pulse frequencies increase the probability of particle-laser interaction and, therefore, reduce the shot-to-shot line intensity variation as compared to lower particle loadings in the cell. Additional experiments using an aerosol chamber were performed to further quantify the laser absorption by the plasma in dependence on time both with and without the presence of particles. The overall implication of laser-particle interactions for LIBS and LA-ICP-MS/OES are discussed.

Surface modification of biomaterials by pulsed laser ablation deposition and plasma/gamma polymerization

Science.gov (United States)

Rau, Kaustubh R.

Surface modification of stainless-steel was carried out by two different methods: pulsed laser ablation deposition (PLAD) and a combined plasma/gamma process. A potential application was the surface modification of endovascular stents, to enhance biocompatibility. The pulsed laser ablation deposition process, had not been previously reported for modifying stents and represented a unique and potentially important method for surface modification of biomaterials. Polydimethylsiloxane (PDMS) elatomer was studied using the PLAD technique. Cross- linked PDMS was deemed important because of its general use for biomedical implants and devices as well as in other fields. Furthermore, PDMS deposition using PLAD had not been previously studied and any information gained on its ablation characteristics could be important scientifically and technologically. The studies reported here showed that the deposited silicone film properties had a dependence on the laser energy density incident on the target. Smooth, hydrophobic, silicone-like films were deposited at low energy densities (100-150 mJ/cm2). At high energy densities (>200 mJ/cm2), the films had an higher oxygen content than PDMS, were hydrophilic and tended to show a more particulate morphology. It was also determined that (1)the deposited films were stable and extremely adherent to the substrate, (2)silicone deposition exhibited an `incubation effect' which led to the film properties changing with laser pulse number and (3)films deposited under high vacuum were similar to films deposited at low vacuum levels. The mechanical properties of the PLAD films were determined by nanomechanical measurements which are based on the Atomic Force Microscope (AFM). From these measurements, it was possible to determine the modulus of the films and also study their scratch resistance. Such measurement techniques represent a significant advance over current state-of-the-art thin film characterization methods. An empirical model for

Effect analysis of material properties of picosecond laser ablation for ABS/PVC

Science.gov (United States)

Tsai, Y. H.; Ho, C. Y.; Chiou, Y. J.

2017-06-01

This paper analytically investigates the picosecond laser ablation of ABS/PVC. Laser-pulsed ablation is a wellestablished tool for polymer. However the ablation mechanism of laser processing for polymer has not been thoroughly understood yet. This study utilized a thermal transport model to analyze the relationship between the ablation rate and laser fluences. This model considered the energy balance at the decomposition interface and Arrhenius law as the ablation mechanisms. The calculated variation of the ablation rate with the logarithm of the laser fluence agrees with the measured data. It is also validated in this work that the variation of the ablation rate with the logarithm of the laser fluence obeys Beer's law for low laser fluences. The effects of material properties and processing parameters on the ablation depth per pulse are also discussed for picosecond laser processing of ABS/PVC.

Ultra-fast Movies Resolve Ultra-short Pulse Laser Ablation and Bump Formation on Thin Molybdenum Films

Science.gov (United States)

Domke, Matthias; Rapp, Stephan; Huber, Heinz

For the monolithic serial interconnection of CIS thin film solar cells, 470 nm molybdenum films on glass substrates must be separated galvanically. The single pulse ablation with a 660 fs laser at a wavelength of 1053 nm is investigated in a fluence regime from 0.5 to 5.0 J/cm2. At fluences above 2.0 J/cm2 bump and jet formation can be observed that could be used for creating microstructures. For the investigation of the underlying mechanisms of the laser ablation process itself as well as of the bump or jet formation, pump probe microscopy is utilized to resolve the transient ablation behavior.

Green synthesis of selenium nanoparticles by excimer pulsed laser ablation in water

Directory of Open Access Journals (Sweden)

O. Van Overschelde

2013-10-01

Full Text Available Pure selenium nanoparticles were successfully synthesized by Liquid Phase - Pulsed Laser Ablation (LP-PLA in de-ionized water. Excimer laser (248 nm operating at low fluence (F ∼ 1 J/cm2 was used to generate colloidal solutions of selenium nanoparticles. The obtained selenium nanoparticles were characterized by UV-visible spectroscopy, Raman spectroscopy, Dynamic Light Scattering, and Transmission Electron Microscopy. We describe the multi-modal size distributions generated and use the centrifugation method to isolate the smallest nanoparticles (∼60 nm in diameter.

Spectroscopic and shadowgraphic analysis of laser induced plasmas in the orthogonal double pulse pre-ablation configuration

International Nuclear Information System (INIS)

Cristoforetti, G.; Legnaioli, S.; Pardini, L.; Palleschi, V.; Salvetti, A.; Tognoni, E.

2006-01-01

This work focuses on the study of the plumes obtained in the double pulse orthogonal Laser Induced Breakdown Spectroscopy (LIBS) in the pre-ablation configuration using both spectroscopic and shadowgraphic approaches. Single and double pulse LIBS experiments were carried out on a brass sample in air. Both the distance of the air plasma from the target surface and the interpulse delay were varied (respectively in the range 0.1-4.2 mm and up to 50 μs) revealing a significant variation of the plasma emission and of the plume-shock wave dynamical expansion in different cases. The intensity of both atomic and ionized zinc lines was measured in all the cases, allowing the calculation of the spatially averaged temperature and electron density and an estimation of the ablated mass. The line intensities and the thermodynamic parameters obtained by the spectroscopic measurements were discussed bearing in mind the dynamical expansion characteristics obtained from the shadowgraphic approach. All the data seem to be consistent with the model previously proposed for the double pulse collinear configuration where the line enhancement is mainly attributed to the ambient gas rarefaction produced by the first laser pulse, which causes a less effective shielding of the second laser pulse

Pulsed laser ablation of Germanium under vacuum and hydrogen environments at various fluences

Energy Technology Data Exchange (ETDEWEB)

Iqbal, Muhammad Hassan [Centre for Advanced Studies in Physics, Government College University, Lahore (Pakistan); Bashir, Shazia, E-mail: shaziabashir@gcu.edu.pk [Centre for Advanced Studies in Physics, Government College University, Lahore (Pakistan); Rafique, Muhammad Shahid [Department of Physics, University of Engineering and Technology, Lahore (Pakistan); Dawood, Asadullah; Akram, Mahreen; Mahmood, Khaliq; Hayat, Asma; Ahmad, Riaz; Hussain, Tousif [Centre for Advanced Studies in Physics, Government College University, Lahore (Pakistan); Mahmood, Arshad [National Institute of Laser and Optronics (NILOP), Islamabad (Pakistan)

2015-07-30

Highlights: • Germanium targets were exposed under vacuum and H{sub 2} environment by nanosecond laser pulses. • The effect of laser fluence and ambient environment has been investigated. • The surface morphology is investigated by SEM analysis. • Raman and FTIR Spectroscopy are performed to reveal structural modification. • Electrical conductivity is probed by four probe method. - Abstract: Laser fluence and ambient environment play a significant role for the formation and development of the micro/nano-structures on the laser irradiated targets. Single crystal (1 0 0) Germanium (Ge) has been ablated under two environments of vacuum (10{sup −3} Torr) and hydrogen (100 Torr) at various fluences ranging from 4.5 J cm{sup −2} to 6 J cm{sup −2}. For this purpose KrF Excimer laser with wavelength of 248 nm, pulse duration of 18 ns and repetition rate of 20 Hz has been employed. Surface morphology has been observed by Scanning Electron Microscope (SEM). Whereas, structural modification of irradiated targets was explored by Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. Electrical conductivity of the irradiated Ge is measured by four probe method. SEM analysis exhibits the formation of laser-induced periodic surface structures (LIPSS), cones and micro-bumps in both ambient environments (vacuum and hydrogen). The formation as well as development of these structures is strongly dependent upon the laser fluence and environmental conditions. The periodicity of LIPSS or ripples varies from 38 μm to 60 μm in case of vacuum whereas in case of hydrogen environment, the periodicity varies from 20 μm to 45 μm. The difference in number of ripples and periodicity as well as in shape and size of cones and bumps in vacuum and hydrogen is explained on the basis of confinement and shielding effect of plasma. FTIR spectroscopy reveals that no new bands are formed for laser ablated Ge under vacuum, whereas C−H stretching vibration band is

Nanosecond pulsed laser ablation of Ge investigated by employing photoacoustic deflection technique and SEM analysis

International Nuclear Information System (INIS)

Yaseen, Nazish; Bashir, Shazia; Shabbir, Muhammad Kaif; Jalil, Sohail Abdul; Akram, Mahreen; Hayat, Asma; Mahmood, Khaliq; Haq, Faizan-ul; Ahmad, Riaz; Hussain, Tousif

2016-01-01

Nanosecond pulsed laser ablation phenomena of single crystal Ge (100) has been investigated by employing photoacoustic deflection as well as SEM analysis techniques. Nd: YAG laser (1064 nm, 10 ns, 1–10 Hz) at various laser fluences ranging from 0.2 to 11 J cm"−"2 is employed as pump beam to ablate Ge targets. In order to evaluate in-situe ablation threshold fluence of Ge by photoacoustic deflection technique, Continuous Wave (CW) He–Ne laser (632 nm, power 10 mW) is employed as a probe beam. It travels parallel to the target surface at a distance of 3 mm and after passing through Ge plasma it causes deflection due to density gradient of acoustic waves. The deflected signal is detected by photodiode and is recorded by oscilloscope. The threshold fluence of Ge, the velocity of ablated species and the amplitude of the deflected signal are evaluated. The threshold fluence of Ge comes out to be 0.5 J cm"−"2 and is comparable with the analytical value. In order to compare the estimated value of threshold with ex-situe measurements, the quantitative analysis of laser irradiated Ge is performed by using SEM analysis. For this purpose Ge is exposed to single and multiple shots of 5, 10, 50 and 100 at various laser fluences ranging from 0.2 to 11 J cm"−"2. The threshold fluence for single and multiple shots as well as incubation coefficients are evaluated. It is observed that the value of incubation co-efficient decreases with increasing number of pulses and is therefore responsible for lowering the threshold fluence of Ge. SEM analysis also reveals the growth of various features such as porous structures, non-uniform ripples and blisters on the laser irradiated Ge. It is observed that both the fluence as well as number of laser shots plays a significant role for the growth of these structures.

Nanosecond pulsed laser ablation of Ge investigated by employing photoacoustic deflection technique and SEM analysis

Energy Technology Data Exchange (ETDEWEB)

Yaseen, Nazish; Bashir, Shazia; Shabbir, Muhammad Kaif; Jalil, Sohail Abdul; Akram, Mahreen; Hayat, Asma; Mahmood, Khaliq; Haq, Faizan-ul; Ahmad, Riaz; Hussain, Tousif

2016-06-01

Nanosecond pulsed laser ablation phenomena of single crystal Ge (100) has been investigated by employing photoacoustic deflection as well as SEM analysis techniques. Nd: YAG laser (1064 nm, 10 ns, 1–10 Hz) at various laser fluences ranging from 0.2 to 11 J cm{sup −2} is employed as pump beam to ablate Ge targets. In order to evaluate in-situe ablation threshold fluence of Ge by photoacoustic deflection technique, Continuous Wave (CW) He–Ne laser (632 nm, power 10 mW) is employed as a probe beam. It travels parallel to the target surface at a distance of 3 mm and after passing through Ge plasma it causes deflection due to density gradient of acoustic waves. The deflected signal is detected by photodiode and is recorded by oscilloscope. The threshold fluence of Ge, the velocity of ablated species and the amplitude of the deflected signal are evaluated. The threshold fluence of Ge comes out to be 0.5 J cm{sup −2} and is comparable with the analytical value. In order to compare the estimated value of threshold with ex-situe measurements, the quantitative analysis of laser irradiated Ge is performed by using SEM analysis. For this purpose Ge is exposed to single and multiple shots of 5, 10, 50 and 100 at various laser fluences ranging from 0.2 to 11 J cm{sup −2}. The threshold fluence for single and multiple shots as well as incubation coefficients are evaluated. It is observed that the value of incubation co-efficient decreases with increasing number of pulses and is therefore responsible for lowering the threshold fluence of Ge. SEM analysis also reveals the growth of various features such as porous structures, non-uniform ripples and blisters on the laser irradiated Ge. It is observed that both the fluence as well as number of laser shots plays a significant role for the growth of these structures.

Palladium nanoparticles produced by CW and pulsed laser ablation in water

Energy Technology Data Exchange (ETDEWEB)

Boutinguiza, M., E-mail: mohamed@uvigo.es [Applied Physics Department, University of Vigo EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Comesaña, R. [Materials Engineering, Applied Mechanics and Construction Department, University of Vigo, EEI, Lagoas-Marcosende, Vigo 36310 (Spain); Lusquiños, F. [Applied Physics Department, University of Vigo EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Riveiro, A. [Applied Physics Department, University of Vigo EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Centro Universitario de la Defensa, Escuela Naval Militar, Plaza de España 2, 36920 Marín (Spain); Val, J. del; Pou, J. [Applied Physics Department, University of Vigo EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain)

2014-05-01

Palladium nanoparticles are receiving important interest due to its application as catalyst. In this work Pd nanoparticles have been obtained by ablating a Pd target submerged in de-ionized using both, pulsed as well as continuous wave (CW) laser. The influence of laser parameters involved in the formation in nanoparticles has been studied. Crystalline phases, morphology and optical properties of the obtained colloidal nanoparticles were characterized by means of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and UV/vis absorption spectroscopy. The obtained colloidal suspensions consisted of pure Pd nanoparticles showing spherical shape with diameters ranging from few nanometers to 5–60 nm. The moderate irradiance delivered by the CW laser favours high production of uniform nanoparticles.

Liquid Atomization Induced by Pulse Laser Reflection underneath Liquid Surface

Science.gov (United States)

Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro; Nakahara, Motonao

2009-05-01

We observed a novel effect of pulse laser reflection at the interface between transparent materials with different refractive indices. The electric field intensity doubles when a laser beam is completely reflected from a material with a higher refractive index to a material with a lower index. This effect appreciably reduces pulse laser ablation threshold of transparent materials. We performed experiments to observe the entire ablation process for laser incidence on the water-air interface using pulse laser shadowgraphy with high-resolution film; the minimum laser fluence for laser ablation at the water-air interface was approximately 12-16 J/cm2. We confirmed that this laser ablation occurs only when the laser beam is incident on the water-air interface from water. Many slender liquid ligaments extend like a milk crown and seem to be atomized at the tip. Their detailed structures can be resolved only by pulse laser photography using high-resolution film.

Plasma dynamics from laser ablated solid lithium

Indian Academy of Sciences (India)

b; 52.25.-b; 52.70.-m. 1. Introduction. Pulsed laser ablation of a solid sample generates a dense plasma emission in the shape of ... The multichannel analyser plate of the ICCD was gated for as less as 4 ns using ... to explain the atomic collision processes [4]. .... Within duration of laser pulse, there occurs laser-solid interac-.

Ablative Laser Propulsion: An Update, Part I

International Nuclear Information System (INIS)

Pakhomov, Andrew V.; Cohen, Timothy; Lin Jun; Thompson, M. Shane; Herren, Kenneth A.

2004-01-01

This paper presents an updated review of studies on Ablative Laser Propulsion conducted by the Laser Propulsion Group (LPG) at the University of Alabama in Huntsville. In particular, we describe the newest results of our experimental study of specific impulses and coupling coefficients achieved by double-pulsed ablation of graphite, aluminum, copper and lead targets

Femtosecond laser ablation of polytetrafluoroethylene (Teflon) in ambient air

International Nuclear Information System (INIS)

Wang, Z.B.; Hong, M.H.; Lu, Y.F.; Wu, D.J.; Lan, B.; Chong, T.C.

2003-01-01

Teflon, polytetrafluorethylene (PTFE), is an important material in bioscience and medical application due to its special characteristics (bio-compatible, nonflammable, antiadhesive, and heat resistant). The advantages of ultrashort laser processing of Teflon include a minimal thermal penetration region and low processing temperatures, precision removal of material, and good-quality feature definition. In this paper, laser processing of PTFE in ambient air by a Ti:sapphire femtosecond laser (780 nm, 110 fs) is investigated. It is found that the pulse number on each irradiated surface area must be large enough for a clear edge definition and the ablated depth increases with the pulse number. The air ionization effect at high laser fluences not only degrades the ablated structures quality but also reduces the ablation efficiency. High quality microstructures are demonstrated with controlling laser fluence below a critical fluence to exclude the air ionization effect. The ablated microstructures show strong adhesion property to liquids and clear edges that are suitable for bio-implantation applications. Theoretical calculation is used to analyze the evolution of the ablated width and depth at various laser fluences

Metal processing with ultrashort laser pulses

Science.gov (United States)

Banks, Paul S.; Felt, M. D.; Komashko, Aleksey M.; Perry, Michael D.; Rubenchik, Alexander M.; Stuart, Brent C.

2000-08-01

Femtosecond laser ablation has been shown to produce well-defined cuts and holes in metals with minimal heat effect to the remaining material. Ultrashort laser pulse processing shows promise as an important technique for materials processing. We will discuss the physical effects associated with processing based experimental and modeling results. Intense ultra-short laser pulse (USLP) generates high pressures and temperatures in a subsurface layer during the pulse, which can strongly modify the absorption. We carried out simulations of USLP absorption versus material and pulse parameters. The ablation rate as function of the laser parameters has been estimated. Since every laser pulse removes only a small amount of material, a practical laser processing system must have high repetition rate. We will demonstrate that planar ablation is unstable and the initially smooth crater bottom develops a corrugated pattern after many tens of shots. The corrugation growth rate, angle of incidence and the polarization of laser electric field dependence will be discussed. In the nonlinear stage, the formation of coherent structures with scales much larger than the laser wavelength was observed. Also, there appears to be a threshold fluence above which a narrow, nearly perfectly circular channel forms after a few hundred shots. Subsequent shots deepen this channel without significantly increasing its diameter. The role of light absorption in the hole walls will be discussed.

Laser ablation for the synthesis of carbon nanotubes

Science.gov (United States)

Holloway, Brian C.; Eklund, Peter C.; Smith, Michael W.; Jordan, Kevin C.; Shinn, Michelle

2010-04-06

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Laser ablation for the synthesis of carbon nanotubes

Science.gov (United States)

Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

2012-01-01

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Effects of 532 nm pulsed-KTP laser parameters on vessel ablation in the avian chorioallantoic membrane: implications for vocal fold mucosa.

Science.gov (United States)

Broadhurst, Matthew S; Akst, Lee M; Burns, James A; Kobler, James B; Heaton, James T; Anderson, R Rox; Zeitels, Steven M

2007-02-01

Selective vascular ablation (photoangiolysis) using pulsed lasers that target hemoglobin is an effective treatment strategy for many vocal fold lesions. However, vessel rupture with extravasation of blood reduces selectivity for vessels, which is frequently observed with the 0.45-ms, 585-nm pulsed dye laser. Previous studies have shown that vessel rupture is the result of vaporization of blood, an event that varies with laser pulse width and pulse fluence (energy per unit area). Clinical observations using a 532-nm wavelength pulsed potassium-titanyl-phosphate (KTP) laser revealed less laser-induced hemorrhage than the pulsed dye laser. This study investigated settings for the pulsed KTP laser to achieve selective vessel destruction without rupture using the avian chorioallantoic membrane under conditions similar to flexible laryngoscopic delivery of the laser in clinical practice. The chick chorioallantoic membrane offers convenient access to many small blood vessels similar in size to those targeted in human vocal fold. Using a 532-nm pulsed KTP laser, pulse width, pulse energy, and working distance from the optical delivery fiber were varied to assess influence on the ability to achieve vessel coagulation without vessel wall rupture. Third-order vessels (n = 135) were irradiated: Energy (471-550 mJ), pulse width (10, 15, 30 ms), and fiber-to-tissue distance (1 mm, 3 mm) were varied systematically. Selective vessel destruction without vessel wall rupture was more often achieved by increasing pulse width, increasing the fiber-to-tissue distance, and decreasing energy. Vessel destruction without rupture was consistently achieved using 15- or 30-ms pulses with a fiber-to-tissue distance of 3 mm (pulse fluence of 13-16 J/cm). This study substantiates our clinical observation that a 532-nm pulsed KTP laser was effective for ablating microcirculation while minimizing vessel wall rupture and hemorrhage.

Structure and morphologies of ZnO nanoparticles synthesized by pulsed laser ablation in liquid: Effects of temperature and energy fluence

Energy Technology Data Exchange (ETDEWEB)

Guillén, G. García; Palma, M.I. Mendivil [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica, San Nicolás de los Garza, Nuevo León 66455 (Mexico); Krishnan, B. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica, San Nicolás de los Garza, Nuevo León 66455 (Mexico); Universidad Autónoma de Nuevo León – Centro de Innovación, Investigación y Desarrollo de Ingeniería y Tecnología, Apodaca, Nuevo León 66600 (Mexico); Avellaneda, D.; Castillo, G.A.; Roy, T.K. Das [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica, San Nicolás de los Garza, Nuevo León 66455 (Mexico); and others

2015-07-15

Zinc oxide nanoparticles were prepared by pulsed laser ablation of a zinc metal target at different water temperatures (room temperature, 50, 70 and 90 °C). Ablation was carried out using 532 nm output from a pulsed (10 ns, 10 Hz) Nd:YAG laser at three different laser fluence. Analysis of the morphology, crystalline phase, elemental composition, optical and luminescent properties were done using Transmission Electron Microscopy (TEM), X-Ray Photoelectron Spectroscopy (XPS), UV–visible absorption spectroscopy and photoluminescence spectroscopy. TEM analysis showed that a change in temperature resulted in ZnO and Zn(OH){sub 2} nanoparticles with different sizes and morphologies. XPS results confirmed the compositions and chemical states of these nanoparticles. These zinc nanomaterials showed emission in the ultraviolet (UV) and blue regions. The results of this work demonstrated that by varying the liquid medium temperature, the structure, composition, morphology and optical properties of the nanomaterials could be modified during pulsed laser ablation in liquid. - Graphical abstract: Display Omitted - Highlights: • Zinc nanomaterial colloids were synthesized by PLAL. • Effects of laser fluence and the distilled water temperature were analyzed. • The final structure varied with the distilled water temperature and laser fluence. • The morphology was dependent on the distilled water temperature and laser fluence. • Zinc nanocolloids showed emission in the UV and blue region.

Structure and morphologies of ZnO nanoparticles synthesized by pulsed laser ablation in liquid: Effects of temperature and energy fluence

International Nuclear Information System (INIS)

Guillén, G. García; Palma, M.I. Mendivil; Krishnan, B.; Avellaneda, D.; Castillo, G.A.; Roy, T.K. Das

2015-01-01

Zinc oxide nanoparticles were prepared by pulsed laser ablation of a zinc metal target at different water temperatures (room temperature, 50, 70 and 90 °C). Ablation was carried out using 532 nm output from a pulsed (10 ns, 10 Hz) Nd:YAG laser at three different laser fluence. Analysis of the morphology, crystalline phase, elemental composition, optical and luminescent properties were done using Transmission Electron Microscopy (TEM), X-Ray Photoelectron Spectroscopy (XPS), UV–visible absorption spectroscopy and photoluminescence spectroscopy. TEM analysis showed that a change in temperature resulted in ZnO and Zn(OH) 2 nanoparticles with different sizes and morphologies. XPS results confirmed the compositions and chemical states of these nanoparticles. These zinc nanomaterials showed emission in the ultraviolet (UV) and blue regions. The results of this work demonstrated that by varying the liquid medium temperature, the structure, composition, morphology and optical properties of the nanomaterials could be modified during pulsed laser ablation in liquid. - Graphical abstract: Display Omitted - Highlights: • Zinc nanomaterial colloids were synthesized by PLAL. • Effects of laser fluence and the distilled water temperature were analyzed. • The final structure varied with the distilled water temperature and laser fluence. • The morphology was dependent on the distilled water temperature and laser fluence. • Zinc nanocolloids showed emission in the UV and blue region

Investigation of the particle size distribution of the ejected material generated during the single femtosecond laser pulse ablation of aluminium

International Nuclear Information System (INIS)

Wu, Han; Zhang, Nan; Zhu, Xiaonong

2014-01-01

Highlights: • Single 50 fs laser pulse ablation of an aluminium target in vacuum is investigated in our experiments. • Nanoparticles with large radii of several hundred nanometers are observed. • The nanoparticles are most likely from the mechanical tensile stress relaxation. - Abstract: Single femtosecond laser pulses are employed to ablate an aluminium target in vacuum, and the particle size distribution of the ablated material deposited on a mica substrate is examined with atomic force microscopy (AFM). The recorded AFM images show that these particles have a mean radius of several tens of nanometres. It is also determined that the mean radius of these deposited nanoparticles increases when the laser fluence at the aluminium target increases from 0.44 J/cm 2 to 0.63 J/cm 2 . The mechanism of the laser-induced nanoparticle generation is thought to be photomechanical tensile stress relaxation. Raman spectroscopy measurements confirm that the nanoparticles thus produced have the same structure as the bulk aluminium

Drilling of Copper Using a Dual-Pulse Femtosecond Laser

Directory of Open Access Journals (Sweden)

Chung-Wei Cheng

2016-02-01

Full Text Available The drilling of copper using a dual-pulse femtosecond laser with wavelength of 800 nm, pulse duration of 120 fs and a variable pulse separation time (0.1–150 ps is investigated theoretically. A one-dimensional two-temperature model with temperature-dependent material properties is considered, including dynamic optical properties and the thermal-physical properties. Rapid phase change and phase explosion models are incorporated to simulate the material ablation process. Numerical results show that under the same total laser fluence of 4 J/cm2, a dual-pulse femtosecond laser with a pulse separation time of 30–150 ps can increase the ablation depth, compared to the single pulse. The optimum pulse separation time is 85 ps. It is also demonstrated that a dual pulse with a suitable pulse separation time for different laser fluences can enhance the ablation rate by about 1.6 times.

Hydrodynamic model for ultra-short pulse ablation of hard dental tissue

Energy Technology Data Exchange (ETDEWEB)

London, R.A.; Bailey, D.S.; Young, D.A.; Alley, W.E.; Feit, M.D.; Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Neev, J. [Beckman Laser Inst., Irvine, CA (United States)

1996-02-29

A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 fsec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

CuInGaSe{sub 2} nanoparticles by pulsed laser ablation in liquid medium

Energy Technology Data Exchange (ETDEWEB)

Mendivil, M.I.; García, L.V. [Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León, 66455 (Mexico); Krishnan, B. [Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León, 66455 (Mexico); CIIDIT—Universidad Autónoma de Nuevo León, Apodaca, Nuevo León (Mexico); Avellaneda, D. [Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León, 66455 (Mexico); and others

2015-12-15

Highlights: • CIGS nanocolloids were synthesized using PLAL technique. • Characterized their morphology, structure, composition and optical properties. • Morphologies were dependent on ablation wavelength and liquid medium. • Optical absorption and bandgap of these nanocolloids were tunable. - Abstract: Pulsed laser ablation in liquid medium (PLALM) is a nanofabrication technique to produce complex nanostructures. CuInGaSe{sub 2} (CIGS) is an alloy with applications in photovoltaic industry. In this work, we studied the effects of laser ablation wavelength, energy fluence and liquid medium on the properties of the CIGS nanoparticles synthesized by PLALM. The nanoparticles obtained were analyzed by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS) and UV–vis absorption spectroscopy. XPS results confirmed the chemical states and composition of the ablated products. TEM analysis showed different morphologies for the nanomaterials obtained in different liquid media and ablation wavelengths. The optical properties for these CIGS nanocolloids were analyzed using UV–vis absorption spectroscopy. The results demonstrated the use of PLALM as a useful synthesis technique for nanoparticles of quaternary photovoltaic materials.

Precise femtosecond laser ablation of dental hard tissue: preliminary investigation on adequate laser parameters

International Nuclear Information System (INIS)

Hikov, Todor; Pecheva, Emilia; Petrov, Todor; Montgomery, Paul; Antoni, Frederic; Leong-Hoi, Audrey

2017-01-01

This work aims at evaluating the possibility of introducing state-of-the-art commercial femtosecond laser system in restorative dentistry by maintaining well-known benefits of lasers for caries removal, but also in overcoming disadvantages such as thermal damage of irradiated substrate. Femtosecond ablation of dental hard tissue is investigated by changing the irradiation parameters (pulsed laser energy, scanning speed and pulse repetition rate), assessed for enamel and dentin. The femtosecond laser system used in this work may be suitable for cavity preparation in dentin and enamel, due to the expected effective ablation and low temperature increase when using ultra short laser pulses. If adequate laser parameters are selected, this system seems to be promising for promoting a laser-assisted, minimally invasive approach in restorative dentistry. (paper)

Influence of wavelength and pulse duration on peripheral thermal and mechanical damage to dentin and alveolar bone during IR laser ablation

Science.gov (United States)

Lee, C.; Ragadio, Jerome N.; Fried, Daniel

2000-03-01

The objective of this study was to measure the peripheral thermal damage produced during the laser ablation of alveolar bone and dentin for clinically relevant IR laser systems. Previous studies have demonstrated that a char layer produced around the laser incision site can inhibit the wound healing process. Moreover, in the case of dentin, a char layer is unsightly and is difficult to bond to with restorative materials. Thermal damage was assessed using polarized light microscopy for laser pulse widths from 500 ns to 300 microseconds at 2.94 micrometer and 9.6 micrometer. Water- cooling was not employed to alleviate thermal damage during the laser irradiation. At 9.6 micrometer, minimal thermal damage was observed for pulse widths on the order of the thermal relaxation time of the deposited laser energy in the tissue, 3 - 4 microseconds, and peripheral thermal damage increased with increasing pulse duration. At 2.94 micrometer, thermal damage was minimal for the Q-switched (500 ns) laser system. This study shows that 9.6 micrometer CO2 laser pulses with pulse widths of 5 - 10 microseconds are well suited for the efficient ablation of dentin and bone with minimal peripheral damage. This work was supported by NIH/NIDCR R29DE12091.

Real-time monitoring of indium tin oxide laser ablation in liquid crystal display patterning

International Nuclear Information System (INIS)

Hong, M.H.; Lu, Y.F.; Meng, M.; Low, T.S.

1998-01-01

Audible acoustic wave detection is applied to investigate KrF excimer laser ablation of Indium Tin Oxide (ITO) thin film layer for Liquid Crystal Display (LCD) patterning. It is found that there is no acoustic wave generation if laser fluence is lower than ITO ablation threshold. For laser fluence higher than the threshold, audible acoustic wave will be detected due to shock wave generation during ITO laser ablation. The amplitude of the acoustic wave is closely related to the laser ablation rate. With more laser pulse applied, the amplitude is dropped to zero because the ITO layer is completely removed. However, if laser fluence is increased higher than ablation threshold for glass substrate, the amplitude is also dropped with pulse number but not to zero. It is due to laser ablation of ITO layer and glass substrate at the same time. Since the thickness of ITO layer is in a scale of 100 nm, laser interaction with glass substrate will happen even at the first pulse of higher laser fluence irradiation. Laser ablation induced ITO plasma emission spectrum in visible light region is analyzed by an Optical Multi-channel Analyzer (OMA). Specific spectral lines are In I (325.8, 410.2 and 451.1 nm) and In II 591.1 nm. Spectral intensities of 410.2 and 451.1 nm lines are selected to characterize the evolution of ITO plasma intensity with laser fluence and pulse number. It is found that the spectral intensities are reduced to zero with laser pulse number. It is also found that spectral lines other than ITO plasma will appear for laser fluence higher than ablation threshold for glass substrate. Threshold fluences for glass and ITO ablation are estimated for setting up a parameter window to control LCD patterning in real-time

Laser ablation in analytical chemistry - A review

Energy Technology Data Exchange (ETDEWEB)

Russo, Richard E.; Mao, Xianglei; Liu, Haichen; Gonzalez, Jhanis; Mao, Samuel S.

2001-10-10

Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas.

Fractional ablative erbium YAG laser

DEFF Research Database (Denmark)

Taudorf, Elisabeth H; Haak, Christina S; Erlendsson, Andrés M

2014-01-01

laser parameters with tissue effects. MATERIALS AND METHODS: Ex vivo pig skin was exposed to a miniaturized 2,940 nm AFXL, spot size 225 µm, density 5%, power levels 1.15-2.22 W, pulse durations 50-225 microseconds, pulse repetition rates 100-500 Hz, and 2, 20, or 50 stacked pulses, resulting in pulse......BACKGROUND AND OBJECTIVES: Treatment of a variety of skin disorders with ablative fractional lasers (AFXL) is driving the development of portable AFXLs. This study measures micropore dimensions produced by a small 2,940 nm AFXL using a variety of stacked pulses, and determines a model correlating...... 190 to 347 µm. CONCLUSIONS: Pulse stacking with a small, low power 2,940 nm AFXL created reproducible shallow to deep micropores, and influenced micropore configuration. Mathematical modeling established relations between laser settings and micropore dimensions, which assists in choosing laser...

Comparative study of excimer and erbium:YAG lasers for ablation of structural components of the knee

Science.gov (United States)

Vari, Sandor G.; Shi, Wei-Qiang; van der Veen, Maurits J.; Fishbein, Michael C.; Miller, J. M.; Papaioannou, Thanassis; Grundfest, Warren S.

1991-05-01

This study was designed to compare the efficiency and thermal effect of a 135 ns pulsed-stretched XeCl excimer laser (308 nm) and a free-running Erbium:YAG laser (2940 nm) with 200 microsecond(s) pulse duration for ablation of knee joint structures (hyaline and fibrous cartilage, tendon and bone). The radiant exposure used for tissue ablation ranged from 2 to 15 J/cm2 for the XeCl excimer and from 33 to 120 J/cm2 for Er:YAG. The excimer and Er:YAG lasers were operated at 4 and 5 Hz respectively. The ablative laser energy was delivered to tissue through fibers. Ablation rates of soft tissues (hyaline and fibrous cartilage, tendon) varied from 8.5 to 203 micrometers /pulse for excimer and from 8.2 to 273 micrometers /pulse for Er:YAG lasers. Ablation rates of soft tissues are linearly dependent on the radiant exposure. Within the range of parameters tested all the tissues except the bone could be rapidly ablated by both lasers. Bone ablation was much less efficient, requiring 15 J/cm2 and 110 J/cm2 radiant exposure for excimer and Er:YAG lasers to ablate 9.5 and 8.2 micrometers tissue per pulse. However, excimer laser ablation produced less thermal damage in the tissues studied compared to Er:YAG at the same laser parameters. The authors conclude that both lasers are capable of efficient knee joint tissue ablation. XeCl excimer laser requires an order of magnitude less energy than Er:YAG laser for comparable tissue ablation.

Elemental fractionation in 785 nm picosecond and femtosecond laser ablation inductively coupled plasma mass spectrometry

International Nuclear Information System (INIS)

Shaheen, M.E.; Gagnon, J.E.; Fryer, B.J.

2015-01-01

Elemental fractionation and ICP-MS signal response were investigated for two different pulse width laser beams originating from the same laser system. Femtosecond and picosecond laser beams at pulse widths of 130 fs and 110 ps, respectively, and wavelength of 785 nm were used to ablate NIST 610 synthetic glass and SRM 1107 Naval Brass B at the same spot for 800 to 1000 laser pulses at different repetition rates (5 to 50 Hz). Elemental fractionation was found to depend on repetition rate and showed a trend with femtosecond laser ablation that is opposite to that observed in picosecond laser ablation for most measured isotopes. ICP-MS signal intensity was higher in femtosecond than picosecond LA-ICP-MS in both NIST 610 and naval brass when ablation was conducted under the same fluence and repetition rate. The differences in signal intensity were partly related to differences in particle size distribution between particles generated by femtosecond and picosecond laser pulses and the consequent differences in transport and ionization efficiencies. The main reason for the higher signal intensity resulting from femtosecond laser pulses was related to the larger crater sizes compared to those created during picosecond laser ablation. Elemental ratios measured using 66 Zn/ 63 Cu, 208 Pb/ 238 U, 232 Th/ 238 U, 66 Zn/ 232 Th and 66 Zn/ 208 Pb were found to change with the number of laser pulses with data points being more scattered in picosecond than femtosecond laser pulses. Reproducibility of replicate measurements of signal intensities, fractionation and elemental ratios was better for fs-LA-ICP-MS (RSD ~ 3 to 6%) than ps-LA-ICP-MS (RSD ~ 7 to 11%). - Highlights: • Fractionation and ICP-MS signal response were investigated for two different pulse widths using NIST 610 and Naval Brass. • Dependence of fractionation indices on repetition rate and pulse width. • Higher ablation rate was observed in picosecond compared to femtosecond laser ablation of NIST 610 and Brass

Impacts of ambient and ablation plasmas on short- and ultrashort-pulse laser processing of surfaces

Czech Academy of Sciences Publication Activity Database

Bulgakova, Nadezhda M.; Panchenko, A.N.; Zhukov, V.P.; Kudryashov, S.I.; Pereira, A.; Marine, W.; Mocek, Tomáš; Bulgakov, A.V.

2014-01-01

Roč. 5, č. 4 (2014), s. 1344-1372 ISSN 2072-666X R&D Projects: GA MŠk ED2.1.00/01.0027; GA MŠk EE2.3.20.0143 Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143 Institutional support: RVO:68378271 Keywords : pulsed laser ablation * laser material processing * laser plasma * ambient gas breakdown * material redeposition * plasma pipe formation * microstructures Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.269, year: 2014

Towards crack-free ablation cutting of thin glass sheets with picosecond pulsed lasers

Science.gov (United States)

Sun, Mingying; Eppelt, Urs; Hartmann, Claudia; Schulz, Wolfgang; Zhu, Jianqiang; Lin, Zunqi

2017-08-01

We investigated the morphology and mechanism of laser-induced damage in the ablation cutting of thin glass sheets with picosecond laser. Two kinds of damage morphologies observed on the cross-section of the cut channel, are caused by high-density free-electrons and the temperature accumulation, respectively. Notches and micro-cracks can be observed on the top surface of the sample near the cut edge. The surface micro-cracks were related to high energy free-electrons and also the heat-affected zone. Heat-affected-zone and visible-cracks free conditions of glass cutting were achieved by controlling the repetition rate and spatial overlap of laser pulses.

Effect of liquid film on near-threshold laser ablation of a solid surface

Energy Technology Data Exchange (ETDEWEB)

Kim, Dongsik; Oh, Bukuk; Lee, Ho

2004-01-30

Enhancement of material ablation and photoacoustic excitation by an artificially deposited liquid film in the process of pulsed-laser ablation (PLA) is investigated in this paper. Ablation threshold, ablation rate, surface topography, and acoustic-transient emission are also measured for dry and liquid film-coated surfaces. The physical mechanisms of enhanced ablation in the liquid-assisted process are analyzed at relatively low laser fluences with negligible effect of laser-produced plasma. Particularly, correlation between material ablation and acoustic-transient generation is examined. In the experiment, aluminum thin-films and bulk foils are ablated by Q-switched Nd:YAG laser pulses. The dependence of ablation rate and laser-induced topography on liquid film thickness and chemical composition is also examined. Photoacoustic emission is measured by the probe beam deflection method utilizing a CW HeNe laser and a microphone. In comparison with a dry ablation process, the liquid-assisted ablation process results in substantially augmented ablation efficiency and reduced ablation threshold. The results indicate that both increased laser-energy coupling, i.e., lowered reflectance, and amplified photoacoustic excitation in explosive vaporization of liquid are responsible for the enhanced material ablation.

Simulation of ablation and plume dynamics under femtosecond double-pulse laser irradiation of aluminum: Comparison of atomistic and continual approaches

Energy Technology Data Exchange (ETDEWEB)

Fokin, Vladimir B.; Povarnitsyn, Mikhail E., E-mail: povar@ihed.ras; Levashov, Pavel R.

2017-02-28

Highlights: • We model double-pulse laser ablation of aluminum using microscopic and macroscopic approaches. • Both methods show decrease in depth of crater with increasing delay between pulses. • Both methods reveal the plume temperature growth with the increasing delay. • Good agreement between results is a step towards the development of combined model. - Abstract: We elaborated two numerical methods, two-temperature hydrodynamics and hybrid two-temperature molecular dynamics, which take into account basic mechanisms of a metal target response to ultrashort laser irradiation. The model used for the description of the electronic subsystem is identical for both approaches, while the ionic part is defined by an equation of state in hydrodynamics and by an interatomic potential in molecular dynamics. Since the phase diagram of the equation of state and corresponding potential match reasonably well, the dynamics of laser ablation obtained by both methods is quite similar. This correspondence can be considered as a first step towards the development of a self-consistent combined model. Two important processes are highlighted in simulations of double-pulse ablation: (1) the crater depth decrease as a result of recoil flux formation in the nascent plume when the delay between the pulses increases; (2) the plume reheating by the second pulse that gives rise to two- three-fold growth of the electron temperature with the delay varying from 0 to 200 ps.

UV laser micromachining of piezoelectric ceramic using a pulsed Nd:YAG laser

International Nuclear Information System (INIS)

Zeng, D.W.; Xie, C.S.; Li, K.; Chan, H.L.W.; Choy, C.L.; Yung, K.C.

2004-01-01

UV laser (λ=355 nm) ablation of piezoelectric lead zirconate titanate (PZT) ceramics in air has been investigated under different laser parameters. It has been found that there is a critical pulse number (N=750). When the pulse number is smaller than the critical value, the ablation rate decreases with increasing pulse number. Beyond the critical value, the ablation rate becomes constant. The ablation rate and concentrations of O, Zr and Ti on the ablated surface increase with the laser fluence, while the Pb concentration decreases due to the selective evaporation of PbO. The loss of the Pb results in the formation of a metastable pyrochlore phase. ZrO 2 was detected by XPS in the ablated zone. Also, the concentrations of the pyrochlore phase and ZrO 2 increase with increasing laser fluence. These results clearly indicate that the chemical composition and phase structure in the ablated zone strongly depend on the laser fluence. The piezoelectric properties of the cut PZT ceramic samples completely disappear due to the loss of the Pb and the existence of the pyrochlore phase. After these samples were annealed at 1150 C for 1 h in a PbO-controlled atmosphere, their phase structure and piezoelectric properties were recovered again. Finally, 1-3 and concentric-ring 2-2 PZT/epoxy composites were fabricated by UV laser micromachining and their thickness modes were measured by impedance spectrum analysis and a d 33 meter. Both composites show high piezoelectric properties. (orig.)

Preparation of TiO sub 2 nanoparticles by pulsed laser ablation: Ambient pressure dependence of crystallization

CERN Document Server

Matsubara, M; Yamaki, T; Itoh, H; Abe, H

2003-01-01

Pulsed laser ablation (PLA) with a KrF excimer laser was used to prepare fine particles of titanium dioxide (TiO sub 2). The ablation in an atmosphere of Ar and O sub 2 (5:5) at total pressures of >= 1 Torr led to the formation of TiO sub 2 nanoparticles composed of anatase and rutile structures without any suboxides. The weight fraction of the rutile/anatase crystalline phases was dependent on the pressure of the Ar/O sub 2 gas. The TiO sub 2 nanoparticles had a spherical shape and their size, ranging from 10 and 14 nm, also appeared to be dependent on the ambient pressure. (author)

Dynamics of laser-induced channel formation in water and influence of pulse duration on the ablation of biotissue under water with pulsed erbium-laser radiation

Science.gov (United States)

Ith, M.; Pratisto, H.; Altermatt, H. J.; Frenz, M.; Weber, H. P.

1994-12-01

The ability to use fiber-delivered erbium-laser radiation for non-contact arthroscopic meniscectomy in a liquid environment was studied. The laser radiation is transmitted through a water-vapor channel created by the leading part of the laser pulse. The dynamics of the channel formation around a submerged fiber tip was investigated with time-resolved flash photography. Strong pressure transients with amplitudes up to a few hundreds of bars measured with a needle hydrophone were found to accompany the channel formation process. Additional pressure transients in the range of kbars were observed after the laser pulse associated with the collapse of the vapor channel. Transmission measurements revealed that the duration the laser-induced channel stays open, and therefore the energy transmittable through it, is substantially determined by the laser pulse duration. The optimum pulse duration was found to be in the range between 250 and 350 µS. This was confirmed by histological evaluations of the laser incisions in meniscus: Increasing the pulse duration from 300 to 800 µs leads to a decrease in the crater depth from 1600 to 300 µm. A comparison of the histological examination after laser treatment through air and through water gave information on the influence of the vapor channel on the ablation efficiency, the cutting quality and the induced thermal damage in the adjacent tissue. The study shows that the erbium laser combined with an adequate fiber delivery system represents an effective surgical instrument liable to become increasingly accepted in orthopedic surgery.

Au, Ag and Au:Ag colloidal nanoparticles synthesized by pulsed laser ablation as SERS substrates

Directory of Open Access Journals (Sweden)

M. Vinod

2014-12-01

Full Text Available Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation. The dependence of laser fluence on the surface plasmon characteristics of the nanoparticles was investigated. Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids. The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process. The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones. The surface enhanced Raman scattering activity of the Au, Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules. Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.

Superhydrophobic/superoleophilic magnetic elastomers by laser ablation

Energy Technology Data Exchange (ETDEWEB)

Milionis, Athanasios, E-mail: am2vy@virginia.edu [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Fragouli, Despina; Brandi, Fernando; Liakos, Ioannis; Barroso, Suset [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Ruffilli, Roberta [Nanochemistry, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Athanassiou, Athanassia, E-mail: athanassia.athanassiou@iit.it [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy)

2015-10-01

Highlights: • We report the development of magnetic nanocomposite sheets. • Laser irradiation of the nanocomposites induces chemical and structural changes to the surface. • The laser-patterned surfaces exhibit superhydrophobicity and superoleophilicity. • The particle contribution in altering the surface and bulk properties of the material is studied. - Abstract: We report the development of magnetic nanocomposite sheets with superhydrophobic and supeoleophilic surfaces generated by laser ablation. Polydimethylsiloxane elastomer free-standing films, loaded homogeneously with 2% wt. carbon coated iron nanoparticles, were ablated by UV (248 nm), nanosecond laser pulses. The laser irradiation induces chemical and structural changes (both in micro- and nano-scale) to the surfaces of the nanocomposites rendering them superhydrophobic. The use of nanoparticles increases the UV light absorption efficiency of the nanocomposite samples, and thus facilitates the ablation process, since the number of pulses and the laser fluence required are greatly reduced compared to the bare polymer. Additionally the magnetic nanoparticles enhance significantly the superhydrophobic and oleophilic properties of the PDMS sheets, and provide to PDMS magnetic properties making possible its actuation by a weak external magnetic field. These nanocomposite elastomers can be considered for applications requiring magnetic MEMS for the controlled separation of liquids.

Atomistic simulations of ultra-short pulse laser ablation of aluminum: validity of the Lambert-Beer law

Science.gov (United States)

Eisfeld, Eugen; Roth, Johannes

2018-05-01

Based on hybrid molecular dynamics/two-temperature simulations, we study the validity of the application of Lambert-Beer's law, which is conveniently used in various modeling approaches of ultra-short pulse laser ablation of metals. The method is compared to a more rigorous treatment, which involves solving the Helmholtz wave equation for different pulse durations ranging from 100 fs to 5 ps and a wavelength of 800 nm. Our simulations show a growing agreement with increasing pulse durations, and we provide appropriate optical parameters for all investigated pulse durations.

Elemental fractionation in 785 nm picosecond and femtosecond laser ablation inductively coupled plasma mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Shaheen, M.E., E-mail: mshaheen73@science.tanta.edu.eg [Department of Physics, Faculty of Sciences, Tanta University, Tanta (Egypt); Gagnon, J.E.; Fryer, B.J. [Great Lakes Institute for Environmental Research (GLIER), University of Windsor, Windsor, Ontario N9B 3P4 (Canada); Department of Earth and Environmental Sciences, University of Windsor, Windsor, Ontario N9B 3P4 (Canada)

2015-05-01

Elemental fractionation and ICP-MS signal response were investigated for two different pulse width laser beams originating from the same laser system. Femtosecond and picosecond laser beams at pulse widths of 130 fs and 110 ps, respectively, and wavelength of 785 nm were used to ablate NIST 610 synthetic glass and SRM 1107 Naval Brass B at the same spot for 800 to 1000 laser pulses at different repetition rates (5 to 50 Hz). Elemental fractionation was found to depend on repetition rate and showed a trend with femtosecond laser ablation that is opposite to that observed in picosecond laser ablation for most measured isotopes. ICP-MS signal intensity was higher in femtosecond than picosecond LA-ICP-MS in both NIST 610 and naval brass when ablation was conducted under the same fluence and repetition rate. The differences in signal intensity were partly related to differences in particle size distribution between particles generated by femtosecond and picosecond laser pulses and the consequent differences in transport and ionization efficiencies. The main reason for the higher signal intensity resulting from femtosecond laser pulses was related to the larger crater sizes compared to those created during picosecond laser ablation. Elemental ratios measured using {sup 66}Zn/{sup 63}Cu, {sup 208}Pb/{sup 238}U, {sup 232}Th/{sup 238}U, {sup 66}Zn/{sup 232}Th and {sup 66}Zn/{sup 208}Pb were found to change with the number of laser pulses with data points being more scattered in picosecond than femtosecond laser pulses. Reproducibility of replicate measurements of signal intensities, fractionation and elemental ratios was better for fs-LA-ICP-MS (RSD ~ 3 to 6%) than ps-LA-ICP-MS (RSD ~ 7 to 11%). - Highlights: • Fractionation and ICP-MS signal response were investigated for two different pulse widths using NIST 610 and Naval Brass. • Dependence of fractionation indices on repetition rate and pulse width. • Higher ablation rate was observed in picosecond compared to

Preclinical investigations of articular cartilage ablation with femtosecond and pulsed infrared lasers as an alternative to microfracture surgery

Science.gov (United States)

Su, Erica; Sun, Hui; Juhasz, Tibor; Wong, Brian J. F.

2014-09-01

Microfracture surgery is a bone marrow stimulation technique for treating cartilage defects and injuries in the knee. Current methods rely on surgical skill and instrumentation. This study investigates the potential use of laser technology as an alternate means to create the microfracture holes. Lasers investigated in this study include an erbium:YAG laser (λ=2.94 μm), titanium:sapphire femtosecond laser system (λ=1700 nm), and Nd:glass femtosecond laser (λ=1053 nm). Bovine samples were ablated at fluences of 8 to 18 J/cm2 with the erbium:YAG laser, at a power of 300±15 mW with the titanium:sapphire femtosecond system, and at an energy of 3 μJ/pulse with the Nd:glass laser. Samples were digitally photographed and histological sections were taken for analysis. The erbium:YAG laser is capable of fast and efficient ablation; specimen treated with fluences of 12 and 18 J/cm2 experienced significant amounts of bone removal and minimal carbonization with saline hydration. The femtosecond laser systems successfully removed cartilage but not clinically significant amounts of bone. Precise tissue removal was possible but not to substantial depths due to limitations of the systems. With additional studies and development, the use of femtosecond laser systems to ablate bone may be achieved at clinically valuable ablation rates.

Performance of Er:YAG laser ablation of hard bone under different irrigation water cooling conditions

Science.gov (United States)

Beltrán Bernal, Lina M.; Shayeganrad, Gholamreza; Kosa, Gabor; Zelechowski, Marek; Rauter, Georg; Friederich, Niklaus; Cattin, Philippe C.; Zam, Azhar

2018-02-01

The biological applicability of the Erbium-doped Yttrium Aluminum Garnet (Er:YAG) laser in surgical processes is so far limited to hard dental tissues. Using the Er:YAG laser for bone ablation is being studied since it has shown good performance for ablating dental hard tissues at the wavelength 2.94 μm, which coincides with the absorption peak of water, one of the main components of hard tissue, like teeth and bone. To obtain a decent performance of the laser in the cutting process, we aim at examining the influence of sequenced water jet irrigation on both, the ablation rate and the prevention of carbonization while performing laser ablation of bone with fixed laser parameters. An Er:YAG laser at 2.94 μm wavelength, 940 mJ energy per pulse, 400 μs pulse width, and 10 Hz repetition rate is used for the ablation of a porcine femur bone under different pulsed water jet irrigation conditions. We used micro-computed tomography (micro-CT) scans to determine the geometry of the ablated areas. In addition, scanning electron microscopy (SEM) is used for qualitative observations for the presence of carbonization and micro-fractures on the ablated surfaces. We evaluate the performance of the laser ablation process for the different water jet conditions in terms of the ablation rate, quantified by the ablated volume per second and the ablation efficiency, calculated as the ablated volume per pulse energy. We provide an optimized system for laser ablation which delivers the appropriate amount of water to the bone and consequently, the bone is ablated in the most efficient way possible without carbonization.

Microsecond enamel ablation with 10.6μm CO2 laser radiation

Science.gov (United States)

Góra, W. S.; McDonald, A.; Hand, D. P.; Shephard, J. D.

2016-02-01

Lasers have been previously been used for dental applications, however there remain issues with thermally-induced cracking. In this paper we investigate the impact of pulse length on CO2 laser ablation of human dental enamel. Experiments were carried in vitro on molar teeth without any modification to the enamel surface, such as grinding or polishing. In addition to varying the pulse length, we also varied pulse energy and focal position, to determine the most efficient ablation of dental hard tissue and more importantly to minimize or eradicate cracking. The maximum temperature rise during the multi pulse ablation process was monitored using a set of thermocouples embedded into the pulpal chamber. The application of a laser device in dental surgery allows removal of tissue with higher precision, which results in minimal loss of healthy dental tissue. In this study we use an RF discharge excited CO2 laser operating at 10.6μm. The wavelength of 10.6 μm overlaps with a phosphate band (PO3-4) absorption in dental hard tissue hence the CO2 laser radiation has been selected as a potential source for modification of the tissue. This research describes an in-depth analysis of single pulse laser ablation. To determine the parameters that are best suited for the ablation of hard dental tissue without thermal cracking, a range of pulse lengths (10-200 μs), and fluences (0-100 J/cm2) are tested. In addition, different laser focusing approaches are investigated to select the most beneficial way of delivering laser radiation to the surface (divergent/convergent beam). To ensure that these processes do not increase the temperature above the critical threshold and cause the necrosis of the tissue a set of thermocouples was placed into the pulpal chambers. Intermittent laser radiation was investigated with and without application of a water spray to cool down the ablation site and the adjacent area. Results show that the temperature can be kept below the critical threshold

Synthesis of oxidation resistant lead nanoparticle films by modified pulsed laser ablation

Energy Technology Data Exchange (ETDEWEB)

Shin, Eunsung; Murray, P. Terrence; Subramanyam, Guru; Malik, Hans K.; Schwartz, Kenneth L. [Research Institute, University of Dayton, Dayton, OH 45469-0170 (United States); Research Institute, University of Dayton, Dayton, OH 45469-0170, USA and Graduate Materials Engineering, University of Dayton, Dayton, OH 45469-0240 (United States); Department of Electrical and Computer Engineering, University of Dayton, Dayton, OH 45469-0232 (United States); Northrop Grumman Electronic Systems, Linthicum, MD 21090 (United States)

2012-07-30

Thin layers of lead nanoparticles have been produced by a modified pulsed laser ablation (PLA) process in which smaller nanoparticles were swept out of the ablation chamber by a stream of flowing Ar. Large ({mu}m-sized) particles, which are usually deposited during the standard PLA process, were successfully eliminated from the deposit. The nanoparticles deposited on room temperature substrates were well distributed, and the most probable particle diameter was in the order of 30 nm. Since lead is highly reactive, the nanoparticles formed in Ar were quickly oxidized upon exposure to air. A small partial pressure of H{sub 2}S gas was subsequently added to the effluent, downstream from the ablation chamber, and this resulted in the formation of nanoparticle deposits that were surprisingly oxidation resistant. The properties of the nanoparticle films (as determined by transmission electron microscopy, scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and conductivity measurements) are reported, and the mechanism of the oxidation retardation process is discussed.

Single-pulse and burst-mode ablation of gold films measured by quartz crystal microbalance

Science.gov (United States)

Andrusyak, Oleksiy G.; Bubelnik, Matthew; Mares, Jeremy; McGovern, Theresa; Siders, Craig W.

2005-02-01

Femtosecond ablation has several distinct advantages: the threshold energy fluence for the onset of damage and ablation is orders of magnitude less than for traditional nanosecond laser machining, and by virtue of the rapid material removal of approximately an optical penetration depth per pulse, femtosecond machined cuts can be cleaner and more precise than those made with traditional nanosecond or longer pulse lasers. However, in many materials of interest, especially metals, this limits ablation rates to 10-100 nm/pulse. We present the results of using multiple pulse bursts to significantly increase the per-burst ablation rate compared to a single pulse with the same integrated energy, while keeping the peak intensity of each individual pulse below the air ionization limit. Femtosecond ablation with pulses centered at 800-nm having integrated energy of up to 30 mJ per pulse incident upon thin gold films was measured via resonance frequency shifts in a gold-electrode-coated quartz-crystal oscillator. Measurements were performed using Michelson-interferometer-based burst generators, with up to 2 ns pulse separations, as well as pulse shaping by programmable acousto-optic dispersive filter (Dazzler from FastLite) with up to 2 ps pulse separations.

Ablation of Liquids for Laser Propulsion With TEA CO2 Laser

National Research Council Canada - National Science Library

Sinko, John; Kodgis, Lisa; Porter, Simon; Sterling, Enrique; Lin, Jun; Pakhomov, Andrew V; Larson, C. W; Mead, Jr., Franklin B

2005-01-01

.... A Transversely Excited at Atmospheric pressure (TEA) CO2 laser operated at 10.6 um, 300 ns pulse width, and 9 J pulse energy was used to ablate liquids contained in various aluminum and glass vessels...

Subcellular analysis by laser ablation electrospray ionization mass spectrometry

Science.gov (United States)

Vertes, Akos; Stolee, Jessica A; Shrestha, Bindesh

2014-12-02

In various embodiments, a method of laser ablation electrospray ionization mass spectrometry (LAESI-MS) may generally comprise micro-dissecting a cell comprising at least one of a cell wall and a cell membrane to expose at least one subcellular component therein, ablating the at least one subcellular component by an infrared laser pulse to form an ablation plume, intercepting the ablation plume by an electrospray plume to form ions, and detecting the ions by mass spectrometry.

Ablation of Liquids for Laser Propulsion with TEA CO2 Laser

National Research Council Canada - National Science Library

Sinko, John; Kodgis, Lisa; Porter, Simon; Sterling, Enrique; Lin, Jun; Pakhomov, Andrew V; Larson, C. W; Mead, Jr, Franklin B

2005-01-01

.... A Transversely Excited at Atmospheric pressure (TEA) CO2 laser operated at 10.6 micro-m, 300 ns pulse width, and 9 J pulse energy was used to ablate liquids contained in various aluminum and glass vessels...

Laser ablation of liquid surface in air induced by laser irradiation through liquid medium

Science.gov (United States)

Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro; Nakahara, Motonao

2010-10-01

The pulse laser ablation of a liquid surface in air when induced by laser irradiation through a liquid medium has been experimentally investigated. A supersonic liquid jet is observed at the liquid-air interface. The liquid surface layer is driven by a plasma plume that is produced by laser ablation at the layer, resulting in a liquid jet. This phenomenon occurs only when an Nd:YAG laser pulse (wavelength: 1064 nm) is focused from the liquid onto air at a low fluence of 20 J/cm2. In this case, as Fresnel’s law shows, the incident and reflected electric fields near the liquid surface layer are superposed constructively. In contrast, when the incident laser is focused from air onto the liquid, a liquid jet is produced only at an extremely high fluence, several times larger than that in the former case. The similarities and differences in the liquid jets and atomization processes are studied for several liquid samples, including water, ethanol, and vacuum oil. The laser ablation of the liquid surface is found to depend on the incident laser energy and laser fluence. A pulse laser light source and high-resolution film are required to observe the detailed structure of a liquid jet.

Relationship between the Ca/P ratio of hydroxyapatite thin films and the spatial energy distribution of the ablation laser in pulsed laser deposition

NARCIS (Netherlands)

Nishikawa, H.; Hasegawa, T; Miyake, A.; Tashiro, Y.; Hashimoto, Y.; Blank, David H.A.; Rijnders, Augustinus J.H.M.

2016-01-01

Variation of the Ca/P ratio in hydroxyapatite (Ca10(PO4)6(OH)2) thin films was studied in relation to the spot size of the ablation laser for two different spatial energy distributions in pulsed laser deposition. One energy distribution is the defocus method with a raw distribution and the other is

InTaO4-based nanostructures synthesized by reactive pulsed laser ablation

International Nuclear Information System (INIS)

Yoshida, Takehito; Toyoyama, Hirokazu; Umezu, Ikurou; Sugimura, Akira

2008-01-01

Nanostructured Ni-doped indium-tantalum-oxides (InTaO 4 ) were synthesized by a reactive pulsed laser ablation process, aiming at the final goal of direct splitting of water under visible sunbeam irradiation. The third harmonics beam of a Nd:YAG laser was focused onto a sintered In 0.9 Ni 0.1 TaO 4-δ target in pure oxygen background gases (0.05-1.00 Torr). Increasing the oxygen gas pressure, via thin films having nanometer-sized strong morphologies, single-crystalline nanoparticles were synthesized in the reactive vapor phases. The nanostructured deposited materials have the monoclinic layered wolframite-type structure of bulk InTaO 4 , without oxygen deficiency. (orig.)

Direct measurements of sample heating by a laser-induced air plasma in pre-ablation spark dual-pulse laser-induced breakdown spectroscopy (LIBS).

Science.gov (United States)

Register, Janna; Scaffidi, Jonathan; Angel, S Michael

2012-08-01

Direct measurements of temperature changes were made using small thermocouples (TC), placed near a laser-induced air plasma. Temperature changes up to ~500 °C were observed. From the measured temperature changes, estimates were made of the amount of heat absorbed per unit area. This allowed calculations to be made of the surface temperature, as a function of time, of a sample heated by the air plasma that is generated during orthogonal pre-ablation spark dual-pulse (DP) LIBS measurements. In separate experiments, single-pulse (SP) LIBS emission and sample ablation rate measurements were performed on nickel at sample temperatures ranging from room temperature to the maximum surface temperature that was calculated using the TC measurement results (500 °C). A small, but real sample temperature-dependent increase in both SP LIBS emission and the rate of sample ablation was found for nickel samples heated up to 500 °C. Comparison of DP LIBS emission enhancement values for bulk nickel samples at room temperature versus the enhanced SP LIBS emission and sample ablation rates observed as a function of increasing sample temperature suggests that sample heating by the laser-induced air plasma plays only a minor role in DP LIBS emission enhancement.

Fabrication of CVD graphene-based devices via laser ablation for wafer-scale characterization

DEFF Research Database (Denmark)

Mackenzie, David; Buron, Jonas Christian Due; Whelan, Patrick Rebsdorf

2015-01-01

Selective laser ablation of a wafer-scale graphene film is shown to provide flexible, high speed (1 wafer/hour) device fabrication while avoiding the degradation of electrical properties associated with traditional lithographic methods. Picosecond laser pulses with single pulse peak fluences of 140......-effect mobility, doping level, on–off ratio, and conductance minimum before and after laser ablation fabrication....

CO2 laser pulse shortening by laser ablation of a metal target

International Nuclear Information System (INIS)

Donnelly, T.; Mazoyer, M.; Lynch, A.; O'Sullivan, G.; O'Reilly, F.; Dunne, P.; Cummins, T.

2012-01-01

A repeatable and flexible technique for pulse shortening of laser pulses has been applied to transversely excited atmospheric (TEA) CO 2 laser pulses. The technique involves focusing the laser output onto a highly reflective metal target so that plasma is formed, which then operates as a shutter due to strong laser absorption and scattering. Precise control of the focused laser intensity allows for timing of the shutter so that different temporal portions of the pulse can be reflected from the target surface before plasma formation occurs. This type of shutter enables one to reduce the pulse duration down to ∼2 ns and to remove the low power, long duration tails that are present in TEA CO 2 pulses. The transmitted energy is reduced as the pulse duration is decreased but the reflected power is ∼10 MW for all pulse durations. A simple laser heating model verifies that the pulse shortening depends directly on the plasma formation time, which in turn is dependent on the applied laser intensity. It is envisaged that this plasma shutter will be used as a tool for pulse shaping in the search for laser pulse conditions to optimize conversion efficiency from laser energy to useable extreme ultraviolet (EUV) radiation for EUV source development.

Glass particles produced by laser ablation for ICP-MSmeasurements

Energy Technology Data Exchange (ETDEWEB)

Gonzalez, J.; Liu, C.; Wen, S.; Mao, X.; Russo, R.E.

2007-06-01

Pulsed laser ablation (266nm) was used to generate glass particles from two sets of standard reference materials using femtosecond (150fs) and nanosecond (4ns) laser pulses with identical fluences of 50 J cm{sup -2}. Scanning electron microscopy (SEM) images of the collected particles revealed that there are more and larger agglomerations of particles produced by nanosecond laser ablation. In contrast to the earlier findings for metal alloy samples, no correlation between the concentration of major elements and the median particle size was found. When the current data on glass were compared with the metal alloy data, there were clear differences in terms of particle size, crater depth, heat affected zone, and ICP-MS response. For example, glass particles were larger than metal alloy particles, the craters in glass were less deep than craters in metal alloys, and damage to the sample was less pronounced in glass compared to metal alloys samples. The femtosecond laser generated more intense ICP-MS signals compared to nanosecond laser ablation for both types of samples, although glass sample behavior was more similar between ns and fs-laser ablation than for metals alloys.

Preparation of ZnS semiconductor nanocrystals using pulsed laser ablation in aqueous surfactant solutions

International Nuclear Information System (INIS)

Choi, S-H; Sasaki, T; Shimizu, Y; Yoon, J-W; Nichols, W T; Sung, Y-E; Koshizaki, N

2007-01-01

Cubic ZnS semiconductor nanocrystals with the size of 2 to 5 nm were prepared by pulsed laser ablation in aqueous surfactant solutions of sodium dodecyl sulfate and cetyltrimethylammonium bromide without any further treatments. The obtained suspensions of the nanocrystals have broad photoluminescence emission from 375 to 600 nm. The abundance and emission intensity of the nanocrystals depend on the concentration of the surfactant in solution

Experimental study on 800 nm femtosecond laser ablation of fused silica in air and vacuum

Energy Technology Data Exchange (ETDEWEB)

Xu, Shi-zhen, E-mail: xusz@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Yao, Cai-zhen; Liao, Wei [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Yuan, Xiao-dong, E-mail: yxd66my@163.com [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Wang, Tao [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Zu, Xiao-tao [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2016-10-15

Ablation rates of fused silica were studied as a function of femtosecond laser pulse fluences (0.7–41 J/cm{sup 2}) in air and vacuum. The experiment was conducted by using a Ti:sapphire laser that emits radiation at 800 nm with a pulse width of 35 fs and a repetition rate of 10 Hz. The morphology and ablation depth of laser-induced damage crater were evaluated by using optical microscopy and scanning electron microscopy (SEM). Ablation rates were calculated from the depth of craters induced by multiple laser pulses. Results showed that two ablation regimes, i.e. non-thermal and thermal ablation co-existed in air and vacuum at low and moderate fluences. A drop of ablation rate was observed at high fluence (higher than 9.5 J/cm{sup 2}) in air. While in vacuum, the ablation rate increased continuously with the increasing of laser fluence and much higher than that in air. The drop of ablation rate observed at high fluence in air was due to the strong defocusing effects associated with the non-equilibrium ionization of air. Furthermore, the laser-induced damage threshold (LIDT), which was determined from the relationship between crater area and the logarithm of laser energy, was found to depend on the number of incident pulses on the same spot, and similar phenomenon was observed in air and vacuum.

Opacity and atomic analysis of double pulse laser ablated Li plasma

Science.gov (United States)

Sivakumaran, V.; Joshi, H. C.; Kumar, Ajai

2014-09-01

Opacity effects for neutral and ionic emission lines of lithium have been investigated by Atomic Data Analysis Structure (ADAS). Line ratios and opacity corrected photon emissivity coefficients are calculated over a wide range of electron temperatures and densities. The experimentally measured temporal evolution of the line profiles of the over dense Li plasma formed in the double pulse laser ablation experiment have been explained using the ADAS analysis and the plasma parameters of the plasma plume under consideration have been estimated. These results could be projected as a diagnostic tool to estimate plasma parameters of an over dense lithium plasma.

Recolonization of laser-ablated bacterial biofilm.

Science.gov (United States)

Nandakumar, Kanavillil; Obika, Hideki; Utsumi, Akihiro; Toshihiko, Ooie; Yano, Tetsuo

2004-01-20

The recolonization of laser-ablated bacterial monoculture biofilm was studied in the laboratory by using a flow-cytometer system. The marine biofilm-forming bacterium Pseudoalteromonas carrageenovora was used to develop biofilms on titanium coupons. Upon exposure to a low-power pulsed irradiation from an Nd:YAG laser, the coupons with biofilm were significantly reduced both in terms of total viable count (TVC) and area cover. The energy density used for a pulse of 5 ns was 0.1 J/cm(2) and the durations of irradiation exposure were 5 and 10 min. When placed in a flow of dilute ZoBell marine broth medium (10%) the laser-destructed bacterial film in a flow-cytometer showed significant recovery over a period of time. The flow of medium was regulated at 3.2 ml/min. The increase in area cover and TVC, however, was significantly less than that observed for nonirradiated control (t-test, Precolonization compared to control was thought be due to the lethal and sublethal impacts of laser irradiation on bacteria. This observation thus provided data on the online recolonization speed of biofilm, which is important when considering pulsed laser irradiation as an ablating technique of biofilm formation and removal in natural systems. Copyright 2003 Wiley Periodicals, Inc.

Characterization of laser ablation of copper in the irradiance regime of laser-induced breakdown spectroscopy analysis

Energy Technology Data Exchange (ETDEWEB)

Picard, J., E-mail: jessica.picard@cea.fr [Commissariat à l' Energie Atomique, DAM, Valduc, F-21120 Is-sur-Tille (France); Sirven, J.-B.; Lacour, J.-L. [Commissariat à l' Energie Atomique, DEN/DANS/DPC/SEARS/LANIE, Saclay, F-91191 Gif-sur-Yvette (France); Musset, O. [Université de Bourgogne, Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR CNRS 5209, F-21000 Dijon (France); Cardona, D.; Hubinois, J.-C. [Commissariat à l' Energie Atomique, DAM, Valduc, F-21120 Is-sur-Tille (France); Mauchien, P. [Commissariat à l' Energie Atomique, DEN/DANS/DPC/SEARS/LANIE, Saclay, F-91191 Gif-sur-Yvette (France)

2014-11-01

The LIBS signal depends both on the ablated mass and on the plasma excitation temperature. These fundamental parameters depend in a complex manner on laser ablation and on laser–plasma coupling. As several works in the literature suggest that laser ablation processes play a predominant role compared to plasma heating phenomena in the LIBS signal variations, this paper focuses on the study of laser ablation. The objective was to determine an interaction regime enabling to maximally control the laser ablation. Nanosecond laser ablation of copper at 266 nm was characterized by scanning electron microscopy and optical profilometry analysis, in air at 1 bar and in the vacuum. The laser beam spatial profile at the sample surface was characterized in order to give realistic values of the irradiance. The effect of the number of accumulated laser shots on the crater volume was studied. Then, the ablation crater morphology, volume, depth and diameter were measured as a function of irradiance between 0.35 and 96 GW/cm². Results show that in the vacuum, a regular trend is observed over the whole irradiance range. In air at 1 bar, below a certain irradiance, laser ablation is very similar to the vacuum case, and the ablation efficiency of copper was estimated at 0.15 ± 0.03 atom/photon. Beyond this irradiance, the laser beam propagation is strongly disrupted by the expansion of the dense plasma, and plasma shielding appears. The fraction of laser energy used for laser ablation and for plasma heating is estimated in the different irradiance regimes. - Highlights: • The morphology of copper's craters was studied as a function of the pulse energy. • Correlation at low energy and two pressures between crater volume and pulse energy • The ablation efficiency of copper at 1 bar is equal to 0.15 atom/photon. • Ablation efficiency in the vacuum is not limited by laser–plasma interaction. • Physical mechanisms of laser ablation at both pressures are discussed.

Nanoparticle fabrication of hydroxyapatite by laser ablation in water

International Nuclear Information System (INIS)

Musaev, O. R.; Wieliczka, D. M.; Wrobel, J. M.; Kruger, M. B.; Dusevich, V.

2008-01-01

Synthetic polycrystalline hydroxyapatite was ablated in water with 337 nm radiation from a UV nitrogen pulsed laser. According to transmission electron microscopy micrographs, the ablated particles were approximately spherical and had a size of ∼80 nm. Raman spectroscopic analysis demonstrated that particles had the same structure as the original crystal. X-ray photoelectron spectroscopy showed that the surface chemical composition was close to that of the original material. The characteristics of the ablated particles and estimations of the temperature rise of the hydroxyapatite surface under laser irradiation are consistent with the mechanism of explosive boiling being responsible for ablation. The experimental observations offer the basis for preparation of hydroxyapatite nanoparticles by laser ablation in water

Gas-phase mechanisms in the growth of ZrCyN1-y thin films by pulsed reactive crossed-beam laser ablation

International Nuclear Information System (INIS)

Spillmann, H.; Clerc, C.; Doebeli, M.; Willmott, P.R.

2002-01-01

Superhard zirconium carbonitride films have been grown via pulsed reactive crossed-beam laser ablation (PRCLA) using zirconium metal and a nitrogen- and carbon-containing gas pulse mixture. The control of stoichiometry was much simplified by using the thermally stable gas-phase species N 2 and CH 4 . The gas-phase processes are investigated using quadrupole mass spectroscopy and optical emission spectroscopy. The excitation of the ablation plume depends intimately on the collision partner of the gas pulse, in particular on its density of states and the probability of energy transfer to internal degrees of freedom

Time resolved emission spectroscopy investigations of pulsed laser ablated plasmas of ZrO2 and Al2O3

International Nuclear Information System (INIS)

Hadoko, A D; Lee, P S; Lee, P; Mohanty, S R; Rawat, R S

2006-01-01

With the rising trend of synthesizing ultra thin films and/or quantum-confined materials using laser ablation, optimization of deposition parameters plays an essential role in obtaining desired film characteristics. This paper presents the initial step of plasma optimization study by examining temporal distribution of the plasma formation by pulsed laser ablation of materials. The emitted spectra of ZrO 2 and Al 2 O 3 are obtained ∼3mm above the ablated target to derive the ablated plasma characteristics. The plasma temperature is estimated to be at around 2.35 eV, with electron density of 1.14 x 10 16 (cm -3 ). Emission spectra with different gate delay time (40-270 ns) are captured to study the time resolved plume characteristics. Transitory elemental species are identified

Microdrilling of metals with an inexpensive and compact ultra-short-pulse fiber amplified microchip laser

Energy Technology Data Exchange (ETDEWEB)

Ancona, A. [Friedrich-Schiller-Universitaet Jena, Institut fuer Angewandte Physik, Jena (Germany); CNR-INFM Regional Laboratory ' LIT3' , Dipartimento Interuniversitario di Fisica, Bari (Italy); Nodop, D.; Limpert, J.; Nolte, S. [Friedrich-Schiller-Universitaet Jena, Institut fuer Angewandte Physik, Jena (Germany); Tuennermann, A. [Friedrich-Schiller-Universitaet Jena, Institut fuer Angewandte Physik, Jena (Germany); Fraunhofer Institute for Applied Optics and Precision Engineering (IOF), Jena (Germany)

2009-01-15

We have investigated the ultra-fast microdrilling of metals using a compact and cheap fiber amplified passively Q-switched microchip laser. This laser system delivers 100-ps pulses with repetition rates higher than 100 kHz and pulse energies up to 80 {mu}J. The ablation process has been studied on metals with quite different thermal properties (copper, carbon steel and stainless steel). The dependence of the ablation depth per pulse on the pulse energy follows the same logarithmic scaling laws governing laser ablation with sub-picosecond pulses. Structures ablated with 100-ps laser pulses are accompanied only by a thin layer of melted material. Despite this, results with a high level of precision are obtained when using the laser trepanning technique. This simple and affordable laser system could be a valid alternative to nanosecond laser sources for micromachining applications. (orig.)

Onset and evolution of laser induced periodic surface structures on indium tin oxide thin films for clean ablation using a repetitively pulsed picosecond laser at low fluence

Science.gov (United States)

Farid, N.; Dasgupta, P.; O’Connor, G. M.

2018-04-01

The onset and evolution of laser induced periodic surface structures (LIPSS) is of key importance to obtain clean ablated features on indium tin oxide (ITO) thin films at low fluences. The evolution of subwavelength periodic nanostructures on a 175 nm thick ITO film, using 10 ps laser pulses at a wavelength of 1032 nm, operating at 400 kHz, is investigated. Initially nanoblisters are observed when a single pulse is applied below the damage threshold fluence (0.45 J cm‑2) the size and distribution of nanoblisters are found to depend on fluence. Finite difference time domain (FDTD) simulations support the hypothesis that conductive nanoblisters can enhance the local intensity of the applied electromagnetic field. The LIPSS are observed to evolve from regions where the electric field enhancement has occurred; LIPSS has a perpendicular orientation relative to the laser polarization for a small number (5) pulses, the orientation of the periodic structures appears to rotate and evolve to become aligned in parallel with the laser polarization at approximately the same periodicity. These orientation effects are not observed at higher fluence—due to the absence of the nanoblister-like structures; this apparent rotation is interpreted to be due to stress-induced fragmentation of the LIPSS structure. The application of subsequent pulses leads to clean ablation. LIPSS are further modified into features of a shorter period when laser scanning is used. Results provide evidence that the formation of conductive nanoblisters leads to the enhancement of the applied electromagnetic field and thereby can be used to precisely control laser ablation on ITO thin films.

Near-field mapping by laser ablation of PMMA coatings

DEFF Research Database (Denmark)

Fiutowski, J.; Maibohm, C.; Kostiucenko, O.

2011-01-01

The optical near-field of lithography-defined gold nanostructures, arranged into regular arrays on a gold film, is characterized via ablation of a polymer coating by laser illumination. The method utilizes femto-second laser pulses from a laser scanning microscope which induces electrical field...... that the different stages in the ablation process can be controlled and characterized making the technique suitable for characterizing optical near-fields of metal nanostructures....

Amorphization of silicon by femtosecond laser pulses

International Nuclear Information System (INIS)

Jia, Jimmy; Li Ming; Thompson, Carl V.

2004-01-01

We have used femtosecond laser pulses to drill submicron holes in single crystal silicon films in silicon-on-insulator structures. Cross-sectional transmission electron microscopy and energy dispersive x-ray analysis of material adjacent to the ablated holes indicates the formation of a layer of amorphous Si. This demonstrates that even when material is ablated using femtosecond pulses near the single pulse ablation threshold, sufficient heating of the surrounding material occurs to create a molten zone which solidifies so rapidly that crystallization is bypassed

Deposition of high Tc superconductor thin films by pulsed excimer laser ablation and their post-synthesis processing

International Nuclear Information System (INIS)

Ogale, S.B.

1992-01-01

This paper describes the use of pulsed excimer laser ablation technique for deposition of high quality superconductor thin films on different substrate materials such as Y stabilized ZrO 2 , SrTiO 3 , LiNbO 3 , Silicon and Stainless Steels, and dopant incorporation during the film depositions. Processing of deposited films using ion and laser beams for realisation of device features are presented. 28 refs., 16 figs

Resonant ablation of single-wall carbon nanotubes by femtosecond laser pulses

International Nuclear Information System (INIS)

Arutyunyan, N R; Komlenok, M S; Kononenko, V V; Pashinin, V P; Pozharov, A S; Konov, V I; Obraztsova, E D

2015-01-01

The thin 50 nm film of bundled arc-discharge single-wall carbon nanotubes was irradiated by femtosecond laser pulses with wavelengths 675, 1350 and 1745 nm corresponding to the absorption band of metallic nanotubes E 11 M , to the background absorption and to the absorption band of semiconducting nanotubes E 11 S , respectively. The aim was to induce a selective removal of nanotubes of specific type from the bundled material. Similar to conducted thermal heating experiments, the effect of laser irradiation results in suppression of all radial breathing modes in the Raman spectra, with preferential destruction of the metallic nanotubes with diameters less than 1.26 nm and of the semiconducting nanotubes with diameters 1.36 nm. However, the etching rate of different nanotubes depends on the wavelength of the laser irradiation. It is demonstrated that the relative content of nanotubes of different chiralities can be tuned by a resonant laser ablation of undesired nanotube fraction. The preferential etching of the resonant nanotubes has been shown for laser wavelengths 675 nm (E 11 M ) and 1745 nm (E 11 S ). (paper)

Water content contribution in calculus phantom ablation during Q-switched Tm:YAG laser lithotripsy.

Science.gov (United States)

Zhang, Jian J; Rajabhandharaks, Danop; Xuan, Jason Rongwei; Wang, Hui; Chia, Ray W J; Hasenberg, Tom; Kang, Hyun Wook

2015-01-01

Q-switched (QS) Tm:YAG laser ablation mechanisms on urinary calculi are still unclear to researchers. Here, dependence of water content in calculus phantom on calculus ablation performance was investigated. White gypsum cement was used as a calculus phantom model. The calculus phantoms were ablated by a total 3-J laser pulse exposure (20 mJ, 100 Hz, 1.5 s) and contact mode with N=15 sample size. Ablation volume was obtained on average 0.079, 0.122, and 0.391  mm3 in dry calculus in air, wet calculus in air, and wet calculus in-water groups, respectively. There were three proposed ablation mechanisms that could explain the effect of water content in calculus phantom on calculus ablation performance, including shock wave due to laser pulse injection and bubble collapse, spallation, and microexplosion. Increased absorption coefficient of wet calculus can cause stronger spallation process compared with that caused by dry calculus; as a result, higher calculus ablation was observed in both wet calculus in air and wet calculus in water. The test result also indicates that the shock waves generated by short laser pulse under the in-water condition have great impact on the ablation volume by Tm:YAG QS laser.

Mechanism of laser ablation for aqueous media irradiated under confined-stress conditions

International Nuclear Information System (INIS)

Oraevsky, A.A.; Jacques, S.L.; Tittel, F.K.

1995-01-01

Pulsed laser ablation of aqueous medium irradiated under conditions of temporal confinement of thermal stress is described. Time-resolved measurements of laser-induced transient stress waves with simultaneous imaging of ablation process by laser-flash photography were performed. Stress transients induced in aqueous solution of K 2 CrO 4 by ablative nanosecond laser pulses at 355 nm were studied by a broad-band lithium niobate acoustic transducer. Recoil momentum upon material ejection was measured from the temporal profiles of the acoustic transducer signal as a function of incident laser fluence. Cavitation bubbles produced in the irradiated volume during the tensile phase of thermoelastic stress were shown to drive material ejection at temperatures substantially below 100 degree C. Experimental data are evident that nanosecond-pulse laser ablation of aqueous media (when temporal stress-confinement conditions are satisfied) include the following two main stages of material ejection: (1) ejection of water microdroplets due to expansion and rupture of subsurface cavitation bubbles; (2) ejection of liquid streams with substantial volume upon collapse of initial crater and large cavitation bubbles in the depth of irradiated volume (after coalescence of smaller bubbles). copyright 1995 American Institute of Physics

An investigation on 800 nm femtosecond laser ablation of K9 glass in air and vacuum

Energy Technology Data Exchange (ETDEWEB)

Xu, Shi-zhen, E-mail: xusz@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Yao, Cai-zhen [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Dou, Hong-qiang [Department of Material Science and Engineering, Sichuan Engineering Technical College, Deyang 618000 (China); Liao, Wei, E-mail: liaowei@caep.cn [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Li, Xiao-yang; Ding, Ren-jie [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Zhang, Li-juan; Liu, Hao; Yuan, Xiao-dong [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Zu, Xiao-tao [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2017-06-01

Highlights: • The fs laser ablation of borosilicate glass (K9) were investigated under 35 and 500 fs pulses. • At high fluence regime, the ablation rate at 35 fs in air increased to a plateau, and 500 fs in air and vacuum decreased. • The mechanisms of multiple-photon ionization and impact ionization were included. • The ablation morphologies of smooth zone and laser-induced periodic surface structures were presented and illustrated. • The ablation mechanisms of non-thermal and thermal ablation were included. - Abstract: Ablation rates of K9 glass were studied as a function of femtosecond laser fluences. The central wavelength was 800 nm, and pulse durations of 35 fs and 500 fs in air and vacuum were employed. Ablation thresholds of 0.42 J/cm{sup 2} and 2.1 J/cm{sup 2} were obtained at 35 fs and 500 fs, respectively, which were independent with the ambient conditions and depend on the incident pulse numbers due to incubation effects. The ablation rate of 35 fs pulse laser increased with the increasing of laser fluence in vacuum, while in air condition, it slowly increased to a plateau at high fluence. The ablation rate of 500 fs pulse laser showed an increase at low fluence and a slow drop of ablation rate was observed at high fluence in air and vacuum, which may due to the strong defocusing effects associated with the non-equilibrium ionization of air, and/or the shielding effects of conduction band electrons (CBEs) produced by multi-photon ionization and impact ionization in K9 glass surface. The typical ablation morphologies, e.g. smooth zone and laser-induced periodic surface structures (LIPSS) were also presented and illustrated.

Measurement of ablation threshold of oxide-film-coated aluminium nanoparticles irradiated by femtosecond laser pulses

International Nuclear Information System (INIS)

Chefonov, O V; Ovchinnikov, A V; Il'ina, I V; Agranat, M B

2016-01-01

We report the results of experiments on estimation of femtosecond laser threshold intensity at which nanoparticles are removed from the substrate surface. The studies are performed with nanoparticles obtained by femtosecond laser ablation of pure aluminium in distilled water. The attenuation (or extinction, i.e. absorption and scattering) spectra of nanoparticles are measured at room temperature in the UV and optical wavelength ranges. The size of nanoparticles is determined using atomic force microscopy. A new method of scanning photoluminescence is proposed to evaluate the threshold of nanoparticle removal from the surface of a glass substrate exposed to IR femtosecond laser pulses with intensities 10 11 – 10 13 W cm -2 . (interaction of laser radiation with matter)

Recycling of pneumatic scrap tyre into nano-crumb rubber by pulsed laser ablation in different pH media

Science.gov (United States)

Ezaan Khamsan, Nur; Bidin, Noriah; Islam, Shumaila; Daud, Suzairi; Krishnan, Ganesan; Bakar, Mohamad Aizat A.; Naqiuddin Razali, Muhamad; Khamis, Jamil

2018-05-01

Nano crumb rubber from scrap tyre is synthesized via 1064 nm pulsed Nd:YAG laser ablation in three different pH media i.e. DI-water (pH∼6.45), D-limonene (pH∼3.47) and NaOH solution (pH∼13.41). Field Emission Scanning Electron Microscope (FESEM) results show spherical morphology of crumb rubber with high degree of aggregation in DI-water and in D-limonene. However, dispersion of crumb rubbers is observed in NaOH solution. The smallest particles size is obtained in NaOH solution within the range of 10.9 nm – 74.3 nm. Energy-dispersive X-ray spectroscopy (EDX) and FTIR analysis confirmed the elements distribution and chemical bonding of rubber with DI-water, D-limonene and NaOH solution. The experimental findings shows that pulsed Nd:YAG laser ablation has potential for fabricating nano-crumb rubber in liquid media.

Generation of dense, pulsed beams of refractory metal atoms using two-stage laser ablation

International Nuclear Information System (INIS)

Kadar-Kallen, M.A.; Bonin, K.D.

1994-01-01

We report a technique for generating a dense, pulsed beam of refractory metal atoms using two-stage laser ablation. An atomic beam of uranium was produced with a peak, ground-state number density of 1x10 12 cm -3 at a distance of z=27 cm from the source. This density can be scaled as 1/z 3 to estimate the density at other distances which are also far from the source

Precision machining of pig intestine using ultrafast laser pulses

Science.gov (United States)

Beck, Rainer J.; Góra, Wojciech S.; Carter, Richard M.; Gunadi, Sonny; Jayne, David; Hand, Duncan P.; Shephard, Jonathan D.

2015-07-01

Endoluminal surgery for the treatment of early stage colorectal cancer is typically based on electrocautery tools which imply restrictions on precision and the risk of harm through collateral thermal damage to the healthy tissue. As a potential alternative to mitigate these drawbacks we present laser machining of pig intestine by means of picosecond laser pulses. The high intensities of an ultrafast laser enable nonlinear absorption processes and a predominantly nonthermal ablation regime. Laser ablation results of square cavities with comparable thickness to early stage colorectal cancers are presented for a wavelength of 1030 nm using an industrial picosecond laser. The corresponding histology sections exhibit only minimal collateral damage to the surrounding tissue. The depth of the ablation can be controlled precisely by means of the pulse energy. Overall, the application of ultrafast lasers to ablate pig intestine enables significantly improved precision and reduced thermal damage to the surrounding tissue compared to conventional techniques.

Selective ablation of a titanium nitride film on tungsten carbide substrate using ultrashort laser pulses

International Nuclear Information System (INIS)

Oliveira, Eduardo Spinelli

2017-01-01

Surface coatings are applied to many cutting tools in the metallurgical industry in order to improve cutting efficiency and extend its useful life. In this work, tests were performed to remove the coating of titanium aluminum nitride (TiAlN) on tungsten carbide (WC-Co) pellets, using an ultrashort laser pulses beam. After determination of the damage thresholds of the film and the substrate, were ablated on the surface of the coating lines using two ablation conditions, it was initially operated on the low fluence regime for the film, and later on the low fluence regime of the substrate, far below the threshold of the film, applying high overlapping pulses. A laser induced breakdown spectroscopy (LIBS) system was set up to monitor the materials present in the plasma generated by the laser, but the system did not present sufficient sensitivity to read the low intensity of the plasma generated in the process and was not used. After the analysis of the traces by electron microscopy, optical profilometer and X-ray fluorescence spectroscopy, it was not possible to determine a safe process to carry out the selective removal of the film in question, however, due to the data obtained and observations of the results in some traces, new possibilities were raised, opening the discussion for future work. (author)

Double nanosecond pulses generation in ytterbium fiber laser

Energy Technology Data Exchange (ETDEWEB)

Veiko, V. P.; Samokhvalov, A. A., E-mail: samokhvalov.itmo@gmail.com; Yakovlev, E. B.; Zhitenev, I. Yu.; Kliushin, A. N. [Saint-Petersburg State University of Information Technologies, Mechanics and Optics, Kronverksky Pr. 49, Saint Petersburg (Russian Federation); Lednev, V. N. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov Str., 38, Moscow (Russian Federation); National University of Science and Technology MISiS, Leninskyave., 4, Moscow (Russian Federation); Pershin, S. M. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov Str., 38, Moscow (Russian Federation)

2016-06-15

Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential “opening” radio pulses with a delay of 0.2–1 μs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse. Laser crater studies and plasma emission measurements revealed an improved efficiency of laser ablation in the double pulse mode.

Investigation on repetition rate and pulse duration influences on ablation efficiency of metals using a high average power Yb-doped ultrafast laser

Directory of Open Access Journals (Sweden)

Lopez J.

2013-11-01

Full Text Available Ultrafast lasers provide an outstanding processing quality but their main drawback is the low removal rate per pulse compared to longer pulses. This limitation could be overcome by increasing both average power and repetition rate. In this paper, we report on the influence of high repetition rate and pulse duration on both ablation efficiency and processing quality on metals. All trials have been performed with a single tunable ultrafast laser (350 fs to 10ps.

Laser cutting of bone tissue under bulk water with a pulsed ps-laser at 532 nm.

Science.gov (United States)

Tulea, Cristian-Alexander; Caron, Jan; Gehlich, Nils; Lenenbach, Achim; Noll, Reinhard; Loosen, Peter

2015-10-01

Hard-tissue ablation was already investigated for a broad variety of pulsed laser systems, which cover almost the entire range of available wavelengths and pulse parameters. Most effective in hard-tissue ablation are Er:YAG and CO2 lasers, both utilizing the effect of absorption of infrared wavelengths by water and so-called explosive vaporization, when a thin water film or water–air spray is supplied. The typical flow rates and the water layer thicknesses are too low for surgical applications where bleeding occurs and wound flushing is necessary. We studied a 20 W ps-laser with 532 nm wavelength and a pulse energy of 1 mJ to effectively ablate bones that are submerged 14 mm under water. For these laser parameters, the plasma-mediated ablation mechanism is dominant. Simulations based on the blow-off model predict the cut depth and cross-sectional shape of the incision. The model is modified considering the cross section of the Gaussian beam, the incident angle, and reflections. The ablation rate amounts to 0.2  mm3/s, corresponding to an increase by at least 50% of the highest values published so far for ultrashort laser ablation of hard tissue.

Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response

International Nuclear Information System (INIS)

Ortiz, Rocio; Quintana, Iban; Etxarri, Jon; Lejardi, Ainhoa; Sarasua, Jose-Ramon

2011-01-01

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response

Energy Technology Data Exchange (ETDEWEB)

Ortiz, Rocio; Quintana, Iban; Etxarri, Jon [Manufacturing Processes Department, Fundacion TEKNIKER, Av. Otaola 20, 20600, Eibar, Guipuzcoa (Spain); Lejardi, Ainhoa; Sarasua, Jose-Ramon [Department of Mining and Metallurgy Engineering and Materials Science, School of Engineering, University of the Basque Country (EHU-UPV), Alameda de Urquijo s/n, 48013 Bilbao (Spain)

2011-11-01

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

In-vitro ablation of fibrocartilage by XeCl excimer laser

Science.gov (United States)

Buchelt, Martin; Papaioannou, Thanassis; Fishbein, Michael C.; Peters, Werner; Beeder, Clain; Grundfest, Warren S.

1991-07-01

A 308 nm excimer laser was employed for ablation of human fibrocartilage. Experiments were conducted in vitro. The tissue response was investigated with respect to dosimetry (ablation rate versus radiant exposure) and thermal effect (thermographic analysis). Irradiation was performed via a 600 um fiber, with radiant exposures ranging between 20mj/mm2 and 80mj/mm2, at 20Hz. The ablation rates were found to range from 3um/pulse to 80um/pulse depending on the radiant exposure and/or the applied pressure on the delivery system. Thermographic analysis, during ablation, revealed maximum average temperatures of about 65 degree(s)C. Similar measurements performed, for the purpose of comparison, with a CW Nd:YAG and a CW CO2 laser showed higher values, of the order of 200 degree(s)C.

Numerical Response Surfaces of Volume of Ablation and Retropulsion Amplitude by Settings of Ho:YAG Laser Lithotripter

Directory of Open Access Journals (Sweden)

Jian J. Zhang

2018-01-01

Full Text Available Objectives. Although laser lithotripsy is now the preferred treatment option for urolithiasis due to shorter operation time and a better stone-free rate, the optimal laser settings for URS (ureteroscopic lithotripsy for less operation time remain unclear. The aim of this study was to look for quantitative responses of calculus ablation and retropulsion by performing operator-independent experiments to determine the best fit versus the pulse energy, pulse width, and the number of pulses. Methods. A lab-built Ho:YAG laser was used as the laser pulse source, with a pulse energy from 0.2 J up to 3.0 J and a pulse width of 150 μs up to 1000 μs. The retropulsion was monitored using a high-speed camera, and the laser-induced craters were evaluated with a 3-D digital microscope. The best fit to the experimental data is done by a design of experiment software. Results. The numerical formulas for the response surfaces of ablation speed and retropulsion amplitude are generated. Conclusions. The longer the pulse, the less the ablation or retropulsion, while the longer pulse makes the ablation decrease faster than the retropulsion. The best quadratic fit of the response surface for the volume of ablation varied nonlinearly with pulse duration and pulse number.

Numerical Response Surfaces of Volume of Ablation and Retropulsion Amplitude by Settings of Ho:YAG Laser Lithotripter

Science.gov (United States)

Rutherford, Jonathan; Solomon, Metasebya; Cheng, Brian; Xuan, Jason R.; Gong, Jason; Yu, Honggang; Xia, Michael L. D.; Yang, Xirong; Hasenberg, Thomas; Curran, Sean

2018-01-01

Objectives Although laser lithotripsy is now the preferred treatment option for urolithiasis due to shorter operation time and a better stone-free rate, the optimal laser settings for URS (ureteroscopic lithotripsy) for less operation time remain unclear. The aim of this study was to look for quantitative responses of calculus ablation and retropulsion by performing operator-independent experiments to determine the best fit versus the pulse energy, pulse width, and the number of pulses. Methods A lab-built Ho:YAG laser was used as the laser pulse source, with a pulse energy from 0.2 J up to 3.0 J and a pulse width of 150 μs up to 1000 μs. The retropulsion was monitored using a high-speed camera, and the laser-induced craters were evaluated with a 3-D digital microscope. The best fit to the experimental data is done by a design of experiment software. Results The numerical formulas for the response surfaces of ablation speed and retropulsion amplitude are generated. Conclusions The longer the pulse, the less the ablation or retropulsion, while the longer pulse makes the ablation decrease faster than the retropulsion. The best quadratic fit of the response surface for the volume of ablation varied nonlinearly with pulse duration and pulse number. PMID:29707187

Generation of ultra-small InN nanocrystals by pulsed laser ablation of suspension in organic solution

Energy Technology Data Exchange (ETDEWEB)

Kursungoez, Canan; Uzcengiz Simsek, Elif; Ortac, Buelend [Bilkent University, Materials Science and Nanotechnology Department, UNAM-National Nanotechnology Research Center, Ankara (Turkey); Bilkent University, Institute of Materials Science and Nanotechnology, Ankara (Turkey); Tuzakli, Refik [Bilkent University, Materials Science and Nanotechnology Department, UNAM-National Nanotechnology Research Center, Ankara (Turkey)

2017-03-15

Nanostructures of InN have been extensively investigated since nano-size provides a number of advantages allowing applications in nanoscale electronic and optoelectronic devices. It is quite important to obtain pure InN nanocrystals (InN-NCs) to reveal the characteristic features, which gain interest in the literature. Here, we proposed a new approach for the synthesis of ultra-small hexagonal InN-NCs by using suspension of micron-sized InN powder in ethanol with pulsed laser ablation method. The liquid environment, laser energy and ablation time were optimized and a post-synthesis treatment, centrifugation, was performed to achieve InN-NCs with the smallest size. Besides, the micron-sized InN powder suspension, as a starting material, enabled us to obtain InN-NCs having diameters smaller than 5 nm. We also presented a detailed characterization of InN-NCs and demonstrated that the formation mechanism mainly depends on the fragmentation due to laser irradiation of the suspension. (orig.)

Generation of ultra-small InN nanocrystals by pulsed laser ablation of suspension in organic solution

International Nuclear Information System (INIS)

Kursungoez, Canan; Uzcengiz Simsek, Elif; Ortac, Buelend; Tuzakli, Refik

2017-01-01

Nanostructures of InN have been extensively investigated since nano-size provides a number of advantages allowing applications in nanoscale electronic and optoelectronic devices. It is quite important to obtain pure InN nanocrystals (InN-NCs) to reveal the characteristic features, which gain interest in the literature. Here, we proposed a new approach for the synthesis of ultra-small hexagonal InN-NCs by using suspension of micron-sized InN powder in ethanol with pulsed laser ablation method. The liquid environment, laser energy and ablation time were optimized and a post-synthesis treatment, centrifugation, was performed to achieve InN-NCs with the smallest size. Besides, the micron-sized InN powder suspension, as a starting material, enabled us to obtain InN-NCs having diameters smaller than 5 nm. We also presented a detailed characterization of InN-NCs and demonstrated that the formation mechanism mainly depends on the fragmentation due to laser irradiation of the suspension. (orig.)

Influence of ablation wavelength and time on optical properties of laser ablated carbon dots

Science.gov (United States)

Isnaeni, Hanna, M. Yusrul; Pambudi, A. A.; Murdaka, F. H.

2017-01-01

Carbon dots, which are unique and applicable materials, have been produced using many techniques. In this work, we have fabricated carbon dots made of coconut fiber using laser ablation technique. The purpose of this work is to evaluate two ablation parameters, which are ablation wavelength and ablation time. We used pulsed laser from Nd:YAG laser with emit wavelength at 355 nm, 532 nm and 1064 nm. We varied ablation time one hour and two hours. Photoluminescence and time-resolved photoluminescence setup were used to study the optical properties of fabricated carbon dots. In general, fabricated carbon dots emit bluish green color emission upon excitation by blue laser. We found that carbon dots fabricated using 1064 nm laser produced the highest carbon dots emission among other samples. The peak wavelength of carbon dots emission is between 495 nm until 505 nm, which gives bluish green color emission. Two hours fabricated carbon dots gave four times higher emission than one hour fabricated carbon dot. More emission intensity of carbon dots means more carbon dots nanoparticles were fabricated during laser ablation process. In addition, we also measured electron dynamics of carbon dots using time-resolved photoluminescence. We found that sample with higher emission has longer electron decay time. Our finding gives optimum condition of carbon dots fabrication from coconut fiber using laser ablation technique. Moreover, fabricated carbon dots are non-toxic nanoparticles that can be applied for health, bio-tagging and medical applications.

Optical wave microphone measurement during laser ablation of Si

Energy Technology Data Exchange (ETDEWEB)

Mitsugi, Fumiaki, E-mail: mitsugi@cs.kumamoto-u.ac.jp [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto, 860-8555 (Japan); Ide, Ryota; Ikegami, Tomoaki [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto, 860-8555 (Japan); Nakamiya, Toshiyuki; Sonoda, Yoshito [Graduate School of Industrial Engineering, Tokai University, 9-1-1 Toroku, Kumamoto, 862-8652 (Japan)

2012-10-30

Pulsed laser irradiation is used for surface treatment of a solid and ablation for particle formation in gas, liquid or supercritical phase media. When a pulsed laser is used to irradiate a solid, spatial refractive index variations (including photothermal expansion, shockwaves and particles) occur, which vary depending on the energy density of the pulsed laser. We focused on this phenomenon and applied an unique method for detection of refractive index variation using an optical wave microphone based on Fraunhofer diffraction. In this research, we analyzed the waveforms and frequencies of refractive index variations caused by pulsed laser irradiation of silicon in air and measured with an optical wave microphone.

Laser ablation: Laser parameters: Frequency, pulse length, power, and beam charter play significant roles with regard to sampling complex samples for ICP/MS analysis

International Nuclear Information System (INIS)

Smith, M.R.; Alexander, M.L.; Hartman, J.S.; Koppenaal, D.W.

1996-01-01

Inductively coupled plasma mass spectrometry is used to investigate the influence of laser parameters with regard to sampling complex matrices ranging from relatively homogenous glasses to multi-phase sludge/slurry materials including radioactive Hanford tank waste. The resulting plume composition caused by the pulsed laser is evaluated as a function of wavelength, pulse energy, pulse length, focus, and beam power profiles. The author's studies indicate that these parameters play varying and often synergistic roles regarding quantitative results. (In a companion paper, particle transport and size distribution studies are presented.) The work described here will illustrate other laser parameters such as focusing and consequently power density and beam power profiles which are shown to influence precision and accuracy. Representative sampling by the LA approach is largely dependent on the sample's optical properties as well as laser parameters. Experimental results indicate that optimal laser parameters; short wavelength (UV), relatively low power (300 mJ), low-to-sub ns pulse lengths, and laser beams with reasonable power distributions (i.e., Gaussian or top-hat beam profiles) provide superior precision and accuracy. Remote LA-ICP/MS analyses of radioactive sludges are used to illustrate these optimal conditions laser ablation sampling

SERS activity of silver and gold nanostructured thin films deposited by pulsed laser ablation

Science.gov (United States)

Agarwal, N. R.; Tommasini, M.; Fazio, E.; Neri, F.; Ponterio, R. C.; Trusso, S.; Ossi, P. M.

2014-10-01

Nanostructured Au and Ag thin films were obtained by nanosecond pulsed laser ablation in presence of a controlled Ar atmosphere. Keeping constant other deposition parameters such as target-to-substrate distance, incidence angle, laser wavelength and laser fluence, the film morphology, revealed by SEM, ranges from isolated NPs to island structures and sensibly depends on gas pressure (10-100 Pa) and on the laser pulse number (500-3 × 10). The control of these two parameters allows tailoring the morphology and correspondingly the optical properties of the films. The position and width of the surface plasmon resonance peak, in fact, can be varied with continuity. The films showed remarkable surface-enhanced Raman activity (SERS) that depends on the adopted deposition conditions. Raman maps were acquired on micrometer-sized areas of both silver and gold substrates selected among those with the strongest SERS activity. Organic dyes of interest in cultural heritage studies (alizarin, purpurin) have been also considered for bench marking the substrates produced in this work. Also the ability to detect the presence of biomolecules was tested using lysozyme in a label free configuration.

Properties of the ablation process for excimer laser ablation of Y1Ba2Cu3O7

International Nuclear Information System (INIS)

Neifeld, R.A.; Potenziani, E.; Sinclair, W.R.; Hill III, W.T.; Turner, B.; Pinkas, A.

1991-01-01

The process of excimer laser ablation has been studied while varying the laser fluence from 0.237 to 19.1 J/cm 2 . Ion time-of-flight, total charge, target etch depth per pulse, and etch volume per pulse have been measured. Results indicate a maximum ablation volume and minimum ionization fraction occur near 5 J/cm 2 . Several of the parameters measured vary rapidly in the 1--5 J/cm 2 range. Variation in these parameters strongly influences the properties of films grown by this technique

Impact of an extended source in laser ablation using pulsed digital holographic interferometry and modelling

Energy Technology Data Exchange (ETDEWEB)

Amer, E., E-mail: eynas.amer@ltu.se [Lulea University of Technology, Department of Applied Physics and Mechanical Engineering, SE-971 87 Lulea (Sweden); Gren, P.; Kaplan, A.F.H.; Sjoedahl, M. [Lulea University of Technology, Department of Applied Physics and Mechanical Engineering, SE-971 87 Lulea (Sweden)

2009-08-15

Pulsed digital holographic interferometry has been used to study the effect of the laser spot diameter on the shock wave generated in the ablation process of an Nd:YAG laser pulse on a Zn target under atmospheric pressure. For different laser spot diameters and time delays, the propagation of the expanding vapour and of the shock wave were recorded by intensity maps calculated using the recorded digital holograms. From the latter, the phase maps, the refractive index and the density field can be derived. A model was developed that approaches the density distribution, in particular the ellipsoidal expansion characteristics. The induced shock wave has an ellipsoid shape that approaches a sphere for decreasing spot diameter. The ellipsoidal shock waves have almost the same centre offset towards the laser beam and the same aspect ratio for different time steps. The model facilitates the derivation of the particle velocity field. The method provides valuable quantitative results that are discussed, in particular in comparison with the simpler point source explosion theory.

Femtosecond laser ablation of enamel

Science.gov (United States)

Le, Quang-Tri; Bertrand, Caroline; Vilar, Rui

2016-06-01

The surface topographical, compositional, and structural modifications induced in human enamel by femtosecond laser ablation is studied. The laser treatments were performed using a Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs and 1030 nm) and fluences up to 14 J/cm2. The ablation surfaces were studied by scanning electron microscopy, grazing incidence x-ray diffraction, and micro-Raman spectroscopy. Regardless of the fluence, the ablation surfaces were covered by a layer of resolidified material, indicating that ablation is accompanied by melting of hydroxyapatite. This layer presented pores and exploded gas bubbles, created by the release of gaseous decomposition products of hydroxyapatite (CO2 and H2O) within the liquid phase. In the specimen treated with 1-kHz repetition frequency and 14 J/cm2, thickness of the resolidified material is in the range of 300 to 900 nm. The micro-Raman analysis revealed that the resolidified material contains amorphous calcium phosphate, while grazing incidence x-ray diffraction analysis allowed detecting traces of a calcium phosphate other than hydroxyapatite, probably β-tricalcium phosphate Ca3), at the surface of this specimen. The present results show that the ablation of enamel involves melting of enamel's hydroxyapatite, but the thickness of the altered layer is very small and thermal damage of the remaining material is negligible.

New application of the long-pulsed Nd-YAG laser as an ablative resurfacing tool for skin rejuvenation: a 7-year study.

Science.gov (United States)

Alshami, Mohammad Ali

2013-09-01

Carbon dioxide (CO2 ) and erbium-yttrium aluminum garnet (Er-YAG) lasers are the gold standards in ablative skin resurfacing. Neodymium-doped yttrium aluminum garnet (Nd-YAG) laser is considered a nonablative skin resurfacing laser whose usage is limited due to its high cost. To assess the efficacy and safety of Nd-YAG as an ablative resurfacing laser and to compare the results with those previously published for CO2 and Erbium-YAG lasers. A total of 296 patients (251 female and 45 male) with Fitzpatrick skin types III-IV and dermatological conditions amenable to ablative skin resurfacing participated in this study. Nd-YAG laser parameters assessed were wavelength (1064 nm), pulse duration (5 ms), fluence (10 J/cm(2) ), and spot size (8-10 mm). Efficacy of Nd-YAG laser was assessed by comparing pre- and posttreatment photographs. An improvement of 30-80% was observed in treated patients. The degree of improvement correlated positively with the number of laser sessions. The most common side effect was hyperpigmentation. Other side effects were less common and mild in intensity compared with published results for gold standard ablative lasers. Not only was the Nd-YAG laser found to be as effective as Er-YAG and CO2 lasers, but treated patients also had shorter recovery and treatment times, and at lower cost. © 2013 Wiley Periodicals, Inc.

Ablation of polymers by ultraviolet pulsed laser

International Nuclear Information System (INIS)

Brezini, A.; Benharrats, N.

1993-08-01

The surface modifications of different polymers treated by far UV-Excimer laser (λ = 193mn, 248, 308nm) are analysed by X-Ray Photoelectrons Spectroscopy. The main feature observed depends strongly on the absorption coefficients. For the high absorbing polymers such (PVC, PS, PI,...) the mechanism of the UV-Excimer Laser interaction appears to be governed by an ablative photodecomposition process (APD) with an APD threshold. In the other limit, i.e. low absorbing polymer the interaction leads to a photothermal process. (author). 51 refs, 24 figs, 7 tabs

CO2-laser ablation of Bi-Sr-Ca-Cu oxide by millisecond pulse lengths

Science.gov (United States)

Meskoob, M.; Honda, T.; Safari, A.; Wachtman, J. B.; Danforth, S.; Wilkens, B. J.

1990-03-01

We have achieved ablation of Bi-Sr-Ca-Cu oxide from single targets of superconducting pellets by CO2-laser pulses of l ms length to grow superconducting thin films. Upon annealing, the 6000-Å thin films have a Tc (onset) of 90 K and zero resistance at 78 K. X-ray diffraction patterns indicate the growth of single-phase thin films. This technique allows growth of uniform single-phase superconducting thin films of lateral area greater than 1 cm2.

A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

International Nuclear Information System (INIS)

See, Tian Long; Liu, Zhu; Li, Lin; Zhong, Xiang Li

2016-01-01

Highlights: • Ablation threshold for excimer laser is lower compared to femtosecond laser. • Effective optical penetration depth for excimer laser is lower compared to femtosecond laser. • Two ablation characteristic regimes are observed for femtosecond laser ablation. • Reduction of C=C bond following excimer or fs laser ablation is observed. • Addition of oxygen- and nitrogen-rich functional groups is observed. - Abstract: This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser–material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (F_t_h = 0.087 J/cm"2) than that for the femtosecond laser ablation of ABS (F_t_h = 1.576 J/cm"2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α"−"1 = 223 nm) than that for femtosecond laser ablation (α"−"1 = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the C=C bond completely through the chain scission process whereas C=C bond is partially

A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

Energy Technology Data Exchange (ETDEWEB)

See, Tian Long, E-mail: tianlong.see@postgrad.manchester.ac.uk [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Liu, Zhu [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Li, Lin [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Zhong, Xiang Li [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom)

2016-02-28

Highlights: • Ablation threshold for excimer laser is lower compared to femtosecond laser. • Effective optical penetration depth for excimer laser is lower compared to femtosecond laser. • Two ablation characteristic regimes are observed for femtosecond laser ablation. • Reduction of C=C bond following excimer or fs laser ablation is observed. • Addition of oxygen- and nitrogen-rich functional groups is observed. - Abstract: This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser–material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (F{sub th} = 0.087 J/cm{sup 2}) than that for the femtosecond laser ablation of ABS (F{sub th} = 1.576 J/cm{sup 2}), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α{sup −1} = 223 nm) than that for femtosecond laser ablation (α{sup −1} = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the C=C bond completely through the chain scission process whereas

Picosecond laser ablation of porcine sclera

Science.gov (United States)

Góra, Wojciech S.; Harvey, Eleanor M.; Dhillon, Baljean; Parson, Simon H.; Maier, Robert R. J.; Hand, Duncan P.; Shephard, Jonathan D.

2013-03-01

Lasers have been shown to be successful in certain medical procedures and they have been identified as potentially making a major contribution to the development of minimally invasive procedures. However, the uptake is not as widespread and there is scope for many other applications where laser devices may offer a significant advantage in comparison to the traditional surgical tools. The purpose of this research is to assess the potential of using a picosecond laser for minimally invasive laser sclerostomy. Experiments were carried out on porcine scleral samples due to the comparable properties to human tissue. Samples were prepared with a 5mm diameter trephine and were stored in lactated Ringer's solution. After laser machining, the samples were fixed in 3% glutaraldehyde, then dried and investigated under SEM. The laser used in the experiments is an industrial picosecond TRUMPF TruMicro laser operating at a wavelength of 1030nm, pulse length of 6ps, repetition rate of 1 kHz and a focused spot diameter of 30μm. The laser beam was scanned across the samples with the use of a galvanometer scan head and various ablation patterns were investigated. Processing parameters (pulse energy, spot and line separation) which allow for the most efficient laser ablation of scleral tissue without introducing any collateral damage were investigated. The potential to create various shapes, such as linear incisions, square cavities and circular cavities was demonstrated.

Stress assisted selective ablation of ITO thin film by picosecond laser

Science.gov (United States)

Farid, Nazar; Chan, Helios; Milne, David; Brunton, Adam; M. O'Connor, Gerard

2018-01-01

Fast selective pattering with high precession on 175 nm ITO thin film with IR ps lasers is investigated. Ablation parameters are optimized with detailed studies on the scribed depth, topography, and particle generation using AFM and SEM. A comparison of 10 and 150 ps laser revealed that the shorter pulse (10 ps) laser is more appropriate in selective and partial ablation; up to 20 nm resolution for controlled depth with multipulses having energy below the damage threshold is demonstrated. The experimental results are interpreted to involve stress assisted ablation mechanism for the 10 ps laser while thermal ablation along with intense melting occurs for 150 ps laser. The transition between these regimes is estimated to occur at approximately 30 ps.

Ultraviolet-laser ablation of skin

Energy Technology Data Exchange (ETDEWEB)

Lane, R.J.; Linsker, R.; Wynne, J.J.; Torres, A.; Geronemus, R.G.

1985-05-01

The authors report on the use of pulsed ultraviolet-laser irradiation at 193 nm from an argon-fluoride laser and at 248 nm from a krypton-fluoride laser to ablate skin. In vitro, both wavelengths performed comparably, removing tissue precisely and cleanly, and leaving minimal thermal damage to the surrounding tissue. In vivo, the 193-nm laser radiation failed to remove tissue after bleeding began. The 248-nm radiation, however, continued to remove tissue despite bleeding and left a clean incision with only minimal thermal damage. The krypton-fluoride excimer laser beam at 248 nm, which should be deliverable through a quartz optical fiber, has great potential as a surgical instrument.

Ultra-fast movies of thin-film laser ablation

Science.gov (United States)

Domke, Matthias; Rapp, Stephan; Schmidt, Michael; Huber, Heinz P.

2012-11-01

Ultra-short-pulse laser irradiation of thin molybdenum films from the glass substrate side initiates an intact Mo disk lift off free from thermal effects. For the investigation of the underlying physical effects, ultra-fast pump-probe microscopy is used to produce stop-motion movies of the single-pulse ablation process, initiated by a 660-fs laser pulse. The ultra-fast dynamics in the femtosecond and picosecond ranges are captured by stroboscopic illumination of the sample with an optically delayed probe pulse of 510-fs duration. The nanosecond and microsecond delay ranges of the probe pulse are covered by an electronically triggered 600-ps laser. Thus, the setup enables an observation of general laser ablation processes from the femtosecond delay range up to the final state. A comparison of time- and space-resolved observations of film and glass substrate side irradiation of a 470-nm molybdenum layer reveals the driving mechanisms of the Mo disk lift off initiated by glass-side irradiation. Observations suggest that a phase explosion generates a liquid-gas mixture in the molybdenum/glass interface about 10 ps after the impact of the pump laser pulse. Then, a shock wave and gas expansion cause the molybdenum layer to bulge, while the enclosed liquid-gas mixture cools and condenses at delay times in the 100-ps range. The bulging continues for approximately 20 ns, when an intact Mo disk shears and lifts off at a velocity of above 70 m/s. As a result, the remaining hole is free from thermal effects.

Laser ablation characteristics of metallic materials: Role of Debye-Waller thermal parameter

International Nuclear Information System (INIS)

Butt, M Z

2014-01-01

The interaction of a high intensity laser pulse with a solid target results in the formation of a crater and a plasma plume. The characteristics of both depend on physical properties of target material, environmental conditions, and laser parameters (e.g. wavelength, pulse duration, energy, beam diameter) etc. It has been shown for numerous metals and their alloys that plasma threshold fluence, plasma threshold energy, ablation efficiency, ablation yield, angular distribution of laser produced plasma (LPP) ions, etc. are a unique function of the Debye-Waller thermal parameter B or the mean-square amplitude of atomic vibration of the target material for given experimental conditions. The FWHM of the angular distribution of LPP ions, ablation yield, and ablation efficiency increase whereas plasma threshold fluence and plasma threshold energy decrease as B-factor of the target material increases