Journal articles: 'Pulses laser femtoseconde'

1

Renard, William, Clément Chan, Antoine Dubrouil, Jérôme Lhermite, Giorgio Santarelli, and Romain Royon. "Agile femtosecond synchronizable laser source from a gated CW laser." Laser Physics Letters 19, no. 7 (May 31, 2022): 075105. http://dx.doi.org/10.1088/1612-202x/ac7133.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Abstract In this letter we demonstrate agile femtosecond pulse generation with a widely tunable repetition rate (10–100 MHz) from a continuous wave laser diode optically gated by a Mach–Zehnder electro-optic intensity modulator. Initial sub-50 ps pulses are strongly spectral broadened (>5 nm) by self-phase modulation in a polarization maintaining single-mode fiber. A tunable optical pulse train with pulse durations of a few hundred femtoseconds is obtained using a simple fixed grating compressor, thanks to spectral broadening saturation phenomena. The source is easily synchronized with low timing jitter using an external clock signal.

2

Li, Zerui. "Analysis of the Principles and Applications of Ultra-intensity and Ultrashort Laser." Highlights in Science, Engineering and Technology 76 (December 31, 2023): 441–49. http://dx.doi.org/10.54097/9s9fm882.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

With the development of laser technology, how to improve the output performance and peak power of lasers has become one of the hot directions of current research. This study analyzes the principles and applications of ultra-intensity and ultrashort pulse laser. It firstly outlines the development history of laser technology and the basic definition of ultra-intensity and ultrashort pulse laser. It also mentions the realization methods for generating ultra-intensity and ultrashort pulse lasers, such as mode-locked femtosecond oscillators and CPA-based femtosecond amplifiers. The paper describes the principles of CPA technique and emphasizes its importance in realizing high power ultrashort pulses. The paper discusses various applications of ultra-intensity and ultrashort pulsed laser and summarizes and discusses the major bottlenecks facing current and future ultra-intensity and ultrashort pulsed lasers and their possible solutions. The technical review in this paper aims to enhance the understanding of ultra-intensity and ultrashort pulsed laser and provide insights into the next phase of research exploration in ultra-intensity and ultrashort pulsed lasers.

3

Tikhomirov, S. A. "Femtosecond System with Pulse Pumping of Seed Laser and Amplifier by Using a Single Power Unit." Devices and Methods of Measurements 12, no. 1 (March 19, 2021): 23–29. http://dx.doi.org/10.21122/2220-9506-2021-12-1-23-29.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

For several decades development of methods for generating ultrashort pulses has been an independent urgent scientific and technical problem. There is a constant improvement both in the methods of such pulses receiving and in methods of their use. The aim of this work was to investigate the possibility of realizing the coordinated operation of two fundamentally different types of pump lasers for the femtosecond oscillator and amplifier based on one single-lamp laser head and to create on this basis a compact high-power femtosecond system with pulsed pumping and one power unit.The practical implementation of two types of pulsed lasers (nano- and picosecond ones operating, respectively, in Q-switch and modelock regime) on a single laser head with two active elements and one pump lamp is carried out. The required synchronization in time the pump pulse femtosecond amplifier formation and quasi-stationary region of generated pulses in the output radiation of a femtosecond Ti:sapphire is obtained.On this basis a compact, pulse pumped monoblock laser system has been developed that can generate femtosecond pulses with a duration of 50–150 fs with an energy up to 1 mJ and a high enough pulse repetition rate (up to 1 kHz which is determined by the type of laser head and pump unit used). In the developed laser system a compact scheme of a stretcher-compressor with a single common diffraction grating is used.Laser systems of this type characterized by a relatively low cost due to the use of a single power supply unit for simultaneous pumping of the amplifier and oscillator, as well as lower requirements for the quality of optical elements and usage conditions due to the pulse mode of operation, are quite practical and can be used both in scientific research in the field of ultra-high-speed kinetic spectroscopy and nonlinear optics, as well as in numerous technical applications, particular in the precision processing of materials, as optical simulators of the action of heavy charged particles in testing the radiation resistance of integrated circuits and electronic modules.

4

Dabu. "Femtosecond Laser Pulses Amplification in Crystals." Crystals 9, no. 7 (July 5, 2019): 347. http://dx.doi.org/10.3390/cryst9070347.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This paper describes techniques for high-energy laser pulse amplification in multi-PW femtosecond laser pulses. Femtosecond laser pulses can be generated and amplified in laser media with a broad emission spectral bandwidth, like Ti:sapphire crystals. By chirped pulse amplification (CPA) techniques, hundred-Joule amplified laser pulses can be obtained. Multi-PW peak-power femtosecond pulses are generated after recompression of amplified chirped laser pulses. The characteristics and problems of large bandwidth laser pulses amplification in Ti:sapphire crystals are discussed. An alternative technique, based on optical parametric chirped pulse amplification (OPCPA) in nonlinear crystals, is presented. Phase-matching conditions for broad bandwidth parametric amplification in nonlinear crystals are inferred. Ultra-broad phase matching bandwidth of more than 100 nm, able to support the amplification of sub-10 fs laser pulses, are demonstrated in nonlinear crystals, such as Beta Barium Borate (BBO), Potassium Dideuterium Phosphate (DKDP), and Lithium Triborate (LBO). The advantages and drawbacks of CPA amplification in laser crystals and OPCPA in nonlinear crystals are discussed. A hybrid amplification method, which combines low-medium energy OPCPA in nonlinear crystals with high energy CPA in large aperture laser crystals, is described. This technique is currently used for the development of 10-PW laser systems, with sub-20 fs pulse duration and more than 1012 intensity contrast of output femtosecond pulses.

5

Zeng, Li, Xiaofan Wang, Yifan Liang, Huaiqian Yi, Weiqing Zhang, and Xueming Yang. "Chirped-Pulse Amplification in an Echo-Enabled Harmonic-Generation Free-Electron Laser." Applied Sciences 13, no. 18 (September 14, 2023): 10292. http://dx.doi.org/10.3390/app131810292.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The field of ultrafast science has experienced significant growth over the last decade, largely attributed to advancements in optical and laser technologies such as chirped-pulse amplification and high-harmonic generation. The distinctive characteristics of intense ultrafast free-electron lasers (FELs) have introduced novel prospects for investigating molecular dynamics, as well as providing an opportunity to gain deeper insights into nonlinear processes in materials. Therefore, high-power ultrafast FELs can be widely used for both fundamental research and practical applications. This study presents a novel approach for producing high-power femtosecond FEL pulses, utilizing chirped-pulse amplification in echo-enabled harmonic generation. Chirped seed pulses are employed to induce frequency-chirped energy modulation in the electron beam. The generated FEL pulse, which inherits the chirped frequency, can be compressed through the gratings in the off-plane mount geometry to provide ultraintense ultrafast pulses. The numerical modeling results indicate that peak power exceeding 20 GW and a pulse duration in the order of several femtoseconds can be achieved.

6

Ye, Hanyu, Florian Leroy, Lilia Pontagnier, Giorgio Santarelli, Johan Boullet, and Eric Cormier. "Non-linear amplification to 200 W of an electro-optic frequency comb with GHz tunable repetition rates." EPJ Web of Conferences 287 (2023): 07025. http://dx.doi.org/10.1051/epjconf/202328707025.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

We present a monolithic Yb-doped fiber laser system delivering 200 W average power of femtosecond pulses at tunable GHz repetition rates. The system is based on a GHz electro-optic (EO) frequency comb operating in the nonlinear regime. The EO comb pulses at 1 µm wavelength are initially pre-compressed to sub-2 ps, amplified to 2.5 W, and finally boosted to 200 W in a newly designed large-mode-area, Yb-doped photonic crystal fiber. Continuously tunable across 1-18 GHz, the picosecond pulses experience nonlinear propagation in the booster amplifier, leading to output pulses compressible down to several hundreds of femtoseconds. To push our system deeper into the nonlinear amplification regime, the pulse repetition rate is further reduced to 2 GHz, enabling significant spectral broadening at 200 W. Characterization reveals sub-200 fs duration after compression. The present EO-comb seeded nonlinear amplification system opens a new route to the development of high-power, tunable GHz-repetition-rate, femtosecond fiber lasers.

7

Obata, Kotaro, Francesc Caballero-Lucas, Shota Kawabata, Godai Miyaji, and Koji Sugioka. "GHz bursts in MHz burst (BiBurst) enabling high-speed femtosecond laser ablation of silicon due to prevention of air ionization." International Journal of Extreme Manufacturing 5, no. 2 (April 11, 2023): 025002. http://dx.doi.org/10.1088/2631-7990/acc0e5.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Abstract For the practical use of femtosecond laser ablation, inputs of higher laser intensity are preferred to attain high-throughput material removal. However, the use of higher laser intensities for increasing ablation rates can have detrimental effects on ablation quality due to excess heat generation and air ionization. This paper employs ablation using BiBurst femtosecond laser pulses, which consist of multiple bursts (2 and 5 bursts) at a repetition rate of 64 MHz, each containing multiple intra-pulses (2–20 pulses) at an ultrafast repetition rate of 4.88 GHz, to overcome these conflicting conditions. Ablation of silicon substrates using the BiBurst mode with 5 burst pulses and 20 intra-pulses successfully prevents air breakdown at packet energies higher than the pulse energy inducing the air ionization by the conventional femtosecond laser pulse irradiation (single-pulse mode). As a result, ablation speed can be enhanced by a factor of 23 without deteriorating the ablation quality compared to that by the single-pulse mode ablation under the conditions where the air ionization is avoided.

8

Li, DongCheng. "Femtosecond pulsed laser technology and applications." Theoretical and Natural Science 28, no. 1 (December 26, 2023): 166–73. http://dx.doi.org/10.54254/2753-8818/28/20230347.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This paper describes femtosecond pulsed laser technology and related applications. The focus is on two core femtosecond pulsed laser technologies: femtosecond pulsed laser generation and amplification. In the generation of femtosecond pulsed lasers, mode-locking techniques, Kerr-lens mode-locking, and semiconductor saturable absorber mirrors are presented; in the amplification of femtosecond pulsed lasers, chirped-pulse amplification and coherent synthesis techniques are presented. This paper analyses the applications of femtosecond pulsed lasers in both the biomedical and manufacturing sectors and gives the development trends as well as the challenges of femtosecond laser technology. Femtosecond lasers are now used in a wide range of applications. Femtosecond pulsed lasers will develop in the directions of high power, miniaturisation, intelligence and precision. Laser tweezers will become the new direction of development in the future.

9

Takubo, Kou, Samiran Banu, Sichen Jin, Misaki Kaneko, Wataru Yajima, Makoto Kuwahara, Yasuhiko Hayashi, et al. "Generation of sub-100 fs electron pulses for time-resolved electron diffraction using a direct synchronization method." Review of Scientific Instruments 93, no. 5 (May 1, 2022): 053005. http://dx.doi.org/10.1063/5.0086008.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

To investigate photoinduced phenomena in various materials and molecules, ultrashort pulsed x-ray and electron sources with high brightness and high repetition rates are required. The x-ray and electron’s typical and de Broglie wavelengths are shorter than lattice constants of materials and molecules. Therefore, photoinduced structural dynamics on the femtosecond to picosecond timescales can be directly observed in a diffraction manner by using these pulses. This research created a tabletop ultrashort pulsed electron diffraction setup that used a femtosecond laser and electron pulse compression cavity that was directly synchronized to the microwave master oscillator (∼3 GHz). A compressed electron pulse with a 1 kHz repetition rate contained 228 000 electrons. The electron pulse duration was estimated to be less than 100 fs at the sample position by using photoinduced immediate lattice changes in an ultrathin silicon film (50 nm). The newly developed time-resolved electron diffraction setup has a pulse duration that is comparable to femtosecond laser pulse widths (35–100 fs). The pulse duration, in particular, fits within the timescale of photoinduced phenomena in quantum materials. Our developed ultrafast time-resolved electron diffraction setup with a sub-100 fs temporal resolution would be a powerful tool in material science with a combination of optical pump–probe, time-resolved photoemission spectroscopic, and pulsed x-ray measurements.

10

Zhu, Chang Jun, Bing Xue, Xue Jun Zhai, and Jun Fang He. "Manufacture of Lasers with Multiple Operating Modes." Advanced Materials Research 482-484 (February 2012): 1937–40. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.1937.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

A two-beam pumped Ti:sapphire laser with femtosecond and picosecond cavities was manufactured. Three operating modes, independent self mode-locking, cross mode-locking and multi-pulse operating, were achieved. In the independent self mode-locking mode, femtosecond and picosecond laser pulses were generated in the two cavities, respectively. In the cross mode-locking mode, synchronized femtosecond and picosecond laser pulses were obtained in the two cavities. In the multi-pulse mode, multi-pulses were produced in the picosecond cavity. The results show that, the independent self mode-locking mode is dominated mainly by group velocity dispersion and self-phase modulation, the cross mode-locking mode is governed primarily by cross-phase modulation and the multi-pulse operating is ruled largely by self-amplitude modulation.

11

Zhao, Lu, Antoine Normand, Jonathan Houard, Ivan Blum, Fabien Delaroche, Olivier Latry, Blaise Ravelo, and Francois Vurpillot. "Optimizing Atom Probe Analysis with Synchronous Laser Pulsing and Voltage Pulsing." Microscopy and Microanalysis 23, no. 2 (February 8, 2017): 221–26. http://dx.doi.org/10.1017/s1431927616012666.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

AbstractAtom probe has been developed for investigating materials at the atomic scale and in three dimensions by using either high-voltage (HV) pulses or laser pulses to trigger the field evaporation of surface atoms. In this paper, we propose an atom probe setup with pulsed evaporation achieved by simultaneous application of both methods. This provides a simple way to improve mass resolution without degrading the intrinsic spatial resolution of the instrument. The basic principle of this setup is the combination of both modes, but with a precise control of the delay (at a femtosecond timescale) between voltage and laser pulses. A home-made voltage pulse generator and an air-to-vacuum transmission system are discussed. The shape of the HV pulse presented at the sample apex is experimentally measured. Optimizing the delay between the voltage and the laser pulse improves the mass spectrum quality.

12

Zhu, Chang Jun, Jun Fang He, Xue Jun Zhai, Bing Xue, and Chong Hui Zhang. "Two Synchronized Operating Modes of Femtosecond and Picosecond Pulses in a Dual-Wavelength Laser." Materials Science Forum 663-665 (November 2010): 284–87. http://dx.doi.org/10.4028/www.scientific.net/msf.663-665.284.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Two synchronized operating modes of femtosecond and picosecond pulses, cross mode-locking and multi-pulse operating, are presented in a two-beam-pumped dual-wavelength Ti:sapphire laser. For the cross mode-locking mode, synchronized laser pulses of 37.5 fs and 0.891ps, with a timing jitter of 139 fs, are obtained in the femtosecond cavity and picosecond cavity, respectively. For the multi-pulse mode, pulses of 35 fs are obtained in the femtosecond cavity, whereas, multi-pulse mode appears in the picosecond cavity, with a pulse envelope width of 1.06 ps. The two operating modes can be switched from one to the other, dominated mainly by the mutual interaction between cross-phase modulation and self-amplitude modulation.

13

Salguero Gómez, Jorge, Marcelo Romero, Irene Del Sol, Moises Batista, and Juan Manuel Vazquez Martinez. "Influence of Power and Frequency in the Femtosecond Laser Texturing of Ti6Al4V." Key Engineering Materials 955 (September 27, 2023): 33–41. http://dx.doi.org/10.4028/p-k8yhy3.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Laser Surface Texturing (LST) has demonstrated to be the most reliable technique for the micro-modification of surfaces, allowing to obtain taylored surfaces. These modifications, depending on the basic micro-geometry and its repetition pattern, can provide special functionalities to a surface, such as hydrophilicity, hydrophobicity, reflectance, anti-bacterial, ostheo-integrability, as well as custom aesthetic, among others.Nevertheless, when a laser irradiates metallic surfaces, the micro-structure can be modified due to the heat induced, changing the mechanical properties of the surface. To avoid these effects, cold or ultra-short pulsed lasers must be used.A cold laser emits optical pulses with a duration below 1 ps (ultra-short pulses), in the domain of femtoseconds (fs=10-15 s). These ultra-short pulses, combined with high frequencies, in the megahertz region, leads to pulse trains with high repetition rates. This allows the sublimation of the material, keeping it relatively cold due to the short exposition time to irradiation.Ti6Al4V is the most used Ti alloy, thanks to its excellent weight/mechanical properties ratio. Nevertheless, its tribological behavior is very poor. Although there is intense research to improve it by using LST, the study of the influence of femtosecond laser parameters in the desired micro-geometries is still a gap in the scientific literature.In this research, a study of the influence of power (up to 50 W) and frequency (up to 2 MHz) in the fs-laser texturing of Ti6Al4V is presented. Local pulse repetition, linear and surface textures have been studied by combining power and frequency in these ranges, evaluating the geometry obtained by variable focus microscopy. The study carried out has allowed to determine the optimal set of parameters as a function on the target texture geometry, as well as the range in which the LST removal process changes from sublimation (for texturing) to melting (for micro-machining).

14

Chen, Gao. "Isolated attosecond pulse generation from helium atom irradiated by a three-color laser pulse." Acta Physica Sinica 71, no. 5 (2022): 054204. http://dx.doi.org/10.7498/aps.71.20211502.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Isolated attosecond pulses enables the studying and controlling of ultrafast electron processes in atoms and molecules. High-order harmonic generation (HHG) is the most promising way to generate such pulses, benefiting from the broad plateau structure of the typical HHG spectrum. We theoretically investigate high-order harmonic and attosecond pulse generation from helium atom in a three-color laser field, which is synthesized by 16 fs/1600 nm, 15 fs/1100 nm and 5 fs/800 nm pulse laser. Compared with harmonic spectrum generated by a two-color laser field synthesized by 16 fs/1600 nm and 15 fs/1100 nm, the harmonic spectrum generated from the synthesized three-color field exhibits high conversion efficiency and broadband supercontinuum characteristics. The continuous spectrum range covers from 230th to 690th harmonics, and the generation of 128 attosecond isolated short pulses with higher intensity is realized after Fourier transform. This result is attributable to the fact that the synthesized three-color electric field exhibits high-intensity and few-cycle mid-infrared femtosecond pulse laser characteristics, which can effectively control atomic ionization and recombination occurring within an effective optical period of the mid-infrared femtosecond pulse. This scheme solves the problems faced by the current femtosecond pulse laser technology, i.e. the few-cycle mid-infrared femtosecond pulse laser cannot have both carrier envelope phase stability and high power output.

15

Ghaforyan, H., R. Sadighi-Bonabi, and E. Irani. "The Effect of Chirped Intense Femtosecond Laser Pulses on the Argon Cluster." Advances in High Energy Physics 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/2609160.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The interaction of intense femtosecond laser pulses with atomic Argon clusters has been investigated by using nanoplasma model. Based on the dynamic simulations, ionization process, heating, and expansion of a cluster after irradiation by femtosecond laser pulses at intensities up to 2×1017 Wcm−2are studied. The analytical calculation provides ionization rate for different mechanisms and time evolution of the density of electrons for different pulse shapes. In this approach, the strong dependence of laser intensity, pulse duration, and laser shape on the electron energy, the electron density, and the cluster size is presented using the intense chirped laser pulses. Based on the presented theoretical modifications, the effect of chirped laser pulse on the complex dynamical process of the interaction is studied. It is found that the energy of electrons and the radius of cluster for the negatively chirped pulses are improved up to 20% in comparison to the unchirped and positively chirped pulses.

16

Bibicheva S. A., Rupasov A. E., Danilov P. A., Ionin N. A., Smirnov N. A, Kudryashov S. N., Shelygina R. A., and Zakoldaev R. A. "Self-organizing half-wave gratings on the surface of silica glass." Optics and Spectroscopy 130, no. 4 (2022): 437. http://dx.doi.org/10.21883/eos.2022.04.53732.58-21.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The interaction of femtosecond laser pulses with the surface of silica glass has been studied. As a result of interference between the incident radiation and surface plasmon polaritons, the formation of self-organizing subwavelength periodic structures with a period of 250 nm was observed. The minimum pulse energy at which recording occurs without surface ablation has been revealed. Keywords: direct laser recording, femtosecond laser pulses, silica, nanogratings.

17

Lu, Qi, Xiang Zhang, Arnaud Couairon, and Yi Liu. "Revealing Local Temporal Profile of Laser Pulses of Intensity above 1014 W/cm2." Sensors 23, no. 6 (March 14, 2023): 3101. http://dx.doi.org/10.3390/s23063101.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

We demonstrated a method for in situ temporal characterization of an intense femtosecond laser pulse around its focus where the laser intensity exceeds 1014 W/cm2. Our method is based on the second harmonic generation (SHG) by a relatively weak femtosecond probe pulse and the intense femtosecond pulses under analysis in the gas plasma. With the increase in the gas pressure, it was found that the incident pulse evolves from a Gaussian profile to a more complicated structure featured by multiple peaks in the temporal domain. Numerical simulations of filamentation propagation support the experimental observations of temporal evolution. This simple method can be applied to many situations involving femtosecond laser–gas interaction, when the temporal profile of the femtosecond pump laser pulse with an intensity above 1014 W/cm2 cannot be measured in traditional ways.

18

Jana, Kamalesh, Amit D. Lad, Ankit Dulat, Yash M. Ved, and G. Ravindra Kumar. "Ultrafast time-resolved two-dimensional velocity mapping of the hot-dense plasmas generated by intense-laser pulses." AIP Advances 12, no. 9 (September 1, 2022): 095112. http://dx.doi.org/10.1063/5.0102048.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Experimental measurements of spatially resolved ultrafast dynamics of the critical surface in ultra-intense laser–solid interactions are essential for a proper understanding of the physical mechanism of the interaction. Resolving ultrafast motion at both the relevant length scales (micrometers) and timescales (femtoseconds) simultaneously has been a challenging task. Here, we demonstrate a novel technique for mapping the spatiotemporal dynamics of hot and solid dense plasma created by high contrast (picosecond contrast ∼10−9) femtosecond relativistic intensity laser pulses. This pump–probe Doppler spectrometry technique offers hundreds of femtosecond temporal resolution, together with a few micrometer spatial resolution across the transverse profile of the plasma. We present the evolution of the plasma surface critical for the probe pulse at the target front as well as the rear. Early time measurements ([Formula: see text] 5 ps) using this technique provide very important information about shock wave generation and propagation and the state of the target rear.

19

Wang, Huai Sheng. "The Temporal Diffraction Characteristic of a Femtosecond Laser Pulse by a Serrated Aperture." Applied Mechanics and Materials 268-270 (December 2012): 1353–56. http://dx.doi.org/10.4028/www.scientific.net/amm.268-270.1353.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Based on Fresnel diffraction theory we give out the light field distribution for the definite frequency component of a femtosecond laser pulse when the laser pulse passes through a serrated aperture. Through an inverse Fourier transformation, we get the temporal diffraction field function of the femtosecond laser pulse at any distance. The temporal diffraction field function is related to the width of the laser pulse, the structure of the serrated aperture, the Fresnel number at central frequency and time. Number calculation shows when the width of the laser pulse is within a few tens of femtoseconds and Fresnel number at central frequency is much, the temporal diffraction intensity is not a Gaussian distribution. Nevertheless when Fresnel number at central frequency is less than ten, the temporal diffraction intensity can be approximately regarded as a Gaussian distribution and has a time delay effect.

20

Sano, Tomokazu, Kengo Takahashi, Akio Hirose, and Kojiro F. Kobayashi. "Femtosecond Laser Ablation of Zr₅₅Al₁₀Ni₅Cu₃₀ Bulk Metallic Glass." Materials Science Forum 539-543 (March 2007): 1951–54. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.1951.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Dependence of the femtosecond laser ablation depth on the laser pulse energy was investigated for Zr55Al10Ni5Cu30 bulk metallic glass. Investigation of the femtosecond laser ablation of bulk metallic glasses has not been reported. Femtosecond laser pulses (wavelength of 800 nm, pulse width of 100 fs, pulse energies of 2 – 900 μJ) were focused and irradiated on the polished surface of metals in air. The ablation depth of the metallic glass is deeper than that of its crystallized metal at a pulse energy in the strong ablation region. We suggest that the energy loss at grain boundaries of hot electrons which is accelerated by the laser electric field influence the ablation depth in the strong ablation region.

21

Zhang, Luwei, Xiaodong Jia, Yunzhe Wang, Yin Zhang, Anmin Chen, Junfeng Shao, and Changbin Zheng. "Effect of Femtosecond Laser Polarization on the Damage Threshold of Ta2O5/SiO2 Film." Applied Sciences 12, no. 3 (January 30, 2022): 1494. http://dx.doi.org/10.3390/app12031494.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The study used linearly and circularly polarized femtosecond pulsed lasers to irradiate a Ta2O5/SiO2 film. Firstly, the damage thresholds of the film for linearly and circularly polarized femtosecond pulsed lasers were measured in 1-on-1 mode. The results showed that the damage threshold (1.70 J/cm2) under a circularly polarized laser was higher than that (1.68 J/cm2) under a linearly polarized laser. For femtosecond lasers, the multi-photon ionization cross-section under circular polarization was lower than that under linear polarization. The lower ionization rate under circular polarization led to a higher damage threshold compared to the case under linear polarization. Secondly, the damage morphology of the film irradiated by linearly and circularly polarized femtosecond lasers was observed by microscope. The damage caused by linearly polarized laser was more evident than that caused by the circularly polarized laser. Finally, the damage thresholds induced by linearly and circularly polarized femtosecond pulsed lasers were measured in S-on-1 (S = 2, 5, and 10) mode. For the same S value (2, 5, or 10), the damage threshold under the circularly polarized laser was higher than that under the linearly polarized laser. The damage thresholds under two polarized laser pulses decreased with an increase in the number of laser shots, indicating that repeated laser pulses had a cumulative effect on the damage of the film.

22

Qi, Li Tao, and Jin Ping Hu. "Experimental Investigation on Femtosecond Laser Ablation of Polycarbonate." Advanced Materials Research 652-654 (January 2013): 2359–62. http://dx.doi.org/10.4028/www.scientific.net/amr.652-654.2359.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

In this paper, experimental investigations on femtosecond laser (pulse duration:164 fs, wavelength:780 nm) micromachining of polycarbonate have been carried out in air. The lateral and vertical machining precision was evaluated by scanning electron microscopy and profilometer. The morphological changes were observed by scanning electron microscopy. The ablation mechanism varied with the laser pulse energy was discussed. The diameter and depth of the ablated crated are influenced by the laser pulse energy and the number of laser pulses. The relation between the diameter and ablation depth of the crater and the key parameters of femtosecond laser is obtained. Femtosecond laser micromachining of polycarbonate have a potential application of the fabrication of polycarbonate-based devices.

23

Mir, Hanan, Fabian Meyer, Andreas A. Brand, Katrin Erath-Dulitz, and Jan Frederik Nekarda. "Study of GHz-Burst Femtosecond Laser Micro-Punching of 4H-SiC Wafers." Solid State Phenomena 344 (June 6, 2023): 29–33. http://dx.doi.org/10.4028/p-q6725d.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The micromaching of silicon carbide using femtosecond laser pulses is becoming an important field of research. High-repetition-rate sub-pulse trains, so-called pulse bursts, are a particularly promising route towards completely new process regimes. We report on the results of micro-punching n-type 4H-silicon carbide wafers using GHz pulse burst in order to systematically investigate the influence of the temporal energy distribution on laser processing. Pulse-burst experiments are performed at a laser wavelength of λ= 1030 nm using a single GHz burst containing a varying number of pulses and then compared with standard single femtosecond pulse exposures. The pulse energy is swept across the ablation threshold. For each set of parameters, the micromachining efficiency is evaluated in terms of ablation efficiency and burr characteristics. Scanning electron micrographs provide qualitative information about the machining quality. The characteristics of the laser modification are discussed in relation to an increase in the number of pulses in a burst envelope and to an increase in pulse energy. We observe that, compared to a single pulse, a GHz burst comprised of 10 lower-energy pulses leads to an increase in the ablation rate by a factor of ≤ 10.

24

Sitnikov, Dmitry S., Maxim A. Filatov, and Inna V. Ilina. "Optimal Exposure Parameters for Microsurgery of Embryo Zona Pellucida Using Femtosecond Laser Pulses." Applied Sciences 13, no. 20 (October 12, 2023): 11204. http://dx.doi.org/10.3390/app132011204.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

We applied femtosecond laser pulses for microsurgery of the zona pellucida (ZP) of mouse embryos in terms of assisted reproductive technologies. The embryos were subjected to a series of laser pulses (wavelength of 514 nm, pulse duration of 280 fs, repetition rate of 2.5 kHz). Optical microscopy was used to study the dependence of the ZP cut width on the pulse energy E and velocity v of the laser beam. It is shown that the same value of the cut width can be obtained for different combinations of these parameters. The boundaries of admissible values were found to be E = (19–52) nJ, v = (0.001–0.03) mm/s; recommendations on their proper choice are given. An analytical expression of the cut width of the ZP for a given combination of laser-pulse energy, beam velocity, and pulse repetition rate is proposed. This simple and easy-to-use equation allows for quick prediction of ZP cut width in embryo microsurgery procedures of laser-assisted hatching and embryo laser tagging using femtosecond laser pulses.

25

Shaheen, Mohamed E., and Brian J. Fryer. "Femtosecond laser ablation of brass: A study of surface morphology and ablation rate." Laser and Particle Beams 30, no. 3 (July 10, 2012): 473–79. http://dx.doi.org/10.1017/s0263034612000407.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

AbstractThe interaction of near infrared femtosecond laser pulses with a Cu based alloy (brass) in ambient air at atmospheric pressure and under different laser conditions was investigated. The effects of laser fluence and number of pulses on surface morphology and ablation rate were studied using scanning electron microscopy (SEM) and optical microscopy. Ablation rates were found to rapidly increase from 83 to 604 nm/pulse in the fluence range 1.14–12.21 J/cm2. At fluence >12.21 J/cm2, ablation rates increased slowly to a maximum (607 nm/pulse at 19.14 J/cm2), and then decreased at fluence higher than 20.47 J/cm2 to 564 nm/pulse at 24.89 J/cm2. Large amounts of ablated material in a form of agglomerated fine particles were observed around the ablation craters as the number of laser pulses and fluence increased. The study of surface morphology shows reduced thermal effects with femtosecond laser ablation in comparison to nanosecond laser ablation at low fluence.

26

Kuzmin E. V. and Klekovkin A.V. "Features of structuring and ablation of thin titanium films by femtosecond laser pulses." Optics and Spectroscopy 130, no. 4 (2022): 412. http://dx.doi.org/10.21883/eos.2022.04.53727.66-21.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The processes of structuring and ablation of a titanium film by femtosecond laser pulses at wavelengths of 515 nm and 1030 nm have been studied in both single-pulse and multi-pulse modes. The optimal energy regimes for the selective removal of film material without damaging the substrate, as well as the regimes for the generation of the periodic structures on the surface, are determined. The evolution of periodic structures with an increase in the number of laser pulses is shown. The precision removal of titanium film is associated with thermomechanical explosive boiling and the corresponding energy contribution, which ensures the cascade appearance of ablation craters.. Keywords: thin films, femtosecond laser pulses, surface treatment

27

JIANG, YUQIANG, CUNGEN MA, ISAMU OH, YOICHIROH HOSOKAWA, and HIROSHI MASUHARA. "SECONDARY CONVERGENCE IN FEMTOSECOND LASER TRAPPING." Modern Physics Letters B 24, no. 16 (June 30, 2010): 1739–46. http://dx.doi.org/10.1142/s0217984910024110.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

When femtosecond laser pulses pass through a trapped polystyrene bead, water breakdown is induced even though the energy of laser pulse is much lower compared to the threshold value of breakdown when the femtosecond laser directly irradiates in water. This mechanism is assigned to the secondary convergence of the laser by the trapped bead.

28

SCHMIDT, M., P. D'OLIVEIRA, P. MEYNADIER, D. NORMAND, and C. CORNAGGIA. "STRONG LASER FIELD INTERACTION WITH DIATOMIC MOLECULES: FROM THE ULTRA-SHORT TO LONG-PULSE REGIME." Journal of Nonlinear Optical Physics & Materials 04, no. 04 (October 1995): 817–29. http://dx.doi.org/10.1142/s0218863595000367.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

In the present paper, we compare novel MEDI results on iodine obtained with 30 ps laser pulses to those obtained in the femtosecond regime. The results indicate laser-induced trapping of the molecules not only in the ultra-short pulse regime, but also for the long pulses, since the fragment kinetic energy releases are essentially the same, although the pulse duration is varied over more than two orders of magnitude. Most interestingly, with 30 ps pulses significant post-dissociation ionization of the In+-fragments observed for the first time, proving that near-Coulomb energies and post-dissociation ionization can be observed simultaneously. A femtosecond double-pulse experiment confirms our recent hypothesis of molecular stabilization governing the MEDI interaction.

29

GUO, ZHONGYI, WEIQIANG DING, SHILIANG QU, JINGMIN DAI, and SHUTIAN LIU. "SELF-ASSEMBLED VOLUME GRATING IN SILICA GLASS INDUCED BY TIGHTLY FOCUSED FEMTOSECOND LASER PULSE." Journal of Nonlinear Optical Physics & Materials 18, no. 04 (December 2009): 625–32. http://dx.doi.org/10.1142/s0218863509004841.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

We report on self-assembled volume grating in silica glass induced by a tightly focused femtosecond laser pulse. The formation of volume grating is attributed to the multiple microexplosion in the transparent materials induced by the femtosecond pulses. The first order diffractive efficiency is greatly dependent on the energy of the pulses and the scanning velocity of the laser, and the highest reaches to nearly 30%.

30

Wang Shixiang, 王士香, 陈志翔 Chen Zhixiang, 刘洪亮 Liu Hongliang, 任莹莹 Ren Yingying, 孙晓莉 Sun Xiaoli, 贾曰辰 Jia Yuechen, and 陈峰 Chen Feng. "飞秒激光直写Tm∶YAP波导脉冲激光器." Acta Optica Sinica 43, no. 16 (2023): 1623018. http://dx.doi.org/10.3788/aos230859.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Balachninaitė, O., J. Skruibis, A. Matijošius, and V. Vaičaitis. "Temporal and spatial properties of plasma induced by infrared femtosecond laser pulses in air." Plasma Sources Science and Technology 31, no. 4 (April 1, 2022): 045001. http://dx.doi.org/10.1088/1361-6595/ac5c62.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Abstract Space and time-resolved electron density and temperature of the plasma, created in air by focused femtosecond laser pulses have been investigated as a function of the pump pulse energy and duration. For the air ionization the infrared (1030 nm) femtosecond (190–500 fs) Yb:KGW laser pulses of up to 1 mJ energy were used. Based on the Stark broadening of the oxygen-I 777.19 nm line we have found that after establishing a local equilibrium the density of laser-created plasma could exceed 1017 cm−3 with the electron temperature of over 5000 °C. Obtained results agree well with the results of previously reported measurements of the plasma density created by the femtosecond near-infrared Ti:sapphire laser pulses.

32

Zhu, Jianqiang, Xinglong Xie, Meizhi Sun, Qunyu Bi, and Jun Kang. "A Novel Femtosecond Laser System for Attosecond Pulse Generation." Advances in Optical Technologies 2012 (January 15, 2012): 1–6. http://dx.doi.org/10.1155/2012/908976.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA). The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50 mm is used instead of the KDP crystal as the gain medium to ensure the shortest pulse. After the completion, the laser will deliver about 8 J with pulse duration of about 10 femtoseconds, which should be beneficial to the attosecond pulse generation and other ultrafast experiments.

33

Qi, Li Tao, and Jin Ping Hu. "Femtosecond Laser Micromachining of High Quality Groove on Sapphire Surface." Applied Mechanics and Materials 217-219 (November 2012): 2213–16. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.2213.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

In this paper, high quality grooves were fabricated by femtosecond laser pulse on sapphire surface. Grooves were fabricated under different experimental conditions. The lateral and vertical machining precision was evaluated by scanning electron microscopy and profilometer. High quality grooves could be obtained at the condition of low pulse energy, high scanning-speed and increasing the number of laser scans. The relationship between the width and depth of the groove and the key parameters of femtosecond laser micromachining system was studied. Several samples of the high quality grooves were obtained by femtosecond laser pulses. High quality grooves have a potential application of the fabrication of sapphire-based devices.

34

Nedyalkov, N., A. Dikovska, T. Dilova, and G. Atanasova. "Influence of the pulse duration at the laser processing of nitride ceramics." Journal of Physics: Conference Series 2710, no. 1 (February 1, 2024): 012014. http://dx.doi.org/10.1088/1742-6596/2710/1/012014.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Abstract This paper presents results on laser ablation of AlN and Si3N4 ceramics by laser pulses with different duration. Three types of laser systems, a Nd:YAG one, operated at wavelength of 1064 nm and pulse duration of 15 ns, a Nd:YAG, operated at wavelength of 1064 nm and pulse duration of 10 ps, and a femtosecond laser system, operated at 800 nm, with a pulse duration of 75 fs, are used for experiments. Details on the ablation efficiency, surface morphology, and the chemical composition of the irradiated zones as a function of the pulse duration are given and discussed. It is demonstrated that the ablation rate (ablation depth per pulse) is highest for processing with nanosecond pulses and it is lowest for the femtosecond regime. The laser ablation results in significant change of the surface morphology, as its characteristics are influenced by the pulse duration. For all pulse durations conditions for formation of ripples structures are found. The ablation process is realized by decomposition of the ceramics and the composition of the remaining surface layer is governed by oxidation and carbonization.

35

Nan, Junyi, Min Li, Ling Zhang, Shuai Yuan, Boqu He, and Heping Zeng. "Terahertz and Photoelectron Emission from Nanoporous Gold Films on Semiconductors." Nanomaterials 9, no. 3 (March 12, 2019): 419. http://dx.doi.org/10.3390/nano9030419.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Efficient terahertz and photoelectron emission were observed from nano-porous gold (NPG) films deposited on an intrinsic gallium arsenide (GaAs) semiconductor substrate stimulated by femtosecond laser with pulse width of 60 fs. Time-domain THz emission and reflection spectroscopy confirmed that the free charges accelerated by irradiated femtosecond laser pulses transferred from the NPG films into the GaAs substrates. Accordingly, charges accumulation was reduced in the NPG films, resulting in a stronger emission of THz pulse than that from NPG films deposited on SiO2 substrate. Charges injected into the GaAs substrate enforced an observable decrease of the THz refractive index proportional to the intensity of incident light. In comparison, for NPG deposited on glass substrates, laser induced free charges were accumulated in the NPG films, and femtosecond laser pulses irradiating on the NPG films made no changes of the THz refractive index of the glass substrates.

36

Wang, Fengdie, Zhonghai Wang, Yuchi Wu, Shaoyi Wang, Yonghong Yan, Minghai Yu, Xiaohui Zhang, et al. "An active dose-measuring device for X-rays generated by ultra-short, ultra-intense laser pulses." Journal of Instrumentation 18, no. 03 (March 1, 2023): P03005. http://dx.doi.org/10.1088/1748-0221/18/03/p03005.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Abstract Ultra-short, ultra-intense laser pulses can create extreme physical conditions for a wide range of applications in atomic and molecular physics, materials chemistry, and inertial-confinement fusion. However, laser-matter interactions can be accompanied by significant X-ray emission that introduces radiation risks to the nearby environment and personnel. It is usually to monitor the radiation dose during in high-intensity laser-target interactions with optically stimulated luminescence and thermo-luminescence devices. However, these passive methods cannot measure the radiation dose in real time, while most active dosimeters cannot accurately measure pulsed radiation doses. Here, transient pulse X-ray radiation doses are converted by CdWO4 crystals into slow signals. Because the crystals have a 14-μs luminescence decay time, they can absorb sub-nanosecond X-ray pulses and release the energy at a 100-μs rate, thus reducing the linear-response pressure of subsequent devices. A pulse detector based on a CdWO4 crystal, a phototube, and a custom signal-processing circuit was developed. Experiments were performed at the 45-TW femtosecond laser facility of the Laser Fusion Research Center. The detector deviation was less than ±20% relative to that of an ionization-chamber detector. This initially verified its feasibility for real-time pulsed X-ray radiation detection.

37

Liu, Yongshan, Houyi Cheng, Pierre Vallobra, Huiwen Wang, Sylvain Eimer, Xiaoqiang Zhang, Gregory Malinowski, et al. "Ultrafast single-pulse switching of Tb-dominant CoTb alloy." Applied Physics Letters 122, no. 2 (January 9, 2023): 022401. http://dx.doi.org/10.1063/5.0131716.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Single-pulse magnetization switching by femtosecond laser pulses is the fastest way to manipulate magnetization. To date, among rare-earth transition metal alloys, single-pulse switching is limited to Gd-based structures. Here, we demonstrate ultrafast single-pulse switching of Tb-dominant CoTb alloys within several tens of picoseconds. Our further analysis shows that the ultrafast magnetization reversal is linked to ultrafast heating of laser pulses and an external field.

38

Zhang, Lei, Xiao Wen Cao, Shun Guang Li, Ru Yi Xiang, and Hui Chao Sun. "Fabrication of Microstructure on Nickel Template by Femtosecond Laser." Applied Mechanics and Materials 670-671 (October 2014): 512–16. http://dx.doi.org/10.4028/www.scientific.net/amm.670-671.512.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This paper presents an experimental investigation into microfabrication of nickel template by femtosecond laser in air at atmospheric pressure. The laser pulses used for the study are 800 nm in wavelength, 100fs in pulse duration, and the repetition rate used is 1KHz. Micro-hole ablation experiments are carried out in air by focusing the femtosecond laser beam on the nickel target surface at normal incidence with the long-focus objective lens of enlargement factor 50 and NA=0.7. Dependence of the diameter, depth and depth-to-diameter ratio of the fabricated holes on the laser power and number of pulses are revealed experimentally. Microgrooves with good uniformity are fabricated on nickel template with femtosecond laser by optimizing the process parameters.

39

Ho, Ching Yen, Chung Ma, and Yu Hsiang Tsai. "Thermal Process of Drilling for Metal Thin Films Using Femtosecond Laser." Applied Mechanics and Materials 764-765 (May 2015): 102–6. http://dx.doi.org/10.4028/www.scientific.net/amm.764-765.102.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The femtosecond laser drilling for metal thin film is theoretically investigated in this paper. Femtosecond laser patterning of metal thin films is of technological significance because the fabrication of electrodes or metallization lines is a key process commonly required in the manufacturing of modern electronic devices. A femtosecond pulsed laser has a temporally short pulse that does not cause significant heat conduction in the material. This property of femtosecond laser pulse drilling makes sub-micron machining achievable with laser irradiation. Considering vaporization as the mechanism of the material removal, this paper employs two-temperature model to analyze the thermal process for femtosecond laser drilling of metal thin film. The variations of the drilling rate and squared diameter with laser fluence are compared with the available experimental data. This study also analytically validates that the drilling depth per pulse is governed by the optical penetration depth for low laser fluences and the squared crater diameter is linearly in proportion to the logarithm of laser fluence.

40

Golovin, Nikolai N., and Alexander K. Dmitriev. "Pulse selector for obtaining femtosecond radiation with a controlled carrier-envelope phase." Analysis and data processing systems, no. 2 (June 28, 2022): 121–32. http://dx.doi.org/10.17212/2782-2001-2022-2-121-132.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

In non-linear optical processes, such as obtaining attosecond pulses, it is extremely important to control the carrier envelope phase. To do this, various periodic trains of identical femtosecond pulses with a controlled phase can be created. In addition, since there is no frequency comb offset in such sequences, the process of measuring optical frequencies is greatly simplified. The pulse selector has been developed to obtain a sequence of identical femtosecond pulses with a controlled carrier – envelope phase. The selector makes it possible to obtain a “pure” sequence of identical femtosecond pulses at the modulator output (when every 125th pulse is selected from the original sequence with a repetition rate of 250 MHz) in a fairly wide range of control signal phase tuning. This range is 1.3 degrees. The phase tuning of the pulse selector provides the possibility of obtaining one hundred twenty-five such sequences with a phase tuning discreteness of 2π/125. The simplest way to reduce discreteness is to increase the ratio of the pulse repetition rate of a femtosecond laser to the shift of its frequency comb. The phase characteristic of the pulse selector was obtained by registering the time dependence of the synthesized sequence with a selector phase tuning step of 0.1 degrees. We measured the spectra of the sequences at different phases of the pulse selector, as well as the emission spectrum of the master laser at the minimum transmission of the modulator in the absence of modulation. The spectrum with the maximum amplitude corresponded to the case when identical pulses with the highest amplitude were selected from the original sequence. The difference between these spectra made it possible to isolate the spectrum of a pure sequence of identical femtosecond pulses without taking into account the "background" that occurs due to the modulator has a finite attenuation of –20 dB.

41

Rung, Stefan, Niklas Häcker, and Ralf Hellmann. "Thermal imaging of high power ultrashort pulse laser ablation of alumina towards temperature optimized micro machining strategies." IOP Conference Series: Materials Science and Engineering 1135, no. 1 (November 1, 2021): 012027. http://dx.doi.org/10.1088/1757-899x/1135/1/012027.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Abstract The application of pulsed laser systems with pulse durations in the pico- and femtosecond regime for material processing is commonly associated with a cold ablation. Due to the minimized interaction-time between the ultrashort laser pulses and the material, this statement is almost valid as long as no heat accumulation effect appears. With the increasing demand of high productivity processes, the average power of ultrashort pulsed laser systems increases above 100 W, which leads, however, to increased thermal effects during laser processing. This is especially important for laser processing of technical ceramics like alumina. Large temperatures gradients, which locally occur during laser processing using high average power could lead to thermal modifications and cracks in the material. In this study, we present a process-optimization method for high power laser ablation of alumina based on thermal imaging. The use of a 2D IR camera enables the estimation of the temperature distribution during the laser processing. We investigate the influence of laser power up to 80 W, pulse duration between 900 fs and 10 ps and processing duration on the resulting material temperature. Beside the material temperature we evaluate the material removal rate and the resulting surface quality.

42

Zhang, Tianyong, Baoshan Guo, Lan Jiang, Tong Zhu, Yanhong Hua, Ningwei Zhan, and Huan Yao. "Single-Shot Multi-Frame Imaging of Femtosecond Laser-Induced Plasma Propagation." Materials 16, no. 8 (April 21, 2023): 3264. http://dx.doi.org/10.3390/ma16083264.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Single-shot ultrafast multi-frame imaging technology plays a crucial role in the observation of laser-induced plasma. However, there are many challenges in the application of laser processing, such as technology fusion and imaging stability. To provide a stable and reliable observation method, we propose an ultrafast single-shot multi-frame imaging technology based on wavelength polarization multiplexing. Through the frequency doubling and birefringence effects of the BBO and the quartz crystal, the 800 nm femtosecond laser pulse was frequency doubled to 400 nm, and a sequence of probe sub-pulses with dual-wavelength and different polarization was generated. The coaxial propagation and framing imaging of multi-frequency pulses provided stable imaging quality and clarity, as well as high temporal/spatial resolution (200 fs and 228 lp/mm). In the experiments involving femtosecond laser-induced plasma propagation, the probe sub-pulses measured their time intervals by capturing the same results. Specifically, the measured time intervals were 200 fs between the same color pulses and 1 ps between the adjacent different. Finally, based on the obtained system time resolution, we observed and revealed the evolution mechanism of femtosecond laser-induced air plasma filaments, the multifilament propagation of femtosecond laser in fused silica, and the influence mechanism of air ionization on laser-induced shock waves.

43

Spence, Stephanie, Takaaki Harada, Athanasios Margiolakis, Skylar Deckoff-Jones, Aaron N. Shugar, James F. Hamm, Keshav M. Dani, and Anya R. Dani. "Applicability of Femtosecond Lasers in the Cross-section Sampling of Works of Art." MRS Advances 2, no. 33-34 (2017): 1801–4. http://dx.doi.org/10.1557/adv.2017.242.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

ABSTRACTIssues in traditional cross-section sampling of paintings and other cultural artifacts with a scalpel, such as crumbling, delamination and paint compression, can deter conservators from sampling fragile paint layers. Often, such sampling carries the risk of causing further damage from a scalpel, which outweighs the benefits of scientific investigation. Here, we show that femtosecond lasers offer a viable alternative to obtaining cross-sections with minimal damage to the surrounding artwork. A Regenerative Ti:Sapphire amplifier system with a pulse duration of 70 femtoseconds, a few milliwatts of average power and a repetition rate of 1 kHz (1000 pulses/sec) was used for the study. Tests were performed on oil paintings ranging in age from the 19th century to late 20th century. Effective settings were determined to be 2 mW of power at a speed of 10mm/sec using an 800nm laser. Preliminary results suggest femtosecond lasers could be a viable alternative for obtaining paint cross-sections when traditional sampling methods cause unnecessary damage to fragile materials.

44

Meng, Yu, An Gong, Zhicheng Chen, Qingsong Wang, Jianwu Guo, Zihao Li, and Jiafang Li. "Atomistic-Continuum Study of an Ultrafast Melting Process Controlled by a Femtosecond Laser-Pulse Train." Materials 17, no. 1 (December 29, 2023): 185. http://dx.doi.org/10.3390/ma17010185.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

In femtosecond laser fabrication, the laser-pulse train shows great promise in improving processing efficiency, quality, and precision. This research investigates the influence of pulse number, pulse interval, and pulse energy ratio on the lateral and longitudinal ultrafast melting process using an experiment and the molecular dynamics coupling two-temperature model (MD-TTM model), which incorporates temperature-dependent thermophysical parameters. The comparison of experimental and simulation results under single and double pulses proves the reliability of the MD-TTM model and indicates that as the pulse number increases, the melting threshold at the edge region of the laser spot decreases, resulting in a larger diameter of the melting region in the 2D lateral melting results. Using the same model, the lateral melting results of five pulses are simulated. Moreover, the longitudinal melting results are also predicted, and an increasing pulse number leads to a greater early-stage melting depth in the melting process. In the case of double femtosecond laser pulses, the pulse interval and pulse energy ratio also affect the early-stage melting depth, with the best enhancement observed with a 2 ps interval and a 3:7 energy ratio. However, pulse number, pulse energy ratio, and pulse interval do not affect the final melting depth with the same total energies. The findings mean that the phenomena of melting region can be flexibly manipulated through the laser-pulse train, which is expected to be applied to improve the structural precision and boundary quality.

45

Alshehria, A. M., El Sayed Yousefa, A. A. Alshahrania, Akram Ibrahima, Nafis Ahmada, and V. R. Bhardwajb. "Differential Nonlinear Absorption of an Elliptically Polarized Femtosecond Vortex Beam in Tellurite Glass-=SUP=-*-=/SUP=-." Журнал технической физики 128, no. 8 (2020): 1178. http://dx.doi.org/10.21883/os.2020.08.49718.293-19.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

We present differential nonlinear absorption of an elliptically polarized femtosecond laser vortex beam carrying an angular momentum of l = -1 in tellurite glass. Transmission measurements were utilized to measure the nonlinear absorption of the glass on a shot-by-shot basis, and to investigate the modification threshold for the beam. Additionally, the effect of pulse energy on the polarization ellipse was investigated. The results revealed a reduction in the ellipticity as the incident pulse energy was increased. Non-rotation of the ellipsoid indicated that there is no change in the third order nonlinear susceptibility (chi(3)) of the telluride glass upon irradiation by the femtosecond beam. The transmission of multiple pulses through the same spot revealed that although an effect was evident for the first ten pulses, the subsequent pulses had no effect. The transmission of a complete cycle of increasing and decreasing pulse energies revealed no hysteresis of the femtosecond laser vortex beam in tellurite glass in contrast to that reported for Gaussian beams in silica glass. Keywords: vortex beam, tellurite glass, nonlinear absorption.

46

Wang, Qingsong, Lan Jiang, Jingya Sun, Changji Pan, Weina Han, Guoyan Wang, Feifei Wang, Kaihu Zhang, Ming Li, and Yongfeng Lu. "Structure-Mediated Excitation of Air Plasma and Silicon Plasma Expansion in Femtosecond Laser Pulses Ablation." Research 2018 (December 9, 2018): 1–11. http://dx.doi.org/10.1155/2018/5709748.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Femtosecond laser-induced surface structures upon multiple pulses irradiation are strongly correlated with the pulse number, which in turn significantly affects successive laser-material interactions. By recording the dynamics of femtosecond laser ablation of silicon using time-resolved shadowgraphy, here we present direct visualization of the excitation of air plasma induced by the reflected laser during the second pulse irradiation. The interaction of the air plasma and silicon plasma is found to enhance the shockwave expansion induced by silicon ablation in the longitudinal direction, showing anisotropic expansion dynamics in different directions. We further demonstrate the vanishing of air plasma as the pulse number increases because of the generation of a rough surface without light focusing ability. In the scenario, the interaction of air plasma and silicon plasma disappears; the expansion of the silicon plasma and shockwave restores its original characteristic that is dominated by the laser-material coupling. The results show that the excitation of air plasma and the laser-material coupling involved in laser-induced plasma and shockwave expansion are structure mediated and dependent on the pulse number, which is of fundamental importance for deep insight into the nature of laser-material interactions during multiple pulses ablation.

47

Wang, Shutong, Junjie Yang, Guoliang Deng, and Shouhuan Zhou. "Femtosecond Laser Direct Writing of Flexible Electronic Devices: A Mini Review." Materials 17, no. 3 (January 24, 2024): 557. http://dx.doi.org/10.3390/ma17030557.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

By virtue of its narrow pulse width and high peak power, the femtosecond pulsed laser can achieve high-precision material modification, material additive or subtractive, and other forms of processing. With additional good material adaptability and process compatibility, femtosecond laser-induced application has achieved significant progress in flexible electronics in recent years. These advancements in the femtosecond laser fabrication of flexible electronic devices are comprehensively summarized here. This review first briefly introduces the physical mechanism and characteristics of the femtosecond laser fabrication of various electronic microdevices. It then focuses on effective methods of improving processing efficiency, resolution, and size. It further highlights the typical progress of applications, including flexible energy storage devices, nanogenerators, flexible sensors, and detectors, etc. Finally, it discusses the development tendency of ultrashort pulse laser processing. This review should facilitate the precision manufacturing of flexible electronics using a femtosecond laser.

48

LAM, Y. C., D. V. TRAN, and H. Y. ZHENG. "A study of substrate temperature distribution during ultrashort laser ablation of bulk copper." Laser and Particle Beams 25, no. 1 (February 28, 2007): 155–59. http://dx.doi.org/10.1017/s0263034607070206.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

With the aid of an infrared thermograph technique, we directly observed the temperature variation across a bulk copper specimen as it was being ablated by multiple femtosecond laser pulses. Combining the experimental results with simulations, we quantified the deposited thermal power into the copper specimen during the femtosecond laser ablation process. A substantial amount of thermal power (more than 50%) was deposited in the copper specimen, implying that thermal effect can be significant in femtosecond laser materials processing in spite of its ultrashort pulse duration.

49

Pajic, Bojan, Brigitte Pajic-Eggspuehler, Christian Rathjen, Mirko Resan, and Zeljka Cvejic. "Why Use Ultrashort Pulses in Ophthalmology and Which Factors Affect Cut Quality." Medicina 57, no. 7 (July 8, 2021): 700. http://dx.doi.org/10.3390/medicina57070700.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The power density of femtosecond lasers and exposure time to the tissue are crucial for a successful procedure in terms of safety and precision. The reduction of the pulse duration allows reducing the quantity of the energy to be delivered to the tissue for disruption with strongly diminished mechanical and thermal collateral damage. The cutting effect of ultra-short pulses is very precise, minimally traumatic, safe, and predictable. Future developments will lead to further energy reductions to achieve optical breakdowns. However, the pulse length cannot be shortened arbitrarily because below 100 fs nonlinear effects can change the process in an unfavorable way. Compared to manual-conventional cataract surgery, femtosecond laser-assisted cataract surgery (FLACS) shows many advantages in clinical application, especially with regard to precision and tissue protection. The femtosecond laser has become particularly important and has made the overall procedure safer when we deal with complex cataract cases such as subluxated lenses. We provide an overview of the evolution of femtosecond laser technology for use in refractive and cataract surgeries. This article describes the advantages of available laser platforms with ultrashort pulses and mainly focuses on the technical and physical backgrounds of ophthalmic surgery technologies.

50

Jiang, Lan, and Hai-Lung Tsai. "Energy Transport and Nanostructuring of Dielectrics by Femtosecond Laser Pulse Trains." Journal of Heat Transfer 128, no. 9 (May 2, 2006): 926–33. http://dx.doi.org/10.1115/1.2241979.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This study analyzes single burst ablation of dielectrics by a femtosecond pulse train that consists of one or multiple pulses. It is found that (1) there exist constant-ablation-depth zones with respect to fluence for one or multiple pulses per train and (2) for the same total fluence per train, although the ablation depth decreases in multiple pulses as compared to that of a single pulse, the depth of the constant-ablation-depth zone decreases. In other words, repeatable structures at the desired smaller nanoscales can be achieved in dielectrics by using the femtosecond pulse train technology, even when the laser fluence is subject to fluctuations. The predicted trends are in agreement with published experimental data.

Journal articles on the topic 'Pulses laser femtoseconde'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles