Showing papers on "Pulse duration published in 2003"
TL;DR: It is shown that the synchronization could be improved considerably by controlling the underlying ultrafast electron dynamics, to provide pulses of 130 attoseconds in duration, which would allow us to track fast electron processes in matter.
Abstract: Subfemtosecond light pulses can be obtained by superposing several high harmonics of an intense laser pulse. Provided that the harmonics are emitted simultaneously, increasing their number should result in shorter pulses. However, we found that the high harmonics were not synchronized on an attosecond time scale, thus setting a lower limit to the achievable x-ray pulse duration. We showed that the synchronization could be improved considerably by controlling the underlying ultrafast electron dynamics, to provide pulses of 130 attoseconds in duration. We discuss the possibility of achieving even shorter pulses, which would allow us to track fast electron processes in matter.
694 citations
TL;DR: In this paper, it was demonstrated that the direction of electron emission from photoionized atoms can be controlled by varying the phase of the field, providing for the first time a tool for its accurate determination.
Abstract: For the shortest pulses generated to date, the amplitude of the electromagnetic wave changes almost as rapidly as the field oscillates. The temporal variation of the field, which directly governs strong-field interactions, therefore depends on whether the maximum of the pulse amplitude coincides with that of the wave cycle or not, i.e., on the phase of the field with respect to the pulse envelope. It is demonstrated that the direction of electron emission from photoionized atoms can be controlled by varying the phase of the field, providing for the first time a tool for its accurate determination. Directing fast electron emission to the right or to the left with the light phase constitutes a new kind of coherent control.
412 citations
Journal Article•
TL;DR: Femtosecond as well as picosecond pulses provide approximately the same relative optical window for safe two-photon fluorescence microscopy, indicating that cell destruction is likely based on a two- photon excitation process rather than a one- or a three-ph photon event.
Abstract: The influence of the pulse length, ?, of ultrashort laser pulses at 780 and 920??nm on cell vitality and cellular reproduction has been studied. A total of 2400 nonlabeled cells were exposed to a highly focused scanning beam from a mode-locked 80-MHz Ti:sapphire laser with 60??s pixel dwell time. For the same pulse energy, destructive effects were more pronounced for shorter pulses. The damage behavior was found to follow approximately a P2/? dependence (P, mean power), indicating that cell destruction is likely based on a two-photon excitation process rather than a one- or a three-photon event. Therefore, femtosecond as well as picosecond pulses provide approximately the same relative optical window for safe two-photon fluorescence microscopy.
264 citations
TL;DR: In this article, the effect of electron recirculation on the rear side sheath acceleration is discussed and it is found that the peak proton energy increases in inverse proportion to the target thickness.
Abstract: The generation of high energy protons from the interaction of a short laser pulse with a dense plasma, accompanied by a preformed low density plasma, has been studied by particle-in-cell simulations. The proton acceleration toward the laser direction in the preformed plasma is characterized by a time-dependent model and the peak proton energy is given. The effect of electron recirculation on the rear side sheath acceleration is discussed and it is found that the peak proton energy increases in inverse proportion to the target thickness. These results shed light on the peak proton energy dependence on laser intensity, laser pulse length, and target thickness. Finally the optimal parameters of the laser pulse for large ion peak energy and conversion efficiency are discussed.
258 citations
TL;DR: To the knowledge this result represents the highest peak power pulses yet produced in any Ti:sapphire chirped-pulse amplification system.
Abstract: We have successfully produced a laser pulse with a peak power of 0.85 PW for a pulse duration of 33 fs in a four-stage Ti:sapphire amplifier chain based on chirped-pulse amplification. To our knowledge this result represents the highest peak power pulses yet produced in any Ti:sapphire chirped-pulse amplification system.
253 citations
TL;DR: Broadband, constant phase excitation which tolerates miscalibration of RF power and variations in RF homogeneity relevant for standard high-resolution probes is chosen to illustrate the capabilities of the optimal control formalism.
249 citations
Patent•
23 Jul 2003
TL;DR: In this paper, a method for precise working of material, particularly organic tissue, comprises the step of providing laser pulses with a pulse length between 50 fs and 1 ps and with pulse frequency from 50 kHz to 1 MHz and with a wavelength between 600 and 2000 nm.
Abstract: A method for precise working of material, particularly organic tissue, comprises the step of providing laser pulses with a pulse length between 50 fs and 1 ps and with a pulse frequency from 50 kHz to 1 MHz and with a wavelength between 600 and 2000 nm for acting on the material to be worked. Apparatus, in accordance with the invention, for precise working of material, particularly organic tissue comprising a pulsed laser, wherein the laser has a pulse length between 50 fs and 1 ps and with a pulse frequency of from 50 kHz to 1 MHz is also described.
179 citations
TL;DR: In this paper, the authors analyzed the time profiles of individual gamma-ray burst (GRB) pulses that are longer than 2 s by modeling them with analytical functions that are based on physical first principles and well-established empirical descriptions of GRB spectral evolution.
Abstract: We analyze the time profiles of individual gamma-ray burst (GRB) pulses that are longer than 2 s by modeling them with analytical functions that are based on physical first principles and well-established empirical descriptions of GRB spectral evolution. These analytical profiles are independent of the emission mechanism and can be used to model both the rise and decay profiles, allowing for the study of the entire pulse light curve. Using this method, we have studied a sample of 77 individual GRB pulses, allowing us to examine the fluence, pulse width, asymmetry, and rise and decay power-law distributions. We find that the rise phase is best modeled with a power law of average index r = 1.48 ± 0.07 and that the average decay phase has an index of d = 2.44 ± 0.12. We also find that the ratio between the rise and decay times (the pulse asymmetry) exhibited by the GRB pulse shape has an average value of 0.47, which varies little from pulse to pulse and is independent of pulse duration or intensity. Although this asymmetry is largely uncorrelated to other pulse properties, a statistically significant trend is observed between the pulse asymmetry and the decay power-law index, possibly hinting at the underlying physics. We compare these parameters with those predicted to occur if individual pulse shapes are created purely by relativistic curvature effects in the context of the fireball model, a process that makes specific predictions about the shape of GRB pulses. The decay index distribution obtained from our sample shows that the average GRB pulse fades faster than the value predicted by curvature effects, with only 39% of our sample being consistent with the curvature model. We discuss several refinements of the relativistic curvature scenario that could naturally account for these observed deviations, such as symmetry breaking and varying relative timescales within individual pulses.
160 citations
TL;DR: Gas-based ultrasound (US) contrast agents increase erythrocyte sonolysis, presumably via enhancing inertial cavitation (IC) activity, and the amount of IC activity and hemolysis generated by exposure to 1.15 MHz US were examined.
Abstract: Gas-based ultrasound (US) contrast agents increase erythrocyte sonolysis, presumably via enhancing inertial cavitation (IC) activity. The amount of IC activity (IC "dose") and hemolysis generated by exposure to 1.15 MHz US were examined with different US pulse lengths, but with the same delivered acoustic energy, for Optison and Albunex. The hypotheses were that 1. at longer pulse lengths, IC would generate more bubbles that could nucleate additional IC activity; 2. if the interval between pulse pairs were short enough for the next pulse to hit derivative bubbles before their dissolution, more IC could be induced; and 3. hemolysis would be proportional to IC activity. Two types of studies were performed. In the first, bubble generation after each burst of IC activity was quantified using an active cavitation detector (ACD), for different pulse lengths (5, 10, 20, 30, 50, 100 or 200 cycles), but the same pressure level (3 MPa) and total "on" time (173.16 ms). Low concentrations of either Optison or Albunex were added into the tank with high-intensity and interrogating transducers orthogonal to each other. For pulse lengths > 100 cycles, and pulse repetition intervals < 5 ms, a "cascade" effect (explosive bubble generation) was observed. In the second, IC was measured by passive detection methods. IC dose and hemolysis were determined in whole blood samples at a pressure level (3 MPa) and interpulse interval (5 ms) that induced the "cascade" effect. Each blood sample was mixed with the same number of contrast microbubbles (Optison approximately 0.3 v/v % and Albunex approximately 0.5 v/v %), but exposed to different pulse lengths (5, 10, 20, 30, 50, 100 or 200 cycles). With Optison, up to 60% hemolysis was produced with long pulses (100 and 200 cycles), compared with < 10% with short pulses (5 and 10 cycles). Albunex generated considerably less IC activity and hemolysis. The r(2) value was 0.99 for the correlation between hemolysis and IC dose. High pulse-repetition frequency (PRF) (500 Hz) generated more hemolysis than the low PRF (200 Hz) at 3 MPa. All experimental results could be explained by the dissolution times of IC-generated bubbles.
143 citations
TL;DR: The model describes well the transmembrane transport caused by electropermeabilization, allowing to study the uptake of molecules as a function of elapsed time, voltage and pulse duration, and shows that the shapes of the curves of cell permeabilization and survival as functions of pulse amplitude can to a large extent be explained by cell size distribution.
132 citations
TL;DR: In this article, the application of ultrashort voltage pulses to a tiny tool electrode under suitable electrochemical conditions enables precise three-dimensional machining of stainless steel in order to reach submicrometer precision and high processing speed.
Abstract: Application of ultrashort voltage pulses to a tiny tool electrode under suitable electrochemical conditions enables precise three-dimensional machining of stainless steel In order to reach submicrometer precision and high processing speed, the formation of a passive layer on the workpiece surface during the machining process has to be prevented by proper choice of the electrolyte Mixtures of concentrated hydrofluoric and hydrochloric acid are well suited in this respect and allow the automated machining of complicated three-dimensional microelements The dependence of the machining precision on pulse duration and pulse amplitude was investigated in detail
TL;DR: Pulsed laser ablation of Au target in n-alkanes generates Au sols Experiments have been performed using the second harmonic of a Nd:yttritium-aluminum-garnet at 532 nm wavelength with a 5 ns pulse duration at a repetition rate of 10 Hz and fluences ranging from 1 to 200 J/cm2 as mentioned in this paper.
Abstract: Pulsed laser ablation of Au target in n-alkanes generates Au sols Experiments have been performed using the second harmonic of a Nd:yttritium–aluminum–garnet at 532 nm wavelength with a 5 ns pulse duration at a repetition rate of 10 Hz and fluences ranging from 1 to 200 J/cm2 Data coming from optical extinction show that the length of the hydrocarbon chain is able to tune the shape of the produced particles and the rate of formation in a controlled way The data are supported by atomic force microscopy and transmission electron microscope observations
TL;DR: This work theoretically investigate photoelectron emission induced by an intense, few-cycle laser pulse from a metal surface (jellium) within the framework of time-dependent density functional theory and finds a pronounced varphi dependence of the photocurrent.
Abstract: The phase varphi of the field oscillations with respect to the peak of a laser pulse influences the light field evolution as the pulse length becomes comparable to the wave cycle and, hence, affects the interaction of intense few-cycle pulses with matter. We theoretically investigate photoelectron emission induced by an intense, few-cycle laser pulse from a metal surface (jellium) within the framework of time-dependent density functional theory and find a pronounced varphi dependence of the photocurrent. Our results reveal a promising route to measuring varphi of few-cycle light pulses (tau<6 fs at lambda=0.8 microm) at moderate intensity levels (I(p) approximately 10(12) W/cm(2)) using a solid-state device.
TL;DR: In this paper, the authors used an 800-nm fundamental pulse whose polarization evolves with time to generate high-order harmonics by controlling the ellipticity modulation of the fundamental field, which can continuously confine the harmonic emission from an estimated minimum value of 7 fs $(1\mathrm{fs}^{\ensuremath{-}15}s})$ up to more than the 35 fs input pulse duration.
Abstract: We generate high-order harmonics by using an 800-nm fundamental pulse whose polarization evolves with time. Controlling the ellipticity modulation of the fundamental field allows us to continuously confine the harmonic emission from an estimated minimum value of 7 fs $(1\mathrm{fs}{=10}^{\ensuremath{-}15}\mathrm{s})$ up to more than the 35 fs input pulse duration. Depending on the observed harmonic, the harmonic spectrum can show either a narrowing or a broadening when the ellipticity is changed in good agreement with an effective confinement of the high-order harmonic generation.
Patent•
22 Apr 2003
TL;DR: In this article, a system and method for classifying signals occurring in a frequency band is proposed, where the accumulated signal data is compared against reference data associated with known signals to classify the one or more signals in the frequency band based on the comparison.
Abstract: A system and method for classifying signals occurring in a frequency band One or more characteristics of one or more signals in the frequency band are detected using any suitable technology, such as a device that can generate characteristics of signal pulses detected in the frequency band Data pertaining to the signal pulses is accumulated over time The accumulated signal data is compared against reference data associated with known signals to classify the one or more signals in the frequency band based on the comparison The accumulated data may include one or more characteristics selected from the group consisting of: pulse center frequency, pulse bandwidth, pulse duration, time between pulses and number of different active pulses, and wherein the reference data associated with each of a plurality of known signals comprises one or more characteristics selected from the group consisting of: pulse center frequency, pulse bandwidth, pulse duration and time between pulses The accumulated signal data is compared against the reference data, and depending on the degree of match with reference data, a signal can be classified Additional levels of signal classification processing may be performed
27 Aug 2003
TL;DR: In this article, the authors studied the ablation of metal targets in air with femtosecond laser pulses, and showed that the intensity of the laser pulses depends logarithmically on the optical penetration depth.
Abstract: In the current work ablation of metal targets in air with femtosecond laser pulses is studied. The laser pulses used for the study were 775 nm in wavelength, 150 fs in pulse duration and the repetition rate was 100 Hz. Ablation thresholds have been measured for a number of metals including stainless steel niobium, titanium and copper. The ablation depth per pulse was measured for laser pulse fluences ranging from the ablation threshold (of most metals) ~ 0.1 J/cm 2 up to 10 J/cm 2 . It has been shown previously that there are two different ablation regimes. In both cases the ablation depth per pulse depends logarithmically on the laser fluence. While operating in the first ablation regime the ablation rate is low and is dependant on the optical penetration depth, α -1 . While in the second ablation regime the ablation rate is greater and is characterized by the 'electron heat diffusion length' or the 'effective heat penetration depth'. In the present study good qualitative agreement in the ablation curve trends was observed with the data of other authors, e.g. Nolte et al (1997).
TL;DR: A diode-pumped chirped-pulse regenerative amplifier with a cooled Yb:YLF crystal with high effective extraction efficiency is developed, attributed to reduced saturation fluence at low temperature and to a high effective pulse energy fluence during regenerative amplification.
Abstract: A diode-pumped chirped-pulse regenerative amplifier with a cooled Yb:YLF crystal has been developed. The output pulse energy is 30 mJ at 20-Hz repetition rate. A high effective extraction efficiency of 68% is obtained, which is attributed to reduced saturation fluence at low temperature and to a high effective pulse energy fluence during regenerative amplification. After pulse compression by use of a parallel grating pair, 18-mJ pulse energy and 795-fs pulse duration are obtained.
TL;DR: The specular reflectivity of plasma mirrors formed by sub-picosecond pulses from a titanium:sapphire laser has been measured for different angles of incidence and for two different pulse lengths as a function of the laser intensity as discussed by the authors.
Abstract: The specular reflectivity of plasma mirrors formed by subpicosecond pulses from a titanium:sapphire laser has been measured for different angles of incidence and for two different pulse lengths as a function of the laser intensity Laser pulses with energies up to 250 mJ and pulse durations of 90 and 500 fs were focused onto a fused silica substrate For angles of incidence between 6° and 45° the specular reflectivity increases to values of about 80% for intensities above a certain threshold intensity The threshold intensity varies with the pulse length but is nearly independent of the angle of incidence For very high intensities the specular reflectivity drops again to values of only a few percent
TL;DR: By optimizing the cavity dispersion map, 1.5-nJ pulses as short as 36 fs were obtained from a Yb-doped fiber laser as mentioned in this paper, where residual higher-order dispersion currently limits the pulse duration.
Abstract: By optimizing the cavity dispersion map, 1.5-nJ pulses as short as 36 fs are obtained from a Yb-doped fiber laser. Residual higher-order dispersion currently limits the pulse duration, and it should be possible to generate pulses as short as 25–30 fs with Yb-doped fiber.
Journal Article•
TL;DR: In this paper, the dependence of LIE irradiance thresholds on pulse duration, optical wavelength, and focal volume was examined, and the experimental data obtained is compared with a theoretical model.
Abstract: Laser-induced breakdown (LIE) thresholds are determined for pulse durations of 2.4 ps, 400 fs, and 100 fs at 580 mn in high purity water, saline and tap water. The dependence of LIE irradiance thresholds on pulse duration, optical wavelength, and focal volume is examined, and the experimental data obtained is compared with a theoretical model. The slopes of the probability curves calculated are compared with mechanisms for LIE, namely avalanche ionization, multiphoton initiated avalanche ionization, and multiphoton ionization. Lastly, the dependence of the peak breakdown electric field on pulse duration and focal volume is empirically determined and compared with previous work.
TL;DR: In this article, the authors studied the ablation rates of aluminum and stainless steel as a function of fluence, hole depth, pulse duration and ambient pressure (air vs vacuum) and found a weak rate dependence on pulse duration from 150 fs to 500 ps.
Abstract: Ablation rates of aluminum and stainless steel are studied as a function of fluence, hole depth, pulse duration and ambient pressure (air vs vacuum). We find a weak rate dependence on pulse duration from 150 fs to 500 ps, and a strong rate dependence on hole depth due to surface roughness. Machining in air plays an important role in deep holes, but has a weaker influence on initial surface ablation rates. Oxidation greatly reduces drilling rates for deep holes in aluminum.
Patent•
28 Jul 2003
TL;DR: In this paper, a system and method for classifying signals occurring in a frequency band is proposed, in which data pertaining to the signal pulses is accumulated over time and compared against reference data associated with known signals to classify the one or more signals in the frequency band based on the comparison.
Abstract: A system and method for classifying signals occurring in a frequency band. One or more characteristics of one or more signals in the frequency band are detected using any suitable technology, such as a device that can generate characteristics of signal pulses detected in the frequency band. Data pertaining to the signal pulses is accumulated over time. The accumulated signal data is compared against reference data associated with known signals to classify the one or more signals in the frequency band based on the comparison. The accumulated data may include one or more characteristics selected from the group consisting of: pulse center frequency, pulse bandwidth, pulse duration, time between pulses and number of different active pulses, and wherein the reference data associated with each of a plurality of known signals comprises one or more characteristics selected from the group consisting of: pulse center frequency, pulse bandwidth, pulse duration and time between pulses. The accumulated signal data is compared against the reference data, and depending on the degree of match with reference data, a signal can be classified. Additional levels of signal classification processing may be performed.
Patent•
10 Jul 2003
TL;DR: In this article, a method and surgical technique for corneal reshaping and for presbyopia correction are provided, which consists of a scanner, a beam spot controller and coupling fibers and the basic laser having a wavelength of (190-310) nm, (0.5-3.2) microns and a pulse duration of about (10-150) nanoseconds, ( 10-500) microseconds and true continuous wave.
Abstract: A method and surgical technique for corneal reshaping and for presbyopia correction are provided. The preferred embodiments of the system consists of a scanner, a beam spot controller and coupling fibers and the basic laser having a wavelength of (190-310) nm, (0.5-3.2) microns and (5.6-6.2) microns and a pulse duration of about (10-150) nanoseconds, (10-500) microseconds and true continuous wave. New mid-infrared gas lasers are provided for the corneal reshaping procedures. Presbyopia is treated by a method which uses ablative laser to ablate the sclera tissue and increase the accommodation of the ciliary body. The tissue bleeding is prevented by a dual-beam system having ablative and coagulation lasers. The preferred embodiments include short pulse ablative lasers (pulse duration less than 200 microseconds) with wavelength range of (0.15-3.2) microns and the long pulse (longer than 200 microseconds) coagulative lasers at (0.5-10.6) microns. Compact diode lasers of (980-2100) nm and diode-pumped solid state laser at about 2.9 microns for radial ablation patterns on the sclera ciliary body of a cornea are also disclosed for presbyopia correction using the mechanism of sclera expansion.
TL;DR: In this article, high-aspect-ratio nanometer accurate features were machined in nickel using ultrashort voltage pulse electrochemical machining without the need for rastering.
Abstract: We show that complex patterns including three-dimensional structures, lines, curved features, and arrays can be machined in substrates in single-step processing without the need for rastering. High-aspect-ratio nanometer accurate features were machined in nickel using ultrashort voltage pulse electrochemical machining. Experiments were conducted with two different tool shapes. The first was a combination of rectangles, squares, and a half circle; the second was a 2×2 array. The effect of pulse duration and electrolyte concentration on feature resolution was studied. Structures with 90 nm widths were made by applying 2 ns voltage pulses.
TL;DR: A compact and highly efficient diode-end-pumped TEM00 Nd:YVO4 slab laser with an output power of 103 W and beam quality M2 < or = 1.5 is reported on.
Abstract: We report on a compact and highly efficient diode-end-pumped TEM00Nd:YVO4 slab laser with an output power of 103 W and beam quality M2≦1.5. The optical-to-optical efficiency was 41.5%. In electro-optically Q-switched operation, 83 W of average power at a pulse-repetition rate of 50 kHz with a pulse length of 11.3 ns was obtained. At a pulse-repetition rate of 10 kHz, 5.6 mJ of pulse energy, and 870 kW of peak power were measured.
TL;DR: A comprehensive optimization of efficiency for magnetic stimulation has been conducted and shows that there exists an optimal inductance, as a consequence of an optimal pulse duration, corresponding to a minimum threshold energy.
Abstract: Magnetic stimulation can activate excitable tissues noninvasively. However, this method requires high energy to operate and can produce equipment heat that leads to inefficient stimulation. In this study, a comprehensive optimization of efficiency for magnetic stimulation has been conducted. A total of 16,781 coil designs were tested in order to determine the optimal coil geometry and inductance for neural excitation. Induced electric fields were calculated to find the optimal stimulation site (OSS) of a given coil. The threshold energy of a magnetic pulse for neural excitation was then calculated based on the transmembrane responses of a nerve model. Simulation results show that there exists an optimal inductance, as a consequence of an optimal pulse duration, corresponding to a minimum threshold energy. A longer pulse width is required to obtain the maximum efficiency for axons with slower membrane dynamics, a longer coil-to-fiber distance, and greater values of resistance (R) and capacitance (C) of the resistance-inductance-capacitance circuit. The optimal geometry features a minimum coil height, suggesting a flat coil design for optimal efficiency. The dimension of the optimal coil design increases with the coil-to-fiber distance. Moreover, the cloverleaf design achieves the highest efficiency for infinitely long fibers whereas the butterfly design is optimal for terminating or bending fibers.
Patent•
31 Jul 2003
TL;DR: In this paper, a long pulse alexandrite laser for treating dermatological specimens is disclosed, which allows operation in the near-infrared, specifically in a 50 nm range surrounding 755.
Abstract: A long pulse alexandrite laser for treating dermatological specimens is disclosed. The use of alexandrite allows operation in the near-infrared, specifically in a 50 nm range surrounding 755. Infrared in this range allows good penetration while still achieving an acceptable ratio of hemoglobin to melanin absorption In addition, a method and related system for treating biologic tissue with pulse light includes generating a long effective output light pulse comprising a series of sub-pulses having a fractional duty cycle over a selected effective pulse duration, a periodicity that is less than the thermal relaxation time of a targeted structure, and an interpulse-delay between successive sub-pulses that is greater than the thermal relaxation time of non-targeted structures within the treatment area; and delivering the output light to the tissue of a patient.
TL;DR: In this article, a diode-pumped highly efficient Cr4+:YAG passively Q-switched Nd:GdVO4 laser formed by a plano-concave resonator has been demonstrated.
Abstract: A diode-pumped highly efficient Cr4+:YAG passively Q-switched Nd:GdVO4 laser formed by a plano–concave resonator has been demonstrated. At the highest attainable absorbed pump power of 11.4 W, 4.05 W of average output power, which was two thirds of the maximum corresponding cw output, was achieved with an optical conversion efficiency of 35.5%, and the slope efficiency was determined to be 46.8%, reaching 85% of the magnitude of its cw counterpart. The resulting shortest pulse duration, single-pulse energy, and peak power were found to be 13 ns, 90 μJ, and 7 kW, respectively, with a pulse repetition frequency (PRF) of 45 kHz. Two particularly modified resonator configurations were employed; the largest pulse energy and the highest peak power reached were, respectively, 154 μJ and 11.2 kW at 8.5 W of absorbed pump power. An analytical relation between the PRF and the absorbed pump power is given for a passively Q-switched laser, showing good consistency with experiment with a Nd:GdVO4 laser. The dependence of the operational parameters on the pump power and on the output coupling was also investigated experimentally. Issues involving the criterion for passive Q switching are discussed in some detail for Cr4+:YAG passively Q-switched neodymium-doped vanadate lasers.
TL;DR: In this article, the authors describe several approaches to basic femtosecond machining and materials processing that should lead to practical applications, including high-throughput deep hole drilling in glasses in ambient air, and precision high-speed micron-scale surface modification of composite materials and chalcogenide glasses.
Abstract: We describe several approaches to basic femtosecond machining and materials processing that should lead to practical applications. Included are results on high-throughput deep hole drilling in glasses in ambient air, and precision high-speed micron-scale surface modification of composite materials and chalcogenide glasses. Ablation of soda-lime silicate glass and PbO lead-silicate is studied under three different sets of exposure conditions, for which both the wavelength and pulse duration are varied. Ablation rates are measured below and above the air ionization threshold. The differences observed are explained in terms of self-channeling in the ablated hole. Fabrication of practical devices such as waveguides and gratings is demonstrated in chalcogenide glass.
TL;DR: In this article, a three-dimensional (3D) optical memory recording and reading in glass by femtosecond pulses was described, and the readout was carried out by the white-light continuum generated from the previously damaged sites (recorded memory bits).
Abstract: We report on three-dimensional (3D) optical memory recording and reading in glass by femtosecond pulses. Optically induced dielectric breakdown of glass is a mechanism of recording. The formulae of dielectric breakdown presented are applicable, in principle, for any crystalline or amorphous dielectric material. Scaling dependences of the probabilities of multi-photon and impact ionization are given. The measured threshold of an in-bulk dielectric breakdown of silica was reproduced numerically by implementing the ionization potential of Si (8.15 eV) for calculations. Exact measures of focal spot size and pulse duration at the focus allowed us to evaluate the intensity of a pulse during recording of 3D optical memory bits with high accuracy. The readout of the 3D optical memory was carried out by the white-light continuum generated from the previously damaged sites (recorded memory bits). The mechanism of the readout was a four-photon parametric interaction.