Showing papers on "Filamentation published in 2010"
Book•
22 Oct 2010
TL;DR: In this article, the theory of single-and multiple-filamentation physics is discussed, as well as the four-wave-mixing inside a single-focal beam.
Abstract: Filamentation Physics.- Theory of Single Filamentation.- Multiple Filamentation.- Filamentation Nonlinear Optics: General.- Filamentation Nonlinear Optics: Third Harmonic Generation and Four-Wave-Mixing Inside a Filament.- Remote Sensing Using Filamentation.- Challenges Ahead.
253 citations
TL;DR: Higher-order nonlinear indices provide the main defocusing contribution to self-channeling of ultrashort laser pulses in air and argon at 800 nm, in contrast with the previously accepted mechanism of filamentation where plasma was considered as the dominant defocusing process.
Abstract: We show that higher-order nonlinear indices (${n}_{4}$, ${n}_{6}$, ${n}_{8}$, ${n}_{10}$) provide the main defocusing contribution to self-channeling of ultrashort laser pulses in air and argon at 800 nm, in contrast with the previously accepted mechanism of filamentation where plasma was considered as the dominant defocusing process. Their consideration allows us to reproduce experimentally observed intensities and plasma densities in self-guided filaments.
233 citations
TL;DR: The results identify a source and focusing parameter working window where high aspect ratio taper-free microchannels can be reproducibly produced without sample translation.
Abstract: We present a systematic study of femtosecond laser microchannel machining in glass using nondiffracting Bessel beams. In particular, our results identify a source and focusing parameter working window where high aspect ratio taper-free microchannels can be reproducibly produced without sample translation. With appropriate source parameters, we machine channels of 2 microm diameter and with aspect ratios up to 40. We propose the filamentation stability of the Bessel beam propagation as the critical factor underlying the controlled and reproducible results that have been obtained.
176 citations
TL;DR: An overview of recent progress concerning remote sensing of the atmosphere using femtosecond laser filamentation is presented and white-light supercontinuum emission in the infrared to UV range is generated, which can be used as an ideal light source for absorption Lidar.
Abstract: Powerful femtosecond laser pulses propagating in transparent materials result in the formation of self-guided structures called filaments. Such filamentation in air can be controlled to occur at a distance as far as a few kilometers, making it ideally suited for remote sensing of pollutants in the atmosphere. On the one hand, the high intensity inside the filaments can induce the fragmentation of all matters in the path of filaments, resulting in the emission of characteristic fluorescence spectra (fingerprints) from the excited fragments, which can be used for the identification of various substances including chemical and biological species. On the other hand, along with the femtosecond laser filamentation, white-light supercontinuum emission in the infrared to UV range is generated, which can be used as an ideal light source for absorption Lidar. In this paper, we present an overview of recent progress concerning remote sensing of the atmosphere using femtosecond laser filamentation.
141 citations
TL;DR: The compact optical configuration utilizing a delay plate in a collinear geometry serves to simplify alignment and increase stability, making it a practical source for transient IR spectroscopy.
Abstract: A compact and stable method for generating high-intensity linearly polarized continuum mid-IR and terahertz light using ultrafast femtosecond (fs) laser pulses is demonstrated. Continuous light generation from 3300 cm(-1) (100 THz, 3 microm) in a sub-100 fs laser pulse is facilitated by nonlinear mixing of the fundamental, second harmonic, and third harmonic of an ultrafast amplified laser source through filamentation in air. Including the third harmonic in the mixing scheme leads to a tenfold increase in the generated IR power. The compact optical configuration utilizing a delay plate in a collinear geometry serves to simplify alignment and increase stability, making it a practical source for transient IR spectroscopy.
108 citations
TL;DR: The capacities of the tec1/tec1 mutant and the flo8/flo8 TDH3-TEC1 strains to form filaments with impaired virulence suggest that filamentation alone is not sufficient to kill G. mellonella and suggest other virulence factors may be associated with genes that regulate filamentation.
100 citations
TL;DR: This work presents a detailed report of the entire unstable k spectrum of a relativistic collisionless beam-plasma system within a fully kinetic framework and investigates the hierarchy between the competing modes, paying particular attention to the relatively poorly known quasielectrostatic oblique modes.
Abstract: Following a recent Letter by Bret [Phys. Rev. Lett. 100, 205008 (2008)], we present a detailed report of the entire unstable k spectrum of a relativistic collisionless beam-plasma system within a fully kinetic framework. In contrast to a number of previously published studies, our linear analysis makes use of smooth momentum distribution functions of the Maxwell-Juttner form. The three competing classes of instabilities, namely, two-stream, filamentation, and oblique modes, are dealt with in a unified manner, no approximation being made regarding the beam-plasma densities, temperatures, and drift energies. We investigate the hierarchy between the competing modes, paying particular attention to the relatively poorly known quasielectrostatic oblique modes in the regime where they govern the system. The properties of the fastest growing oblique modes are examined in terms of the system parameters and compared to those of the dominant two-stream and filamentation modes.
75 citations
TL;DR: It is found that intensity clamping during filamentation effect still play a role even under strong external focusing, and the electron density in some interaction zones is higher than 3 × 10(19) cm(-3), which indicates that each air molecule there is ionized.
Abstract: The propagation of tightly focused femtosecond laser pulse with numerical aperture of 012 in air is investigated experimentally The formation and evolution of the filament bunch are recorded by time-resolved shadowgraph with laser energy from 24 mJ to 47 mJ The distribution of electron density in breakdown area is retrieved using Nomarski interferometer It is found that intensity clamping during filamentation effect still play a role even under strong external focusing The electron density in some interaction zones is higher than 3×1019 cm-3, which indicates that each air molecule there is ionized
64 citations
TL;DR: In this article, the authors have experimentally measured that laser filaments in air generate up to 1014, 3×1012, and 3 ×1013 molecules of O3, NO, and NO2, respectively.
Abstract: We have experimentally measured that laser filaments in air generate up to 1014, 3×1012, and 3×1013 molecules of O3, NO, and NO2, respectively. The corresponding local concentrations in the filament active volume are 1016, 3×1014, and 3×1015 cm−3, and allows efficient oxidative chemistry of nitrogen, resulting in concentrations of HNO3 in the parts per million range. The latter forming binary clusters with water, our results provide a plausible pathway for the efficient nucleation recently observed in laser filaments.
62 citations
TL;DR: Measurements of the supercontinuum emission from ultrashort Ti:Saph laser pulse filamentation in air in a tightly focused geometry indicate that peak intensities exceed the clamping value of a few 10(13) W/cm(2) obtained for filamentations in a loose focusing geometry by at least one order of magnitude.
Abstract: We present measurements of the supercontinuum emission (SCE) from ultrashort Ti:Saph laser pulse filamentation in air in a tightly focused geometry. The spectral broadening of SCE indicates that peak intensities exceed the clamping value of a few 10(13) W/cm(2) obtained for filamentation in a loose focusing geometry by at least one order of magnitude. We provide an interpretation for this regime of filamenation without intensity clamping.
60 citations
TL;DR: It is demonstrated that the continuum generation process is initiated by the filamentation of the vortex, resulting in a spatially divergent continuum.
Abstract: We employ an optical vortex beam for the generation of femtosecond supercontinuum in a solid state medium. We demonstrate that the continuum generation process is initiated by the filamentation of the vortex, resulting in a spatially divergent continuum. Despite the strong self-focusing and the formation of multiple hot-spots along the vortex ring, the singularity is preserved in both the near- and far-fields.
Abstract: We study, both experimentally and theoretically, the underlying physics of third-harmonic generation in air by a filamented infrared femtosecond laser pulse propagating through a thin plasma channel. It is shown that the recently observed more than two-order-of-magnitude increase of the efficiency of third-harmonic generation occurs due to the plasma-enhanced third-order susceptibility. An estimate of the effective value of this susceptibility is given.
Journal Article•
TL;DR: In this article, the authors present a detailed report of the entire unstable k spectrum of a relativistic collisionless beam-plasma system within a fully kinetic framework, making use of smooth momentum distribution functions of the Maxwell-Juttner form.
Abstract: Following a recent Letter by Bret [Phys. Rev. Lett. 100, 205008 (2008)], we present a detailed report of the entire unstable k spectrum of a relativistic collisionless beam-plasma system within a fully kinetic framework. In contrast to a number of previously published studies, our linear analysis makes use of smooth momentum distribution functions of the Maxwell-Juttner form. The three competing classes of instabilities, namely, two-stream, filamentation, and oblique modes, are dealt with in a unified manner, no approximation being made regarding the beam-plasma densities, temperatures, and drift energies. We investigate the hierarchy between the competing modes, paying particular attention to the relatively poorly known quasielectrostatic oblique modes in the regime where they govern the system. The properties of the fastest growing oblique modes are examined in terms of the system parameters and compared to those of the dominant two-stream and filamentation modes.
TL;DR: In this article, a comparison between experiments and simulations revealed that the four-wave mixing mechanism is dominant for the far-infrared generation during two-color filamentation, while the transient photocurrent was the dominant mechanism for the generation of submillimetric (terahertz) waves.
Abstract: Tunable far-infrared laser pulses were generated efficiently during two-color filamentation in air. Understanding the creation of few-cycle far-infrared laser pulses is important since it is at the frontier between two possible generation mechanisms. The first one is the four-wave mixing generation, associated to the generation of wavelengths from ultraviolet up to mid-infrared laser pulses. The second process is the formation of transient photocurrent, which was recently used to describe the generation of submillimetric (terahertz) waves. Comparison between experiments and simulations revealed that the four-wave mixing mechanism is dominant for the far-infrared generation during two-color filamentation.
TL;DR: In this paper, the complex cubic Ginzburg-Landau equation was derived for amplified and nonlinearly saturated surface plasmon polaritons propagating and diffracting along a metal-dielectric interface.
Abstract: Using a multiple-scale asymptotic approach, we have derived the complex cubic Ginzburg-Landau equation for amplified and nonlinearly saturated surface plasmon polaritons propagating and diffracting along a metal-dielectric interface. An important feature of our method is that it explicitly accounts for nonlinear terms in the boundary conditions, which are critical for a correct description of nonlinear surface waves. Using our model we have analyzed filamentation and discussed the bright and dark spatially localized structures of plasmons.
TL;DR: Numerical modeling is used to propose an experiment capable of discriminating between the standard and the new intensity-dependent Kerr-effect models.
Abstract: According to a recent experiment, the instantaneous electronic Kerr effect in air exhibits a strong intensity dependence, the nonlinear refractive index switching sign and crossing over from a self-focusing to a de-focusing nonlinearity. A subsequent theoretical work has demonstrated that this has paradigm-changing consequences for the understanding of filamentation in air, so it is important to subject the idea of higher-order nonlinearities to stringent tests. Here we use numerical modeling to propose an experiment capable of discriminating between the standard and the new intensity-dependent Kerr-effect models.
TL;DR: In this article, the authors provide thorough details about the protocol that has been employed to infer the HOKE indices from the experiment and discuss potential sources of artifact in the experimental measurements of these terms and show that neither the value of the observed birefringence nor its inversion, nor the intensity at which it is observed, appear to be flawed.
Abstract: As a contribution to the ongoing controversy about the role of higher-order Kerr effect (HOKE) in laser filamentation, we first provide thorough details about the protocol that has been employed to infer the HOKE indices from the experiment. Next, we discuss potential sources of artifact in the experimental measurements of these terms and show that neither the value of the observed birefringence, nor its inversion, nor the intensity at which it is observed, appear to be flawed. Furthermore, we argue that, independently on our values, the principle of including HOKE is straightforward. Due to the different temporal and spectral dynamics, the respective efficiency of defocusing by the plasma and by the HOKE is expected to depend substantially on both incident wavelength and pulse duration. The discussion should therefore focus on defining the conditions where each filamentation regime dominates.
TL;DR: It is demonstrated that Candida albicans cells with CaSCH9 deleted have reduced cell sizes and show a delayed log-phase growth and that CaSch9p is an important regulator for the cell growth, filamentation and virulence of this human fungal pathogen.
Abstract: The target of rapamycin complex 1 (TORC1) is the central controller of growth in eukaryotic cells. As one of the downstream targets of TORC1, the protein kinase ScSch9p plays multiple roles in stress resistance, longevity and nutrient sensing in Saccharomyces cerevisiae. In this study, we demonstrate that Candida albicans cells with CaSCH9 deleted have reduced cell sizes and show a delayed log-phase growth. In addition, deletion of CaSCH9 renders C. albicans cells sensitive to rapamycin, caffeine and sodium dodecyl sulfate. Similar to ScSCH9, deletion of CaSCH9 also causes C. albicans cells to become sensitive to cations, but does not lead to a defect in the utilization of galactose. Furthermore, deletion of CaSCH9 affects the filamentation of C. albicans cells and attenuates the virulence in a mouse mode of systemic candidiasis. Therefore, CaSch9p is an important regulator for the cell growth, filamentation and virulence of this human fungal pathogen.
TL;DR: In this article, the authors studied the analogue geometry induced by the filament and showed that one of the most evident features of filamentation, namely conical emission, may be precisely reconstructed from the geodesics.
Abstract: Ultrashort laser pulse filaments in dispersive nonlinear Kerr media induce a moving refractive index perturbation which modifies the spacetime geometry as seen by co-propagating light rays. We study the analogue geometry induced by the filament and show that one of the most evident features of filamentation, namely conical emission, may be precisely reconstructed from the geodesics. We highlight the existence of favorable conditions for the study of analogue black hole kinematics and Hawking-type radiation.
TL;DR: In this article, the instantaneous electronic Kerr effect in air exhibits a strong intensity dependence, the nonlinear refractive index switching sign and crossing over from a self-focusing to a defocusing nonlinearity.
Abstract: According to a recent experiment, the instantaneous electronic Kerr effect in air exhibits a strong intensity dependence, the nonlinear refractive index switching sign and crossing over from a self-focusing to a defocusing nonlinearity. A subsequent theoretical work has demonstrated that this has paradigm-changing consequences for the understanding of filamentation in air, so it is important to subject the idea of higher-order nonlinearities to stringent tests. Here we use numerical modeling to propose an experiment capable of discriminating between the standard and the new intensity-dependent Kerr-effect models.
TL;DR: In this paper, the early stage development of the filamentation instability of an initially unmagnetized plasma, which is relevant for both collisionless shock formation and reconnection dynamics in relativistic astrophysical outflows, as well as for laboratory astrophysics experiments, is presented.
Abstract: Radiation from many astrophysical sources, e.g. gamma-ray bursts and active galactic nuclei, is believed to arise from relativistically shocked collisionless plasmas. Such sources often exhibit highly transient spectra evolving rapidly, compared with source lifetimes. Radiation emitted from these sources is typically associated with non-linear plasma physics, complex field topologies and non-thermal particle distributions. In such circumstances a standard synchrotron paradigm may fail to produce accurate conclusions regarding the underlying physics. Simulating spectral emission and spectral evolution numerically in various relativistic shock scenarios is then the only viable method to determine the detailed physical origin of the emitted spectra. In this Letter we present synthetic radiation spectra representing the early stage development of the filamentation (streaming) instability of an initially unmagnetized plasma, which is relevant for both collisionless shock formation and reconnection dynamics in relativistic astrophysical outflows, as well as for laboratory astrophysics experiments. Results were obtained using a highly efficient "in situ" diagnostics method, based on detailed particle-in-cell modeling of collisionless plasmas. The synthetic spectra obtained here are compared with those predicted by a semi-analytical model for jitter radiation from the filamentation instability, the latter including self-consistent generated field topologies and particle distributions obtained from the simulations reported upon here. Spectra exhibit dependence on the presence - or absence - of an inert plasma constituent, when comparing baryonic plasmas (i.e. containing protons) with pair plasmas. The results also illustrate that considerable care should be taken when using lower-dimensional models to obtain information about the astrophysical phenomena generating observed spectra.
TL;DR: In this article, the early stage development of the filamentation instability of an initially unmagnetized plasmas was modeled using a particle-in-cell (PIC) model.
Abstract: Radiation from many astrophysical sources, e.g., gamma-ray bursts and active galactic nuclei, is believed to arise from relativistically shocked collisionless plasmas. Such sources often exhibit highly transient spectra evolving rapidly compared with source lifetimes. Radiation emitted from these sources is typically associated with nonlinear plasma physics, complex field topologies, and non-thermal particle distributions. In such circumstances, a standard synchrotron paradigm may fail to produce accurate conclusions regarding the underlying physics. Simulating spectral emission and spectral evolution numerically in various relativistic shock scenarios is then the only viable method to determine the detailed physical origin of the emitted spectra. In this Letter, we present synthetic radiation spectra representing the early stage development of the filamentation (streaming) instability of an initially unmagnetized plasma, which is relevant for both collisionless shock formation and reconnection dynamics in relativistic astrophysical outflows as well as for laboratory astrophysics experiments. Results were obtained using a highly efficient in situ diagnostics method, based on detailed particle-in-cell modeling of collisionless plasmas. The synthetic spectra obtained here are compared with those predicted by a semi-analytical model for jitter radiation from the filamentation instability, the latter including self-consistent generated field topologies and particle distributions obtained from the simulations reported upon here. Spectra exhibit dependence on the presence—or the absence—of an inert plasma constituent, when comparing baryonic plasmas (i.e., containing protons) with pair plasmas. The results also illustrate that considerable care should be taken when using lower-dimensional models to obtain information about the astrophysical phenomena generating observed spectra.
TL;DR: In this paper, the authors experimentally and numerically characterize multiple filamentation of laser pulses with incident intensities of a few TW/cm2, and observe a new propagation regime where the filament density saturates.
Abstract: We experimentally and numerically characterize multiple filamentation of laser pulses with incident intensities of a few TW/cm2. Propagating 100 TW laser pulses over 42 m in air, we observe a new propagation regime where the filament density saturates. As also evidenced by numerical simulations in the same intensity range, the total number of filaments is governed by geometric constraints and mutual interactions among filaments rather than by the available power in the beam.
TL;DR: In this paper, the authors demonstrate that laser filamentation provides high intensity plasma strings of micrometric diameters and lengths of tens of centimeters, which can be used for remotely drilling and cutting metals and biological materials such as flesh and bones.
Abstract: Laser filamentation provides high intensity plasma strings of micrometric diameters and lengths of tens of centimeters. We demonstrate that these filaments can be used for remotely drilling and cutting metals and biological materials such as flesh and bones. Since no tight focusing is needed, complex 3D shapes can be machined without any adjustment of the laser while processing.
TL;DR: In this paper, a detailed model of plasma dynamics, which selfconsistently integrates plasma-kinetic, Navier-Stokes, electron heat conduction, and electron-vibration energy transfer equations, is used to quantify the limitations on the lifetime of microwave plasma waveguides induced in the atmosphere through filamentation with high-intensity ultrashort laser pulses further sustained by long laser pulses.
Abstract: A detailed model of plasma dynamics, which self-consistently integrates plasma-kinetic, Navier–Stokes, electron heat conduction, and electron-vibration energy transfer equations, is used to quantify the limitations on the lifetime of microwave plasma waveguides induced in the atmosphere through filamentation with high-intensity ultrashort laser pulses further sustained by long laser pulses. We demonstrate that a near-infrared or midinfrared laser pulse can tailor plasma decay in the wake of a filament, efficiently suppressing, through electron temperature increase, the attachment of electrons to neutral species and dissociative recombination, thus substantially increasing the plasma-guide lifetime and facilitating long-distance transmission of microwaves.
TL;DR: In this paper, the terahertz (THz) emission from a dc-biased two-color femtosecond laser-induced filament in air was systematically investigated and a polarization analysis demonstrated that the THz emission could be the sum of two components: one generated by two-colour laser induced filamentation and the second induced by the external dc electric field.
Abstract: The generation of terahertz (THz) emission from a dc-biased two-color femtosecond laser-induced filament in air was systematically investigated. A polarization analysis demonstrated that the THz emission could be the sum of two components: one generated by two-color laser-induced filamentation and the second induced by the external dc electric field. The first component is mostly from four-wave mixing process and a transient transverse electric current under the action of the external dc field could be responsible for the second THz emission.
TL;DR: It is demonstrated that during growth in contact with a semi‐solid surface, activation of a MAP kinase, Cek1p, is promoted, in part, by a plasma membrane protein termed Dfi1p and results in invasive filamentation.
Abstract: Growth of cells in contact with an abiotic or biological surface profoundly affects cellular physiology. In the opportunistic human pathogen, Candida albicans, growth on a semi-solid matrix such as agar results in invasive filamentation, a process in which cells change their morphology to highly elongated filamentous hyphae that grow into the matrix. We hypothesized that a plasma membrane receptor-type protein would sense the presence of matrix and activate a signal transduction cascade, thus promoting invasive filamentation. In this communication, we demonstrate that during growth in contact with a semi-solid surface, activation of a MAP kinase, Cek1p, is promoted, in part, by a plasma membrane protein termed Dfi1p and results in invasive filamentation. A C. albicans mutant lacking Dfi1p showed reduced virulence in a murine model of disseminated candidiasis. Dfi1p is a relatively small, integral membrane protein that localizes to the plasma membrane. Some Dfi1p molecules become cross-linked to the carbohydrate polymers of the cell wall. Thus, Dfi1p is capable of linking the cell wall to the plasma membrane and cytoplasm.
TL;DR: In this paper, a block-structured adaptive mesh refinement (SMEF) code is proposed to describe the large and intermediate-scale dynamics of reconnection flow with highly reduced request for number of grid points.
TL;DR: An increase by 1 order of magnitude of the overall terahertz power is found when the two filaments are coherently linked on-axis, leading to a single longer concatenated filament.
Abstract: We investigate the emission of terahertz (THz) radiation from two laser filaments in air. An increase by 1 order of magnitude of the overall THz power is found when the two filaments are coherently linked on-axis, leading to a single longer concatenated filament. The observed enhancement is found to be the same for the cases of single-color and two-color filamentation approaches.
TL;DR: In this article, higher-order nonlinear indices of air and argon have a dominant contribution to both focusing and defocusing in ultrashort laser pulses over most of the spectrum.
Abstract: Based on numerical simulations, we show that higher-order nonlinear indices (up to ${n}_{8}$ and ${n}_{10}$, respectively) of air and argon have a dominant contribution to both focusing and defocusing in the self-guiding of ultrashort laser pulses over most of the spectrum. Plasma generation and filamentation are therefore decoupled. As a consequence, ultraviolet wavelength may not be the optimal wavelength for applications requiring to maximize ionization.