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Laser filamentation in water allows investigation of many nonlinear effects such as plasma formation, supercontinuum generation and filamentation, without a need to worry about the damage of the sample. The liquid phase of matter also gives opportunity to characterize the energy deposition into the medium and the cavitation induced by abrupt heating of the localized region.
We demonstrate the coupling of microwave radiation into a plasma channel formed by laser filamentation in air, leading to the amplification by two orders of magnitude of longitudinal oscillations of the plasma. Transfer of this longitudinal excitation toward unexcited region of the plasma column occurs over >10 cm, in good agreement with a theoretical model describing the propagation of a TM wave...
Acoustic signals generated by filamentation of TW laser pulses in water are characterized experimentally and numerically revealing a strong influence of the input pulse duration on the shape of the acoustic signal.
The relaxation of a plasma grating resulting from the interference of two crossing laser filaments in molecular and atomic gases is studied experimentally. Dissipation of the grating fringes is dominated by ambipolar diffusion in atomic gases and by a combination of ambipolar diffusion and collision-assisted free electron recombination in molecular gases. A theoretical model of the grating evolution...
Interaction between a large number of conventional infrared filaments in air leads to the emergence over meter long distance of plasma channels one order of magnitude denser than standard filaments. Simulations reproduce well these features.
Propagation of femtosecond pulses at 800 and 400 nm is studied in water. Acoustic signals generated with MW to TW laser power are characterized, showing a directed and broadband emission in the band 0–20 MHz.
We present results of an experimental study aimed at producing a compact Marx generator consisting of three to six stages in series. A continuous plasma column is used to trigger simultaneously each element of the generator. This plasma channel is created by the filamentation of an intense femtosecond laser pulse (200–250 mJ, 700 fs @ 800 nm) from a Ti: Sapphire chirped pulse amplification laser chain...
The propagation of intense ultrashort laser pulses in water is affected by group velocity dispersion and nonlinear effects such as self-focusing and multiphoton absorption [1]. For a laser beam with an input peak power exceeding a few MW propagating in water, a filamentation phenomenon can occur producing a self contraction of the beam accompanied by the formation of an extended plasma channel [2]...
In recent years great progress has been made on remote generation and detection of THz radiation produced in air by intense femtosecond laser pulses [1, 2]. We present here results showing that it is possible to control the directionality of the Terahertz radiation emitted by two adjacent femtosecond laser filaments formed in air. Calculations for two neighboring filaments predict that the THz emission...
During propagation of intense laser pulses through atmosphere, owing to a dynamic competition between Kerr self-focusing, diffraction and ionization induced defocusing, a contracted beam of high peak intensity can be formed over long distances, provided the pulse input power exceeds a critical value (Pc ∼ 5 GW at 800 nm). During this process called filamentation [1], the pulse leaves in its wake a...
Plasma antennas, where plasma replaces metal as the conducting element, have long been known and used [1]. However, most designs use low-pressure plasmas confined inside solid dielectric vessels. We experimentally demonstrated a functional plasma antenna in air, which brings about many advantages like tunability in a large frequency range (100 MHz–1 GHz), stealth when de-activated and quick reconfiguration...
Optical phase conjugation is well known for its time reversal properties [1]. A phase conjugate mirror is formed when two laser beams of same frequency w meet from opposite directions in a transparent nonlinear medium. When a probe beam is retro-reflected by an optical phase conjugate mirror, wavefront distortions induced by a phase object are removed after re-crossing this object [2, 3]. In this...
We study the guiding effect of femtosecond laser filaments on high-voltage electric discharges generated by a compact Tesla coil. Meter scale repetitive discharges are demonstrated.
We demonstrate the use of a plasma column created by femtosecond filamentation and heated by a high-voltage discharge from a Tesla coil as an effective radio-frequency emitting antenna.
An investigational AS02 v -adjuvanted hepatitis B (HB-AS02) was compared with a licensed conventional recombinant hepatitis B vaccine (HBVAXPRO™; Sanofi Pasteur MSD, Lyon, France) in pre-dialysis, peritoneal dialysis and hemodialysis patients aged ≥18 years who had failed either to respond to prior vaccination with a conventional hepatitis B vaccine (Study A; n=251) or to maintain protective...
We show for the first time that filaments are able to divert electric discharges from their normal path. Comparison between negative and positive discharge polarities reveals important differences in the guiding mechanism.
Currents circulating in the plasma column of filaments in air are detected with a fast current monitor. The currents can be amplified with circularly polarized light.
Spontaneous currents inside the plasma column of filaments of N2 and Argon circulate in opposite directions. A competition between the laser Lorentz force and a Coulomb wake force explains the difference.
We present a compact and energy-scalable crossed polarized wave generation setup with waveguide filtering. A 1.4 mJ, 14.5 fs FTL, 10−4 contrast ratio enhanced XPW pulse is produced with 11 mJ, 40 fs input pulse.
We experimentally demonstrate the revival of short lived femtosecond laser induced plasma channels in air by a nanosecond laser pulse up to several milliseconds after plasma recombination. Such revived plasma channel is generated over 50 cm using a Bessel-like nanosecond laser beam.
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