Quasitransient backward Raman amplification of powerful laser pulses in dense plasmas with multicharged ions (original) (raw)
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Physics of Plasmas, 2011
It was proposed recently that powerful optical laser pulses could be efficiently compressed through backward Raman amplification in ionized low density solids, in spite of strong damping of the resonant Langmuir wave. It was argued that, even for nonsaturated Landau damping of the Langmuir wave, the energy transfer from the pump laser pulse to the amplified seed laser pulse can nevertheless be highly efficient. This work numerically examines such regimes of strong damping, called quasitransient regimes, within the simplest model that takes into account the major effects. The simulations indicate that compression of powerful optical laser pulses in ionized low density solids indeed can be highly efficient. V
Laser duration and intensity limits in plasma backward Raman amplifiers
Physics of Plasmas, 2012
The shortest duration and the largest non-focused intensity of laser pulses produced by means of backward Raman amplification (BRA) in plasmas are calculated. These limits occur in moderately undercritical plasmas and are imposed by combined effects of moderately small group velocity dispersion and relativistic electron nonlinearity of the amplified pulses. The efficient BRA range covered by this theory is broader than one known previously. This can be useful for BRA of x-ray pulses in regular or compressed solids and ultra-powerful optical pulses in the lowest density solids. V
Raman laser amplification in preformed and ionizing plasmas
Laser and Particle Beams, 2005
The recently proposed backward Raman laser amplification scheme utilizes the stimulated Raman backscattering in plasma of a long pumping laser pulse to amplify a short, frequency downshifted seed pulse. The output intensity for this scheme is limited by the development of forward Raman scattering (FRS) or modulational instabilities of the highly amplified seed. Theoretically, focused output intensities as high as 10 25 W/cm 2 and pulse lengths of less than 100 fs could be accessible by this technique for 1 µm lasers ⎯ an improvement of 10 4-10 5 in focused intensity over current techniques. Simulations with the particle-in-cell (PIC) code Zohar are presented which investigate the effects of FRS and modulational instabilities and of Langmuir wave breaking on the output intensity for Raman amplification. Using the intense seed pulse to photoionize the plasma simultaneous with its amplification (and hence avoid plasmas-based instabilities of the pump) is also investigated by PIC simulations. It is shown that both approaches can access focused intensities in the 10 25 W/cm 2 range.
Intense laser pulse amplification using Raman backscatter in plasma channels
Physics Letters A, 2002
It has been proposed that the Raman backscatter interaction in a plasma can be used to amplify ultra-intense laser pulses. To accomplish this, energy is transferred from a long drive pulse at frequency ω pump to an intense seed pulse at frequency ω seed , with a Langmuir plasma wave at frequency w p mediating the transfer; the frequencies are chosen to satisfy the resonant condition ω p = ω pump − ω seed. Diffraction of the pulses limits the interaction length in a uniform plasma, and hence the energy transfer between the pulses. However in a parabolic plasma density channel it is shown, through two-dimensional particle-incell simulations, that such a plasma channel can be used to guide both the amplified and drive pulses over an interaction distance much greater than a diffraction length. The seed pulse is amplified by a factor of more than 200 in energy for pulses whose widths are matched to the channel size, and achieve a peak intensity of more than 6 × 10 17 W/cm 2. Unmatched pump pulses are seen to generate much smaller gain.
Detuned Raman Amplification of Short Laser Pulses in Plasma
Physical Review Letters, 2000
The recently proposed scheme of so-called "fast compression" of laser pulses in plasma can increase peak laser intensities by 10 5 [ Phys. Rev. Lett. 82, 4448 (1999)]. The compression mechanism is the transient stimulated Raman backscattering, which outruns the fastest filamentation instabilities of the pumped pulse even at highly overcritical powers. This Letter proposes a novel nonlinear filtering effect that suppresses premature backscattering of the pump in a noisy plasma layer, while the desired amplification of a sufficiently intense seed persists with a high efficiency. The effect is of basic interest and also makes it robust to noise the simplest technologically fast compression scheme.
Plasma
The demand for high-intensity lasers has grown ever since the invention of lasers in 1960, owing to their applications in the fields of inertial confinement fusion, plasma-based relativistic particle accelerators, complex X-ray and gamma-ray sources, and laboratory astrophysics. To create such high-intensity lasers, free-running lasers were either Q-switched or mode-locked to increase the peak power to the gigawatt range. Later, chirped pulse amplification was developed, allowing the generation of peak power up to 1012 W. However, the next generation of high-intensity lasers might not be able to be driven by the solid-state technology alone as they are already operating close to their damage thresholds. In this scenario, concepts of amplification based on plasmas has the potential to revolutionize the laser industry, as plasma is already a broken-down medium, and hence does not pose any problems related to the damage thresholds. On the other hand, there are many other aspects that n...
Operating regime for a backward Raman laser amplifier in preformed plasma
Physics of Plasmas, 2003
A critical issue in the generation of ultraintense, ultrashort laser pulses by backward Raman scattering in plasma is the stability of the pumping pulse to premature backscatter from thermal fluctuations in the preformed plasma. Malkin et al. ͓Phys. Rev. Lett. 84, 1208 ͑2000͔͒ demonstrated that density gradients may be used to detune the Raman resonance in such a way that backscatter of the pump from thermal noise can be stabilized while useful Raman amplification persists. Here plasma conditions for which the pump is stable to thermal Raman backscatter in a homogeneous plasma and the density gradients necessary to stabilize the pump for other plasma conditions are quantified. Other ancillary constraints on a Raman amplifier are also considered to determine a specific region in the T e-n e plane where Raman amplification is feasible. By determining an operability region, the degree of uncertainty in density or temperature tolerable for an experimental Raman amplifier is thus also identified. The fluid code F3D ͓R. L. Berger et al., Phys. Plasmas 5, 4337 ͑1998͔͒, which includes the effects of thermal fluctuations, is used to verify these analytic estimates.
Simulations of Raman laser amplification in ionizing plasmas
Physics of Plasmas, 2003
By using the amplifying laser pulse in a plasma-based backward Raman laser amplifier to generate the plasma by photoionization of a gas simultaneous with the amplification process, possible instabilities of the pumping laser pulse can be avoided. Particle-in-cell simulations are used to study this amplification mechanism, and earlier results using more elementary models of the Raman interaction are verified [D.S.Clark and N.J.Fisch., Phys.Plasmas, 9(6):2772-2780, 2002]. The effects (unique to amplification in ionizing plasmas and not included in previous simulations) of blue-shifting of the pump and seed laser pulses and the generation of a wake are observed not significantly to impact the amplification process. As expected theoretically, the peak output intensity is found to be limited to I ∼ 10 17 W/cm 2 by forward Raman scattering of the amplifying seed. The integrity of the ionization front of the seed pulse against the development of a possible transverse modulation instability is also demonstrated.
Broad-band linear Raman chirped pulse amplification in plasma
2015
The advent of laser systems based on the chirped pulse amplification (CPA) technique has allowed the production of femtosecond pulses with intensities up to 1021W/cm2. However reaching these intensities and beyond is proving very expensive and the development of future laser systems may need to use a different technology. Amplifiers based on stimulated Raman backscattering (RBS) in plasma could represent the next generation of amplifiers [1, 2]. Ra-man backscattering is a very promising means of transferring energy from a long pump pulse to a short probe pulse. Moreover, plasma can withstand extremely high power densities and therefore is a very robust gain medium. Raman backscattering in plasma can be simply characterized as the resonant decay of an incident photon into a frequency downshifted scattered photon and an electron plasma wave (a Langmuir wave). The frequency and wave number matching conditions are given by: ω0 = ω1+ωp, k0 = k1+ kp (1) where ω0,1,p and k0,1,p are the fre...