Raman Amplification of Laser Pulses in Microcapillary Plasmas (original) (raw)
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Raman amplification of ultrashort laser pulses in microcapillary plasmas
Physical Review E, 2002
Experimental evidences of Raman amplification of ultrashort pulses in microcapillary plasmas are presented. The amplification of 100-500 fs pulses was investigated in microcapillaries with different lengths. The experimental data, together with simulation results, indicate that the resonance condition for Raman amplification in high-density plasma, n e ϳ1Ϫ3ϫ10 20 cm Ϫ3 , existed only in a very short plasma column. Such an assumption makes it possible to reconcile the experimental results and theoretical predictions. Investigations in very short microcapillaries ͑0.2-0.5 mm͒ with a broadband seed pulse further support this hypothesis and the amplification factor is in agreement with the linear growth rate.
Development of a nanosecond-laser-pumped Raman amplifier for short laser pulses in plasma
Physics of Plasmas, 2009
Progress on developing a plasma amplifier/compressor based on stimulated Raman scattering of nanosecond laser pulses is reported. Generation of a millijoule seed pulse at a wavelength that is redshifted relative to the pump beam has been achieved using an external Raman gas cell. By interacting the shifted picosecond seed pulse and the nanosecond pump pulse in a gas jet plasma at a density of ϳ10 19 cm −3 , the upper limit of the pump intensity to avoid angular spray of the amplified seed has been determined. The Raman amplification has been studied as a function of the pump and seed intensities. Although the heating of plasma by the nanosecond pump pulse results in strong Landau damping of the plasma wave, an amplified pulse with an energy of up to 14 mJ has been demonstrated, which is, to the best of our knowledge, the highest output energy so far by Raman amplification in a plasma. One-dimensional particle-in-cell simulations indicate that the saturation of amplification is consistent with onset of particle trapping, which might be overcome by employing a shorter seed pulse.
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.
2005
Strongly coupled large-angle stimulated Raman scattering (LA SRS) of a short intense laser pulse develops in a plane plasma-filled capillary differently than in a plasma with open boundaries. Coupling the laser pulse to a capillary seeds the LA SRS in the forward direction sscattering angle smaller than p/2d and can thus produce a high instability level in the vicinity of the entrance plane. In addition, oblique mirror reflections off capillary walls partly suppress the lateral convection of scattered radiation and increase the growth rate of the SRS under arbitrary (not too small) angle. Hence, the saturated convective gain falls with an angle much slower than in an unbounded plasma and even for the near-forward SRS can be close to that of the direct backscatter. At a large distance, the LA SRS evolution in the interior of the capillary is dominated by quasi-one-dimensional leaky modes whose damping is related to the leakage of scattered radiation through the walls.
Amplification of Ultrashort Laser Pulses by a Resonant Raman Scheme in a Gas-Jet Plasma
Physical Review Letters, 2004
Raman amplification of subpicosecond laser pulses up to 95 times is demonstrated at corresponding frequencies in a gas-jet plasma. The larger amplification is accompanied by a broader bandwidth and shorter pulse duration. Theoretical simulations show a qualitative agreement with the measurements, and the effects of the plasma conditions and laser intensities are discussed.
Chirped pulse Raman amplification in plasma: high gain measurements
2009
High power short pulse lasers are usually based on chirped pulse amplification (CPA), where a frequency chirped and temporarily stretched "seed" pulse is amplified by a broad-bandwidth solid state medium, which is usually pumped by a monochromatic "pump" laser. Here, we demonstrate the feasibility of using chirped pulse Raman amplification (CPRA) as a means of amplifying short pulses in plasma. In this scheme, a short seed pulse is amplified by a stretched and chirped pump pulse through Raman backscattering in a plasma channel. Unlike conventional CPA, each spectral component of the seed is amplified at different longitudinal positions determined by the resonance of the seed, pump and plasma wave, which excites a density echelon that acts as a "chirped" mirror and simultaneously backscatters and compresses the pump. Experimental evidence shows that it has potential as an ultra-broad bandwidth linear amplifier which dispenses with the need for large compressor gratings.
Chirped pulse Raman amplification in plasma: high gain measurements
Harnessing Relativistic Plasma Waves as Novel Radiation Sources from Terahertz to X-Rays and Beyond, 2009
High power short pulse lasers are usually based on chirped pulse amplification (CPA), where a frequency chirped and temporarily stretched "seed" pulse is amplified by a broad-bandwidth solid state medium, which is usually pumped by a monochromatic "pump" laser. Here, we demonstrate the feasibility of using chirped pulse Raman amplification (CPRA) as a means of amplifying short pulses in plasma. In this scheme, a short seed pulse is amplified by a stretched and chirped pump pulse through Raman backscattering in a plasma channel. Unlike conventional CPA, each spectral component of the seed is amplified at different longitudinal positions determined by the resonance of the seed, pump and plasma wave, which excites a density echelon that acts as a "chirped" mirror and simultaneously backscatters and compresses the pump. Experimental evidence shows that it has potential as an ultra-broad bandwidth linear amplifier which dispenses with the need for large compressor gratings.
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.
Chirped pulse Raman amplification in plasma
New Journal of Physics, 2011
Raman amplification in plasma has been proposed to be a promising method of amplifying short radiation pulses. Here, we investigate chirped pulse Raman amplification (CPRA) where the pump pulse is chirped and leads to spatiotemporal distributed gain, which exhibits superradiant scaling in the linear regime, usually associated with the nonlinear pump depletion and Compton amplification regimes. CPRA has the potential to serve as a high-efficiency high-fidelity amplifier/compressor stage.
Large-Angle Stimulated Raman Scattering of Short Laser Pulses in Plasma
2000
The features of the large-angle stimulated Raman scattering of short laser pulses in a homogeneous underdense plasma are studied analytically. It is found that, for scattering angles that are not too close to zero, a steady-state regime of the convective amplification of unstable waves is established in the frame of reference comoving with the laser pulse. The problem of convective amplification in a two-dimensional region is solved in both weak- and strong-coupling regimes. It is shown that the steady-state envelopes of the scattered radiation and scattering plasma waves are two-dimensional in nature. It is found that, for a given scattering angle, the maximum possible spatial amplification at the trailing edge of the pulse is achieved if the ratio of the transverse to longitudinal size of the pulse is larger than the cotangent of one-half of the scattering angle.