Compression of X-ray Free Electron Laser pulses to attosecond duration

State of the art X-ray Free Electron Laser facilities currently provide the brightest X-ray pulses available, typically with mJ energy and several hundred femtosecond duration. Here we present one- and two-dimensional Particle-in-Cell simulations, utilising the process of stimulated Raman amplification, showing that these pulses are compressed to a temporally coherent, sub-femtosecond pulse at 8% efficiency. Pulses of this type may pave the way for routine time resolution of electrons in nm size potentials. Furthermore, evidence is presented that significant Landau damping and wave-breaking may be beneficial in distorting the rear of the interaction and further reducing the final pulse duration

Advantages to a diverging Raman amplifier

The plasma Raman instability can efficiently compress a nanosecond long high-power laser pulse to sub-picosecond duration. Although, many authors envisaged a converging beam geometry for Raman amplification, here we propose the exact opposite geometry; the amplification should start at the intense focus of the seed. We generalise the coupled laser envelope equations to include this non-collimated case. The new geometry completely eradicates the usual trailing secondary peaks of the output pulse, which typically lower the efficiency by half. It also reduces, by orders of magnitude, the initial seed pulse energy required for efficient operation. As in the collimated case, the evolution is self similar, although the temporal pulse envelope is different. A two-dimensional particle-in-cell simulation demonstrates efficient amplification of a diverging seed with only 0.3 mJ energy. The pulse has no secondary peaks and almost constant intensity as it amplifies and diverges

Optimization of plasma amplifiers

Plasma amplifiers offer a route to side-step limitations on chirped pulse amplification and generate laser pulses at the power frontier. They compress long pulses by transferring energy to a shorter pulse via the Raman or Brillouin instabilities. We present an extensive kinetic numerical study of the three-dimensional parameter space for the Raman case. Further particle-in-cell simulations find the optimal seed pulse parameters for experimentally relevant constraints. The high-efficiency self-similar behavior is observed only for seeds shorter than the linear Raman growth time. A test case similar to an upcoming experiment at the Laboratory for Laser Energetics is found to maintain good transverse coherence and high-energy efficiency. Effective compression of a 10 kJ , nanosecond-long driver pulse is also demonstrated in a 15-cm-long amplifier

Numerical simulations of photon acceleration occurring during the modulation of a long laser pulse in plasma

This chapter looks at numerical simulations of photon acceleration occurring during the modulation of a long laser pulse in plasm

Numerical studies of photon acceleration in laser wakefields

This chapter looks at numerical studies of photon acceleration in laser wakefield

Scaling laws for laser–plasma interaction derived with photon kinetic theory

In this report, we present a derivation of scaling laws for laser-plasma interaction in one-dimensional geometry, using photon kinetic theory. The interest in scaling laws arises from last year's experimental results on mono-energetic electron acceleration with the Astra laser. These results are considered a major breakthrough for laser-plasma accelerated electron bunches in terms of beam quality. Previously, the energy spectra were found to be typically Maxwellian, which made laser-plasma based electron sources of limited interest for applications. After the successful demonstration of mono- energetic acceleration, it is timely to address, among various other issues, the scalability to different laser and plasma parameters. The choice of photon kinetic theory for developing the scaling laws is motivated by its simplicity and the useful analogies between laser pulses and electron beams interacting with plasma due to the phase space representation of the electromagnetic field . The results presented in this paper are preliminary in the sense that only the laser pulse evolution is considered, not the electron acceleration. Also, we are planning to extend the model to three-dimensional geometry

Photon acceleration by laser produced wakefields on Astra

This chapter looks at photon acceleration by laser produced wakefields on Astr

Numerical Simulation of Plasma-Based Raman Amplification of Laser Pulses to Petawatt Powers

Contemporary high-power laser systems make use of solid-state laser technology to reach petawatt pulse powers. The breakdown threshold for optical components in these systems, however, demands beam diameters up to 1 m. Raman amplification of laser beams promises a breakthrough by the use of much smaller amplifying media, i.e., millimeter-diameter-wide plasmas. Through the first large-scale multidimensional particle-in-cell simulations of this process, we have identified the parameter regime where multipetawatt peak laser powers can be reached, while the influence of damaging laser-plasma instabilities is only minor. Snapshots of the probe laser pulse being amplified, generated using state-of-the-art visualization techniques, are presented.</p

Numerical simulation of plasma-based Raman amplification of laser pulses to petawatt powers

Contemporary high-power laser systems make use of solid-state laser technology to reach petawatt pulse powers. The breakdown threshold for optical components in these systems, however, demands beam diameters up to 1 m. Raman amplification of laser beams promises a breakthrough by the use of much smaller amplifying media, i.e., millimeter-diameter-wide plasmas. Through the first large-scale multidimensional particle-in-cell simulations of this process, we have identified the parameter regime where multipetawatt peak laser powers can be reached, while the influence of damaging laser-plasma instabilities is only minor. Snapshots of the probe laser pulse being amplified, generated using state-of-the-art visualization techniques, are presented