RESUMEN
We investigate the coherence of plasma-based soft X-ray laser (XRL) for different conditions that can alter the electron density in the gain region. We first measure the source temporal coherence in amplified spontaneous emission (ASE) mode. We develop a data analysis procedure to extract both its spectral width and pulse duration. These findings are in agreement with the spectral line shape simulations and seeded operation experimental results. Utilizing the deduced spectral width and pulse duration in a one-dimensional Bloch-Maxwell code, we reproduce the experimental temporal coherence properties of the seeded-XRL. Finally, we demonstrate efficient lasing in ASE and seeded mode at an electron density two times higher than the routine conditions. In this regime, using Bloch-Maxwell modeling, we predict the pulse duration of the seeded XRL to be â¼500fs.
RESUMEN
A quantitative interpretation method is described for experiments involving the linear autocorrelation of partially coherent extreme-ultraviolet (XUV) pulses, generated by either x-ray free-electron lasers or plasma-based XUV lasers. A recently published modeling method for partially coherent pulses is numerically implemented in that specific case. Analytical expressions for the statistical root-mean-square average of the fringe visibility are derived. The method yields unambiguous information on both the coherence time and the pulse duration, providing a valuable data interpretation tool.
RESUMEN
Development of efficient soft x-ray laser plasma amplifiers adapted to seeded operation, requires a better control over amplifier transverse spatial extent, brilliance control and gain lifetime. Here it is shown that pumping the plasma amplifier with one long and two short pump pulses (1L2S) provides advantages in terms of control for the specified parameters in the case of Ni-like Ag x-ray laser. Also, significant tunability of the gain lifetime in the 1L2S pumping scheme for Ne-like Ti x-ray laser is observed. Direct harmonics seeding and chirped harmonics seeding amplification approaches may benefit from the control of the gain lifetime, in terms of better use of the pump energy and as a way to reduce the amplified spontaneous emission in x-ray lasers.
RESUMEN
We study how the degree of temporal coherence of plasma-based extreme ultraviolet lasers operated in the amplification of the spontaneous emission mode is encoded in the shape of the linear autocorrelation function, which is obtained from the variation of the fringe visibility while varying the delay in a variable path-difference interferometer. We discuss the implications of this effect when the technique is used to infer the spectral properties of the source. Our numerical simulations, based on a partial coherence model developed by other authors for x-ray free electron lasers, are in good agreement with previously reported sets of measurements, illustrating similar statistical properties for both sources.
RESUMEN
An expression is proposed for a threshold discriminating between classical quasi-steady-state amplification and a strong pumping regime where a new dynamic behavior shows up in plasma-based extreme-ultraviolet (XUV) lasers. The criterion derived is applied to laser systems currently investigated in various laboratories. It is found that only high-gain XUV laser systems can be driven in that dynamic regime, associated with Rabi oscillations. For those systems, the small-signal dynamic gain accounting for the exponential amplification of the laser intensity is shown to be significantly smaller than the adiabatic value usually inferred from numerical simulations.