Observation of spectral gain narrowing in a high-order harmonic seeded soft-x-ray amplifier

Abstract

International audienceWe report an observation of spectral gain narrowing of a high-order harmonic amplified by a soft-x-ray optical-field-ionized plasma. The temporal coherence and spectral linewidth of both the seeded and unseeded soft-x-ray lasers were experimentally measured using a varying-path-difference interferometer. The results showed that the high-order harmonic is subject to a strong spectral narrowing during its propagation in the plasma amplifier without rebroadening at saturation. This is in good agreement with a radiative transfer calculation including gain narrowing and saturation rebroadening

Temporal coherence measurements of a seeded GRIP transient Ni-like Mo soft X-ray laser

“…For the same plasma length, the line width in seeded mode is a little larger than in the ASE mode, and the maximum visibility is a little larger. These conclusions are consistent with a previous experiment performed at LOA with an OFI-pumped X-ray [4,11].…”

“…The spectral line width is observed to decrease slightly, when increasing the 3.11 ± 0.25 2.60 ± 0.42 2.27 ± 0.34 2.18 ± 0.34 length of the plasma amplifier from 2 mm to 4 mm. Such behaviour is consistent with gain narrowing and was already observed in another experiment performed with the OFI seeded X-ray laser [4,11]. By comparing in Table 1 the values of the spectral width to the corresponding values of the coherence length it can be noted that these two quantities do not exhibit the same behaviour.…”

“…These applications are effected by the spatial and temporal coherence of these sources. Recent works report some exciting results for high quality x-ray laser [2][3][4]. The most interesting progress is the injection-seeded x-ray laser [5,6].…”

Spectral linewidth of a Ne-like Ar capillary discharge soft-x-ray laser and its dependence on amplification beyond gain saturation

“…This results in a very narrow laser line that is difficult to measure because its width is below the resolution of most existing spectrometers at this wavelength. Several measurements of the linewidth of different types of laser-pumped soft-x-ray lasers have been reported [22][23][24][25][26][27]. These measurements were conducted using either a custom-made spectrometer of extremely high resolution [22], or different types of interferometers [23][24][25][26][27].…”

Line profiles of Ni-like collisional XUV laser amplifiers: Particle correlation effects

“…There is an increasing interest in better understanding the spectral behaviour of plasma-based collisional XUV lasers in the last years [1,2,3,4,5]. The main reason is that the shortest pulse duration that was reached until now is limited to ∼ 1 picosecond [6] by the extremely narrow bandwidth of these sources.…”