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Gain dynamics in a soft-X-ray laser amplifier perturbed by a strong injected X-ray field


Seeding soft-X-ray plasma amplifiers with high harmonics has been demonstrated to generate high-brightness soft-X-ray laser pulses with full spatial and temporal coherence1,2,3. The interaction between the injected coherent field and the swept-gain medium has been modelled4,5. However, no experiment has been conducted to probe the gain dynamics when perturbed by a strong external seed field. Here, we report the first X-ray pump–X-ray probe measurement of the nonlinear response of a plasma amplifier perturbed by a strong soft-X-ray ultra-short pulse. We injected a sequence of two time-delayed high-harmonic pulses (λ = 18.9 nm) into a collisionally excited nickel-like molybdenum plasma to measure with femtosecond resolution the gain depletion induced by the saturated amplification of the high-harmonic pump and its subsequent recovery. The measured fast gain recovery in 1.5–1.75 ps confirms the possibility to generate ultra-intense, fully phase-coherent soft-X-ray lasers by chirped pulse amplification in plasma amplifiers6.

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Figure 1: Schematic of the set-up used to measure the gain dynamics in an injection-seeded soft-X-ray laser plasma amplifier.
Figure 2: Experimental measurement of the gain dynamics in a soft-X-ray plasma Ni-like Mo amplifier compared with results from a Maxwell–Bloch simulation.
Figure 3: Simulation of HH pump–HH probe and single stretched HH seed pulse amplification in a plasma soft-X-ray amplifier.


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The authors thank M. Fajardo and S. Sebban for discussions. This work was supported by the AMOS programme of the Office of Basic Energy Sciences, US Department of Energy, using equipment developed at the NSF ERC for Extreme Ultraviolet Science and Technology (NSF award MRI-ARRA 09-561) and by the LASERLAB3-INREX European project and SHYLAX plus CIBOR RTRA ‘Triangle de la Physique’ programmes.

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The concept of the experiment was proposed by Ph.Z. and the experiment was designed by J.J.R., Y.W., S.W., J.D. and Ph.Z. Modelling was performed by E.O., T.T.T.L., M.B., L.L., C.P., D.R. and Ph.Z. The experiment was set and realized by Y.W., S.W., L.L., M.B., L.Y., J.N., B.M.L. and J.J.R. All authors participated in data treatment and writing the article.

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Correspondence to Ph. Zeitoun or J. J. Rocca.

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The authors declare no competing financial interests.

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Wang, Y., Wang, S., Oliva, E. et al. Gain dynamics in a soft-X-ray laser amplifier perturbed by a strong injected X-ray field. Nature Photon 8, 381–384 (2014).

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