Search

International audience; The wavefront of an injection-seeded soft x-ray laser beam generated by amplification of high-harmonic pulses in a lambda = 18.9 nm molybdenum plasma amplifier was measured by a Hartmann wavefront sensor with an accuracy of lambda/32 root mean square (rms). A significant improvement in wavefront aberrations of 0.51 +/- 0.03 lambda rms to 0.23 +/- 0.01 lambda rms was observed as a function of plasma column length. The variation of wavefront characteristic as a function time delay between the injection of the seed and peak of soft x-ray amplifier pump was studied. The measurements were used to reconstruct the soft x-ray source and confirm its high peak brightness. (C) 2013 Optical Society of America

International audience; Seeding plasma-based soft-x-ray lasers (PBSXRL) with high order harmonics (HOH) has been demonstrated in plasmas created from gas targets (Zeitoun et al. in Nature 431:426, 2004) and solid targets (Wang et al. in Nat. Photonics 2:94, 2008), obtaining 1 mu J, 1 ps pulses. Reaching multi-microJoule, hundreds of fs regime is the ultimate goal. Recent papers (Oliva et al. in Opt. Lett. 34(17):26402642, 2009; Phys. Rev. E 82(5):056408, 2010) showed that increasing the width (up to 1 mm) of the plasma increases the amplification surface and improves the gain zone properties. Up to 20 mu J could be extracted when seeding but the temporal duration and profile was not studied. Simulations show that the HOH is weakly amplified whereas most of the energy is within a long (several picoseconds) wake induced by the HOH (Al'miev et al. in Phys. Rev. Lett. 99(12):123902, 2007; Kim et al. in Phys. Rev. Lett. 104:053901, 2010). Amplified Spontaneous Emission (ASE) is also present in the output beam. Using the 1D Maxwell-Bloch code DeepOne (Oliva et al. in Phys. Rev. A 84(1):013811, 2011) we will show that fully coherent, wake and ASE-suppressed, 21.6 mu J, 80 fs pulse can be obtained when optimizing at the same time both the seed and the plasma conditions

International audience; The amplification of high-order harmonics (HOH) in a plasma-based amplifier is a multiscale, temporal phenomenon that couples plasma hydrodynamics, atomic processes, and HOH electromagnetic fields. We use a one-dimensional, time-dependent Maxwell-Bloch code to compare the natural amplification regime and another regime where plasma polarization is constantly forced by the HOH. In this regime, a 10-MW (i.e., 100 times higher than current seeded soft x-ray laser power), 1.5-mu J, 140-fs pulse free from the parasitic temporal structures appearing on the natural amplification regime can be obtained.

International audience; Experimental results of a two-stage Ni-like Ag soft X-ray laser operated in a seed-amplifier configuration are presented. Both targets were pumped applying the double-pulse grazing incidence technique with intrinsic travelling wave excitation. The injection of the seed X-ray laser into the amplifier target was realized by a spherical mirror. The results show amplification of the seed X-ray laser and allow for a direct measurement of the gain lifetime. The experimental configuration is suitable for providing valuable input for computational simulations. (C) 2012 Optical Society of America

International audience; The wavefront of a lambda=18.9 nm soft x-ray beam from an injection-seeded plasma amplifier was measured using a Hartmann sensor. An optical quality superior to that of the seed, up to lambda/7 rms, was obtained. (C) 2013 Optical Society of America