Demonstration of a spatial filtering amplifier for high-order harmonics

Abstract

We report what is to our knowledge the first demonstration of spatial filtering of a high-order harmonic beam into a soft-x-ray laser plasma amplifier at 32.8 nm. After amplification the seed energy is enhanced by a factor of 50, and the beam profile of the amplified beam exhibits an Airy-like shape due to the spatial filtering by the optical field ionized plasma. Moreover, the transverse coherence of the spatially filtered amplified beam is strongly enhanced, resulting in the generation of a peak coherent power of 0.9 x 10(5) to 1.8 x 10(5) W.

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

“…Note that the fringe visibility is lower than 100%. This is not due to a degradation of the harmonic beam spatial coherence by the plasma [3] but rather to the experimental setup. A fringe actually covers around 5 CCD pixels, causing a loss of information.…”

“…When the amplifier is properly seeded, the spatial quality of the output beam is dramatically enhanced. It has been demonstrated to be highly collimated, with a Gaussian transverse profile, and spatially coherent [1,3,4], up to the diffraction limit [5,7]. In addition to being more energetic than either the ASE or the unamplified harmonic, a seeded soft-x-ray laser pulse is temporally fully coherent, thus having a duration (a few picoseconds [6]) predominantly limited by Fourier transform [8].…”

Picosecond imaging of low-density plasmas by electron deflectometry

“…Owing to their unique properties, OFI plasmas have gained applications in various fields, such as inertial confinement fusion [1], generation of high-energy ions [2,3], x-ray emission [4,5], and x-ray lasers [6][7][8][9][10]. The parameters of OFI plasmas can be determined by a variety of diagnostic methods.…”

Spatial properties of odd and even low order harmonics generated in gas

“…Associating focusing optics and gratings allows to separate correctly the different orders, but this usually introduce a lot of aberration and generally one can only get information in the vertical dimension of the beam 57 . One quite elaborated solution could be that of selecting the desired harmonic by a second mechanism such as amplification in plasma based soft X-ray laser 58 or FEL 59 , but in these cases the shape of the amplified harmonics would be largely dependent of the amplification medium. In summary, for high orders it is almost impossible to clearly distinguish behaviors of odd and even harmonics generation.…”