RESUMEN
By seeding an optical-field-ionized population-inverted plasma amplifier with the 25th harmonic of an IR laser, we have achieved what we believe to be the first aberration-free laser beam in the soft x-ray spectral range. This laser emits within a cone of 1.34 mrad(1/e(2)) at a repetition rate of 10 Hz at a central wavelength of 32.8 nm. The beam exhibits a circular profile and wavefront distortions as low as lambda/17. A theoretical analysis of these results shows that this high beam quality is due to spatial filtering of the seed beam by the plasma amplifier aperture.
RESUMEN
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.