Compact high repetition rate soft x-ray lasers: A doorway to high intensity coherent soft x-ray science on a table-top

We discuss recent advances in high repetition rate table-top soft x-ray lasers that allow the generation of laser beams in the 25-100 eV photon energy region with peak spectral brightness that surpasses by several orders of magnitude that of undulators in third generation synchrotrons, enabling new applications. These advances include the demonstration of 5 Hz repetition rate table-top soft x-ray lasers that operate in the gain-saturation regime to produce intense beams at wavelengths ranging from 13.2 to 32.6 nm, and the observation of lasing at wavelengths down to 10.9 nm. The results were obtained by collisional electron impact excitation of highly ionized atoms in dense plasmas efficiently heated with picosecond optical laser pulses of only 1 J energy. Further improvement in the brightness of these compact sources was obtained seeding the soft x-ray amplifiers with high harmonic pulses. We have demonstrated the saturated amplification of high harmonic seed pulses in a dense transient collisional soft x-ray laser amplifier medium created by heating a solid titanium target. Amplification of the seed pulses in the 32.6 nm line of Ne-like Ti generated laser pulses of sub-picosecond duration that were measured to approach full spatial coherence. The scheme is scalable to produce extremely bright lasers at very short wavelength with full temporal and spatial coherence. These new compact lasers are allowing the implementation of a variety of table-top experiments with intense soft x-ray laser light.