Dramatic enhancement of xuv laser output using a multimode gas-filled capillary waveguide

We report a significant increase of the output of a 41.8-nm Xe^8+ laser achieved by means of multimode guiding of high-intensity femtosecond laser pulses in a gas-filled dielectric capillary tube. The optimized lasing signal from a 15-mm-long capillary was nearly an order of magnitude higher than that from a gas cell of the same length. Simulations of the propagation of the pump laser pulse in the capillary confirmed that this enhancement is due to reflections from the capillary wall, which increase the length of the Xe^8+ plasma column generated. The influence of gas pressure and focusing position on the lasing is also presented.