Distortion-free guiding of 0.2 /spl times/ 10/sup 18/ W/cm/sup 2/ pulses through a fully-ionized 1.5 cm He plasma channel

Summary from only given. Plasma waveguides capable of guiding relativistically intense fs laser pulses without optical distortion are essential to developing GeV-scale Laser Wakefield (LWF) Accelerators and coherent short-wavelength sources. We report the highest intensity-length product (0.2/spl times/10/sup 18/ W/cm/sup 2/ /spl times/ 1.5 cm) to date for distortion-free guiding. We generated our channels in a backfill of He gas (300-700 Torr) using a modification of a method developed by Milchberg, who line-focused /spl sim/ 100 ps, /spl sim/ 0.3 J Nd:YAG laser pulses to intensities of /spl sim/ 10/sup 13/ W/cm/sup 2/ into a gas using an axicon. This intensity readily field-ionizes high-Z gases (e.g. Ar, N/sub 2/), thus initiating the channel-forming process, but forms an incompletely-ionized channel, in which relativistically intense pulses suffer ionization-induced phase distortion during guiding and ionization-induced defocusing when entering the channel. Indeed we observe distorted exit mode and spectrum and only 5% throughput when we attempt to guide a pulse at /spl ges/10/sup 17/ W/cm/sup 2/ through a nitrogen channel.