High efficiency coupling and guiding of intense femtosecond laser pulses in preformed plasma channels in an elongated gas jet

We report coupling and guiding of pulses of peak power up to 0.3 TW in 1.5-cm-long preformed plasma waveguides, generated in a high repetition rate argon gas jet. Coupling of up to 52% was measured for 50-mJ, {~}110-fs pulses injected at times longer than 20 ns, giving guided intensities up to ~5×10¹⁶ W/cm². For short delays between waveguide generation and pulse injection, pulse shortening occurred, with this effect reduced either by increasing delay or injecting a prepulse into the waveguide. There is excessive taper at the waveguide ends, which results from reduced heating at the ends of the jet by the waveguide generation pulse.