Production And Characterization Of A Fully-Ionized He Plasma Channel
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We report guiding of intense (I = 1.3 +/- 0.7 x 10(17)W/cm(2)) 80 fs laser pulses with negligible spectral distortion through 1.5-cm-long preformed helium plasma channels. Channels were formed by axicon-focused Nd:YAG laser pulses of either 0.3 J energy, 100 ps duration, after pre-ionizing a 200-700 Torr backfill of He gas to n(e) similar to 10(16)cm(-3) with a pulsed electrical discharge; or 0.6-1.1 J energy, 400 ps duration, which required neither pre-ionization nor intentional impurities for seeding. Transverse interferometry showed that He was fully-ionized on the channel axis in both cases. Identical fis pulses suffered substantial ionization-induced blueshifts after propagating through Ar and Ne channels of similar dimensions.