Production and characterization of a fully-ionized He plasma channel

摘要

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 ～ 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 fs pulses suffered substantial ionization-induced blueshifts after propagating through Ar and Ne channels of similar dimensions.