Browsing by Subject "intensity laser-pulses"

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Femtosecond Pump-Probe Diagnostics Of Preformed Plasma Channels
(2004-12) Zgadzaj, R.; Gaul, E. W.; Matlis, N. H.; Shvets, G.; Debus, A.; Downer, M. C.; Zgadzaj, R.; Gaul, E. W.; Matlis, N. H.; Shvets, G.; Debus, A.; Downer, M. C.
We report on recent ultrafast pump-probe experiments 28 in He plasma waveguides using 800 nm, 80 fs pump pulses of 0.2 x 1018 W/cm2 peak guided intensity, and single orthogonally-polarized 800 nm probe pulses with similar to0.1% of pump intensity. The main results are: (1) We observe frequency-domain interference between the probe and a weak, depolarized component of the pump that differs substantially in mode shape from the injected pump pulse; (2) we observe spectral blue-shifts in the transmitted probe that are not evident in the transmitted pump. The evidence indicates that pump depolarization and probe blue-shifts both originate near the channel entrance.
Production And Characterization Of A Fully-Ionized He Plasma Channel
(2001-12) Gaul, E. W.; Le Blanc, S. P.; Rundquist, A. R.; Zgadzaj, R.; Matlis, N. H.; Langhoff, H.; Downer, M. C.; Gaul, E. W.; Le Blanc, S. P.; Rundquist, A. R.; Zgadzaj, R.; Langhoff, H.; Downer, M. C.
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.