Nonlinear transformation of a spectrum of femtosecond laser pulses in a gas-filled microcapillary |
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Authors: | K G Shaynurova S A Bakhramov A M Kokhkharov U K Makhmanov E A Zakhidov |
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Institution: | 1.Akadempribor Scientific-Production Association,Academy of Sciences of the Republic of Uzbekisan,Tashkent,Uzbekistan;2.Heat Physics Department,Academy of Sciences of the Republic of Uzbekistan,Tashkent,Uzbekistan |
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Abstract: | Features of light pulse propagation and nonlinear optical transformation of the spectrum generated by titanium-sapphire laser
pulses (τ0.5 = 27 fs, λ0 = 790 nm) have been studied experimentally in a 50-cm cylindrical hollow waveguide (microcapillary with 280-μm diameter core)
filled with gaseous molecular nitrogen and helium. Stable guided propagation of light pulses with an intensity of ~1.5⋅1014 W/cm2 in the fundamental EH11 mode of the gas-filled capillary has been demonstrated. Exact focusing of the laser light made it possible to obtain rather
high relative (≥95%) and absolute (~60%) energy transmission efficiencies for the pulses at gas pressures equal to or lower
than 760 Torr. A method to determine the nonlinear phase shift of the pulses has been proposed. Values of the nonlinear refractive
index n2 ≈ 4.5⋅10–23 cm2/(W⋅Torr) (N2) and n2 ≈ 2.8⋅10–23 cm2/(W⋅Torr) (He) have been found. A short-wavelength shift in addition to the Kerr nonlinearity has been shown to be contributed
by the generated electron plasma at high pulse intensities (≥1014 W/cm2). |
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