Transformation of strong picosecond pulses in radiation with an extended quasirotational spectrum during self-focusing in high-pressure hydrogen |
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Authors: | V B Morozov A N Olenin V G Tunkin |
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Institution: | (1) International Science-Educational Laser Center, M. V. Lomonosov Moscow State University, 119899 Moscow, Russia |
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Abstract: | Radiation with a spectrum representing a discrete analog of the extended spectrum observed in the generation of a supercontinuum
in gases is generated in the self-focusing of 30-ps pulses with a wavelength of 1.06 μ]m in hydrogen at pressures up to 120 atm. The spectrum contains lines with similar intensities, an average frequency spacing
approximately equal to the rotational transition frequency in hydrogen (587 cm−1), and a smooth spatial profile. The lines consist of several vibrational-rotational components. As the pressure is increased,
the spectral lines are transformed so that at a pressure above 60 atm each line in the spectrum contains one or two components
formed as a result of the smaller number of cascade (rotational and vibrational) processes. Self-focusing is manifested in
the occurrence of a radiating channel up to 12 cm in length. The formation of a channel of this length is associated mainly
with the variation of the refractive index in vibrational excitation of the hydrogen molecules by electrons heated in the
pump field.
Zh. éksp. Teor. Fiz. 115, 479–493 (February 1999) |
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