Investigation of highly directional supercontinuum characteristics in nitrogen
D.M. Lubenko, I.A. Zyatikov, V.F. Losev, S.V. Alekseev
High Current Electronics Institute of the Siberian Branch of the RAS, Tomsk, Russia
Keywords: filament, supercontinuum, aberration focusing, radiation pulse, wavelength, divergence
Abstract
Highly directional supercontinuum (HDSC) is a unique source of broadband coherent radiation. To create such a source, it is necessary to know the parameters and conditions of its occurrence. The article presents the results of experimental study of the conditions for HDSC generation in gaseous nitrogen pumped by a radiation pulse with wavelength of 950 nm, duration of 70 fs, and energy of 3-6 mJ. The pump radiation was focused into a gas chamber by a spherical mirror with F = 75 cm under aberration conditions (the angle of incidence of the radiation on the mirror was 15°). It is shown that there is optimal pump energy of 4.5 mJ and gas pressure of 3-4 atm. The spectral composition of the HDSC covers the range from 350 to 1000 nm. The divergence of HDSC radiation is diffraction-limited and its greatest value (the diameter of the white spot in the far zone) corresponds to a wavelength of 780 nm. The maximal HDSC energy was 17 μJ. The results are useful for understanding the physical mechanisms underlying the emergence of HDSC, as well as for developing broadband coherent radiation sources.
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