Vol. 30, issue 03, article # 2

Ivanov N. G., Losev V. F. Kerr nonlinearity effect on femtosecond radiation pulse filamentation in air. // Optika Atmosfery i Okeana. 2017. V. 30. No. 03. P. 198–203. DOI: 10.15372/AOO20170302 [in Russian].
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Abstract:

The filamentation conditions of a femtosecond laser pulse by its focusing in air are investigated experimentally and theoretically. A good agreement is observed between experimental and calculated data when neglecting the filament plasma. It is shown that at low numerical aperture (NA ≤ 2.15 × 10–3), a Kerr nonlinearity plays a fundamental role in the formation, existence, and termination of a filament. At the initial stage, the Kerr effect leads to the beam self-focusing and emergence of the filament; at the final stage, to radiation defocusing and sharp decrease in its axial intensity due to the beam wave front distortions. In the case of aberration focusing, a spatial quasi-soliton is formed after a visible filament due to the balance between Kerr self-focusing and diffraction extending. The quasisoliton is a source of the directional white supercontinuum.

Keywords:

Kerr nonlinearity, filamentation, focusing, supercontinuum

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