We report steady-state self-focusing, self-trapping, and self-defocusing of a cw dye laser beam in sodium vapor for frequencies within several Doppler widths of the

D

-line resonance transitions. We measured the variation of the beam profile as the light propagates through the vapor. We observed a 20-mW beam self-trapped in a 12-cm-long filament having a half-power diameter of 70 \ensuremath{\mu}m.

DOI: 10.1103/physrevlett.32.129

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Strong amplification of sidebands in self-focused laser beams in an atomic vapor

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Summary form only given. The interaction between an intense pump beam and a weak probe beam in an atomic vapor has been the subject of numerous investigations. Besides the well-known features in the frequency spectrum of the light, interesting spatial phenomena are observed. They are due to the inhomogeneous intensity distribution of a laser beam, coupled to propagation, and range from self-focusing or defocusing effects to the generation of localized distributions of light that propagate self-similarly (bright or dark solitons). We investigate the reshaping of a probe beam due to the interaction with a pump in sodium vapor, a problem that is important in many different contexts.Summary form only given. The interaction between an intense pump beam and a weak probe beam in an atomic vapor has been the subject of numerous investigations. Besides the well-known features in the frequency spectrum of the light, interesting spatial phenomena are observed. They are due to the inhomogeneous intensity distribution of a laser beam, coupled to propagation, and range from self-focusing or defocusing effects to the generation of localized distributions of light that propagate self-similarly (bright or dark solitons). We investigate the reshaping of a probe beam due to the interaction with a pump in sodium vapor, a problem that is important in many different contexts.

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We report steady-state self-focusing, self-trapping, and self-defocusing of a cw dye laser beam in sodium vapor for frequencies within several Doppler widths of the

D

We report steady-state self-focusing, self-trapping, and self-defocusing of a cw dye laser beam in sodium vapor for frequencies within several Doppler widths of the

D

A cw dye-laser beam tuned to the high-frequency wing of the Na

{D}_{2}

line (at 2-6 GHz from the center of the

{D}_{2}

line) is focused into a Na vapor, forming a self-focused laser filament. The incident laser beam, which is mainly single frequency, contains very weak sidebands at about \ifmmode\pm\else\textpm\fi{} 1 GHz from the main frequency and of intensity \ensuremath{\sim} ${10}^{\ensuremath{-}3}$ of the main frequency. Such sidebands are found to be strongly amplified by the vapor. Amplification factors in excess of 100 have been observed at suitable Na density, laser power, and detuning. Such strong sideband amplification, previously unknown, is explained as an off-resonant stimulated Raman scattering process.