Self-phase modulation (SPM) in filamentary plasma can explain anomalous large frequency shifts in time-resolved spectra of laser light backscattered from laser plasmas. We have modelled the effect of SPM by assuming a rapid variation in the plasma electron density. This is expected when laser light filaments or self-focuses in plasmas. The first direct experimental observation is presented showing the correlation between laser beam self-focusing and anomalous backscattered stimulated Brillouin (B-SBS) spectra. The B-SBS spectral features recorded are strongly characteristic of those expected when the frequency of the incident laser light is modified by SPM. A consequence of our observation is that SPM should be considered in the interpretation of SBS spectra in laser-plasma interactions where laser self-focusing is occurring. Also, SPM can contribute to the saturation of the SBS process to low levels by effectively destroying the coherence of the SBS interaction.

THE EFFECT OF SELF-PHASE MODULATION ON STIMULATED BRILLOUIN-SCATTERING IN FILAMENTARY LASER PLASMAS

GIULIETTI, DANILO;
1991

Abstract

Self-phase modulation (SPM) in filamentary plasma can explain anomalous large frequency shifts in time-resolved spectra of laser light backscattered from laser plasmas. We have modelled the effect of SPM by assuming a rapid variation in the plasma electron density. This is expected when laser light filaments or self-focuses in plasmas. The first direct experimental observation is presented showing the correlation between laser beam self-focusing and anomalous backscattered stimulated Brillouin (B-SBS) spectra. The B-SBS spectral features recorded are strongly characteristic of those expected when the frequency of the incident laser light is modified by SPM. A consequence of our observation is that SPM should be considered in the interpretation of SBS spectra in laser-plasma interactions where laser self-focusing is occurring. Also, SPM can contribute to the saturation of the SBS process to low levels by effectively destroying the coherence of the SBS interaction.
Afsharrad, T; Coe, S; Giulietti, A; Giulietti, Danilo; Willi, O.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/18743
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