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;
1991-01-01
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
