The Faraday effect in potassium vapour pumped by nanosecond pulses of near resonant laser radiation is studied experimentally. The input radiation with linewidth 3 cm had a central frequency v = 13055 cm' which was 12 cm' higher than 4S1, -4P3, atomic transition frequency v0 = 13043 cm' The strong spectral broadening of pump radiation allowed to observe the Faraday rotation at frequencies V±l = V0 2.5 cm' located closer to the atomic resonance where the rotation was high. The decrease of Faraday rotation from 1 500 to 20° with the increase of the intensity of pump radiation from 2lO to 1O W/ciu2 has been measured. The saturation of 4S1, -4P3, transition is considered as a cause of suppression of Faraday rotation. The contributions of one photon resonance absorption, as well as of multiphoton processes, caused by more intense off resonant part of broadened pump radiation (having frequency detuning 12 cm'), to saturation of resonant transition is discussed . The experimental results are compared with theoretical calculations performed in [10].
The circularly distributed speckle pattern, as well as interference fringe structure in profile of the beam of stimulated Raman scattering (SRS) I Stokes component, pumped by multimode radiation with nearly four-fold azimuthal symmetry, have been observed. The SRS was excited near the threshold of generation by nanosecond pulses of laser radiation at wavelength 530 nm. The profile of output pump beam had a uniform intensity distribution, whereas the SRS beam profile showed kaleidoscopic change from shot to shot, while the energies of input pulses were kept stable. The interference fringes showed a number ofpoints where the fringes originated or vanished. Such behavior, which is the vortex signature, allows to suppose that SRS waves, generated from quantum noise, carry screw dislocations.
The beam profile of stimulated Raman scattering (SRS) in a Kerr medium (nitrobenzene) pumped by multimode radiation with regular structure having nearly four-fold azimuthal symmetry was studied. The SRS was excited near the threshold of generation by nanosecond pulses of laser radiation at wavelength 530 rim. The profile of output pump beam had a uniform intensity distribution, whereas the SRS beam profile showed kaleidoscopic change from shot to shot, while the energies of input pulses were kept stable. The circularly distributed speckle pauern, as well as interference fringe structure in the profile of the beam of SRS I Stokes component was observed. The interference fringes showed the number of points with origination and vanishing of fringes. Such behavior, which is the vortex signature, allows to suppose that SRS waves, generated from quantum noise, cany the screw dislocations. The origin of dislocations is analogous to one described for a speckle field 28 and discussed for SRS in
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