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The pair correlations between the instantaneous intensities of input pump superbroadband (250 cm1) laser radiation with femtosecond and picosecond noise structures, output depleted pump radiation and Stokes one generated through stimulated Raman scattering in compressed hydrogen have been experimentally studied under the weak and strong pump depletion by means of time-delayed four-wave nüxing in Kerr-shutter configuration. Experimental results show that the Stokes radiation is well correlated with the input pump one up to the energy conversion efficiency of about 30 %. Considerable suppression of the femtosecond amplitude fluctuations in the depleted pump beam has been observed upon increasing the pump depletion that indicates the possible way for preparing superbroadband light with predominant phase fluctuations using SRS. The picosecond part of cross-correlation function between the depleted pump and Stokes radiation flows has very asymmetric shape that is probably caused by the transiency in the scattering of picosecond noise spikes and by the fact that these spikes in Stokes and depleted pump radiation flows have opposite temporal shapes. INTRODUCTIONThe studies of the statistical properties of radiation flows involved in the process of stimulated Raman scattering (SRS) is of great interest for nonlinear optics from the different points of view' . In particular, SRS is a convenient nonlinear process for producing frequency-shifted superbroadband Stokes radiation which is well correlated with the pumping one2 . Such radiation flows can be widely used in the transient crosscorrelation spectroscopy with incoherent 1ight810 and for the other .In this report we present the results of experimental studies of temporal pair correlations between the intensities of superbroad-bandwidth input laser pump, depleted pump and Stokes beams involved in the process of SRS in compressed hydrogen. Input pump radiation had two noise structures in the dependence of the instantaneous intensity on time -one noise structure with femtosecond correlation time and the other with picosecond correlation time. We have studied and compared the transformation of noise properties through SRS in these time scales under the different levels of pump depletion from weak to strong one when pump to Stokes energy conversion efficiency varied from 3 % up to about 30 %. EXPERiMENTAL STUDIES OF CORRELATIONSThe scheme of the studies is shown in Fig. 1. A broadband Rhodamine 6G dye-laser (3) pumped by the second harmonic (SH) pulses of nanosecond YAG:Nd-laser (1) with nonselective resonator was used for generating the 6 ns (full width at half maximum or FWHM) pulses with a spectral bandwidth of about 250 cm1 (FWHM) and energy of about 15 mJ in maximum. The 8-shaped cavity of the dye laser without any spectral selecting elements consisted of three highly reflective mirrors and the output one with reflection coefficient of 10%. Such a scheme of the laser allowed to realize the conditions near to superluminescent lasing with multiple passing the inultimode ...

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