Abstract

Generation of soliton-like pulses in the depletion region of the pump pulse in the SRS process is one of the few phenomena which enable us to observe time evolution of quantum fluctuations.¹ As it was theoretically shown,^2,3 spontaneous phase fluctuations play a substantial role in initiation and development of the SRS process. Formed in linear regime of SRS random distribution of phases does not practically change, and in the deep nonlinear regime this phase picture is transferred to the distribution of the instantaneous intensity of laser and Stokes radiation. If the value of the relative phase of the laser, Stokes, and polarization waves Δϕ(t – z/c)= ϕ_S – ϕ_L – ϕ_q equal πn, then the SRS process does not develop. At high SRS efficiencies solitonlike spikes ("solitons") in the region of pump depletion (and "dark solitons" in the Stokes pulse accordingly) correspond to this phase value. Coincidence of temporal positions of solitons with the moments when the condition Δϕ = πn is satisfied allowed us to give indirect experimental confirmation of the existence of relative phase conservation in the SRS process.^4,5 For investigation of SRS process details, the most significant problem is direct phase measurements of interactive waves. In our case it is most convenient to observe the phase of the depleted pump wave, because we have referenced exciting laser wave with constant phase.

© 1994 IEEE