The Study Of Relations Between Stimulated Brillouin Scattering And Stimulated Raman Scattering In Liquid Water

Recently, Stimulated Brillouin Scattering(SBS) and Stimulated RamanScattering(SRS) has become an important studies in nonlinear optics. StimulatedBrillouin Scattering and Stimulated Raman Scattering are two similar to the processof stimulated scattering. Stimulated Raman Scattering is a typical of stimulatedscattering, competing with stimulated Brillouin scattering for pumping laser energy,the result of competition correlates with The parameters of media and The nature ofthe incident laser spectroscopy. For liquid materials, if the laser pump source issingle longitudinal mode,the SBS will be the main scattering process because ofsignificant steady-state gain,but SRS will be greatly inhibited. However, recentstudies have shown that With the increase of laser energy,although SBS can be mainposition in liquid water, Backward stimulated Raman scattering(BSRS) began toincrease exponentially with the momentum,they are not only in comparison with eachother,but also there is symbiotic relationship between them.In this paper,we studiedthat attenuation coefficient and effective gain length in liquid water how to impact therelations between SBS and SRS.The laser line width is30GHZ and90MHZ without and with injection seededrespectively,the pulse energy of the laser is adjusted by changing the time delaybetween the oscillator and the amplifier.In the experiment,we chose5differentattenuation coefficient of water and effective gain length of0.8m,1.2m,1.6m,2.0m tomeasure;When the attenuation coefficient is same, to measure and analyze the energysignal of SBS and SRS which caused4different effective gain length in the watercell,respectively; When the effective gain length is same, to measure and analyzedifferent attenuation coefficient in the water cell,respectively. The results show thatbecause of the pulse compression effect, when the incident energy is high enough andwhen the effective gain length is relatively long, SBS can easy gain high-energy toform high peak power. Once the peak power more then the threshold of SRS or thethreshold of second-order SBS, SBS will serve as a new excitation source to exciteSRS or second-order SBS, to lead to consume part of energy of SBS, so when thelaser energy is high enough, the smaller the attenuation coefficient of water, the higher SBS output energy, at the same time the amplification of SRS became more fully; thelonger effective gain length, occurrence of SBS became more fully, more the laserenergy was used to excit SRS, the lower output energy of SBS.At the same time this paper studied the threshold relationship between salinity ofthe water and stimulated Brillouin scattering from theoretical and experimental. Theresults show that the curve of Attenuation coefficient of narrow-band mode happen toseparation when the incident energy increases to a certain value; That is, incident laserenergy of narrow-band mode increases to the stimulated Brillouin scattering threshold.And with the increase of salinity, the energy on the separation point of attenuationcoefficient under the narrow-band mode is larger, stimulated Brillouin scatteringthreshold is also larger clearly.