Fast Light Based On Forward Stimulated Brillouin Scattering In Photonic Crystal Fiber

In recent years,with the increasing development of optical fiber communication technology,the speed of the information process and transmission need to further improve.Fast or slow light technology is the most possible technology to deal with signal synchronization and buffering in all-optical communication networks.The stimulated Brillouin scattering effect in the optical fiber can be utilized to realize fast and slow light which has the advantages,such as operating at room temperature,adjustable operating wavelength,and being compatibility with the recent optical fiber communication systems and so on.In the past decades,the backward stimulated Brillouin scattering has been extensively studied and the applications has been implemented.With the evolution of photonic crystal fibers,the forward stimulated Brillouin scattering has attracted more and more attention for last years.The Brillouin frequency shift can reach up to GHz range in photonic crystal fibers,the optical waves and the transverse acoustic waves are tightly confined and interacted in small-core optical fibers,which effectively enhances the interaction between optical wave and the sound waveIn this paper,the distributions of optical field fundamental mode and acoustic field fundamental mode are numerically simulated based on the three-wave coupling equations of the forward stimulated Brillouin scattering,and the effective refractive index,the Brillouin frequency shift and the acoustic-optic coupling integral are calculated by using the finite element method.The influences of pump light power,transmission distance and initial pulse width on the time advancement are studied.The results show that the time advancement is more sensitive to the pump power than to the transmission distance.When the pulse line width is less than the Brillouin line width,the pulse is compressed obviously.For the same initial pulse width,the signal pulse is compressed greatly as the pump power increasesThe PCF doped with different concentrations of GeO2 in the substrate materials is proposed,the influences of the doping concentration on the Brillouin frequency shift of the forward stimulated Brillouin scattering,the transverse distribution of the acoustic and optical fields,interaction between the acoustic and optical fields,strain energy density of acoustic field and Brillouin line width are investigated.The Brillouin frequencies of the four acoustic fields(named L1,L2,L3 and L4)are 1.5919GHz,1.6559GHz,1.7446GHz and 1.9647GHz respectively.With the increase of the doping concentration,the Brillouin frequency shift and the Brillouin line width decrease,but the interaction between the acoustic field and the optical field is still the strongest.For a given the doping concentration,the Brillouin frequency shift rises,but the intensity of the acoustic field and the forward stimulated Brillouin scattering gradually drops with the increase of the order of the acoustic field modes.The variation of doping concentration can change the sequence of occurrence of different acoustic modes.The influence of temperature and strain on Brillouin frequency shift is also simulated and the results indicate that with the temperature increases,the Brillouin frequency shift of acoustic mode L1 increases,but those of the other three acoustic modes decreases.The increase of strain intensity leads to the increase of Brillouin frequency shift of the four acoustic modes.