Impact Of Potential Barriers On Soliton Spectral Tunneling In Photonic Crystal Fiber

Since the light pulse in the optical fiber has a very low transmission loss,it is used as the medium for information transmission over long distances.However,traditional fiber has its limitations.Recently,the appearance of photonic crystal fiber(PCF)has broken these limitations,opening a new door for scientific research,and its dispersion controllability and high nonlinearity bring unlimited possibilities for the development of nonlinear optics.By changing its materials and internal structure,we can adjust its dispersion parameters,the number of zero dispersion wavelengths(ZDWs)to obtain the required fiber for scientific research.For example,the typical fluoride fiber greatly broadens the spectrum of the supercontinuum in the fiber by doping.We can also use the flexibility of its structure to obtain PCF with multiple ZDWs,which can be used for the study of soliton spectral tunneling(SST)effects.The launched soliton in the anomalous group velocity dispersion(GVD)regime experiences red shift by reason of Raman-induced frequency shift(RIFS),and the energy of the launched soliton tunnels through the potential barrier in the form of red-shifted dispersive wave(R-DW)and appears in the next anomalous GVD regime in the form of soliton.This is so-called SST effect.In this paper,numerical analysis is used to explore the effects of the potential barrier in the PCF on the energy distribution,variation and tunneling soliton in the SST effect.PCFs with three ZDWs are used as the transmission medium,and the chief studies are listed below:First,on the basis of the generalized nonlinear Schr?dinger equation of optical pulse propagation in the fiber,the split-step Fourier method in the numerical analysis method can be used to better analyze the generation of the dispersive wave(DW)during the optical pulse transmission.In addition,by using the cross-correlation frequencyresolved optical gating(X-FROG)technique,one can explore the time-frequency characteristics of the optical pulse transmission process.In addition,the energy distribution and transference of DWs and solitons in the SST effect can be well analyzed.Secondly,based on the data of numerical simulation,the energy distribution and variation of each spectral component(soliton,blue-shifted dispersive wave(B-DW),R-DW,etc.)during the SST are analyzed.The results show that during the SST,the RDW acts as the channel of energy for the SST,and transfers the energy from the launched soliton to the switched soliton.Under the premise that the soliton can tunnel through the potential barrier,that the wider the potential barrier,the slower the increase rate of the energy ratio of the switched soliton,while the width does not affect the final energy ratio of switched soliton—in other words,the conversion rate in the process of SST.Thirdly,the differences of SST in the fibers with different potential barriers are analyzed and compared.When the potential barrier meets with the premise of SST,the energy of the launched soliton tunnels through the normal GVD regime in the form of the R-DW and forms as the switched soliton in the next anomalous GVD regime.When the potential barrier gradually widens and doesn't meets with the premise of SST,most of the energy of the launched soliton remains in the normal GVD regime in the form of R-DW,only a small portion of the energy tunnels through the normal GVD regime and forms as a leakage DW.It exists for a period of time and dissipates during the propagation process;when the barrier is too wide,the launched soliton can't tunnel through the normal GVD regime,and its energy remains in the normal GVD regime in the form of a R-DW.The result indicates that when the potential barrier is reasonably adjusted,the process of SST and the spectrum range where the soliton appears can be well controlled.In this way,the spectrum range and energy intensity of the supercontinuum can be well regulated.At the same time,it also has high value in the application of communication security.