Research On The Soliton Trapping Of Dispersive Wave In Photonic Crystal Fibers

The rise of photonic crystal fiber(PCF)has opened new horizons for effectively supercontinuum(SC)generation mainly because of their“endlessly single-mode”behavior,controllable group velocity dispersion characteristics and high nonlinear properties.The generation of dispersive wave is the one of the main physical mechanism of SC generation.Dispersive wave(DW)is emitted due to the energy transfer from soliton to narrow-band resonance in the normal dispersion regime,which is a complex nonlinear process.In recent years,DW has a wide application in the practical engineering and scientific research.Based on the numerical study,our paper shows that the time-frequency characteristic of DW and the soliton trapping of DW.The main research contents are listed below:Firstly,based on the nonlinear Schrodinger equation,we studied DW generation and its influence factors in PCF by the standard split-step Fourier method.Because of the complexity of DW generation by the theoretical analysis,the generation and influential factors of dispersive wave in photonic crystal fiber are analyzed by the numerical simulation.In order to clearly display the evolution of soliton trapping of dispersive waves,the spectrogram of output pulses is observed using cross-correlation frequency-resolved optical gating technique(XFROG).Secondly,we numerical studied the main influence factors of high-order soliton propagate in PCF and the DW generation under different dispersion slope.The simulation results show that the generation and amplification of DW is the main physical mechanism of SC generation.For the positive dispersion slope,the generated blue-shifted DW(B-DW)is at the blue side of output spectrum,the B-DW is emitted at the trailing edge of the red-shift soliton in the time domain whereas the DW will be generated at the red side of output spectrum and at the leadling edge of the red-shift soliton if the dispersion slope is negative.When the pump wavelength is near the low zero dispersion wavelength(ZDW)of PCF with ZDW,the B-DW and red-shifted DW(R-DW)can be observed at the same time.Thirdly,we present a comparison of trapping of DW by solitons during femtosecond pumped supercontinuum generation in photonic crystal fiber with single or double zero dispersive wavelength.Numerical simulation results show that the generated supercontinuum in photonic crystal fiber with two zero dispersive wavelengths includes both blue-shifted dispersive wave(B-DW)and red-shifted dispersive wave(R-DW)while the generated supercontinuum in photonic crystal fiber with single zero dispersive wavelength has only blue-shifted dispersive wave.We find a novel phenomenon that not only B-DW but also R-DW can be trapped by solitions via four-wave mixing when the group-velocity matching between the soliton and the dispersive wave is satisfied,thus leading to the generation of new spectral components.Increasing the pump power can make the trapping phenomenon more obvious,which can help us to get more wide and smooth continuous spectrum.