Propagation Characteristics Of Parallel Dark Solitons And The Spectral Evolution Of Bright Soliton In Silicon-on-insulator Waveguide

Silicon-on-insulator(SOI)waveguides are the main media used for silicon photonics research.Because of the refractive index mismatch in the SOI waveguide core layer,light can be restricted to a small core layer,resulting in strong nonlinear optical effect,which enables us to realize a variety of optical functions in a very short length.It is expected that optical integrated chips will replace traditional chips and improve operational efficiency.Dark soliton pulses are stable and highly resistant to noise and losses in waveguides.Dark solitons have smaller amplitude attenuation rate,pulse width growth rate,and exhibit high code rate and good self-recovery.There is little discussion on the effect of dark solitons in silicon based optical waveguides.But in the time domain,dark solitons are likely to be generated when bright solitons are transmitted,and the dark solitons have an obvious influence on their transmission characteristics,and the spectral evolution in the frequency domain will also undergo a great change.In this paper,two parallel dark solitons’ transmission characteristics and the spectral morphology of the bright soliton accompanied by dark solitons are simulated by using the coupled wave equation established in the Silicon-on-insulator waveguides using the split-step Fourier method.The simulation analysis shows that the delay difference will deform the parallel dark soliton pulse,forming a bright-like soliton in the transmission process and reducing the transmission quality.By increasing the power of one dark soliton,the energy of the other dark soliton can be increased,and the larger the increase of energy,the greater the increase of the other dark soliton.When the initial chirp is introduced into one of the dark solitons,it is found that chirp will aggravate energy consumption,positive chirp will intensify pulse broadening,negative chirp will slow down pulse broadening,and it has obvious compression effect on the other dark solitons.Negative chirp of dark solitons should not be too large,too large negative chirp will have a strong impact on itself and parallel dark solitons.To explore the influence of dark soliton on light soliton spectrum,the power and input chirp of dark soliton and the second-order dispersion are changed to influence the self-phase modulation,soliton splitting and dispersion wave radiation of bright solitons.The simulation shows that the dark soliton will change the spectral shape of the bright soliton.If the power of dark solitons is changed,the splitting effect of bright soliton will be affected.The chirped dark soliton can improve the spectral width and flatness.Changing the dark soliton’s dispersion will affect the phase matching of the bright soliton,affect the dispersion wave radiation,and therefore affect the spectrum evolution.