Research On Ultrashort Pulse Transmission Characteristics In Dispersion Decreasing Nonlinear Silicon Nitride Optical Waveguide

Ultrashort pulses have important applications in many fields such as optical information processing,high-speed optical communication systems,and optical imaging.Research on optical pulse compression and self-similar parabolic pulse generation based on fiber dispersion and nonlinear effects has been relatively mature.In recent years,nonlinear integrated optical waveguides have been developed based on silicon-based nonlinear integrated optical waveguides due to their large nonlinear coefficients and small volume,which facilitates the realization of integrated supercontinuum sources.However,silicon has a severe two-photon absorption effect in the 1550 nm band,which affects the nonlinear efficiency,while the two-photon absorption effect in the silicon nitride is weak and the waveguide loss is also small.In this paper,the transmission characteristics of ultrashort pulses in the dispersion-decreasing silicon nitride optical waveguide are studied.The optical pulse compression is realized by using the anomalous dispersion decreasing waveguide?and the self-similar parabolic pulse is generated by using the normal dispersion decreasing waveguide.The main research contents and innovations of this paper are as follows:1.The simulation design of multimode silicon nitride optical waveguide is carried out.Based on the waveguide fabrication process parameters5the dispersion characteristics of the TE fundamental mode of the multimode silicon nitride optical waveguide are designed for normal dispersion and anomalous dispersion control.2.According to the principle of self-similar soliton pulse compression,based on the simulated anomalous dispersion curve?the pulse compression is simulated and optimized.The better waveguide design parameters are determined by changing the pulse width and the waveguide transmission length,and the high-order dispersion effect on the pulse compression is studied.The pulse compression effect of the linear decreasing of the dispersion value and the decreasing of the parabola is studied.The 40cm long silicon nitride optical waveguide that can be realized by the fabrication process is discretized and segmented along the transmission distance,and the parameters such as dispersion and high-order dispersion of each segment are obtained,and pulse compression simulation is performed.3.According to the principle of self-similar parabolic pulse generation,the dispersion is gradually reduced to obtain the equivalent gain,and the self-similar parabolic pulse is generated based on the normal dispersion decreasing waveguide approximatively.The transmission characteristics of the hyperbolic secant pulse in the normal dispersion decreasing silicon nitride optical waveguide are studied,and the quasi-linear parabolic pulse generation is obtained.