Research Of Spectral Broadening And Compression Based On Nonlinearity In Chalcogenide Waveguides

In recent years,silicon-based photonics has attracted great research interest because of its irreplaceable role in the development of all-optical communication networks.The nonlinearity of the silicon-based waveguide can be used to broaden or compress the spectrum,which provides a reliable method for obtaining mid-infrared supercontinuum and narrow linewidth sources.Currently,the schemes for generating supercontinuum and spectral compression in the optical fibers require longer fiber lengths and higher pump peak power,which are detrimental to the photonic integration and system stability.To study the nonlinear dynamics of supercontinuum generation and spectral compression in the mid-infrared region,several simple chalcogenide waveguides are designed in this paper.On the one hand,the conditions and influence factors on high-coherence and octave supercontinuum are deeply studied.On the other hand,two spectral compression schemes of the preset negative chirped pulse spectrum compression based on self-phase modulation effect and the spectral adiabatic compression scheme are implemented.The corresponding research work and innovations are as follows:1.The basic characteristics and research status of chalcogenide are described.The research status of mid-infrared supercontinuum and several schemes of spectrum compression are analyzed.2.The propagation equation of optical pulses in the nonlinear medium,which is also named the generalized nonlinear Schrodinger equation,is derived.Two general numerical solutions are given to solve the equation.The influence of nonlinear and dispersion effects is analyzed when the optical pulses propagate in the nonlinear media.3.To study the spectral broadening because of the nonlinearity in waveguides,a chalcogenide(As2Se3)waveguide with a ridge and suspended structure is designed and the relationship between the dispersion parameters and the waveguide structure parameters is studied.The optimal parameters of the waveguide are given by simulation.The effects of pump wavelength,peak power,pulse width and waveguide length on the mid-infrared supercontinuum generation are studied.The simulation results show that when the pump wavelength is 3.3 ?m,the peak power is 900 W,a pulse width is 100 fs and waveguide length is 0.87 mm,the generated supercontinuum has a spectral width ranging from 1.76 to 14.42 ?m at-40 dB,and it reaches to three octaves.The effects of different random noise levels on the coherence of supercontinuum are discussed further.Finally,we study the optical frequency comb generation based on supercontinuum.4.Two schemes for spectral compression using the nonlinearity in waveguides are studied.To realize the spectrum compression by using the preset negative chirped pulse based on the self-phase modulation effect,a As2S3 ridge waveguide is designed.When pumped at 2.05 ?m,the spectral compression ratio of 27.32 is achieved in the waveguide with a length of 6.6 mm.To realize spectral compression by spectral adiabatic compression,a As2S3 waveguide with a ridge and tapered structure is proposed and its dispersion parameter is increased exponentially with the change of the waveguide width.When pumped at 1.74 ?m,the spectral compression ratio of 3.62 is achieved in the waveguide with a length of 10 cm.In this paper,the good optical properties of chalcogenide waveguides in the mid-infrared region are used to study the nonlinear dynamics of high-coherence and octave supercontinuum generation and efficient spectral compression by simulation.The related research results are helpful to obtain on-chip mid-infrared broadband source and narrow linewidth source,thus actively promoting the research and development of silicon-based nonlinear photonics.