飞秒脉冲在硅波导中产生超连续谱的研究

Nonlinear propagation and supercontinuum generation of a femtosecond pulse in silicon waveguide

利用非线性薛定谔方程对飞秒脉冲在硅波导中的传输以及超连续谱的产生进行了研究,计算和分析了色散参量及非线性损耗在超连续谱的产生过程中的影响.结果表明,孤子分裂是飞秒脉冲在硅波导中产生超连续谱的主要机理.飞秒脉冲中心波长与波导零色散点的相对位置对超连续谱的产生有极大影响.当中心波长位于近零色散点的反常色散区时,孤子分裂现象最明显,谱宽远大于在零色散波长及正常色散处入射时的情况,并且达到稳定展宽所需波导长度最短.其次,高阶色散的大小也会影响光谱展宽,三阶色散绝对值较小时,能够获得较大的展宽.另外,由于双光子吸收效应带来大量损耗,限制了谱宽,并且随着初始脉冲功率的逐渐增大,展宽出现饱和现象.

Propagation of femtosecond pulse and supercontinuum generation in silicon waveguide are investigated numerically by solving the generalized nonlinear Schrdinger equation.The effects of dispersive effect and nonlinear loss on supercontinuum generation are simulated and analyzed.It is found that soliton fission is the main mechanism of supercontinuum generation in silicon waveguide.The relative position between the central wavelength of femtosecond pulse and zero-dispersive wavelength（ZDW） of silicon waveguide significantly affects the generation of supercontinuum.When the input pulse falls in the anomalous dispersion regime,soliton fission phenomenon is most obvious.It is also found that the high-order dispersion plays an important role in supercontinuum generation.When the absolute value of third-order dispersion is smaller,a broader supercontinuum can be obtained.Besides,two-photon absorption（TPA） effect in silicon induces high loss,and reduces the spectral width of the supercontinuum.