Besides the conventional single-pulse train generation,the Ti:sapphire laser system sometimes produces two or even more pulses should proper conditions be satisfied.By treating the pulse propagation within the laser gain medium with the help of split-step Fourier method,independently taking into account of the dispersion originating from the prism sequence,and making use of a generalized pulsewidth formula,the double-pulse formation process is numerically simulated in a self-consistent scheme.It is revealed that the condition of a tiny net negative dispersion with strong chirp is mandatory.The double-pulse generation manifests itself in a narrow range of physical parameters,thereby pose it as a metastable state.%在自锁模钛宝石激光器中,除可形成传统的单脉冲外,在适当的条件下,还可产生双脉冲.本文运用广义脉宽公式单独计及棱镜系统的色散,用分步富氏法数值求解非线性薛定谔方程,在脉宽自洽的判据下,模拟了双脉冲的形成过程.结果表明,小量的净负色散配合强的啁啾是形成光谱调制的条件.双脉冲只产生在有限的参数范围内且极易被破坏.
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