超短脉冲在单块晶体中的三次谐波理论模拟

Study on Third-Harmonic Generation of Ultra-short Pulse in Single Crystal

讨论了群速度失配、自相位调制和交叉相位调制、晶体厚度、基波的频率啁啾等因素对超短脉冲单块晶体的三次谐波转换效率、三倍频光脉冲形状以及频谱的影响.结果表明:群速度延迟使三倍频光脉冲展宽;自相位调制和交叉相位调制会降低转换效率,并使三倍频光脉冲形状发生畸变;晶体厚度对三倍频光脉冲频谱展宽有着较大的影响;合适的基频光频率啁啾可以减小三倍频光脉冲的畸变,并有效地提高三倍频转换效率.

The effects of group-velocity mismatch,self-and cross-phase modulation,the thickness of crystal,and the chirp of fundamental field on the conversion efficiency,pulse shape and spectrum of third-harmonic field were discussed.The results show that group-velocity mismatch broadens the width of third-harmonic pulse.Self-and cross-phase modulation not only reduces the tripling efficiency,but also distorts the shape of third-harmonic pulse.The thickness of crystal has effect on the spectrum distribution of third-harmonic field.Furthermore,the suitable chirp of fundamental field can reduce the distortion of third-harmonic pulse and increase the third-harmonic conversion efficiency.