对折射率线性调制晶体中超短脉冲倍频特性进行了数值计算, 在泵浦衰减的情况下, 研究了转换效率和脉冲宽度随匹配带宽和晶体长度的变化.大信号时各频率成份在晶体不同位置的不平衡转换致使脉冲展宽, 且由于折射率的调制, 脉冲宽度和转换效率出现了周期性变化.同时, 分析了谐波脉冲啁啾随晶体长度和带宽的变化, 发现随着晶体长度的增大, 归一化最佳啁啾系数先增大后减小, 在长晶体时趋于1, 其极大值位置决定于本征带宽和调制带宽.讨论了相位失配量对转换效率和脉宽的影响, 结果表明失配因子y决定了中心频率的匹配位置, 当y=0时, 中心频率在晶体中心匹配, 这有利于提高转换效率并减小脉冲宽度.

Frequency-doubling in refractive-index-linear-modulating crystals was investigated numerically. In the case of depleted-pump, changes of conversion efficiency and pulse width with crystal length and band width of phase matching were studied. With the increase of pump pulses energy, pulses are broadened resulted from the unbalanced conversion of fundamental pulses at the different position of the crystal. Due to the modulation of refractive index, there are periodic oscillations in conversion efficiency and pulse width. Subsequently, by analyzing the chirp in harmonic waves, it was found that with the increase of crystal length, the normalized chirp coefficient increase first then decrease and finally tend to 1. The maximum of the normalized chirp coefficient is governed by modulated bandwidth and intrinsic bandwidth. Finally, the effects of phase mismatching parameter on conversion efficiency and pulse width was discussed and the results showed that phase mismatching parameter y determines the location of phasing matching of central frequency. When y=0 is considered, central frequency reaches phase matching at the middle of crystals where is beneficial to improve conversion efficiency and pulse quality.