在无啁啾激光脉冲的非线性压缩过程中，基于级联倍频机制，对影响脉冲压缩的敏感因素——晶体位相失配量进行了理论分析和实验验证。当入射基频激光（即1ω光，波长为800 nm，脉宽为278 fs）进入I类二倍频β-BaB2O4(BBO)晶体后，随着晶体位相失配量的增加，基频光的输出脉宽先降后升，这种趋势可总结为“U”字形非线性变化；当位相失配量为40 mm-1时，脉宽缩至最小，此时脉宽压缩比最大。

Based on the cascaded frequency-harmonic mechanism during the course of nonlinear compression of nonchirped laser pulse, the sensitive factor affecting the pulse compression of crystal phase mismatch is analyzed theoretically and validated experimentally. After the input fundamental pulse (namely, 1ω, 0.8-μm wavelength and 278-fs pulse width) propagates through the type I second harmonic generation β-BaB2O4(BBO) crystal, the 1ω output pulse width is shortened firstly and widened again with the increase of crystal phase mismatch. This trend can be summarized as the “U” grapheme nonlinear change. The output pulse width is shortened to the least value and the highest compression ratio of pulse width is obtained when the crystal mismatch is 40 mm-1.