中文摘要：

以飞秒振荡器作为激发光源，使用单色泵浦－探测技术观测Bi薄膜的超快动力学和相干声子振荡。在不同泵浦能量（0.28～4.57 mJ／cm2）下，可以观测到明显的相干声子振荡现象，这主要是由A1g模式的振动引的。在考虑啁啾系数的条件下使用经典阻尼振荡函数对测试结果进行拟合。实验和理论拟合结果显示，随着泵浦能量的增加，其振荡强度明显增强，经过快速傅里叶变换后， A1g模式的频率值从2.98 THz变化到2.92 THz，明显不对称，啁啾常数发生变化， A1g模式有软化趋势，这与低频高能脉冲激发下得出的结论一致。

英文摘要：

We measured coherent optical phonon dynamics in a thin bismuth film through one-color pump-probe reflection experiment with femtosecond oscillator as excitation laser source .The obvious coherent phonon can be observed due to the damped harmonic oscillation of A 1g mode as a function of pump fluence from 0.28~4.57 mJ/cm2 .The experimental and theoretical results reveals the amplitude of coherent phonon is enhanced with the pump fluence increased under the condition of chirp coefficient considered .After the fast Fourier transformation , the frequency of A1g mode is asymmetrical and changed from 2.98 to 2.92 THz when the pump fluence is increased . The soften of A1g mode can be derived with the consistence of low-repetition rate femtosecond laser source .