利用共轴双色飞秒激光泵浦-探测技术测量了铋(Bi)纳米薄膜的相干光学声子。采用自相关技术测量得到探测光的脉宽约为45 fs,用探测光和泵浦光的互相关信号得到泵浦光经过脉冲整形以后的脉宽约为250 fs,进而测量得到Bi纳米薄膜的对称振动模频率为2.86 THz,与自发Raman光谱的结果吻合。采用指数衰减函数与互相关信号的卷积拟合延迟时间在10 ps以内的差分反射信号,确定了相干光学声子振幅衰减的特征时间约为2.6 ps,与电子衰减特征时间相近,却远小于晶格加热的特征时间,从而为进一步揭示材料内部载流子与声子的相互作用提供了依据。 Coaxial photonic femtosecond laser pump - detection technique was used to measure the coherent optical phonons of bismuth (Bi) nanocrystalline films. The pulse width of the probe light measured by autocorrelation is about 45 fs. The pulse width of the pump light after pulse shaping is about 250 fs with the cross-correlation signal of the probe light and the pump light, and then the Bi nanometer thin film The symmetric vibrational mode frequency is 2.86 THz, which is consistent with the results of spontaneous Raman spectroscopy. Convolution of exponential decay function and cross-correlation signal is used to fit the differential reflection signal with delay less than 10 ps. The characteristic time of amplitude attenuation of coherent optical phonon is determined to be about 2.6 ps, which is close to the electronic attenuation characteristic time but much smaller than The characteristic time of lattice heating provides the basis for further revealing the interaction of carriers and phonons in the material.