铋纳米薄膜相干光学声子研究  

Study of Coherent Optical Phonon in Bismuth Nanofilms

作　　者：王建立[1,2] 郭亮 罗哲 徐先凡 倪中华[1] 陈云飞[1] 

机构地区：[1]东南大学机械工程学院江苏省微纳生物医疗器械重点实验室,南京211189 [2]SCHOOL OF MECHANICAL ENGINEERING,PURDUE UNIVERSITY,WEST LAFAYETTE,INDIANA

出　　处：《工程热物理学报》2015年第4期865-869,共5页Journal of Engineering Thermophysics

基　　金：国家973计划(No.2011CB707605);国家自然科学基金资助项目(No.51106029,No.51476033)

摘　　要：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。The coherent optical phonon of bismuth nanofilms is measured by using the ultrafast collinear two color time-resolved pump-probe experiment.The pulse width of the probe beam is obtained to be about 45 fs by using the auto-correlation technique.After the manipulation of the Pulse Shaper,the pulse width of the pump beam of about 250 fs is characterized by the cross-correlation technique.Finally,the symmetric vibration mode(A_(1g)) with a frequency of 2.86 THz is determined,which agrees well with the result that observed by using the spontaneous Raman scattering(Raman Spectroscopy).Considering the effect of convolution between the cross-correlation signal and the exponential decay function,the differential reflectivity within 10 ps is fitted,the characteristic decay time of the coherent optical phonon is determined to be about 2.6 ps,which is comparable to the decay time of electronic cooling component but much smaller than the rise time of the lattice heating process.Therefore,the ultrafast time-resolved pump-probe experiment offers a convenient way to clarify the different carrier-phonon scattering processes at distinctive time constant.

关 键 词：超快激光 相干光学声子 脉冲整形 对称振动模 互相关测量 

分 类 号：TB302[一般工业技术—材料科学与工程] TB383.2