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首页> 外文会议>High-Power Laser Ablation VI pt.1 >Reflectivity oscillations of fs-laser excited Bismuth: Excitation of coherent phonons
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Reflectivity oscillations of fs-laser excited Bismuth: Excitation of coherent phonons

机译：fs-激光激发铋的反射振荡：相干声子的激发

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摘要

We present the experimental and theoretical studies of the optical response from the single-crystal of bismuth to the excitation by the femtosecond laser pulse. The experimental results revealed a complex, first - positive and a few picoseconds later - negative, change in time-dependent reflectivity, which could not be explained in the light of the existing theories. It is shown that reflectivity oscillations are related to the excitation of coherent phonons by the pulse with duration shorter of all relaxation times. We demonstrate that swiftly heated electrons are responsible for the phonon excitation due to the fast modification of the attractive (electronic) part of interatomic potential. The electronic perturbation of potential is also responsible for the red shift of phonon frequency and for the increase in the amplitude of phonons. The coherent phonon excitation process as well as the change in the reflectivity is related mainly to the modification of the electron-phonon momentum exchange frequency. The comparison between the theory and experiments shows an excellent agreement. Moreover, the reflectivity measurements allow direct recovery of the electron-phonon coupling rate in bismuth crystal, which has not been measured before.
机译：我们提出了从铋的单晶到飞秒激光脉冲激发的光学响应的​​实验和理论研究。实验结果表明，随时间变化的反射率首先会发生复杂的变化，首先是正的，然后是几皮秒，然后是负的，这无法根据现有理论进行解释。结果表明，反射率振荡与脉冲对相干声子的激发有关，持续时间短于所有弛豫时间。我们证明，由于原子间电势的吸引（电子）部分的快速修饰，迅速加热的电子引起了声子激发。电势的电子扰动还引起声子频率的红移和声子振幅的增加。相干声子激发过程以及反射率的变化主要与电子-声子动量交换频率的改变有关。理论与实验之间的比较显示出极好的一致性。而且，反射率测量允许直接恢复铋晶体中的电子-声子耦合速率，这是以前从未测量过的。

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