本文通过飞秒脉冲激光和铁铂异质结构的相互作用产生太赫兹(Terahertz,THz)脉冲,并利用时序太赫兹的测量方法,研究了太赫兹光在金属薄膜中的传播规律.太赫兹光在铁(Fe)膜和铂(Pt)膜中都以指数形式衰减,但是与金属体材料传播介质及适用于体材料的Drude模型相比,2～10 nm厚的铁、铂薄膜对太赫兹光的衰减系数明显增加.其原因可能是由于超薄薄膜中电子在膜厚方向的运动受限,而膜平面内的自由程增加,导致在膜平面内电场的衰减长度变小.该现象在近红外的飞秒脉冲光中同样存在.%This paper investigates the transmission of terahertz pulse in the ultrathin film with terahertz time-domain spectroscopy and the terahertz pulse produced by the interaction between femtosecond laser pulse and Fe/Pt heterostructure.The thickness of the Fe/Pt film ranges from 2 nm to 8 nm.The terahertz wave exponentially decays in Fe and Pt ultrathin films,but it decays much faster in the bulk Fe and Pt.Due to the limitation in the thickness,electrons have much longer free path in the film plane,which increases the conductivity in the film plane.We also find that the laser pulse with 800 nm wavelength also decays faster in the ultrathin film.
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