Photoexcited GaAs surfaces studied by transient terahertz time-domain spectroscopy.
Photoexcited GaAs surfaces studied by transient terahertz time-domain spectroscopy.
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DOI：
10.1364/ol.25.000013
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发表时间：
2000
期刊：
影响因子：
3.6
通讯作者：
M. Schall;P. U. Jepsen
中科院分区：
文献类型：
--
作者：
M. Schall;P. U. Jepsen
空气-GaAs界面的传输特性和瞬态吸收和折射率光谱的薄，光激发表面层的研究随后由飞秒激光脉冲激发。我们发现太赫兹（THz）探测脉冲的总相位变化和传输受界面效应的影响。这一观测结果在解释吸收介质的THz时域光谱数据方面具有重要意义。我们还观察到，太赫兹脉冲显然到达探测器多达60 fs之前，当它是通过光激发GaAs晶片传输。这种效果是充分解释的频率相关的传输和相移在空气GaAs界面，是不相关的超光速传播。
The transmission characteristics of an air-GaAs interface and the transient absorption and index spectra of the thin, photoexcited surface layer are investigated subsequent to excitation by a femtosecond laser pulse. We find that the total phase change and transmission of a terahertz (THz) probe pulse are dominated by interface effects. This observation has important implications in the interpretation of THz time-domain spectroscopy data of absorbing media. We also observe that the THz pulse apparently arrives at the detector as much as 60 fs earlier when it is transmitted through an optically excited GaAs wafer. This effect is fully explained in terms of a frequency-dependent transmission and phase shift at the air-GaAs interface and is not associated with superluminal propagation.