超短脉冲通过厚衬底多层结构传输的回波光谱畸变的消除
Removal of spectral distortion due to echo for ultrashort pulses propagating through multilayer structures with thick substrate
摘要：
鉴于时域光谱，特别是THz时域光谱的广泛应用，通常需要对通过多层结构传播的探测脉冲进行建模。由于多层膜通常生长在比其他层厚得多的衬底上，探测脉冲的传输包括由衬底界面处的多次反射引起的一系列回波脉冲。实验通常只从第一个发射脉冲测量时间轮廓并构造发射光谱。由于典型的衬底导致与光谱带宽相当的交叉时间的事实，第一透射脉冲的光谱和全透射光谱可以是显著不同的。因此，重要的是在理论上对没有回波的传输进行建模，以便能够直接与实验结果进行比较。在这里，我们提出了一种方法来优雅和容易地从理论上消除透射光谱的回波，而无需傅立叶变换信号两次。没有回波的发射脉冲的频谱将在没有额外的数值步骤的情况下解析地产生，从而在处理大规模计算时减少计算时间和程序复杂性。
英文摘要：
Given the wide range of applications of time-domain spectroscopy, and particularly THz time-domain spectroscopy, the modelling of a probe pulse propagating through a multilayered structure is often required. Due to the fact that the multilayers are usually grown on a substrate much thicker than the other layers, the transmission of a probe pulse includes a series of echo pulses caused by the multiple reflections at the substrate interfaces. Experiments often measure the time profile and construct the transmitted spectrum only from the first transmitted pulse. Due to the fact that typical substrates lead to times of crossing comparable to the spectral bandwidth, the first transmitted pulse's spectrum and the full transmitted spectrum can be importantly different. It is therefore important to theoretically model the transmission without the echo, to be able to directly compare with experimental results. Here we propose a method to elegantly and easily theoretically remove the echo from the transmission spectrum, without Fourier transforming the signal twice. The spectrum of the transmitted pulse without echo will be produced analytically without additional numerical steps, reducing computational time and program complexity when dealing with larger scale computing.
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