Roussel Eléonore, Szwaj Christophe, Evain Clément, Steffen Bernd, Gerth Christopher, Jalali Bahram, Bielawski Serge
Univ. Lille, CNRS, UMR 8523 - PhLAM - Physique des Lasers, Atomes et Molécules, Centre d'Étude Recherches et Applications (CERLA), F-59000, Lille, France.
DESY (Deutsches Elektronen-Synchrotron), Notkestr. 85, D-22607, Hamburg, Germany.
Light Sci Appl. 2022 Jan 10;11(1):14. doi: 10.1038/s41377-021-00696-2.
Recording electric field evolution in single-shot with THz bandwidth is needed in science including spectroscopy, plasmas, biology, chemistry, Free-Electron Lasers, accelerators, and material inspection. However, the potential application range depends on the possibility to achieve sub-picosecond resolution over a long time window, which is a largely open problem for single-shot techniques. To solve this problem, we present a new conceptual approach for the so-called spectral decoding technique, where a chirped laser pulse interacts with a THz signal in a Pockels crystal, and is analyzed using a grating optical spectrum analyzer. By borrowing mathematical concepts from photonic time stretch theory and radio-frequency communication, we deduce a novel dual-output electro-optic sampling system, for which the input THz signal can be numerically retrieved-with unprecedented resolution-using the so-called phase diversity technique. We show numerically and experimentally that this approach enables the recording of THz waveforms in single-shot over much longer durations and/or higher bandwidth than previous spectral decoding techniques. We present and test the proposed DEOS (Diversity Electro-Optic Sampling) design for recording 1.5 THz bandwidth THz pulses, over 20 ps duration, in single-shot. Then we demonstrate the potential of DEOS in accelerator physics by recording, in two successive shots, the shape of 200 fs RMS relativistic electron bunches at European X-FEL, over 10 ps recording windows. The designs presented here can be used directly for accelerator diagnostics, characterization of THz sources, and single-shot Time-Domain Spectroscopy.
在包括光谱学、等离子体、生物学、化学、自由电子激光、加速器和材料检测等科学领域，需要以太赫兹带宽单次记录电场演变。然而，潜在的应用范围取决于在长时间窗口内实现亚皮秒分辨率的可能性，这对于单次技术来说在很大程度上仍是一个未解决的问题。为了解决这个问题，我们提出了一种针对所谓光谱解码技术的新的概念方法，其中啁啾激光脉冲与普克尔盒晶体中的太赫兹信号相互作用，并使用光栅光谱分析仪进行分析。通过借鉴光子时间拉伸理论和射频通信中的数学概念，我们推导出一种新颖的双输出电光采样系统，利用所谓的相位分集技术，可以以前所未有的分辨率对输入的太赫兹信号进行数值重建。我们通过数值模拟和实验表明，与以前的光谱解码技术相比，这种方法能够单次记录持续时间长得多和/或带宽更高的太赫兹波形。我们展示并测试了所提出的用于单次记录持续时间超过20 ps、带宽为1.5太赫兹的太赫兹脉冲的分集电光采样（DEOS）设计。然后，我们通过在欧洲X射线自由电子激光装置上连续两次记录，在10 ps记录窗口内记录200 fs均方根相对论电子束团的形状，展示了DEOS在加速器物理中的潜力。这里提出的设计可直接用于加速器诊断、太赫兹源的表征以及单次时域光谱分析。
