Department of Engineering, University of Cambridge , 9 JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom.
Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford, OX1 3PU, United Kingdom.
Nano Lett. 2017 Apr 12;17(4):2603-2610. doi: 10.1021/acs.nanolett.7b00401. Epub 2017 Mar 30.
Progress in the terahertz (THz) region of the electromagnetic spectrum is undergoing major advances, with advanced THz sources and detectors being developed at a rapid pace. Yet, ultrafast THz communication is still to be realized, owing to the lack of practical and effective THz modulators. Here, we present a novel ultrafast active THz polarization modulator based on GaAs semiconductor nanowires arranged in a wire-grid configuration. We utilize an optical pump-terahertz probe spectroscopy system and vary the polarization of the optical pump beam to demonstrate ultrafast THz modulation with a switching time of less than 5 ps and a modulation depth of -8 dB. We achieve an extinction of over 13% and a dynamic range of -9 dB, comparable to microsecond-switchable graphene- and metamaterial-based THz modulators, and surpassing the performance of optically switchable carbon nanotube THz polarizers. We show a broad bandwidth for THz modulation between 0.1 and 4 THz. Thus, this work presents the first THz modulator which combines not only a large modulation depth but also a broad bandwidth and picosecond time resolution for THz intensity and phase modulation, making it an ideal candidate for ultrafast THz communication.
太赫兹（THz）光谱区域的进展正在取得重大进展，先进的太赫兹源和探测器正在快速发展。然而，由于缺乏实用有效的太赫兹调制器，太赫兹超高速通信仍有待实现。在这里，我们提出了一种基于 GaAs 半导体纳米线的新型超快主动太赫兹偏振调制器，这些纳米线呈栅格状排列。我们利用光泵太赫兹探针光谱系统，改变光泵束的偏振，演示了超快太赫兹调制，其开关时间小于 5 ps，调制深度为-8 dB。我们实现了超过 13%的消光比和-9 dB 的动态范围，与微秒级可切换的基于石墨烯和超材料的太赫兹调制器相当，超过了光可切换碳纳米管太赫兹偏振器的性能。我们展示了在 0.1 到 4 THz 之间的太赫兹调制的宽带宽。因此，这项工作提出了第一个太赫兹调制器，它不仅具有大的调制深度，而且具有宽的带宽和皮秒时间分辨率，用于太赫兹强度和相位调制，使其成为太赫兹超高速通信的理想候选者。
