Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87106, United States.
Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, New Mexico 87131, United States.
ACS Nano. 2021 Jan 26;15(1):1229-1239. doi: 10.1021/acsnano.0c08296. Epub 2020 Dec 18.
We present a transformative route to obtain mass-producible helical slow-wave structures for operation in beam-wave interaction devices at THz frequencies. The approach relies on guided self-assembly of conductive nanomembranes. Our work coordinates simulations of cold helices (i.e., helices with no electron beam) and hot helices (i.e., helices that interact with an electron beam). The theoretical study determines electromagnetic fields, current distributions, and beam-wave interaction in a parameter space that has not been explored before. These parameters include microscale diameter, pitch, tape width, and nanoscale surface finish. Parametric simulations show that beam-wave interaction devices based on self-assembled and electroplated helices will potentially provide gain-bandwidth products higher than 2 dBTHz at 1 THz. Informed by the simulation results, we fabricate prototype helices for operation as slow-wave structures at THz frequencies, using metal nanomembranes. Single and intertwined double helices, as well as helices with one or two chiralities, are obtained by self-assembly of stressed metal bilayers. The nanomembrane stiffness and built-in stress control the diameter of the helices. The in-plane geometry of the nanomembrane determines the pitch, the chirality, and the formation of single vs intertwined double helices.
我们提出了一种变革性的方法，可用于在太赫兹频率的束波相互作用器件中获得大规模生产的螺旋慢波结构。该方法依赖于导电纳米膜的引导自组装。我们的工作协调了冷螺旋（即没有电子束的螺旋）和热螺旋（即与电子束相互作用的螺旋）的模拟。理论研究确定了以前未探索过的参数空间中的电磁场、电流分布和束波相互作用。这些参数包括微尺度直径、螺距、带宽度和纳米尺度表面光洁度。参数模拟表明，基于自组装和电镀螺旋的束波相互作用器件将有可能在 1 THz 时提供高于 2 dBTHz 的增益带宽产品。受模拟结果的启发，我们使用金属纳米膜制造了原型螺旋，用作太赫兹频率的慢波结构。通过受压金属双层的自组装，获得了单螺旋和交织双螺旋，以及具有一个或两个手性的螺旋。纳米膜的刚度和内建应力控制着螺旋的直径。纳米膜的面内几何形状决定了螺距、手性以及单螺旋与交织双螺旋的形成。
