posted on 2020-12-18, 18:09authored byDivya
J. Prakash, Matthew M. Dwyer, Marcos Martinez Argudo, Mengistie L. Debasu, Hassan Dibaji, Max G. Lagally, Daniel W. van der Weide, Francesca Cavallo
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.