Theoretical Study of a 0.22 THz Backward Wave Oscillator Based on a Dual-Gridded, Carbon-Nanotube Cold Cathode

Qingyun Chen,Yang Yan,Matthew Cole,Yu Zhang,Lin Meng,Xuesong Yuan

doi:10.3390/app8122462

Abstract

The carbon nanotube (CNT) cold cathode is an attractive choice for millimeter and terahertz vacuum electronic devices owning to its unique instant switch-on and high emission current density. A novel, dual-gridded, field emission architecture based on a CNT cold cathode is proposed here. CNTs are synthesized directly on the cathode surface. The first separating grid is attached to the CNT cathode surface to shape the CNT cathode array. The second separating grid is responsible for controlled extraction of electrons from the CNT emitters. The cathode surface electric field distribution has been improved drastically compared to conventional planar devices. Furthermore, a high-compression-ratio, dual-gridded, CNT-based electron gun has been designed to further increase the current density, and a 21 kV/50 mA electron beam has been obtained with beam transparency of nearly 100%, along with a compression ratio of 39. A 0.22 THz disk-loaded waveguide backward wave oscillator (BWO) based on this electron gun architecture has been realized theoretically with output power of 32 W. The results indicate that higher output power and higher frequency terahertz BWOs can be made using advanced, nanomaterial-based cold cathodes.

Highlights

Terahertz radiation sources have gleaned much attention due to the wide range of potential applications of such devices, such as high data rate communications; the identification of concealed weaponry; remote, high-resolution imaging; and biomedical diagnostics [1,2,3,4,5]
A dual-gridded field emission architecture based on carbon nanotube (CNT) cold cathode is investigated here to solve the non-uniform electric field distribution at the cathode surface, which is the major cause of
A dual-gridded field emission architecture based on CNT cold cathode is investigated here to cathode arcing

Summary

Introduction

Terahertz radiation sources have gleaned much attention due to the wide range of potential applications of such devices, such as high data rate communications; the identification of concealed weaponry; remote, high-resolution imaging; and biomedical diagnostics [1,2,3,4,5]. Several existing technologies to generate terahertz waves are currently available, including quantum cascade lasers, solid state electron devices, and optical devices [6,7,8,9]. They have many intrinsic restrictions such as poor anti-interference performance, deleterious responsiveness to incident radiation, and the need for cryogenic cooling, which is often coupled to challengingly low output power.

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