A Dual-Frequency Quasi-Optical Output System for a THz Gyro-Multiplier

Abstract

This paper presents the investigation of a quasioptical output system for a fourth-harmonic gyro-multiplier in the THz band through geometric optic analysis and three-dimensional full-wave simulation. The output system of the gyro-multiplier needs not only to transfer two high-order waveguide modes into the quasi-Gaussian beams, but also to separate the two beams. A dual-frequency quasi-optical mode converter (DQMC) and a frequency selective surface (FSS) are employed to achieve both goals within this system. Our study has shown that the optimal design of the DQMC requires a special mode selection in the gyro-multiplier. The high-pass FSS is designed, fabricated, and experimentally verified by a THz-TDS system. We have also demonstrated that the designed FSS is capable of handling the high-power output from the gyro-multiplier.

Investigation of Frequency-Selective Surfaces for a THz Gyromultiplier Output System

“…4 shows a typical measured surface profile of the fabricated high-pass FSS with a DektakXT stylus surface profiler [29]. According to the surface profile data, the root-mean-squared (rms) surface roughness values of the high-pass and the low-pass FSSs are estimated to be within the range of 201±15 nm, which are about half of the value for the fabricated sample in [17]. Such reduction of the surface roughness can help to increase the effective conductivity and the volumetric breakdown threshold of air at the vicinity of the metal surface.…”

“…In 2015, the combination of quasi-optical mode converters (QMCs) [10]- [12] and FSSs in the output systems of the double-beam gyrotron and the fourth-harmonic gyro-multiplier [13] has been proposed in [14] and [15], respectively. Further development of the two systems are reported in [16] and [17], respectively. In these systems, the QMCs are used to transform the high-order waveguide modes into quasi-Gaussian beams and the FSSs are used to spatially separate the converted beams according to the frequencies.…”

“…To avoid the reflection back into the DQMC and the beam-wave interaction cavity, the FSSs are designed for oblique incidence with an incident angle of 15°. The incident quasi-Gaussian beams have a linear polarization pointing outwards from the paper [17], thus form a TE mode incidence regarding the FSSs. In Fig.…”

“…In our previous work [17], a high-pass FSS based on a square array of periodic perforations on a brass plate is reported with tested insertion loss values of 32.7 and 2.8 dB at 342 and 1368 GHz, respectively. The configuration is shown as Fig.…”

Design and Simulation of a Multi-Sheet Beam Terahertz Radiation Source Based on Carbon-Nanotube Cold Cathode

“…Due to its wide bandwidth, good directionality, high spatial and temporal resolution, terahertz (THz) technology has attracted wide interest in a range of applications, such as high data rate communications, radar systems, electronic countermeasures, biomedical diagnostics, and security inspection [1][2][3][4][5][6]. Vacuum electronic devices (VEDs), one of the several existing technologies capable of generating THz waves, have received extensive attention due to their high output power and high electronic efficiency [7,8].…”