High-Q terahertz bandstop filter via cuboid frame structure

Abstract

A terahertz (THZ) bandstop filter can be used to filter interference signals in a filter passband. The quality factor (Q) is the most important index in evaluating the transmission performance of the filter. Usually, a higher Q value, a narrow bandwidth and a larger stopband slope ensures good filtering accuracy and transmission response. However, the Q value taken from metamaterial structures designed on the plane is only ever in single digits, resulting in a less than satisfactory filtering performance. Herein, a high-Q THZ bandstop filter based on metamaterials was proposed. To fabricate this 3D metamaterial structure, a microtopographic substrate-guided method with feasible and high accuracy capacities was proposed. As a result, it is ascertained that the device is in the filtering state in the range 1.038–1.102 THz while it is stopped in the range 1.062–1.066 THz. The similarity between the experimental and simulated transmissions is up to 86.32%, indicating that the fabricating method possesses high accuracy. Accordingly, the Q value was calculated to be as high as 532. In future, the bandstop filter with this record Q value can be widely used in THZ detection, imaging and sensing. Meanwhile, the proposed fabrication method is effectively applied to a 3D metamaterial and a THZ device as well.