Design of terahertz photoconductive antenna arrays based on defective photonic crystal substrates

Abstract

In this paper, arrays of two different terahertz (THz) antennas based on defective photonic crystal (DPC) substrates are proposed and their radiation characteristics are investigated by using full-wave simulation. We show that employing DPC substrates in THz photoconductive antenna (PCA) arrays reduces the amount of power coupled to the substrate surface waves and, as a result, decreases the mutual coupling between the elements of the antenna array and increases the directivity in the boresight direction. By studying 1 × 2 arrays of bowtie and four-leaf-clover-shaped antennas, we show that either the improvement of directivity in a broad bandwidth or the enhancement of photomixer antenna impedance at a resonant frequency can be considered in the design of the DPC substrate. Therefore, the proposed approach can significantly improve the efficiency and radiation performance of THz photomixer antennas resulting in an improved effective THz radiated power in the desirable direction. The proposed DPC substrate can be considered as a way to realize sub-millimeter-sized dielectric resonator antennas at terahertz frequencies. In addition, this cost-effective technique can reduce the necessity of exploiting hyper-hemispherical Si lenses by overcoming the adverse effects of the thick substrate which is of prime importance in PCA arrays from a practical viewpoint.