Influence of Coupled Structural Parameters of Photoconductive Antennas on the Terahertz Narrowband Detection Performance of High Sensitivity and Frequency Selection

Abstract

Narrowband terahertz (THz) detection plays a key role in biomedical imaging, biological applications, and security screening. Particularly rapid resolution of material differences based on spectral fingerprints or time-resolved observation of the materials conformational state typically requires only the measurement of spectral information at a few selected frequencies. Here, a high-performance resonance-based coupled photoconductive antenna (PCA) was designed, which consists of a square split-ring resonator (SRR) and an H-shaped antenna. The incident THz wave energy can be effectively coupled in the gap of the H-shaped antenna, and the coupling effect base on coupled harmonic oscillator model can be effectively strengthened. By decreasing the square SRR gap width HD, the relative position parameters of d and L3 between the square SRR and H-shaped antenna can markedly improve the resonance frequency sensitivity with inductive–capacitive resonance. With the square SRR arm length L1=L2=L increased, the resonance frequency markedly shifted toward a lower frequency and the resonance sensitivity increased. The results prove that the THz frequency selection detection range of the coupled PCA can be designed to 0.1∼1.0 THz. Compared with the traditional H-shaped photoconductive detection antenna, the detection resonance peak shifted the lower frequency and the maximum THz detection sensitivity increased by approximately two orders of magnitude at 0.2528 THz. The structure of the noncontact micrometer–coupled PCA is simple and easy to fabricate and integrate. Our findings may also help to advance the use of THz technology in rapid distinguish material properties.