Yu Mei, Geng Haifeng, Jiang Shoulu, Hua Tao, An Deyue, Xu Weiwei, Chen Zhi Ning, Li Jun, Wang Huabing, Chen Jian, Wu Peiheng
Opt Express. 2020 May 11;28(10):14271-14279. doi: 10.1364/OE.390997.
In a quasi-optical system, the high temperature superconducting terahertz detector often suffers from a fundamental problem of low coupling efficiency with the terahertz signal, especially for the detector based on YBaCuO (YBCO) bicrystal Josephson junction (JJ) due to a small normal-state resistance. Here, we developed a bowtie loaded meander antenna to enhance coupling efficiency. Differing from the conventional characterization confining on vector network analyzers, we applied three methods to evaluate the antenna, including the measurements of the maximal size of the first order Shapiro step under per incident power, the coupling efficiency between the antenna and the junction, and voltage responsivity. Furthermore, with simulation analysis, we propose that the inductive reactance of the YBCO bicrystal JJ is around 60 ohms under terahertz irradiation at 210 GHz, thus, the reactance is comparable as that of the antenna.
