Development of high sensitive superconducting detectors for terahertz spectral imaging

本文研究了YBa_2Cu_3O_7（YBCO）晶界约瑟夫森结与不同类型天线集成的太赫兹波探测器的制备及其在0.1 ~ 4.2THz范围内的敏感特性。探测器采用平面对数周期天线（LPA），射频耦合损耗约为-26dB。我们发现，阻抗失配损耗是RF耦合损耗的主要部分。采用共面波导馈电缝隙偶极子阵列（SDA）代替LPA的探测器表明RF耦合损耗改善约20 dB。利用FDTD方法对SDA的辐射特性进行了数值模拟，发现SDA的低辐射阻抗有助于提高灵敏度。为了进一步改善阻抗失配损耗，本征Josephson结（多个结串联）是一种阻抗更高的敏感元件。虽然用谐振天线代替LPA的探测器带宽较窄，但通过数值模拟发现，在0.2THz谐振时，缝隙偶极子的相对带宽约为50%。

We have investigated fabrication of terahertz wave detectors of YBa_2Cu_3O_7 (YBCO) grain boundary Josephson junctions integrating with various types of antenna and their sensing properties from 0.1 to 4.2 THz. The detector with a planar log-periodic antenna (LPA) indicated the RF coupling loss of about -26dB. We revealed that an impedance miss-matching loss was a dominant part of the RF coupling loss. A detector with a coplanar waveguide-fed slot dipole array (SDA) instead of LPA indicated an improvement in the RF coupling loss of about 20dB. The detector with SDA achieved the sensitivity of 1,400 (V/W).We carried out numerical simulations on radiation properties of SDA by the FDTD method and revealed that low radiation impedance of SDA have contributed the improvement in the sensitivity. For further improvement in the impedance miss-matching loss, intrinsic Josephson junctions in which many junctions are connected in series is one of candidates as sensing elements with higher impedances.Although detectors with resonance antenna replaced LPA have narrow band widths, we have found that the slot dipole shows the relative band width of about 50% at 0.2 THz resonance by numerical simulations.