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Chinese Physics Letters

Terahertz Detection with Twin Superconductor–Insulator–Superconductor Tunnel Junctions

Jing Li, Wang Ming-Jye, Shi Sheng-Cai, Hiroshi Matsuo

Published Jan 18, 2007• 4 citations
Publisher

Abstract

Terahertz detection with twin superconductor–insulator–superconductor (SIS) tunnel junctions, which are connected in parallel via an inductive thin-film superconducting microstrip line, is mainly studied. Firstly, we investigate the direct-detection response of a superconducting twin-junction device by means of a Fourier transform spectrometer. Secondly, we construct a direct-detection model of twin SIS tunnel junctions. The superconducting twin-junction device is then simulated in terms of the constructed model. The simulation result is found to be in good agreement with the measured one. In addition, we observe that the direct-detection response of the device is consistent with the noise temperature behaviour.

DOI
10.1088/0256-307x/24/2/075

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Jing Li, 王明杰, 史生才 +1 more

有成双的 superconductor-insulator-superconductor (SIS ) 的兆兆赫察觉隧道连接，经由一根引入的薄电影的 superconductingmicrostrip 线在平行被连接，主要被学习。第一，我们借助于一个 Fourier 变换分光计调查 asuperconducting 双胞胎连接设备的直接察觉的反应。第二， weconstruct 成双的 SIS 隧道连接的一个直接察觉的模型。超导的成双的 junctiondevice 然后以构造模型被模仿。模拟结果被发现是对测量那个的 ingood 同意。另外，我们观察到直接察觉的反应 ofthe 设备与噪音温度行为一致。

Chinese Physics Letters•Jan 1, 2007•0 citations
Terahertz detection with twin superconductor–insulator–superconductor (SIS) tunnel junctions, which are connected in parallel via an inductive thin-film superconducting microstrip line, is mainly studied. Firstly, we investigate the direct-detection response of a superconducting twin-junction device by means of a Fourier transform spectrometer. Secondly, we construct a direct-detection model of twin SIS tunnel junctions. The superconducting twin-junction device is then simulated in terms of the constructed model. The simulation result is found to be in good agreement with the measured one. In addition, we observe that the direct-detection response of the device is consistent with the noise temperature behaviour.
Abstract Superconducting integrated circuits based on NbTiN/Al transmission lines at frequencies of up to 1.1 THz have been developed and experimentally investigated. The numerical simulation has been carried out for two topologies of a microcircuit with an operating frequency range of 0.9‒1.2 THz, which contains a slot antenna formed in the NbTiN thin film and output-matched with a microstrip transmission line and a superconductor‒insulator‒superconductor (SIS) tunnel junction with an area of ~1 µm2 acting as a terahertz detector. Experimental samples of the microcircuit have been fabricated and tested in an experimental setup utilizing a backward-wave oscillator with an output frequency of up to 1.1 THz used as a source. The powerful pumping of the SIS detector has been obtained to demonstrate the applicability of the fabricated NbTiN/Al transmission lines for operation in superconducting circuits at frequencies above 750 GHz, where the conventional Nb/Nb transmission lines cannot operate due to high losses.
Heterodyne mixers based on superconducting SIS (superconductor-insulator-superconductor) tunnel junctions have been demonstrated to be the most sensitive coherent detectors at millimeter and submillimeter wavelengths. In fact, conventional superconducting SIS mixers with Nb/AlOx/Nb junction and Nb/SiO2/Nb tuning circuit have shown good performances with the noise temperature reaching as low as three times the quantum limit below 0.7THz, which is the gap frequency of Nb-based SIS junctions. However, due to the large loss in Nb thin-film superconducting microstrip lines, the noise performance of Nb SIS mixers deteriorates significantly above 0.7THz. With a gap frequency double that of Nb-based SIS junctions, NbN-based SIS junctions are of particular interest for the development of heterodyne mixers in the terahertz region. Considering the bandwidth and output power of local-oscillator (LO) signal sources are quite limited around 1THz, we firstly develop a waveguide NbN-based SIS mixer at 0.5THz. Three types of SIS junctions, i.e., long junction, parallel-connected tunnel junction (PCTJ) and distributed junction array (DJ) are investigated. They are all comprised of NbN-AlN-NbN tri-layer fabricated on an MgO substrate and have the same current density (Jc) of 10kA/cm2. In this paper, we describe their design, fabrication and preliminary experimental results.
This paper presents the direct-detection responses of a 500-GHz and a 660-GHz waveguide superconducting SIS (superconductor-insulator-superconductor) mixer measured with a Fourier transform spectrometer (FTS). The two superconducting SIS mixers adopt the same type of junction tuning circuit (i.e., parallel connected twin SIS junctions), but are of different designs for the junction feed point where RF signals are coupled and then transmitted to the SIS junction tuning circuit and have different mixer design criteria. The experimental results are discussed in detail.
Heterodyne mixers based on superconducting SIS (superconductor-insulator-superconductor) tunnel junctions have been demonstrated to be the most sensitive coherent detectors at millimeter and submillimeter wavelengths. In fact, conventional superconducting SIS mixers with Nb/AIO(x)/Nb junction and Nb/SiO2/Nb tuning circuit have shown good performances with the noise temperature reaching as low as three times the quantum limit below 0.7THz, which is the gap frequency of Nb-based SIS junctions. However, due to the large loss in Nb thin-film superconducting microstrip lines, the noise performance of Nb SIS mixers deteriorates significantly above 0.7THz. With a gap frequency double that of Nb-based SIS junctions, NbN-based SIS junctions are of particular interest for the development of heterodyne mixers in the terahertz region.
The terahertz band, a unique segment of the electromagnetic spectrum, is crucial for observing the cold, dark universe and plays a pivotal role in cutting-edge scientific research, including the study of cosmic environments that support life and imaging black holes. High-sensitivity superconductor–insulator–superconductor (SIS) mixers are essential detectors for terahertz astronomical telescopes and interferometric arrays. Compared to the commonly used classical Nb/AlO x /Nb superconducting tunnel junction, the Nb/AlN/NbN hybrid superconducting tunnel junction has a higher energy gap voltage and can achieve a higher critical current density. This makes it particularly promising for the development of ultra-wideband, high-sensitivity coherent detectors or mixers in various scientific research fields. In this paper, we present a superconducting SIS mixer based on Nb/AlN/NbN parallel-connected twin junctions (PCTJ), which has a bandwidth extending up to 490 GHz–720 GHz. The best achieved double-sideband (DSB) noise temperature (sensitivity) is below three times the quantum noise level.
有成双的 superconductor-insulator-superconductor (SIS ) 的兆兆赫察觉隧道连接，经由一根引入的薄电影的 superconductingmicrostrip 线在平行被连接，主要被学习。第一，我们借助于一个 Fourier 变换分光计调查 asuperconducting 双胞胎连接设备的直接察觉的反应。第二， weconstruct 成双的 SIS 隧道连接的一个直接察觉的模型。超导的成双的 junctiondevice 然后以构造模型被模仿。模拟结果被发现是对测量那个的 ingood 同意。另外，我们观察到直接察觉的反应 ofthe 设备与噪音温度行为一致。