In this paper we explore an adaptation of a high-temperature superconducting (HTS) Josephson R-SQUID (Resistive Superconducting Quantum Interference Device) heterodyne oscillator for the detection of terahertz (THz) radiation. This approach can be potentially applied for a large array detector readout in the frequency domain. The design concepts for the R-SQUID THz detector and early measurement results of its response to a THz signal are presented here.
In this paper we explore an adaptation of a high-temperature superconducting (HTS) Josephson R-SQUID (Resistive Superconducting Quantum Interference Device) heterodyne oscillator for the detection of terahertz (THz) radiation. This approach can be potentially applied for a large array detector readout in the frequency domain. The design concepts for the R-SQUID THz detector and early measurement results of its response to a THz signal are presented here.
The CSIRO Applied Superconductivity Group has a long-term effort in research and development of superconducting electronic devices and systems for various practical applications. In this paper, I will mainly describe our recent research progress in developing novel HTS Josephson devices for high frequency applications. Specifically, we have recently developed a novel HTS Josephson heterodyne gigahertz (GHz) microwave oscillator and on-chip down-converter (mixer). For even higher frequency application, we developed a HTS Josephson junction terahertz (THz) detector and applied it successfully to THz imaging. I will highlight some of the recent results and describe the on-going effort of developing an array of such detectors and associated electronics as well as system integration.
We report a novel terahertz (THz) detector with a high- T c superconducting (HTS) Josephson junction. This detector was fabricated using a YBa 2 Cu 3 O 7-δ grain boundary junction. Clear THz signals induced by THz-pulse radiation from an ultrafast photoconductive antenna excited by femtosecond optical pulses were observed. We investigated the characteristics of the detector by changing the parameters of THz radiation such as pump laser power for the THz emitter and THz polarization. The results indicate that the detector mainly detects the THz electric fields. This is the first demonstration of a detection of pulsed THz electric fields using an HTS Josephson junction.
The terahertz regime, as a last radio window, remains to be fully explored, and astronomical and atmospheric observations in this regime are scientifically important. Like other frequency regimes, developing high-sensitivity detectors (coherent and incoherent) is of particular significance for both ground-based and space-borne facilities. As the coherent detector of choice below 1.4 THz, superconductor-insulator-superconductor (SIS) heterodyne mixers have achieved as high a sensitivity as five times the quantum limit around 1.4 THz. It is, however, still a challenge to developing SIS mixers at frequencies beyond 1.4 THz with considerable transmission loss in superconducting circuits due to the Cooper-pair breaking by energetic photons and increased many difficulties in designing and fabricating. So far, superconducting hot electron bolometer (HEB) mixers have been the most sensitive heterodyne detectors at frequencies above 1.5 THz, and successfully used to detect molecular spectral lines up to 2.5 THz from ground-based and space telescopes. Although spiral-antenna coupled NbN HEB mixers show a good sensitivity in the whole THz frequency range, the directly measured spectral response with Fourier transform spectrometer falls quickly as frequency increases, especially above 3 THz. The terahertz band is also of particular importance to observe astronomical objects such as cosmic microwave background, early distant objects, cold objects and dusty objects. Aiming at such objects, we develop a terahertz imaging array system by combining advanced superconducting detectors such as transition edge sensor (TES) and microwave kinetic inductance detectors (MKIDs), thus the system has a frequency band centred at 350 m, an operational temperature of 0.3 K, and a sensitivity reaching background limit performance for ground-based applications. In addition, it is expected to have some breakthroughs in ultra-sensitive superconducting TES and MKID, low noise multi-channel readout and multiplexing, efficient terahertz-wave coupling technology, and large-scale array system integration. The developed terahertz imaging array system will serve as the next-generation instrument of Dome A 5 m terahertz telescope, conducting a 350 m-band legacy survey for studying the planets, stars, galaxies and cosmology. Besides the application in astronomy, the developed terahertz imaging array system can also be applied to some areas requiring rapid detection such as security, deep space exploration, and biomedical imaging. In this paper, we mainly introduce the superconducting detectors developed at Purple Mountain Observatory and those for international collaborative projects.
Abstract Terahertz (THz) technology is a rapidly developing field that explores the use of electromagnetic waves in the THz frequency range. The unique properties of THz waves have great application prospects in electromagnetic sensing, security inspection, non-destructive testing, medical diagnostics, biology, high-speed wireless communication, space science and so on. At present, the application of THz technology is still under continuous research and development, and its broad scientific prospects are recognized worldwide. THz frequency falls into the gap on the electromagnetic spectrum of electronics and optics, thus both classic microwave and optical technologies cannot be directly applied to the THz systems. New components, circuits and application systems are being developed for THz technology. Superconductivity is a quantum mechanical phenomenon and offers unique advantages for applications in high-frequency electromagnetic domains. Novel superconducting quantum devices are being exploited for THz wave radiation and detection, and many THz application systems. The high-T c superconducting (HTS) electronic devices have great potential in emerging THz technologies due to its very high-energy bandgap (well into THz regions) and much relaxed cooling requirement, and they offer strong prospect for the development of practical and portable THz systems. This paper provides an overview of the state-of-art development of HTS THz quantum devices and their application for THz sensing, imaging and communication. The review will start with a brief introduction about cutting-edge THz technology, the fundamental of superconductivity, Josephson effects and the HTS Josephson junctions. Then, the research progress and the latest achievement of HTS Josephson THz emitters, detectors and mixers will be reviewed, followed by their application examples in some THz systems. Finally, the conclusion, challenges and outlooks of the HTS technologies in THz applications are discussed.
This paper reviews our major technical achievement in high-Tcsuperconducting (HTS) terahertz (THz) receivers or heterodyne mixers in recent years. By virtue of innovative on-chip antenna/circuit designs, accurate device modelling and simulation, and advanced YBa2Cu3O7-x (YBCO) step-edge junction technology, we have successfully developed a series of HTS Josephson THz mixers with superior performance in terms of operating temperature, intermediate-frequency (IF) bandwidth, conversion gain and noise temperature. These mixers serve as promising receiver frontends for THz wireless communication and sensing systems.
The terahertz region of the electromagnetic spectrum [0.3-10THz] has, so far, not been exploited fully due to the lack of suitable sources and detectors. Indeed, THz frequency lies between the frequency range of traditional electronics and photonics where the existing technology cannot be simply extended. SIS Niobium tunnel junctions that are currently used as mixing element in heterodyne receivers are intrinsically limited in frequency by the energy gap of Nb and operate only at low temperature (4.2K). An alternative to these devices consists of using High-Tc superconducting receivers. Over the past years, we have developed a new approach based on ion irradiation to make Josephson nano-junctions and SQUIDs with YBCO thin films [1,2]. In this talk, we will present a study of the high-frequency mixing properties of such junctions up to 400 GHz [3]. Conversion gain has been measured at frequencies spanning the range below and above the characteristic frequency fc = (2e/h)IcRn of the junctions. The transition between two distinct mixing regimes has been clearly evidenced, in good agreement with the prediction of the three ports model.[1] N. Bergeal et al., Appl. Phys. Lett. 87, 102502 (2005)[2] N. Bergeal et al., Appl. Phys. Lett. 89, 1112515 (2006)[3] Luo et al, arXiv:1203.1734 (2012)