Research On Superconducting Terahertz Radiation Source And Small High-Temperature Superconducting Test System

Terahertz(THz)waves refer to electromagnetic waves with a frequency range of0.1 THz to 10 THz.Due to their special location on the electromagnetic spectrum,they have great theoretical research values and practical application prospects.For a long time,due to the lack of a stable CW terahertz source and the lack of effective terahertz wave detection technology,the research and application of terahertz wave have been developed slowly,so it is called"terahertz gap".As the basic component of superconductivity electronics,the Josephson junction is a kind of macroscopic quantum device which is composed of two weakly coupled superconductors.When two superconductors are separated by an insulator of a suitable thickness,even without a voltage drop across the junction,the supercurrent can still go through the insulator without any loss.This is the DC Josephson effect.When the current passing through the Josephson junction gradually increases and exceeds its critical current,a potential difference will be formed across the junction.At this time,the current passing through the Josephson junction is an alternating current with the oscillation frequency f=2ev/h.So the Josephson junction is an ideal voltage-frequency converter.It can be said that the discovery of the Josephson effect is an important milestone of superconductor electronics,so the researches around the Josephson junction are of great significance.Based on the AC Josephson effect in superconducting Josephson devices,ones can be used as high-efficiency voltage-frequency converters,and superconducting materials can be used to prepare high-performance terahertz radiation sources and high-sensitivity terahertz detectors.High temperature superconductor(HTS)mainly refers to materials that are superconducting above the liquid nitrogen temperature(77 K).Because high-temperature superconducting materials have a higher energy gap than traditional that of superconducting materials,terahertz sources and detectors using high-temperature superconducting materials have the advantages of wide frequency and high operating temperature.For example,High-temperature superconductor Bi₂Sr₂Ca Cu₂O_8+?(BSCCO)intrinsic Josephson junctions are very suitable for making high-temperature superconducting terahertz sources and terahertz detectors.Radiation sources and detectors based on high-temperature superconductors are of great application value.However,due to the limitations of the test system,there is still a lack of a portable,lightweight and compact mobile measuring system.Therefore,this dissertation has launched a research on this point.Firstly,a new BSCCO high-temperature superconducting Josephson micro-bridge junction was studied,which can be a start point for the preparation of new SQUID(superconducting quantum interference device)and SQIF(superconducting quantum interference filter).The Josephson junction itself can also be used as a direct or heterodyne terahertz wave detector.Secondly,based on the C376 cryocooler,a test system for high-temperature superconducting device was built,and the test of BSCCO terahertz radiation source was carried out,which verified the usability of the system.Finally,using this setup we carried out harmonic mixings at 52 K with a BSCCO Josephson junction detector fabricated with a double-sided process.The detected signal is 110 GHz,and the maximum harmonic number reaches 67.