高温超导太赫兹辐射源的性能优化

发布时间：2018-06-23 22:04

本文选题：太赫兹辐射源 + 本征约瑟夫森结阵　；参考：《南京大学》2017年博士论文

【摘要】：高温超导太赫兹辐射源是通过微加工技术制备而成的Bi2Sr2CaCu2O8(BSCCO)本征约瑟夫森结阵,具有频段适中、可调谐、连续波、易制备等优势,有力地推动了太赫兹技术的发展,具有重要研究意义和巨大应用潜力。本论文分别从结构创新和实用创新角度出发,对高温超导太赫兹辐射源的性能优化,如提高辐射频率、增强实用性等方面,进行了积极探索和尝试,主要研究成果如下:1.带有孔隙微扰的BSCCO结阵。将微扰法引入高温超导太赫兹辐射源的研究,设计并制备出一种带有孔隙微扰的BSCCO本征约瑟夫森结阵。实验发现,当孔隙数大于1时,电流-电压特性(IVCs)曲线上会出现电压台阶。更重要的是,随着孔隙数目的增加,结阵电压不断增大,辐射频率也不断提高。因此,这种结构微扰为优化结阵性能提供了新的可行方式。2."片上"温度检测方式。对于BSCCO结阵,我们提出"片上"温度检测方式,将BSCCO检测器小结原位制备于辐射结阵表面,作为温度传感器。通过将不同温度下与不同辐射结阵偏置条件下的小结的IVCs曲线进行比对,获得小结所处位置的辐射结阵的表面温度。这是首次利用实验手段进行的结阵表面温度检测,对于研究结阵内部热分布和热传导具有积极意义。3.太赫兹"手电筒"。现有的太赫兹辐射源大多存在体积大、成本高、系统复杂等弊端,为此,我们研发出一套液氮冷却的便携式小型高温超导太赫兹辐射装置,且具有温度调节功能。该装置体积不足40cm3,最大辐射功率1.17μW,最大可调谐带宽100GHz。另外,还可用一节1.5V干电池和偏置调节模块替代复杂的电流源系统,使其能够像"手电筒"一样便于使用。这项工作初步实现了太赫兹源的小型化、实用化和低成本化,为促进高温超导太赫兹技术的实际应用起到了推进作用。4.功率可调的高温超导太赫兹辐射装置。二氧化钒(VO2)具有金属-绝缘体相变特性,可对电磁波的透射起到调控作用。我们首次将VO2相变薄膜与高温超导太赫兹源进行有效结合,把VO2低温电控相变作为可调衰减器,在保持温度和频率不变的条件下,实现了高温超导太赫兹源的功率调控,在20K和25K分别获得了-5.6dB和-4.3dB的最大衰减。这种适用于全低温环境的功率可调太赫兹源及其衰减器,进一步丰富了太赫兹技术的功能性和实用性,也为学科间的交叉融合提供了典型范例。另外,我们还通过室温和低温电控相变实验,并借助电子关联效应进行分析,为"热与电场共同作用引起电激发相变"这一观点提供了依据。
[Abstract]:High temperature superconducting terahertz radiation source is an intrinsic Josephson junction array of Bi2Sr2CaCu2O8 (BSCCO) prepared by microfabrication technology. It has the advantages of moderate frequency band, tunable, continuous wave and easy preparation, and has promoted the development of terahertz technology. It has important research significance and great application potential. In this paper, from the perspective of structural innovation and practical innovation, the performance optimization of HTS terahertz radiation sources, such as increasing radiation frequency and enhancing practicability, has been actively explored and tried. The main research results are as follows: 1. BSCCO array with pore perturbation. A BSCCO intrinsic Josephson array with pore perturbation was designed and fabricated by introducing the perturbation method into the study of high temperature superconducting terahertz radiation source. It is found that voltage steps appear on the current-voltage characteristic (IVCs) curve when the number of pores is larger than 1. More importantly, as the number of pores increases, the array voltage increases and the radiation frequency increases. Therefore, this kind of structure perturbation provides a new feasible way to optimize the performance of the array. " On-chip "temperature detection method." For the BSCCO array, we propose a "on-chip" temperature detection method. The BSCCO detector junction is prepared in situ on the surface of the radiation junction array as a temperature sensor. By comparing the IVCs curves of the nodule at different temperatures with those under different bias conditions, the surface temperature of the nodule is obtained. This is the first time to detect the surface temperature of a junction array by means of experiments, which has a positive significance for the study of the thermal distribution and heat conduction in the junction array. Terahertz "flashlight". Most of the existing terahertz radiation sources have many disadvantages, such as large volume, high cost and complex system. Therefore, a portable high temperature superconducting terahertz radiation device with liquid nitrogen cooling has been developed and has the function of temperature regulation. The volume of the device is less than 40 cm ~ 3, the maximum radiation power is 1.17 渭 W, and the maximum tunable bandwidth is 100 GHz. In addition, a 1.5 V dry battery and offset adjustment module can be used to replace the complex current source system, making it as easy to use as a flashlight. This work has preliminarily realized the miniaturization, practicality and low cost of terahertz source, and has played an important role in promoting the practical application of HTS THz technology. High temperature superconducting terahertz radiation device with adjustable power. Vanadium oxide (VO _ 2) has the characteristics of metal-insulator phase transition, which can regulate the transmission of electromagnetic wave. For the first time, the VO _ 2 phase change thin film is effectively combined with the high temperature superconducting terahertz source. The VO _ 2 low temperature electronic controlled phase transition is used as an adjustable attenuator, and the power control of the high temperature superconducting terahertz source is realized under the condition of keeping the temperature and frequency constant. The maximum attenuation of -5.6dB and -4.3dB is obtained at 20K and 25K, respectively. The power tunable terahertz source and its attenuator suitable for full low temperature environment further enrich the functionality and practicability of terahertz technology and provide a typical example for interdisciplinary cross fusion. In addition, through the electrically controlled phase transition experiments at room temperature and low temperature and with the aid of electron correlation effect, we provide a basis for the viewpoint that "the interaction of heat and electric field leads to the electric excited phase transition".
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O441.4

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