超导太赫兹辐射源物性与调控研究

发布时间：2019-01-08 11:43

【摘要】：高温超导本征约瑟夫森结阵(Bi_2Sr_2CaCu_2O_8单晶)制备了成的超导太赫兹辐射源因其特殊的器件特性,如其辐射波为连续波、辐射频率连续可调、频段适中、功率可观等,而越来越受到研究人员的关注,也有望成为适合实际应用的连续波太赫兹辐射源,并促进太赫兹技术的发展。在对超导太赫兹辐射源的研究过程中,我们在国际上首创了集成超导太赫兹辐射源辐射特性测试和低温扫描激光显微镜成像测试的综合测试系统。该系统可同时检测超导太赫兹辐射源的外部辐射特性和器件内部的电磁能量分布以及温度分布。此套测试系统极大地帮助我们加深了对超导太赫兹辐射源器件物理的理解,并帮助改进超导太赫兹辐射源的设计、提升超导太赫兹辐射源的性能。利用该综合测试系统,我们研究了辐射源器件的辐射特性与器件内部电磁驻波的关系。在器件辐射功率达到峰值时,我们在器件内部测得了满足谐振模式与频率关系的驻波图案,得出了器件中电磁谐振增强辐射功率的结论。在通过综合测试系统理解了辐射源的器件物理后,我们针对实际应用的需求,设计和制备了原创结构的超导太赫兹辐射源,同时也提出了改善太赫兹辐射源辐射特性的外部调节技术。针对实际应用对太赫兹辐射源提出的调控需求,我们设计了 "三端-独立"结构超导太赫兹辐射源。有别于传统的超导太赫兹辐射源,该种结构的超导太赫兹辐射源具有三个电极。采用特殊的电流偏置方式,能够在超导太赫兹辐射源内部产生可以移动的高温热区。通过控制辐射源内部高温热区的位置,在总偏置电流固定的情况下,辐射频率可调范围为8%;在电流偏置比例固定的情况下,辐射频率可调范围为10%-20%。因此,通过这种器件结构,我们实现了调控超导太赫兹辐射源辐射特性的目的。此外,受器件焦耳热产生的高温热区能影响超导太赫兹辐射源辐射特性这一特殊物理现象的启发,我们提出了使用外部热源激励辐射源器件,进而调谐辐射源辐射特性的调控方案。我们采用聚焦的激光束来调控辐射源器件后,辐射源的功率可在100%-175%之间连续调节。通过研究激光束调控后的辐射功率与激光的位置以及激光光强等因素之间的关系,我们得到了聚集激光束作为额外热源对超导太赫兹辐射源的调控机制,并能可控地使用激光束调谐超导辐射源。综上,通过设计、搭建原创的测试系统,我们研究了超导太赫兹辐射源中的多种物理现象,并由此提出、实现了创新结构的超导太赫兹辐射源器件和创新的太赫兹辐射源的外部调谐方案,以满足实际应用对太赫兹辐射源调控方面的需求。
[Abstract]:The superconducting terahertz radiation source prepared by high temperature superconducting intrinsic Josephson junction array (Bi_2Sr_2CaCu_2O_8 single crystal) is suitable for its special device characteristics, such as continuous wave, continuously adjustable radiation frequency and moderate frequency range. Because of its considerable power, researchers are paying more and more attention to it, which is expected to be a continuous wave terahertz radiation source suitable for practical application, and to promote the development of terahertz technology. In the process of studying superconducting terahertz radiation source, we have created a comprehensive testing system which integrates the radiation characteristics of superconducting terahertz radiation source and the low-temperature scanning laser microscope imaging test. The system can simultaneously detect the external radiation characteristics of the superconducting terahertz radiation source and the electromagnetic energy distribution and temperature distribution inside the device. This test system has greatly helped us to deepen our understanding of the physics of superconducting terahertz radiation sources and to improve the design of superconducting terahertz radiation sources and improve the performance of superconducting terahertz radiation sources. Using the integrated measurement system, we study the relationship between the radiation characteristics of the radiation source devices and the electromagnetic standing waves inside the devices. When the radiation power of the device reaches the peak, the standing wave pattern satisfying the relationship between the resonant mode and the frequency is measured in the device, and the conclusion of the electromagnetic resonance enhanced radiation power in the device is obtained. After understanding the device physics of the radiation source through the comprehensive test system, we designed and fabricated the superconducting terahertz radiation source with original structure according to the practical application demand. At the same time, the external regulation technology to improve the radiation characteristics of terahertz radiation source is also proposed. In order to meet the requirements of practical applications for the regulation of terahertz radiation sources, we have designed a "three-terminal independent" superconducting terahertz radiation source. Different from the traditional superconducting terahertz radiation source, the superconducting terahertz radiation source has three electrodes. By using special current bias, a movable high temperature heat region can be generated in the superconducting terahertz radiation source. By controlling the position of the high temperature heat region inside the radiation source, the radiation frequency can be adjusted in the range of 8 when the total bias current is fixed, and in the case of fixed current bias ratio, the adjustable range of the radiation frequency is from 10 to 20. Therefore, through this device structure, we can control the radiation characteristics of superconducting terahertz radiation source. In addition, inspired by the special physical phenomenon that the high temperature heat region produced by the Joule heat of the device affects the radiation characteristics of the superconducting terahertz radiation source, we propose to use an external heat source to excite the radiation source device. And then tuning the radiation characteristics of the radiation source control scheme. After the focused laser beam is used to control the radiation source device, the power of the radiation source can be continuously adjusted between 100% and 175%. By studying the relationship between the radiation power of the laser beam and the position of the laser and the intensity of the laser, we obtained the mechanism of the superconducting terahertz radiation source by using the aggregated laser beam as an additional heat source. The laser beam can be used to tune the superconducting radiation source. In summary, by designing and building an original testing system, we have studied various physical phenomena in superconducting terahertz radiation sources, and put forward that, The novel superconducting terahertz radiation source device and the innovative terahertz radiation source external tuning scheme are realized to meet the requirements of practical application in the regulation of terahertz radiation source.
【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】：O551;O441.4

【相似文献】