Simulation On Physics Properties Of Superconducting Terahertz Emitters And Design Of A Compact Measure System Of High-Temperature Superconductor Devices

With the advantages like continuous-wave radiation,tunable emission frequency,proper emission frequency range,superconducting emitters fabricated from high-temperature superconductor Bi₂Sr₂Ca Cu₂O₈?intrinsic Josephson junctions?,which may have a profound potential in reality applications,are drawing increased attention and researchers in the THz academic area.Emission power and frequency are the most vital factors when we measure the emission properties of these superconducting emitters.One of the most effective ways to enhance the emission frequency is to improve the thermal conduction of the device.Here,by using COMSOL Multiphysics,we paid special attention to the gold film which was used as electrodes in superconducting terahertz emitter.We investigated the thickness dependence of gold film resistivity by both experiment and theory,and its effect on the device performance from the thermal aspect.We found that gold film with increasing thickness has a better cooling performance,which may bring a higher voltage and emission frequency.The Low Temperature Scanning Laser Microscope?LTSLM?system is a significant setup to study the emission properties of the terahertz emitter.This thesis designs a shorter wavelength laser and optical path system,which improves the resolution of the microscope.On the other hand,we can characterize devices with smaller scales.Besides,because the laser works in the visible light band,we can also study other electronic devices like Si nanowires and solar cells.After that,we used COMSOL to investigate the mechanism for the high laser absorption rate of radial silicon nanowires.By comparing with the results of the laser microscope scanning experiment,we found that laser scattering between the outer walls of these nanowires would cause the nanowires to absorb the laser many times,as a result it will increase the light absorption rate of the Si nanowires.In addition,in order to improve the flexibility and portability of the high-temperature superconducting device measure system,we designed and built a compact high-temperature superconducting device measure system based on a Linear-separation Stirling cryocooler.With great efforts,the minimum cooling temperature of the system is 50 K,and it can be cooled from room temperature to 70 K in only 7 minutes.In conclusion,the system could be used tomeasure superconducting Terahertz emitters effciently.