Research On Device Physics And Modulation Of Superconducting Terahertz Emitters

With tunable emission frequency,proper frequency range and considerable emission power,superconducting terahertz emitters fabricated from high temperature superconductor Bi₂Sr₂CaCu₂O₈?intrinsic Josephson junctions?,which are considered as a versatile candidate in reality applications,are now attracting more and more researchers.In order to have a better understanding of superconducting terahertz emitters and the ability to promote the emission properties of these emitters,we designed and built up a multifunction measurement system that combines the general emission measurement system of superconducting terahertz emitters and the Low Temperature Scanning Laser Microscope?LTSLM?.It is this system that can measure the distribution of electromagnetic power and the distribution of temperature inside the device while detecting the properties of emission from the device at the same time.With such a powerful system,we are able to figure out a lot of underlying device physics.It also prompts the redesign and development of superconducting terahertz emitters.With the mentioned system,we studied the relationship between the emission power with the standing-wave inside the emitter.It came out that emission peaks were always accompany by the standing-wave inside the emitter while the resonant mode of such standing-wave was also coincident with the emission frequency.After studying device physics of superconducting terahertz emitters,we designed and fabricated superconducting terahertz emitters with new structures and also developed modulation method on superconducting terahertz emitters,to satisfy the requirement of reality applications.To have a desired tunable superconducting terahertz emitter,we designed and fabricated three-terminal superconducting terahertz emitter of which the device structure is rather new.Moving the position of hot spot was then realizable by modifying the injection configuration.We thus can control the emission properties by controlling the hot spot region.With a constant total bias current,moving hot spot brings an extra frequency tunability about 8%.And under a fixed current ratio,the frequency tunability is about 10%-20%by varying the total bias current.Apart from the hot spot region generated by the Joule heating,we also tried to stimulate the superconducting terahertz emitter with external heating source.We were able to tuning the emission power continuously from 100%to 175%,by applying a focus laser spot on the superconducting terahertz emitter.And with the study on the mechanism of such tuning phenomenon,controllable modulation on the emission properties was realized.In a word,with a versatile measurement system we made,we had a deep understanding of superconducting terahertz emitters.With a deep understanding,we designed and fabricated advanced superconducting terahertz emitters.With advanced emitters,we hope we can have a better future of the terahertz technology and thus a better life.