Research On The Characteristics Of Terahertz Superconducting Dynamic Inductance Detectors

Superconducting kinetic inductance detectors,also known as microwave kinetic inductance detectors,it with low-gap superconducting materials(such as Al,TiN,etc.)and made of a coplanar waveguide resonator with high Q value.It's detected by the change of the surface kinetic inductance of the superconducting thin film and the Q value which is caused by the incident photon breaking Cooper Pairs.Superconducting kinetic inductance detector adopts plane preparation technology and frequency division multiplexing readout method,which has obvious advantages in large-scale array integration and has become one of the most sensitive detectors in the terahertz band.In the field of astrophysics,especially in cosmic microwave background radiation detection,superconducting kinetic inductive detectors is of great value and had played an important role in some related exploration tasks.This paper starts from the terahertz astronomy,firstly introduces the development of low temperature superconducting terahertz detectors and briefly analyzes the working mechanism of MKIDs and the relative advantages of other detectors.Then,the researcher introduces the kinetic of superconducting thin films,and have a comprehensive reach about the working principle of the MKIDs by combining CPW and the characteristics of quarter-wave microwave resonators,and designs the chip of 64 pixels combined with the theory.Then,the fabrication process of the superconducting thin film of 64 pixel chip is explained in detail,including UV lithography,evaporation coating,exposure controling and so on.The resistance and resistivity of the films were measured by the square resistance meter,and the grain size,crystallinity and crystal orientation of the films were analyzed by X ray diffraction(XRD).The installation and fixation of the chip are completed by automatic ultrasonic welding instrument.Finally,the chip is installed in the vacuum Dewar,using the adsorption chiller and dilution refrigerator to create a millikelvin temperature environment,measuring its transmission coefficient in the vector network,and analysis the influence on the resonant characteristics of different temperature?different input power and different target out of Dewar window.And the good chip with design frequency is obtained,its Q value is as high as 104.This paper has the following characteristics: 1)the microstructure and film quality of the chip are analyzed by XRD,which can provide the material for the optimization of the coating process parameters and the improvement of detector performance.2)the actual Q value varies with the resonant frequency and temperature.The coupling factors of the design are compared with the theoretical values to find out the differences and analyze the reasons.3)the deflection curve of the measured resonant frequency with temperature is given and compared with the measured values by the Mattis-Bardeen theory.