| This dissertation describes results on the development and the application of Josephson junctions as submillimeter wave sources. Three subjects have been studied.; 1. Single junction coupled to a resonator. The purpose of this work is to study a simple and well defined system so that a clear and useful relation between the response of the junction and the high frequency characteristic of the resonator can be obtained. The system, consisting of a Resistively Shunted Junction and a microstrip resonator, was investigated using both numerical analysis and perturbation method. The results obtained from the simple analytical solution of the perturbation method were used to calculate the surface resistances of Nb and other materials to about 400 GHz with an accuracy of better than 30%.; 2. Distributed Josephson junction arrays were designed. The objective was to improve the design of phase locked Josephson junction arrays. A true distributed array has been developed based on the results of computer simulation. The experimental test on the actual fabricated array, containing 20 junctions, did show good performance (produced {dollar}sim{dollar}2 {dollar}mu{dollar}W RF power to a 26 {dollar}Omega{dollar} load around 300 GHz). The design for the future high power arrays was also addressed, based on the results of this study.; 3. Radiation linewidth of a phase locked Josephson junction array was studied using computer simulation, and was measured at 250 GHz, using an integrated submillimeter wave receiver/source developed specially for this work. The purpose of the research was to investigate the coherent behavior of the distributed arrays developed and presented in this thesis. The results showed that, for a carefully designed distributed array, all the junctions in the array can oscillate coherently and in-phase, resulting in the reduction of radiation linewidth ({dollar}Deltaomega propto 1/N).{dollar} The convoluted linewidth (10 junctions in the local oscillator array, and 10 junctions in the signal array) was measured to be 10 MHz at 1.6 K, with an accuracy better than 50%.; All the junctions (RSJ and SIS) used and fabricated were based on the Nb/AlO{dollar}sb{lcub}x{rcub}{dollar}/Nb technology. The detailed device fabrication process is discussed. |
