Superconducting Structures for Study and Phase Synchronization of Integrated Terahertz Oscillators

Superconducting integrated circuits based on high-quality Nb–AlOx–Nb and Nb–AlN–NbN tunnel junctions, including a harmonic mixer with a high harmonic number, have been developed, optimized, and investigated. Details of the design, manufacturing methods, and specificities of operation of superconducting elements and circuits for the detection and study of terahertz radiation from cryogenic integrated oscillators are presented. The signal of an integral terahertz oscillator was detected, its power was estimated, and the radiation spectrum was measured with a resolution of about 1 Hz. The synchronization of a superconducting oscillator at any frequency in the range 250–750 GHz with a spectral quality higher than 50% has been realized, and the phase noise of the generator in the PLL mode has been measured.