Phase locking of 270-440 GHz Josephson flux flow oscillators

Abstract

External phase locking of a Josephson flux flow oscillator (FFO) to a 10 MHz reference oscillator is demonstrated experimentally in the frequency range 270-440 GHz. A linewidth as low as 1 Hz (as determined by the resolution bandwidth of the spectrum analyser) has been measured. This linewidth is far below the fundamental level given by shot and thermal noise of the free-running tunnel junction. The combination of narrow linewidth, wide band tunability and low noise is important for spectral radio astronomy applications.