Josephson cascade micromaser.

Abstract

The possibility of maser action using a current-biased {ital mesoscopic} Josephson junction in a high-{ital Q} {ital microcavity} is discussed. A mesoscopic Josephson junction behaves like an artificial atom as far as the interaction with the photon field is concerned. Under a certain bias current, the Josephson {open_quote}{open_quote}atom{close_quote}{close_quote} is resonantly excited or pumped by quantum-mechanical fluctuations of the Josephson phase, i.e., macroscopic resonant tunneling. When the pumping overcomes the loss of photons from the cavity, maser action is possible. Quantum statistical properties of photons are also investigated numerically, taking into acount the microcavity effect on the basis of a Jaynes-Cummings model with pumping and cavity damping. We found that a mesoscopic Josephson junction within the high-{ital Q} microcavity acts as a thresholdless maser with sub-Poissonian photon statstics. {copyright} {ital 1996 The American Physical Society.}