Noise in the ac Josephson Effect

A Langevin treatment of noise in the ac Josephson effect is given at finite temperatures, including the quasiparticle tunneling currents. Using quasilinear methods, the stability and small oscillations of the system are investigated. It is found that the system is unstable for phase fluctuations and that these phase fluctuations lead to a Lorentzian line for the radiation emitted from a Josephson junction. The power spectrum of voltage fluctuations of the junction and the statistics of the emitted radiation are investigated.