ENHANCED JOSEPHSON RADIATION AND LINEWIDTH-NARROWING SUPERCONDUCTING MICROBRIDGES IN A RESONANT CAVITY.

Josephson radiation emitted from superconducting microbridges and coupled two-bridge junctions has been investigated at microwave frequencies. The radiation linewidth DELTA f and total radiation power P are found to vary with the output coupling controlled by a tuning stub in the cavity, indicating feedback-induced effects due to the radiation fields. We have found ( DELTA f)//m//i//n approximately equals 900 kHz, P//m//a//x similar 0. 9 x 10** minus **1**2 W for the single microbridge and ( DELTA f) //m//i//n similar 60 kHz, P//m//a//x similar 5 x 10** minus **1**2 W for the coupled bridges. The enhancement of radiated power and line-narrowing in the coupled bridges are attributed to coherent behavior of the junctions.