Amplification of electromagnetic waves excited by a chain of propagating magnetic vortices in YBaCuO Josephson-junction arrays

Theory shows that when a soliton propagates in a discrete lattice it excites small-amplitude linear waves in its wake. In a dc current-biased Josephson-junction (JJ) array these manifest as electromagnetic (EM) waves excited by a (magnetic field induced) chain of propagating magnetic vortices. When the vortex velocity and the phase velocity of one of the excited EM waves match, phase-locking occurs. This results in the amplification of the EM radiation. We report the first observation of phase-locking-induced amplification of EM radiation at 77K and above in JJ arrays made of high temperature superconductors.