Random amplification of coherent light in diffusive random lasers

Random lasing is a phenomenon in which light amplification is favoured by a disordered environment[1]. A vast body of research exists that endorses the exciting physics seen in such media[2-4]. Hitherto, however, these systems have always been studied in the self-amplification mode where the spontaneous fluorescence of the medium is amplified. In this paper, we experimentally demonstrate the amplification of an external coherent signal by a random amplifying system. This is the first such demonstration, which has potential applications in optical amplifiers, frequency control of random lasers[5,6] etc.