Regular papers

Optical spectrum behaviour of a coupled laser system under chaotic synchronization conditions

National Institute for Laser, Plasma and Radiation Physics, PO Box MG 36, 077125 Magurele, Romania

^* ionut.andrei@inflpr.ro

Received: 14 December 2012
Revised: 10 June 2013
Revised: 22 July 2013

Abstract

Synchronization characteristics of two bidirectionally coupled semiconductor lasers, one operating in a chaotic regime with low-frequency fluctuations and the other with free laser beam emission, were experimentally investigated. The chaotic synchronization regimes and optical spectral behavior of the coupled system were analyzed with respect to the optical spectra emitted initially by the two uncoupled lasers operated under the same feedback conditions. It was observed that the number of synchronization regimes that can be obtained and their stability depend on the similarity of spectral structures of the uncoupled lasers emissions. The dominant active laser modes of the coupled system emission coincide with the laser modes of the one or both uncoupled laser emissions, depending on the operating synchronization regime. We have associated changes in the optical spectrum of the coupled system with the synchronization regimes. The repartition of power between the active modes of a coupled system allows identification of the synchronization regime.