Frequency domain analysis of the chaotic synchronization of injection-locked semiconductor lasers

Abstract

The quality and degree of synchronization obtained between a chaotic master laser diode and a slave laser diode is usually assessed using a correlogram. This technique is known to accurately identify areas of good synchronization, but it is not able to elucidate why these regions exist. By using a complementary frequency domain technique, the response gain, we have been able to obtain further insight into the synchronization process. We show using numerical simulations that trends in synchronization quality evident in the injection-locking diagram are also present in the response gain. We also show that most of the spectral power is situated in a small band of frequencies close to the relaxation oscillation frequency of the master laser and that accurate reproduction of these frequency components in the slave laser is vital in achieving a good synchronization. We associate the variation in synchronization quality within the injection-locking regime to changes in the response gain profile induced by the optical injection from the master laser. Variations in the spectral profile of the response gain clearly delineate and explain the various regions seen in the correlation synchronization diagram.