Synchronization of coupled semiconductor lasers

Abstract

The dynamics of two mutually coupled semiconductor lasers is studied experimentally and numerically for weak coupling. The two lasers are pumped at different levels and have dissimilar free-running relaxation oscillation frequencies and intensities. We have found that the two lasers exhibit large amplitude intensity oscillations for one laser and small amplitude intensity oscillations for the other laser. In our previous work, we studied the effect of the coupling strength. In this paper, we keep the coupling strength fixed and examine the effect of the detuning between the optical frequencies. As the detuning comes close to a multiple of the relaxation oscillation frequency of one of the two lasers, we observe the amplification of the intensities due to resonance and synchronization. Our experimental observations of the laser spectra are in good agreement with the numerical spectra and bifurcation diagrams computed from the semiconductor laser rate equations.