Observation of additional delayed-time in chaos synchronization of uni-directionally coupled VCSELs.

Abstract

We report an experimental and numerical investigation on the existence of additional delayed-time in chaos synchronization of two uni-directionally coupled vertical-cavity surface-emitting lasers (VCSELs) for the first time. Under a generalized synchronization scenario, we demonstrate that there exists an additional delayed-time in addition to the time-of-flight between the two coupled VCSELs. The cross-correlation function analysis has been used as a method to determine the coupling delay and synchronization quality between two uni-directionally coupled chaotic VCSELs. We show that the injection strength significantly influences the additional delayed-time, and the injection strength analysis eventually substantiates the existence of additional delayed-time between the coupled lasers in experiments. The experimental results are in accordance with the numerical results. Additionally, we numerically study the effect of laser's internal parameter mismatches on additional delayed-time and synchronization quality between the lasers.