Experimental study of time-delay signature of chaos in mutually coupled vertical-cavity surface-emitting lasers subject to polarization optical injection

Time-delay signature of chaos in mutually coupled vertical-cavity surface-emitting lasers subject to polarization rotated optical injection has been investigated experimentally. Autocorrelation function and permutation entropy are used to quantitatively identify the time-delay signature of chaos. The experiment results show that the time-delay signature is sensitive to the polarization rotated angle. Minimum time-delay signature has been observed in the intermediate polarization rotated angle for the lower bias current. This is in good agreement with the theoretical prediction. At higher bias currents, the lower time-delay signature has been obtained with parallel optical injection.