Phase synchronization of chaotic lasers

We experimentally investigate phase synchronization between two electronically coupled diode laser pumped Nd:YAG lasers. As the coupling strength increases, the phase of the two chaotic laser outputs develops from a nonsynchronous state to a phase synchronous one through a phase jump state. We find that there are 2 pi phase jumps and a pi/2 phase shift between the two laser outputs unlike in optically coupled Nd: YAG lasers. To clarify the transition to phase synchronization with a pi/2 phase shift, we analyze the phenomenon of phase synchronization by using a phase portrait, phase difference dynamics, and frequency variation depending on the coupling strength and obtain the scaling rule of the average phase locking time in the intermittent phase jump state. (c) 2006 Optical Society of America.