Characteristics of chaos synchronization in two separate Nd:YVO4 microchip lasers

Synchronization of chaos has recently attracted great interest because of its potential for application in secure communications. Recently, optical encryption systems using laser chaos were experimentally demonstrated. It is more difficult to realize synchronization of chaos in two separate chaotic lasers because both systems possess positive Lyapunov exponents, which is different from Pecora and Carroll´s synchronization scheme (1990). We experimentally demonstrate synchronization of chaos in a master-slave system with two separate diode-pumped Nd:YVO₄ microchip lasers. Achievement of synchronization of chaos is highly dependent on the injection locking performance of the slave oscillator. The two laser frequencies are adjusted by temperature control of the microchip crystals so that their laser-oscillation frequencies are within the injection-locking range. Consequently, the frequency of the slave laser is pulled to that of the master laser, and then the two laser frequencies are perfectly matched