Generalized synchronization of chaos in He-Ne lasers.

We experimentally demonstrate synchronization of chaos in one-way coupled He-Ne lasers with optical feedback. We observe different types of synchronization such as identical synchronization, inverse synchronization, and random amplification. These dynamics are maintained only for a short duration of several hundred milliseconds. We also observe generalized synchronization of chaos by using one master and two slave lasers. The generalized synchronization is achieved for a long duration of tens of seconds under injection locking. The generalized synchronization is always maintained while the injection locking is achieved.