This thesis theoretically and experimentally investigates issues relevant to the use of semiconductor lasers for optical chaotic communication systems. The motivation for using chaos in communications is to obtain secure/private communication systems by exploiting the complex and unpredictable behaviour of chaotic systems.
The modulation properties of a semiconductor laser, an important consideration for any optical communication system, including chaotic communication systems are studied. Injection locking of a multi mode semiconductor laser is studied as a way for enhancing the modulation properties.
A new proposal for chaotic transmitters and receivers in a chaotic communication system is presented. It is shown theoretically that chaotic dynamics can be obtained in a compact disc (CD) semiconductor laser under direct modulation of the laser drive current. Having obtained chaotic dynamics in a CD laser, attention is then given to the synchronisation of two chaotic CD lasers. An experimental investigation of the security of a chaotic communication system based on external cavity semiconductor lasers is performed, where an attempt is made by an eavesdropper to intercept and decode a chaotically encrypted message. The dynamics of short external cavity semiconductor lasers are studied with emphasis given to the effect that sub-wavelength changes in the external cavity length have on the temporal and spectral output behaviour. The control of chaos in a semiconductor laser via optical injection from a secondary semiconductor laser is studied. Chaos control techniques have an important role to play in the engineering of immunity of semiconductor lasers to feedback effects.