Semiconductor lasers subject to optical feedback are of both scientific and technological importance. The laser and external mirror form a compound cavity which can be modeled using a coupled cavity approach. Using this approach we have calculated the longitudinal mode frequencies and the associated mode lifetimes of all the modes in the system. We have found that for a narrow range of external cavity reflectivities, the mode lifetimes become almost degenerate. In this regime the mode lifetimes become highly sensitive to variations in the refractive index of the laser and external cavity reflectivities. Close inspection of this regime has revealed ever finer detail, suggesting a fractal structure to the mode solutions. The calculations have been undertaken in the 'cold cavity' limit and indicate a catastrophic loss of mode discrimination, even in a system with no inherent material gain. In the short cavity limit the external reflectivity required to induce the loss of mode discrimination varies as a function of external cavity round-trip time.
Synchronized external-cavity diode lasers are used for chaotic optical communication. A 1 GHz message is encoded by current modulation of the chaotic transmitter laser and decoded by a synchronzied chaotic receiver laser diode. The effect of introducing the message by optical injection into the receiver laser instead of direct current modulation is then investigated. Finally, we show how the signal masking can be enhacned by the appropriate choice of external cavity length for a given message frequency.
This paper presents an overview of work undertaken and directed at the utilization of chaotic laser diodes in secure optical communications systems. Particular emphasis will be given to experimental work using external cavity laser diodes.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.