The effects of delayed filtered optical feedback on diode laser dynamics
This research investigates the effects of filtered optical feedback on the nonlinear dynamics of a diode laser. Dynamics due to optical feedback have traditionally been considered unwanted phenomena in diode lasers, and hence something to be avoided. In recent years, it has become apparent that some of these dynamics can be useful for certain applications. The principal focus of this research is to develop and investigate a novel mechanism for controlling these dynamics via parameters that are external to the laser system. It is shown that there are three regimes of interest for filtered optical feedback based on the filter bandwidth relative to laser parameters (relaxation oscillation frequency and external cavity mode spacing). The dynamical response of the laser is quite different in each of the three regimes. The moderate and narrow filter cases reduce the influence of relaxation oscillations. In the moderate filter case, one can elicit novel dynamics in the frequency of the laser output. First, oscillations are produced on a time scale set by the feedback delay time. Second, there is a period doubling route to chaos in frequency which is also based on the round trip delay time. It is also shown that filtered optical feedback eliminates low frequency fluctuations. Soliton-like pulses in a three level system are also considered. Although the problem does not involve filtered optical feedback, it considers issues of time delay and ultimately has applications in communications and spectroscopy as does filtered optical feedback.
Vemuri, Purdue University.
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