Dynamics in the Frequency of a Semiconductor Laser using Feedback from a Narrow Filter

We demonstrate that by spectrally filtering the delayed optical feedback into a semiconductor laser, one can elicit novel dynamics in the frequency of the laser output light on a time scale that is set by the delay time of the feedback. Diode lasers subject to external optical feedback have been intensely studied, both theoretically and experimentally [1-4]. From a technological point of view, it is essential to understand and control the feedback laser, since feedback occurs naturally in any application, such as back reflections from a fibre facet, and thus must be confronted and understood. From a more fundamental point of view, the feedback laser is an example of a delayed dynamical system and its understanding may contribute to furthering our knowledge of many other delayed systems, which occur frequently in nature. The laser with feedback from an external cavity is known to show a wide range of dynamics [1][3][4]. Unfortunately, there are very few and sometimes inaccessible control parameters, which dictate the dynamics and thus the resulting analysis requires pain-staking accuracy. Recently, we proposed the use of a frequency filter in the external cavity by means of which one may control many aspects of the feedback light and thus influence the feedback syste