We study a semiconductor laser subject to filtered optical feedback from two separate filters. This work is motivated by an application where two fiber gratings are used to stabilize the output of a laser source. Specifically, we consider the structure of the external filtered modes (EFMs), which are the basic cw-states of the system. The system is modelled by a set of four delay differential equations with two delays that are due to the travel times of the light in each of the external cavities. Here, each filter is approximated by a Lorentzian and we assume that there is no interaction between the two filters. We derive a transcendental equation for the EFMs as a function of the widths, detunings and the feedback strengths of the two filters. With continuation techniques we investigate how the number of EFMs changes with parameters. In particular, we consider the equation for its envelope. This allows us to determine regions in the plane of the two detunings that correspond to one, two or three EFM components - disjoint closed curves that are traced out by the EFMs as a function of the feedback phase.
Translated title of the contribution | Mode structure of a semiconductor laser with feedback from two external filters |
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Original language | English |
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Title of host publication | SPIE 2008 |
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Publication status | Published - Feb 2008 |
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Conference Organiser: GWR and Bookham Technology Ltd