Description
Semiconductor lasers are compact, efficient light sources widely used in optical communications, and their sensitivity to external feedback also makes them rich systems for studying nonlinear dynamics. The Lang–Kobayashi (LK) equations remain the standard framework for modelling feedback from a regular mirror, but many modern systems employ fibre Bragg gratings (FBGs) for their precise spectral control and all-fibre integration. FBG feedback enables narrow-linewidth, wavelength-stable emission essential for exciting rare-earth-doped gain media such as erbium and ytterbium, and for maintaining spectral purity in high-resolution sensing and coherent communication systems.
When the external feedback comes from an FBG, present modelling requires a computationally expensive convolution term, which provides limited analytical insight into the system's behaviour. We present a novel modelling approach that approximates FBG feedback by a sum of discrete delay terms. Critically, this avoids the need for numerical convolution while preserving the essential physics. This approach enables detailed analysis of the laser's mode structure, stability regimes, and bifurcations in the spirit of that for the ‘classic’ LK equations. The model reproduces the characteristic stability windows that appear when FBG reflection zeros coincide with the laser’s intrinsic frequencies and captures the transition between steady, periodic, and chaotic regimes. In this way, our work provides a foundation for deeper theoretical study of semiconductor lasers subject to technologically relevant types of FBG feedback, bridging the gap between numerical simulation and analytical understanding.
| I am the presenting author | Yes |
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