Spatial-mode analysis in broad-area semiconductor lasers subjected to optical feedback

Broad-area semiconductor lasers are unstable light sources even in solitary oscillation owing to the spatial dependence of laser emission along the stripe width. One of the instabilities that occur in the dynamics of broad-area semiconductor lasers is filamentation. Laser oscillations are further affected by optical feedback. In the presence of optical feedback, higher spatial modes related to the filamentations are either excited or suppressed depending on the feedback conditions. As a result, the beam shape of the time-averaged pattern is greatly affected by optical feedback. In this study, we perform the decomposition of spatial-mode components for time-averaged near-field patterns in the presence of optical feedback. A method of simulated annealing (SA) is employed for the decomposition. The beam profiles are well reconstructed by the SA method. A quantitative discussion of the excitation or suppression of higher spatial modes in relation to the optical feedback conditions is given.