Gain margin analysis of distributed feedback lasers for both transverse electric and magnetic modes

A theoretical analysis of the gain margin with both transverse electric (TE) and transverse magnetic (TM) modes in distributed feedback (DFB) lasers of second-order gratings and various structural parameters is presented. Though the dominant mode is usually a TE mode, one of the TM modes often becomes the secondary mode with the second lowest threshold and seriously affects the single-mode characteristics of DFB lasers. To design DFB lasers with a large gain margin, proper amounts of facet reflectivity for both polarizations and control of the spatial phase of the grating at the facet are required.<
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