Linewidth enhancement in distributed-feedback semiconductor lasers

It is demonstrated that the linewidth enhancement in distributed-feedback (DFB) laser diodes can differ significantly from (1 + α2), where a is Henry's linewidth enhancement factor. The influence of the relevant laser parameters, the detuning of the gain peak wavelength, a π/2 phase shift and a reflecting end facet on the linewidth enhancement is discussed with respect to an improved DFB laser design.