Abstract

It is well-known that λ/4-shifted DFB lasers with uniform gratings are capable of oscillating at the Bragg frequency with high side mode suppression. The longitudinal intensity profile can be highly non-uniform, however, and above threshold spatial holeburning (SHE) will lead to a reduced side mode suppression and an increase of the linewidth-power product. ¹ To compensate this effect non-uniform current injection has been applied,² and the use of more sophisticated gratings that can lead to a uniform intensity distribution has been suggested.^3,4 In this paper we argue on the basis of numerical calculations that the primary condition tor having a narrow linewidth is to minimize the variation of the Bragg frequency along the cavity and to maintain oscillation near the center of the slop band.

© 1991 Optical Society of America