Above-threshold analysis in an optimized three phase-shift DFB laser structure for stable single-mode operation

By an improved optimization of the grating profile, an asymmetric three phase-shift (3PS) distributed feedback (DFB) laser structure is shown to achieve stable single mode oscillation up to high current injection levels. The analysis of those structures enhances the possibility of attaining high mode selectivity whilst ensuring almost flat profiles for the intracavity field distribution. The transfer matrix-method has been applied to evaluate the above-threshold performance of the asymmetric 3PS-DFB laser, namely the mode selectivity and the flatness versus biasing current. Outstanding improvements have been shown in comparison with the quarterly-wavelength-shifted DBF structure or with other similar but symmetric DFB structures referred in literature.