SPECTRAL CHARACTERISTICS OF DISTRIBUTED-FEEDBACK LASER-DIODES WITH DISTRIBUTED COUPLING COEFFICIENT

A comprehensive investigation of the spectral characteristics of distributed feedback (DFB) laser diodes (LD's) with a distributed coupling coefficient (DCC) is presented, With a proper selection of both the coupling ratio (tau) and a corrugation position (CP), the performance of the DCC laser structure is enhanced with an improved single-mode stability as well as a uniform field distribution. In the analysis, the above threshold characteristics and the influence of non-lasing side modes have been investigated using the transfer matrix method (TMM). Based on a DCC laser structure with tau = 1/3 and CP = 0.46, a normalized gain margin (Delta alpha L) = 0.81 and a side mode suppression ratio (SMSR) of 45 dB have been achieved for a DCC LD at biasing current of 4I(th). The introduction of the DCC laser structure opens a new way of stabilizing the single-mode oscillation in DFB LD's.