Spectral characteristics of distributed feedback laser diodes with distributed coupling coefficient

A comprehensive investigation of the spectral characteristics of distributed feedback (DPB) laser diodes (LD's) with a distributed coupling coefficient (DCC) is presented. With a proper selection of both the coupling ratio (r) 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 r=1/3 and CP=0.46, a normalized gain margin (/spl Delta//spl 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/sub th/. The introduction of the DCC laser structure opens a new way of stabilizing the single-mode oscillation in DFB LD's.>