Experimental and theoretical evaluation of the CW suppression of TE side modes in conventional 1.55 mu m InP-InGaAsP distributed feedback lasers

Abstract

A study is made of the factors that influence the suppression of the second TE Bragg mode in conventional 1.55 mu m capped-mesa-buried-heterostructure distributed-feedback (CMBH-DFB) lasers. It is shown that the TE side-mode suppression becomes increasingly worse as the coupling of the optical mode to the grating (kL) becomes larger, as expected from theoretical predictions. This degradation is not correlated to changes in the measured threshold gain margin, as obtained from spectral resonances. To explain the results, the authors introduce a new parameter-the threshold bias margin-which is a measure of the threshold difference between the lasing mode and the most prominent side mode.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>