S. Hansmann et al., THEORETICAL AND EXPERIMENTAL-STUDY OF INHOMOGENEOUSLY PUMPED DISTRIBUTED-FEEDBACK LASERS, Journal of applied physics, 73(11), 1993, pp. 7138-7144
We have investigated inhomogeneously pumped index-coupled distributed
feedback (DFB) laser structures both theoretically and experimentally.
Using a transfer matrix method, an optimized device structure was des
igned which drastically suppresses the longitudinal sidemodes by conce
ntrating the injection current in the region close to the phase-shift
position. In this way, a high yield of monomode lasers together with a
n easy fabrication technique was achieved without the necessity of end
facet antireflection coating. Experimental evidence of the improvemen
t of the single-mode stability is given first by three-section DFB las
ers operated by two different injection currents. Second, the proposed
three-segment laser pumped with a single drive current was implemente
d simply by splitting up the contact of a mushroom type 2 X lambda/8 p
hase-shifted DFB laser. We observed the theoretically predicted enhanc
ed stability of the Bragg mode with a sidemode suppression ratio of 52
dB and a higher yield of monomode lasers compared with uniformly pump
ed conventional DFB laser devices.