Experimental measure of dynamic spatial-hole burning in DFB lasers

Spatially resolved measurements of carrier density in two 1.3-μm distributed feedback laser diodes are reported. By measuring the response of the spontaneous emission intensity to a 50-MHz drive current, small relative changes in the carrier density can be observed. When biased below threshold, the carrier density fluctuates uniformly in the laser cavity with a phase delay corresponding to the carrier lifetime. When biased above threshold, the carrier density response shows clear evidence of spatial hole burning. The location of the minimum and the net change in carrier density, however, depend on the particular laser