Emission dynamics of 1.5 &mgr;m InGaAs/InGaAsP quasi‐quantum wire lasers excited by ultrashort optical pulses were investigated. Wire distributed feedback lasers with different nanometer wire widths and distances between the wires, which were realized by dry‐etching technique, were compared in detail. The dependence of dynamic behavior on wire width was observed. Detailed theoretical simulations show that, the improvement of dynamic response with decrease of wire width is attributed to a superlinear increase of differential gain with decrease of wire width, which counteracts the negative effects due to decrease of packing density of the active region and increase of electron relaxation time.