The linewidth enhancement factor (LEF) and nonlinear gain coefficient of an InAs/AlGaInAs quantum dot (QD) laser
are measured using an injection locking technique. The nonlinear gain coefficient was found by curve-fitting the
measured LEF as a linear function of the output power. The LEF of the InAs/AlGaInAs quantum dot laser was
measured to be 1.2 to 8.6 at output powers from 2 to 10.2 mW, leading to a corresponding nonlinear gain coefficient of
1.4 x 10<sup>-14 </sup>cm<sup>3</sup>. This value for the nonlinear gain coefficient is three orders of magnitude higher than the typical
quantum well nonlinear gain coefficient of 10<sup>-17</sup> cm<sup>3</sup>. Consequently we expect that the dynamics under optical injection
and external feedback of this type of quantum dot laser will be dramatically different than in quantum well lasers,
suggesting that a careful re-examination of the dynamics of this type of laser is needed.