Determination of nonlinear gain coefficient of semiconductor lasers from above threshold spontaneous emission measurement

The measurement of spontaneous emission power above threshold has shown a nearly linear increase with biasing current in a 1.55-μm InGaAs/InGaAlAs multiple quantum-well laser. Based on this measurement, we propose a novel experimental method to determine the nonlinear gain coefficient. The obtained value is 1.2×10/sup -17/ cm
³
for the laser used. This value corresponds reasonably to that obtained by chirp-to-modulated-power ratio method, confirming the validity of this new measurement method.