Multimode Lasing Characteristics of Quantum Dot Lasers due to Inhomogeneously Broadened Gain

The growth condition for In(Ga)As/InGaAsP/InP quantum dots (QDs) has been optimized and room temperature lasing has been obtained from QD laser diodes (LDs) emitting at 1.55 m. However, it is observed that many new lasing modes keep appearing at longer wavelength with increase in injection current, and the output power of the new modes at longer wavelength gets much stronger than that of the mode that started to lase rst. This behavior is explained as having been caused both by an inhomogeneously broadened gain of QD LDs where the gains at di erent wavelengths keep increasing even though the gain of the primary mode is clamped at the threshold value and by a Gaussian-like distribution of the magnitudes of density of states due to a statistical distribution of the sizes of the grown QDs.