Characteristics of InAs/InGaAsP quantum dot laser diodes lasing at 1.55um

We have measured I-V, L-I curves and electroluminescence spectra from InAs/InGaAsP quantum dot (QD) laser diodes (LDs) to investigate how to optimize QD LDs for high output power. The slope of an L-I curve, which is proportional to the differential quantum efficiency, decreased rapidly after lasing due to heat in cw mode. Since the heat problem is not significant in pulse mode, the efficiency is constant up to a rather high current level. In spite of the heat problem, the maximum output power is over 79 mW from a single facet in cw mode at 20 °C. At the same temperature, the lowest threshold current is 132 mA with cavity length, width and QD layers of 500 um, 5 um and 7 stacks, respectively. The characteristic temperatures of QD LD are 188 K and 111 K under pulse and cw mode, respectively. Typical lasing wavelength is around 1.55 um. The slope efficiency, internal loss and gain are 0.368 W/A, 5.2 cm-1 and 15 cm-1, respectively.