Temperature dependence of the lasing wavelength of InGaAs quantum dot lasers

We observe that the emission wavelength of edge-emitting InGaAs quantum dot lasers has a much weaker temperature dependence (0.6 Angstrom K-1) than eq uivalent quantum well devices (3 Angstrom K-1). Measured gain and absorptio n spectra show that the gain peak wavelength due to dot states is almost in dependent of temperature for a given value of peak gain whereas the absorpt ion edge shifts at a rate of about 2 Angstrom K-1. Above 100 K the occupanc y of dot states can be described by Fermi functions and on this basis we fi nd that the measured gain and absorption spectra are in excellent quantitat ive agreement. Although the band edge energy reduces with increasing temper ature, this analysis shows that the energy distribution of dot states match es the evolution of the Fermi functions such as to leave the quasi Fermi le vel separation and the wavelength of the gain peak unchanged as a function of temperature for a given value of peak gain. This energy distribution is a consequence of the dot size distribution so the match to the Fermi functi ons is probably fortuitous. (C) 2001 American Institute of Physics.