Abstract

In the last decade a strong interest is shown in the optimization of the quantum cascade lasers and in particular on the improvement of their power efficiency. In QCLs, one of the key parameters that influence performance is the quality of the interfaces between the epitaxial layers. A quantitative model that assumed interfaces with steps with an Gaussian distribution (<h(r)h(r')>=Δ²exp(-|r-r'|²/Λ²)) characterized by an average step height Δ and a correlation length Λ was shown to correctly predict the temperature dependence of the intersubband broadening[1]. Early studies have focused on the prediction and minimization of the intersubband broadening parameter[2]. However recent works have shown that some devices exhibiting wide gain bandwidth exhibited at the same time record wallplug efficiencies, as shown by[3,4]. In fact the influence of interface roughness(IFR) on laser performance is complex since it does not only influence the broadening but also the intersubband lifetime. Trying to explore experimentally this dependence, the performances of strain-balanced quantum cascade lasers were investigated as a function of the substrate temperature during epitaxial growth. The structure design used for this work was already presented elsewhere[5].

© 2011 Optical Society of America