Facet temperature mapping of GaAs/AlGaAs quantum cascade lasers by photoluminescence microprobe

The measurement of thermal resistance and facet temperature profile of oper ating GaAs/AlGaAs quantum cascade lasers (QCLs) as a function of injected c urrent, repetition rate and pulse width is reported. The use of microprobe band-to-band photoluminescence (PL) spectroscopy allows to achieve a spatia l resolution <1 mum. Substrate-side and epilayer-side mounted devices with identical laser structures were investigated. At T = 80 K, the thermal resi stance of epilayer-side mounted devices (7.8 K/W) is similar to 30% lower t han that of substrate-side mounted devices, thus explaining the better perf ormance of the former. The outcome of a two-dimensional model of heat propa gation in our structures is compared with the experimental data. (C) 2001 E lsevier Science B.V. All rights reserved.