Microprobe photoluminescence assessment of the wall-plug efficiency in interband cascade lasers

We employ a microprobe photoluminescence (PL) technique to determine the thermal resistance and wall-plug efficiency of narrow-ridge interband cascade lasers emitting at 3.8 mu m. Using two different semiconductor epilayers as integrated thermometers, the local lattice temperature is extracted from the PL spectra and the wall-plug efficiency (eta(w)) derived from the slope of the temperature increase versus electrical power. The maximum (eta(w)) at 78 K is found to be 8.1 +/- 0.5%, and a fit to the lattice temperature gradient implies cross-plane thermal conductivities of 4.5-6.5 W/m K for the short-period InAs/AlSb superlattice cladding and of approximate to 1.5-4 W/m K for the active region. (C) 2008 American Institute of Physics.