Time-resolved measurement of the local lattice temperature in terahertz quantum cascade lasers

We measured the time dependence of the local lattice temperature in terahertz quantum cascade lasers with surface plasmon waveguides. The time constants for heat extraction from the active region (0.15-0.29 μs) are approximately ten times shorter than those associated with heat extraction from the substrate, thereby showing the dominant role of the substrate-heat sink coupling. Thermal diffusivities D=0.052 cm2 s (Ds =3.9 cm2 s) and thermal diffusion lengths μ=1.2 μm (μs =31 μm) in the active region (substrate) have been extracted by fitting the solution of the heat transport equation to the experimental data