Cross-plane thermal diffusivity measurement of an operating vertical cavity surface emitting laser using thermoreflectance

Abstract

Cross-plane thermal diffusivity of a GaAs/AlGaAs-based vertical cavity surface emitting laser (VCSEL) is measured under operating conditions and active heat sinking using a thermoreflectance technique. Perpendicular thermal diffusivity is determined from the measurements of phase difference between the heating source and the temperature as a function of temperature modulation frequency. The value of (1.22 ± 0.23) × 10-6 m2/s is obtained for thermal diffusivity, which is of the same order as previous values obtained on unbiased VCSEL structures. This is 10−14 times smaller than the corresponding bulk value. The reduction is attributed to the increase in phonon-boundary scattering in the multilayer structure of the VCSEL.