  In this work we present results of the analysis of thermal properties of
high-power laser bars obtained by spatially resolved thermoreflectance (TR)
spectroscopy. Thermoreflectance is a modulation technique relying on periodic
facet temperature modulation induced by pulsed current supply of the laser. The
periodic temperature change of the laser induces variation of the refractive
index and consequently modulates probe beam reflectivity. The technique has a
spatial resolution of about ~1 $\mu$m and can be used for temperature mapping
over 300 $\mu$m x 300 $\mu$m area. Information obtained in these experiments
provide an insight into thermal processes occurring at devices' facets and
consequently lead to increased reliability and substantially longer lifetimes
of such structures.
