  We present an optical technique based on ultrafast photoacoustics to
precisely determine the local temperature distribution profile in liquid
samples in contact with a laser heated optical transducer. This ultrafast
pump-probe experiment uses time-domain Brillouin scattering (TDBS) to locally
determine the light scattering frequency shift. As the temperature influences
the Brillouin scattering frequency, the TDBS signal probes the local
laser-induced temperature distribution in the liquid. We demonstrate the
relevance and the sensitivity of this technique for the measurement of the
absolute laser-induced temperature gradient of a glass forming liquid
prototype, glycerol, at different laser pump powers - i.e. different steady
state background temperatures. Complementarily, our experiments illustrate how
this TDBS technique can be applied to measure thermal diffusion in complex
multilayer systems in contact to a surrounding liquid.
