Foundation of femtosecond laser pump-probe thermoreflectance system

Femtosecond laser pump-probe thermoreflectance system was founded and used to in- vestigate energy deposition and transport during the early period of ultra-short pulse laser heating of 50-nm-thick golden film.The laser pulse duration is 140 fs and the heating energy density of one pulse is only 5×10~(-3)mJ/cm~2.As the maximal electron temperature change is less than 10 K,the imprecision of measurement,caused by varying parameters with temperature,effectively reduces.The experiment results were given,and the influencing factors were discussed.