Coupling of ultrafast laser energy to coherent phonons in bismuth

Abstract

Energy coupling to coherent phonons in Bi during femtosecond laser–bismuth interaction is investigated using a double-pulse femtosecond pulse train generated from a temporal pulse shaper. It is found that the increase of bismuth temperature is dependent on the separation time between the two laser pulses. Using a numerical fitting, which considers the effect of convolution between the incident pulses and the material response, the measured temperature increases using different pulse-to-pulse separations allow quantitative determination of the amount of laser energy coupled from excited electrons to coherent phonon vibration.