Onset of optical emission in femtosecond laser-induced plasmas and its correlation with surface dynamics monitored by pump–probe time-resolved microscopy

Abstract

Femtosecond time-resolved images acquired by using a two-color pump–probe microscope have been used in combination with optical emission spectroscopy to determine the time scales for the onset of atomic and molecular emission in laser-induced plasmas. A time-slicing acquisition scheme has been used to follow the build-up of emission lines in the spectra. Microscopy images suggest that the ejection of material from silicon starts several nanoseconds before photon emission is detected in our system. The time elapsed is material dependent and proceeds much slower in organics as demonstrated for nylon and Teflon. This finding is of great interest for time-resolved measurements in laser-induced plasmas and should be used for extracting maximum information from spectral data following femtosecond laser ablation.