Temperature dependence of emission intensity in femtosecond laser-induced Ge plasma
Femtosecond laser-induced breakdown spectroscopy (LIBS) of Ge at different initial sample temperatures is investigated. The spectral intensity of the Ge(I) 422.66 nm line is shown to decrease with increasing temperature. And, higher spectral emission intensity with an 800 nm laser wavelength is observed in comparison to a 400 nm laser wavelength. In order to understand this result, the transient relative reflectivity of a semiconductor Ge sample at different temperatures is measured by an ultrafast time-resolved pump-probe experiment. It is found that the change in the transient reflectivity of Ge at higher temperature is less than that at lower temperature, which may be the main reason for the decrease of spectral emission intensity.