Linear chirping effects on heating of silicon surface after interaction with femtosecond laser pulses

Abstract In this paper, the interaction of the ultra-short chirped laser pulses with silicon has been studied. Chirping effect changes the instantaneous frequency of the ultra-short laser pulses. For correct simulation, the absorption spectrum of the silicon is used instead of constant absorption value. Heating and laser absorption has been investigated using the finite difference method for solving equations of the two-temperature model. The time evolution of the carriers number density is also determined by coupling an additional equation with the two-temperature equations. The number density, carriers temperature, and lattice temperature at different times are compared for up, down, and un-chirped laser pulses. It is shown that by applying an up-chirped or down-chirped laser pulses, the laser absorption by the silicon is increased relative to the un-chirped laser pulse. It is also revealed that by using a linearly chirped laser pulse the carriers and lattice maximum temperature will increase. Results indicate that due to the effective acceleration by ponderomotive force, the laser absorption for down-chirped laser pulse is more efficient than up-chirped laser pulse.