Investigation of spatial beam profiles of a femtosecond Ti:sapphire laser amplifier

With a homemade laser beam profile measurement system, the characteristics of the spatial beam profile of 40 GW amplified femtosecond laser pulses have been studied. It is found that the laser beam profile has better quality at lower pump current, and the beam quality decreases as the pump current increases. In particular, the light intensity at the central area of the femtosecond laser beam may actually become weaker at high current than that at the low current. It is also found that within the multipass amplification process the beam quality of the pump laser has a great impact on the spatial beam profile of the femtosecond laser pulses.