Temporal and spatial properties of plasma induced by infrared femtosecond laser pulses in air

Space and time-resolved electron density and temperature of the plasma, created in air by focused femtosecond laser pulses have been investigated as a function of the pump pulse energy and duration. For the air ionization the infrared (1030 nm) femtosecond (190–500 fs) Yb:KGW laser pulses of up to 1 mJ energy were used. Based on the Stark broadening of the oxygen-I 777.19 nm line we have found that after establishing a local equilibrium the density of laser-created plasma could exceed 10 17 cm −3 with the electron temperature of over 5000 °C. Obtained results agree well with the results of previously reported measurements of the plasma density created by the femtosecond near-infrared Ti:sapphire laser pulses.