We investigate the angular distribution and average kinetic energy of ions produced during ultrafast laser ablation (ULA) of a copper target in high vacuum. Laser produced plasma (LPP) is induced by irradiating the target with Ti:Sapphire laser pulses of ~50 fs and 800 nm at an angle of incidence of 45o. An ion probe is moved along a circular path around the ablation spot, thereby allowing characterization of the time-of-flight (TOF) of ions at different angles relative to the normal target. The angular distribution of the ion flux is well-described by an adiabatic and isentropic expansion model of a plume produced by solid-target laser ablation (LA). The angular width of the ion flux becomes narrower with increasing laser fluence. Moreover, the ion average kinetic energy is forward-peaked and shows a stronger dependence on the laser pulse fluence than on the ion flux. Such results can be ascribed to space charge effects that occur during the early stages of LPP formation.
© 2013 Chinese Optics Letters
(320.2250) Ultrafast optics : Femtosecond phenomena
(320.7120) Ultrafast optics : Ultrafast phenomena
(350.5400) Other areas of optics : Plasmas
(320.7085) Ultrafast optics : Ultrafast information processing
Xiaochang Ni, Anoop K.K., Mario Bianco, Salvatore Amoruso, Xuan Wang, Tong Li, Minglie Hu, and Zhenming Song, "Ion dynamics in ultrafast laser ablation of copper target," Chin. Opt. Lett. 11, 093201- (2013)