TIME-INTEGRATED REFLECTIVITY OF LASER-INDUCED BACK-ABLATED ALUMINUM THIN-FILM TARGETS

A study of the time-integrated reflectivity of Al targets during laser -induced back ablation by 1064 nm, 10 ns laser pulses is reported. The Al target reflectance data is analyzed using a model which includes n ot only Al surface removal but also the possible production of Al plas ma. Calculations based on a sharp Al film ablation fluence (J(th) appr oximate to 710 mJ/cm(2)) threshold agree with the reflectance data. Pl asma reflectance contribution is found to be negligible for plasma ele ctron densities of less than 0.3 critical density. (C) 1997 American I nstitute of Physics.