Experimental investigation of laser damage to thin metal films using a quartz resonator

An experimental investigation was made of some of the conclusions of the two-phase model of laser damage to thin absorbent films. A new investigation method was applied and this allowed accurate quantitative measurements to be made of the variation in the mass of the film on exposure to laser radiation. The thresholds q₁ and q₂ for initial and total damage to the film were measured using the experimentally determined dependence of the thickness of the evaporated layer h on the light flux density q. The theoretical dependences q_1,2(H), q_1,2(τ), and q_1,2(A) (H is the film thickness, τ is the duration of the laser pulse, and A is the reflectivity of the film) were confirmed experimentally. The experiments supported the conclusion of the two-phase model that, when the dimensions of the illuminated zone are large d≫√κτ, d≫Hw_i /v_f (d is the diameter of the illuminated zone, κ is the thermal diffusivity of the film, w_i is the velocity of the melt, and v_f is the velocity of the evaporation boundary of the film), the damage process is accurately described by the evaporation model.