LASER GENERATION OF HIGH-AMPLITUDE STRESS WAVES IN MATERIALS

Stress-wave environments generated at a confined surface by a pulsed laser were investigated. Experimental measurements and theoretical calculations demonstrated that confinement of the surface with a transparent overlay provided an effective method of generating high-amplitude laser-induced stress waves in the target material. Peak pressures aproaching 10 GPa were possible at laser power densities of several times 109 W/cm2 for laser pulse durations ranging from several nanoseconds to several tens of nanoseconds. These pressures were generated in an air environment at standard conditions, thus enhancing their practical utilization for processing of materials and measurments of material properties. At laser power densities greater than 109 W/cm2, the laser-induced stress-wave environment was controlled by properties of the ionized plasma created near the metal surface. Some enhancement in the amplitude and duration of laser-induced stress-wave environments was observed at laser power densities less than 109 W/cm2 if low thermal conductivity and low heat of vaporization materials were used. Calculations show that peak pressures greater than 10 GPa were possible by superimposing stress waves either through reflection off a high acoustic impedance barrier or through the interaction of stress waves which were generated at different surfaces of a material.