REFLECTIVITY MEASUREMENTS FOR 1.06μm LASER PULSES INTERACTING WITH LY12 AIUMINIUM TARGETS

Reflectivities and spatial distributions of reflected light was measured with a multi ?chanell apparatus for 1.06μm laser pulses interacting with LY12 aluminum targets in 1 atm air. As the laser power density changed from 1.68×l0⁴ to 6.08 × 10⁴W/cm² with target surface roughness 1.6～3.2μm, the reflectivity reduced from 0.90 to 0.8 for long pulses. For 2.83 × 10⁸ W/cm² short pulses, its reflectivity was 0.78. The experiments indicated that reflectivity and thd spatial dlistribution of the reflected light was dependent on the temperature field of the targets, optical property of ablated surface and the mechanism of laser energy absorption by vapor plume.