Absorption of pulsed laser radiation by composites based on hexogen and aluminium nanoparticles

Absorption of the second-harmonic radiation from a pulsed YAG : Nd³⁺ laser by composites based on hexogen and aluminium nanoparticles (of a diameter 100 nm) is theoretically and experimentally investigated. The absorption efficiency factor (the ratio of the light absorption cross section to the geometrical cross section) is calculated by using the Mie theory for Al inclusions in a hexogen medium for various particle diameters and wavelengths corresponding to laser fundamental and second-harmonic radiation. Dependences of the absorption coefficient and amplitude of an acoustic signal on the concentration of inclusions under laser irradiation of composite samples are measured by using a piezo-acoustic transducer. It is shown that the radiation is directly absorbed by nanoparticles. The optimal concentration is found, which provides the maximal signal of the piezo-acoustic transducer.