Attenuation of laser radiation by particles during laser materials processing

The extinction, absorption and scattering of laser radiation by small aerosol particles of Fe, Fe3O4, Al, and Al2O3 have been calculated using Mie theory at wavelengths of 1.06 and 10.6 μm. It is shown that the attenuation of incident laser radiation by particles with radii r in the range 10 nm ⩽ r ⩽ 10 μm can be significant over pathlengths as small as 10−2 m when the ratio of aerosol mass density to solid density, M/ρ ≳ 10−4. Under certain conditions highly directed scattering of laser radiation can occur. Some implications of these results with regard to processing of materials with laser radiation are discussed.