As one can easily ascertain by simple estimates, a nanosecond-scale laser pulse can overheat the thin surface layer of a light-absorbing material to a temperature of thousands Kelvins. Thermal emission of this laser-heated surface (laserinduced incandescence, LII) is easily observed in the visible spectral range by a photomultiplier. The local LII intensity of the laser-heated surface depends on the presence of undersurface structural. In the present work, we perform computer simulations of the processes of transient laser heating of a surface layer with hidden submicron-sized voids located under the surface in order to assess the possibilities of their visualization via LII. Calculations showed that undersurface microscopic inhomogeneities can significantly affect the local LII intensities of the laser-irradiated surface. The calculations were performed with the ordinary heat diffusion equation, assuming temperature-independence of material parameters as a first approximation. The intensity of LII was calculated with the using of Planck’s blackbody emission law at a fixed wavelength of 500 nm.
Maksym Kokhan, Ilona Koleshnia, Serge E. Zelensky, and Toru Aoki, "On the possibility of visualization of undersurface submicron-sized inhomogeneities via laser-induced incandescence of surface layers," Proc. SPIE 10097, High-Power Laser Materials Processing: Applications, Diagnostics, and Systems VI, 100970G (Presented at SPIE LASE: February 02, 2017; Published: 22 February 2017); https://doi.org/10.1117/12.2253006.
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