Conclusion
Diffusion of light through surfaces and volumes

Light scattering remains a key tool for many precision opticians. In particular, it provides a metrology tool that is directly linked to the desired application. It gives the user the benefit of simplicity: an angular scattering measurement, combined with the calculation of an optical factor, gives access to the surface roughness or volume permittivity spectrum.

Roughness is always relative to a bandwidth that must be specified; this condition is necessary for any intercomparison between different metrology instruments. Far-field optical measurement is macroscopic in nature and gives access to the low frequencies responsible for scattered flux, while local probe measurement gives access to the high frequencies closer to atomic structure. Bandwidths can be extended by modifying the illumination wavelength (scattering) or the sampling step (AFM).

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