Polarized light scattering from metal surfaces

Abstract

The stretching and bending of polished and industrial-grade metallurgical surfaces changes the appearance of the specimen’s surface. The changes in surface structure can be detected in the polarized light scattered from the surface cracks and other defects, which act as scattering centers. In order to interpret light scattering signals from complex surfaces, we first examine the nature of light scattered from a perfect mirror surface, a degraded mirror, a line on a mirror, a randomly sanded surface, and, finally, the industrial grade metal surfaces damaged by stretching and bending.

Light depolarization in off-specular reflection on submicro rough metal surfaces with imperfectly random roughness

“…17,28 Even if the materials are confined to be the same and the differences among samples are confined to only surface condition, depolarization is still related to microcosmic height/particle distribution (geometric property) in the nonlinear Rayleigh scattering or near-linear Mie scattering levels. 19,20,33,34 Meanwhile, even on highly conductive metal surfaces that are comparatively simple because of the lack of multilayer reflection (although they cannot be treated as an ideal conductor because of the light wavelength), comparatively few publications are found on studying the mechanism of depolarization in the light scattering at imperfectly random rough surfaces that have statistical height distributions of non-Gaussian ones (that are quite general in practical polished or textured surfaces). [20][21][22][23]35,36 Bickel et al briefly reported the depolarization effect in Stokes vectors (macrocosmic expression) of the scratches/lines on both perfect mirror and randomly sanded brass surfaces using a He-Cd laser source with beam diameter of 600 µm, 20,23 but there is no further quantitative comparison maybe mainly due to the limitation in the lack of precise submicro or nm-level geometric information at that time.…”

“…19,20,33,34 Meanwhile, even on highly conductive metal surfaces that are comparatively simple because of the lack of multilayer reflection (although they cannot be treated as an ideal conductor because of the light wavelength), comparatively few publications are found on studying the mechanism of depolarization in the light scattering at imperfectly random rough surfaces that have statistical height distributions of non-Gaussian ones (that are quite general in practical polished or textured surfaces). [20][21][22][23]35,36 Bickel et al briefly reported the depolarization effect in Stokes vectors (macrocosmic expression) of the scratches/lines on both perfect mirror and randomly sanded brass surfaces using a He-Cd laser source with beam diameter of 600 µm, 20,23 but there is no further quantitative comparison maybe mainly due to the limitation in the lack of precise submicro or nm-level geometric information at that time. Crespo et al did plenty of numerical simulations on rough random surfaces that had R q of 0.1-2λ generated using Monte Carlo method, 21 but no depolarization effects were accounted as they studied one-dimensional (1D) surfaces and treated the surfaces as perfectly conductive ones.…”

“…On the other hand, optical methods of depolarization analyses were developed based on the fact that depolarization happens as the roughness degree of a surface to be inspected increases from a comparatively smooth mirror to rough surface. 17 Scattering depolarization has been studied and reported in both theoretical and laboratorial researches for more than forty years, [18][19][20][21][22][23][24][25][26][27][28] observed for more than ten years during carrying out nondestructive testing (NDT) research on thin film growth, 29,30 and also the polarization extinction was analyzed by surface roughness, bulk heterogeneity, and interface scatters in the recent ten years. 31,32 However, most of them focused on analyzing samples of randomly rough surfaces and also the majority are numerical simulations.…”

Transition radiation based transverse beam diagnostics for non relativistic ion beams

“…Scattering of light from a rough surface has been a subject of intensive study for many decades since all surfaces are rough to some extent. The studies have mainly been performed either from the material surface characterization perspective [14] or were efforts towards building perfect mirrors [15,16]. Broadly speaking, rough surfaces are typically characterized as "weak" or "strong" rough surfaces based on the "rms" roughness and characteristic length (correlation length) with respect to the incident light wavelength [16].…”

<title>Goniometric optical scatter instrument for bidirectional reflectance distribution function measurements with out-of-plane and polarimetry capabilities</title>

“…(8) The primed coordinate system tracks the sample orientation in terms of the laboratory-based coordinate system.…”