Toward Characterization of a Rectangular Groove on a Metallic Surface by Multi-Angle Light Scattering

Abstract

Fast quantitative characterization of a rectangular groove with sizes from sub-micrometers to micrometers on a surface has been demanding in quality control of optical elements. We report a numerical procedure for retrieval of the geometrical parameters of a rectangular groove, including width and depth, from the angular distribution of the scattered light generated by launching plane waves on the groove on a metallic surface from different propagation directions. The far-field intensity of scattering light is first obtained by numerically solving the electromagnetic problem with the modal theory. Then, a two-stage inverse modeling approach is developed to retrieve the groove parameters based on the lookup table and repulsive particle swarm optimization from multi-angle scattering light distribution that is highly sensitive to the groove parameters. Noise influences are considered in the simulation. Results suggest that our method can precisely obtain the groove parameters for noisy signals. As the measurement of light scattering can be conducted with high efficiency, it should be a powerful tool to characterize rectangle grooves on metallic surfaces. INDEX TERMS Light scattering, groove parameter, inverse modeling, repulsive particle swarm optimization.

Time–Domain Electromagnetic Identification Based on Rectangular Grooves

“…The Finite-Difference Time-Domain approach was used to solve for the EM fields scattered by grooves in [20]. The authors in [21] proposed a method to characterize the properties of a single groove on a metallic surface by the angular distribution of the scattered light generated by a set of plane waves. Authors in [22] derived a method based on Geometric/Physical Optics to analyze the terahertz-wave scattering characteristics of objects with multiple small-scale grooves having the same dimensions.…”