NIST Researches Optical Scattering from Surfaces
The National Institute of Standards and Technology (NIST) is conducting research on optical scattering from various surfaces to develop standard measurement methods and artifacts. This research aims to evaluate highly polished optical surfaces, bulk optical materials, surface residues, and diffuse scattering materials. Optical scattering can also be used to assess the uniformity of periodic structures like compact disks and semiconductor deposited lines.
Polarization of Scattered Light Provides Clues
The polarization of scattered light can indicate the source of the scattering. NIST researchers use Light Scattering Ellipsometry to measure the polarization of light scattered out of the plane of incidence for a fixed incident polarization. This technique allows them to distinguish between scattering from microroughness, subsurface defects, and particulate contamination.
Software and Instrumentation for Optical Scattering Analysis
NIST has developed the SCATMECH: Polarized Light Scattering C++ Class Library, which allows researchers to utilize models for polarized light scattering from surfaces. The library can be easily expanded to include new models. The Modeled Integrated Scatter Tool (MIST) program is a general application for modeling an integrated scattering system.
A laser-based goniometric optical scatter instrument (GOSI) is available for measuring the bidirectional reflectance distribution function (BRDF), its polarization counterpart (Mueller matrix BRDF), or other light scattering ellipsometry parameters from various samples or surfaces. The instrument is housed in a clean environment to maintain sample integrity.
The research focuses on placing the technique on a firm metrological basis, ensuring quantitative accuracy. Polarized light scattering in the Stokes-Mueller representation is also studied.
Source: https://www.nist.gov/programs-projects/optical-scattering-surfaces
Keywords: Metrology, Scattering, Polarization, Ellipsometry, BRDF
