Colloquia & Guest Speakers

Measuring and Modeling the Polarization of Light Scattered from Surfaces

Dr. Thomas A. Germer, Sensor Science Division, NIST

Tuesday, October 3, 2017
1:30 p.m.

Wilmot Building, Fifth Floor Collaboratory


For many years, ellipsometry has been a powerful technique for characterizing thin films and their optical properties. Being an inherently ratiometric method, it has a number of measurement advantages, making it very precise. In terms of solving inverse problems, it has advantages over simple reflectance measurements, since it incorporates both phase and amplitude information. In our work, we have been motivated by both of these aspects to extend ellipsometry into the diffuse scattering regime, thus sensing not just film thickness and optical properties, but lateral structure and inhomogeneity. For diffuse scattering, there are more degrees of freedom for the measurement, and the Mueller matrix formalism must be used. Significant modeling is often required to interpret the results. However, in some cases, we have found that Mueller matrix decomposition, guided by measurement data, can yield interesting results. I will give examples of recent work we have performed, including structured silicon surfaces, birefringent glancing angle deposition thin films, and vertically-aligned carbon nanotubes.


Thomas A. Germer is a physicist specializing in measurements and modeling of the optical properties of materials at the National Institute of Standards and Technology in Gaithersburg, Maryland. He has published over one hundred technical papers, covering topics of electron and ultrafast time-resolved surface spectroscopy, diffuse optical scattering from particles, roughness, and defects near surfaces and thin films, polarimetry, critical dimension metrology by grating scatterometry, and biomedical optics. He is the developer of the SCATMECH library of light scattering codes and the associated MIST program. Dr. Germer received a B.A. from the University of California, Berkeley, and a M.S. and Ph.D. from Cornell University, and is a Fellow of SPIE.

Location:  Wilmot Building, Fifth Floor Collaboratory