Physical Light-Matter Interaction in Hermite-Gauss Space

Shlomi Steinberg
ACM Transactions on Graphics (Proceedings of SIGGRAPH ASIA 2021)

To Appear

Partially-coherent light transport in a scene with diffractive materials. The insets visualise the shape of the coherence area (see Fig. 4) of light that is sourced from a light source or scattered by matter. A spherical source gives rise to light with (a) highly isotropic spatial coherence, while a cylindrical source produces light that is (b) significantly more coherent in one transverse direction than in the other (a phenomenon we term coherence anisotropy). Light then propagates away from the source and interacts with matter. These physical processes—the coherence of light and light-matter interaction—are mutually-dependant processes: Coherence drives the optical response of the interaction of light with matter, and, conversely, the properties of matter alter the coherence properties of the scattered radiation. (c) Thin coating over the wings of a silver scarab induces interference. The distinct colours on the left and right wings arise solely due to the difference in the spectral composition and coherence of the incident light. The surface is smooth and the scattered light retains the coherence shape of the incident light. (d,e) On the other hand, scatter by rough surfaces induces coherence properties and anisotropies that are dictated by the surface parameters. (f) Diffraction grating by (unrecorded) DVD disks. Note that the secondary diffraction lobes diminish due to the limited spatial coherence of light. One of the primary theoretical conclusions of this paper is that it is the ensemble-averaged reflectivity of the matter that drives the coherence shape of the scattered light. This can be seen in (c) and (f), where the induced interference does not influence the scattered radiation’s coherence properties.

Abstract