| Abstract Scope |
Although strain measurement via optical diffraction is conceptually simple and well understood, it has thus far been limited with respect to strain resolution. This work, based on a simple one-dimensional diffraction grating, builds on prior optical diffraction techniques to significantly extend the resolution with which strain may be measured. A new approach termed grazing excidence optical diffraction (GEOD) is introduced, demonstrating an ultimate strain resolution of ~800 picostrain, under true quasi-static loading conditions, i.e. without any signal averaging. We designate the condition, θ→π/2, grazing excidence, to describe a diffracted beam that is nearly parallel to the surface of the grating. For some perspective, for the grating used (d=1.266 μm), 800 picostrain corresponds to a change in average grating spacing of approximately one femtometer, or 1/100,000 the atomic radius of a silicon atom. |