We experimentally demonstrate a nonimaging approach to displacement measurement for complex scattering materials. By spatially controlling the wavefront of the light that incidents on the material, we concentrate the scattered light in a focus on a designated position. This wavefront acts as a unique optical fingerprint that enables precise position detection of the illuminated material by simply measuring the intensity in the focus. By combining two fingerprints we demonstrate position detection along one in-plane dimension with a displacement resolution of 2.1 nm. As our approach does not require an image of the scattered field, it is possible to employ fast nonimaging detectors to enable high-speed position detection of scattering materials.

Opt. Lett.

van Putten, E. G., Mosk, A., & Lagendijk, A. (2012). Nonimaging speckle interferometry for high-speed nanometer-scale position detection. Opt. Lett., 37(6), 1070–1072. doi:10.1364/OL.37.001070