Sensing the position of a single scatterer in opaque media using Mutual Extinction & Transparency

Abstract

Traditional scattering experiments are associated with sending a single beam on a target.The detailed structure of the target including the positions of all scatterers are encoded in the characteristics of the scattered waves. However, when a medium becomes opaque, usual single scattering (Fourier) approaches break down and only limited information is available by, e.g., diffusing wave spectroscopy. Recently, the development of multiple-beam techniques, e.g., wavefront shaping, has opened more potential in the research of opaque samples. Different from the case of a single incident wave, the interference of multiple beams gives rise to a new phenomenon called ”Mutual Extinction and Transparency” [1]. Here, we conjecture that Mutual Extinction with 2 incident beams is a promising technique to detect the movement of a dipole in a sample of multiple stable dipoles (see Fig. 1 for more details). The underlying idea is that the cross-interference information of 2 beams is more sensitive to changes of the scatterer located deep within the sample than conventional 1-beam scattering methods. For comparison, we perform exact calculations of the sensitivity of Mutual Extinction (from 2 beams) and the differential cross-section (from 1 beam) in response to the displacement of 1 dipole. Our numerical results confirm that Mutual Extinction is indeed more sensitive (see Fig. 2), thus, a better tool (than traditional 1-beam techniques) to locate a single scatterer inside a multiple scattering sample.