Influence of anisotropy factor on the memory effect: A systematic study

Optical angular memory effect (AME) is the theoretical foundation of many promising techniques, such as wavefront shaping assisted microscopies, that have allowed us to see clearer and deeper into biological tissues. Conventional predictions in the field only take medium thickness into account, and have been proved to deviate away from practice, especially for biological tissues. Some recent explorations have improved the theory; the paraxial condition governed in most studies, however, restricts the accurate prediction to very thin layers, say, less than 300 μm even when the anisotropy factor is larger than 0.95. To explore the boundaries and promote applications of imaging techniques under different circumstances, a full and accurate understanding of the AME range is urgently needed. In this work, we explore the influence of anisotropy factor g on the AME range with different sample thicknesses. An empirical relationship among the AME range, sample thickness, and g is derived and verified: as g approaches 1, the AME range yields significant enhancement; such dependence on g, however, diminishes rapidly with increased sample thickness. It confirms a rule of thumb that it is meaningful to exploit the AME range only when ballistic photons and/or forward scattering light are non-ignorable.