title: Preferential coupling of an incident wave to reflection eigenchannels of disordered media.
abstract: Light waves incident to a highly scattering medium are incapable of penetrating deep into the medium due to the multiple scattering process. This poses a fundamental limitation to optically imaging, sensing, and manipulating targets embedded in opaque scattering layers such as biological tissues. One strategy for mitigating the shallow wave penetration is to exploit eigenchannels with anomalously high transmittance existing in any scattering medium. However, finding such eigenchannels has been a challenging task due to the complexity of disordered media. Moreover, it is even more difficult to identify those eigenchannels from the practically relevant reflection geometry of measurements. In this Letter, we present an iterative wavefront control method that either minimizes or maximizes the total intensity of the reflected waves. We proved that this process led to the preferential coupling of incident wave to either low or high-reflection eigenchannels, and observed either enhanced or reduced wave transmission as a consequence. Since our approach is free from prior characterization measurements such as the recording of transmission matrix, and also able to keep up with sample perturbation, it is readily applicable to in vivo applications. Enhancing light penetration will help improving the working depth of optical sensing and treatment techniques.
authors.affiliation: Department of Physics, Korea University, Seoul 136-701, Korea.|Center for Molecular Spectroscopy and Dynamics, Seoul 136-701, Korea.
authors.forename: Wonjun
authors.initials: W
authors.lastname: Choi
authors.affiliation: Department of Physics, Korea University, Seoul 136-701, Korea.
authors.forename: Moonseok
authors.initials: M
authors.lastname: Kim
authors.affiliation: Department of Physics, Korea University, Seoul 136-701, Korea.
authors.forename: Donggyu
authors.initials: D
authors.lastname: Kim
authors.affiliation: Department of Physics, Korea University, Seoul 136-701, Korea.
authors.forename: Changhyeong
authors.initials: C
authors.lastname: Yoon
authors.affiliation: Department of Physics, Korea University, Seoul 136-701, Korea.|Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Fang-Yen
authors.affiliation: Department of Physics, Korea University, Seoul 136-701, Korea.
authors.forename: Q-Han
authors.initials: QH
authors.lastname: Park
authors.affiliation: Department of Physics, Korea University, Seoul 136-701, Korea.|Center for Molecular Spectroscopy and Dynamics, Seoul 136-701, Korea.
authors.forename: Wonshik
authors.initials: W
authors.lastname: Choi