Disorder-induced coherence enables control of wave transport

ABSTRACT

Waveforms matched to the eigenchannels of the electronic transmission matrix and their classical-wave counterparts produce striking variations in transmission—from complete to vanishing—and in internal energy density, revealing new possibilities for communications, imaging, sensing, and energy delivery. Yet the origin of these departures from diffusive transport has remained elusive: they can arise only through interference, but coherence between incident and internal waveguide modes is rapidly lost as waves scatter. In this talk we show, through microwave measurements and simulations, that although coherence with incident modes is destroyed, phase coherence nonetheless builds among the modes within the medium and governs the flux, energy density, and velocity throughout the sample. This coherence manifests itself in the growing diversity of modal flux across transmission eigenchannels, which mirrors the distinctive angular spread of modal contributions to each transmission eigenchannel. The balance between the fixed incident weights, diminishing flux-matrix amplitudes, and growing internal coherence determines the modal composition within each eigenchannel throughout the sample and enables measurements of transmission eigenvalues that are orders of magnitude below the instrumental noise floor. This establishes a foundation for controlling transport in complex media and for understanding the scaling of mesoscopic electronic conductance and wave transmittance.

BIOGRAPHY

Azriel Genack is a Distinguished Professor of Physics at Queens College and the Graduate Center of the City University of New York. He received his Ph.D. in Physics at Columba University in 1973 on nuclear magnetic resonance in superconductors (Alfred Redfield). As a postdoc, he studied resonant Raman scattering in crystals (CCNY, Herman Cummins) and coherent optical transients (IBM Research, Richard Brewer). He worked at Exxon Research from 1977-1984 on surface enhanced Raman scattering and optical propagation in random media. He has been at Queens College since 1984, where he focuses on the study of wave propagation. In 1999, he co-founded Chiral Photonics, Inc., which now produces fiber optics polarizers and couplers for applications in telecommunications and sensing. He is a fellow of the APS and Optica.