The information age in optics: Measuring the transmission matrix

Optical elements such as lenses and polarizers are used to modify the propagation of light. The transformations of the optical wave front that these elements perform are described by simple and straightforward transmission matrices (Fig. 1). The formalism of transmission matrices is also used to microscopically describe the transmission through more complex optical systems, including opaque materials such as a layer of paint in which light is strongly scattered. A microscopic description of this scattering process requires a transmission matrix with an enormous number of elements. Sébastien Popoff, Geoffroy Lerosey, Rémi Carminati, Mathias Fink, Claude Boccara, and Sylvain Gigan of the Institut Langevin in Paris now report in Physical Review Letters an experimental approach to microscopically measure the transmission matrix for light [1]. Knowledge of the transmission matrix promises a deeper understanding of the transport properties and enables precise control over light propagation through complex photonic systems.