Complex optical properties of random materials obtained with Mutual Extinction

Modern techniques for studying and controlling light scattering, such as wavefront shaping (WFS), rely heavily in the interference of scattered waves. In WFS, the intensity of light is optimized, which is proportional to the absolute square of the scattering amplitude. Recently, we introduced a new type of wavefront called Mutual Extinction (ME), where the light extinction is optimized. In contrast with the intensity, the light extinction is directly proportional to the scattering amplitude. Therefore, ME gives information about complex media that WFS cannot access.
In our experiments, we study various strongly scattering samples such as a silicon bar and a human hair. We illuminate the sample using two crossing beams. With ME we control how much light is extinguished inside the sample, making it more opaque or more transparent. For small angles, this allows us to almost double the total extinction (object twice as opaque) or nearly inhibit it (object fully transparent).
The modulation range of the total extinction depends on the relative angle and phase between the incident beams, which yields information about the amplitude and phase of the scattering amplitude, respectively. Furthermore, the angle dependency of the total extinction give us information about the overall shape of the object. In this work, we show how to extract this new information from our experiments and study the application of this new technique.