Activity: Talk or presentation › Oral presentation
The well-known optical theorem describes that extinction energy lost from a light beam is equal to scattering in all directions, and possible absorption . Recently, our group has generalized the theorem to multiple incident beams , with which we discovered it is possible to either enhanced transparency or enhanced extinction in a scattering system with multiple beams, controlling the relative phase and angle between them. This effect is called mutual transparency or extinction. Here, we present an experimental study of this effect. We use a strongly scattering sample made from a strip of silicon (see figure 1.b). A liquid crystal phase retarder is used to control the phase difference between two incident beams and using an unbalanced March-Zehnder interferometer, we can control the relative angle with a movable mirror. For small angles, we can almost duplicate the total extinction or nearly annihilate it. In Figure 1.a a curve of total extinction against the relative angle is shown. As can be seen, the experimental data closely follows the theoretical model . We investigate the phase and also angle dependency of the total extinction and how the Fraunhofer diffraction model compares to our exact calculations. Our technique has the potential to control both forward and backscattering on a sample.