Observation of Mutual Transparency and Mutual Extinction of Light

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 [1]. Intriguing interference appears that leads to either enhanced transparency or enhanced extinction, called mutual transparency or extinction, depending on the phase difference between the beams. Here, we present an experimental study of this effect. We use a human hair as a strongly absorbing sample. A liquid crystal phase retarder is used to control the phase difference between two incident beams. We observe an enhancement in transparency and extinction by up to 10 percent varying the angle between the beams, in excellent agreement with theory. We discuss the novel applications of mutual extinction and transparency effect in microscopy and bio-imaging.