Controlling and harnessing the behavior of light is crucial for advancements in various technological fields, ranging from energy harvesting and computation to communication and biomedical sensing. However, the unpredictable and chaotic nature of light has presented challenges in efficiently managing its behavior. Physicist Andrea Alù, an Einstein Professor of Physics at the CUNY Graduate Center, has drawn an analogy between chaotic light behavior and the initial shot in a game of billiards, where minute variations in cue ball launch lead to different ball trajectories. In the realm of light, this unpredictability arises when conducting experiments with similar settings that yield different outcomes each time.
In a recent study published in Nature Physics, a team of researchers led by the CUNY Graduate Center has introduced a novel approach to control the chaotic behavior of light by tailoring its scattering patterns using light itself. The study was spearheaded by co-first authors Xuefeng Jiang, a former postdoctoral researcher in Alù’s lab and now an assistant professor of Physics at Seton Hall University, and Shixiong Yin, a graduate student in Alù’s lab.
Traditional platforms for investigating light’s behavior often employ circular or regularly shaped resonant cavities, within which light follows more predictable patterns of scattering and reflection. In such cavities, only specific and distinct frequencies of light survive, each associated with a unique spatial pattern or mode. However, this approach falls short of fully comprehending the complexity of light behavior in intricate systems.
The researchers addressed this challenge by designing a large stadium-shaped cavity with an open top and two channels on opposing sides for directing light into the cavity. As incoming light scatters off the cavity walls and bounces around, a camera placed above records the amount of light escaping the stadium and its spatial patterns.
The device is equipped with adjustable knobs on its sides, enabling control over the light intensity at the two inputs and the delay between them. The opposing channels cause the light beams to interfere with each other within the stadium cavity, allowing the researchers to control one beam’s scattering through another in a process referred to as coherent control—essentially, using light to manage light. Remarkably, by altering the relative intensity and delay of the light beams entering the two channels, the researchers consistently modified the light’s radiation pattern outside the cavity.
This level of control became possible through the observation of a rare light behavior in resonant cavities known as “reflectionless scattering modes” (RSMs). While these modes had been theoretically predicted previously, they had not been observed in optical cavity systems until now. Manipulating RSMs as demonstrated in this study has far-reaching implications for efficient excitation and control of complex optical systems, with potential applications in energy storage, computing, and signal processing.
The researchers plan to expand their work by introducing additional controls in future studies, offering more degrees of freedom for unraveling further intricacies in light behavior. This research, titled “Coherent Control of Chaotic Optical Microcavity with Reflectionless Scattering Modes,” presents a significant step forward in our ability to manage and utilize light in complex systems.
