The behavior of light is complex in real-world circumstances, which makes it difficult to govern effectively. Physicist Andrea Alù compares how light behaves in chaotic systems to a billiards game’s opening break stroke.
A group of CUNY researchers has published a report outlining a novel platform for controlling light’s chaotic behavior by adjusting its scattering patterns directly from the light source.
Light bounces and scatters in more predictable patterns in resonant cavities that are circular or regularly shaped, which are the standard platforms for investigating the behaviors of light. For instance, only distinct and predictable frequencies (colors of light) remain in a circular cavity, and each supported frequency is linked to a specific spatial pattern or mode. Understanding the physics at work in a circular hole can be done in just one way at a single frequency. Still, this method only partially unlocks the complexity of light behaviors observed in complex platforms.
To overcome the challenge, the group created a large stadium-shaped cavity, which has an open top and two channels that stream light into it from opposite sides. A camera overhead captures the amount of light leaving the stadium and its spatial patterns as it scatters and bounces off the walls.
To control the light intensity at the two inputs and the delay between them, the device has knobs on its sides. The stadium cavity’s opposing channels cause the light beams to interfere, allowing for coherent control—basically, using light to control light—whereby one beam’s scattering may be managed by the other.
This control was made possible by “reflectionless scattering modes” (RSMs), a rare behavior of light in resonant cavities that has previously only been theoretically predicted but not demonstrated in optical cavity systems.
Shixiong Yin, a graduate student in Alù’s lab, said, “The ability to manipulate RSMs demonstrated in this work allows for the efficient excitation and control of complex optical systems, which has implications for energy storage, computing, and signal processing.”
“We found at certain frequencies our system can support two independent, overlapping RSMs, which cause all of the light to enter the stadium cavity without reflections back to our channel ports, thus enabling its control. Our demonstration deals with optical signals within the bandwidth of optical fibers that we use in our daily life, so this finding paves a new way for better storage, routing, and control of light signals in complex optical platforms.”
Scientists are looking forward to adding more knobs in future studies, offering more degrees of freedom to unravel further complexities in the behavior of light.