Certain things in life can be predicted well. The tide rises and falls. The moon fluctuates. The billiard balls will bounce around the table according to the orderly geometric shapes.
Then, there is something that makes people unable to predict easily: the hurricane changed its direction without warning. Splashing water in the fountain. The graceful branches that grow from a tree are disorderly.
These and other similar phenomena can be described as chaotic systems, and are known for exhibiting initially predictable behavior, but becoming more and more random as time passes.
Because chaotic systems play an important role in the world around us, scientists and mathematicians have long sought to understand them better. Now, Professor Bren of Andrew and Peggy Cherng of the California Institute of Technology’s Department of Medical Engineering, and Lihong Wang of the California Institute of Technology have developed a new tool that can help with this task.
In the latest issue Scientific progress, Wang described how to record video at a rate of 1 billion frames per second using his own ultrafast camera to observe the movement of lasers in a room specifically designed to cause chaotic reflections.
Wang said: “Some cavities are non-chaotic, so the propagation path of light can be predicted.” But in the current work, he and his colleagues have used that ultrafast camera as a tool for studying chaotic cavities. Each time the experiment is repeated, the light travels in a different path.”
The camera utilizes a technology called Compressed Ultra Fast Photography (CUP), which Wang has demonstrated in other studies that can shoot at speeds of up to 70 trillion frames per second. The speed at which the CUP camera shoots video allows it to see light as it travels-this is the fastest thing in the universe.
But the CUP camera has another function that makes it particularly suitable for studying chaotic systems. Unlike traditional cameras that shoot one frame of video at a time, CUP cameras actually shoot all frames at once. This allows the camera to capture the entire chaotic path of the laser beam in the entire chamber at one time.
This is important because in a chaotic system, the behavior is different every time. If the camera captures only part of the action, the unrecorded behavior will never be studied, because the behavior will never happen in exactly the same way again. It’s like trying to photograph a bird, but using a camera that can only capture one body part at the same time; and every time the bird lands near you, it will be a different species. Although you can try to combine all the photos into a composite bird image, the cobblestone bird will have the beak of a crow, the neck of a stork, the wings of a duck, and the tail and legs of an eagle. A chicken. Not entirely useful.
Wang said that the ability of his CUP camera to capture the chaotic motion of light may inject new vitality into the study of optical chaos, which has applications in the fields of physics, communication and cryptography.
He said: “This was a very hot field some time ago, but it has disappeared, maybe because we don’t have the tools we need.” “The experimentalists lost interest because they were unable to conduct experiments, and the theorists lost Interested because they can’t verify their theory through experiments. This is an interesting demonstration to show people in the field that they finally have experimental tools.”
The paper describing the research is titled “Real-time Observation and Control of Optical Chaos” and was published on January 13 Scientific progress.
The new ultrafast camera can take 70 trillion photos per second
Fan Linran et al. Real-time observation and control of optical chaos Scientific progress January 13, 2021: Volume 7, No. 3, eabc8448, DOI: 10.1126/sciadv.abc8448
Provided by California Institute of Technology
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