Using probably one of the fastest cameras in the world, scientists from Washington University in St. Louis amazingly captured a photonic Mach cone, or a sonic boom of light, in action for the first time in history.
What Is A Photonic Mach Cone?
The typical sonic boom occurs as a loud, thunder-like sound whenever any form of aerospace vehicle flies faster than the speed of sound or supersonic. As the supersonic aircraft revs up its speed, pressure waves build up and form a shock wave.
This shock wave creates a "Mach cone," or a cone shape of pressurized air molecules, which appear most prominently at the rear of the supersonic aircraft. The same phenomenon can also be seen when a boat leaves V-shaped bow waves trailing behind as it travels faster than the waves it pushes out of the way.
Streak Camera Captures Sonic Boom of Light
Scientists have long theorized that light, too, can produce conical wakes like in sonic booms.
Proving this theory, Jinyang Liang, an optical engineer and the study's lead author, and his team launched green laser lights, each lasting for seven picoseconds, or trillionths of a second, down a little tunnel made of silicone rubber and aluminum oxide powder packed with dry ice fog.
They filmed this process using a custom-built "streak camera," which features an advanced technique called "lossless-encoding compressed ultrafast photography," or LLE-CUP. With the LLE-CUP system, Liang's streak camera can capture 100 billion frames per second in a single exposure, making it possible to film the scattering light in real time.
"Our camera is different from a common camera where you just take a snapshot and record one image: our camera works by first capturing all the images of a dynamic event into one snapshot. And then we reconstruct them, one by one," said Liang.
Practical Applications
Liang and his team are looking into the possible application of their streak camera in biomedical imaging. Ultrafast imaging technologies are already being used in medicine. However, they are often inefficient and inaccurate because they require multiple filming, which isn't always possible in the medical field.
"Our camera is fast enough to watch neurons fire and image live traffic in the brain," Liang stated in an article by Live Science. "We hope we can use our system to study neural networks to understand how the brain works." According to Liang, their LLE-CUP system can complement standard cameras, microscopes, and telescopes to detect the smallest neurons or cancer cells and monitor changes in the light within a supernova.
The full details of the study are published in the peer-reviewed multidisciplinary open-access scientific journal Science Advances.
