Light 'sonic boom' filmed in a single shot for first time


The camera system, which captures 100 billion frames per second, could be used to film electrical signals between brain cells. Angus Bezzina reports.


An illustration of a photonic Mach cone. Ån ultrafast camera has filmed one in real life.
Jinyang Liang and Lihong V. Wang

A new camera system that can capture 100 billion frames each second has become the first to record light creating a "sonic boom" in a single shot.

The camera (or lossless-encoding compressed ultrafast photography – LLE-CUP – system as it is officially known) was created by Jinyang Liang from Washington University in the US and his colleagues, who outlined their experiment to record the so-called photonic Mach cone in Science Advances.

This technology could be used in biomedicine, for instance, as it’s capable of mapping the high-speed firing of brain cells.

Just as an aircraft that breaks the speed of sound produces a booming pressure wave – called a Mach cone – so can light.

But this is only possible if light is slowed down by, for instance, passing it through glass. (After all, nothing can travel faster than the speed of light in a vacuum, not even a shockwave.)

Liang and his crew built a device to hit light’s brakes – a narrow tube filled with a cloud of dry ice, sandwiched between aluminium oxide and silicone.

When they fired a laser pulse lasting just seven trillionths of second through the layers, it passed through the walls of the tunnel slower than the fog, creating a photonic Mach cone.

Of course, they couldn’t use any old camera to film the Mach cone so the team also designed and built an ultrafast apparatus – the LLE-CUP – capable of filming 100 billion frames per second.

While other ultrafast cameras must stitch together hundreds or even thousands of measurements to reveal a moving image, the LLE-CUP could do the same in a single shot.

Liang et al. Sci. Adv.2017;3:e1601814

“Single shot versus multi-shot is the biggest difference between our camera system and previous methods to image photonic Mach cones,” Liang notes.

Liang and his team claim that the success of their product in this experiment holds great promise for the LLE-CUP’s applications in a broad array of scientific fields.

“Our camera is very generic – essentially we have developed a light-speed camera,” Liang says.

“The camera can be combined with photography, microscopy or even telescopes so we can adjust our spatial and temporal resolution depending on what kind of image modality we would like to couple it with.”

He notes that the kind of ultrafast imaging of light distribution that the LLE-CUP provides would be particularly useful in biomedicine. If coupled with a microscope, scientists might view single-shot, full-field images of 3-D microstructures in biological systems.

While these results are already impressive, Liang says his team are finessing the LLE-CUP design even further. Theoretically, he says, they could double the number of frames per second that the camera currently captures.

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Angus Bezzina is a writer from Sydney, Australia.