Ultrafast Laser-Assisted Imaging

BBC News, Intersciences.org, UCLA Newsroom: Researchers at the UCLA Henry Samueli School of Engineering and Applied Science have developed a novel camera that captures images thousand times faster than any existing conventional camera. Dubbed Serial Time-Encoded Amplified imaging, or STEAM, the new imaging technique depends on carefully manipulating so-called "supercontinuum" laser pulses.

These pulses, less than a pico-second long, contain a broad range of colors. Two optical elements spread the pinprick laser pulses into an ordered two-dimensional array of colors. This "2-D rainbow" illuminates a sample. Part of the rainbow is reflected by the sample - depending on light and dark areas of the illuminated spot - and the reflections travel back along their initial path.

Because the spreading of the pulse's various colors is regular and ordered, the range of colors reflected contains detailed spatial information about the sample. The pulse then passes back through the dispersive optics and again becomes a pinprick of light, with the image tucked away within as a series of distributed colours.

However, that color spectrum is mixed up in an exceptionally short pulse of light that would be impossible to unpick in traditional electronics. The team then routes the pulse into a dispersive fibre - a fibre-optic cable that has a different speed limit for different colors of light. As a result, the red part of the spectrum races ahead of the blue part as the pulse travels along the fibre. Eventually, the red part and blue part separate in the fibre, arriving at very different times at the fibre's end.

All that remains is to detect the light as it pops out of the fibre with a standard photodiode and digitize it, assigning the parts of the pulse that arrive at different times to different points in two-dimensional space.

Now researchers are looking for a possible application for the fast camera. "The most demanding application for high-speed imaging involves fast events that are very rare, rogue events or the proverbial needle in the haystack — in other words, unusual events that carry important information," said Jalali, a professor of electrical engineering and principal investigator of the project.

Update: The original Nature Journal paper is here, for those who have a subscription.