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Ultra-sensitive Light Detector Offers Driverless Tech a Jolt

Published Sun, May 30 2021 18:38 pm
by The Silicon Trend


Realizing the ability of autonomous vehicles hinges on the tech that can swiftly sense & react to hazards & other vehicles in real-time. Engineers from the University of Texas at Austin & the University of Virginia developed a novel light detecting device that can precisely amplify weak signals bouncing off of faraway objects than existing tech allows, offering self-driving vehicles a fuller picture of what's happening on the road.

The novel device is more sensitive than other light detectors, eliminating noise associated with the detection process. Such noise cause systems to miss signals & puts the passengers at risk. It has a staircase-like alignment with physical steps in energy that electrons roll down & multiplying along the way, developing a more robust electrical current for light detection as they go.

Seth Bank, professor in the Cockrell School's Department of Electrical & Computer Engineering, said that the electrons are like marbles rolling down a flight of stairs. Each time the marbles roll off the step, it drops & crashes onto the next one. In this case, electrons do the same thing, but each collision releases enough energy to free another electron.

The novel pixel-sized device is ideal for light detection & ranging (LIDAR) receivers that need high-resolution sensors to detect optical signals reflected from far objects. Lidar is a vital part of autonomous vehicle tech & it also has applications in terrain mapping, robotics & surveillance. Adding steps increases the consistency & sensitivity of the device & the consistent multiplication of electrons with each step creates the detector's electrical signals more dependable, even in less light situations.

Bank stated that the less random the multiplication is, the weaker the signals we pick out from the background. For instance, it could permit us to look out farther distances with a laser radar system for self-driving vehicles. This type of sensing ability has existed for decades, but the technological obstacles held back its advancement. Photomultiplier tubes long represented the 'holy grail' of this sensing form. Bank quoted, but the tech has been around for more than 50 years, using outdated vacuum tubes & lightning components.

An inventor - Federico Capasso, in the 1980s first conceived of avalanche photodiode tech. But the methods & tools to make it a reality weren't far enough. Seth Bank mentioned the science behind this innovation comes in a novel way of growing materials. Instead of growing materials with randomly distributed atoms, they developed alloy layers composed of binary compounds made up of 2 elements, stacked one above the other.

This device permits modification of the electron's energy landscape in a straightforward method to develop the structure that Capasso imagined in the early 80s. Still, unfortunately, there just wasn't the potential to synthesize crystals that had all the requisite properties. Another significant part of this device is that it can operate at room temperature. Today, the most sensitive light detectors must be kept at temperatures hundreds of degrees below zero, making them impractical & too expensive for applications such as Lidar.

The probe was funded by the US Army Research Office (ARO) & The Defence Advanced Research Projects Agency (DARPA). The scientists have funding via DARPA & ARO to continue refining their method to add even more steps to the device. They are operating with a semiconductor firm to commercialize the tech. The engineers also plan to combine their multi-step staircase device with an avalanche photodiode they created last year, which is sensitive to near IR light, which opens up novel applications such as thermal imaging & fiber-topic communications.

Bank stated, "This should offer us the best of both worlds: greater sensitivity to weak signals & response to a wider color range because of low noise amplification that comes naturally from the staircase design."






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