New light-controlling device could allow LIDAR to image scenes a million times faster

Controlling light "has been a recurring research theme since antiquity."
Chris Young
wireless spatial light modulator
Scientists have developed a programmable, wireless spatial light modulator that can manipulate light at the wavelength scale with orders-of-magnitude faster response than existing devices.

Sampson Wilcox 

An international group of researchers, led by a team at MIT, spent more than four years developing technologies for high-speed optical beam forming.

They have now presented the fruits of their labor: a programmable, wireless device that can control light. The new system can manipulate the intensity of light and focus it in specific directions, and "do it orders of magnitude more quickly than commercial devices," an MIT press statement reveals.

The researchers also developed a pioneering fabrication process that will ensure the quality of the device if and when it is manufactured at scale.

Controlling lightwaves

The team of scientists says their device, named a spatial light modulator (SLM), could be used to create a super-fast LIDAR sensor for self-driving cars. They claim the LIDAR sensor using their technology would be able to map out a scene approximately a million times faster than existing systems.

The device could also allow for much faster brain scanners that use light to "see" through human tissue, allowing them to generate higher-resolution images. The researchers presented their findings in a paper published in the journal Nature Photonics.

"We are focusing on controlling light, which has been a recurring research theme since antiquity," lead author Christopher Panuski explained in the MIT post. "Our development is another major step toward the ultimate goal of complete optical control — in both space and time — for the myriad applications that use light."

An "ideal optical antenna"

An SLM manipulates light by controlling its emission properties. To precisely control tiny light wavelengths, the device features a two-dimensional array of optical modulators as well as an array of photonic crystal microcavities that allow light to be stored and emitted at the wavelength scale.

Over the course of about a billionth of a second, these photonic crystal microcavities can manipulate light by controlling how quickly it escapes. Controlling the entire array, meanwhile, modulates an entire light field, so scientists can precisely steer a beam of light.

"One novel aspect of our device is its engineered radiation pattern. We want the reflected light from each cavity to be a focused beam because that improves the beam-steering performance of the final device. Our process essentially makes an ideal optical antenna," Panuski says.

The team also used a micro-LED display to control the SLM during their experiments, with one LED tuning to a single microcavity. Using this method means the array is programmable, reconfigurable, and completely wireless, according to Panuski. "It is an all-optical control process. Without metal wires, we can place devices closer together without worrying about absorption losses," he said.

On top of all of this, the researchers partnered with the Air Force Research Laboratory to develop a highly precise mass-manufacturing process that they believe will make their device scalable for the mass market. It stamps billions of cavities onto a 12-inch silicon wafer and utilizes a post-processing step to make sure all of the microcavities operate at the same wavelength.

During their experiments, the researchers said their device was able to almost perfectly control an optical field with a joint "spatiotemporal bandwidth" 10 times greater than that of existing SLMs. Their work could one day allow for ground-breaking new technologies for medicine, self-driving vehicles, and communications systems.

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