Metasurfaces for ultrasmall solid-state LiDAR sensors? - Laser Focus World

A probe squad from Pohang University of Science and Technology (POSTECH) and Sungkyunkwan University successful South Korea is tapping metasurfaces to make a solid-state LiDAR sensor with a 360-degree presumption of its surrounding environment.

Metasurfaces are 2D arrangements of designed nanostructures that deduce their properties—such arsenic resonant and waveguide effects—from their gathering blocks.

LiDAR sensors service arsenic eyes for autonomous vehicles by projecting airy onto objects to assistance place the region to them, arsenic good arsenic the velocity and absorption of the vehicle. These sensors ideally should “see” from the sides arsenic good arsenic the beforehand and rear of the vehicles, but the rotating LiDAR sensors presently successful usage contiguous marque it intolerable to spot some beforehand and rear simultaneously.

The metasurface the squad uses for its sensor is simply a level optical instrumentality that greatly expands the viewing space of the LiDAR sensor to 360-degrees. It extracts 3D accusation of objects successful 360-degree regions and scatters much than 10,000 laser dot arrays from the metasurface to objects, past photographs the irradiated constituent signifier with a camera.

“This benignant of LiDAR sensor is utilized for the iPhone’s Face ID,” says Gyeongtae Kim, a Ph.D. campaigner moving with Professor Junsuk Rho successful the Departments of Mechanical Engineering and Chemical Engineering astatine POSTECH, arsenic good arsenic Yeseul Kim and Jooyeong Yun, Ph.D. candidates astatine POSTECH, and Professor Inki Kim astatine Sungkyunkwan University. “It uses a dot projector to make the constituent sets, but has respective limitations: the uniformity and viewing space of the constituent signifier are limited, and the instrumentality is large.”

Diffractive optical elements are usually utilized to signifier laser dot arrays for LiDAR, but thin to effect successful constricted field-of-view (FOV) and diffraction ratio due to the fact that of their micron-scale pixel size.

So that’s wherefore the squad opted alternatively for a metasurface-enhanced structured-light-based depth-sensing level that scatters high-density 10K dot array implicit the 180-degree FOV by manipulating airy astatine subwavelength scale.

As their impervious of concept, the researchers placed 1 facemask connected the beam axis and different 1 50 degrees away, wrong a region of 1 meter, and estimated the extent accusation utilizing a stereo-matching algorithm (see figure).

One of the large challenges to flooded is the sensor’s moving distance, which is constricted to a fewer meters owed to the powerfulness dispersion of a precocious fig of diffraction beams. “Such limitations tin beryllium flooded by utilizing a higher-power laser and expanding the diffraction ratio of the metasurfaces,” says Kim.

A nanoparticle-embedded-resin imprinting method enables the squad to people their caller instrumentality onto immoderate substrate—including assorted curved surfaces specified arsenic glasses oregon substrates for AR glasses. “We’ve shown we tin power the propagation of airy successful each angles by processing a exertion much precocious than accepted metasurface devices,” Rho says. “This archetypal exertion volition alteration an ultrasmall and full-space 3D imaging sensor platform.”

The team’s full-space diffractive metasurfaces whitethorn soon alteration an ultracompact depth-perception level for look designation and automotive robotic imaginativeness applications.

FURTHER READING

G. Kim et al., Nat. Commun., 13, 5920 (2022); https://doi.org/10.1038/s41467-022-32117-2.