Tech bends light more efficiently, offers wider angles for light input

A one-inch diameter Bragg polarization grating diffracts white light from an LED flashlight onto a screen placed nearby. Even though the difference between the light’s input and output direction is very large, the grating is highly efficient for a wide set of input angles. The extremely large color separation occurs because the grating structure has a nanoscale periodic structure smaller than the wavelength of visible light.

Illustration of the director profile of the two-slant LC polymer Bragg PG. All notation follows ref.13.
Illustration of the director profile of the two-slant LC polymer Bragg PG. All notation follows ref.13.

Until now, state-of-the-art diffraction gratings designed to guide visible light to expansive edges have had a precise acknowledgment range, or with a bandwidth of 20 degrees. It means, the light source must be coordinated into the grating inside an arc of 20 degrees.

Now, scientists at the North Carolina State University came up with a new technology that steers light with more light input and greater efficiency. This new type of grating that allows light to enter the grating from a wider range of input angles with the bandwidth of 40 degrees.

Michael Escuti, a professor of electrical and computer engineering at NC State said, “The practical effect of this – in augmented-reality displays, for example – would be that users would have a greater field of view; the experience would be more immersive.”

Xiao Xiang, a Ph.D. student at NC State said, “In previous gratings in a comparable configuration, an average of 30 percent of the light input is being diffracted in the desired direction. Our new grating diffracts about 75 percent of the light in the desired direction. This advance could also make fiber-optic networks more energy efficient.”

The technology achieves the advance in angular bandwidth by integrating two layers, which are superimposed in a way that enables their optical reactions to cooperate. One layer contains particles that are orchestrated at a “slant” that enables it to catch 20 degrees of precise transfer speed. The second layer is orchestrated at an alternate inclination, which catches a neighboring 20 degrees of precise data transmission.

The higher efficiency stems from a smoothly varying pattern in the orientation of the liquid crystal molecules in the grating. The pattern affects the phase of the light, which is the mechanism responsible for redirecting the light.

Scientists are now working to take the advantages of these gratings and make a new generation of augmented-reality hardware.

The study is published in the journal Scientific Reports.

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