Semi-transparent nanostructured surface applicable to AR/VR technology
Institute Reference: 2-19053
Dielectric reflective metasurfaces provide a versatile alternative to conventional optics, especially in compact near-eye display systems for augmented reality applications. In typical reflective metasurfaces, there is a non-transparent metal backplate that blocks the transmission of light, thus hindering user visibility. As a result, there is a need for a method that achieves semi-transparency while preserving the reflective properties of structured metasurfaces.
University of Rochester researchers propose a method to produce a see-through metal-dielectric metasurface device. With this device, light can be transmitted through the backplate while maintaining the reflective functions of metasurfaces in the front.
An incoming wavefront interacts with the subwavelength elements of the device (referred to as tokens). Each of the tokens can be individually tuned by changing the local dimensions like width and height. The reflected wavefront can be freely modified through these adjustable tokens. To achieve wavefront shaping, the device needs to be positioned on top of a non-transparent metal plate. Apertures of random position and diameter (RPD) are then etched through the tokens and metal backplate. Next, an RPD pattern is overlaid on top of the reflective grating structure. Apertures are made significantly larger than tokens and the wavelength that the device is designed to be used with. This ensures that the rear of the device is see-through while preventing interference with the reflective properties of the front. Researchers randomize the size and position of the apertures to minimize sharp diffraction features that can degrade the see-through quality.
The fabricated device shows ∼20% diffraction efficiency in the first diffractive order over 0-50 ° angle of incidence, which agrees with experimental electromagnetic simulations. The technology is semitransparent, letting ∼50% of the light illuminating the back of the device through via the RPD apertures. Furthermore, the light transmitted through the RPD apertures does not show any defined features due to diffraction, such as rings and fringes, aside from a quasi-uniform halo.
This technology has applications in AR/VR headsets since it enables adding a see-through component to ocular systems, enhancing external visibility without hindering the immersive experience.
The university seeks to license this technology exclusively.