Full-color optical combiner based on multilayered metasurface design

Optical combiners are see through optical components, which fuse a virtual image with the real-world scene, and play a key part in near-to-eye (NTE) visors and head-up displays (HUDs). Several types of optical combiners have been demonstrated in the past^1,2. A common combiner scheme consists of a diffraction grating that couples light in and out of a planar waveguide. This combiner is durable, relatively easy to manufacture, and can project high-resolution images. Projecting a full color image, however, is challenging due to large chromatic aberrations, and requires more complex design schemes. In this work, we present an optical combiner, which is based on a planar waveguide with embedded multilayered plasmonic metasurfaces, serving as achromatic diffractive grating couplers. The multilayered metasurface grating couplers are ultra-thin (<500nm) and highly transparent (∼90%). We fabricated 1mmX1mm metasurface based gratings using a standard E-beam lithography technique. The grating is designed to diffract only a specific wavelength range in the visible spectrum. Thus, it is possible to stack three layers of such metasurface gratings and couple a full color (RGB) image into a single waveguide, while compensating for the inherent chromatic dispersion of diffractive grating couplers.