See-through reflective metasurface diffraction grating

Metal-dielectric reflective metasurfaces with an engineered phase response provide a versatile alternative to conventional optics, especially when wanting to defy the basic law of reflection, as in compact near-eye display systems for augmented reality applications. Specifically, a key component of these display systems is a reflective grating with see-through function or capability. For a reflective metasurface, the transmission regime is typically not allowed due to a non-transparent metal backplate. In the current work, we propose a method to enable see-through metal-dielectric metasurfaces by etching apertures of random position and diameter (RPD) much larger than the design wavelength of the metasurfaces. We demonstrate a 1200 lp/mm metal-dielectric metasurface diffraction grating for use in reflection with 650 nm illumination. The fabricated device shows ∼20% diffraction efficiency in the first diffractive order over 0-50° angle of incidence, which is in agreement with the electromagnetic simulations. The device 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 (rings, fringes, etc.) aside from a quasi-uniform halo.