Design of achromatic surface microstructure for near-eye display with diffractive waveguide

TL;DR

This paper introduces an achromatic surface microstructure with a triple-carved-sub-grating for near-eye displays, effectively addressing dispersion issues and enabling compact, efficient RGB wavelength diffraction.

Contribution

A novel design method for an achromatic microstructure using triple-carved-sub-gratings based on rigorous coupled wave theory, achieving high diffraction efficiency across RGB wavelengths.

Findings

Diffraction efficiencies of 47.5% for RGB wavelengths.

Achromatic diffraction angles of 35 degrees for RGB.

Crosstalk less than 4.5% under normal TE polarization.

Abstract

Dispersion problem has always constrained the development of see-through near-eye displays with diffractive waveguide. Here, we propose a design method and optical systems for achromatic surface microstructure composed with a triple-carved-sub-grating. The triple-carved-sub-grating with specified period is designed based on rigorous coupled wave theory, corresponding to Red, Green and Blue (RGB) wavelengths, respectively, with diffraction efficiencies of 1st(-1st) orders reach 47.5% under TE polarization. The surface microstructure with period of 18.9um is realized by integrating the three sub-gratings together, and it is verified numerically that the diffractive angle of RGB wavelengths is 35{\deg} and the crosstalk is less than 4.5% under the normal incidence of TE polarization, which imply the surface microstructure diffracts the certain RGB wavelengths achromatically. Via proper duplication it could be utilized as the combining optics of diffractive-waveguide near-eye display and head-up display because of its light and compact features.