Optical waveguide structure and augmented reality display device

An augmented reality (AR) display device, comprising:

• a display panel configured to emit image light;
• and
• an optical waveguide structure configured to receive the image light, the optical waveguide structure comprising:
• a first waveguide comprising a first surface and a second surface opposite to each other, the first waveguide configured to guide a first sub-image light within a first wavelength range of the image light along a first direction;
• a first in-coupling grating on the first surface and configured to couple the first sub-image light into the first waveguide;
• and
• a first out-coupling grating on the first surface and spaced apart from the first in-coupling grating along the first direction, the first out-coupling grating configured to couple the first sub-image light out of the first waveguide;
• wherein a grating direction of the first in-coupling grating has a first angle θ1 relative to the first direction, a grating direction of the first out-coupling grating has a second angle θ2 relative to the first direction, each of the first angle θ1 and the second angle θ2 is non-zero, and the grating direction of the first in-coupling grating is opposite to the grating direction of the first out-coupling grating.