Display structure

A display structure comprising:

• a waveguide
• an in-coupling structure on a first side of the waveguide comprising diffractive grating features and sub-wavelength grating features, and configured to receive light comprising a first polarization and a second polarization, wherein the diffractive grating features are configured to couple at least part of the first polarization into the waveguide as in-coupled light and wherein the sub-wavelength grating features are configured to make the diffractive grating features at least partially transparent to the second polarization;
• and
• a polarization manipulating grating on a second side of the waveguide configured to receive at least a part of the in-coupled light, and to rotate the polarization of the in-coupled light, resulting in polarization-rotated in-coupled light, when the in-coupled light is reflected from the second side of the waveguide back towards the first side of the waveguide;
• wherein the diffractive grating features comprise a plurality of diffractive grating lines and the sub-wavelength grating features comprise a plurality sub-wavelength grating lines, the plurality of sub-wavelength grating lines are positioned between the plurality of diffractive grating lines, and the plurality of diffractive grating lines and the plurality of sub-wavelength grating lines are non-parallel.