Abstract: A device is provided. The device includes a waveguide configured to guide an image light to propagate from a light inputting surface to a light outputting surface. The waveguide includes a substrate having a back surface facing an eye-box region of the device and a front surface opposite to the back surface, a plurality of out-coupling structures disposed at the back surface or at least partially inside the substrate, and a medium layer embedded inside the substrate between the out-coupling structures and the front surface. The medium layer has a refractive index that is lower than the substrate. The device also includes an optical lens printed over the back surface of the substrate.