WAVEGUIDE FOR TRANSMITTING LIGHT

An optical device includes a stack that includes a first curved optical element stacked with a second curved optical element. The second curved optical element propagates light by total internal reflection. The stack also includes an incoupling diffractive grating that incouples the light into the second optical element and an outcoupling diffractive grating optically coupled to the incoupling diffractive grating through the second curved optical element. The outcoupling diffractive grating directs the light. The first curved optical element has a first refractive index, the second curved optical element has a second refractive index, and the first refractive index is different from the second refractive index by approximately 0.15 to 1.2.