Example embodiments include an optical system comprising a waveguide substrate. A diffractive coupler is associated with the waveguide substrate, the diffractive coupler comprising at least two diffraction gratings. Each of the diffraction gratings includes a first layer of grating elements and a second layer of grating elements, the first and second layers of grating elements being arranged in different planes. The first and second layers of grating elements each have a grating period associated with the respective diffraction grating, and the grating elements of the second layer have a lateral offset with respect to the grating elements of the first layer.