Abstract: Disclosed herein are techniques for waveguide displays. According to some embodiments, a method for fabricating a multi-layer optical device comprising includes measuring thickness variations within a target area of a first substrate for fabricating a first optical element of the multi-layer optical device and determining, based on the measuring, a thickness correction map indicating amounts of material to be removed in different regions of the target area to planarize the target area. The method also includes planarizing the target area of the first substrate based on the thickness correction map and bonding the first substrate to a second substrate that comprises a second optical element fabricated thereon to form a layer stack, wherein the target area of the first substrate aligns with and is bonded to the second optical element to form a multi-layer structure. The method further includes singulating the multi-layer structure from the layer stack.

Abstract: A bilayer binary 2D surface relief grating includes a primary grating layer having an array of primary grating elements, and a secondary grating layer having an array of secondary grating elements overlying the primary grating layer, where the secondary grating elements are at least partially laterally offset from the primary grating elements. A method of manufacturing such a surface relief grating includes forming a low refractive index layer over a substrate, the low refractive index layer including a primary sub-layer having an array of primary openings and a secondary sub-layer overlying the primary sub-layer and having an array of secondary openings, where the secondary openings are at least partially laterally offset from the primary openings, and forming a high refractive index layer within the primary and secondary openings.

Abstract: One or more optical resonators are coupled to an optical waveguide in sequence. Each of the resonators includes a corresponding modulator. A signal controller is configured to electrically drive each modulator with a corresponding composite electrical signal. Each composite electrical signal includes two or more frequency components of a frequency comb defined by the one or more resonators. The result of this configuration is that an input-output relation between an input of the waveguide and an output of the waveguide is a linear transformation defined by the composite electrical signals using frequencies of the frequency comb as a basis. Such linear transformations can be reciprocal or non-reciprocal, unitary or non-unitary.

Abstract: An output grating for waveguide of a head-mounted display is configured to suppress the (1, 1) diffraction order of the output grating. The grating has a design of two or more materials having different refractive indices. The design is repeated periodically in a first dimension and repeated periodically in a second dimension, to form a two-dimensional pattern. A refractive index of the two-dimensional pattern is approximated by a two-dimensional Fourier series comprising a first coefficient of order (1, 0), a second coefficient of order (0, 1), and a third coefficient of order (1, 1). The third coefficient is less than half the first coefficient and less than half the second coefficient, such that light from the (1, 1) diffraction order of the grating is suppressed.

Abstract: A pupil-replicating waveguide includes a high-index substrate and a low-index substrate coupled by an intermediate layer between the substrates. The refractive index of the intermediate layer is lower than the refractive index of the low-index substrate. The intermediate layer prevents highly oblique rays of image light from entering the low-index substrate, thereby reducing intensity drops in the field of view conveyed by the pupil-replicating waveguide, the intensity drops caused by insufficient replication of the highly oblique rays in the low-index substrate.

Abstract: A diffraction grating includes a substrate and a plurality of fringes supported by the substrate. The fringes run parallel to each other in a first direction. A refractive index of a material of the plurality of fringes is anisotropic, whereby a refractive index contrast of the diffraction grating depends on direction of electric field of an impinging light beam, and through that dependence is a function of an azimuthal angle of the impinging light beam. A dependence of the diffraction efficiency on the azimuthal angle is affected by the dependence of the refractive index contrast on the direction of electric field of an impinging light beam. A pupil-replicating waveguide may use such a diffraction grating as a coupler for in- our out-coupling image light.

Abstract: A pupil-replicating waveguide includes a high-index substrate and a low-index substrate coupled by an intermediate layer between the substrates. The refractive index of the intermediate layer is lower than the refractive index of the low-index substrate. The intermediate layer prevents highly oblique rays of image light from entering the low-index substrate, thereby reducing intensity drops in the field of view conveyed by the pupil-replicating waveguide, the intensity drops caused by insufficient replication of the highly oblique rays in the low-index substrate.

Abstract: A diffraction grating includes a substrate and a plurality of fringes supported by the substrate. The fringes run parallel to each other in a first direction. A refractive index of a material of the plurality of fringes is anisotropic, whereby a refractive index contrast of the diffraction grating depends on direction of electric field of an impinging light beam, and through that dependence is a function of an azimuthal angle of the impinging light beam. A dependence of the diffraction efficiency on the azimuthal angle is affected by the dependence of the refractive index contrast on the direction of electric field of an impinging light beam. A pupil-replicating waveguide may use such a diffraction grating as a coupler for in- our out-coupling image light.