Structures for a grating coupler and methods of fabricating a structure for a grating coupler. The structure includes a grating coupler having a central portion and edge portions. The central portion and the edge portions define a sidewall, and the central portion and the edge portions have a first longitudinal axis along which the edge portions are arranged in a spaced relationship. Each edge portion projects from the sidewall at an angle relative to the first longitudinal axis. A waveguide core is optically coupled to the grating coupler. The first longitudinal axis is aligned in a first direction, and the waveguide core has a second longitudinal axis that is aligned in a second direction different from the first direction.

Structures for a grating coupler and methods of fabricating a structure for a grating coupler. The structure includes a grating coupler having a central portion and edge portions. The central portion and the edge portions define a sidewall, and the central portion and the edge portions have a first longitudinal axis along which the edge portions are arranged in a spaced relationship. Each edge portion projects from the sidewall at an angle relative to the first longitudinal axis. A waveguide core is optically coupled to the grating coupler. The first longitudinal axis is aligned in a first direction, and the waveguide core has a second longitudinal axis that is aligned in a second direction different from the first direction.

A light guide member includes an incident portion, an emission portion, a reflection portion, and an inclined portion. An internal reflection angle inside the reflection portion and the emission portion is larger than an incident angle of an external light with respect to a first normal line that is a normal line of the emission portion. A first inclination angle that is an inclination angle of the incident portion with respect to the first normal line is smaller than the internal reflection angle. A height from the emission portion to a second side of the incident portion is larger than a distance between the emission portion and the reflection portion. A second inclination angle that is an inclination angle of the inclined portion with respect to the first normal line is smaller than the internal reflection angle.

A light guide member includes an incident portion, an emission portion, a reflection portion, and an inclined portion. An internal reflection angle inside the reflection portion and the emission portion is larger than an incident angle of an external light with respect to a first normal line that is a normal line of the emission portion. A first inclination angle that is an inclination angle of the incident portion with respect to the first normal line is smaller than the internal reflection angle. A height from the emission portion to a second side of the incident portion is larger than a distance between the emission portion and the reflection portion. A second inclination angle that is an inclination angle of the inclined portion with respect to the first normal line is smaller than the internal reflection angle.

To improve brightness of an image to be perceived by a user and enhance visibility there is provided a light guide plate including an incident diffraction grating which diffracts incident imaging light, an exit diffraction grating through which the imaging light goes out, and an intermediate diffraction grating existing in optical paths from the incident diffraction grating to the exit diffraction grating. In this light guide plate, a periodic linear corrugated pattern is formed as the incident diffraction grating, and when an imaginary line is established that passes through an incident point of imaging light onto the incident diffraction grating and is parallel with a periodic direction of the corrugated pattern, the intermediate diffraction grating has a first region on one side of the imaginary line and a second region on another side of the imaginary line.

A diffractive waveguide stack includes first, second, and third diffractive waveguides for guiding light in first, second, and third visible wavelength ranges, respectively. The first diffractive waveguide includes a first material having first refractive index at a selected wavelength and a first target refractive index at a midpoint of the first visible wavelength range. The second diffractive waveguide includes a second material having a second refractive index at the selected wavelength and a second target refractive index at a midpoint of the second visible wavelength range. The third diffractive waveguide includes a third material having a third refractive index at the selected wavelength and a third target refractive index at a midpoint of the third visible wavelength range. A difference between any two of the first target refractive index, the second target refractive index, and the third target refractive index is less than 0.005 at the selected wavelength.

An optical element includes a transparent layer, outcoupling elements, and a waveguide structure. The outcoupling elements are positioned across the transparent layer. The waveguide structure provides non-visible light to the outcoupling elements and the outcoupling elements outcouple the non-visible light as non-visible illumination light to illuminate an eye region.

An optical waveguide comprises at least two TIR surface and contains a grating. Input TIR light with a first angular range along a first propagation direction undergoes at least two diffractions at the grating. Each diffraction directs light into a unique TIR angular range along a second propagation direction.

An optical waveguide comprises at least two TIR surface and contains a grating. Input TIR light with a first angular range along a first propagation direction undergoes at least two diffractions at the grating. Each diffraction directs light into a unique TIR angular range along a second propagation direction.

Illuminations systems that separate different colors into laterally displaced beams may be used to direct different color image content into an eyepiece for displaying images in the eye. Such an eyepiece may be used, for example, for an augmented reality head mounted display. Illumination systems may be provided that utilize one or more waveguides to direct light from a light source towards a spatial light modulator. Light from the spatial light modulator may be directed towards an eyepiece. Some aspects of the invention provide for light of different colors to be outcoupled at different angles from the one or more waveguides and directed along different beam paths.