An eyepiece for projecting an image to an eye of a viewer includes a waveguide configured to propagate light in a first wavelength range, and a grating coupled to a back surface of the waveguide. The grating is configured to diffract a first portion of the light propagating in the waveguide out of a plane of the waveguide toward a first direction, and to diffract a second portion of the light propagating in the waveguide out of the plane of the waveguide toward a second direction opposite to the first direction. The eyepiece furthers include a wavelength-selective reflector coupled to a front surface of the waveguide. The wavelength selective reflector is configured to reflect light in the first wavelength range and transmit light outside the first wavelength range, such that the wavelength-selective reflector reflects at least part of the second portion of the light back toward the first direction.

An eyepiece includes a planar waveguide having a front surface and a back surface. The eyepiece also includes a grating coupled to the back surface of the planar waveguide and configured to diffract a first portion of the light propagating in the planar waveguide out of a plane of the planar waveguide toward a first direction and to diffract a second portion of the light propagating in the planar waveguide out of the plane of the planar waveguide toward a second direction opposite to the first direction and a wavelength-selective reflector coupled to the front surface of the planar waveguide. The wavelength-selective reflector comprises a multilevel metasurface comprising a plurality of spaced apart protrusions having a pitch and formed of a first optically transmissive material and a second optically transmissive material disposed between the spaced apart protrusions.

Various embodiments and configurations of optical imaging systems are described herein that utilize a metalens for narrowband deflection of target frequencies. For example, one embodiment of a multifrequency metalens includes an in-plane spatially multiplexed array of frequency-specific nanopillars or frequency-specific rows/columns of nanopillars that are intermingled with one another. In other embodiments, transmissive metalenses and/or reflective metalenses are tuned to focus color-separated visible light into red, green, and blue (RGB) channels of a digital image sensor.

A hologram element for broadband shaping of electromagnetic waves and a related system are disclosed. The hologram element has a dispersive surface with a surface height profile that is configured to spatially modulate at least one of an amplitude or a phase of transmitted electromagnetic waves having a bandwidth defined by a start frequency f.sub.1 and a stop frequency f.sub.2. The surface height profile is further configured to maximize a rate of one of a phase shift or a delay variation at said bandwidth via steps comprised in the dispersive surface, each step having a step height the electrical length of which is a multiple of N+q wavelengths at the start frequency f.sub.1 and M multiple of wavelengths at the stop frequency f.sub.2.

An eyepiece for use in front of an eye of a viewer includes a waveguide configured to propagate light therein, and a diffractive optical element optically coupled to the waveguide. The diffractive optical element includes a plurality of first ridges protruding from a surface of the waveguide. Each of the plurality of first ridges has a first height and a first width. The diffractive optical element further includes a plurality of second ridges. Each of the plurality of second ridges protrudes from a respective first ridge and has a second height greater than the first height and a second width less than the first width. The diffractive optical element is configured to diffract a portion of a light beam incident on the diffractive optical element toward the eye as a first order transmission.

An optical assembly may include a waveguide and a Bragg grating configured to couple light into or out of the waveguide. The Bragg grating may include a plurality of layer pairs, wherein at least one layer pair comprises a first material having a first refractive index and a second layer having a second refractive index, and wherein properties of the Bragg grating are selected so that the Bragg grating exhibits a substantially similar diffractive efficiency and diffraction angle for light of at least two colors.

A rainbow-free waveguide display, a near-eye display incorporating the rainbow-free waveguide, and methods of manufacturing the rainbow-free waveguide are provided. The display includes a waveguide display configured to direct image light to an eyebox plane having a length (L.sub.Eyebox) and to a user's eye. The waveguide display includes a waveguide combiner and an out-coupler grating, wherein the out-coupler grating has a grating period Λ.sub.OC such that all angles of incidence θ.sub.in of light from an external light source, result in diffracted angles θ.sub.out, that miss the user's eye.

A light source device includes: a plurality of laser sources; a plurality of collimating parts, each configured to collimate the light beam emitted from a corresponding one of the laser sources; a combining grating configured to diffract, at an identical diffraction angle, light beams that have passed through the collimating parts and are incident on the combining grating at different incident angles to combine the diffracted light beams; and a plurality of volume holographic gratings, wherein each of the volume holographic gratings is disposed in an optical path between a corresponding one of the laser sources and the combining grating, wherein each of the volume holographic gratings determines a wavelength of the light beam incident on the combining grating, and wherein each of the volume holographic gratings is configured to diffract a portion of the light beam emitted from a corresponding laser source back to the laser source.

An optical structure includes a grating coupler and a microlens. The grating coupler is configured to receive a laser light. The microlens is above the grating coupler, in which a metal shielding covers the microlens and has an opening to allow the laser light entering an effective coupling region of the grating coupler.

An optical system includes a light module, an optical element on a first grating coupler, and a second grating coupler. The light module emits three beams from different positions. The optical element is below the light module and is configured to change incident angles of the three beams and to focus the three beams at the same region of the first grating coupler. The first grating coupler is below the optical element and is configured to couple the three beams into a light-guide substrate. The light-guide substrate is connected to the first grating coupler and is configured to transmit the three beams. The second grating coupler is connected to the light-guide substrate and is configured to enable the three beams departing from the light-guide substrate after the three beams have traveled the same optical path.