An optical composite film comprises a reflective grating film layer, a first uniaxial optical film layer, and a second uniaxial optical film layer. The first uniaxial optical film layer comprises a plate portion and a plurality of refraction portions. The plate portion is disposed on the reflective grating film layer. The plurality of refraction portions are disposed on a side of the plate portion away from the reflective grating film layer, and are either curved columns or quadrangular prisms. The second uniaxial optical film layer is laminated on a side of the plate portion adjacent to the refraction portions. The plurality of refraction portions are accommodated in the second uniaxial optical film layer. The second uniaxial optical film layer has an ordinary refractive index less than an extraordinary refractive index of the first uniaxial optical film layer.

In various embodiments, laser devices include a thermal bonding layer featuring an array of carbon nanotubes and at least one metallic thermal bonding material.

In various embodiments, laser devices include a thermal bonding layer featuring an array of carbon nanotubes and at least one metallic thermal bonding material.

A diffractive optical element includes: a diffraction unit; and a lens unit disposed on a light incident side of the diffraction unit. The lens unit includes: a substrate; and a protrusion and recess portion disposed on a side opposite to a light incident side of the substrate. The protrusion and recess portion includes: a periodic structure of a relief-protrusion portion disposed in a central part, a periodic structure of a stepwise grating disposed in a central part simulating the relief-protrusion portion, or a combination thereof; and a grating disposed in a portion other than the central part. The number of steps of the stepwise grating disposed in the central part is larger than the number of steps of the grating disposed in the portion other than the central part.

A diffractive optical element includes: a diffraction unit; and a lens unit disposed on a light incident side of the diffraction unit. The lens unit includes: a substrate; and a protrusion and recess portion disposed on a side opposite to a light incident side of the substrate. The protrusion and recess portion includes: a periodic structure of a relief-protrusion portion disposed in a central part, a periodic structure of a stepwise grating disposed in a central part simulating the relief-protrusion portion, or a combination thereof; and a grating disposed in a portion other than the central part. The number of steps of the stepwise grating disposed in the central part is larger than the number of steps of the grating disposed in the portion other than the central part.

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.

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.

A structured light system may include a semiconductor laser to emit light and a diffractive optical element to diffract the light such that one or more diffracted orders of the light, associated with forming a structured light pattern, are transmitted by the diffractive optical element. The diffractive optical element may be arranged such that the light is to be incident on the diffractive optical element at a substantially non-normal angle of incidence. The substantially non-normal angle of incidence may be designed to cause the diffractive optical element to transmit a zero-order beam of the light outside of a field of view associated with the diffractive optical element.

A display apparatus including a volume grating-based combiner is disclosed. The display apparatus includes: an image providing device; and a combiner, wherein the combiner includes a plurality of volume gratings configured to diffract light containing an image, which is emitted from the image providing device, each volume grating has a first surface and a second surface facing each other, and each volume grating is further configured to diffract light incident on the first surface and transmit therethrough light incident on the second surface without diffraction.

A display apparatus including a volume grating-based combiner is disclosed. The display apparatus includes: an image providing device; and a combiner, wherein the combiner includes a plurality of volume gratings configured to diffract light containing an image, which is emitted from the image providing device, each volume grating has a first surface and a second surface facing each other, and each volume grating is further configured to diffract light incident on the first surface and transmit therethrough light incident on the second surface without diffraction.