CN-121995566-A - Diffraction optical device

CN121995566ACN 121995566 ACN121995566 ACN 121995566ACN-121995566-A

Abstract

A diffractive optical device includes a waveguide, a light emitting unit, and a metasurface. The waveguide includes a first lateral surface and a second lateral surface opposite the first lateral surface. The light emitting unit is in direct contact with the first lateral surface of the waveguide and is configured to emit a light beam having an initial divergence angle, wherein the light emitting unit comprises a light source. The metasurface is disposed on a second lateral surface of the waveguide, wherein the metasurface is configured to couple the light beam out of the waveguide and to project an optical pattern on a projection plane, wherein the optical pattern comprises negative-order diffracted light. The light emitting unit of the diffractive optical device of the present disclosure directly contacts the lateral surface of the waveguide, so the thickness of the diffractive optical device can be reduced to hundreds of micrometers, and thus the continuously shrinking diffractive optical device can be satisfied.

Inventors

WANG HUAIYONG
FU BAIHAN
XIE JINQUAN

Assignees

采钰科技股份有限公司

Dates

Publication Date: 20260508
Application Date: 20250311
Priority Date: 20241106

Claims (13)

1. A diffractive optical device, comprising: a waveguide comprising a first lateral surface and a second lateral surface opposite the first lateral surface; a light emitting unit directly contacting the first lateral surface of the waveguide and configured to emit a light beam having an initial divergence angle, wherein the light emitting unit comprises a light source, and A metasurface disposed on the second lateral surface of the waveguide, wherein the metasurface is configured to couple the light beam out of the waveguide and to project an optical pattern on a projection plane, wherein the optical pattern comprises a negative-order diffracted light.
2. The diffractive optical device recited in claim 1, wherein the light source comprises a vertical cavity surface emitting laser or a light emitting diode, and the waveguide comprises a planar waveguide or a curved waveguide.
3. The diffractive optical device recited in claim 1, wherein the light-emitting unit further comprises a surface relief grating disposed between the light source and the waveguide, the surface relief grating directly contacting the first lateral surface of the waveguide, and an initial exit angle (θ 0 ) of the light beam within the waveguide is not 0 degrees, wherein the initial exit angle is defined by an angle between a center line of the light beam and a normal to the first lateral surface, Wherein the light beam is tilted with respect to a normal to the second lateral surface of the waveguide before being coupled out of the waveguide, and the optical pattern comprises-1 st order diffracted light to-5 th order diffracted light.
4. The diffractive optical device recited in claim 3, wherein the surface relief grating comprises a plurality of sloped structures, the metasurface comprises a plurality of posts, and the plurality of posts are arranged in an asymmetric manner.
5. The diffractive optical device recited in claim 3, wherein the waveguide further comprises an anti-reflection layer adjacent to the metasurface, and the anti-reflection layer is perpendicular to the first lateral surface and the second lateral surface.
6. The diffractive optical device recited in claim 3, wherein an incident angle of the light beam, the initial divergence angle of the light beam, and a refractive index of the waveguide satisfy the following equations: Wherein θ i is the angle of incidence of the light beam, defined by an angle between the center line of the light beam and the normal to the first lateral surface of the waveguide after a total internal reflection of the light beam within the waveguide, β is the initial divergence angle of the light beam, n is the refractive index of the waveguide, the refractive index of the waveguide is greater than 1, and the angle of incidence (θ i ) is equal to the initial exit angle (θ 0 ).
7. The diffractive optical device recited in claim 1, wherein an initial exit angle of the light beam within the waveguide is 0 degrees, the initial exit angle being defined by an angle between a center line of the light beam and a normal to the first lateral surface of the waveguide, wherein the waveguide further comprises: A mirror adjacent to the light source, wherein the mirror is configured to change an angle of incidence of the light beam for total internal reflection within the waveguide, the mirror connects the first lateral surface and the second lateral surface and is tilted with respect to the first lateral surface of the waveguide, and An anti-reflection layer adjacent to the metasurface, wherein the anti-reflection layer is perpendicular to the first lateral surface and the second lateral surface.
8. The diffractive optical device recited in claim 7, wherein a tilt angle of the mirror is based on the following equation: 2θ slope ＝θ i , Where θ slope is the tilt angle of the mirror, θ slope is defined by an angle between the mirror of the waveguide and the first lateral surface of the waveguide, θ i is an angle of incidence of the light beam on the first lateral surface of the waveguide, and θ i is defined by an angle between the center line of the light beam and the normal to the first lateral surface of the waveguide after a total internal reflection of the light beam within the waveguide.
9. The diffractive optical device recited in claim 7, wherein a tilt angle of the mirror, the initial divergence angle of the beam, and a refractive index of the waveguide satisfy the following equation: Where θ slope is the tilt angle of the mirror, θ slope is defined by an angle between the mirror of the waveguide and the first lateral surface of the waveguide, β is the initial divergence angle of the light beam, and n is the refractive index of the waveguide.
10. The diffractive optical device recited in claim 7, wherein a thickness of the waveguide is based on the following equation: H waveguide ＝W source ×tan(θ slope ), Where H waveguide is the thickness of the waveguide, W source is a width of the light source, θ slope is an angle of inclination of the mirror, and θ slope is defined by an angle between the mirror of the waveguide and the first lateral surface of the waveguide.
11. The diffractive optical device recited in claim 1, wherein an initial exit angle of the light beam within the waveguide is 0 degrees, the initial exit angle being defined by an angle between a center line of the light beam and a normal to the first lateral surface of the waveguide, wherein the waveguide further comprises: A first mirror adjacent to the light source, wherein the first mirror is configured to transmit the light beam in parallel within the waveguide, the first mirror connects the first lateral surface and the second lateral surface, and the first mirror is tilted with respect to the first lateral surface of the waveguide, and A second mirror adjacent to the metasurface, wherein the second mirror is configured to change an angle of incidence of the light beam on the second lateral surface of the waveguide to 0 degrees, the angle of incidence of the light beam on the second lateral surface being defined by an angle between a normal to the second lateral surface and the centerline of the light beam on the second lateral surface, the second mirror connecting the first lateral surface and the second lateral surface, and the second mirror being tilted with respect to the first lateral surface of the waveguide, wherein the first mirror is parallel to the second mirror.
12. The diffractive optical device recited in claim 11, wherein a thickness of the waveguide is based on the following equation: H waveguide ＝W source ×tan(θ slope ), Where H waveguide is the thickness of the waveguide, W source is a width of the light source, θ slope is an inclination angle of the first mirror, θ slope is defined by an angle between the first mirror of the waveguide and the first lateral surface of the waveguide, and θ slope is 45 degrees.
13. The diffractive optical device recited in claim 12, wherein the light beam is perpendicular to the second lateral surface of the waveguide before the light beam is coupled out of the waveguide, and the optical pattern further comprises zero order diffracted light, ±1 order diffracted light, and ±2 order diffracted light.

Description

Diffraction optical device Technical Field The present disclosure relates to diffractive optical devices, and more particularly to diffractive optical devices that couple out negative-order diffracted light. Background Conventional metaoptics (meta optical element; MOE) or diffractive optics (DIFFRACTIVE OPTICAL ELEMENT; DOE) systems typically require a certain focal length between the light source and the waveguide to achieve diffraction, and thus conventional diffractive optics have a certain thickness, e.g., hundreds of millimeters. However, the conventional diffractive optical device cannot meet the requirement of the ever shrinking diffractive optical device. Therefore, a diffractive optical device is required to solve the above-mentioned problems. Disclosure of Invention The present disclosure provides a diffractive optical device having a waveguide, a light emitting unit, and a metasurface, wherein the light emitting unit directly contacts a lateral surface of the waveguide such that a light beam can be transmitted within the waveguide by total internal reflection and then coupled out through the metasurface. Because the light emitting units of the present disclosure directly contact the lateral surface of the waveguide, the thickness of the diffractive optical device can be reduced to hundreds of microns as compared to conventional MOE or DOE systems. Therefore, the diffractive optical device of the present disclosure can satisfy the ever shrinking diffractive optical devices. One embodiment of the present disclosure provides a diffractive optical device. The diffractive optical device includes a waveguide, a light emitting unit, and a metasurface. The waveguide includes a first lateral surface and a second lateral surface opposite the first lateral surface. The light emitting unit is in direct contact with the first lateral surface of the waveguide and is configured to emit a light beam having an initial divergence angle, wherein the light emitting unit comprises a light source. The metasurface is disposed on a second lateral surface of the waveguide, wherein the metasurface is configured to couple the light beam out of the waveguide and to project an optical pattern on a projection plane, wherein the optical pattern comprises negative-order diffracted light. According to some embodiments of the disclosure, the light source comprises a vertical cavity surface emitting laser or a light emitting diode. According to some embodiments of the disclosure, the waveguide comprises a planar waveguide or a curved waveguide. According to some embodiments of the present disclosure, the light emitting unit further comprises a surface relief grating disposed between the light source and the waveguide, the surface relief grating directly contacting the first lateral surface of the waveguide, and an initial exit angle (θ 0) of the light beam within the waveguide is not 0 degrees, wherein the initial exit angle is defined by an angle between a centerline of the light beam and a normal to the first lateral surface of the waveguide. According to some embodiments of the present disclosure, the surface relief grating comprises a plurality of tilted structures. According to some embodiments of the disclosure, the waveguide further comprises an anti-reflective layer adjacent to the metasurface, and the anti-reflective layer is substantially perpendicular to the first lateral surface and the second lateral surface. According to some embodiments of the present disclosure, the incident angle of the light beam, the initial divergence angle of the light beam, and the refractive index of the waveguide satisfy the following equations: Where θ i is the angle of incidence of the light beam, the angle of incidence (θ i) is defined by the angle between the centerline of the light beam and the normal to the first lateral surface of the waveguide after a total internal reflection of the light beam within the waveguide, β is the initial angle of divergence of the light beam, n is the refractive index of the waveguide, the refractive index of the waveguide is greater than 1, and the angle of incidence (θ i) is equal to the initial angle of emergence (θ 0). According to some embodiments of the present disclosure, the light beam is tilted with respect to a normal to a second lateral surface of the waveguide before the light beam is coupled out of the waveguide, and the optical pattern comprises-1 st order diffracted light to-5 th order diffracted light. According to some embodiments of the disclosure, the metasurface comprises a plurality of posts, and the plurality of posts are arranged in an asymmetric manner. According to some embodiments of the present disclosure, an initial exit angle of the light beam within the waveguide is 0 degrees, the initial exit angle being defined by an angle between a centerline of the light beam and a normal to a first lateral surface of the waveguide, wherein the waveguide further comprises a mirror and a