US-20260126572-A1 - DIFFRACTIVE OPTICAL DEVICE

US20260126572A1US 20260126572 A1US20260126572 A1US 20260126572A1US-20260126572-A1

Abstract

A diffractive optical structure includes a waveguide, a light emitting unit, and a metasurface. The waveguide includes a first transverse surface and a second transverse surface opposite to the first transverse surface. The light emitting unit directly contacts the first transverse surface of the waveguide is configured to emit a light beam with an initial divergence angle, wherein the light emitting unit includes a light source. The metasurface is disposed on the second transverse surface of the waveguide, wherein the metasurface is configured to couple out the light beam from the waveguide and project an optical pattern on a plane, wherein the optical pattern includes a negative order diffracted light.

Inventors

Huai-Yung WANG
Po-Han FU
Chin-Chuan Hsieh

Assignees

VISERA TECHNOLOGIES COMPANY LTD.

Dates

Publication Date: 20260507
Application Date: 20241106

Claims (20)

1 . A diffractive optical device, comprising: a waveguide comprising a first transverse surface and a second transverse surface opposite to the first transverse surface; a light emitting unit directly contacting the first transverse surface of the waveguide configured to emit a light beam with an initial divergence angle, wherein the light emitting unit comprises a light source and; and a metasurface disposed on the second transverse surface of the waveguide, wherein the metasurface is configured to couple out the light beam from the waveguide and project an optical pattern on a plane, wherein the optical pattern comprises a negative order diffracted light.
2 . The diffractive optical device of claim 1 , wherein the light source comprises a vertical cavity surface emitting laser or a light emitting diode.
3 . The diffractive optical device of claim 1 , wherein the waveguide comprises a planar waveguide or a curved waveguide.
4 . The diffractive optical device of claim 1 , wherein the light emitting unit further comprises a surface relief grating, the surface relief grating is disposed between the light source and the waveguide and directly contacts the first transverse surface of the waveguide, and an initial emergent angle (θ 0 ) of the light beam in the waveguide is not 0 degree, wherein the initial emergent angle is defined by an included angle between a center line of the light beam and a normal line of the first transverse surface.
5 . The diffractive optical device of claim 4 , wherein the surface relief grating comprises a plurality of slanted structures.
6 . The diffractive optical device of claim 4 , wherein the waveguide further comprises an anti-reflection layer adjacent to the metasurface, and the anti-reflection layer is substantially perpendicular to both the first transverse surface and the second transverse surface.
7 . The diffractive optical device of claim 4 , 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 equitation: θ i - β 2 ≥ sin - 1 ( 1 n ) , wherein θ i is the incident angle of the light beam, the incident angle is defined by an included angle between a center line of the light beam and the normal line of the first transverse surface of the waveguide after the light beam occurs once total internal reflection in 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 incident angle (θ i ) is the same as the initial emergent angle (θ 0 ).
8 . The diffractive optical device of claim 4 , wherein the light beam is inclined relative to a normal line of the second transverse surface of the waveguide before coupling out from the waveguide, and the optical pattern comprises from −1 st to −5 th order diffracted lights.
9 . The diffractive optical device of claim 4 , wherein the metasurface comprises a plurality of pillars, and the pillars are arranged in asymmetric.
10 . The diffractive optical device of claim 1 , wherein an initial emergent angle of the light beam in the waveguide is 0 degree, and the initial emergent angle is defined by an included angle between a center line of the light beam and a normal line of the first transverse surface of the waveguide, wherein the waveguide further comprises: a mirror adjacent to the light source, wherein the mirror is configured to change an incident angle of the light beam for a total internal reflection in the waveguide, the mirror connects the first transverse surface and the second transverse surface, and the mirror is inclined relative to the first transverse surface of the waveguide; and an anti-reflection layer adjacent to the metasurface, wherein the anti-reflection layer is substantially perpendicular to both the first transverse surface and the second transverse surface.
11 . The diffractive optical device of claim 10 , wherein an inclined angle of the mirror is based on the following equation: 2 ⁢ θ slope = θ i , wherein θ slope is the inclined angle of the mirror, θ slope is defined by an included angle between the mirror of the waveguide and the first transverse surface of the waveguide, θ i is an incident angle of the light beam on the first transverse surface of the waveguide, and θ i is defined by an included angle between the center line of the light beam and the normal line of first transverse surface of the waveguide after the light beam occurs once total internal reflection in the waveguide.
12 . The diffractive optical device of claim 10 , wherein an inclined angle of the mirror, the initial divergence angle of the light beam, and a refractive index of the waveguide satisfy the following equitation: 2 ⁢ θ slope - β 2 ≥ sin - 1 ( 1 n ) , wherein θ slope is the inclined angle of the mirror, θ slope is defined by an included angle between the mirror of the waveguide and the first transverse surface of the waveguide, B is the initial divergence angle of the light beam, and n is the refractive index of the waveguide.
13 . The diffractive optical device of claim 12 , wherein the refractive index of the waveguide is greater than 1.
14 . The diffractive optical device of claim 10 , wherein a thickness of the waveguide is based on the following equation: H waveguide = W source × tan ⁡ ( θ slope ) , wherein H waveguide is the thickness of the waveguide, W source is a width of the light source, θ slope is an inclined angle of the mirror, θ slope is defined by an included angle between the mirror of the waveguide and the first transverse surface of the waveguide.
15 . The diffractive optical device of claim 10 , wherein the light beam is inclined relative to a normal line of the second transverse surface of the waveguide before coupling out from the waveguide, and the optical pattern comprises from −1 st to −5 th order diffracted lights.
16 . The diffractive optical device of claim 10 , wherein the metasurface comprises a plurality of pillars, and the pillars are arranged in asymmetric.
17 . The diffractive optical device of claim 1 , wherein an initial emergent angle of the light beam in the waveguide is 0 degree, and the initial emergent angle is defined by an included angle between a center line of the light beam and a normal line of the first transverse 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 parallel in the waveguide, the first mirror connects the first transverse surface and the second transverse surface, and the first mirror is inclined relative to the first transverse surface of the waveguide; and a second mirror adjacent to the metasurface, wherein the second mirror is configured to change an incident angle of the light beam on the second transverse surface in the waveguide to 0 degree, the incident angle of the light beam on the second transverse surface is defined by an included angle between a normal line of the second transverse surface and the center line of the light beam on the second transverse surface, the second mirror connects the first transverse surface and the second transverse surface, and the second mirror is inclined relative to the first transverse surface of the waveguide, wherein the first mirror is parallel to the second mirror.
18 . The diffractive optical device of claim 17 , wherein a thickness of the waveguide is based on the following equation: H waveguide = W source × tan ⁡ ( θ slope ) , wherein H waveguide is the thickness of the waveguide, W source is a width of the light source, θ slope is an inclined angle of the mirror, θ slope is defined by an included angle between the mirror of the waveguide and the first transverse surface of the waveguide, and θ slope is 45 degrees.
19 . The diffractive optical device of claim 18 , wherein the light beam is perpendicular to the second transverse surface of the waveguide before coupling out from the waveguide, and the optical pattern further comprises a zero order diffracted light, ±1 order diffracted lights, and ±2 order diffracted lights.
20 . The diffractive optical device of claim 18 , wherein a refractive index of the waveguide is greater than 1, the metasurface comprises a plurality of pillars, and the pillars are arranged in symmetric.

Description

BACKGROUND Field of Invention The present disclosure relates to a diffractive optical device. More particularly, the present disclosure relates to the diffractive optical device coupling out a negative order diffracted light. Description of Related Art A traditional meta optical element (MOE) or diffractive optical element (DOE) system usually needs a certain focal length between a light source and a waveguide to achieve diffraction, so the traditional diffractive optical device has a certain thickness, for example, hundreds of millimeters. However, traditional diffractive optical device cannot satisfy continuously shrinking diffractive optical devices. Therefore, there is a need to solve the above problems. SUMMARY The present disclosure provides a diffractive optical device having a waveguide, a light emitting unit, and a metasurface, in which the light emitting unit directly contacts a transverse surface of the waveguide, so that a light beam can travel in the waveguide by total internal reflection before coupling out through the metasurface. Since the light emitting unit directly contacts the transverse surface of the waveguide, a thickness of the disclosed diffractive optical device can be reduced compared to the traditional MOE or DOE system. Therefore, the disclosed diffractive optical device can satisfy continuously shrinking diffractive optical devices. One aspect of the present disclosure is to provide a diffractive optical device. The diffractive optical device includes a waveguide, a light emitting unit, and a metasurface. The waveguide includes a first transverse surface and a second transverse surface opposite to the first transverse surface. The light emitting unit directly contacts the first transverse surface of the waveguide configured to emit a light beam with an initial divergence angle, wherein the light emitting unit includes a light source. The metasurface is disposed on the second transverse surface of the waveguide, wherein the metasurface is configured to couple out the light beam from the waveguide and project an optical pattern on a plane, wherein the optical pattern includes a negative order diffracted light. According to some embodiments of the present disclosure, the light source includes a vertical cavity surface emitting laser or a light emitting diode. According to some embodiments of the present disclosure, the waveguide includes a planar waveguide or a curved waveguide. According to some embodiments of the present disclosure, the light emitting unit further includes a surface relief grating, the surface relief grating is disposed between the light source and the waveguide and directly contacts the first transverse surface of the waveguide, and an initial emergent angle (θ0) of the light beam in the waveguide is not 0 degree, wherein the initial emergent angle is defined by an included angle between a center line of the light beam and a normal line of the first transverse surface of the waveguide. According to some embodiments of the present disclosure, the surface relief grating includes a plurality of slanted structures. According to some embodiments of the present disclosure, the waveguide further includes an anti-reflection layer adjacent to the metasurface, and the anti-reflection layer is substantially perpendicular to both the first transverse surface and the second transverse surface. According to some embodiments of the present disclosure, 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 equitation: θi-β2≥sin-1(1n), wherein θi is the incident angle of the light beam, the incident angle (θi) is defined by an included angle between a center line of the light beam and the normal line of the first transverse surface of the waveguide after the light beam occurs once total internal reflection in the waveguide, B 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 incident angle (θi) is the same as the initial emergent angle (θ0). According to some embodiments of the present disclosure, the light beam is inclined relative to a normal line of the second transverse surface of the waveguide before coupling out from the waveguide, and the optical pattern includes from −1st to −5th order diffracted lights. According to some embodiments of the present disclosure, the metasurface includes a plurality of pillars, and the pillars are arranged in asymmetric. According to some embodiments of the present disclosure, an initial emergent angle of the light beam in the waveguide is 0 degree, and the initial emergent angle is defined by an included angle between a center line of the light beam and a normal line of the first transverse surface of the waveguide, wherein the waveguide further includes a mirror and an anti-reflection layer. The mirror is adjacent to the light source, wher