Diffraction optical device
By directly contacting the light-emitting unit with the transverse surface of the waveguide in the diffraction optical device and utilizing total internal reflection and metasurface coupling technology, the problem of excessive thickness in traditional diffraction optical devices has been solved, and the device has been made thinner.
Patent Information
- Application Number
- CN202510282235.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-11-06
- Filing Date
- 2025-03-11
- Publication Date
- 2026-05-08
AI Technical Summary
Traditional diffraction optical devices are relatively thick because they need to maintain a certain focal length, which cannot meet the needs of continuous shrinkage.
Design a diffraction optical device in which the light-emitting unit directly contacts the transverse surface of the waveguide, the light beam is transmitted in the waveguide through total internal reflection and coupled out through the metasurface, thereby reducing the thickness of the device.
The thickness of the diffractive optical device has been reduced to several hundred micrometers, meeting the ever-shrinking requirements.
Smart Images
Figure CN121995566A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to a diffraction optical device, and more particularly to a diffraction optical device that couples out negative order diffraction light. Background Technology
[0002] Traditional meta-optical elements (MOEs) or diffractive optical elements (DOEs) typically require a certain focal length between the light source and the waveguide to achieve diffraction, thus traditional diffractive optical devices have a certain thickness, such as several hundred millimeters. However, traditional diffractive optical devices cannot meet the requirements of increasingly smaller diffractive optical devices. Therefore, a diffractive optical device is needed to solve the above problems. Summary of the Invention
[0003] This disclosure provides a diffraction optical device comprising a waveguide, a light-emitting unit, and a metasurface, wherein the light-emitting unit directly contacts the transverse surface of the waveguide, allowing the light beam to propagate within the waveguide via total internal reflection and then coupled out through the metasurface. Compared to conventional MOE or DOE systems, because the light-emitting unit of this disclosure directly contacts the transverse surface of the waveguide, the thickness of the diffraction optical device can be reduced to hundreds of micrometers. Therefore, the diffraction optical device of this disclosure can meet the needs of continuously shrinking diffraction optical devices.
[0004] One embodiment of this disclosure provides a diffraction optical device. The diffraction 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 and is configured to emit a light beam having 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 the light beam out of the waveguide and project an optical pattern onto a projection plane, wherein the optical pattern includes negative-order diffracted light.
[0005] According to some embodiments of this disclosure, the light source includes a vertical cavity surface-emitting laser or a light-emitting diode.
[0006] According to some embodiments of this disclosure, the waveguide includes a planar waveguide or a curved waveguide.
[0007] According to some embodiments of the present disclosure, the light-emitting unit further includes a surface relief grating disposed between the light source and the waveguide. The surface relief grating directly contacts the first transverse surface of the waveguide, and the initial exit angle (θ0) of the light beam in the waveguide is not 0 degrees, wherein the initial exit angle is defined by the angle between the centerline of the light beam and the normal of the first transverse surface of the waveguide.
[0008] According to some embodiments of this disclosure, the surface relief grating includes multiple tilted structures.
[0009] According to some embodiments of this disclosure, the waveguide further includes an antireflective layer adjacent to the metasurface, and the antireflective layer is substantially perpendicular to the first transverse surface and the second transverse surface.
[0010] According to some embodiments of this disclosure, the incident angle of the beam, the initial divergence angle of the beam, and the refractive index of the waveguide satisfy the following equations:
[0011]
[0012] Where θ i Let θ be the angle of incidence of the light beam. i The angle θ is defined as the angle between the centerline of the beam and the normal to the first transverse surface of the waveguide after the beam undergoes one total internal reflection within the waveguide, where β is the initial divergence angle of the beam, n is the refractive index of the waveguide (which is greater than 1), and the incident angle (θ) is constant. i The initial emission angle (θ0) is equal to the initial emission angle.
[0013] According to some embodiments of this disclosure, the beam is tilted relative to the normal of the second transverse surface of the waveguide before being coupled out of the waveguide, and the optical pattern includes diffracted light of order -1 to order -5.
[0014] According to some embodiments of this disclosure, the metasurface includes a plurality of pillars, and the plurality of pillars are arranged in an asymmetrical manner.
[0015] According to some embodiments of this disclosure, the initial exit angle of the light beam within the waveguide is 0 degrees, defined by the angle between the centerline of the beam and the normal to the first transverse surface of the waveguide. The waveguide further includes a mirror and an antireflective layer. The mirror is adjacent to the light source and is configured to change the incident angle of the beam for total internal reflection within the waveguide. The mirror connects the first transverse surface and the second transverse surface and is tilted relative to the first transverse surface of the waveguide. The antireflective layer is adjacent to the metasurface and is substantially perpendicular to both the first and second transverse surfaces.
[0016] According to some embodiments of this disclosure, the tilt angle of the reflector is based on the following equation:
[0017] 2θ slope =θ i ,
[0018] Where θ slope Let θ be the tilt angle of the mirror. slope θ is defined by the angle between the waveguide's mirror and the first transverse surface of the waveguide.i Let θ be the incident angle of the light beam on the first transverse surface of the waveguide. i It is defined as the angle between the centerline of the beam and the normal to the first transverse surface of the waveguide after the beam undergoes one total internal reflection within the waveguide.
[0019] According to some embodiments of this disclosure, the tilt angle of the mirror, the initial divergence angle of the beam, and the refractive index of the waveguide satisfy the following equations:
[0020]
[0021] Where θ slope Let θ be the tilt angle of the mirror. slope Defined by the angle between the waveguide's mirror and the first transverse surface of the waveguide, β is the initial divergence angle of the beam, and n is the refractive index of the waveguide.
[0022] According to some embodiments of this disclosure, the refractive index of the waveguide is greater than 1.
[0023] According to some embodiments of this disclosure, the thickness of the waveguide is based on the following equation:
[0024] H waveguide =W source ×tan(θ slope ),
[0025] Where H waveguide W is the thickness of the waveguide. source θ is the width of the light source. slope Let θ be the tilt angle of the mirror, and θ slope Defined by the angle between the waveguide's mirror and the waveguide's first transverse surface.
[0026] According to some embodiments of this disclosure, the beam is tilted relative to the normal of the second transverse surface of the waveguide before being coupled out of the waveguide, and the optical pattern includes diffracted light of order -1 to order -5.
[0027] According to some embodiments of this disclosure, the metasurface includes a plurality of pillars, and the plurality of pillars are arranged in an asymmetrical manner.
[0028] According to some embodiments of this disclosure, the initial exit angle of the light beam within the waveguide is 0 degrees, defined by the angle between the centerline of the beam and the normal to the first transverse surface of the waveguide. The waveguide further includes a first mirror and a second mirror. The first mirror is adjacent to the light source and is configured to transmit the light beam parallel within the waveguide. The first mirror connects the first transverse surface and the second transverse surface, and is tilted relative to the first transverse surface of the waveguide. The second mirror is adjacent to the metasurface and is configured to change the incident angle of the light beam on the second transverse surface of the waveguide to 0 degrees. The incident angle of the light beam on the second transverse surface is defined by the angle between the normal to the second transverse surface and the centerline of the beam on the second transverse surface. The second mirror connects the first transverse surface and the second transverse surface, and is tilted relative to the first transverse surface of the waveguide. The first mirror is parallel to the second mirror.
[0029] According to some embodiments of this disclosure, the thickness of the waveguide is based on the following equation:
[0030] H waveguide =W source ×tan(θ slope ),
[0031] Where H waveguide W is the thickness of the waveguide. source θ is the width of the light source. slope Let θ be the tilt angle of the first reflecting mirror. slope Defined by the angle between the first reflecting mirror of the waveguide and the first transverse surface of the waveguide, and θ slope It is 45 degrees.
[0032] According to some embodiments of this disclosure, before the light beam is coupled out of the waveguide, the light beam is perpendicular to the second transverse surface of the waveguide, and the optical pattern also includes zero-order diffraction, ±1-order diffraction, and ±2-order diffraction.
[0033] According to some embodiments of this disclosure, the waveguide has a refractive index greater than 1, and the metasurface contains a plurality of pillars arranged symmetrically. Attached Figure Description
[0034] The various embodiments of this disclosure can be best understood by reading in conjunction with the accompanying drawings and the following detailed description. It should be understood that, in accordance with industry standard practice, the various features are not drawn to scale. In fact, the dimensions of the various features can be arbitrarily increased or decreased for clarity.
[0035] Figure 1 This is a cross-sectional schematic diagram of a diffractive optical device illustrated according to some embodiments of the present disclosure.
[0036] Figure 2 for Figure 1 An enlarged view of the surface relief grating in the image.
[0037] Figure 3 for Figure 1 A partial top view of the asymmetric superconducting surface in the image.
[0038] Figure 4 This is a cross-sectional schematic diagram of a diffractive optical device illustrated according to some embodiments of the present disclosure.
[0039] Figure 5 This is a cross-sectional schematic diagram of a diffractive optical device illustrated according to some embodiments of the present disclosure.
[0040] Figure 6 for Figure 5 A partial top view of the symmetrical superconducting surface in the image.
[0041] Figure 7 This is a top view illustrating a packaging structure according to some embodiments of the present disclosure.
[0042] The reference numerals in the attached figures are explained as follows:
[0043] 100: Diffraction optical device
[0044] 110: Waveguide
[0045] 112: Anti-reflective layer
[0046] 114: Reflector
[0047] 116: Reflector
[0048] 120: Light-emitting unit
[0049] 122: Light source
[0050] 124: Surface relief grating
[0051] 130, 130a: Super-high surface
[0052] 132: Substrate
[0053] 134, 134a, 134b, 134c, 134d, 134e, 134f, 134g, 134h, 134i: Columns
[0054] 140: Projection plane
[0055] 400: Diffraction optical device
[0056] 500: Diffraction optical device
[0057] 700: Package structure
[0058] 710: Diffraction Optical Device
[0059] 720: Device
[0060] -1: -1st order diffraction light
[0061] -2: -2nd order diffraction light
[0062] -3: -3rd order diffraction light
[0063] -4: -4th order diffraction light
[0064] -5: -5th order diffraction light
[0065] 0:0 order diffraction light
[0066] +1: +1st order diffraction light
[0067] +2: +2nd order diffraction light
[0068] H waveguide :thickness
[0069] LB: Beam
[0070] P: Spacing
[0071] p1: Inclined plane
[0072] p2: Inclined plane
[0073] s1: First transverse surface
[0074] s2: Second transverse surface
[0075] W source :width
[0076] θ0: Initial launch angle
[0077] θ i Angle of incidence
[0078] θ slope Inclination angle
[0079] β: Initial divergence angle Detailed Implementation
[0080] The embodiments of this disclosure will now be described in detail, and examples are illustrated in the accompanying drawings. Where possible, the same reference numerals are used in the drawings and description to denote the same or similar parts.
[0081] The following disclosure provides many different implementations or embodiments for achieving various features of this disclosure. Specific embodiments of components and arrangements are described below to simplify this disclosure. These are, of course, merely embodiments and are not intended to be limiting. For example, in the following description, the formation of a first feature above or on a second feature may include implementations where the first and second features are formed in direct contact, or implementations where another feature may be formed between the first and second features so that the first and second features are not in direct contact. Furthermore, reference numerals and / or words may be repeated in different instances in this disclosure. The purpose of repetition is to simplify and clarify the description, not to define the relationships between the different implementations and / or configurations discussed. It is understood that the number of any elements / components is for illustrative purposes only and is not intended to limit this disclosure.
[0082] It is understood that although terms such as “first” and “second” may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of the embodiments, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.
[0083] In addition, spatial relative terms such as "below," "below," "lower than," "above," and other similar terms are used here for the convenience of describing the relationship between one element or feature and another element or feature in the figure. Spatial relative terms cover not only the orientation depicted in the figure, but also other orientations of the device during use or operation. The device may be oriented in other orientations (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein can be interpreted accordingly.
[0084] This disclosure presents three diffractive optical devices. In each diffractive optical device, multiple light-emitting units directly contact the transverse surface of the waveguide. The light beam can be transmitted within the waveguide via total internal reflection (TIR) and then coupled out through a metasurface to project an optical pattern (i.e., a diffraction pattern) onto the projection plane. Compared to conventional MOE or DOE systems, the diffractive optical devices of this disclosure do not require a specific focal length to generate the optical pattern. Therefore, the diffractive optical devices of this disclosure can meet the requirements of continuously shrinking diffractive optical devices. The thickness of the diffractive optical devices of this disclosure ranges from tens to hundreds of micrometers.
[0085] Figure 1This is a cross-sectional schematic diagram of a diffractive optical device 100 according to some embodiments of the present disclosure. The diffractive optical device 100 includes a waveguide 110, a light-emitting unit 120, and a metasurface 130. The waveguide 110 includes a first transverse surface s1 and a second transverse surface s2 opposite to the first transverse surface s1, wherein the first transverse surface s1 is parallel to the second transverse surface s2. The light-emitting unit 120 is in direct contact with the first transverse surface s1 of the waveguide 110, wherein the light-emitting unit 120 includes a light source 122. The light-emitting unit 120 is configured to emit a light beam LB having an initial divergence angle β. The metasurface 130 is disposed on the second transverse surface s2 of the waveguide 110, wherein the metasurface 130 is configured to couple the light beam LB out of the waveguide 110 and project an optical pattern onto a projection plane 140, wherein the optical pattern includes negative order diffracted light.
[0086] In some embodiments, the light source 122 includes a vertical cavity surface emitting laser (VCSEL) or a light-emitting diode, but is not limited thereto. In some embodiments, the light source 122 provides a transverse electric (TE) mode and / or a transverse magnetic (TM) mode of the beam LB.
[0087] Please refer to Figure 1 The light-emitting unit 120 also includes a surface relief grating (SRG) 124 disposed between the light source 122 and the waveguide 110. The surface relief grating 124 is disposed on the light source 122. The surface relief grating 124 directly contacts the first transverse surface s1 of the waveguide 110, and the initial exit angle θ0 of the light beam LB within the waveguide 110 is not 0 degrees. The initial exit angle θ0 is defined by the angle between the centerline of the light beam LB and the normal to the first transverse surface s1 of the waveguide 110, such as... Figure 1 As shown. In other words, the initial exit angle θ0 is tilted relative to the normal of the first transverse surface s1 of waveguide 110. It can be understood that the beam LB is coupled into waveguide 110 with the initial exit angle θ0 and the initial divergence angle β.
[0088] Figure 2 for Figure 1 An enlarged view of the surface relief grating 124 is shown. The surface relief grating 124 comprises multiple tilted structures. The tilted structures are configured to efficiently diffract the beam LB from air into the waveguide 110. The incident angle θ can be adjusted by designing the distance P between the tilted structures. i And optimize its slope to achieve the best coupling efficiency to meet the beam LB in waveguide 110 (see reference). Figure 1 The conditions under which total internal reflection occurs in a molecule.
[0089] Please refer to Figure 1 The incident angle θ of beam LB i The initial divergence angle β of beam LB and the refractive index of waveguide 110 satisfy the following equation:
[0090]
[0091] Where θ i Let θ be the incident angle of beam LB. i Let β be the initial divergence angle of beam LB after it undergoes one total internal reflection within waveguide 110, defined by the angle between the centerline of beam LB and the normal to the first transverse surface s1 of waveguide 110, where β is the initial divergence angle of beam LB and n is the refractive index of waveguide 110. When the incident angle θ of beam LB... i The initial divergence angle β of beam LB and the refractive index of waveguide 110 satisfy the above equation, and beam LB undergoes total internal reflection at waveguide 110. In some embodiments, the refractive index of waveguide 110 is greater than 1, for example, SiO2 with a refractive index of 1.5, a-Si with a refractive index of 3.5, or Ta2O5 with a refractive index of 2.1. For example, the material of waveguide 110 includes glass with a refractive index of 1.5. In some embodiments, the initial divergence angle β is approximately 15 degrees in a VCSEL. In some embodiments, when the refractive index of waveguide 110 is 1.5, the incident angle θ i At least 49.3 degrees (i.e., θ) i ≥49.3 degrees). In the embodiment of the diffractive optical device 100, the incident angle θ i It is equal to the initial launch angle θ0.
[0092] Please refer to Figure 1 Before the beam LB is coupled out of waveguide 110, the beam LB is tilted relative to the normal of the second transverse surface s2 of waveguide 110. In other words, the centerline of the beam LB is tilted relative to the normal of the second transverse surface s2. In some embodiments, the optical pattern on the projection plane 140 includes -1st order diffraction, -2nd order diffraction, -3rd order diffraction, -4th order diffraction, and -5th order diffraction. In other words, the beam LB is coupled out of the metasurface 130 into the air and generates multiple negative order diffractions. In some embodiments, the effective refractive index of the metasurface 130 is equal to or higher than the refractive index of waveguide 110 to couple the beam LB out.
[0093] Please refer to Figure 1The waveguide 110 also includes an antireflective layer 112 adjacent to the metasurface 130, and the antireflective layer 112 is substantially perpendicular to the first lateral surface s1 and the second lateral surface s2. Specifically, the antireflective layer 112 is disposed at an end of the waveguide 110. The antireflective layer 112 is configured to suppress reflected light from the beam LB at the end of the waveguide 110, where the reflected light would cause crosstalk interference with the original light of the beam LB. Therefore, the antireflective layer 112 can avoid or reduce crosstalk and improve the coupling efficiency of the diffraction optics device 100.
[0094] Figure 3 for Figure 1 A partial top view of the asymmetric metasurface 130 in the image. Please refer to... Figure 1 and Figure 3 The metasurface 130 includes a substrate 132 and a plurality of pillars 134 (including pillars 134a to 134f), and the plurality of pillars 134a to 134f are arranged in an asymmetric manner. Figure 3 As shown, the diameters of each column 134a–134f can be designed and simulated using the Finite-Difference Time-Domain (FDTD) method. This is because the incident angle θ between the beam LB and the normal to the second transverse surface s2 of waveguide 110... i Furthermore, the required diffraction pattern is negative order diffraction light, therefore Figure 1 and Figure 3 The supersurface 130 in the design is an asymmetric periodic structure. For example... Figure 1 As shown, the metasurface 130 directly contacts the second lateral surface s2 of the waveguide 110. In some embodiments, the projection of the light-emitting unit 120 onto the waveguide 110 is spaced apart from the projection of the metasurface 130 onto the waveguide 110.
[0095] In some embodiments, the diffraction optical device 100 further includes a polarizer disposed between the surface relief grating 124 and the waveguide 110. The polarizer allows a beam of light with a specific polarization LB to pass through.
[0096] exist Figure 1 The diffraction optical device 100 in the waveguide 110 allows a light beam LB with an initial exit angle θ0 to satisfy the total internal reflection condition within the waveguide 110, resulting in total internal reflection of the light beam LB within the waveguide 110. The thickness H of the waveguide 110 is... waveguide Determined by manufacturing capabilities. The total thickness of the diffraction optical device 100 is equal to the thickness of the light-emitting unit 120 and the thickness H. waveguide And the sum of the thickness of the super-sensitive surface 130.
[0097] Figure 4This is a cross-sectional schematic diagram of a diffractive optical device 400 according to some embodiments of the present disclosure. Identical or similar features are indicated by the same element symbols, and descriptions of identical or similar features will not be repeated in the following figures. In the diffractive optical device 400, the waveguide 110 further includes a mirror 114 adjacent to the light source 122. The mirror 114 is configured to change the incident angle of the light beam LB to achieve total internal reflection within the waveguide 110. The mirror 114 connects a first transverse surface s1 and a second transverse surface s2, and the mirror 114 is tilted relative to the first transverse surface s1 of the waveguide 110. In other words, the waveguide 110 has a tilted plane p1, and the mirror 114 is disposed on the tilted plane p1.
[0098] Waveguide 110 also includes an antireflective layer 112 adjacent to metasurface 130, wherein the antireflective layer 112 is substantially perpendicular to the first lateral surface s1 and the second lateral surface s2. The antireflective layer 112 is configured to suppress reflected light from the beam LB at the end of waveguide 110, where the reflected light would cause crosstalk with the original light of beam LB. Therefore, the antireflective layer 112 can avoid or reduce crosstalk and improve the coupling efficiency of the diffraction optics 400.
[0099] Please refer to Figure 4 The initial exit angle θ0 of the beam LB within waveguide 110 (please refer to...) Figure 1 The initial exit angle θ0 is 0 degrees, defined by the angle between the centerline of the beam LB and the normal to the first transverse surface s1 of the waveguide 110. In other words, the centerline of the beam LB is parallel to the normal to the first transverse surface s1 of the waveguide. Perpendicular incidence of the beam LB helps improve coupling efficiency to approach the theoretical transmittance from the light source 122 to the first transverse surface s1, where the equation for the theoretical transmittance is {1-[(n-1) / (n+1)]}. 2}*100%, where n is the refractive index of waveguide 110. For example, given a refractive index of 1.5, the theoretical transmittance of waveguide 110 is approximately 96%.
[0100] In some embodiments, the tilt angle θ of the reflector 114 slope Based on the following equation:
[0101] 2θ slope =θ i ,
[0102] Where θ slope Let θ be the tilt angle of mirror 114. slope θ is defined by the angle between the reflector 114 of waveguide 110 and the first transverse surface s1 of waveguide 110. i Let θ be the incident angle of beam LB on the first transverse surface s1 of waveguide 110, and θ iThe angle between the centerline of the beam LB and the normal to the first transverse surface s1 of the waveguide 110 after the beam LB undergoes one total internal reflection within the waveguide 110 is defined.
[0103] In some embodiments, the tilt angle θ of the reflector 114 slope The initial divergence angle β of beam LB and the refractive index of waveguide 110 satisfy the following equation:
[0104]
[0105] Where θ slope Let θ be the tilt angle of mirror 114, β be the initial divergence angle of beam LB, and n be the refractive index of waveguide 110. In some embodiments, the refractive index of waveguide 110 is greater than 1, for example, SiO2 with a refractive index of 1.5, a-Si with a refractive index of 3.5, or Ta2O5 with a refractive index of 2.1. When the tilt angle θ of mirror 114... slope When the initial divergence angle β of beam LB and the refractive index of waveguide 110 satisfy the above equation, beam LB undergoes total internal reflection within waveguide 110. In some embodiments, the initial divergence angle β is approximately 15 degrees in the VCSEL. In some embodiments, when the refractive index of waveguide 110 is 1.5, the incident angle θ... i At least 49.3 degrees (i.e., θ) i ≥49.3 degrees) and tilt angle θ slope At least 24.65 degrees (i.e., θ) slope ≥24.65 degrees).
[0106] In some embodiments, the thickness H of the waveguide 110 in the diffractive optical device 400 waveguide Based on the following equation:
[0107] H waveguide =W source ×tan(θ slope ),
[0108] Where H waveguide W is the thickness of the waveguide. source For the width of the light source 122, θ slope The tilt angle is θ for the reflector 114. In the embodiment of the diffraction optical device 400, when the refractive index of the waveguide 110 is 1.5, the tilt angle θ is... slope The minimum degree is 24.65 degrees, and the minimum thickness H of waveguide 110 is... waveguide Approximately 0.46 × W source .
[0109] Please refer to Figure 4Before the beam LB is coupled out of the waveguide 110, the beam LB is tilted relative to the normal of the second lateral surface s2 of the waveguide 110. In other words, the centerline of the beam LB is tilted relative to the normal of the second lateral surface s2. In some embodiments, the optical pattern on the projection plane 140 includes multiple diffracted beams of order -1 to -5.
[0110] Please refer to Figure 3 and Figure 4 The metasurface 130 also includes multiple pillars 134 (including pillars 134a to 134f), and the multiple pillars 134a to 134f are arranged asymmetrically. Due to the incident angle θ between the beam LB and the normal to the second transverse surface s2 of the waveguide 110... i Furthermore, the required diffraction pattern is negative order diffraction light, therefore Figure 3 and Figure 4 The supersurface 130 in the design is an asymmetric periodic structure.
[0111] exist Figure 4 In the diffractive optical device 400, the tilted reflector 114 can change the optical path of the light beam LB and satisfy the total internal reflection condition within the waveguide 110, causing the light beam LB to undergo total internal reflection within the waveguide 110. The total thickness of the diffractive optical device 400 is equal to the thickness of the light source 122 and the thickness H. waveguide And the sum of the thickness of the super-sensitive surface 130.
[0112] Figure 5 This is a cross-sectional schematic diagram of a diffractive optical device 500 according to some embodiments of the present disclosure. In the diffractive optical device 500, the waveguide 110 includes a mirror 114 adjacent to the light source 122 and a mirror 116 adjacent to the metasurface 130a. The waveguide 110 has an inclined plane p1 and an inclined plane p2, with the mirror 114 disposed on the inclined plane p1 and the mirror 116 disposed on the inclined plane p2.
[0113] Reflector 114 connects the first lateral surface s1 and the second lateral surface s2, and is tilted relative to the first lateral surface s1 of waveguide 110. Reflector 114 is configured to transmit the beam LB parallel within waveguide 110 after a first total internal reflection. Specifically, after the first total internal reflection, the centerline of the beam LB is parallel to the first lateral surface s1 and the second lateral surface s2 of waveguide 110. Reflector 116 connects the first lateral surface s1 and the second lateral surface s2, and is tilted relative to the first lateral surface s1 of waveguide 110. After a second total internal reflection, reflector 116 is configured to change the angle of incidence of the beam LB to the second lateral surface s2 of waveguide 110 to 0 degrees, wherein the angle of incidence of the beam LB on the second lateral surface s2 is defined by the angle between the normal to the second lateral surface s2 and the centerline of the beam LB on the second lateral surface s2. In other words, the angle between the centerline of the beam LB and the normal to the second lateral surface s2 is 0 degrees. In an embodiment of the diffractive optical device 500, the reflector 114 is parallel to the reflector 116. The diffractive optical device 500 does not have an anti-reflection layer.
[0114] Please refer to Figure 5 The initial exit angle θ0 of beam LB within waveguide 110 (please refer to...) Figure 1 The initial emission angle θ0 is 0 degrees, defined by the angle between the centerline of the beam LB and the normal to the first transverse surface s1 of the waveguide 110. In other words, the centerline of the beam LB is parallel to the normal to the first transverse surface s1 of the waveguide.
[0115] In some embodiments, the thickness H of the waveguide 110 in the diffractive optical device 500 waveguide Based on the following equation:
[0116] H waveguide =W source ×tan(θ slope ),
[0117] Where H waveguide For the thickness of waveguide 110, W source θ is the width of light source 122. slope Let θ be the tilt angle of mirror 114. slope Defined by the angle between the reflector 114 of waveguide 110 and the first transverse surface s1 of waveguide 110, and θ slope It is 45 degrees. In other words, the thickness H waveguide Equal to width W source .
[0118] In an embodiment of the diffractive optical device 500, before the beam LB is coupled out of the waveguide 110, the beam LB is perpendicular to the second transverse surface s2 of the waveguide 110. In other words, the centerline of the beam LB is parallel to the normal of the second transverse surface s2. In some embodiments, the optical pattern on the projection plane 140 includes zero-order diffraction, ±1-order diffraction (i.e., +1-order and -1-order diffraction), and ±2-order diffraction (i.e., +2-order and -2-order diffraction).
[0119] Figure 6 for Figure 5 A partial top view of the symmetrical metamorphic surface 130a in the diagram. Please refer to... Figure 5 and Figure 6 The metasurface 130a includes a substrate 132 and a plurality of pillars 134 (including pillars 134a to 134i), and the plurality of pillars 134a to 134i are arranged in a symmetrical manner. In other words, pillar 134e can be considered as the center of symmetry. In some embodiments, the effective refractive index of the metasurface 130a is equal to or higher than the refractive index of the waveguide 110 to couple the light beam LB out.
[0120] exist Figure 5 In the diffraction optical device 500, the input of the beam LB is perpendicularly coupled to the first transverse surface s1 of the waveguide 110, and the output of the beam LB is perpendicularly coupled to the second transverse surface s2 of the waveguide 110. Therefore, the diffraction optical device 500 can minimize the loss of coupling efficiency, thereby improving its coupling efficiency. Furthermore, because the beam LB between mirrors 114 and 116 is parallel to both the first transverse surface s1 and the second transverse surface s2, the diffraction optical device 500 can significantly reduce propagation loss. Due to θ slope The initial exit angle θ0 is 45 degrees and the beam LB is 130 degrees from the metasurface (please refer to...). Figure 1 The angle is 0 degrees, thus maximizing the coupling efficiency from waveguide 110 to metasurface 130. The total thickness of the diffractive optical device 500 is equal to the thickness of the light source 122 and the thickness H. waveguide And the sum of the thickness of the super-advanced surface 130a.
[0121] The diffraction optical devices 100, 400 and 500 disclosed herein can be applied to the display field (e.g., augmented reality (AR), virtual reality (VR), 2D sensing, 3D sensing and cameras) and the silicon photonics field (e.g., light detection and ranging (LiDAR), optical coupling and guidance and packaging).
[0122] Figure 7 This is a top view of a package structure 700 illustrated according to some embodiments of the present disclosure. The package structure 700 includes a diffractive optical device 710 and a plurality of devices 720. It is understood that the number and configuration of the devices 720 are for illustrative purposes only. In the diffractive optical device 710 of the package structure 700, the waveguide 110 is a bent waveguide. Specifically, the extension direction of the waveguide 110 can be adjusted according to the configuration of the devices 720, thereby creating the shortest waveguide path in the package structure 700. The diffractive optical device 710 can be the diffractive optical devices 100, 400, or 500 described above. In the diffractive optical devices 100, 400, or 500, each waveguide 110 can be a planar waveguide. Therefore, the diffractive optical devices 100, 400, 500, and 710 have high compatibility to match different spaces.
[0123] In each diffractive optical device of this disclosure, the light beam can be transmitted within the waveguide via total internal reflection and then coupled out through a metasurface. Compared to conventional MOE or DOE systems, the thickness of the diffractive optical device can be reduced because the light-emitting unit of this disclosure is in direct contact with the transverse surface of the waveguide. Therefore, the diffractive optical device of this disclosure can meet the requirements of continuously shrinking diffractive optical devices.
[0124] This disclosure has been described above; however, it is not intended to limit the scope of this disclosure. Various changes, substitutions, and modifications can be made to it by those skilled in the art without departing from the concept and scope of this disclosure. Therefore, the scope of protection of this disclosure shall be determined by the claims and their equivalents.
Claims
1. A diffractive optical device, characterized in that, Include: A waveguide includes a first transverse surface and a second transverse surface opposite to the first transverse surface; A light-emitting unit, in direct contact with the first lateral surface of the waveguide, is configured to emit a beam of light having an initial divergence angle, wherein the light-emitting unit includes a light source; and A metasurface is disposed on the second transverse surface of the waveguide, wherein the metasurface is configured to couple the light beam out of the waveguide and project an optical pattern onto a projection plane, wherein the optical pattern includes a negative order diffracted light.
2. The diffraction optical device as claimed in claim 1, wherein the light source comprises a vertical resonant cavity surface-emitting laser or a light-emitting diode, and the waveguide comprises a planar waveguide or a curved waveguide.
3. The diffraction optical device as claimed 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 transverse surface of the waveguide, and the initial exit angle (θ0) 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 transverse surface. Before the beam is coupled out of the waveguide, the beam is tilted relative to a normal of the second transverse surface of the waveguide, and the optical pattern includes diffracted light of order -1 to order -5.
4. The diffraction optical device of claim 3, wherein the surface relief grating comprises a plurality of tilted structures, the metasurface comprises a plurality of pillars, and the plurality of pillars are arranged in an asymmetrical manner.
5. The diffraction optical device of claim 3, wherein the waveguide further comprises an antireflective layer adjacent to the metasurface, and the antireflective layer is perpendicular to the first transverse surface and the second transverse surface.
6. The diffraction optical device of claim 3, wherein an incident angle of the beam, an initial divergence angle of the beam, and a refractive index of the waveguide satisfy the following equation: Where θ i Let β be the incident angle of the beam, defined as the angle between the centerline of the beam and the normal to the first transverse surface of the waveguide after the beam undergoes one total internal reflection within the waveguide; let β be the initial divergence angle of the beam; and let n be the refractive index of the waveguide, which is greater than 1. The incident angle (θ) is... i The initial emission angle (θ0) is equal to this initial emission angle.
7. The diffraction optical device of claim 1, wherein the 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 the first transverse surface of the waveguide, wherein the waveguide further comprises: A reflector, adjacent to the light source, wherein the reflector is configured to change an incident angle of the light beam to achieve total internal reflection within the waveguide, the reflector connects the first lateral surface and the second lateral surface, and the reflector is tilted relative to the first lateral surface of the waveguide; and An anti-reflective layer is provided adjacent to the metasurface, wherein the anti-reflective layer is perpendicular to the first transverse surface and the second transverse surface.
8. The diffraction optical device of claim 7, wherein a tilt angle of the reflector is based on the following equation: 2θ slope =θ i , Where θ slope Let θ be the tilt angle of the mirror. slope θ is defined by the angle between the reflector of the waveguide and the first transverse surface of the waveguide. i Let θ be the incident angle of the light beam on the first transverse surface of the waveguide. i The angle between the centerline of the beam and the normal to the first transverse surface of the waveguide after the beam undergoes one total internal reflection within the waveguide is defined.
9. The diffraction optical device of 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 Let θ be the tilt angle of the mirror. slope Defined by the angle between the reflector of the waveguide and the first transverse surface of the waveguide, β is the initial divergence angle of the beam, and n is the refractive index of the waveguide.
10. The diffraction optical device of claim 7, wherein the thickness of the waveguide is based on the following equation: H waveguide =W source ×tan(θ slope ), Where H waveguide For the thickness of this waveguide, W source Let θ be the width of the light source. slope Let θ be a tilt angle of the mirror, and θ slope Defined by an angle between the waveguide's reflector and the waveguide's first transverse surface.
11. The diffraction optical device of claim 1, wherein the 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 the first transverse surface of the waveguide, wherein the waveguide further comprises: A first reflector, adjacent to the light source, wherein the first reflector is configured to transmit the light beam parallel within the waveguide, the first reflector connects the first lateral surface and the second lateral surface, and the first reflector is tilted relative to the first lateral surface of the waveguide; and A second reflector is provided adjacent to the metasurface, wherein the second reflector is configured to change the angle of incidence of the light beam at the second transverse surface of the waveguide to 0 degrees, the angle of incidence of the light beam at the second transverse surface being defined by an angle between a normal of the second transverse surface and the center line of the light beam at the second transverse surface, the second reflector connecting the first transverse surface and the second transverse surface, and the second reflector being tilted relative to the first transverse surface of the waveguide, wherein the first reflector is parallel to the second reflector.
12. The diffraction optical device of claim 11, wherein the thickness of the waveguide is based on the following equation: H waveguide =W source ×tan(θ slope ), Where H waveguide For the thickness of this waveguide, W source Let θ be the width of the light source. slope Let θ be the tilt angle of the first reflecting mirror. slope Defined by an angle between the first reflector of the waveguide and the first transverse surface of the waveguide, and θ slope It is 45 degrees.
13. The diffraction optical device of claim 12, wherein the beam is perpendicular to the second transverse surface of the waveguide before being coupled out of the waveguide, and the optical pattern further comprises zero-order diffraction, ±1-order diffraction, and ±2-order diffraction.