CN110068900B

CN110068900B - Optical coupler

Info

Publication number: CN110068900B
Application number: CN201810066896.1A
Authority: CN
Inventors: 杨立启; 曾智伟; 吴志忠; 庄荣敏
Original assignee: Oplink Communications LLC
Current assignee: Oplink Communications LLC
Priority date: 2018-01-24
Filing date: 2018-01-24
Publication date: 2021-03-12
Anticipated expiration: 2038-01-24
Also published as: CN110068900A

Abstract

The present disclosure provides an optical coupler. The optical coupler includes an optical waveguide. The optical waveguide includes a body portion, a first lower-layer finger structure, a second lower-layer finger structure, a first upper-layer finger structure, and a second upper-layer finger structure. The first lower layer finger structure is connected with the body portion. The second lower finger structure is connected to the body portion. The first lower-layer finger-shaped structure, the second lower-layer finger-shaped structure and the body part define a U-shaped structure in a front-back direction, and an opening of the U-shaped structure faces forward. The first upper layer finger structure is above the first lower layer finger structure and connected with the body part. The second upper layer finger structure is above the second lower layer finger structure and connected with the body part. The optical coupler utilizes the double-layer finger structure to expand an optical field mode.

Description

Optical coupler

Technical Field

The present disclosure relates to optical devices, and more particularly to an optical coupler for coupling an optical field to an integrated circuit.

Background

Fig. 1 is a schematic view of a conventional optical coupler (optical coupler), which is disclosed in U.S. Pat. No. 9002263. Referring to fig. 1, the conventional optical coupler utilizes a double-layer tapered structure of a first tapered structure 114a and a second tapered structure 116a to enlarge the size of an optical field mode in the vertical direction, thereby reducing the energy loss of coupling. The energy dissipation reduced in this way is however limited.

Fig. 2 is a schematic view showing the structure of another conventional optical coupler (optical coupler), which is disclosed in U.S. Pat. No. US 9477043. Referring to fig. 2, the optical coupler of the prior art uses a plurality of

tapered structures

432, 433, 434 to expand the size of the optical field mode in the horizontal direction, but not in the vertical direction.

This background discussion section is intended only to provide background data. The statements in this background discussion are not an admission that the subject matter disclosed in this section constitutes background to the present disclosure, and no part of this section is available as an admission that any part of the present application, including this background section, constitutes background to the present disclosure.

Disclosure of Invention

Embodiments of the present disclosure provide an optical coupler. The optical coupler includes an optical waveguide. The optical waveguide includes a body portion, a first lower-layer finger structure, a second lower-layer finger structure, a first upper-layer finger structure, and a second upper-layer finger structure. The first lower layer finger structure is connected with the body portion. The first lower layer finger structure has a first length. The second lower finger structure is connected to the body portion. The second lower layer finger structure has a second length. The first upper layer finger structure is above the first lower layer finger structure and connected with the body part. The first upper layer finger structure has a third length, and the third length is shorter than the first length. The second upper layer finger structure is above the second lower layer finger structure and connected with the body part. The second upper layer finger structure has a fourth length, and the fourth length is shorter than the second length.

In embodiments of the present disclosure, the first lower finger structure includes a first lower back end. The second lower finger structure includes a second lower rear end. The first upper finger structure includes a first upper rear end portion. The second upper finger structure includes a second upper rear end portion. The first lower rear end portion, the second lower rear end portion, the first upper rear end portion and the second upper rear end portion are aligned with each other.

In an embodiment of the disclosure, the body portion includes a first body portion and a second body portion. The second body portion extends from the first body portion. The first lower layer finger structure extends from the second body portion. The second lower finger structure extends from the second body portion. The first upper layer finger structure extends from the first body portion and is located above the first lower layer finger structure and the second body portion. The second upper layer finger structure extends from the first body portion and is located above the second lower layer finger structure and the second body portion. The first upper finger structure and the second upper finger structure together expose a first portion of the second body portion.

In an embodiment of the present disclosure, the optical coupler further includes a third lower layer finger structure and a third upper layer finger structure. The third lower finger extends from the second body portion. The third upper layer finger structure extends from the first body portion and is located above the third lower layer finger structure and the second body portion. The second upper layer finger structure and the third upper layer finger structure together expose a second portion of the second body portion. The first portion has a first terminal portion. The second portion has a second terminal portion. The first terminal portion is aligned with the second terminal portion.

In an embodiment of the present disclosure, the first lower layer finger structure, the second lower layer finger structure, the first upper layer finger structure, and the second upper layer finger structure are made of silicon (Si), silicon nitride (SiN), silicon oxynitride (SiON), or silicon carbide (SiC).

In embodiments of the present disclosure, the first lower layer finger structure has a first width. The first upper layer finger structure has a second width. The first width is wider than the second width.

In embodiments of the present disclosure, the underlying finger structures each include a grating.

In an embodiment of the present disclosure, the upper layer finger structures each include a grating.

In an embodiment of the present disclosure, the first lower-layer finger structure, the second lower-layer finger structure and the body portion define a groove in a front-to-rear direction, and an opening of the groove faces forward.

In the embodiment of the present disclosure, the groove has a U-shaped structure.

In an embodiment of the present disclosure, the first lower finger structure and the first upper finger structure are the same semiconductor layer, and the semiconductor layer is etched to have the first lower finger structure and the first upper finger structure through a specific etching process.

In an embodiment of the present disclosure, the first lower layer finger structure and the first upper layer finger structure are different semiconductor layers.

In an embodiment of the present disclosure, the first lower layer finger structure and the first upper layer finger structure are composed of different materials.

In an embodiment of the present disclosure, the first lower layer finger structure and the first upper layer finger structure are composed of the same material.

The invention discloses a coupling optical field and an integrated circuit by utilizing a plurality of double-layer finger-shaped structures, wherein the plurality of double-layer finger-shaped structures are used for expanding the horizontal mode of the optical field and expanding the vertical mode of the optical field by utilizing the double-layer finger-shaped structures by increasing the number of coupled inner cores, so that the loss in coupling can be effectively reduced, the coupling efficiency of the optical field and the integrated circuit is increased, the problem of energy dissipation caused by the traditional coupling mode is solved, and the reliability of the optical coupler in coupling the optical field and the integrated circuit is improved.

Drawings

The aspects of the present disclosure are best understood from the following detailed description and accompanying drawings. It is noted that, according to the standard implementation of the industry, the various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

Fig. 1 is a schematic structural view of a conventional optical coupler.

Fig. 2 is a schematic structural view of another conventional optical coupler.

Fig. 3 is a perspective view of an optical coupler according to an embodiment of the present disclosure.

FIG. 4 is a top view of the optical coupler of FIG. 3.

Fig. 5 is a schematic diagram of the first optical waveguide of fig. 3.

Fig. 6 is a schematic top view of another optical waveguide according to an embodiment of the present disclosure.

Fig. 7 is a perspective view of yet another optical waveguide of an embodiment of the present disclosure.

Fig. 8 is a perspective view of yet another optical waveguide of an embodiment of the present disclosure.

[ notation ] to show

1 optical coupler

2 silicon dioxide layer

3 first optical waveguide

4 base plate

5 body part

6 body part

9 second optical waveguide

10 first part

11 first lower layer finger structure

12 first upper layer finger structure

13 optical fiber

15 light beam

1A grating

8A grating

20 second part

21 second lower layer finger structure

22 second upper layer finger structure

23 first end

25 second end

31 third lower layer finger structure

32 third upper layer finger structure

33 optical waveguide

34 optical waveguide

41 fourth lower layer finger structure

42 fourth upper layer finger structure

51 fifth lower layer finger structure

52 fifth upper layer finger structure

61 sixth lower layer finger structure

62 sixth upper layer finger

63 first body part

64 second body part

65 optical waveguide

67 optical waveguide

71 seventh lower layer finger structure

72 seventh upper layer finger structure

100 first terminal part

111 front end of first lower layer

112 first lower rear end portion

114a first cone-like structure

116a second cone structure

121 first upper front end

122 first upper rear end

131 lower layer finger structure

132 lower layer finger structure

133 lower layer finger structure

134 lower layer finger structure

135 lower layer finger structure

136 lower layer finger structure

137 lower layer finger structure

141 upper finger structure

142 upper finger structure

143 upper finger structure

144 upper layer finger structure

145 upper layer finger structure

146 upper layer finger structure

147 upper finger structure

151 upper front end portion

152 upper rear end portion

161 lower layer front end

162 lower rear end portion

200 second terminal part

211 second lower layer front end portion

212 second lower rear end portion

221 second upper layer front end part

222 second upper rear end portion

432 taper structure

433 taper structure

434 tapered structure

Height H1

Height H2

L1 length

L2 length

Width of W1

Width of W2

Width of W3

W4 width.

Detailed Description

The following disclosure provides many different embodiments, or examples, for implementing different features of the application. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to limit the present application. For example, the following description of forming a first feature over or on a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which other features are formed between the first and second features, such that the first and second features are not in direct contact. Moreover, the present application may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or architectures discussed.

Furthermore, the present application may use spatially corresponding terms, such as "for example," "below," "lower," "above," "higher," and the like, to describe one element or feature's relationship to another element or feature in the figures. Spatially corresponding terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be positioned (rotated 90 degrees or at other orientations) and the spatially corresponding descriptions used herein may be interpreted accordingly. It is understood that when a feature is formed over another feature or substrate, other features may be present therebetween.

The invention discloses a light field and an integrated circuit coupled by a plurality of double-layer finger-shaped structures, which are used for expanding the horizontal mode of the light field and expanding the vertical mode of the light field by utilizing the double-layer structures by increasing the number of coupled inner cores, thereby effectively reducing the loss during coupling, increasing the efficiency during coupling the light field and the integrated circuit, overcoming the problem of energy dissipation caused by the traditional coupling mode and improving the reliability of an optical coupler during coupling the light field and the integrated circuit.

In the embodiments of the present disclosure described below, the optical field described above will be transmitted through an optical fiber in the form of a light beam. However, the present disclosure is not intended to be limited to the optical field being transmitted through optical fibers. In other embodiments, the optical field may be focused by a laser outside the optical coupler and then coupled into the plurality of double-layer fingers.

Fig. 3 is a perspective view of an optical coupler 1 according to an embodiment of the present disclosure. Referring to fig. 3, the optical coupler 1 is configured to receive a light beam 15 provided by an optical fiber 13 and output the light beam 15 to an integrated circuit (not shown in fig. 3). The optical coupler 1 includes an optical waveguide 33, a silicon dioxide layer 2, and a substrate 4. The optical waveguide 33 is located above the silicon dioxide layer 2, and the silicon dioxide layer 2 is located above the substrate 4 in sequence. In some embodiments, the substrate 4 may comprise a silicon oxynitride-on-insulator (SiON) substrate, or a silicon nitride-on-insulator (SiN-on-insulator) substrate. In some embodiments, the optical waveguide 33 is coated with a coating (not shown in FIG. 3). The optical waveguide 33 has a refractive index higher than that of the clad. Therefore, even if a portion of the light beam 15 does not initially enter the optical waveguide 33 but enters the cladding layer, it is redirected back into the optical waveguide 33 due to the refractive index, thereby confining the light beam 15 within the optical waveguide 33 to prevent the light beam 15 from being lost.

The optical waveguide 33 includes a first optical waveguide 3 and a second optical waveguide 9. The first optical waveguide 3 includes a body portion 5, a plurality of lower-

layer finger structures

11, 21, 31, 41, 51, 61, 71, and a plurality of upper-

layer finger structures

12, 22, 32, 42, 52, 62, 72. For convenience of description, the

lower layer fingers

11, 21, 31 are illustrated as first, second, and third

lower layer fingers

11, 21, 31, respectively, where appropriate. Similarly, the

upper layer fingers

12, 22, 32 are illustrated as first upper layer fingers 12, second upper layer fingers 22, and third upper layer fingers 32, respectively, where appropriate. Since the optical waveguide 33 has a plurality of finger structures, the size of the optical field in the horizontal direction (i.e., the horizontal mode of the optical field is expanded) can be expanded. Therefore, the coupled energy loss can be effectively reduced.

The

lower finger structures

11, 21, 31, 41, 51, 61, 71 are connected to the body portion 5. Specifically, the first lower-layer finger structures 11, the second lower-layer finger structures 21, and a portion of the body portion 5 define a U-shaped structure in a front-to-rear direction, and the opening of the U-shaped structure faces forward. Similarly, any two adjacent lower finger structures and a portion of the body portion 5 define a U-shaped structure. In some embodiments, the material of the

lower finger structures

11, 21, 31, 41, 51, 61, 71 may be any one of the following materials: silicon (Si), silicon nitride (SiN), silicon oxynitride (SiON), and silicon carbide (SiC).

The

upper layer fingers

12, 22, 32, 42, 52, 62, 72 are connected to the body portion 5 and are located above the

lower layer fingers

11, 21, 31, 41, 51, 61, 71, respectively. In some embodiments, the material of which the upper

layer finger structures

12, 22, 32, 42, 52, 62, 72 are made may be any of the following materials: silicon (Si), silicon nitride (SiN), silicon oxynitride (SiON), and silicon carbide (SiC). In some embodiments, the

upper layer fingers

12, 22, 32, 42, 52, 62, 72 are formed of the same material as the

lower layer fingers

11, 21, 31, 41, 51, 61, 71. In some embodiments, the

upper finger structures

12, 22, 32, 42, 52, 62, 72 and the

lower finger structures

11, 21, 31, 41, 51, 61, 71 are the same semiconductor layer, and the semiconductor layer is etched into an upper layer having the

upper finger structures

12, 22, 32, 42, 52, 62, 72 and a lower layer having the

lower finger structures

11, 21, 31, 41, 51, 61, 71 through a specific etching process. In some embodiments, the upper

layer finger structures

12, 22, 32, 42, 52, 62, 72 and the lower

layer finger structures

11, 21, 31, 41, 51, 61, 71 are different semiconductor layers. In some embodiments, the

upper layer fingers

12, 22, 32, 42, 52, 62, 72 are formed of a different material than the

lower layer fingers

11, 21, 31, 41, 51, 61, 71. In some embodiments, the

upper layer fingers

12, 22, 32, 42, 52, 62, 72 are formed of the same material as the

lower layer fingers

11, 21, 31, 41, 51, 61, 71. The first lower finger 11 is used as an example to explain the function and structure of the lower finger. The remaining

lower layer fingers

21, 31, 41, 51, 61, 71 have the same function and structure. The first lower layer finger 11 is configured to receive a light beam 15. In some embodiments, the first lower layer finger structures 11 are tapered or elongated. In some embodiments, the first lower layer fingers 11 are linear tapered or non-linear tapered.

The second optical waveguide 9 comprises a first end 23 and a second end 25, which are opposite to each other. The first end 23 is connected to the body portion 5 of the first optical waveguide 3 and the second end 25 is connected to the integrated circuit, wherein the width W3 of the first end 23 is wider than the width W4 of the second end 25. Thus, the second optical waveguide 9 is a tapered optical waveguide. Accordingly, as the light beam 15 enters from the first end 23 of the second optical waveguide 9 and travels towards the second end 25, the optical field size of the light beam 15 is gradually reduced. Therefore, the optical coupling loss can be effectively reduced.

In contrast, in some prior art optical waveguides, the size of the optical waveguide is not tapered, but is discontinuously tapered in a discontinuous cross-section. Since the change in profile is drastic compared to the change in taper, the optical coupling loss is relatively high.

Fig. 4 is a schematic top view of the optical coupler 1 of fig. 3. Referring to fig. 4, the first upper finger 12 and the second upper finger 22 respectively include a first upper rear end 122 and a second upper rear end 222.

The first lower finger 11 includes a first lower front end 111 and a first lower rear end 112, which are opposite to each other. First lower layer front end section 111 couples to optical fiber 13, thereby receiving optical beam 15. In some embodiments, the width of the first lower layer front end portion 111 is less than 1 micrometer (μm). The first lower rear end portion 112 is connected to the main body portion 5. Similarly, the second lower layer finger structure 21 includes a second lower layer front end 211 and a second lower layer rear end 212, which are opposite to each other. The second lower front end 211 and the second lower rear end 212 have the same structure and function as the first lower front end 111 and the first lower rear end 112, respectively, and are not described herein again.

The first lower rear end portion 112, the second lower rear end portion 212, the first upper rear end portion 122, and the second upper rear end portion 222 are aligned with one another. More specifically, the connection surface between the first lower rear end 112 and the main body 5, the connection surface between the second lower rear end 212 and the main body 5, the connection surface between the first upper rear end 122 and the main body 5, and the connection surface between the second upper rear end 222 and the main body 5 are coplanar. Accordingly, the number of cross sections between the first optical waveguide 3 and the second optical waveguide 9 is relatively small, and thus the efficiency of optical coupling is relatively high.

For convenience of description, only the first upper layer finger structure 12, the second upper layer finger structure 22, the first lower layer finger structure 11, and the second lower layer finger structure 21 are taken as examples. The present disclosure is not limited thereto, and in some embodiments, the connection surfaces of all the upper

layer finger structures

12, 22, 32, 42, 52, 62, 72 and all the lower

layer finger structures

11, 21, 31, 41, 51, 61, 71 and the body portion 5 are coplanar. In some embodiments, the at least two lower layer finger structures and the at least two upper layer finger structures are coplanar with the connection face of the body portion 5.

In addition, in the present embodiment, a first width W1 of the first lower layer finger 11 is wider than a second width W2 of the first upper layer finger 12. The present disclosure is not so limited and in some embodiments, the first width W1 of the first lower layer fingers 11 is the same as the second width W2 of the first upper layer fingers 12. In the above description, the relative relationship between the lower layer fingers and the upper layer fingers in the width direction is exemplified by the first lower layer fingers 11 and the first upper layer fingers 12. The remaining

lower layer fingers

21, 31, 41, 51, 61, 71 and the remaining

upper layer fingers

22, 32, 42, 52, 62, 72 may have the same relationship in width.

Fig. 5 is a schematic view of the first optical waveguide 3 of fig. 3. Fig. 5 is only used to illustrate the relationship between the height and the length of the first upper layer finger 12 and the first lower layer finger 11, and is not used to illustrate the actual structure reflecting the two. Referring to fig. 5, the first lower layer finger 11 has a height H1 and a length L1, and the first upper layer finger 12 has a height H2 and a length L2. In some embodiments, the height H1 is 110 nanometers (nm) and the height H2 is 110 nm, so that the height of the front end of the first optical waveguide 3 is lower than that of the conventional optical coupler to enlarge the dimension of the optical field in the vertical direction (i.e., enlarge the vertical mode of the optical field). In some embodiments, the length L1 is longer than the length L2, so that the optical waveguide 3 has a step-like structure, so as to enlarge the dimension of the optical field in the vertical direction, thereby effectively reducing the coupled energy dissipation. When the functions and structures of the upper layer fingers and the lower layer fingers are described above, the first lower layer fingers 11 and the first upper layer fingers 12 are taken as examples. The remaining upper and lower fingers (not shown in fig. 5) have the same function and structure.

Fig. 6 is a schematic top view of another optical waveguide 34 of an embodiment of the present disclosure. Referring to fig. 6, an optical waveguide 34 is similar to the optical waveguide 33 of fig. 4, with the difference that the optical waveguide 34 includes a body portion 6. The body portion 6 includes a first body portion 63 and a second body portion 64. The height of the first body portion 63 is similar to the sum of the heights H1 and H2 of fig. 5, and the height of the second body portion 64 is similar to the height H1 of fig. 5. The second body portion 64 is located between the first body portion 63 and the

lower finger structures

11, 21, 31, 41, 51, 61, 71. Further, the

lower finger structures

11, 21, 31, 41, 51, 61, 71 extend from the second body portion 64.

The first upper layer finger 12 extends from the first body portion 63 and is located above the first lower layer finger 11 and the second body portion 64. Similarly, the remaining upper fingers extend from the first body portion 63 and are positioned above their associated lower fingers and the second body portion 64.

The first upper layer fingers 12 and the second upper layer fingers 22 together expose a first portion 10 of the second body portion 64, and the second upper layer fingers 22 and the third upper layer fingers 32 together expose a second portion 20 of the second body portion 64. Similarly, the remaining adjacent upper finger structures together expose other portions of the second body portion 64.

For ease of discussion, the exposed first portion 10 and second portion 20 are used as examples below. The relationship between the remaining exposed portions may be the same as the first portion 10 and the second portion 20. The first portion 10 includes a first terminal portion 100. the first terminal portion 100 may be considered to be a finger web between the

lower layer fingers

11 and 21. The second portion 20 includes a second terminal portion 200, and the second terminal portion 200 may be considered as a web between the

lower layer fingers

21 and 31.

The first terminal portion 100 and the second terminal portion 200 are aligned with each other. That is, similar to that described in fig. 4, the connection surface of the first lower rear end portion 112 and the second body portion 64 and the connection surface of the second lower rear end portion 212 and the second body portion 64 are aligned with each other. In view of the above, can reduce the section when the optical coupling, and then promote optical coupling's efficiency. The above description has been given only by way of example of the first terminal portion 100 and the second terminal portion 200, and the present disclosure is not limited thereto. In some embodiments, the webs between all two adjacent lower layer fingers are aligned to reduce the cross-section of the optical coupling, thereby improving the efficiency of the optical coupling.

Similarly, the webs between the first and second

upper layer fingers

12, 22 are aligned with the webs between the second and third

upper layer fingers

22, 32. That is, the connection surfaces between the first upper layer finger structures 12 and the first body portion 63, the connection surfaces between the second upper layer finger structures 22 and the first body portion 63, and the connection surfaces between the third upper layer finger structures 32 and the first body portion 63 are aligned with each other. In view of the above, can reduce the section when the optical coupling, and then promote optical coupling's efficiency. The first upper-layer finger structures 12, the second upper-layer finger structures 22, and the third upper-layer finger structures 32 are only used as examples, and the disclosure is not limited thereto. In some embodiments, the webs between all two adjacent upper layer fingers are aligned to reduce the cross-section of the optical coupling, thereby improving the efficiency of the optical coupling.

In addition, the connection surfaces of the first lower layer finger structures 11 and the second body portion 64 are not aligned with the connection surfaces of the first upper layer finger structures 12 and the first body portion 63 in the front-rear direction. The upper layer palm and the lower layer palm are deviated in the front-back direction. Accordingly, the efficiency of optical coupling can be improved more effectively.

Fig. 7 is a perspective view of yet another optical waveguide 65 of an embodiment of the present disclosure. Referring to FIG. 7, optical waveguide 65 is similar to optical waveguide 34 of FIG. 6, with the difference that optical waveguide 65 includes a plurality of underlying fingers 131, 132, 133, 134, 135, 136, 137.

The lower finger 131 includes a lower front end 161 and a lower rear end 162, which are opposite to each other. The lower rear end portion 162 is connected to the second body portion 64. The lower front end 161 includes a grating 1A. The grating 1A is formed by, for example, a photolithography or etching technique. Since the lower finger 131 has the grating 1A, the optical coupling efficiency is relatively good. In the example of the lower finger 131, the remaining lower fingers 132, 133, 134, 135, 136, 137 may have the same structure.

Fig. 8 is a perspective view of another optical waveguide 67 of an embodiment of the present disclosure. Referring to FIG. 8, optical waveguide 67 is similar to optical waveguide 34 of FIG. 6, with the difference that optical waveguide 67 includes a plurality of upper

level finger structures

141, 142, 143, 144, 145, 146, 147.

The upper finger 141 includes an upper front end 151 and an upper rear end 152, which are opposite to each other. The upper layer rear end portion 152 is connected to the first body portion 63. The upper layer front end 151 includes a grating 8A. The grating 8A is formed by, for example, photolithography or etching techniques. Since the upper layer finger 141 has the grating 8A, the coupling efficiency for a horizontally polarized light in the light beam 15 can be improved. In the above example, the upper layer fingers 141 are all the same as the rest of the

upper layer fingers

142, 143, 144, 145, 146, and 147.

The foregoing outlines features of some embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and components for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

1. An optical coupler, comprising:

an optical waveguide, comprising:

a body portion;

a first lower finger structure including a first lower front end and a first lower rear end connected to the body portion, the first lower front end configured to receive a light beam, the first lower finger structure having a first length;

a second lower finger structure including a second lower front end and a second lower rear end, the second lower rear end connected to the body portion, the second lower front end configured to receive the beam, the second lower finger structure having a second length;

a first upper finger structure including a first upper front end and a first upper rear end, above the first lower finger structure and connected to the body portion at the first upper rear end, the first upper finger structure having a third length shorter than the first length, wherein the first upper front end is a first specific distance from the first lower front end in a length direction; and

a second upper finger structure including a second upper front end and a second upper rear end, above the second lower finger structure and connected to the body portion at the second upper rear end, wherein the second upper front end is a second specific distance from the second lower front end in the length direction, the second upper finger structure has a fourth length, and the fourth length is shorter than the second length.

2. The optical coupler of claim 1, wherein the first lower layer back end, the second lower layer back end, the first upper layer back end and the second upper layer back end are aligned with one another.

3. The optical coupler of claim 1, wherein the body portion comprises:

a first body portion; and

a second body portion extending from the first body portion, wherein the first lower finger structure extends from the second body portion, and the second lower finger structure extends from the second body portion, wherein the first upper finger structure extends from the first body portion and is positioned above the first lower finger structure and the second body portion, wherein the second upper finger structure extends from the first body portion and is positioned above the second lower finger structure and the second body portion, wherein the first upper finger structure and the second upper finger structure together expose a first portion of the second body portion.

4. The optical coupler of claim 3, further comprising:

a third lower finger structure extending from the second body portion; and

a third upper layer finger structure extending from the first body portion and located over the third lower layer finger structure and the second body portion, wherein the second upper layer finger structure and the third upper layer finger structure together expose a second portion of the second body portion, wherein the first portion has a first terminal portion and the second portion has a second terminal portion, the first terminal portion being aligned with the second terminal portion.

5. The optical coupler of claim 1, wherein the first lower layer fingers, the second lower layer fingers, the first upper layer fingers, and the second upper layer fingers are silicon (Si), silicon nitride (SiN), silicon oxynitride (SiON), or silicon carbide (SiC).

6. The optical coupler of claim 1, wherein the first lower layer finger structure has a first width and the first upper layer finger structure has a second width, wherein the first width is wider than the second width.

7. The optical coupler of claim 1, wherein the underlying finger structures each include a grating.

8. The optical coupler of claim 1, wherein the upper layer fingers each include a grating.

9. The optical coupler of claim 1, wherein the first lower layer finger structure, the second lower layer finger structure and the body portion define a recess in a front-to-back direction, an opening of the recess facing forward.

10. The optical coupler of claim 9, wherein the recess is a U-shaped structure.

11. The optical coupler of claim 1, wherein the first lower finger structure and the first upper finger structure are the same semiconductor layer, and the semiconductor layer is etched to have the first lower finger structure and to have the first upper finger structure by a specific etching process.

12. The optical coupler of claim 1, wherein the first lower layer finger structure and the first upper layer finger structure are different semiconductor layers.

13. The optical coupler of claim 12, wherein the first lower layer fingers and the first upper layer fingers are comprised of different materials.

14. The optical coupler of claim 12, wherein the first lower layer fingers and the first upper layer fingers are comprised of the same material.