Optical interlink structure

Abstract

The present disclosure relates to an integrated photonic device, specifically an optical interlink structure. An optical interlink structure includes conjoined optical components, wherein each component includes one or cascaded multimode interferometer(s) (MMIs) on two distinct optical chip regions, wherein the conjoined arrangement enables efficient optical transmission between the interlink components.

Description

Technical Field

[0001] This disclosure relates to the fields of integrated photonics, large-scale wafers, optical wafer-to-wafer interconnects, and hybrid optical integration. The invention discloses an optical interconnect unit having one or more interconnect structures that optimize optical signal propagation from one optical wafer to another. Prior Technology

[0002] Optical interconnects are used to integrate multiple areas of a design or fabrication, ensuring that optical signal transmission between these areas remains largely uninterrupted. Optical interconnect structures are required to integrate at least two different optical wafers.

[0003] In wafer-to-wafer coupling, structural discontinuities between optical wafers can lead to optical signal loss in those discontinuities. Such signal loss is undesirable. Optical interconnect structures are needed to ensure that signal transmission is not affected by any discontinuities that may occur across the optical wafers.

[0004] Optical interconnects are used to integrate two different optical wafers. This is especially necessary when integrating wafers made of different optical materials, which may possess properties suitable for different functions. For example, optical coupling between optical wafers made of different materials is essential for integrating multiple high-performance functions on a single platform. However, while various wafer-to-wafer implementations have been proposed, these methods either have low inter-wafer optical coupling efficiency, require difficult inter-wafer alignment, or involve complex structural designs. Designing a structure that addresses these issues can be extremely complex. Although hybrid integration has been widely adopted for such integrations, these hybrid integration methods typically involve trade-offs in spectral bandwidth, optical coupling efficiency, manufacturability, or mechanical stability.

[0005] The goal is to develop an optical interconnect method that addresses the aforementioned and other trade-offs and drawbacks. Summary of the Invention

[0006] According to one aspect, an optical interconnect structure is provided, the optical interconnect structure comprising: An optical interconnect transmitter having at least one transmitter multimode interferometer, each transmitter multimode interferometer having at least one transmitter waveguide; An optical interconnect receiver having at least one receiver multimode interferometer, each receiver multimode interferometer having at least one receiver waveguide; In this configuration, the optical interconnect transmitter and the optical interconnect receiver are arranged on different optical wafers, with a discontinuous region inserted between them. The interferometers are derived from at least one transmitter multimode interferometer and at least one receiver multimode interferometer, and are closest to the discontinuity region in the at least one transmitter multimode interferometer and at least one receiver multimode interferometer. The two multimode interferometers are connected to each other, such that the transmitter waveguide and receiver waveguide of the two multimode interferometers are connected.

[0007] According to one aspect, an optical interconnect structure is provided, the optical interconnect structure comprising: An optical interconnect transmitter having at least one transmitter multimode interferometer, each transmitter multimode interferometer having at least one transmitter waveguide; An optical interconnect receiver having at least one receiver multimode interferometer, each receiver multimode interferometer having at least one receiver waveguide; and A first optical wafer region and a distinct second optical wafer region are provided, wherein optical interconnect transmitters and optical interconnect receivers are respectively arranged on the first optical wafer region and the second optical wafer region, with a discontinuous region interposed between them. Among them, two multimode interferometers, which are derived from at least one transmitter multimode interferometer and at least one receiver multimode interferometer and are closest to the discontinuity region, are connected to each other, such that the transmitter waveguide and receiver waveguide of the two multimode interferometers are connected.

[0008] In the embodiments described above, the waveguides of the two multimode interferometers are arranged to be in contact with each other.

[0009] In an embodiment of the above aspect, the optical interconnect structure further includes: a refractive index matching material arranged in the discontinuous region, wherein the waveguides of the two multimode interferometers are connected by the refractive index matching material.

[0010] In the embodiments described above, the at least one transmitter multimode interferometer comprises a plurality of transmitter multimode interferometers connected in series, and the at least one receiver multimode interferometer comprises a plurality of receiver multimode interferometers connected in series.

[0011] In the embodiments described above, the at least one transmitter multimode interferometer comprises a single transmitter multimode interferometer, and the at least one receiver multimode interferometer comprises a single receiver multimode interferometer.

[0012] In embodiments described above, each waveguide of at least a portion of the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer comprises a width that is at least five times the width of the input port of the waveguide.

[0013] In the embodiments described above, each waveguide of at least a portion of the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer includes a width that tapers in opposite directions from the input port of the waveguide to the output port of the waveguide.

[0014] In the embodiments described above, the two multimode interferometers are misaligned laterally.

[0015] In the embodiments described above, the two multimode interferometers are misaligned in the vertical direction.

[0016] In the embodiments described above, the different materials are selected from the group consisting of silicon (Si), polysilicon, silicon nitride (Si3N4), silicon dioxide, germanium (Ge), lithium niobate (Li3NbO3), polymers, and group III-IV compounds.

[0017] In the embodiments described above, the at least one transmitter waveguide and the at least one receiver waveguide contain different materials.

[0018] From the foregoing disclosure and the following more detailed description of various embodiments, it will be apparent to those skilled in the art that the present invention provides a significant technical advancement in enabling low-loss optical transmission between two different wafer regions. Particularly important in this respect is the invention's potential to provide enhanced optical transmission with a wide optical bandwidth between two different wafer regions with high manufacturability. This prevents signal information loss across a wide spectral wavelength range, which would otherwise exist at discontinuities between wafer regions due to a lack of modal focusing. Other features and advantages of the various embodiments will be better understood in conjunction with the detailed description provided below. Simple Explanation of the Diagram

[0019] Figure 1 shows a schematic diagram of an optical interconnect structure having two different optical wafers according to certain embodiments.

[0020] Figure 2 shows a schematic top view of an optical interconnect structure with different waveguide materials according to one embodiment.

[0021] Figure 3 shows a schematic isometric view of the optical interconnect structure in Figure 2.

[0022] Figure 4 shows the estimated electric field (|E|) distribution and optical field transmission of the optical interconnect components when there is no substantial gap between the two optical interconnect components.

[0023] Figure 5 shows a schematic diagram of a cascaded multimode interferometer provided as an optical interconnect structure according to one embodiment.

[0024] Figure 6 shows the estimated electric field (|E|) distribution and optical field transmission of optical interconnect components comprising silicon (Si) waveguides and indium phosphide (InP) waveguides, respectively, with input from the silicon transmitter interconnect to the indium phosphide receiver interconnect.

[0025] Figure 7 shows the estimated electric field (|E|) distribution and optical field transmission of a cascaded multimode interferometer as an optical interconnect component. The cascaded multimode interferometer includes a silicon (Si) waveguide and an indium phosphide (InP) waveguide, with inputs from an indium phosphide transmitter interconnect to a silicon receiver interconnect.

[0026] It should be understood that the accompanying drawings are not necessarily drawn to scale, but are simplified representations of various features shown in the basic principles of the invention. Specific design features of the optical interconnect structures disclosed herein, including, for example, the specific dimensions of the interconnect structures, will depend in part on the particular intended application and usage environment. Some features of the illustrated embodiments have been enlarged or distorted relative to other features to aid clarity. In particular, thin features may be thickened, for example, for clarity of illustration. Implementation

[0027] In the following description, various embodiments will be illustrated with reference to the accompanying drawings, wherein the same reference numerals generally refer to the same components in different views. It will be apparent to those skilled in the art, i.e., those with knowledge or experience in the art, that the optical interconnect structures disclosed herein can be used and designed in various ways. The embodiments described below illustrate the general principles of the present invention for integrating at least two different optical chips to suit applications designed with its optical interconnect structure. Other embodiments applicable to other applications will also be apparent to those skilled in the art given this disclosure.

[0028] This disclosure relates to an integrated chip-to-chip photonic device, particularly an optical interconnect structure. The optical interconnect structure includes transmitter and receiver structures disposed on different optical chips, arranged in an operative manner to ensure efficient optical transmission between the different optical chips. The optical interconnect structure can be used as part of a photonic integrated circuit (PIC) package structure to optically connect different optical chips together.

[0029] This disclosure relates to an integrated photonic device, particularly an optical interconnect structure. The optical interconnect structure includes connected optical components, each component comprising one or more cascaded multimode interferometers (MMIs) disposed on two different optical wafer regions. This connection arrangement enables highly efficient optical transmission between the interconnect components. The optical interconnect structure can be used as part of a large-wafer coupling structure or a wafer-to-wafer coupling structure, for example, in large-wafer architectures and multifunctional inter-wafer integration architectures.

[0030] The optical interconnect structure includes an optical interconnect transmitter and an optical interconnect receiver. Each optical interconnect transmitter and receiver further includes at least the following components: one or more transmitter multimode interferometers, and one or more receiver multimode interferometers connected to the one or more transmitter multimode interferometers to ensure efficient optical coupling between them. The one or more transmitter multimode interferometers are used to transmit optical signals from the aforementioned optical structure on a first optical wafer, via the one or more receiver multimode interferometers, to a subsequent optical structure on a second optical wafer. The optical multimode interferometer may include a wide waveguide, wherein the width of the waveguide is at least five times the width of the input port or input optical waveguide of the multimode interferometer. Alternatively, the optical multimode interferometer may include a tapered optical waveguide disposed between the input and / or output optical ports and the multimode interferometer.

[0031] The layout of optical interconnect structures, such as the type of multimode interferometer, the positional relationship of the input port / optical waveguide relative to the multimode interferometer, and the relative positions of the multimode interferometers in two different wafer regions, may lead to differences in the positioning accuracy of components within the interconnect structure of the optical multimode interferometer due to the application of the optical interconnect structure. For example, in large-scale in-wafer applications, multimode interferometers located in the wafer regions at both ends may be misaligned laterally (horizontally), or in inter-wafer integration applications, they may be misaligned simultaneously in both vertical and lateral (or horizontal) directions, or only in the vertical direction, or they may be aligned. Typically, when the relative position between optical couplers (on the transmitter and receiver sides) is offset (this offset can be in the x, y, or z direction), optical transmission will decrease significantly, i.e., optical coupling loss may increase substantially. However, using the optical transmitter and receiver interconnect structure disclosed herein, the sensitivity to relative position can be significantly reduced. For example, when the lateral offset is 0.5 micrometers, using the embodiments disclosed herein, the coupling loss can be reduced to approximately 0.5 dB. This results in better performance (lower coupling loss) compared to typical wafer-to-wafer optical coupling methods (such as edge couplers and grating couplers). In other words, the optical interconnect structure disclosed herein does not require or includes edge couplers and grating couplers.

[0032] These layout considerations necessitate configuring the optical interconnect structure to ensure efficient optical transmission via it. This can be achieved by designing an optical multimode interferometer that focuses the light field within the structure onto discontinuous regions, specifically between two different wafer regions. The required operating wavelength range—that is, the range of operating wavelengths required for the application in which the optical interconnect unit is used—is another consideration. At least one multimode interferometer, or cascaded multimode interferometer, in each wafer region is configured to address these considerations, and the size of the multimode interferometer is optimized for the optical interconnect structure design.

[0033] In one example, a multimode interferometer provides a method for spatially focusing a light field by configuring it to spatially focus the optical amplitude of the light field on a specific portion of the optical interconnect structure. This focusing concentrates the light field into a spot significantly smaller than the width of the light field at most other locations along the multimode interferometer on the optical interconnect unit. Therefore, the multimode interferometer configured to spatially focus the light field amplitude makes the optical interconnect structure insensitive to discontinuities in two different optical wafer regions.

[0034] The components of the optical interconnect structure are positioned such that an optical signal can be efficiently propagated from the first of at least one multimode interferometer to the second of at least one multimode interferometer via the optical interconnect structure. Thus, at least one receiver multimode interferometer receives the optical field that has passed through at least one transmitter multimode interferometer in the optical interconnect structure.

[0035] At least one multimode interferometer can be implemented as a wide optical rib or channel waveguide, a periodic waveguide structure, or a photonic crystal structure, positioned on a substrate carrying optical interconnect structures. The waveguide of the multimode interferometer includes an input port, an output port, and a body connecting the input and output ports. However, some multimode interferometers (also known as edge multimode interferometers) may not have input or output ports because these edge multimode interferometers are arranged in or near discontinuous regions.

[0036] The optical interconnect structure will be described in more detail below with reference to the accompanying drawings.

[0037] Referring to FIG1, a schematic block diagram 100 of an optical interconnect structure 101 is disclosed according to certain embodiments, comprising an optical interconnect transmitter 110 and an optical interconnect receiver 120 in an assembly arrangement. The optical interconnect transmitter 110 includes at least one transmitter multimode interferometer 111 arranged on an interconnect transmitter wafer substrate 130. The optical interconnect receiver 120 includes at least one receiver multimode interferometer 121 arranged on an interconnect receiver wafer substrate 140. The interconnect transmitter wafer substrate 130 and the interconnect receiver wafer substrate 140 are provided by different optical wafers (also referred to as a first optical wafer and a second optical wafer) and are positioned close to each other. Due to the structural discontinuity between the first optical wafer and the second optical wafer, a discontinuous region is introduced between the interconnect transmitter wafer substrate and the interconnect receiver wafer substrate. This discontinuous region may refer to a contact (gap-free) interface between the interconnect transmitter wafer substrate 130 and the interconnect receiver wafer substrate 140, or a gap between the interconnect transmitter wafer substrate 130 and the interconnect receiver wafer substrate 140.

[0038] In at least the embodiments shown in Figures 1 and 5, the optical interconnect transmitter 110 includes a plurality of multimode interferometers 111 (also referred to as transmitter multimode interferometers) connected in series with each other via their waveguide ports 150 (including input and output ports). In other words, the output port of the aforementioned transmitter multimode interferometer is connected in series with the input port of the subsequent transmitter multimode interferometer. However, the multimode interferometer 112 closest to the edge of the interconnect transmitter wafer substrate (also referred to as the transmitter edge multimode interferometer, i.e., the one closest to the optical interconnect receiver 120 among the transmitter multimode interferometers 111) does not include or has an output port.

[0039] The optical interconnect receiver 120 includes a plurality of multimode interferometers 121 (also referred to as receiver multimode interferometers), which are connected in series with each other via their waveguide ports 150 (including input and output ports). In other words, the output port of the aforementioned receiver multimode interferometer is connected in series with the input port of the subsequent receiver multimode interferometer. However, the multimode interferometer 122 closest to the edge of the interconnect receiver wafer substrate (also referred to as the receiver edge multimode interferometer, i.e., the one closest to the optical interconnect transmitter 110 or transmitter edge multimode interferometer 112 among the receiver multimode interferometers 121) does not include or has an input port.

[0040] Optical interconnect transmitter 110 includes an input port 151 (also referred to as the optical interconnect transmitter input port) having a waveguide width configured to ensure single-mode optical transmission (typically a small width, e.g., approximately 0.5 micrometers for approximately 1.550 micrometer optical wavelength transmission). The transmitter input port 151 is closest to and coupled to a first receiver multimode interferometer, which is furthest from the transmitter edge multimode interferometer 112 compared to the other multimode interferometers of the optical interconnect transmitter 110. Optical interconnect transmitter 110 includes an output port (also referred to as the optical interconnect transmitter output port) having a waveguide width configured to ensure multimode optical transmission (typically a larger width, e.g., greater than 1.0 micrometer for approximately 1.55 micrometer optical wavelength transmission). The transmitter output port 152 is closest to and coupled to the transmitter output multimode interferometer 112 compared to the other multimode interferometers of the optical interconnect transmitter 110.

[0041] The optical interconnect receiver 120 includes an input port 152 (also referred to as the receiver input port) connected to the transmitter output port of the optical interconnect transmitter 110. The transmitter output port is closest to and coupled to a first receiver multimode interferometer 122, which is furthest from the receiver edge multimode interferometer 122 compared to the other multimode interferometers 121 of the optical interconnect receiver 120. In this disclosure, the same reference numeral 152 is used to refer to both the transmitter output port and the receiver input port, as they are connected. The optical interconnect receiver 120 includes an output port 153 (also referred to as the receiver output port) having a waveguide width (typically a small width, e.g., approximately 0.5 micrometers for approximately 1.550 micrometer optical wavelength transmission) configured to ensure single-mode optical transmission. The receiver output port 153 is coupled to a first receiver multimode interferometer, which is furthest from the receiver edge multimode interferometer 122 compared to the other multimode interferometers of the optical interconnect receiver 120.

[0042] In the discontinuous region, two multimode interferometers 112, 122, respectively from the optical interconnect transmitter 110 and the optical interconnect receiver 120, are coupled, for example, connected, to facilitate optical transmission therebetween by coupling the transmitter output port to the receiver input port. The junction region 152 includes the transmitter output port and the receiver input port.

[0043] The bonding region 152 can be implemented by arranging the transmitter output port and the receiver input port in contact with each other. Alternatively, the bonding region can also be implemented by arranging a refractive index matching material 152 connecting the transmitter output port and the receiver input port. In this alternative, the bonding region 152 includes the transmitter output port, the receiver input port, and the refractive index matching material. The refractive index matching material 152 is configured to substantially match the refractive indices of the optical waveguides of the optical interconnect transmitter 110 and the optical interconnect receiver 120. The refractive index matching material 152 can be a liquid, such as an oil, gel, or adhesive.

[0044] Optical interconnect transmitter 110 and optical interconnect receiver 120 can be advantageously and efficiently optically coupled through two different interconnect regions. The optical interconnect transmitter 110 and receiver 120 can be implemented using a phase mask, which can be made of, for example, silicon (Si), polycrystalline silicon, silicon nitride (Si3N4), silicon dioxide, germanium (Ge), lithium niobate (Li3NbO3), polymer materials, group III-V compounds (i.e., alloys containing elements of groups III and V in the periodic table), and group II-VI compounds (i.e., alloys containing elements of groups II and VI in the periodic table).

[0045] Multimode interferometers can be selected from a variety of different types. For example, a multimode interferometer can be a total internal reflection-based multimode interferometer (this type constitutes the vast majority of multimode interferometers traditionally used in integrating photonics). Alternatively, an in-plane scattering multimode interferometer can be used, such as a multimode interferometer formed from a photonic crystal (also utilizing total internal reflection) and metamaterials. Each multimode interferometer can be composed of, for example, at least one of silicon (Si), silicon dioxide (SiO2), barium titanate (BaTiO3), lithium niobate (Li3NbO3), indium phosphide (InP), group III-V compounds, group II-VI compounds, and polymeric materials. For example, a multimode interferometer can support any optical waveguide mode, such as transverse electric mode and transverse magnetic mode.

[0046] Any number of multimode interferometers can be configured according to the optical interconnect structure 101 selected for the application. Both the optical interconnect emitter edge and the optical interconnect receiver edge closest to the junction region 153 can contain structures for inducing optical field focusing, so that the optical interconnect structure 110 is insensitive to structural discontinuities.

[0047] In one embodiment (see optical interconnect structure 162 in FIG. 2), the optical interconnect transmitter 110 may include at most one multimode interferometer (single multimode interferometer), rather than multiple multimode interferometers, and the optical interconnect receiver 120 may also include at most one multimode interferometer (single multimode interferometer), rather than multiple multimode interferometers. Therefore, the single multimode interferometer of the optical interconnect transmitter 110 may be indicated by feature 111 or 112 in the figures, while the single multimode interferometer of the optical interconnect receiver 120 may be indicated by feature 121 or 122 in the figures. Other features of this embodiment are similar to those of the optical interconnect structure 101 in FIG. 1.

[0048] Figure 2 shows a schematic top view of an optical interconnect structure 162 according to an embodiment of the present disclosure. In the optical interconnect structure 162, a refractive index matching material 152 is disposed at a structural discontinuity, which would cause optical loss during transmission between the optical wafers disposed on the interconnect transmitter wafer substrate 130 and the interconnect receiver wafer substrate 140 if the refractive index matching material were not provided at the discontinuity. According to the present disclosure, the use of the optical interconnect structure ensures high efficiency in transmission from the optical interconnect transmitter 110 to the optical interconnect receiver 120.

[0049] In the embodiment of Figure 2, the transmitter waveguide and the receiver waveguide contain different materials. In other words, the waveguide materials spanning different optical wafers can be different. In other embodiments, the transmitter waveguide and the receiver waveguide can contain the same material.

[0050] Figure 3 shows a schematic isometric view of the optical interconnect structure 162 in Figure 2.

[0051] Figure 4 shows the estimated electric field (|E|) distribution and optical field transmission in optical interconnect component embodiments with different multimode interferometer waveguide materials in optical interconnect structure 162. In Figure 4, it can be observed that the electric field changes relatively little between the optical input waveguide of the optical interconnect transmitter 110 and the optical output waveguide of the optical interconnect receiver 120. Therefore, even after coupling between different optical interconnect structures, the electric field remains relatively undisturbed despite some optical losses during the transmission of the optical field from the optical interconnect transmitter 110 to the optical interconnect receiver 120. Given the high optical field transmission efficiency, the optical interconnect structure disclosed herein is suitable for optical coupling between different optical wafers. For example, an optical interconnect structure may include the following parameters: the silicon (Si) multimode interferometer (MMI) of the optical interconnect transmitter may have a length of 65 micrometers and a width of 6 micrometers, while the indium phosphide (InP) multimode interferometer (MMI) of the optical interconnect receiver may have a length of 65 micrometers and a width of 6 micrometers.

[0052] Figure 5 is a schematic diagram showing an optical interconnect structure 602 with multiple cascaded multimode interferometers 621, 622, 623, and 624. The embodiment in Figure 5 enables the adjustment or improvement of the optical transmission efficiency between the optical interconnect transmitter and the optical interconnect receiver by changing the optical phase of the waveguide modes between the cascaded structures, for example, by introducing refractive index matching materials into the waveguides between the cascaded interconnect structures.

[0053] Figure 6 shows the estimated electric field (|E|) distribution and optical field transmission in a multimode interferometer embodiment of a silicon (Si) and indium phosphide (InP) waveguide optical interconnect component according to the embodiment of Figure 5, wherein the input from the silicon optical interconnect transmitter 110 is transmitted to the indium phosphide optical interconnect receiver. The same observations as in Figure 4 can be obtained for Figure 6.

[0054] In one example, the optical interconnect structure 101 may include the following parameters: the silicon multimode interferometer of the optical interconnect transmitter 110 may have a cascaded length of 30 µm and 24 µm and a width of 6 µm, while the indium phosphide multimode interferometer of the optical interconnect receiver 120 may have a length of 30 µm and a width of 6 µm. The gap between the optical interconnect transmitter 110 and the optical interconnect receiver 120 may be 5 µm, and the optical interconnect transmitter 110 and the optical interconnect receiver 120 are connected by refractive index matching oil. The difference in length between the two silicon multimode interferometers is due to different tapered widths (from 1.5 µm to 0.5 µm in the first cascade and from 0.5 µm to 3 µm in the second cascade). This tapered structure connects two cascaded structures within the same optical wafer. To compensate for optical transmission losses and / or device performance variability / inconsistency caused by fabrication inconsistencies, the optical phase of the tapered regions between cascaded optical interconnect transmitters or receivers can be selectively adjusted, for example, by applying a refractive index matching material, such as oil, to the tapered regions. This effectively changes the effective refractive index of the tapered regions, thereby altering their optical phase to improve optical signal transmission between the optical interconnect structures.

[0055] Figure 7 shows the estimated electric field (|E|) distribution and optical field transmission of the cascaded multimode interferometer in the embodiment shown in Figure 6 as a photonic interconnect component, where the input from the indium phosphide (InP) optical interconnect transmitter 120 is transmitted to the silicon (Si) optical interconnect receiver 120. The same observations as in Figure 4 can be obtained for Figure 7.

[0056] From the foregoing disclosure and detailed description of specific embodiments, it will be apparent to those skilled in the art that various modifications, additions, and other alternative embodiments can be implemented without departing from the true scope and spirit of the invention. The selection and description of the embodiments discussed are intended to provide the best illustration of the principles of the invention and its practical application, thereby enabling those skilled in the art to use the invention in various embodiments and make various modifications suitable for a particular intended use. All such modifications and variations fall within the scope of the invention, defined by the appended claims, and to be interpreted fairly, legally, and reasonably to the extent appropriate.

[0057] 100: Block Diagram 101, 162, 602: Optical interconnect structure 110: Optical Interconnect Transmitter 111: Multimode Interferometer / Transmitter Multimode Interferometer 112: Multimode Interferometer / Emitter Edge Multimode Interferometer 120: Optical Interconnect Receiver 121: Multimode Interferometer / Receiver Multimode Interferometer 122: Multimode Interferometer / Receiver Edge Multimode Interferometer 130: Interconnect transmitter chip substrate 140: Interconnect receiver chip substrate 150: Waveguide Port 151: Input Port / Optical Interconnect Transmitter Input Port 152: Input Port / Receiver Input Port / Output Port / Transmitter Output Port / Gathering Area / Refractive Index Matching Material 153: Output Port / Receiver Output Port / Connection Area 621, 622, 623, 624: Cascaded Multimode Interferometers

Claims

1. An optical interconnect structure, comprising: An optical interconnect transmitter having at least one transmitter multimode interferometer, each transmitter multimode interferometer having at least one transmitter waveguide; An optical interconnect receiver includes at least one receiver multimode interferometer, each receiver multimode interferometer having at least one receiver waveguide, wherein the optical interconnect transmitter and the optical interconnect receiver are respectively arranged on different optical wafers with a discontinuity region therebetween; and a refractive index matching material is arranged in the discontinuity region, wherein the material originates from the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer, and is closest to the discontinuity region among the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer, two multimode interferometers are connected such that the transmitter waveguides of the two multimode interferometers are connected to the receiver waveguides, wherein the transmitter waveguides of the two multimode interferometers and the receiver waveguides are connected by the refractive index matching material, wherein the refractive index matching material is configured to match the refractive index of at least one transmitter waveguide with the refractive index of at least one receiver waveguide, wherein the refractive index matching material comprises a liquid, the liquid being an oil, gel, or adhesive.

2. The optical interconnect structure as described in claim 1, wherein, The at least one transmitter multimode interferometer includes a plurality of transmitter multimode interferometers connected in series, and the at least one receiver multimode interferometer includes a plurality of receiver multimode interferometers connected in series.

3. The optical interconnect structure as described in any one of claims 1 to 2, wherein, The at least one transmitter multimode interferometer includes a single transmitter multimode interferometer, and the at least one receiver multimode interferometer includes a single receiver multimode interferometer.

4. The optical interconnect structure as described in any one of claims 1 to 2, wherein, At least a portion of the transmitter waveguide and receiver waveguide of each of the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer include a width that is at least five times the width of the input port of each of the transmitter waveguide and the receiver waveguide.

5. The optical interconnect structure as described in any one of claims 1 to 2, wherein, At least a portion of the transmitter multimode interferometer and the receiver multimode interferometer of each of the at least one transmitter multimode interferometers includes a width that tapers in opposite directions from the input port of each of the transmitter and receiver waveguides to the output port of each of the transmitter and receiver waveguides.

6. The optical interconnect structure as described in any one of claims 1 to 2, wherein, The two multimode interferometers are misaligned laterally.

7. The optical interconnect structure as described in any one of claims 1 to 2, wherein, The two multimode interferometers are misaligned in the vertical direction.

8. The optical interconnect structure as described in any one of claims 1 to 2, wherein, The at least one transmitter waveguide and the at least one receiver waveguide contain different materials.

9. The optical interconnect structure as described in claim 8, wherein, The materials of the transmitter waveguide and the receiver waveguide are selected from the group consisting of silicon (Si), polycrystalline silicon, silicon nitride (Si3N4), silicon dioxide, germanium (Ge), lithium niobate (Li3NbO3), polymer materials, and group III-IV compounds.

10. An optical interconnect structure, comprising: An optical interconnect transmitter having at least one transmitter multimode interferometer, each transmitter multimode interferometer having at least one transmitter waveguide; An optical interconnect receiver includes at least one receiver multimode interferometer, each receiver multimode interferometer having at least one receiver waveguide; a first optical wafer region and different second optical wafer regions, wherein the optical interconnect transmitter and the optical interconnect receiver are respectively arranged on the first optical wafer region and the second optical wafer region, with a discontinuity region interposed therebetween; and a refractive index matching material arranged in the discontinuity region, wherein the material originates from the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer, and is closest to the discontinuity region among the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer, two multimode interferometers are connected such that the transmitter waveguides of the two multimode interferometers are connected to the receiver waveguides, wherein the transmitter waveguides of the two multimode interferometers and the receiver waveguides are connected by the refractive index matching material, wherein the refractive index matching material is configured to match the refractive index of at least one transmitter waveguide with the refractive index of at least one receiver waveguide, wherein the refractive index matching material comprises a liquid, the liquid being an oil, gel, or adhesive.

11. The optical interconnect structure as described in any one of claims 10 to 11, wherein, The at least one transmitter multimode interferometer includes a plurality of transmitter multimode interferometers connected in series, and the at least one receiver multimode interferometer includes a plurality of receiver multimode interferometers connected in series.

12. The optical interconnect structure as described in any one of claims 10 to 11, wherein, The at least one transmitter multimode interferometer includes a single transmitter multimode interferometer, and the at least one receiver multimode interferometer includes a single receiver multimode interferometer.

13. The optical interconnect structure as described in any one of claims 10 to 11, wherein, At least a portion of the transmitter waveguide and receiver waveguide of each of the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer include a width that is at least five times the width of the input port of each of the transmitter waveguide and the receiver waveguide.

14. The optical interconnect structure as described in any one of claims 10 to 11, wherein, At least a portion of the transmitter multimode interferometer and the receiver multimode interferometer of each of the at least one transmitter multimode interferometers includes a width that tapers in opposite directions from the input port of each of the transmitter and receiver waveguides to the output port of each of the transmitter and receiver waveguides.

15. The optical interconnect structure as described in any one of claims 10 to 11, wherein, The two multimode interferometers are misaligned laterally.

16. The optical interconnect structure as described in any one of claims 10 to 1, wherein, The two multimode interferometers are misaligned in the vertical direction.

17. The optical interconnect structure as described in any one of claims 10 to 11, wherein, The at least one transmitter waveguide and the at least one receiver waveguide contain different materials.

18. The optical interconnect structure as claimed in claim 17, wherein the material of the transmitter waveguide and the material of the receiver waveguide are selected from the group consisting of silicon (Si), polycrystalline silicon, silicon nitride (Si3N4), silicon dioxide, germanium (Ge), lithium niobate (Li3NbO3), polymer materials, and group III-IV compounds.

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