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

[0001] OPTICAL INTERLINK STRUCTURE

[0002] FIELD OF THE INVENTION

[0003]

[0001] The present disclosure relates to the field of integrated photonics, large-scale chip, optical chip-to-chip interconnects, and optical hybrid integration. An optical interlink unit having one or more interconnect structures is disclosed, the one or more interlink structures optimising an optical signal propagation from one optical chip to another.

[0004] BACKGROUND OF THE INVENTION

[0005]

[0002] Optical interlink is used to integrate multiple designed or fabricated regions such that optical signal transmission between these regions remain largely unperturbed. Optical interlink structures are needed to integrate at least two distinct optical chips.

[0006]

[0003] In optical chip-to-chip coupling, the structural discontinuity between optical chips can contribute to optical signal loss at the discontinuous region. Such signal loss is undesirable. Optical interlink structures are needed to ensure that signal transmission is unaffected from possible discontinuities across the optical chips.

[0007]

[0004] Optical interlink is used to integrate two distinct optical chips. This is especially needed to integrate different chips of different optical materials which can have properties that are suited for different functionalities. For example, in order to integrate multiple functionalities with high performance on a single platform, optical coupling between optical chips of different materials is essential. However, although multiple chip-to-chip implementations have been proposed, the approaches either have low inter-chip optical coupling efficiency, requires difficult inter-chip alignment, or have complex structural designs. It can be prohibitively complex to design a structure that address the aforementioned problems. Although hybrid integration have been largely adopted for such integration, such hybrid integration approaches typically have tradeoffs in spectral bandwidth, optical coupling efficiency, or manufacturability and mechanical stability.

[0008]

[0005] It is desirable to realize an optical interlink approach that addresses the above and other tradeoffs and shortcomings.SUMMARY OF THE INVENTION

[0009]

[0006] According to an aspect, an optical interlink structure is provided which comprises:

[0010] an optical interlink transmitter having at least one transmitter multimode interferometer, each transmitter multimode interferometer having at least one transmitter waveguide; and

[0011] an optical interlink receiver having at least one receiver multimode interferometer, each receiver multimode interferometer having at least one receiver waveguide;

[0012] wherein the optical interlink transmitter and the optical interlink receiver are respectively arranged on distinct optical chips and interpose a discontinuous region therebetween,

[0013] wherein two multimode interferometers, respectively from the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer, and being closest to the discontinuous region among the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer, are conjoined such that the transmitter waveguide and the receiver waveguide of the two multimode interferometers are conjoined.

[0014]

[0007] According to an aspect, an optical interlink structure is provided which comprises:

[0015] an optical interlink transmitter having at least one transmitter multimode interferometer, each transmitter multimode interferometer having at least one transmitter waveguide;

[0016] an optical interlink receiver having at least one receiver multimode interferometer, each receiver multimode interferometer having at least one receiver waveguide; and

[0017] a first optical chip region and a distinct second optical chip region, wherein the optical interlink transmitter and the optical interlink receiver are respectively arranged on the first optical chip region and the second optical chip region and interpose a discontinuous region therebetween,

[0018] wherein two multimode interferometers, respectively from the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer, and being closest to the discontinuous region among the at least onetransmitter multimode interferometer and the at least one receiver multimode interferometer, are conjoined such that the transmitter waveguide and the receiver waveguide of the two MM Is are conjoined.

[0019]

[0008] In embodiments of the above aspects, the waveguides of the two multimode interferometers are arranged in mutual contact.

[0020]

[0009] In embodiments of the above aspects, the optical interlink structure further comprises: an index-matching material arranged at the discontinuous region, wherein the waveguides of the two multimode interferometers are conjoined by the indexmatching material.

[0021]

[0010] In embodiments of the above aspects, the at least one transmitter multimode interferometer includes a plurality of cascaded transmitter multimode interferometers, and wherein the at least one receiver multimode interferometer includes a plurality of cascaded receiver multimode interferometers.

[0022]

[0011] In embodiments of the above aspects, the at least one transmitter multimode interferometer includes a single transmitter multimode interferometer, and wherein the at least one receiver multimode interferometer includes a single receiver multimode interferometer.

[0023]

[0012] In embodiments of the above aspects, the waveguide of each multimode interferometer of at least some of the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer includes a width which is at least five times a width of an input port of the waveguide.

[0024]

[0013] In embodiments of the above aspects, the waveguide of each multimode interferometer of at least some of the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer includes a width which inversely tapers from an input port of the waveguide to an output port of the waveguide.

[0025]

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

[0026]

[0015] In embodiments of the above aspects, the two multimode interferometers are vertically misaligned.

[0027]

[0016] In embodiments of the above aspects, the different materials are selected from the group consisting of silicon (Si), polysilicon, silicon nitride (SisN4), silicon dioxide, germanium (Ge), lithium niobate (LisNbOs), polymer, and lll-IV compound.

[0028]

[0017] In embodiments of the above aspects, the at least one transmitter waveguide and the at least one receiver waveguide include different materials.

[0018] From the foregoing disclosure and following more detailed description of various embodiments it will be apparent to those skilled in the art that the present invention provides a significant advance in the technology to provide a low loss optical transmission between two distinct chip regions. Particularly significant in this regard is the potential the invention affords for providing enhanced optical transmission with a broad optical bandwidth with high manufacturability between two distinct chip regions. This prevents loss of signal information across a broad spectral wavelength, which would otherwise exist due to the lack of modal focusing at the discontinuity point between the chip regions. Additional features and advantages of various embodiments will be better understood in view of the detailed description provided below.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030]

[0019] Figure 1 shows a schematic diagram of an optical interlink structure having two distinct optical chips , in accordance with some embodiments;

[0031]

[0020] Figure 2 shows a schematic top view of optical interlink structure having distinct waveguide materials, in accordance with an embodiment;

[0032]

[0021] Figure 3 shows a schematic isometric view of the optical interlink structure of Figure 2;

[0033]

[0022] Figure 4 shows an estimated resulting electric field (|E|) profile and transmission of optical field of optical interlink components with no substantial gap between the two optical interlink components;

[0034]

[0023] Figure 5 shows a schematic diagram in which cascaded multimode interferometers are provided as optical interlink structures, in accordance with an embodiment;

[0035]

[0024] Figure 6 shows an estimated resulting electric field (|E|) profile and transmission of optical field of optical interlink components which include silicon (Si) and indium phosphide (InP) waveguides respectively, and input from a Si transmitter interlink to an InP receiver interlink;

[0036]

[0025] Figure 7 shows an estimated resulting electric field (|E|) profile and transmission of optical field of cascaded multimode interferometers as optical interlink components which include Si and InP waveguides respectively, and input from an InP transmitter interlink to a Si receiver interlink;

[0026] It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the optical interlink structures as disclosed here, including, for example, the specific dimensions of the interlink structures, will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments have been enlarged or distorted relative to others to help provide clear understanding. In particular, thin features may be thickened, for example, for clarity of illustration.

[0037] DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

[0038]

[0027] In the following description, various embodiments are described with reference to the drawings, where like reference characters generally refer to the same parts throughout the different views. It will be apparent to those skilled in the art, that is, to those who have knowledge or experience in this area of technology, that many use and design variations are possible for the optical interlink structure disclosed herein. The following described embodiments illustrate the general principles of the invention to integrate at least two distinct optical chips to suit applications for which its optical interlink structure is designed. Other embodiments suitable for other applications will be apparent to those skilled in the art given the benefit of this disclosure.

[0039]

[0028] The present disclosure relates to an integrated chip-to-chip photonic device, specifically an optical interlink structure. An optical interlink structure includes a transmitter and receiver structure on different optical chips operatively arranged to ensure efficient optical transmission across different optical chips. The optical interlink structure may be part of a photonic integrated circuit (PIC) packaged structure to optically connect distinct optical chips together.

[0040]

[0029] 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. The optical interlink structure may be part of a large chip coupling structure, or chip-to-chip coupling structure used in, for example, large-scale chip architectures and multi-functional interchip integrated architectures.

[0041]

[0030] The optical interlink structure includes an optical interlink transmitter and an optical interlink receiver which in turn include at least the following components: one or more transmitter multimode interferometers; and one or more receiver multimode interferometers conjoined to the one or more transmitter multimode interferometers to ensure efficient optical coupling between the two. The one or more transmitter multimode interferometers serves to transmit optical signal from preceding optical structures on the first optical chip to the succeeding optical structures on the second optical chip via the one or more multimode receiver interferometers. The optical multimode interferometers may include broad optical waveguides for which the width of the waveguide is at least five times the width of the input port of or input optical waveguide to the multimode interferometers. Alternatively, the optical multimode interferometers may include tapered optical waveguides with the tapers between the input and / or output optical ports and the multimode interferometers.

[0042]

[0031] The layout of the optical interlink structure, such as the type of multimode interferometer; and the relative position of the input ports / optical waveguides to the multimode interferometers and the relative positions of the multimode interferometers at the two distinct chip regions, may differ in positioning accuracy of the components in the optical interlink structure to which the optical multimode interferometer belongs depending on the applications of the optical interlink structure. For example, the multimode interferometers at both ends of the chip regions may be laterally (horizontally) misaligned for large-scale intrachip applications, or both vertically and laterally (or horizontally) misaligned for interchip integration applications, or may be vertically misaligned, or may be aligned. Typically, when the relative positions of optical couplers (on the transmitter and receiver sides) are shifted (which may be in x, y- or z- positions), optical transmission can decrease significantly, i.e., optical coupling loss can be substantial or substantially increased. However, using the optical transmitter and receiver interlink structures of the present disclosure, sensitivity to relative positions is substantially decreased. For example, with a horizontal misalignment of 0.5 pm, the coupling loss may be reduced to about 0.5 dB using the embodiments of the present disclosure. This results in better performance (less coupling loss) as compared to typical chip-to-chip optical coupling approaches such as edge coupler and grating couplers. In other words, the optical interlink structure ofthe present disclosure does not require or is devoid of edge coupler and grating coupler.

[0043]

[0032] These layout considerations result in requiring for an optical interlink structure to be configured such that highly efficient optical transmission through the optical interlink structure can be ensured. This can be achieved by designing the optical multimode interferometers such that the optical field in the structure focuses at the discontinuous region i.e., between the two distinct chip regions. The operating wavelength range, required by the application for which the optical interlink unit is used, is another consideration point. The at least one multimode interferometer or the cascade of multimode interferometers on each of the chip regions are configured to address the above considerations and dimensions of the multimode interferometers are optimised for the optical interlink structure design.

[0044]

[0033] In an example, the multimode interferometer provides a means to spatially concentrate an optical field by being configured to spatially focus an optical amplitude of the optical field onto specific portions of the optical interlink structure. This focusing concentrates the optical field into spots of significantly smaller widths compared to the width of the optical field at most other locations along the multimode interferometers on the optical interlink unit. As such, the multimode interferometers being configured to spatially focus an optical field amplitude allows the optical interlink structure to be insensitive to discontinuity at the two distinct optical chip regions.

[0045]

[0034] The components of the optical interlink structure are positioned so that the optical signal can propagate efficiently through the optical interlink structure from the first of the at least one multimode interferometer to the second of the at least one multimode interferometer. Accordingly, the at least one receiver multimode interferometer receives an optical field that has passed through the at least one transmitter multimode interferometer in the optical interlink structure.

[0046]

[0035] The at least one multimode interferometer may be realised as broad optical rib or channel waveguide, corrugated waveguide structures or photonic crystal structures positioned on the substrate on which the optical interlink structure is disposed. The waveguide of a multimode interferometer comprises an input port, an output port, and a main body interconnecting the input port and the output port. However, some multimode interferometers (alternatively referred to as edge multimode interferometers) may be devoid of an input port or an output port as theseedge multimode interferometers are arranged at or proximate to the discontinuous region.

[0047]

[0036] The optical interlink structure is described in greater detail below in conjunction with the accompanying figures.

[0048]

[0037] Referring to Figure 1 , a schematic block diagram 100 of an optical interlink structure 101, according to some embodiments, is disclosed which comprises a conjoined arrangement of an optical interlink transmitter 110 and an optical interlink receiver 120. The optical interlink transmitter 110 comprises at least one transmitter multimode interferometer 111 arranged on an interlink transmitter chip substrate 130. The optical interlink receiver 120 comprises at least one receiver multimode interferometer 121 arranged on an interlink receiver chip substrate 140. The interlink transmitter chip substrate 130 and the interlink receiver chip substrate 140 are respectively provided by distinct optical chips (alternatively referred to as first and second optical chips) and are positioned in close proximity to each other. A discontinuous region is interposed between the interlink transmitter chip substrate and the interlink receiver chip substrate as a result of structural discontinuity between the first and second optical chips. The discontinuous region may refer to a contact (nongap) interface between the interlink transmitter chip substrate 130 and the interlink receiver chip substrate 140, or a gap between the interlink transmitter chip substrate 130 and the interlink receiver chip substrate 140.

[0049]

[0038] In an embodiment illustrated by at least Figures 1 and 5, the optical interlink transmitter 110 comprises a plurality of multimode interferometer 111 (alternatively referred to as transmitter multimode interferometers) which are cascaded with one another via their waveguide ports 150, including input and output ports. In other words, an output port of a preceding transmitter multimode interferometer is cascaded with an input port of a succeeding transmitter multimode interferometer. However, the multimode interferometer 112 (alternatively referred to as transmitter edge multimode interferometer), which is closest to the interlink transmitter chip substrate edge (i.e., closest to the optical interlink receiver 120 among the transmitter multimode interferometers 111), does not comprise or is devoid of an output port.

[0050]

[0039] The optical interlink receiver 120 comprises a plurality of multimode interferometers 121 (alternatively referred to as receiver multimode interferometers) which are cascaded with one another via their waveguide ports 150, including input and output ports. In other words, an output port of a preceding receiver multimodeinterferometer is cascaded with an input port of a succeeding receiver multimode interferometer. However, the multimode interferometer 122 (alternatively referred to as receiver edge multimode interferometer), which is closest to the interlink receiver chip substrate edge (i.e., closest to the optical interlink transmitter 110 or transmitter edge multimode interferometer 112 among the receiver multimode interferometers 121 ), does not comprise or is devoid of an input port.

[0051]

[0040] The optical interlink transmitter 110 includes an input port 151 (alternatively referred to as optical interlink transmitter input port) having a waveguide width configured to ensure single-mode optical transmission (generally a smaller width, e.g., about 0.5 pm for about 1.550 pm 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 as compared to other multimode interferometers of the optical interlink transmitter 110. The optical interlink transmitter 110 includes an output port (alternatively referred to as optical interlink transmitter output port) having a waveguide width configured to ensure multimode optical transmission (generally a larger width, e.g., greater than 1 .0 pm for about 1.55 pm optical wavelength transmission). The transmitter output port 152 is closest to the transmitter output multimode interferometer 112 as compared to other multimode interferometers of the optical interlink transmitter 110 and is coupled to the transmitter output multimode interferometer 112.

[0052]

[0041] The optical interlink receiver 120 includes an input port 152 (alternatively referred to as receiver input port) which is conjoined to the transmitter output port of the optical interlink 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 as compared to other multimode interferometers 121 of the optical interlink receiver 120. In the present disclosure, the same reference number 152 is used to refer to both the transmitter output port and the receiver input port as they are conjoined. The optical interlink receiver 120 includes an output port 153 (alternatively referred to as receiver output port) having a waveguide width configured to ensure single-mode optical transmission (generally a smaller width, e.g., about 0.5 pm for about 1.550 pm optical wavelength transmission). The receiver output port 153 is coupled to the first receiver multimode interferometer which is furthest from the receiver edge multimode interferometer 122 as compared to other multimode interferometers of the optical interlink receiver 120.

[0042] At the discontinuous region, two multimode interferometers 112, 122, which are respectively from the optical interlink transmitter 110 and the optical interlink receiver 120, are coupled, e.g., conjoined, to facilitate optical transmission therebetween by coupling the transmitter output port with the receiver input port. The conjoined region 152 includes both the transmitter output port and the receiver input port.

[0053]

[0043] The conjoined region 152 may be implemented by arranging the transmitter output port and the receiver input port in mutual contact. Alternatively, the conjoined region may be implemented by arranging an index-matching material 152 which interconnects the transmitter output port and the receiver input port. In this alternative, the conjoined region 152 includes the transmitter output port, the receiver input port, and the index-matching material. The index-matching material 152 is configured to approximately match refractive indices of optical waveguide of the optical interlink transmitter 110 and optical interlink receiver 120. The index-matching material 152 may be a liquid, e.g. oil, a gel, or an adhesive.

[0054]

[0044] The optical interlink transmitter 110 and optical interlink receiver 120 advantageously optically couple light efficiently through the two distinct interlink regions. The optical interlink transmitter 110 and receiver 120 may be implemented by phase masks fabricated from, for example, any of silicon (Si), polysilicon, silicon nitride (SisIX ), silicon dioxide, germanium (Ge), lithium niobate (LisNbOs) a polymer, a lll-V compound (that is, an alloy containing elements from Groups III and V in the periodic table, and a ll-VI compound (that is, an alloy containing elements from Groups II and VI in the Periodic Table).

[0055]

[0045] The multimode interferometers may be selected from any of several different types of multimode interferometers. For example, the multimode interferometer can be a total internal reflection-based (which makes up the overwhelming majority of multimode interferometer traditionally used in integrated photonics). Alternatively, an in-plane scattering multimode interferometer may be used, such as multimode interferometer formed from photonic crystals (which also use total internal reflection) and metamaterials. A composition of each of the plurality of multimode interferometers can be, for example, at least one of Si, SiO2, BaTiOs, LisNbOs, InP, a lll-V compound, a ll-VI compound, and a polymer, for example. The multimode interferometers can support any of the optical waveguide modes, for example, Transverse Electric mode and Transverse Magnetic mode.

[0046] There can be any arbitrary number of multimode interferometers based on a configuration of the optical interlink structure 101 selected for an application. Both the optical interlink transmitter edge and optical interlink receiver edge, which are closest to the conjoined region 153, may comprise structures that induce optical field focusing to collectively result in the optical interlink structure 110 being insensitive to structural discontinuity.

[0056]

[0047] In an embodiment (see optical interlink structure 162 of Figure 2), the optical interlink transmitter 110 may comprise at most one multimode interferometer (a single multimode interferometer) instead of a plurality of multimode interferometers, while the optical interlink receiver 120 may comprise at most one multimode interferometer (a single multimode interferometer) instead of a plurality of multimode interferometer. Hence, the single multimode interferometer of the optical interlink transmitter 110 may be represented by feature 111 or 112 in the drawings, while the single multimode interferometer of the optical interlink receiver 120 may be represented by feature 121 or 122 in the drawings. Other features of this embodiment are similar to the optical interlink structure 101 of Figure 1.

[0057]

[0048] Figure 2 shows a schematic top view of optical interlink structure 162 according to an embodiment of the present disclosure. In the optical interlink structure 162, an index-matching material 152 is arranged at a structural discontinuity which would otherwise cause optical loss in the transmission between optical chips of which the interlink transmitter chip substrate 130 and the interlink receiver chip substrate 140 are arranged. In accordance with the present disclosure, the use of optical interlink structures ensures transmission from the optical interlink transmitter 110 to the optical interlink receiver 120 is efficient.

[0058]

[0049] In the embodiment of Figure 2, the transmitter waveguide and the receiver waveguide include different materials. In other words, the waveguide materials across distinct optical chips may be different. In other embodiment, the transmitter waveguide and the receiver waveguide may include the same material.

[0059]

[0050] Figure 3 shows a schematic isometric diagram of the optical interlink structure 162 of Figure 2.

[0060]

[0051] Figure 4 shows the estimated resulting electric field (|E|) profiles and transmission of optical field of embodiments of optical interlink components of the different multimode interferometer waveguide materials in optical interlink structure 162. In Figure 4, it can be observed that the electric field is relatively unchanged fromthe optical input waveguide of the optical transmitter interlink 110 and the optical output waveguide of the optical receiver interlink 120. Therefore, the electric field is relatively unperturbed even after being coupled between different optical interlink structures notwithstanding some optical loss as optical field transmits from the optical transmitter interlink 110 to the optical receiver interlink 120. Given that the optical field transmission efficiency is high, the optical interlink structure of the present disclosure is suitable for coupling light between different optical chips. In an example, an optical interlink structure may include the following parameters: a Si multimode interferometer of an optical interlink transmitter may have a length of 65 pm and a width of 6 pm while an InP multimode interferometer of an optical interlink receiver may have a length of 65 pm and a width of 6 pm.

[0061]

[0052] Figure 5 is a schematic diagram showing an optical interlink structure 602 having a plurality of cascaded multimode interferometers 621, 622, 623, 624. The embodiment of Figure 5 enables a convenience or ability to tune or enhance optical transmission efficiency between the optical interlink transmitter and the optical interlink receiver by varying the optical phase of the waveguide modes between the cascaded structures, e.g., by interposing an index-matching material on the waveguides between the cascaded interlink structures.

[0062]

[0053] Figure 6 shows estimated resulting electric field (| E|) profiles and transmission of optical field of embodiments of optical interlink components of Si and InP waveguides in the multimode interferometers, where an input from Si optical interlink transmitter 110 is transferred to InP optical interlink receiver, according to the embodiment of Figure 5. The same observations of Figure 4 may be drawn for Figure 6.

[0063]

[0054] In an example, an optical interlink structure 101 may include the following parameters: Si multimode interferometers of an optical interlink transmitter 110 may have a length of 30 pm and 24 pm cascaded, a width of 6 pm while InP multimode interferometers of an optical interlink receiver 120 may have a length of 30 pm and a width of 6 pm. A gap between the optical interlink receiver 110 and the optical interlink receiver 120 may be 5 pm with an index matching oil to interconnect the interlink receiver 110 and the optical interlink receiver 120. The difference in lengths of the two Si multimode interferometers is due to the different taper widths (from 1.5 pm to 0.5 pm from first cascade, and 0.5 pm to 3 pm to second cascade. The tapers link the two cascaded structures within the same optical chip. In order to compensate opticaltransmission loss and / or device performance variability / consistency due to fabrication inconsistencies, the optical phases at the tapers between the cascaded optical interlink transmitter or receiver can be alternatively adjusted, e.g., by applying index matching material, e.g., oil, onto the taper region. This effectively changes the effective refractive index of the taper region, and therefore shifts the optical phase at the taper region to enhance the optical signal transmission between the optical interlink structures.

[0064]

[0055] Figure 7 shows the estimated resulting electric field (|E|) profiles and transmission of optical field of embodiments of cascaded multimode interferometers as photonic interlink components, as illustrated in Figure 6, wherein input from InP optical interlink transmitter 120 is transferred to Si optical receiver interlink receiver 120. The same observations of Figure 4 may be drawn for Figure 7.

[0065]

[0056] From the foregoing disclosure and detailed description of certain embodiments, it will be apparent that various modifications, additions and other alternative embodiments are possible without departing from the true scope and spirit of the invention. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to use the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

AMENDED CLAIMSreceived by the International Bureau on 19 May 2026 (19.05.2026) Claims1. An optical interlink structure, comprising:an optical interlink transmitter having at least one transmitter multimode interferometer, each transmitter multimode interferometer having at least one transmitter waveguide; andan optical interlink receiver having at least one receiver multimode interferometer, each receiver multimode interferometer having at least one receiver waveguide;wherein the optical interlink transmitter and the optical interlink receiver are respectively arranged on distinct optical chips and interpose a discontinuous region therebetween,wherein two multimode interferometers, respectively from the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer, and being closest to the discontinuous region among the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer, are conjoined such that the transmitter waveguide and the receiver waveguide of the two multimode interferometers are conjoined.

2. An optical interlink structure, comprising:an optical interlink transmitter having at least one transmitter multimode interferometer, each transmitter multimode interferometer having at least one transmitter waveguide;an optical interlink receiver having at least one receiver multimode interferometer, each receiver multimode interferometer having at least one receiver waveguide; anda first optical chip region and a distinct second optical chip region, wherein the optical interlink transmitter and the optical interlink receiver are respectively arranged on the first optical chip region and the distinct second optical chip region and interpose a discontinuous region therebetween,wherein two multimode interferometers, respectively from the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer, and being closest to the discontinuous region among the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer, are conjoined such that the transmitter waveguide and the receiver waveguide of the two multimode interferometers are conjoined, wherein the discontinuous region is one of: a contact (non-gap) interface between the first optical chip region and the distinct second optical chip region, and a gap between the first optical chip region and the distinct second optical chip region.

3. The optical interlink structure of claim 1 or claim 2, wherein the waveguides of the two multimode interferometers are arranged in mutual contact.

4. The optical interlink structure of claim 1 or claim 2, further comprising:an index-matching material arranged at the discontinuous region, wherein the waveguides of the two multimode interferometers are conjoined by the index-matching material.

5. The optical interlink structure of claim 4, wherein the index-matching material is configured to approximately match a refractive index of the at least one transmitter waveguide and a refractive index of the at least one receiver waveguide.

6. The optical interlink structure of claim 4 or 5, wherein the index-matching material includes a liquid, preferably an oil, a gel, or an adhesive.

7. The optical interlink structure of any one of claim 1 to claim 6, wherein the at least one transmitter multimode interferometer includes a plurality of cascaded transmitter multimode interferometers, and wherein the at least one receiver multimode interferometer includes a plurality of cascaded receiver multimode interferometers.

8. The optical interlink structure of any one of claim 1 to claim 6, wherein the at least one transmitter multimode interferometer includes a single transmitter multimodeinterferometer, and wherein the at least one receiver multimode interferometer includes a single receiver multimode interferometer.

9. The optical interlink structure of any one of claim 1 to claim 8, wherein the waveguide of each multimode interferometer of at least some of the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer includes a width which is at least five times a width of an input port of the waveguide.

10. The optical interlink structure of any one of claim 1 to claim 8, wherein the waveguide of each multimode interferometer of at least some of the at least one transmitter multimode interferometer and the at least one receiver multimode interferometer includes a width which inversely tapers from an input port of the waveguide to an output port of the waveguide.

11. The optical interlink structure of any one of claim 1 to claim 10, wherein the two multimode interferometers are laterally misaligned.

12. The optical interlink structure of any one of claim 1 to claim 11 , wherein the two multimode interferometers are vertically misaligned.

13. The optical interlink structure of any one of claim 1 to claim 12, wherein the at least one transmitter waveguide and the at least one receiver waveguide include different materials.

14. The optical interlink structure of claim 13, wherein the different materials are selected from the group consisting of silicon (Si), polysilicon, silicon nitride (SisN4), silicon dioxide, germanium (Ge), lithium niobate (LisNbOs), polymer, and lll-IV compound.

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