CN115692518A - On-chip integrated structure - Google Patents

Abstract

The disclosed embodiment provides an on-chip integrated structure, including: a substrate; a waveguide layer located above the substrate, the waveguide layer having therein a silicon waveguide, a transition waveguide and a lithium niobate waveguide extending in a first direction; the first direction is parallel to a surface of the substrate; the silicon waveguide, the transition waveguide and the lithium niobate waveguide are sequentially stacked along the direction far away from the surface of the substrate; the transition waveguide has a first portion and a second portion arranged in sequence along the first direction; a projection of the first portion on the substrate at least partially coincides with a projection of the silicon waveguide on the substrate; a projection of the second portion on the substrate at least partially coincides with a projection of the lithium niobate waveguide on the substrate.

Description

On-chip integrated structure

Technical Field

The present disclosure relates to the field of optical communication devices, and relates to, but is not limited to, an on-chip integrated structure.

Background

The silicon photonic technology is a new generation technology for developing and integrating optical devices by using the existing Complementary Metal Oxide Semiconductor (CMOS) process based on silicon and silicon-based materials. The silicon photon technology combines the characteristics of ultra-large scale and ultra-high precision manufacturing of an integrated circuit technology and the advantages of ultra-high speed and ultra-low power consumption of the photon technology, and is a subversive technology for coping with the failure of the moore's law. This combination contributes to scalability of semiconductor wafer fabrication, thereby enabling cost reduction.

Because lithium niobate materials have the advantages of high electro-optic response, high intrinsic bandwidth, wide transparent window, good thermal stability and the like, in recent years, lithium niobate films have been widely used for various active optical devices. However, the component library of lithium niobate thin films is not complete enough, so that the application thereof is limited. Therefore, how to integrate the lithium niobate thin film and the silicon optical platform becomes a problem to be solved urgently at present.

Disclosure of Invention

In view of this, the disclosed embodiments provide a chip integrated structure, including:

a substrate;

a waveguide layer located above the substrate, the waveguide layer having therein a silicon waveguide, a transition waveguide and a lithium niobate waveguide extending in a first direction; the first direction is parallel to a surface of the substrate; the silicon waveguide, the transition waveguide and the lithium niobate waveguide are sequentially stacked along the direction far away from the surface of the substrate;

the transition waveguide is provided with a first part and a second part which are sequentially arranged along the first direction; a projection of the first portion on the substrate at least partially coincides with a projection of the silicon waveguide on the substrate; a projection of the second portion on the substrate at least partially coincides with a projection of the lithium niobate waveguide on the substrate.

In some embodiments, the difference between the refractive index of the transition waveguide and the refractive index of the lithium niobate waveguide is less than a preset value.

In some embodiments, the material of the transition waveguide is silicon nitride.

In some embodiments, the width of the transition waveguide remains constant at the first portion;

the width of the transition waveguide is gradually reduced along the first direction in the second portion.

In some embodiments, the silicon waveguide has a third portion and a fourth portion arranged in sequence along the first direction; a projection of the fourth portion on the substrate at least partially coincides with a projection of the first portion on the substrate;

the width of the silicon waveguide remains constant in the third portion;

the width of the silicon waveguide is gradually reduced along the first direction at the fourth portion.

In some embodiments, the integrated on-chip structure further comprises:

a layer of germanium material over the third portion of the silicon waveguide, the layer of germanium material in contact with the silicon waveguide; the projection region of the germanium material layer on the substrate and the projection region of the transition waveguide on the substrate are mutually spaced;

the layer of germanium material and a portion of the silicon waveguide in the third portion form a photodetector.

In some embodiments, an upper surface of the germanium material layer is no higher than an upper surface of the lithium niobate waveguide.

In some embodiments, the width of the lithium niobate waveguide remains constant in the first direction.

In some embodiments, the integrated on-chip structure further comprises:

the electro-optical modulator is connected with the lithium niobate waveguide; wherein a modulation arm of the electro-optical modulator is provided with a ridge waveguide connected with the lithium niobate waveguide; the lithium niobate waveguide has a first width and the ridge waveguide has a second width;

the ridge waveguide is connected with the lithium niobate waveguide through a gradual change waveguide, and the width of the gradual change waveguide is gradually changed from the first width to the second width along the first direction.

In some embodiments, there is a gap between the silicon waveguide and the transition waveguide and a gap between the transition waveguide and the lithium niobate waveguide in a direction perpendicular to the surface of the substrate.

In some embodiments, the integrated on-chip structure further comprises:

and the insulating structure layer is positioned between the waveguide layer and the substrate.

In some embodiments, the integrated on-chip structure further comprises:

and the waveguide covering layer is positioned in the waveguide layer and covers the silicon waveguide, the transition waveguide and the lithium niobate waveguide.

In the on-chip integrated structure provided by the embodiment of the disclosure, the first portion of the transition waveguide is at least partially overlapped with the projection of the silicon waveguide on the substrate, and the second portion of the transition waveguide is at least partially overlapped with the projection of the lithium niobate waveguide on the substrate. Therefore, the transition waveguide is positioned between the silicon waveguide and the lithium niobate waveguide in the vertical direction, on one hand, the lithium niobate waveguide can be coupled with the silicon waveguide through the transition waveguide so as to improve the performance and the integration level of the on-chip integrated structure; on the other hand, the transition waveguide enables the distance between the silicon waveguide and the lithium niobate waveguide in the vertical direction to be larger, and is beneficial to integrating the photoelectric detector above the silicon waveguide.

Drawings

FIG. 1 is a schematic diagram of an on-chip integrated structure provided by an embodiment of the present disclosure;

FIG. 2 is a top view of a transition waveguide in an integrated on-chip structure provided by an embodiment of the present disclosure;

FIG. 3 is a top view of a silicon waveguide in an integrated on-chip structure provided by an embodiment of the present disclosure;

FIG. 4 is a schematic diagram of another integrated structure on a chip provided by an embodiment of the present disclosure;

FIG. 5 is a top view of an electro-optic modulator in an integrated on-chip configuration provided by an embodiment of the present disclosure;

fig. 6 is a schematic diagram of another on-chip integrated structure provided in the embodiments of the present disclosure.

Detailed Description

To facilitate an understanding of the present disclosure, exemplary embodiments of the present disclosure will be described in more detail below with reference to the associated drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present disclosure. It will be apparent, however, to one skilled in the art, that the present disclosure may be practiced without one or more of these specific details. In some embodiments, some technical features that are well known in the art are not described in order to avoid obscuring the present disclosure; that is, not all features of an actual implementation may be described herein, and well-known functions and constructions may not be described in detail.

In general, terms may be understood at least in part from the context of their use. For example, the term "one or more" as used herein may be used to describe any feature, structure, or characteristic in the singular or may be used to describe a combination of features, structures, or characteristics in the plural, depending, at least in part, on the context. Similarly, terms such as "a" or "the" may also be understood to convey a singular use or to convey a plural use, depending, at least in part, on the context. Additionally, the term "based on" may be understood as not necessarily intended to convey an exclusive set of factors, and may instead allow for the presence of additional factors that are not necessarily expressly described, again depending at least in part on the context.

Unless otherwise defined, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

In order to thoroughly understand the present disclosure, detailed steps and detailed structures will be set forth in the following description in order to explain the technical aspects of the present disclosure. The following detailed description of the preferred embodiments of the present disclosure, however, the present disclosure may have other embodiments in addition to these detailed descriptions.

As shown in fig. 1, the disclosed embodiment provides an on-chip integrated structure 10, including:

a substrate 100;

a waveguide layer 110 over the substrate 100, the waveguide layer 110 having therein a silicon waveguide 120, a transition waveguide 130, and a lithium niobate waveguide 140 extending in a first direction; the first direction is parallel to the surface of the substrate 100; the silicon waveguide 120, the transition waveguide 130 and the lithium niobate waveguide 140 are sequentially stacked along a direction away from the surface of the substrate 100;

the transition waveguide 130 has a first portion 131 and a second portion 132 arranged in sequence along the first direction; the projection of the first portion 131 on the substrate 100 at least partially coincides with the projection of the silicon waveguide 120 on the substrate 100; the projection of the second portion 132 on the substrate 100 at least partially coincides with the projection of the lithium niobate waveguide 140 on the substrate 100.

In the embodiments of the present disclosure, the material of the substrate 100 may include a simple substance semiconductor material, such as Silicon (Si), germanium (Ge), etc., a compound semiconductor material, such as gallium nitride (GaN), gallium arsenide (GaAs), or indium phosphide (InP), etc., and a compound semiconductor material, such as Silicon Germanium (SiGe), silicon On Insulator (SOI), germanium on Insulator (GeOI), etc. The substrate 100 may also be doped or include doped and undoped regions in the substrate. It should be understood that in order to clearly illustrate the structures of the various layers in the drawings, the dimensional proportion of the structures of the various layers may not be the same as the actual structure.

Here and hereinafter, the first direction is a direction parallel to the surface of the substrate 100, and for clarity of description of the present disclosure, the first direction is taken as an X direction in the drawings in the following embodiments as an example. It should be noted, however, that the following description of the embodiments with respect to the direction is only for illustrating the present disclosure, and is not intended to limit the scope of the present disclosure.

The waveguide layer 110 is located above the substrate 100 in a direction perpendicular to the substrate surface, i.e., the Z direction. The waveguide layer 110 has therein a silicon waveguide 120, a transition waveguide 130, and a lithium niobate waveguide 140 extending in the X direction and parallel to each other. The silicon waveguide 120, the transition waveguide 130, and the lithium niobate waveguide 140 are sequentially stacked and arranged along the Z direction. In the Z direction, the silicon waveguide 120 and the transition waveguide 130 may not be in direct contact with each other, and the transition waveguide 130 and the lithium niobate waveguide 140 may not be in direct contact with each other, and for example, the waveguide layer 110 may have a covering material that covers the silicon waveguide 120, the transition waveguide 130, and the lithium niobate waveguide 140, and the covering material has a different refractive index from the material of the above waveguides, for example, the covering material may be silicon dioxide.

In some embodiments, the lithium niobate waveguide may be a lithium niobate thin film and directly bonded to the silicon optical portion with the silicon waveguide, thereby achieving evanescent field coupling of the lithium niobate waveguide and the silicon waveguide. However, the silicon waveguide bonded here is only a passive waveguide, and a photodetector cannot be further integrated on the silicon waveguide, resulting in limitation of the function and performance of the integrated structure on chip formed by bonding. The photoelectric detector can be integrated by continuously growing a layer of germanium on the material layer on which the silicon waveguide is positioned, however, the thickness of the germanium-silicon photoelectric detector is larger, so that if a bonding technology is adopted to form the lithium niobate waveguide on the silicon optical part, the distance between the lithium niobate waveguide and the silicon waveguide is larger, and therefore mode fields of the lithium niobate waveguide and the silicon waveguide cannot be close to each other, and evanescent field coupling cannot be formed. Therefore, the direct bonding method can realize the coupling of the lithium niobate waveguide and the passive silicon waveguide, but is not convenient for realizing the integration of the lithium niobate waveguide and the photoelectric detector.

In the disclosed embodiment, transition waveguide 130 may be located between silicon waveguide 120 and lithium niobate waveguide 140 in the Z-direction, and silicon waveguide 120 and lithium niobate waveguide 140 may indirectly form evanescent field coupling through transition waveguide 130. The transition waveguide 130 has a first portion 131 and a second portion 132 arranged in the X direction. The first portion 131 at least partially coincides with the projection of the silicon waveguide 120 on the substrate 100, i.e., the silicon waveguide 120 and the transition waveguide 130 may be coupled by the first portion 131; the second portion 132 may at least partially coincide with the projection of the lithium niobate waveguide 140 onto the substrate 100, i.e., the transition waveguide 130 and the lithium niobate waveguide 140 may be coupled through the second portion 132. Thus, the silicon waveguide 120, the transition waveguide 130 and the lithium niobate waveguide 140 may form a stepped multilayer structure, so as to implement evanescent field coupling between the lithium niobate waveguide 140 and the silicon waveguide 120, that is, the on-chip integrated structure 10 is a heterogeneous three-dimensional integrated structure, which is beneficial to improving the performance and integration level of the on-chip integrated structure 10. In addition, because the transition waveguide 130 is located between the silicon waveguide 120 and the lithium niobate waveguide 140, and the three are stacked in a staggered manner, in an actual manufacturing process, a germanium material layer can also be grown in a region which is not shielded by the transition waveguide 130 above the silicon waveguide 120, so that the lithium niobate waveguide 140 can be coupled to a germanium-silicon photodetector, which is beneficial to exerting performance advantages of various materials in the on-chip integrated structure 10, and simultaneously expands functions of the on-chip integrated structure 10.

In some embodiments, the silicon waveguide and the lithium niobate waveguide can be coupled through a multilayer transition waveguide to improve mode field coupling efficiency, so as to meet actual performance requirements of an on-chip integrated structure. It can be understood that the more the number of layers of the transition waveguide, the better the continuity of the change in the mode spot; in addition, in the multilayer waveguide coupling structure, the thickness of each layer of waveguide can be the same, so as to improve the stability of the mode spot change.

In some embodiments, the difference between the refractive index of the transition waveguide 130 and the refractive index of the lithium niobate waveguide 140 is less than a preset value.

In the embodiment of the present disclosure, in order to realize low-loss coupling between the transition waveguide 130 and the lithium niobate waveguide 140, the refractive indexes of the transition waveguide 130 and the lithium niobate waveguide 140 need to be close to each other, that is, the difference between the refractive index of the transition waveguide 130 and the refractive index of the lithium niobate waveguide 140 is smaller than a preset value. It is understood that the preset value is greater than or equal to 0, and the difference between the refractive indexes of the transition waveguide 130 and the lithium niobate waveguide 140 is an absolute value. The preset value can be adjusted according to the actual process and the product requirement.

In some embodiments, the material of the transition waveguide 130 is silicon nitride.

In the embodiment of the present disclosure, since the refractive indexes of the silicon nitride and the lithium niobate material are relatively close, the transition waveguide 130 may be made of silicon nitride, so as to reduce the loss of interlayer coupling between the transition waveguide 130 and the lithium niobate waveguide 140, and the problems of mode field mismatch and the like. In addition, the technology for forming the silicon nitride waveguide in the silicon optical process is mature, which is beneficial to simplifying the manufacturing process of the on-chip integrated structure 10 and saving the cost.

In some embodiments, as shown in fig. 2, which is a top view of transition waveguide 130, the width of transition waveguide 130 remains constant at first portion 131;

the width of the transition waveguide 130 is gradually reduced in the first direction at the second portion 132.

In the embodiment of the present disclosure, the width of the first portion 131 in the transition waveguide 130 may be a fixed value, the first portion 131 may be used for signal transmission, and the first portion 131 may be a straight waveguide, for example. The width of the second portion 132 in the transition waveguide 130 is gradually reduced along the X direction, and the second portion 132 may be used for mode conversion between the transition waveguide 130 and the lithium niobate waveguide, so as to implement interlayer coupling, for example, the second portion 132 may be a wedge-shaped waveguide. Thus, the interlayer coupling loss between the transition waveguide 130 and the lithium niobate waveguide is small, which is beneficial to improving the transmission efficiency.

In some embodiments, as shown in fig. 3, which is a top view of the silicon waveguide 120, the silicon waveguide 120 has a third portion 121 and a fourth portion 122 arranged in sequence along the first direction; the projection of the fourth portion 122 on the substrate 100 at least partially coincides with the projection of the first portion on the substrate 100;

the width of the silicon waveguide 120 remains constant in the third portion 121;

the width of the silicon waveguide 120 is gradually decreased along the first direction at the fourth portion 122.

In the disclosed embodiment, the silicon waveguide 120 has a third section 121 and a fourth section 122 arranged in order along the X-direction. Wherein the fourth portion 122 at least partially coincides with the projection of the first portion of the transition waveguide on the substrate, i.e. the silicon waveguide 120 and the transition waveguide may be interlayer coupled by the fourth portion 122 and the first portion.

Wherein the width of the third portion 121 in the silicon waveguide 120 may be a fixed value, the third portion 121 may be used for signal transmission, and exemplarily, the third portion 121 may be a straight waveguide. The fourth portion 122 of the silicon waveguide 120 has a width gradually decreasing along the X direction, and the fourth portion 122 may be used for mode conversion between the silicon waveguide 120 and the transition waveguide, for example, the fourth portion 122 may be a wedge-shaped waveguide. Thus, the coupling loss between the silicon waveguide 120 and the transition waveguide is small, which is beneficial to improving the transmission efficiency.

In some embodiments, as shown in fig. 4, the on-chip integrated structure 10 further includes:

a layer of germanium material 150 over the third portion 121 of the silicon waveguide 120, the layer of germanium material 150 being in contact with the silicon waveguide 120; the projection area of the germanium material layer 150 on the substrate 100 and the projection area of the transition waveguide 130 on the substrate 100 are spaced from each other;

the layer of germanium material 150 and a portion of the silicon waveguide 120 in the third portion 121 form a photodetector.

In the embodiment of the present disclosure, since the preparation process of the germanium material is compatible with the silicon photo process, the third portion 121 may further have a germanium material layer 150 thereon, that is, the germanium material layer 150 may be located on a region which is not shielded by the transition waveguide 130 above the silicon waveguide 120. The germanium material Layer 150 may be formed over the material Layer on which the silicon waveguide 120 is located by a CMOS process such as Deposition, including but not limited to Chemical Vapor Deposition (CVD), atomic Layer Deposition (ALD), physical Vapor Deposition (PVD), or the like. Notably, there is no contact between the layer of germanium material 150 and the transition waveguide 130.

Since the silicon material is transparent to light in the O-band and the C-band, the silicon material cannot be used as a photodetector. The germanium material has an absorption effect on light in an O wave band and a C wave band, and is a four-group material with silicon, so that the germanium-silicon structure has great advantages when being used as a photoelectric detector. It will be appreciated that the layer of germanium material 150 may be in direct contact with the silicon waveguide 120 in the third portion 121 to form a photodetector, to enable coupling of the lithium niobate waveguide to the photodetector.

In some embodiments, as shown in fig. 4, the upper surface of the germanium material layer 150 is no higher than the upper surface of the lithium niobate waveguide 140.

In the disclosed embodiment, since transition waveguide 130 is located between silicon waveguide 120 and lithium niobate waveguide 140 in the Z-direction, the upper surface of thicker layer of germanium material 150 may be no higher than the upper surface of lithium niobate waveguide 140. That is, the thickness of the on-chip integrated structure 10 is not additionally increased while integrating the photodetector, so that the structure layout is optimized to improve the integration level of the on-chip integrated structure 10.

In some embodiments, as shown in fig. 5, which is a partial top view of the on-chip integrated structure 10, the width of the lithium niobate waveguide 140 remains constant in the first direction.

In the disclosed embodiment, the width of the lithium niobate waveguide 140 remains constant along the X-direction, where the lithium niobate waveguide 140 may be, for example, a strip waveguide. Because the refractive index of the transition waveguide can be close to that of the lithium niobate waveguide 140, the lithium niobate waveguide 140 can effectively reduce the loss in the coupling process by using the strip waveguide.

In some embodiments, as shown in fig. 5, the integrated on-chip structure 10 further comprises:

an electro-optical modulator 160 connected to the lithium niobate waveguide 140; wherein, the modulation arm of the electro-optical modulator 160 has a ridge waveguide 161 connected with the lithium niobate waveguide 140; the lithium niobate waveguide 140 has a first width w1, and the ridge waveguide 161 has a second width w2;

the ridge waveguide 161 and the lithium niobate waveguide 140 are connected by a tapered waveguide 162, and the width of the tapered waveguide 162 is tapered from the first width w1 to the second width w2 along the first direction.

In the disclosed embodiment, the modulation arm of the electro-optic modulator 160 has a ridge waveguide 161 therein that is connected to the lithium niobate waveguide 140. The ridge waveguide 161 may have a ridge region and a slab region, and the ridge waveguide 161 has a large confinement factor for light, which is advantageous to improve modulation efficiency. The ridge waveguide 161 may also be a lithium niobate thin film material, and since the lithium niobate material is transparent in the whole telecommunication communication band and has a strong electro-optical effect, the lithium niobate thin film may greatly improve the modulation efficiency of the electro-optical modulator. The modulation arm of the electro-optic modulator 160 may have an electrode structure 163 therein corresponding to the ridge waveguide.

The lithium niobate waveguide 140 and the ridge waveguide 161 in the electro-optical modulator 160 can be connected by a tapered waveguide 162, where the tapered waveguide 162 can also be a lithium niobate thin film material, so as to simplify the manufacturing process. Illustratively, as shown in fig. 5, the lithium niobate waveguide 140 has a first width w1, the ridge waveguide 161 has a second width w2, and the width of the tapered waveguide 162 is tapered from the first width w1 to the second width w2 along the transmission path of the optical signal to reduce mode mismatch and transmission loss. It is understood that, since the ridge waveguide 161 may be divided into a ridge region and a slab region in the Z direction, and widths of the ridge region and the slab region are respectively different, the tapered waveguide 162 may have a two-layer tapered structure corresponding to the ridge region and the slab region, that is, the tapered waveguide 162 is a tapered ridge waveguide. Illustratively, as shown in fig. 5, the width of the ridge region of the tapered waveguide 162 is tapered from a first width w1 to a second width w2, and the width of the slab region of the tapered waveguide 162 is tapered from the first width w1 to the width of the slab region of the ridge waveguide 161, so as to further reduce the transmission loss. In some embodiments, the thicknesses of the lithium niobate waveguide 140 and the ridge waveguide 161 are different, and the thickness of the graded waveguide 162 may be graded along the transmission path of the optical signal.

So, integrated structure 10 on the chip both can utilize the photoelectric detector and all kinds of active, passive devices of silicon optical part, has the high bandwidth low-loss characteristic of lithium niobate electrooptical modulator concurrently again, when realizing better function expansibility, has also satisfied the demand of silicon optical chip to high transmission rate.

In some embodiments, as shown in fig. 4, in a direction perpendicular to the surface of the substrate 100, there is a gap between the silicon waveguide 120 and the transition waveguide 130, and a gap between the transition waveguide 130 and the lithium niobate waveguide 140.

In the embodiment of the present disclosure, in the Z direction, there is a gap between two adjacent waveguides in the on-chip integrated structure 10, that is, none of the silicon waveguide 120, the transition waveguide 130, and the lithium niobate waveguide 140 contact each other. Since the silicon waveguide 120 and the transition waveguide 130, and the transition waveguide 130 and the lithium niobate waveguide 140 are coupled between layers, the coupling efficiency between two adjacent waveguides in the Z direction can be adjusted by changing the size of the gap.

In some embodiments, as shown in fig. 4, the integrated on-chip structure 10 further comprises:

an insulating structure layer 170 between the waveguide layer 110 and the substrate 100.

In the embodiment of the present disclosure, the insulating structure layer 170 is located between the waveguide layer 110 and the substrate 100, and an upper surface of the insulating structure layer 170 is not higher than a lower surface of the silicon waveguide 120. The insulating structure layer 170 may be made of a polymer material, silicon oxide, or the like, and the insulating structure layer 170 may be used to reduce a leakage phenomenon occurring at the substrate 100, so as to protect the integrated structure 10 on the whole chip.

In some embodiments, as shown in fig. 4, the integrated on-chip structure 10 further comprises:

a waveguide cladding layer 180 disposed in the waveguide layer 110, the waveguide cladding layer 180 cladding the silicon waveguide 120, the transition waveguide 130, and the lithium niobate waveguide 140.

In embodiments of the present disclosure, the waveguide cladding layer 180 may be located in the waveguide layer 110, and the waveguide cladding layer 180 claddes the silicon waveguide 120, the transition waveguide 130, and the lithium niobate waveguide 140. Waveguide cladding layer 180 may be a polymer, oxide, or like material to protect the waveguides from contaminants and to increase the structural strength of integrated on-chip structure 10.

In some embodiments, the coupling of the silicon waveguide and the lithium niobate waveguide may be achieved by an evanescent field based bonding technique, where the silicon optical portion where the silicon waveguide is located has only passive waveguides. The reason is that the thickness of the germanium-silicon photoelectric detector is large, so that the mode fields of the silicon waveguide and the lithium niobate waveguide which are connected with the germanium-silicon detector cannot be close to each other, and the lithium niobate waveguide cannot be integrated with the germanium-silicon detector. Therefore, although the lithium niobate thin film material has the performance advantages of high bandwidth and high modulation efficiency, the lithium niobate thin film material cannot be integrated with a photoelectric detector in practical application; in addition, because the oblique angle structure of the side wall in the lithium niobate thin film etching process is difficult to realize polarization beam splitting and rotating devices, compared with a mature silicon optical process platform, the component library of the lithium niobate thin film is incomplete, and functional elements capable of being integrated are fewer.

As shown in fig. 6, another alternative on-chip integrated structure 20 provided by the embodiment of the present disclosure, the on-chip integrated structure 20 includes:

a silicon waveguide 220, a transition waveguide 230, a lithium niobate waveguide 240, a waveguide covering layer 280, an insulating structure layer 270 and a substrate 200; wherein, the material of the transition waveguide 230 is silicon nitride;

the transition waveguide 230 is divided into a first part 231 and a second part 232 along the X direction, the first part 231 is a straight waveguide for signal transmission, the second part 232 is a wedge-shaped waveguide for mode conversion with the lithium niobate waveguide 240, and the first part 231 and the second part 232 are sequentially connected and arranged to form a planar structure;

the silicon waveguide 220 is divided into a third part 221 and a fourth part 222 along the X direction, the third part 221 is a straight waveguide for signal transmission, the fourth part 222 is a wedge-shaped waveguide for mode conversion with the transition waveguide 230, and the third part 221 and the fourth part 222 are sequentially connected and arranged to form a planar structure;

the transition waveguide 230 is located above the fourth portion 222 and does not contact each other;

the lithium niobate waveguide 240 is positioned above the second portion 232 and is not in contact with each other;

the lithium niobate waveguide 240 adopts a strip waveguide structure; the lithium niobate waveguide 240 is converted into a ridge waveguide in the modulation arm area of the electro-optic modulator through a gradual change waveguide;

the waveguide cladding layer 280 wraps the silicon waveguide 220, the transition waveguide 230 and the lithium niobate waveguide 240;

the insulating structure layer 270 is located below the lower surface of the waveguide cladding layer 280;

the substrate 200 is disposed below the lower surface of the insulating structure layer 270;

the fourth portion 222 and the first portion 231 form a first order coupling region, and the second portion 232 and the lithium niobate waveguide 240 form a second order coupling region.

In the embodiment of the present disclosure, the optical field on the lithium niobate waveguide 240 is coupled into the transition waveguide 230 first, and then coupled into the silicon waveguide 220 by the transition waveguide 230, so as to realize the integration of the silicon optical process and the lithium niobate thin film process, the silicon optical portion continues to use the high-speed germanium-silicon detector and the mature passive device library thereof, and the lithium niobate thin film is only used in the structure requiring high-performance electro-optical modulation, thereby solving the problem of the lack of functional elements of the current lithium niobate thin film platform.

Because the transition waveguide 230 is made of silicon nitride material and has a refractive index very close to that of the lithium niobate waveguide 240, the lithium niobate waveguide 240 in the second-order coupling region adopts a strip waveguide structure to reduce loss caused by dissipation in a slab region during coupling, and the transition waveguide is converted into a ridge waveguide in a modulation arm region of the electro-optical modulator through a tapered waveguide.

According to the on-chip integrated structure provided by the embodiment of the disclosure, the transition waveguide is arranged to couple the silicon waveguide and the lithium niobate waveguide, so that a silicon optical process and a lithium niobate thin film process are integrated, the technical problem of on-chip integration of multi-material multifunctional devices is solved, heterogeneous three-dimensional integration is realized, the integration level is high, and the performance of a communication system chip is effectively improved; in addition, the on-chip integrated structure provided by the disclosure has the advantage of simple manufacturing process.

It should be noted that the features disclosed in the several structural embodiments provided in the present disclosure may be arbitrarily combined to obtain a new structural embodiment without conflict.

It should be appreciated that reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It should be understood that, in various embodiments of the present disclosure, the sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present disclosure. The above-mentioned serial numbers of the embodiments of the present disclosure are merely for description and do not represent the merits of the embodiments.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or apparatus that comprises the element.

In the several embodiments provided in the present disclosure, it should be understood that the disclosed structure may be implemented in other ways. The above-described device embodiments are merely illustrative, for example, the division of the unit is only a logical functional division, and there may be other division ways in actual implementation, such as: multiple units or components may be combined, or may be integrated into another system, or some features may be omitted, or not implemented. In addition, the coupling, direct coupling or communication connection between the components shown or discussed may be through some interfaces, and the indirect coupling or communication connection between the devices or units may be electrical, mechanical or in other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units; can be located in one place or distributed on a plurality of network units; some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, all the functional units in the embodiments of the present disclosure may be integrated into one processing unit, or each unit may be separately regarded as one unit, or two or more units may be integrated into one unit; the integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit.

The above description is only for the specific embodiments of the present disclosure, but the scope of the present disclosure is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present disclosure, and all the changes or substitutions should be covered within the scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims (12)

1. An on-chip integrated structure, comprising:

a substrate;

a waveguide layer located above the substrate, the waveguide layer having therein a silicon waveguide, a transition waveguide and a lithium niobate waveguide extending in a first direction; the first direction is parallel to a surface of the substrate; the silicon waveguide, the transition waveguide and the lithium niobate waveguide are sequentially stacked along the direction far away from the surface of the substrate;

the transition waveguide has a first portion and a second portion arranged in sequence along the first direction; a projection of the first portion on the substrate at least partially coincides with a projection of the silicon waveguide on the substrate; a projection of the second portion on the substrate at least partially coincides with a projection of the lithium niobate waveguide on the substrate.

2. The on-chip integrated structure of claim 1, wherein a difference between a refractive index of the transition waveguide and a refractive index of the lithium niobate waveguide is less than a predetermined value.

3. The integrated structure of claim 2, wherein the transition waveguide is made of silicon nitride.

4. The integrated on-chip structure of claim 1, wherein a width of the transition waveguide remains constant at the first portion;

the width of the transition waveguide is gradually reduced along the first direction in the second portion.

5. The integrated structure of claim 4, wherein the silicon waveguide has a third portion and a fourth portion arranged in sequence along the first direction; a projection of the fourth portion on the substrate at least partially coincides with a projection of the first portion on the substrate;

the width of the silicon waveguide remains constant in the third portion;

the width of the silicon waveguide is gradually reduced along the first direction at the fourth portion.

6. The integrated on-chip structure of claim 5, further comprising:

a layer of germanium material over the third portion of the silicon waveguide, the layer of germanium material in contact with the silicon waveguide; the projection region of the germanium material layer on the substrate and the projection region of the transition waveguide on the substrate are mutually spaced;

the layer of germanium material and a portion of the silicon waveguide in the third portion constitute a photodetector.

7. The integrated structure of claim 6, wherein an upper surface of the germanium material layer is no higher than an upper surface of the lithium niobate waveguide.

8. The on-chip integrated structure of claim 1, wherein a width of the lithium niobate waveguide remains constant in the first direction.

9. The integrated on-chip structure of claim 8, further comprising:

the electro-optical modulator is connected with the lithium niobate waveguide; the modulation arm of the electro-optical modulator is provided with a ridge waveguide connected with the lithium niobate waveguide; the lithium niobate waveguide has a first width and the ridge waveguide has a second width;

the ridge waveguide is connected with the lithium niobate waveguide through a gradual change waveguide, and the width of the gradual change waveguide is gradually changed from the first width to the second width along the first direction.

10. The on-chip integrated structure of claim 1, wherein a gap is provided between the silicon waveguide and the transition waveguide and a gap is provided between the transition waveguide and the lithium niobate waveguide in a direction perpendicular to the surface of the substrate.

11. The integrated on-chip structure of claim 1, further comprising:

and the insulating structure layer is positioned between the waveguide layer and the substrate.

12. The integrated on-chip structure of claim 1, further comprising:

and the waveguide covering layer is positioned in the waveguide layer and covers the silicon waveguide, the transition waveguide and the lithium niobate waveguide.

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