Structure for light propagation and method of manufacturing the same, semiconductor device, optical device, and lidar

Abstract

A structure for light propagation, a method for manufacturing the same, a semiconductor device, an optical device, and a laser radar are disclosed. The structure for light propagation includes a first waveguide, a second waveguide, and a light medium structure. The first waveguide has a first refractive index; the second waveguide has a second refractive index; and the light medium structure has a third refractive index. The third refractive index is greater than the first refractive index; and the second refractive index is greater than or equal to the first refractive index and less than or equal to the third refractive index. A first end of the second waveguide is coupled to the first waveguide in a first direction; and a second end of the second waveguide is coupled to the light medium structure in a second direction.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor technology, and in particular to a structure for light propagation and a method for manufacturing the same, a semiconductor device, an optical device, and a lidar. Background Technology

[0002] A photonic chip is a chip based on photonic technology. It uses optical components (such as waveguides, optical modulators, and photodetectors) to process and transmit information on the chip. Compared to electronic chips, photonic chips offer higher data transmission speeds, lower power consumption, and greater bandwidth, making them an important direction for the development of next-generation information technology.

[0003] To meet the needs of information processing or transmission, photonic chips need to meet certain optical requirements, often requiring the integration of multiple optical structures. How to achieve low-loss coupling of optical signals between these optical structures is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] This disclosure provides a structure for light propagation and a method for manufacturing the same, a semiconductor device, an optical device, and a lidar, to reduce light loss during propagation in the semiconductor device.

[0005] In a first aspect, a structure for light propagation is provided, comprising: a first waveguide, a second waveguide, and an optical dielectric structure. The first waveguide has a first refractive index; the second waveguide has a second refractive index; and the optical dielectric structure has a third refractive index. The third refractive index is greater than the first refractive index; the second refractive index is greater than or equal to the first refractive index and less than or equal to the third refractive index. A first end of the second waveguide is coupled to the first waveguide along a first direction; and a second end of the second waveguide is coupled to the optical dielectric structure along a second direction.

[0006] In the above structure, the second waveguide acts as a connector between different optical propagation media (the first waveguide and the optical medium structure), reducing coupling loss during light transmission between them. The second waveguide's refractive index is chosen to be between the first waveguide's first refractive index and the optical medium structure's third refractive index, allowing for a smooth transition between the two. This reduces the need for patterning the optical medium structure, significantly improving processing tolerance and yield, reducing processing complexity, and lowering production costs. This is particularly advantageous when the material of the optical medium structure is not suitable for patterning.

[0007] Optionally, the first waveguide and the optical dielectric structure are made of different materials.

[0008] Optionally, the first waveguide includes a first segment and a second segment, the first segment is coupled to the second segment, and the first width of the first segment is greater than the second width of the second segment; the second waveguide is coupled to the first segment, the third width of the first end is less than the first width, and the fourth width of the second end is greater than the first width.

[0009] In the above structure, in the first waveguide, the first width of the first segment is greater than the second width of the second segment. This allows light to diverge more in the first segment, enabling light to enter the second waveguide from the first waveguide and reducing coupling loss between the two waveguides. The width of the first waveguide narrows to the second width in the second segment, reducing the equivalent refractive index in the first waveguide. This promotes more light entering the second waveguide, improving the efficiency of light coupling from the first waveguide to the second waveguide. The fourth width being greater than the first width allows more light to propagate from the first waveguide to the second waveguide, further improving the efficiency of light propagation across layers and reducing coupling loss.

[0010] Optionally, the difference between the first width and the third width is greater than or equal to twice the processing tolerance.

[0011] By setting the width as described above, the reliability of the alignment between the first end of the second waveguide and the first waveguide can be improved, and the coupling loss caused by processing tolerance can be reduced.

[0012] Optionally, the first width is less than or equal to the first threshold.

[0013] Optionally, the first waveguide further includes a third segment located between the first and second segments, wherein the width of the third segment is reduced from the first width to the second width, and the length of the third segment is greater than or equal to the second threshold.

[0014] In the above structure, the third segment is equivalent to adding a transition structure between the first and second segments. This transition structure allows the equivalent refractive index of the first waveguide to change slowly, making the transition smoother and reducing the loss during light propagation.

[0015] Optionally, the width of the end of the optical dielectric structure coupled to the second waveguide is greater than or equal to the fourth width.

[0016] Optionally, the width of the second waveguide increases from the third width to the fourth width, and the length of the second waveguide is greater than or equal to the third threshold.

[0017] Optionally, the absolute value of the difference between the thickness of the second waveguide and the thickness of the optical dielectric structure is less than or equal to 5% of the thickness of the second waveguide; or, the absolute value of the difference between the thickness of the second waveguide and the thickness of the optical dielectric structure is less than or equal to 5% of the thickness of the optical dielectric structure.

[0018] Optionally, it further includes: a third waveguide; the first waveguide further includes a fourth segment, the fourth segment is coupled to the second segment, and the fifth width of the fourth segment is greater than the second width; the third end of the third waveguide is coupled to the optical dielectric structure along the second direction, the fourth end of the third waveguide is coupled to the fourth segment along the third third direction, the third third direction is opposite to the first direction, and the sixth width of the third end is greater than the fifth width, and the seventh width of the fourth end is less than the fifth width.

[0019] Optionally, it further includes: a cladding formed between the first waveguide and the second waveguide, the thickness of which is less than or equal to a thickness threshold.

[0020] In a second aspect, a method for manufacturing a structure for light propagation is provided, comprising: forming a first waveguide having a first refractive index; forming a second waveguide having a second refractive index, and a first end of the second waveguide being coupled to the first waveguide along a first direction; forming an optical dielectric structure having a third refractive index, and a second end of the second waveguide being coupled to the optical dielectric structure along a second direction. The third refractive index is greater than the first refractive index, and the second refractive index is greater than or equal to the first refractive index and less than or equal to the third refractive index.

[0021] Optionally, forming the second waveguide includes: forming the second waveguide by deposition or etching; forming the optical dielectric structure includes: bonding the optical dielectric structure at the second end of the second waveguide.

[0022] Optionally, it further includes: forming a cladding on the first waveguide; forming a second waveguide on the cladding; wherein the thickness of the cladding between the first waveguide and the second waveguide is less than or equal to a thickness threshold.

[0023] Thirdly, a semiconductor device is provided, comprising the structure provided in the first aspect.

[0024] Fourthly, an optical device is provided, comprising the structure provided in the first aspect.

[0025] Fifthly, a lidar is provided, including a laser and a structure provided in the first aspect; the laser is configured to emit a probe light; a first waveguide of the structure is disposed in the path of the emitted probe light. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be introduced as examples below. The accompanying drawings described below are merely embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort. The accompanying drawings are used to provide a further understanding of this disclosure and constitute a part of the specification. They are used together with the embodiments of this disclosure to explain this disclosure and do not constitute a limitation of this disclosure.

[0027] Figure 1 An example diagram of a structure for light propagation is shown.

[0028] Figure 2A A cross-sectional view of another example of a structure used for light propagation is shown.

[0029] Figure 2B A top view shows an example of another structure used for light propagation.

[0030] Figure 3A A cross-sectional view is shown of an example of a structure for light propagation consistent with some embodiments of this disclosure.

[0031] Figure 3B A top view is shown of an example of a structure for light propagation consistent with some embodiments of this disclosure.

[0032] Figure 4 A top view is shown of an example of another structure for light propagation consistent with some embodiments of this disclosure.

[0033] Figure 5 A top view is shown of another example of a structure for light propagation consistent with some embodiments of this disclosure.

[0034] Figure 6 An example graph showing the relationship between optical loss and waveguide length, consistent with some embodiments of this disclosure, is shown.

[0035] Figure 7 An example diagram of a first structure for light propagation, consistent with some embodiments of this disclosure, is shown.

[0036] Figure 8 An example diagram of a second structure for light propagation, consistent with some embodiments of this disclosure, is shown.

[0037] Figure 9 An example diagram of a third structure for light propagation, consistent with some embodiments of this disclosure, is shown.

[0038] Figure 10 An example flowchart of a method for manufacturing a structure for light propagation, consistent with some embodiments of this disclosure, is shown.

[0039] Figure 11 An example diagram of an optical device consistent with some embodiments of this disclosure is shown. Detailed Implementation

[0040] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the specific implementation methods of this disclosure will be described below with reference to the accompanying drawings. The accompanying drawings described below are merely some embodiments of this disclosure. For those skilled in the art, other drawings or embodiments can be obtained based on these drawings or embodiments without creative effort. Adjustments and improvements made without departing from the concept of this disclosure are all within the protection scope of this disclosure.

[0041] To keep the drawings simple, each figure only schematically shows the parts relevant to the embodiment, and they do not represent the actual structure of the product. In addition, for the sake of simplicity and ease of understanding, only some structures or parts are schematically shown, and there may be more or fewer similar structures or parts in reality.

[0042] With the development of photonic chip technology, photonic chips are evolving from single on-chip optical platforms to heterogeneous integration. Heterogeneous integration can package different technologies or functional structures or chips together, combining the advantages of different platforms to improve chip performance and integration.

[0043] When photonic chips employ heterogeneous integration or heterogeneous integration technology, the propagation of light between optical structures of different layers may be involved. However, light often faces high loss issues when propagating between different layers.

[0044] In one solution, an etching process can be used to etch the upper material into a waveguide with a gradually varying width, thereby slowly transferring optical signals from the lower chip to the upper waveguide and reducing interlayer light propagation losses. For example, Figure 1 An example diagram of a structure for light propagation is shown. (Reference) Figure 1 In this structure 100, lithium niobate (LN) is etched into a tapered transition waveguide 120, and the transition waveguide 120 is bonded to the waveguide 140 (e.g., silicon nitride (SiN) waveguide) of the lower chip using micro-transfer technology, so as to slowly transition the optical signal in the lower chip to the upper waveguide.

[0045] While this structure can reduce light propagation loss, it presents at least one of the following problems. First, patterned structures are difficult to fabricate during bonding-type heterogeneous integration. For example, the alignment precision between transition waveguide 120 and waveguide 140 must be at least on the order of hundreds of nanometers. In this case, bonding operations are difficult, processing tolerances are small, production yields are low, and industrial production is challenging. Second, the application scenarios for this structure are limited. For example, magneto-optical materials are not suitable for etching. In applications using magneto-optical materials, it is difficult to etch and pattern them, thus preventing the use of this structure to reduce light propagation loss. Furthermore, microsystems achieve complex semiconductor structures at the micrometer or even nanometer scale; at such tiny dimensions, patterning and bonding operations of waveguide materials present significant challenges.

[0046] In another solution, a transition design can be implemented for the underlying waveguide. For example, Figure 2A and Figure 2B Cross-sectional and top views are shown respectively, representing another example of a structure used for light propagation. (Reference) Figure 2A and Figure 2B The structure 200 includes an upper waveguide 220 and a lower waveguide 240. In this structure 200, the lower waveguide 240 undergoes a transition design, giving it a transition structure 242. The width of the transition structure 242 narrows (e.g., from W21 to W22). The width W21 reduces coupling loss with the upper waveguide. The width W22 allows more light to enter the upper waveguide. This transition structure design for the lower waveguide 240 reduces the patterning requirements of the upper waveguide 220, lowers operational complexity and production costs, simplifies the fabrication process, and improves industrial production feasibility.

[0047] However, this structure 200 still suffers from significant light loss during propagation. Although widening the lower waveguide can reduce the loss to some extent, the loss remains at a relatively high level.

[0048] This disclosure provides a structure for light propagation (hereinafter referred to as a light propagation structure), which can not only reduce the operational difficulty and production cost in the manufacturing process and improve the feasibility of industrial production, but also greatly reduce the loss in the light propagation process and improve the efficiency of light propagation.

[0049] Figure 3A and Figure 3B Cross-sectional and top views are shown respectively, illustrating an example of a structure for light propagation consistent with some embodiments of this disclosure. Reference Figure 3A and Figure 3BThe structure 300 includes a waveguide 320 (which may be referred to as a first waveguide for distinction), a waveguide 340 (which may be referred to as a second waveguide for distinction), and an optical dielectric structure 360. Waveguide 320 may have a first refractive index n1. Waveguide 340 may have a second refractive index n2. Optical dielectric structure 360 ​​may have a third refractive index n3. The third refractive index n3 may be greater than the first refractive index n1. The second refractive index n2 may be greater than or equal to the first refractive index n1 and less than or equal to the third refractive index n3. A first end of waveguide 340 may be coupled to waveguide 320 along a first direction F1. A second end of waveguide 340 may be coupled to optical dielectric structure 360 ​​along a second direction F2.

[0050] In the above structure 300, the waveguide 340 acts as a connecting structure between the light propagation media (waveguide 320 and optical medium structure 360) of different layers. This connecting structure can transform the coupling in the first direction between the light propagation media of different layers into coupling in the second direction, reducing the loss of optical coupling between the light propagation media of different layers. Furthermore, the refractive index of waveguide 340 is between that of waveguide 320 and optical medium structure 360, enabling a transition in refractive index, reducing the need for patterning of optical medium structure 360, significantly improving processing tolerance and production yield, reducing processing complexity, and lowering production costs. This is particularly advantageous when the material of the optical medium structure is not suitable for patterning. It has a wider range of applications, such as heterogeneous integration of magneto-optical materials (e.g., magneto-optical crystals or magneto-optical glass) or heterogeneous integration of microsystems.

[0051] The third refractive index n3 of the optical dielectric structure 360 ​​can be greater than the first refractive index of the waveguide 320. The second refractive index n2 of the waveguide 340 can be greater than or equal to the first refractive index n1 of the waveguide 320, and less than or equal to the third refractive index n3 of the waveguide 340. These refractive index settings allow light in the waveguide 320 to tend to propagate from the waveguide 340 to the optical dielectric structure 360. In the above structure 300, during the propagation of light from the waveguide 320 with the first refractive index n1 to the optical dielectric structure 360 ​​with the third refractive index n3, the waveguide 340 can provide a smoother transition in refractive index, thereby reducing coupling loss during light propagation.

[0052] Waveguide 320 and optical dielectric structure 360 ​​are located in different layers, and the first direction F1 may include the optical coupling direction between layers. For example, waveguide 320 includes a lower waveguide, and optical dielectric structure 360 ​​includes an upper waveguide, and the first direction F1 is the optical coupling direction from the lower layer to the upper layer. Since the optical path is reversible, the first direction can also be the optical coupling direction from the upper layer to the lower layer. The second direction F2 may include the optical coupling direction within a layer (e.g., the optical coupling direction within the upper layer). In some embodiments, such as Figure 3A and Figure 3BAs shown, the first direction F1 may include a direction perpendicular to the waveguide 320 and extending toward the layer containing the optical dielectric structure 360. The second direction F2 may include a direction parallel to the layer containing the optical dielectric structure 360 ​​and extending toward the optical dielectric structure 360. The first direction F1 and the second direction F2 may be perpendicular. In some other embodiments, the first direction and the second direction may not be perpendicular, as long as light can be guided from the optical propagation medium of one layer (e.g., the lower layer) to the optical propagation medium of another layer.

[0053] In some embodiments, the waveguide 320 and the optical dielectric structure 360 ​​may be made of different materials. For example, the waveguide 320 may include silicon nitride (SiN), and the optical dielectric structure 360 ​​may include lithium niobate (LN). LN has a higher refractive index than SiN. In some embodiments, the waveguide 340 may be made of the same material as the waveguide 320 (e.g., SiN). In this case, the manufacturing process can be further simplified, and the waveguide 340 can be manufactured using a similar process as that used to manufacture the waveguide 320.

[0054] In some embodiments, waveguide 320 can be a lower waveguide, and optical dielectric structure 360 ​​can be an upper waveguide. When heterogeneous or heterogeneous integration is performed using the above structure 300, light in waveguide 320 can enter waveguide 340 with lower coupling loss. When light propagates from waveguide 340 to optical dielectric structure 360, the light can propagate within the same layer, further reducing coupling loss. Furthermore, in heterogeneous integration applications, the above structure 300 can reduce the patterning requirements of optical dielectric structure 360, significantly improve processing tolerance and production yield, reduce processing complexity, and lower production costs, making it applicable to a wide range of scenarios.

[0055] In some embodiments, the width of waveguide 340 can gradually increase from the first end 342 along the second direction F2 to the second end 344, further smoothing the propagation of light. This gradual increase can include linear or nonlinear increases. This disclosure does not limit the shape of the waveguide 340 projected along a direction parallel to the first direction F1. In some embodiments, the projected shape of waveguide 340 can include: a trapezoid, an approximate trapezoid, a partial fan shape, or other transitional shapes with axisymmetric characteristics. In some embodiments, the projected surface shape of waveguide 340 can include a non-axisymmetric transitional shape with inconsistent changes on both sides (e.g., one side increases linearly or nonlinearly, while the other side remains unchanged or has a different trend of change). In other embodiments, the width of waveguide 340 can not gradually increase from the first end 342 along the second direction F2 to the second end 344, but has an overall increasing trend. In summary, this disclosure does not limit the shape of the projected surface of waveguide 340, as long as the shape of the projected surface allows the width of waveguide 340 to have an overall increasing trend from the first end 342 along the second direction F2 to the second end 344.

[0056] In some embodiments, the first waveguide can be designed to further improve the efficiency of light propagation. For example, Figure 4 A top view is shown as an example of another structure for light propagation consistent with some embodiments of this disclosure. Reference Figure 4 The structure 400 includes waveguide 420, waveguide 440, and optical dielectric structure 460. Waveguide 440 and optical dielectric structure 460 can be similar to waveguide 340 and optical dielectric structure 360 ​​in the embodiment shown in FIG3, and will not be described again here. In some embodiments, waveguide 420 includes segment 422 (which may be referred to as the first segment for distinction) and segment 424 (which may be referred to as the second segment for distinction), and segment 422 can be coupled to segment 424. The width W41 of segment 422 (which may be referred to as the first width for distinction) is greater than the width W43 of segment 424 (which may be referred to as the second width for distinction). Waveguide 440 can be coupled to segment 422, wherein the width W42 of the first end 442 (which may be referred to as the third width for distinction) is less than the width W41, and the width W44 of the second end 444 (which may be referred to as the fourth width for distinction) is greater than the width W41.

[0057] refer to Figure 4 For example, in waveguide 420, the width W41 of segment 422 is greater than the width W43 of segment 424, allowing the overall structure of waveguide 420 to first broaden to width W41, providing a wider waveguide for light. This structure allows light to diverge more, enabling light to enter the second waveguide from the first waveguide and reducing coupling loss with waveguide 440. The width of the first waveguide narrows to width W43 in the second segment, reducing the equivalent refractive index in waveguide 420, which can promote more light entering waveguide 440 and improve the efficiency of light coupling from the first waveguide to the second waveguide. Width W44 is greater than width W41, allowing more light to propagate from waveguide 420 to waveguide 440, further improving the efficiency of light propagation across layers and reducing coupling loss.

[0058] This disclosure does not limit the width W41 of segment 422, and different widths can be set according to different application scenarios. For example, it can be determined based on the size of a preset optical field. This disclosure also does not limit the width W43 of segment 424, and the width W43 can be determined based on the purpose of the light to be propagated in the waveguide 420 in the application. If it is desired that more light propagates into the optical medium structure 460, a smaller width W43 can be set. If it is desired that a portion of the light is retained at the emitting end of the waveguide 420, a larger width W43 can be set. In some embodiments, the width W43 can be smaller than the width W41. The width W42 can be greater than, less than, or equal to the width W43.

[0059] In some embodiments, the width of waveguide 440 gradually widens from the width W42 of the first end 442 along the second direction F2 to the width W44 of the second end, which can gradually increase the equivalent refractive index of waveguide 440 and further reduce the loss of light during propagation.

[0060] In some embodiments, the difference between width W41 and width W42 is greater than or equal to twice the manufacturing tolerance. Manufacturing tolerance refers to the allowable deviation or error during the manufacturing process. By setting the widths as described above, the reliability of the alignment between the first end 442 of waveguide 440 and waveguide 420 can be improved, and coupling loss due to manufacturing tolerance can be reduced. Figure 4 Taking the illustrated embodiment as an example, for instance, during processes such as deposition or etching, if the first end 442 of waveguide 440 has a processing tolerance and deviates to one side, ensuring that the difference between width W41 and width W42 is greater than or equal to twice the processing tolerance can prevent the first end 442 of waveguide 440 from deviating from the range of waveguide 420. This achieves alignment between the first end 442 of waveguide 440 and waveguide 420, reducing losses that may be caused by process errors during light propagation.

[0061] In some embodiments, the width W41 is less than or equal to a first threshold. This disclosure does not limit the size of the first threshold, and it can have different values ​​in different application scenarios. In some embodiments, the first threshold can be determined based on the propagation mode of light. For example, when waveguide 420 is used for single-mode propagation of light, the first threshold is determined based on the single-mode width. The single-mode width in this disclosure includes the diameter at which the light intensity decreases to 1 / e² of the center light intensity during propagation. For example, the width W41 can be less than or equal to the single-mode width. This not only allows more light to propagate into waveguide 440, resulting in higher modulation efficiency, but also limits the generation of multimodes. Furthermore, when waveguide 420 is used for multimode propagation of light, the first threshold can be determined based on the maximum width of the multimode propagation. For example, the width W41 can be less than or equal to the maximum width. The maximum width can be determined based on one or more of the number of modes, propagation rate, propagation bandwidth, or propagation distance.

[0062] In some embodiments, a transition segment can be provided between the first segment and the second segment of the first waveguide to further improve the efficiency of light propagation. For example, Figure 5 A top view is shown of another example of a structure for light propagation consistent with some embodiments of this disclosure. Reference Figure 5The structure 500 includes waveguide 520, waveguide 540, and optical dielectric structure 560. Waveguide 520 and optical dielectric structure 560 can be similar to waveguide 320 and optical dielectric structure 360 ​​in the embodiment shown in FIG3, and will not be described again here. In some embodiments, waveguide 520 includes segments 522, 524, and 526 (for distinction, they can be referred to as a third segment). Segments 522 and 524 can be similar to... Figure 4 Segments 422 and 424 of the illustrated embodiment will not be described again here. Segment 526 is located between segments 522 and 524. The width of segment 526 can be reduced from width W51 to width W53.

[0063] refer to Figure 5 For example, segment 526 is equivalent to adding a transition structure between segment 522 and segment 524. This transition structure allows the equivalent refractive index of waveguide 520 to change slowly, resulting in a smoother transition and reducing light loss during propagation. This disclosure does not limit the shape of the projection of segment 526 along the direction parallel to the first direction F1. In some embodiments, the projected shape of segment 526 may include: a trapezoid, an approximate trapezoid, a partial sector, or other transition shapes with axisymmetric characteristics. Furthermore, the projected shape of segment 526 may include a non-axisymmetric transition shape with inconsistent changes on both sides.

[0064] In some embodiments, the length L1 of segment 526 is greater than or equal to a second threshold. The second threshold can be set based on the loss requirements of the optical field. For example, the second threshold ensures that the loss of the optical field after passing through segment 526 is less than or equal to one percent. When the widths W51 and W53 are constant, the longer the length of segment 526, the slower the change in the equivalent refractive index of waveguide 520, and the smaller the optical loss. Thus, by setting the length of segment 526, the loss during light propagation can be further reduced. For example, the second threshold can be determined based on the wavelength of light and the relationship between the propagation loss of light at that wavelength in segment 526 and the length of segment 526, thereby determining a second threshold that meets the preset loss requirements. Setting the length L1 of segment 526 to be greater than or equal to the second threshold reduces the propagation loss of light in waveguide 520 and improves the propagation efficiency of light.

[0065] This disclosure does not limit the width of the optical medium structure (e.g., the widths W36, W46, W56 described in conjunction with Figures 3-5). In applications, the width of the optical medium structure can be determined based on the application scenario. For example, when applied in a laser, the laser's output structure may include optical medium structures 360, 460, 560, and the width of the optical medium structures 360, 460, 560 can be determined based on the size of a preset laser spot. In some embodiments, the widths W36, W46, W56 of one end of the optical medium structures 360, 460, 560 coupled to the waveguides 340, 440, 540 can be greater than or equal to the widths W34, W44, W54 of the second ends 344, 444, 544 of the waveguides 340, 440, 540. This facilitates the coupling of waveguides 340, 440, and 540 with optical dielectric structures 360, 460, and 560, reducing light loss during propagation from waveguides 340, 440, and 540 to optical dielectric structures 360, 460, and 560, thereby improving light utilization efficiency.

[0066] In some embodiments, the widths of waveguides 340, 440, and 540 are increased from widths W32, W42, and W52 to widths W34, W44, and W54. Increasing the widths of waveguides 340, 440, and 540 allows for a gradual increase in the equivalent refractive index of waveguides 340, 440, and 540, which can reduce coupling loss of light between waveguides 320, 420, 520 and waveguides 340, 440, and 540.

[0067] In some embodiments, the length L2 of waveguides 340, 440, and 540 is greater than or equal to a third threshold. The third threshold can be set based on the optical field loss requirements. For example, the third threshold ensures that the optical field loss after passing through waveguides 340, 440, and 540 is less than or equal to one percent. When the widths W52 and W54 are constant, the longer the length L2 of waveguides 340, 440, and 540, the slower the change in the equivalent refractive index of waveguide 540, and the smaller the optical loss. Thus, by setting the lengths of waveguides 340, 440, and 540, the loss during light propagation can be further reduced. For example, the third threshold can be determined based on the wavelength of light and the relationship between the propagation loss of light at that wavelength in waveguides 340, 440, and 540 and the length L2 of waveguides 340, 440, and 540, thereby determining a third threshold that meets the preset loss requirements. The length L2 of waveguides 340, 440, and 540 is set to be greater than or equal to the third threshold to reduce the propagation loss of light in waveguides 340, 440, and 540 and improve the propagation efficiency of light.

[0068] During the propagation of light, light loss can vary with the propagation length. Figure 6An example graph illustrating the relationship between optical loss and waveguide length, consistent with some embodiments of this disclosure, is shown. (Reference) Figure 6 The horizontal axis represents the waveguide length L2 at 340, 440, and 540 mm, in micrometers (µm), and the vertical axis represents the transmission loss in decibels (dB). Taking O-band light as an example... Figure 6 As shown, the propagation loss gradually decreases with the increase of the waveguide length L2 (340, 440, 540). When the length L2 is around 100 micrometers, the light propagation efficiency can reach over 99%, and the loss is less than 0.04 dB.

[0069] In some embodiments, the absolute value of the difference between the thickness of waveguides 340, 440, 540 and the thickness of optical dielectric structures 360, 460, 560 may be less than or equal to 5% of the thickness of waveguides 340, 440, 540. Alternatively, the absolute value of the difference between the thickness of waveguides 340, 440, 540 and the thickness of optical dielectric structures 360, 460, 560 may be less than or equal to 5% of the thickness of optical dielectric structures 360, 460, 560.

[0070] During light propagation, scattering and loss may occur when light passes through structures with different cross-sectional thicknesses. The thicknesses of waveguides 340, 440, and 540 are set to be as equal as possible to the thicknesses of optical dielectric structures 360, 460, and 560. For example, the absolute value of the thickness difference is less than or equal to 5% of the thickness of waveguides 340, 440, and 540 or optical dielectric structures 360, 460, and 560, to reduce coupling loss between them, further reducing light propagation losses and improving propagation efficiency. Furthermore, waveguides 340, 440, and 540 and optical dielectric structures 360, 460, and 560 may be heterogeneous or heterogeneous structures, and can be manufactured independently during processing. For example, waveguides 340, 440, and 540 can be formed together with waveguides 320, 420, and 520 through deposition or etching processes. After the optical dielectric structures 360, 460, and 560 are independently manufactured, they are bonded together with the waveguides 340, 440, and 540 using a bonding process. By controlling the thickness of the waveguides 340, 440, and 540 and the optical dielectric structures 360, 460, and 560, the coupling loss between them can be reduced after bonding.

[0071] The design of any of the structures in the above embodiments can be extended to multiple sets of structures, allowing light to propagate in more layers, or allowing light to be converted during propagation between two layers. For example, Figures 7 to 9 Several example diagrams of structures for light propagation consistent with some embodiments of this disclosure are shown. Reference Figures 7 to 9The structures 700, 800, and 900 include waveguides 720, 820, 920, 740, 840, and 940, optical dielectric structures 760, 860, and 960, and waveguides 780, 880, and 980 (which may be referred to as third waveguides for distinction). The descriptions of waveguides 740, 840, and 940 and optical dielectric structures 760, 860, and 960 are similar to those in the above embodiments and will not be repeated here.

[0072] In some embodiments, reference Figure 7 Waveguide 720 can use similar technologies as described above. Figure 3B The structure is shown. One end 784 of waveguide 780 (which can be referred to as the third end for distinction) is coupled to the optical dielectric structure 760 along the second direction F2. The other end 782 of waveguide 780 (which can be referred to as the fourth end for distinction) is coupled to waveguide 720 along the third direction F3. The third direction F3 can be opposite to the first direction F1. Figure 7 The direction shown is perpendicular to the paper and incident on the paper. This allows light to propagate alternately between different layers. Alternatively, the third direction F3 can be the same as the first direction F1. For example... Figure 7 The direction shown is perpendicular to the paper and extends outwards from the paper. This allows light to propagate between multiple layers.

[0073] The design of the dimensions (e.g., width, length, etc.) of waveguide 780 is similar to that of waveguide 340, but may be the same or different. For example, the width of the fourth end 782 is smaller than the width of the third end 784. The width of waveguide 780 may gradually decrease linearly or nonlinearly along the second direction F2. The width of the end of the optical dielectric structure 760 coupled to waveguide 780 is greater than or equal to the width of the third end 784. The difference between the width of waveguide 720 and the width of the fourth end 782 is greater than or equal to twice the fabrication tolerance.

[0074] In some embodiments, reference Figure 8 Waveguide 820 can use similar techniques as described above. Figure 4 The structure is shown. Waveguide 820 includes segments 822, 824, and 821 (which may be referred to as the fourth segment for distinction). Segment 821 is similar to segment 822, which is similar to segment 422 in the above embodiment. Segment 821 is coupled to segment 824. The width of segment 821 (which may be referred to as the fifth width for distinction) is greater than the width of segment 824. The width of segment 821 may be the same as or different from the width of segment 822.

[0075] One end 884 of waveguide 880 (which can be referred to as the third end for clarity) is coupled to the optical dielectric structure 860 along the second direction F2, and the other end 882 (which can be referred to as the fourth end for clarity) is coupled to segment 821 along the third direction F3. The third direction F3 is similar to the above. Figure 7 The illustrated embodiment is described below. The design of the dimensions (e.g., width, length, etc.) of waveguide 880 is similar to that of waveguide 440, but may be the same or different. For example, the width of the third end 884 (which may be referred to as the sixth width for distinction) is greater than the width of segment 821, and the width of the fourth end 882 (which may be referred to as the seventh width for distinction) is less than the width of segment 821. The difference between the width of segment 821 and the width of the fourth end 882 is greater than or equal to twice the manufacturing tolerance. The width of waveguide 880 may gradually decrease linearly or nonlinearly along the second direction F2. The width of the end of the optical dielectric structure 860 coupled to waveguide 880 is greater than or equal to the width of the third end 884.

[0076] In some embodiments, reference Figure 9 Waveguide 920 can use similar techniques as described above. Figure 5 The structure shown includes segments 922, 924, 926, 921 (which may be referred to as the fourth segment for distinction), and 923 (which may be referred to as the fifth segment for distinction). Segment 923 is located between segments 921 and 924. Segment 923 is similar to segment 926. The design of the dimensions (e.g., width, length, etc.) of segment 923 is similar to that of segment 926, but may be the same or different. Segment 926 is similar to segment 526 in the above embodiment. For example, the width of the coupling side of segment 923 with segment 924 is smaller than the width of the coupling side of segment 923 with segment 921. The width of segment 923 may increase linearly or non-linearly.

[0077] The design of the dimensions (e.g., width, length, etc.) of waveguide 980 is similar to that of waveguide 540, but may be the same or different. The coupling of waveguide 980 with optical dielectric structure 960 and segment 921 is similar to the coupling of waveguide 880 with optical dielectric structure 860 and segment 821.

[0078] exist Figures 7 to 9 In the illustrated structure, light can propagate from waveguides 720, 820, and 920 to waveguides 740, 840, and 940, and then via waveguides 740, 840, and 940 to optical dielectric structures 760, 860, and 960. Then, light can propagate through optical dielectric structures 760, 860, and 960 to waveguides 780, 880, and 980, and then to waveguides 720, 820, and 920. In other embodiments, light can propagate through optical dielectric structures 760, 860, and 960 to waveguides 780, 880, and 980, and then to waveguides or optical dielectric structures in other layers.

[0079] In some embodiments, the above structural design can be repeated to achieve low-loss continuous multi-layer propagation of light.

[0080] This disclosure does not limit the shape of the optical medium structure. Regular cross-sectional shapes (e.g., rectangular cross-sectional shapes) are more advantageous in reducing the patterning requirements of the optical medium structure. In other embodiments, the cross-sectional shape of the optical medium structure may also include trapezoids, multiple rectangles of different widths, a combination of rectangles and trapezoids, or other regular or irregular shapes.

[0081] Continue to refer to Figure 3A In some embodiments, structure 300 may further include a cladding 310 formed between waveguide 320 and waveguide 340. Forming the cladding on waveguide 320 allows for planarization of the surface of waveguide 320, which is then used to subsequently form waveguide 340 and integrated optical dielectric structure 360. The planarized surface reduces light scattering, thereby reducing light propagation loss.

[0082] In some embodiments, the thickness of the cladding may be less than or equal to a thickness threshold. This disclosure does not limit the size of the thickness threshold, as long as the thickness of the cladding is sufficient to make the interface between waveguide 320 and waveguide 340 sufficiently flat and does not affect the coupling efficiency between waveguide 320 and waveguide 340, allowing at least a portion of the optical field in waveguide 320 to couple into waveguide 340. For example, the expected portion may be expressed as a percentage. For example, the expected portion may be between 10% and 50%, or higher than 50%. For example, the expected portion includes 50%, 30%, 25%, 15%, or 10%, etc. In some embodiments, the thickness threshold may be designed based on the cladding material, or the effect of thickness on light propagation loss, etc. For example, the thickness threshold may be within 1 micrometer, such as 1 micrometer, or at the level of hundreds of nanometers.

[0083] This disclosure does not limit the cladding material, which may include, for example, silicon dioxide (SiO2).

[0084] This disclosure also provides a method for manufacturing a structure for light propagation. For example, Figure 10 An example flowchart of a method for manufacturing a structure for light propagation, consistent with some embodiments of this disclosure, is shown. (Reference) Figure 10 The method includes at least the following steps.

[0085] In step 101, a first waveguide is formed, and the first waveguide has a first refractive index.

[0086] In step 103, a second waveguide is formed, the second waveguide has a second refractive index, and the first end of the second waveguide is coupled to the first waveguide along a first direction.

[0087] In step 105, an optical medium structure is formed. The optical medium structure has a third refractive index, and the second end of the second waveguide is coupled to the optical medium structure along a second direction. The third refractive index is greater than the first refractive index, and the second refractive index is greater than or equal to the first refractive index and less than or equal to the third refractive index.

[0088] The above method utilizes a second waveguide to connect the light propagation between the first waveguide and the optical medium structure. This connection transforms the coupling in the first direction between different layers of the light propagation medium into coupling in the second direction, reducing the loss of light coupling between different layers of the light propagation medium. Furthermore, the refractive index of waveguide 340 is between that of waveguide 320 and the refractive index of the optical medium structure 360, enabling a refractive index transition, reducing the patterning requirements of the optical medium structure 360, significantly improving processing tolerance and production yield, reducing processing complexity, and lowering production costs. This is particularly advantageous when the material of the optical medium structure is not suitable for patterning. It has broader applicability in scenarios such as heterogeneous integration of magneto-optical materials (e.g., magneto-optical crystals or magneto-optical glass) or heterogeneous integration of microsystems.

[0089] In some embodiments, step 103, forming the second waveguide, may include forming the second waveguide by deposition or etching. Step 105, forming the optical dielectric structure, may include bonding the optical dielectric structure to the second end of the second waveguide. This enables heterogeneous integration, integrating independently fabricated optical dielectric structures with the first or second waveguide.

[0090] In some embodiments, the above method may further include: forming a cladding on a first waveguide; forming a second waveguide on the cladding. Similar to the description in the above embodiments, the thickness of the cladding between the first and second waveguides is less than or equal to a thickness threshold.

[0091] This disclosure also provides a semiconductor device, which may include a photonic chip and any of the structures for light propagation provided in the above embodiments.

[0092] This disclosure also provides an optical device. For example, Figure 11 An example diagram of an optical device consistent with some embodiments of this disclosure is shown. Reference Figure 11The optical device 110 may include optical components and any of the light propagation structures provided in the above embodiments, referred to as the light propagation structure 120. In some embodiments, the optical components may include a light emitter 111 for emitting light. The light emitted by the light emitter 111 can propagate through the light propagation structure 120 to other optical components or exit to the outside. For example, the light emitted by the light emitter 111 exits to the outside of the optical device after passing through the light propagation structure 120. Another example is that the light emitted by the light emitter 111 propagates through the light propagation structure 120 to a photodetector. The photodetector can detect the received light and convert it into an electrical signal. In some embodiments, the optical components may include a photodetector for detecting light. The light propagation structure 120 can propagate light to the photodetector. In some embodiments, the optical device 110 may include a light emitter, a light propagation structure, and a photodetector.

[0093] For example, the optical device includes a non-reciprocal optical isolator. When implementing a non-reciprocal optical isolator using magneto-optical materials, the structure provided in any of the above embodiments allows for heterogeneous and heterogeneous integration of magneto-optical materials within a chip, combining the advantages of on-chip platforms and magneto-optical materials to achieve isolator integration.

[0094] For example, silicon nitride (SiN) possesses excellent properties such as ultra-low loss, strong chemical stability, and a large light transmission window. Lithium niobate (LN) has good electro-optic properties, making it suitable for designing optical devices such as high-speed electro-optic modulators. Using the structures provided in any of the above embodiments, SiN and LN can be heterogeneously integrated within a chip. This allows for the utilization of the advantages of both materials, thereby improving the performance of optical devices such as high-speed electro-optic modulators.

[0095] In the above optical devices, the light emitting device can be used to emit laser light, or the photodetector can be used to detect laser light. In this case, the optical device can be used in optical detection devices such as lidar.

[0096] This disclosure also provides a lidar, including any of the structures for light propagation provided in the above embodiments. This structure can be disposed on at least one of the laser emission path or the laser receiving path to improve the propagation efficiency of the laser within the lidar.

[0097] In this disclosure, unless otherwise expressly specified and limited, ordinal numbers, such as "first," "second," etc., are used only to distinguish and describe related objects, and should not be construed as indicating or implying the relative importance or order between related objects. Furthermore, ordinal numbers do not represent the quantity of related objects. For example, "first lidar" may include one lidar or multiple lidars.

[0098] "Multiple" includes two or more, and other classifiers are similar.

[0099] The terms "or" and "and / or" in this disclosure are used to describe relationships between related objects, indicating a non-exclusive inclusion. For example, "A and / or B" and "A or B" can both include: "A alone," "B alone," or "A and B," where "A" and "B" can include a single object or multiple objects. Similarly, "A, B and / or C," "A, B or C," and "A, B and C" can both include: "A alone," "B alone," "C alone," "A and B," "A and C," "B and C," or "A, B and C," where "A," "B," and "C" can include a single object or multiple objects. Additionally, the " / " in this disclosure is used to indicate an "or" relationship between related objects. The meanings of "at least one of A or B" and "one or more of A and B" in this disclosure are the same as the meaning of "A or B" above. The meanings of "one or more of A, B, and C" and "at least one of A, B, or C" are the same as the meaning of "A, B, or C" above. The meaning of "one or more of A, B, and C" is the same as the meaning of "A, B, or C" above.

[0100] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not described in detail or in a particular embodiment can be referred to in the relevant descriptions of other embodiments. Furthermore, the above embodiments can be freely combined as needed.

Claims

1. A structure for light propagation, characterized in that, include: The first waveguide has a first refractive index; The second waveguide has a second refractive index, and the first end of the second waveguide is coupled to the first waveguide along a first direction; An optical dielectric structure having a third refractive index, wherein the second end of the second waveguide is coupled to the optical dielectric structure along a second direction; The third refractive index is greater than the first refractive index; the second refractive index is greater than or equal to the first refractive index and less than or equal to the third refractive index.

2. The structure according to claim 1, characterized in that, The first waveguide and the optical dielectric structure are made of different materials.

3. The structure according to claim 1 or 2, characterized in that, The first waveguide includes a first segment and a second segment, the first segment is coupled to the second segment, and the first width of the first segment is greater than the second width of the second segment; The second waveguide is coupled to the first segment, the third width of the first end is smaller than the first width, and the fourth width of the second end is larger than the first width.

4. The structure according to claim 3, characterized in that, The difference between the first width and the third width is greater than or equal to twice the processing tolerance.

5. The structure according to claim 3 or 4, characterized in that, The first width is less than or equal to the first threshold.

6. The structure according to any one of claims 3-5, characterized in that, The first waveguide further includes a third segment located between the first segment and the second segment, wherein the width of the third segment is reduced from the first width to the second width, and the length of the third segment is greater than or equal to a second threshold.

7. The structure according to claim 6, characterized in that, The width of the end of the optical dielectric structure coupled to the second waveguide is greater than or equal to the fourth width.

8. The structure according to any one of claims 3-7, characterized in that, The width of the second waveguide increases from the third width to the fourth width, and the length of the second waveguide is greater than or equal to the third threshold.

9. The structure according to any one of claims 1-8, characterized in that, The absolute value of the difference between the thickness of the second waveguide and the thickness of the optical dielectric structure is less than or equal to 5% of the thickness of the second waveguide; or, The absolute value of the difference between the thickness of the second waveguide and the thickness of the optical dielectric structure is less than or equal to 5% of the thickness of the optical dielectric structure.

10. The structure according to any one of claims 3-9, characterized in that, Also includes: Third waveguide; The first waveguide further includes a fourth segment, which is coupled to the second segment, and the fifth width of the fourth segment is greater than the second width; The third end of the third waveguide is coupled to the optical dielectric structure along the second direction, and the fourth end of the third waveguide is coupled to the fourth segment along a third direction. The third direction is the same as or opposite to the first direction, and the sixth width of the third end is greater than the fifth width, and the seventh width of the fourth end is less than the fifth width.

11. The structure according to any one of claims 1-10, characterized in that, Also includes: A cladding layer is formed between the first waveguide and the second waveguide, and the thickness of the cladding layer is less than or equal to a thickness threshold.

12. A method for manufacturing a structure for light propagation, characterized in that, include: A first waveguide is formed, and the first waveguide has a first refractive index; A second waveguide is formed, the second waveguide has a second refractive index, and the first end of the second waveguide is coupled to the first waveguide along a first direction; An optical medium structure is formed, the optical medium structure having a third refractive index, and the second end of the second waveguide is coupled to the optical medium structure along a second direction, wherein the third refractive index is greater than the first refractive index, and the second refractive index is greater than or equal to the first refractive index and less than or equal to the third refractive index.

13. The method according to claim 12, characterized in that, The formation of the second waveguide includes: forming the second waveguide by deposition or etching; The formation of the optical medium structure includes: bonding the optical medium structure at the second end of the second waveguide.

14. The method according to claim 12 or 13, characterized in that, Also includes: A cladding is formed on the first waveguide; The second waveguide is formed on the cladding; Wherein, the thickness of the cladding between the first waveguide and the second waveguide is less than or equal to a thickness threshold.

15. A semiconductor device, characterized in that, Includes the structure for light propagation as described in any one of claims 1-10.

16. An optical device, characterized in that, include: The structure for light propagation according to any one of claims 1-10 is configured to propagate light; Optical devices are configured to emit or receive the light.

17. A lidar, characterized in that, Includes the optical device as described in claim 16.

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