Grating coupler

Abstract

The invention relates to the technical field of gratings, in particular to a grating coupler. The grating coupler includes: a substrate; the grating layer is located on one side of the substrate, the grating layer comprises a waveguide part and a grating part, the grating part comprises a first end and a second end which are oppositely arranged in the extension direction of the grating layer, the first end is used for being connected with the waveguide part, the grating part comprises a first grating part, and in the direction from the first end to the second end, the duty ratio of the first grating part is decreased, and the period of the first grating part is increased; the optical fiber is located on the side, away from the substrate, of the grating part, and the orthographic projection of the optical fiber on the substrate and the orthographic projection of the first grating part on the substrate have an overlapped part. The duty ratio of the first grating part is set to be reduced, so that the diffraction field of the first grating part can be gently adjusted in the first grating part, and the diffraction field of the first grating part is enabled to be better matched with the mode field of the optical fiber. The period of the first grating part is set to be increased, so that the grating still basically meets the phase matching condition under the condition that the duty ratio is reduced and changed.

Description

Technical Field

[0001] The present disclosure relates to the field of grating technology, and in particular to a grating coupler. Background Art

[0002] Optoelectronic chips achieve the input of off-chip light sources or the output of on-chip optical signals by coupling with optical fibers. Grating couplers are commonly used devices for coupling optoelectronic chips and optical fibers.

[0003] With the continuous development of integrated circuits, traditional electronic integrated circuits are gradually approaching their limits in terms of bandwidth and energy consumption, and photonic chips have been vigorously developed. Photonic chips use light waves (electromagnetic waves) as the carrier of information transmission or data calculation, and grating couplers are key components that determine the light energy utilization rate and detection rate of photonic chips. Therefore, how to improve the efficiency of grating couplers is an urgent problem to be solved. Summary of the invention

[0004] Based on this, it is necessary to provide a grating coupler to address the problem of low efficiency of the grating coupler in the prior art.

[0005] In order to achieve the above object, on the one hand, a grating coupler is provided, comprising:

[0006] substrate;

[0007] a grating layer, located at one side of the substrate, the grating layer comprising a waveguide portion and a grating portion, the grating portion comprising a first end and a second end arranged opposite to each other in an extending direction of the grating layer, the first end being used to connect the waveguide portion, and the grating portion comprising a first grating portion, in a direction from the first end to the second end, a duty cycle of the first grating portion decreases and a period increases;

[0008] The optical fiber is located at a side of the grating portion away from the substrate, and an orthographic projection of the optical fiber on the substrate overlaps with an orthographic projection of the first grating portion on the substrate.

[0009] In one of the embodiments, in a direction from the first end to the second end, the duty cycle of the first grating portion decreases linearly.

[0010] In one embodiment, the grating portion includes a second grating portion, the second grating portion is located on a side of the first grating portion close to the first end, and the second grating portion is surrounded to form a plurality of rectangular grooves.

[0011] In one embodiment, the second grating portion is surrounded to form a plurality of rows of rectangular grooves arranged along a first direction, each row having a plurality of rectangular grooves spaced apart along a second direction, the second direction intersects with the first direction, and the first direction includes an extension direction of the grating layer.

[0012] In one embodiment, in the same column of rectangular grooves, the lengths of the plurality of rectangular grooves in the second direction are consistent, and / or the spacings between adjacent rectangular grooves in the second direction are consistent.

[0013] In one embodiment, in different columns of rectangular grooves, in the direction from the first end to the second end, the length of the rectangular groove in the second direction increases.

[0014] In one of the embodiments, the substrate includes a support layer and an insulating layer, the grating portion is located on a side of the insulating layer away from the support layer, and the thickness of the insulating layer is not less than 1.8 μm.

[0015] In one embodiment, the waveguide portion comprises:

[0016] A tapered waveguide is connected to the first end of the grating portion, and a width of the tapered waveguide increases in a direction from the first end to the second end.

[0017] In one embodiment, the width of the tapered waveguide on a side close to the first end is consistent with the width of the first end of the grating portion.

[0018] In one embodiment, the grating coupler comprises:

[0019] A straight waveguide is located at a side of the tapered waveguide away from the grating portion, wherein the straight waveguide comprises a ridge waveguide.

[0020] The grating coupler of the present specification has the following beneficial effects: by setting the duty cycle of the first grating portion of the grating coupler to be reduced, the diffraction field of the first grating portion can be smoothly adjusted in the first grating portion, so that the diffraction field of the first grating portion is more matched with the mode field of the optical fiber. At the same time, the period of the first grating portion is increased, so that when the duty cycle is reduced, the grating diffraction field still basically meets the phase matching condition, thereby increasing the coupling efficiency of the grating coupler. Moreover, in some embodiments, the second grating portion of the grating coupler is surrounded to form a plurality of rectangular grooves, so that the equivalent refractive index of the second grating portion can be adjusted by the position and shape of the rectangular grooves, so that when the light beam of the waveguide portion is transmitted to the first grating portion through the second grating portion, its transmittance is close to 1, thereby reducing the loss of the light beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 is a schematic diagram of a substrate provided in an embodiment;

[0023] Figure 2 is a schematic diagram of a straight waveguide provided in an embodiment;

[0024] Figure 3 A schematic diagram of a tapered waveguide provided in an embodiment;

[0025] Figure 4 is a schematic diagram of a grating portion provided in an embodiment;

[0026] Figure 5 A schematic diagram of a grating coupler test provided in an embodiment;

[0027] Figure 6 A schematic diagram of a grating coupler test provided in another embodiment.

[0028] Explanation of the reference numerals: grating coupler-100; substrate-110; silicon support substrate-111; insulator-112; silicon carbide film-113; straight waveguide-120; tapered waveguide-121; grating portion-130; first end-131; second end-132; first grating portion-133; second grating portion-134; rectangular groove-1341.

[0029] In order to better describe and illustrate the embodiments and / or examples of the inventions disclosed herein, reference may be made to one or more drawings. The additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed inventions, the embodiments and / or examples currently described, and the best modes of these inventions currently understood. DETAILED DESCRIPTION

[0030] In order to facilitate understanding of the present disclosure, the present disclosure will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present disclosure are shown in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thorough and comprehensive.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs. The terms used herein in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure.

[0032] In each embodiment, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in each embodiment can be understood according to the specific situation.

[0033] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish an element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teaching of the present embodiment, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part.

[0034] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientations shown in the figures, spatially relative terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, an element or feature described as "under other elements" or "under it" or "under it" will be oriented as being "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0035] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that when the terms "consisting of" and / or "comprising" are used in this specification, the presence of the features, integers, steps, operations, elements and / or parts can be determined, but the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups is not excluded. At the same time, when used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0036] Embodiments of the present specification are described herein with reference to cross-sectional views that are schematic representations of ideal embodiments (and intermediate structures) of the present specification, such that variations in the shapes shown due to, for example, manufacturing techniques and / or tolerances are anticipated. Thus, embodiments of the present specification should not be limited to the specific shapes of the regions shown herein, but include deviations in shapes due to, for example, manufacturing techniques. The regions shown in the figures are schematic in nature, their shapes do not represent the actual shapes of the regions of the device, and do not limit the scope of the embodiments of the present specification.

[0037] As mentioned in the background technology, how to improve the efficiency of the grating coupler is a problem that urgently needs to be solved. In traditional technology, the efficiency of the grating coupler is often improved by adding a back reflector to the back of the grating or designing a double-layer grating. In one possible example, after adding a back reflector to the back of the grating, the back reflector can reflect the light diffracted downward by the grating, thereby increasing the efficiency of the grating's upward diffraction. In another possible example, the double-layer grating can make the light diffracted downward satisfy coherent destructiveness and the light diffracted upward satisfy coherent constructiveness, thereby improving the efficiency of the grating's upward diffraction. However, whether adding a back reflector to the back of the grating or designing a double-layer grating, the preparation cost and difficulty of the grating coupler are increased, which is not conducive to the market application of the grating coupler.

[0038] Based on this, see Figures 1 to 4 In one embodiment, a grating coupler 100 is provided. The grating coupler 100 includes a substrate 110, a grating layer 130, and an optical fiber.

[0039] The substrate 110 is used to carry the grating layer 130 and the optical fiber. The substrate 110 may include a silicon support substrate 111, an insulator 112, and a silicon carbide (SiC) film 113 arranged in sequence, the insulator 112 is located on one side of the silicon support substrate 111, and the silicon carbide film 113 is located on the side of the insulator 112 away from the silicon support substrate 111. As an example, the refractive index of the insulator 112 is less than the refractive index of the silicon carbide film 113. For example, the material of the insulator 112 may include silicon dioxide, etc., which can enable the light field to be bound and transmitted in the silicon carbide film 113. Moreover, the thickness of the insulating layer set in this embodiment can be in the range of 2.8μm-3.2μm, or in the range of 1.8μm-2.2μm. Since the grating layer 130 will have a light field diffracted downward, the light field diffracted downward will be reflected at the interface between the insulator 112 and the silicon support substrate 111, and the reflected light will interfere with the light field diffracted on the grating layer 130. Therefore, in this embodiment, the refractive index of the insulator 112 is set to be smaller than the refractive index of the silicon carbide film 113, and the thickness of the insulating layer is in the range of 2.8μm-3.2μm, or in the range of 1.8μm-2.2μm, which increases the light field diffracted on the grating layer 130. Further, this makes it unnecessary to set a back reflector in this embodiment, thereby reducing the preparation cost of the grating coupler 100.

[0040] In addition, when preparing the silicon carbide film 113, it can be obtained by directly bonding a silicon carbide wafer to a silicon dioxide layer. Specifically, the silicon carbide film on the silicon dioxide layer can be obtained by using a smart stripping technique.

[0041] The grating layer 130 is located on one side of the substrate 110. Specifically, the grating layer 130 may be located on a side of the silicon carbide film 113 away from the silicon support substrate 111. The grating layer 130 may include a waveguide portion and a grating portion. The grating portion may include a first end 131 and a second end 132 that are relatively arranged in the extension direction of the grating layer 130, and the first end 131 is used to connect the waveguide portion. The grating portion may also include a first grating portion 133, and in the direction from the first end 131 to the second end 132, the duty cycle of the first grating portion 133 decreases and the period increases. As an example, in the direction from the first end 131 to the second end 132, the duty cycle of the first grating portion 133 may decrease linearly and the period may increase linearly.

[0042] In one possible example, during the preparation of the grating layer 130, the grating coupler pattern can be formed into a photoresist using electron beam lithography or deep ultraviolet lithography technology as an anti-etching mask. For example, the minimum size of the grating coupler in the present embodiment can be 150nm, which can be easily obtained using electron beam lithography or deep ultraviolet lithography technology. In another possible example, the silicon carbide film 113 can be etched using inductively coupled plasma reactive etching technology. During the etching process, a mixed gas of sulfur hexafluoride and oxygen can be used for etching. After the etching is completed, a diluted hydrofluoric acid solution is used to remove the remaining photoresist.

[0043] The waveguide portion may include a tapered waveguide 121 and a straight waveguide 120. The tapered waveguide 121 may be connected to the first end 131 of the grating portion, and the width of the tapered waveguide 121 increases in the direction from the first end 131 to the second end 132. Specifically, the width of the tapered waveguide 121 on the side close to the first end 131 is consistent with the width of the first end 131 of the grating portion. The straight waveguide 120 may be located on the side of the tapered waveguide 121 away from the grating portion, and the straight waveguide 120 includes a ridge waveguide. The straight waveguide 120 may extend along the first direction. Specifically, the cross-sectional view of the straight waveguide 120 may be rectangular or trapezoidal to increase the stability of the straight waveguide 120. It can be understood that the shape of the cross-sectional view of the straight waveguide 120 depends on the processing effect. Of course, the waveguide portion may also be provided with other waveguides, such as curved waveguides, etc., and this embodiment does not limit the specific composition of the waveguide portion.

[0044] The optical fiber may be located on a side of the grating portion away from the substrate 110. The optical fiber may be a single-mode optical fiber. The optical fiber may receive the light beam diffracted upward by the first grating portion 133. The orthographic projection of the optical fiber on the substrate 110 overlaps with the orthographic projection of the first grating portion 133 on the substrate 110. As an example, the orthographic projection of the optical fiber on the substrate 110 may be located within the orthographic projection of the first grating portion 133 on the substrate 110.

[0045] In this embodiment, the duty cycle of the first grating portion 133 is reduced, so that the diffraction field of the first grating portion 133 can be smoothly adjusted in the first grating portion 133, so that the diffraction field of the first grating portion 133 is more matched with the mode field of the optical fiber. At the same time, the period of the first grating portion 133 is increased, so that when the duty cycle is reduced, the grating diffraction field still basically meets the phase matching condition, thereby increasing the coupling efficiency of the grating coupler 100.

[0046] In addition, in the technical field of grating coupler 100, silicon-based and lithium niobate are often used as grating coupler materials. In this embodiment, the material of grating coupler 100 can be silicon carbide. Silicon carbide grating coupler has better advantages in electrical properties, thermal properties and mechanical properties, which further increases the application prospects of grating coupler 100 provided in this embodiment.

[0047] In one embodiment, the grating portion includes a second grating portion 134 .

[0048] The second grating portion 134 may be located on a side of the first grating portion 133 close to the first end 131. The second grating portion 134 is surrounded to form a plurality of rectangular grooves 1341. The depth of the rectangular grooves may be consistent with the depth of the grating grooves of the first grating portion 133 (the grating grooves may be the depth of each grating unit in the first grating portion 133). As an example, the second grating portion 134 may be surrounded to form a plurality of columns of rectangular grooves 1341 arranged along a first direction (X direction), and each column has a plurality of rectangular grooves 1341 spaced apart along a second direction (Y direction). The second direction intersects with the first direction, for example, the second direction is perpendicular to the first direction. The first direction includes the extension direction of the grating layer 130.

[0049] In the same column of rectangular grooves 1341, the lengths of the plurality of rectangular grooves 1341 in the second direction (eg, Figure 4 The length w shown in 1，y ) are consistent, and / or, the spacing between adjacent rectangular grooves 1341 in the second direction (for example, Figure 4 The length d shown in 1，y ) are consistent, and / or, the lengths of the plurality of rectangular grooves 1341 in the first direction (eg, Figure 4 The length w shown in 1，x ) are consistent.

[0050] In different columns of rectangular grooves 1341, the length of the rectangular grooves 1341 in the first direction increases in the direction from the first end 131 to the second end 132. As an example, in the same column of rectangular grooves 1341, the area of ​​each rectangular groove 1341 is equal. In different columns of rectangular grooves 1341, the area of ​​the rectangular grooves 1341 increases in the direction from the first end 131 to the second end 132.

[0051] In this embodiment, the distance d between adjacent rows of rectangular grooves 1341 is 1，x No specific limitation.

[0052] In this embodiment, the second grating portion 134 is provided to form a plurality of rectangular grooves 1341, so that the equivalent refractive index of the second grating portion 134 can be adjusted by the position and shape of the rectangular grooves 1341. Moreover, in different rows of rectangular grooves 1341, in the direction from the first end 131 to the second end 132, the length of the rectangular grooves 1341 in the second direction increases, so that the equivalent refractive index of the second grating portion 134 is between the equivalent refractive index of the waveguide portion and the equivalent refractive index of the first grating portion 133, so that when the light beam of the waveguide portion is transmitted to the first grating portion 133 through the second grating portion 134, its transmittance is close to 1, so that the reflectivity of the grating coupler 100 is as low as 1%, reducing the loss of the light beam. Furthermore, the first grating portion 133 and the second grating portion 134 in the grating layer of this embodiment are arranged in parallel, so that no overlay is required during preparation, which reduces the difficulty of preparation.

[0053] The following is an exemplary description of the grating coupler 100 provided in one or more embodiments of the present application. First, a silicon support substrate 111, an insulator 112, and a silicon carbide film 113 are formed in sequence. Among them, the material of the insulator 112 can be silicon dioxide, and the thickness of the silicon dioxide can be in the range of 2.8μm-3.2μm, or the thickness of the silicon dioxide can be in the range of 1.8μm-2.2μm. For example, the thickness of silicon dioxide can be 3μm. The silicon carbide film 113 can be between 50nm-250nm.

[0054] The straight waveguide 120 is a ridge waveguide, the width of the ridge waveguide may be between 0.6 μm and 1.2 μm, and the height of the ridge waveguide may be between 0.3 μm and 0.35 μm. For example, the width of the ridge waveguide may be 1 μm, and the height of the ridge waveguide may be 0.3 μm.

[0055] The leftmost width of the tapered waveguide 121 is equal to the width of the straight waveguide 120, the rightmost width of the tapered waveguide 121 is equal to the width of the first grating portion 133, and the length of the tapered waveguide 121 may be greater than 250 μm, so that the coupling efficiency of the tapered waveguide 121 is greater than 98%. For example, the length of the tapered waveguide 121 may be 300 μm, at which time, the coupling efficiency of the tapered waveguide 121 is 99%.

[0056] The first grating portion 133 is arranged along the X direction to form a plurality of columns of rectangular grooves 1341, and the number of columns may be between 2 and 4. For example, the first grating portion 133 may have 2 columns of rectangular grooves 1341. Each column of rectangular grooves 1341 may be rectangular. In the same column of rectangular grooves 1341, the width along the first direction (X direction) may be equal, and the length along the second direction (Y direction) may be equal. For example, the width along the first direction of the rectangular grooves 1341 in the first column may be 150 nm. Furthermore, in the same column of rectangular grooves 1341, the spacing between adjacent rectangular grooves 1341 in the second direction is consistent. Specifically, in one possible example, for the i-th (i=1, 2) column, the width of each rectangular groove 1341 in the second direction is w 1，y (i) In the same column, the distance between two adjacent rectangular grooves 1341 is d 1，y (i) It can be understood that the number of rectangular slots 1341 of the first grating portion 133 depends on w 1，y (i)+d 1，y (i) and the width (W) of the first grating portion 133. By adjusting w 1，y (i) and d 1，y (i) can adjust the equivalent refractive index of the first grating portion 133. 1，y (1) = 0.156 μm, d 1，y (1) = 0.344 μm, w 1，y (2) = 0.219 μm, d 1，y (2) = 0.281 μm.

[0057] The second grating portion 134 is provided with a plurality of columns of grating units along the first direction, and the number of columns N of the grating units may be in the range of 15-20. For example, the number of columns N may be 19. For the qth column, the width of the rectangular groove 1341 is recorded as w 2 (q), the distance between the rectangular grooves 1341 is denoted as d 2 (q), by linearly reducing the duty cycle F(q) = w 2 (q) / [d 2 (q)+w 2 (q)] so that the diffracted light field of the second grating portion 134 matches the optical fiber mode field, thereby improving the coupling efficiency.

[0058] The change of F(q) may cause the configuration to fail to meet the phase matching condition. In this case, the period Λ(q) = [d 2 (q)+w 2(q)] compensation. After F(1) ... F(N) and Λ(1) ... Λ(N) are determined, the duty cycle F(q) and period Λ(q) of the qth column can be determined. Afterwards, a variety of algorithms can be used to optimize the values ​​of F(1) ... F(N) and Λ(1) ... Λ(N), which can improve the coupling efficiency of the grating coupler 100. Exemplarily, F(1) = 0.83 ... F(N = 19) = 0.28, and correspondingly, Λ(1) = 795nm ... Λ(N = 19) = 983nm.

[0059] As mentioned above, the change of the duty cycle of the first grating portion 133 will change the diffraction angle. In order to compensate for the change of the diffraction angle, the first grating portion 133 linearly increases the period length along the first direction so that when the duty cycle decreases, the grating diffraction field still basically meets the phase matching condition.

[0060] In addition, the height of the first grating portion 133 and the second grating portion 134 can be between 300nm and 350nm. For example, the height of the first grating portion 133 and the second grating portion 134 can be 300nm. Moreover, the height of the grating portion is consistent with the height of the waveguide portion, thereby reducing the difficulty of etching. Of course, the height of the grating portion may also be inconsistent with the height of the waveguide portion, thereby obtaining other forms of grating couplers 100.

[0061] After performing simulation experiments using the grating coupler 100 provided by one or more embodiments of the present application, a coupling efficiency spectrum of the grating coupler 100 is obtained. For example, the coupling efficiency spectrum of the grating coupler 100 ( Figure 5 ) shows that at a wavelength of 1553nm, the efficiency (CE) of the transverse electric field (TE) polarized waveguide mode coupled to the optical fiber reaches 80%. The transverse electric field here refers to the polarization direction along the Figure 4 The electric field in the Y direction is shown. In the 10nm band, the coupling efficiency (CE) is higher than 75%. It can be seen that the coupling efficiency of the grating coupler 100 of the present application is high. After performing a simulation experiment using the grating coupler 100 provided by one or more embodiments provided by the present application, a grating reflectivity spectrum is obtained. As shown in the grating reflectivity spectrum ( Figure 6 ), at a wavelength of 1553nm, the reflectivity (R) is as low as 0.34%, and within a wavelength range of 10nm, the reflectivity (R) is less than 1%. It can be seen that the reflectivity of the grating coupler 100 of the present application is relatively low. Therefore, the grating coupler 100 provided by the present application has a relatively superior performance.

[0062] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that "this embodiment" or "one embodiment" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present disclosure. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification may not necessarily refer to the same embodiment.

[0063] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features of the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] The embodiments described above only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all fall within the scope of protection of the present application. Therefore, the scope of protection of the patent of the present application shall be subject to the attached claims. The above description is only a preferred implementation method of the present disclosure, and does not limit the scope of the patent of the present disclosure. All equivalent structural transformations made by using the contents of the present disclosure specification and drawings under the inventive concept of the present disclosure, or direct / indirect application in other related technical fields are included in the scope of protection of the patent of the present disclosure.

Claims

1. A grating coupler, characterized in that: include: substrate; a grating layer, located at one side of the substrate, the grating layer comprising a waveguide portion and a grating portion, the grating portion comprising a first end and a second end arranged opposite to each other in an extending direction of the grating layer, the first end being used to connect the waveguide portion, and the grating portion comprising a first grating portion, in a direction from the first end to the second end, a duty cycle of the first grating portion decreases and a period increases; The optical fiber is located at a side of the grating portion away from the substrate, and an orthographic projection of the optical fiber on the substrate overlaps with an orthographic projection of the first grating portion on the substrate.

2. The grating coupler according to claim 1, characterized in that: In a direction from the first end to the second end, the duty cycle of the first grating portion decreases linearly.

3. The grating coupler according to claim 1, characterized in that: The grating portion includes a second grating portion, the second grating portion is located on a side of the first grating portion close to the first end, and the second grating portion is surrounded to form a plurality of rectangular grooves.

4. The grating coupler according to claim 3, characterized in that: The second grating portion is surrounded to form a plurality of rows of rectangular grooves arranged along a first direction, each row having a plurality of rectangular grooves spaced apart along a second direction, the second direction intersects the first direction, and the first direction includes an extension direction of the grating layer.

5. The grating coupler according to claim 4, characterized in that: In the same column of rectangular grooves, the lengths of the plurality of rectangular grooves in the second direction are consistent, and / or the intervals between adjacent rectangular grooves in the second direction are consistent.

6. The grating coupler according to claim 4, characterized in that: In different columns of rectangular grooves, in a direction from the first end to the second end, the length of the rectangular groove in the second direction increases.

7. The grating coupler according to claim 1, characterized in that: The substrate comprises a supporting layer and an insulating layer, the grating portion is located on a side of the insulating layer away from the supporting layer, and the thickness of the insulating layer is not less than 1.8 μm.

8. The grating coupler according to claim 1, characterized in that: The waveguide portion comprises: A tapered waveguide is connected to the first end of the grating portion, and a width of the tapered waveguide increases in a direction from the first end to the second end.

9. The grating coupler according to claim 8, characterized in that: The width of the tapered waveguide on one side close to the first end is consistent with the width of the first end of the grating portion.

10. The grating coupler according to claim 8, characterized in that: The grating coupler comprises: A straight waveguide is located at a side of the tapered waveguide away from the grating portion, wherein the straight waveguide comprises a ridge waveguide.

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