Optical splitter chip, preparation method of optical splitter chip, and optical equipment

Abstract

The invention relates to an optical splitter chip, a preparation method of the optical splitter chip and optical equipment. According to the optical splitter chip provided by the invention, an optical waveguide core layer comprises a first optical splitting structure, an optical splitting assembly and an output waveguide assembly; the light splitting assembly comprises at least one column of light splitting array; each column of light splitting array comprises a plurality of sub light splitting structures; any light splitting structure comprises an input waveguide, a multi-mode interference waveguide and a plurality of output waveguides; each output waveguide of the first light splitting structure is coupled with an input waveguide of one sub light splitting structure in the first column of light splitting array through a transition waveguide; each output waveguide of each sub-light-splitting structure in each column of light-splitting array is coupled with an input waveguide of one sub-light-splitting structure in the next column of light-splitting array after the sub-light-splitting structure in each column of light-splitting array through a transition waveguide; and each output waveguide of each sub light splitting structure in the last column of light splitting array is coupled with one final output waveguide in the output waveguide assembly, so that the channel expansion capability is improved.

Description

Technical Field

[0001] This application relates to the field of optics, and in particular to a beam splitter chip, a method for fabricating the beam splitter chip, and an optical device. Background Technology

[0002] In high-precision magnetic field measurement systems, spin-exchange relaxation-free (SERF) magnetometers have been widely used in biomedical imaging devices such as magnetic resonance imaging of the heart and brain. These biomedical imaging devices typically require multiple probes to improve spatial resolution. In recent years, a solution combining lasers and beam splitters has been commonly adopted, splitting a single optical signal emitted by the laser into multiple optical signals for output to the probe array.

[0003] Currently, polarizing beam splitters (PBS) are commonly used to achieve beam splitting. However, PBS beam splitters are relatively large and have poor channel expansion capabilities. Summary of the Invention

[0004] This embodiment provides a beam splitter chip, a method for fabricating the beam splitter chip, and an optical device to improve the channel expansion capability of the beam splitter chip.

[0005] In a first aspect, this embodiment provides a beam splitter chip, which includes a substrate, an optical waveguide core layer, an optical waveguide cladding layer, and a cover plate sequentially disposed on the substrate.

[0006] The optical waveguide core layer includes a first beam splitting structure, a beam splitting component, and an output waveguide component connected in sequence; the beam splitting component includes at least one beam splitting array; each beam splitting array includes multiple sub-beam splitting structures; along the direction of light transmission, any one of the first beam splitting structure and the sub-beam splitting structures includes an input waveguide, a multimode interference waveguide, and multiple output waveguides;

[0007] Each output waveguide of the first beam splitting structure is coupled to the input waveguide of a sub-beam splitting structure in the first column of the beam splitting assembly via a transition waveguide; each output waveguide of each sub-beam splitting structure in each column of the beam splitting assembly is coupled to the input waveguide of a sub-beam splitting structure in the next column of the beam splitting array following that column via a transition waveguide.

[0008] The output waveguide assembly includes multiple final output waveguides; each output waveguide of each sub-splitter in the last column of the beam splitter array is coupled to one of the final output waveguides in the output waveguide assembly.

[0009] Secondly, this embodiment provides a method for fabricating a beam splitter chip, the method being used to fabricate the beam splitter chip according to any one of the first aspects of this application; the fabrication method includes:

[0010] An optical waveguide material layer is deposited on a substrate, and a pattern identical to that of the optical waveguide core layer to be prepared is formed on the optical waveguide material layer.

[0011] The optical waveguide material layer is etched to form an optical waveguide core layer on the substrate;

[0012] An optical waveguide cladding is deposited on the optical waveguide core layer;

[0013] A cover plate is bonded to the optical waveguide cladding to form a beam splitter chip.

[0014] Thirdly, this embodiment provides an optical device, which includes the beam splitter chip described in any of the first aspects of this application.

[0015] Compared to related technologies, the beam splitter chip provided in this embodiment, by setting a primary beam splitting structure and beam splitting components in the optical waveguide core layer, and designing the beam splitting components to include at least one column of beam splitting arrays, can achieve initial beam splitting through the primary beam splitting structure and further beam splitting in combination with the beam splitting components, thus achieving multi-stage beam splitting. Therefore, the number of output waveguides of the primary beam splitting structure, the number of beam splitting arrays, and the number of sub-beam splitting structures in each column of beam splitting arrays can be flexibly adjusted according to actual needs, facilitating channel expansion to achieve different numbers of channels in different application scenarios. Furthermore, the coupling between the primary beam splitting structure and the beam splitting components, as well as between each column of beam splitting arrays, through transition waveguides, can effectively reduce mutual interference between optical paths and ensure stable transmission of optical signals.

[0016] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0018] Figure 1 This is a schematic diagram of the structure of a beam splitter chip shown in an exemplary embodiment of this application;

[0019] Figure 2 This is a schematic diagram of an exemplary embodiment of the optical waveguide core layer shown in this application;

[0020] Figure 3 A schematic diagram of an optical waveguide core layer shown in another exemplary embodiment of this application;

[0021] Figure 4 This is a schematic diagram of a beam-splitting structure shown in an exemplary embodiment of this application;

[0022] Figure 5 A flowchart illustrating a method for fabricating a beam splitter chip, as shown in an exemplary embodiment of this application;

[0023] Figure 6 This is a schematic diagram of an optical device shown as an exemplary embodiment of this application.

[0024] Explanation of reference numerals in the attached figures:

[0025] 100: Substrate;

[0026] 200: Optical waveguide core layer;

[0027] 300: Optical waveguide cladding;

[0028] 400: Cover plate;

[0029] 1: First beam splitting structure;

[0030] 11: Input waveguide;

[0031] 111: Direct-input waveguide;

[0032] 112: Tapered input waveguide;

[0033] 1121: First input terminal;

[0034] 1122: First output terminal;

[0035] 12: Multimode interferometric waveguide;

[0036] 13: Output waveguide;

[0037] 131: Tapered output waveguide;

[0038] 1311: Second input terminal;

[0039] 1312: Second output terminal;

[0040] 132: Direct output waveguide;

[0041] 2: Spectrophotometer;

[0042] 21: Beam splitter array;

[0043] 211: Sub-spectral structure;

[0044] 3: Output waveguide assembly;

[0045] 31: Final output waveguide;

[0046] 4: Transition waveguide. Detailed Implementation

[0047] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0048] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “a,” “the,” “the,” and “these” used in this application do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion. Words such as “connected,” “linked,” and “coupled” used in this application are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. Generally, the character “ / ” indicates that the objects before and after it are in an “or” relationship. The terms “first,” “second,” and “third” used in this application are merely for distinguishing similar objects and do not represent a specific ordering of objects.

[0049] The following specific embodiments are provided to illustrate the technical solution of this application in detail.

[0050] Figure 1 This is a schematic diagram of the structure of a beam splitter chip shown in an exemplary embodiment of this application; Figure 2 This is a schematic diagram of an optical waveguide core layer shown in an exemplary embodiment of this application. Figure 3 This is a schematic diagram of an optical waveguide core layer shown in another exemplary embodiment of this application. Please also refer to... Figures 1 to 3 The beam splitter chip provided in this embodiment includes a substrate 100, an optical waveguide core layer 200, an optical waveguide cladding layer 300 and a cover plate 400 sequentially disposed on the substrate;

[0051] The optical waveguide core layer 200 includes a first beam splitting structure 1, a beam splitting component 2, and an output waveguide component 3 connected in sequence; the beam splitting component 2 includes at least one beam splitting array 21; each beam splitting array 21 includes multiple sub-beam splitting structures 211; along the direction of light transmission, any one of the first beam splitting structure 1 and the sub-beam splitting structure 211 includes an input waveguide 11, a multimode interference waveguide 12, and multiple output waveguides 13;

[0052] Each output waveguide 13 of the first beam splitting structure 1 is coupled to the input waveguide 11 of a sub-beam splitting structure 211 in the first column of beam splitting array in the beam splitting component 2 via a transition waveguide 4; each output waveguide 13 of each sub-beam splitting structure 211 in each beam splitting array in the beam splitting component 2 is coupled to the input waveguide 11 of a sub-beam splitting structure 211 in the next column of beam splitting array after that column of beam splitting array via a transition waveguide 4.

[0053] The output waveguide assembly 3 includes a plurality of final output waveguides 31; each output waveguide 13 of each sub-splitting structure 211 in the last column of the beam splitting array is coupled to one of the final output waveguides 31 in the output waveguide assembly 3.

[0054] Optionally, in one possible implementation, the length of the beam splitter chip is 5~80mm, the width is 2~30mm, and the height is 0.2~5mm.

[0055] It should be noted that in this embodiment, the length direction is the direction of light propagation, the width direction is in the same horizontal plane as the length direction, and the width direction is perpendicular to the length direction; furthermore, the height direction is perpendicular to the horizontal plane. For details, please refer to... Figure 1 The length direction is Figure 1 The left and right directions, and the width direction are Figure 1 The direction perpendicular to the paper surface, and the height direction is Figure 1 The up and down directions in the middle.

[0056] Please continue to refer to Figure 1 The substrate 100 is made of silicon dioxide and has a thickness of 0.2~2mm; the waveguide core layer 200 can be made of silicon, silicon dioxide, silicon nitride or lithium niobate; the waveguide cladding 300 is made of silicon dioxide and has a thickness of 0.5~30μm; the cover plate is made of glass.

[0057] It is understandable that the refractive index of the optical waveguide core layer 200 is greater than that of the optical waveguide cladding layer 300, so that the optical signal can be transmitted in the optical waveguide core layer 200.

[0058] It should be noted that the refractive indices of the substrate 100, the optical waveguide core layer 200, and the optical waveguide cladding 300 are set according to actual needs, and are not limited in this embodiment. Optionally, in one possible implementation, the optical waveguide cladding 300 is made of silicon dioxide doped with germanium, phosphorus, and boron to adjust the refractive index so that it is equal to the refractive index of the substrate 100.

[0059] Please continue to refer to Figure 1 along Figure 1Viewed vertically, the beam splitter chip has a trapezoidal structure, meaning that the normals at the input and output ends of the chip are at certain angles to the optical axis. Optionally, in one possible implementation, the inclination angle of the input end is -8° and the inclination angle of the output end is +8° to reflect echoes, improve fiber coupling efficiency, and reduce interference between multiple optical paths.

[0060] It should be noted that the tangential tilt angle of the input and output ends refers to the angle between the normal of the end face and the optical axis of the beam splitter chip, with clockwise as the positive direction and counterclockwise as the negative direction.

[0061] The following section provides a detailed description of the waveguide core layer 200. For further details, please refer to [link / reference needed]. Figure 2 and Figure 3 The optical waveguide core layer 200 includes a first beam splitting structure 1, a beam splitting component 2, and an output waveguide component 3 connected in sequence.

[0062] Specifically, the initial beam splitting structure 1 includes an input waveguide 11, a multimode interference waveguide 12, and multiple output waveguides 13. The input waveguide 11 receives externally input optical signals and transmits them to the multimode interference waveguide 12. The multimode interference waveguide 12 modulates the input optical signals using multimode interference, creating a specific interference distribution within the cross-section of the multimode interference waveguide 12, thereby generating multiple optical signals at the output waveguides 13. The multiple output waveguides 13 form an output waveguide array, used to extract the split optical signals respectively.

[0063] It should be noted that the number of output waveguides 13 included in the first beam splitting structure 1 is set according to actual needs, and in this embodiment, its specific number is not limited. Optionally, in a specific implementation, the first beam splitting structure 1 includes 2 to 16 output waveguides 13.

[0064] As described above, it can be understood that the first beam splitting structure 1 is an MMI beam splitting structure (Multimode Interference, or MMI for short). When the optical signal enters the multimode interference waveguide 12 from the input waveguide 11, different propagation modes coherently superimpose in this region, forming a periodic light intensity distribution, which can achieve the same power beam splitting effect at the output waveguide 13.

[0065] In addition, the first beam splitting structure 1 is a planar lightwave circuit (PLC), which means that the light waveguide is located in a plane.

[0066] Please continue to refer to Figure 2 and Figure 3 After the first beam splitting structure 1, a beam splitting component 2 is coupled, which is used to further split the optical signal.

[0067] Specifically, the beam splitting component 2 includes at least one column of beam splitting arrays 21. It should be noted that the number of beam splitting arrays 21 included in the beam splitting component 2 is determined according to actual needs, and is not limited in this embodiment. For example, in... Figure 2 In the example shown, the beam-splitting component 2 includes a beam-splitting array 21. For example, in... Figure 3 In the example shown, the beam splitting component 2 includes two beam splitting arrays 21.

[0068] It should be noted that, for ease of distinction, the multi-column beam-splitting array 21 is referred to as the first beam-splitting array, the second beam-splitting array, etc., according to the direction of light propagation. Please continue to see... Figure 2 and Figure 3 When there is no next beam splitter array after a certain beam splitter array, that beam splitter array is the first beam splitter array, which is located at the very end of the propagation path. It can be understood that when the beam splitter component 2 includes only one beam splitter array, that beam splitter array is both the first beam splitter array and the last beam splitter array.

[0069] Please continue to refer to Figure 2 and Figure 3 Each beam splitter array 21 includes multiple sub-beam splitter structures 211. The specific morphology of the sub-beam splitter structure 211 is the same as that of the first beam splitter structure 1, and will not be described again here.

[0070] Furthermore, the number of sub-splitting structures 211 included in each beam splitter array 21 is equal to the number of optical signals output by its preceding beam splitter. It can be understood that, for the first beam splitter array, its preceding beam splitter is the first beam splitter structure 1. When multiple beam splitter arrays are included, for beam splitter arrays other than the first beam splitter array, its preceding beam splitter is the beam splitter array preceding that beam splitter array. For example, in... Figure 2 In the example shown, when the beam splitter component 2 includes only the first beam splitter array, the number of sub-beam splitter structures included in the first beam splitter array is equal to the number of optical signals output by the first beam splitter structure 1, that is, the number of sub-beam splitter structures included in the first beam splitter array is equal to the number of output waveguides 13 of the first beam splitter structure 1. For example, in... Figure 3 In the example shown, when the beam splitting component 2 includes a first beam splitting array and a second beam splitting array, the number of sub-beam splitting structures included in the first beam splitting array is equal to the number of output waveguides 13 of the first beam splitting structure 1, and the number of sub-beam splitting structures included in the second beam splitting array is equal to the number of optical signals output by the first beam splitting array.

[0071] Referring to the preceding description, for example, in one possible implementation, in Figure 2In the example shown, the first beam splitting structure is a 1-to-16 structure, meaning that the first beam splitting structure includes 16 output waveguides. In this case, the first column beam splitting array can be configured with 16 sub-beam splitting structures. One output waveguide of the first beam splitting structure is coupled to the input waveguide of one sub-beam splitting structure of the first column beam splitting array.

[0072] Furthermore, for example, in one possible implementation, in Figure 2 In the example shown, each sub-splitter may include 16 output waveguides. Figure 2 The splitter chip shown can achieve 256 outputs.

[0073] For example, in another possible implementation, in Figure 3 In the example shown, the first beam splitter structure is a 1-to-16 structure, meaning it includes 16 output waveguides. In this case, the first column of the beam splitter array has 16 sub-beam splitters, and each output waveguide of the first beam splitter structure 1 is coupled to the input waveguide of one of the sub-beam splitters in the first column of the beam splitter array. Further, each sub-beam splitter structure is a 1-to-8 structure. In this case, the first column of the beam splitter array outputs a total of 128 optical signals. Correspondingly, the second column of the beam splitter array has 128 sub-beam splitters, and one output waveguide of each sub-beam splitter in the first column of the beam splitter array is coupled to the input waveguide of one of the sub-beam splitters in the second column of the beam splitter array. As another example, in this case, each sub-beam splitter structure in the second column of the beam splitter array is a 1-to-2 structure. In this case, the beam splitter chip can also achieve 256 outputs.

[0074] Please continue to refer to Figure 2 and Figure 3 The specific morphology of the transition waveguide 4 is determined according to actual needs. In this embodiment, it is not limited and can be a straight waveguide or a curved waveguide. Furthermore, the angle of the curved waveguide is ≤12° and the bending radius is 10000~50000μm.

[0075] For further details, please refer to [link / reference]. Figure 2 and Figure 3 The output waveguide assembly 3 includes a plurality of final output waveguides 31; each output waveguide of each sub-splitting structure in the last column of the beam splitting array is coupled to one of the final output waveguides 31 in the output waveguide assembly 3.

[0076] For example, in Figure 2 and Figure 3 In the example shown, the output waveguide assembly 3 includes 256 final output waveguides 31, with each output waveguide of each sub-splitter in the last beam splitter array coupled to one final output waveguide 31.

[0077] The following is based on Figure 2Taking this as an example, let's briefly introduce the working principle of this beam splitter chip. Specifically, the optical signal first enters the first beam splitting structure, where it undergoes the first beam splitting. Further, the split optical signals enter the sub-beam splitting structures in the first column of the beam splitting array, where they undergo the second beam splitting. After the second beam splitting, the split optical signals are output through the final output waveguide.

[0078] The beam splitter chip provided in this embodiment, by setting a primary beam splitting structure and beam splitting components in the optical waveguide core layer, and designing the beam splitting components to include at least one column of beam splitting arrays, can achieve initial beam splitting through the primary beam splitting structure and further beam splitting in combination with the beam splitting components, thus achieving multi-stage beam splitting. This allows for flexible adjustment of the number of output waveguides in the primary beam splitting structure, the number of beam splitting arrays, and the number of sub-beam splitting structures in each column of beam splitting arrays according to actual needs, facilitating channel expansion to achieve different numbers of channels in different application scenarios. Furthermore, the coupling between the primary beam splitting structure and the beam splitting components, as well as between each column of beam splitting arrays, through transition waveguides, effectively reduces mutual interference between optical paths, ensuring stable transmission of optical signals.

[0079] Furthermore, Figure 4 This is a schematic diagram illustrating a beam-splitting structure in an exemplary embodiment of this application. The beam-splitting structure may be a primary beam-splitting structure or a sub-beam-splitting structure; please refer to... Figure 4 In one possible implementation, the input waveguide 11 includes a straight input waveguide 111 and a tapered input waveguide 112 coupled to each other; each of the output waveguides 13 includes a tapered output waveguide 131 and a straight output waveguide 132 coupled to each other.

[0080] Both the direct input waveguide 111 and the direct output waveguide 132 are rectangular structures;

[0081] The tapered input waveguide 112 is a trapezoidal structure including a first input end 1121 and a first output end 1122; the width of the first input end 1121 is smaller than the width of the first output end 1122;

[0082] The tapered output waveguide 131 is a trapezoidal structure including a second input terminal 1311 and a second output terminal 1312; the width of the second input terminal 1311 is greater than the width of the second output terminal 1312.

[0083] Specifically, along the direction of light propagation, the direct input waveguide 111 is coupled to the tapered input waveguide 112, the tapered input waveguide 112 is coupled to the beginning of the multimode interference waveguide 12, the end of the multimode interference waveguide 12 is coupled to the tapered output waveguide 131, and the tapered output waveguide 131 is coupled to the direct output waveguide 132.

[0084] It should be noted that both the direct input waveguide 111 and the direct output waveguide 132 are rectangular structures, and their specific dimensions are set according to actual needs. In this embodiment, their specific dimensions are not limited. Similarly, both the tapered input waveguide 112 and the tapered output waveguide 131 are trapezoidal structures.

[0085] It should be noted that, along the width direction, the straight input waveguide 111 and the tapered input waveguide 112 can be coaxially arranged (specifically, coaxial arrangement means that the optical axes of the straight input waveguide 111 and the tapered input waveguide 112 are on the same straight line), or they can be non-coaxially arranged (specifically, non-coaxial arrangement means that the optical axes of the straight input waveguide 111 and the tapered input waveguide 112 are not on the same straight line). In this embodiment, no limitation is imposed. For example, in Figure 3 In the example shown, the straight input waveguide 111 and the tapered input waveguide 112 are coaxially arranged. Similarly, the tapered output waveguide 131 and the straight output waveguide 132 can be coaxially arranged or non-coaxially arranged; this embodiment does not limit their arrangement.

[0086] For details, please continue to refer to... Figure 3 The tapered input waveguide 112 includes a first input terminal 1121 and a first output terminal 1122, the width of the first input terminal 1121 being smaller than the width of the first output terminal 1122. Similarly, the tapered output waveguide 131 includes a second input terminal 1311 and a second output terminal 1312, the width of the second input terminal 1311 being larger than the width of the second output terminal 1312.

[0087] It should be noted that the widths of the first input terminal 1121, the first output terminal 1122, the second input terminal 1311, and the second output terminal 1312 are set according to actual needs, and are not limited in this embodiment.

[0088] Furthermore, the relationship between the width of the direct input waveguide 111 and the width of the first input terminal 1121 is set according to actual needs, and is not limited in this embodiment. Similarly, the relationship between the width of the second output terminal 1312 and the width of the direct output waveguide 132 is also set according to actual needs, and is not limited in this embodiment.

[0089] Furthermore, in this embodiment, the waist of the trapezoidal structure can be a straight line or a curve; in this embodiment, it is not limited to either.

[0090] The beam splitter chip provided in this embodiment designs its input waveguide as a combination of a straight input waveguide and a tapered input waveguide, and its output waveguide as a combination of a tapered output waveguide and a straight output waveguide. Firstly, the tapered input and output designs, by gradually changing the waveguide cross-section, allow for a smooth transition of the optical signal during input and output, optimizing coupling efficiency and reducing optical signal loss. Secondly, the combination of the rectangular structure of the straight waveguide and the trapezoidal structure of the tapered waveguide effectively transforms the optical field from a rectangular waveguide mode to a trapezoidal waveguide mode at the input end, and vice versa at the output end. This enables more efficient signal transmission and avoids reflection or loss due to cross-section mismatch. Furthermore, by adjusting the width ratio of the tapered and straight waveguides, the propagation characteristics of the optical signal can be flexibly adjusted, further optimizing the system's performance in different application scenarios.

[0091] It should be noted that the laser in the SERF magnetometer typically operates in the short-wavelength band. For example, in one embodiment, the laser operates at 795nm. In this case, the beam splitter chip is also required to operate at 795nm and be able to achieve uniform beam splitting. Therefore, in this application, to achieve the above objectives, a special size design has been made to the beam splitter chip based on the above embodiments. The specific size design will be described in detail below.

[0092] Please continue to refer to Figure 2 and Figure 4 In one possible implementation, the beam splitting component includes a beam splitting array, and each beam splitting structure includes 2 to 16 output waveguides;

[0093] The height of the optical waveguide core layer is 0.2~5μm;

[0094] The length of the direct input waveguide is 200~2000μm;

[0095] The tapered input waveguide has an isosceles trapezoidal structure; the length of the tapered input waveguide is 50~1000μm; the width of the first input end is the same as the width of the straight input waveguide, and the width of the first output end is 5~20μm;

[0096] The multimode interference waveguide has a rectangular structure; the length of the multimode interference waveguide is 200~8000μm, and the width of the multimode interference waveguide is 20~300μm.

[0097] The tapered output waveguide has an isosceles trapezoidal structure; the length of the tapered output waveguide is 50~1000μm; the width of the second input end is 3~20μm; the width of the second output end is the same as the width of the straight output waveguide;

[0098] The length of the direct output waveguide is 1~200μm;

[0099] The widths of both the direct input waveguide and the direct output waveguide are equal to the height of the optical waveguide core layer.

[0100] In this embodiment, the beam splitter chip includes a beam splitter array. Furthermore, the number of output waveguides for each beam splitter structure is limited to between 2 and 16, thus balancing beam splitting accuracy and device size.

[0101] It should be noted that, in one possible implementation, the dimensional parameters of the optical waveguide core layer are determined according to the following method:

[0102] (1) Determine the width of the optical waveguide core layer based on the spacing between two adjacent final output waveguides.

[0103] Specifically, the spacing between two adjacent final output waveguides is set according to actual needs, and is not limited in this embodiment. For example, in one possible implementation, the spacing between two adjacent final output waveguides matches the spacing between two adjacent optical fibers in the fiber array. Optionally, for example, in one embodiment, the spacing between two adjacent final output waveguides is 70~150μm. Further, once the spacing between two adjacent final output waveguides is determined, the width occupied by the output waveguide component can be obtained based on this spacing and the number of final output waveguides. Then, the width of the optical waveguide core layer is determined based on the width occupied by the output waveguide component. The width of the optical waveguide core layer is greater than the width occupied by the output waveguide component.

[0104] (2) Based on the fundamental mode transmission constraint and the aspect ratio constraint of the optical waveguide core layer, the height of the optical waveguide core layer is determined according to the desired operating wavelength, the refractive index deviation of the beam splitter chip, and the width of the optical waveguide core layer; the refractive index deviation is the difference between the refractive index of the optical waveguide core layer and the refractive index of the optical waveguide cladding; the height of the optical waveguide core layer is inversely proportional to the refractive index deviation of the beam splitter chip.

[0105] Specifically, in this step, the height of the optical waveguide core layer is determined using the normalized frequency V as the core criterion. The expression for the normalized frequency V is V = (2π / λ) × h × NA, where λ is the operating wavelength, h is the height of the optical waveguide core layer, and NA = (ncore² - nclad²)^(1 / 2), where ncore is the refractive index of the optical waveguide core layer and nclad is the refractive index of the optical waveguide cladding.

[0106] In practice, to ensure that the optical waveguide core layer only supports fundamental mode transmission, the normalized frequency needs to meet the fundamental mode transmission constraint condition, which is: (2π / λ)×h ×NA<π / 2.

[0107] Therefore, given a working wavelength, the geometric dimensions of the optical waveguide core layer are related to the refractive index deviation of the beam splitter chip (it should be noted that the refractive index deviation of the beam splitter chip is the difference between the refractive index of the optical waveguide chip and the refractive index of the optical waveguide cladding).

[0108] Furthermore, by combining the aspect ratio constraint of the optical waveguide core layer (aspect ratio less than or equal to 1) and optimizing the working wavelength and refractive index together, the height of the optical waveguide core layer can be determined.

[0109] In practical implementation, for example, once the materials of the optical waveguide core layer and the optical waveguide cladding are determined, the refractive index deviation of the beam splitter chip is also determined. Furthermore, according to the fundamental mode transmission constraint condition, the height of the optical waveguide core layer satisfies the following formula: h A×λ / 4NA. A is the preset safety factor, ranging from 0.6 to 0.95.

[0110] At this point, with the desired operating wavelength known, the maximum height can be calculated. Based on the aspect ratio constraint (w / h ≤ 1), it can be known that h... w, thus, given a fixed width of the waveguide core layer, the minimum height value can be further determined.

[0111] For example, in this embodiment, the desired operating wavelength is 795nm. Based on the selected material and refractive index, the height of the optical waveguide core layer is finally determined to be 0.2~5μm. This size can effectively suppress all higher-order modes at 795nm, achieve stable single-mode transmission, and provide a key basic structure for subsequent optical path integration.

[0112] It should be noted that after determining the width of the optical waveguide core layer, the dimensions of the transition waveguide, as well as the structure and dimensions of the beam splitter array, can be determined based on this width value. After determining the structure and dimensions of the beam splitter array, the dimensions of the primary beam splitter structure can then be further determined.

[0113] In this embodiment, by determining the size parameters of the optical waveguide core layer according to the spacing between two adjacent final output waveguides, the fundamental mode transmission constraint condition, and the core layer aspect ratio constraint condition, the optical waveguide can be limited to supporting only the fundamental mode transmission, avoiding multimode interference or mode coupling phenomena, thereby improving the stability of optical field transmission and the beam splitting accuracy.

[0114] It should be noted that you should continue to refer to... Figure 2 and Figure 4 In this embodiment, either the primary beam splitter structure or the sub-beam splitter structure includes multiple output waveguides, and the multiple tapered output waveguides of the multiple output waveguides constitute a multi-channel tapered array. This multi-channel tapered array is used to efficiently separate and extend the optical field output from the multimode interference waveguide to the straight output waveguide.

[0115] Furthermore, the width of each tapered output waveguide satisfies the following linear gradient function:

[0116] ;

[0117] Where W0 is the width of the second input terminal, W1 is the width of the second output terminal, L is the length of the tapered output waveguide, and a is a preset value.

[0118] Furthermore, the spacing S between two adjacent tapered output waveguides is determined based on the width W0 of the second input end and the number of tapered output waveguides to ensure that the output spot spacing meets the design requirements and minimizes mode matching loss. This spacing ranges from 3 to 50 μm. A larger spacing (≥3 μm) allows for better compatibility with traditional micro / nano fabrication processes and reduces the difficulty of cladding filling.

[0119] In this embodiment, when the desired operating wavelength is 795nm, W0, W1, S, and L are all optimized and determined by the beam propagation method based on the operating wavelength and the refractive index of the optical waveguide core layer, so as to achieve low insertion loss and high channel uniformity.

[0120] In practice, for example, with the objective function of maximizing channel uniformity, the output light field distribution is observed by scanning different W0, W1, L and S, and the output power is evaluated. When the output power is maximized and the light intensity of each channel is close to uniform, the corresponding parameters are the optimization results.

[0121] For details, please continue to refer to... Figure 2 In this embodiment, by setting the beam splitting array as a column and setting the number of multiple output waveguides in any beam splitting structure to 2 to 16, the number of output waveguides can be flexibly set according to the target number of beam splitting paths.

[0122] Please continue to refer to Figure 2 The direct-input waveguide has a rectangular structure with a length of 200–2000 μm. Furthermore, in one possible implementation, the width of the direct-input waveguide is equal to its height. This direct-input waveguide is used to receive optical signals from external optical fibers and stably guide them into the waveguide core, providing an input channel for mode field averaging.

[0123] Furthermore, in this embodiment, the tapered input waveguide is configured as an isosceles trapezoid with a length of 50–1000 μm. Furthermore, the width of the first input end of the tapered input waveguide is the same as that of the straight input waveguide, while the width of the first output end is 5–20 μm, with the input end width being smaller than the output end width. Thus, through the tapered transition structure, the optical field can achieve mode expansion from a narrow waveguide to a wider waveguide, reducing mode mismatch and reflection loss, thereby improving input coupling efficiency.

[0124] Furthermore, the multimode interference waveguide is the core functional area of ​​the beam splitter structure. Input light undergoes multimode interference within this region, forming a specific interference pattern. By precisely designing its length and width, equal-power beam splitting can be achieved at the output end.

[0125] Similarly, by setting the tapered output waveguide as an isosceles trapezoidal structure with a length of 50–1000 μm, a second input end width of 3–20 μm, and a second output end width that is the same as the width of the straight output waveguide, and the second input end width is greater than the second output end width, the tapered output waveguide can achieve mode contraction and output end matching, ensuring that the interference optical field is smoothly coupled to the straight output waveguide.

[0126] As described above, it is understood that the above structural parameters, through coordinated design in length and width, achieve the effects of low-loss coupling, high uniformity of beam splitting, and stable mode transmission, ensuring the excellent optical performance and manufacturing feasibility of the beam splitter chip at a working wavelength of 795 nm.

[0127] The beam splitter chip provided in this embodiment improves beam splitting uniformity and reduces coupling loss by precisely designing the structural dimensions of the input waveguide, multimode interference waveguide, and output waveguide. The specific principle is as follows:

[0128] (1) Core layer size and single-mode constraints

[0129] By setting the height of the optical waveguide core layer to 0.2~5 μm, V satisfies V < π / 2, thereby ensuring that the entire transmission path only supports the propagation of the fundamental mode.

[0130] (2) Tapered transition structure of the input waveguide

[0131] By configuring the input waveguide as a composite structure of a straight input waveguide and a tapered input waveguide, the incident light mode gradually transitions from a single-mode waveguide to a multimode interference region supporting multimode transmission. This gradually expanding structure effectively reduces reflection and scattering losses caused by mode mismatch, achieving a smooth broadening of the optical field distribution.

[0132] Furthermore, by designing the length of the tapered input waveguide within the range of 50~1000 μm, mode conversion can be completed within a limited chip length, thus avoiding high-order mode excitation.

[0133] (3) Mode self-imaging effect of multimode interferometric waveguide

[0134] By rationally designing the dimensions of the multimode interference waveguide, the multimode interference waveguide can achieve spatial redistribution of energy through optical self-imaging effect, generating multiple equal-amplitude output light fields.

[0135] In this embodiment, by optimizing the aspect ratio and length, it can be ensured that multiple equal-amplitude light fields are formed at predetermined positions at the output end, thereby achieving 2 to 16 channels of highly uniform beam splitting.

[0136] (4) The inverse conical convergence and straight-segment connection structure of the output waveguide

[0137] By setting the output waveguide as a composite structure of an inverse conical (shrinking) structure and a straight waveguide structure, the multiple light spots of the multimode interference output are efficiently coupled into the corresponding single-mode output waveguides through the inverse conical structure, thereby stabilizing the output light field and reducing end-face reflection through the straight waveguide part.

[0138] In summary, through the coordinated design of the structure and dimensions described above, the mode distribution of light can be continuously evolved between the input, interference and output regions, avoiding mode distortion caused by abrupt coupling. This enables the beam splitter chip provided in this embodiment to achieve low loss, high uniformity and multi-channel beam splitting output at a working wavelength of 795 nm, providing a structural basis for high-stability optical signal distribution.

[0139] Optionally, based on the above embodiments, in one possible implementation, any of the beam splitting structures includes eight output waveguides; the length of the tapered input waveguide is 500~600μm, and the width of the first output end is 9~10μm; the length of the multimode interference waveguide is 3000~5000μm, and the width of the multimode interference waveguide is 100~130μm; the length of the tapered output waveguide is 300~450μm, and the width of the second input end is 5~8μm.

[0140] It is understood that in this embodiment, the initial beam splitting structure includes 8 output waveguides, i.e., the initial beam splitting structure is a 1-to-8 beam splitting structure. Furthermore, the beam splitting component includes a beam splitting array, which in turn includes 8 sub-beam splitting structures. Each sub-beam splitting structure is coupled to one output waveguide of the initial beam splitting structure. Each sub-beam splitting structure further includes 8 output waveguides. Thus, the beam splitter chip can ultimately output 64 optical signals, achieving an overall 1-to-64 beam splitting effect.

[0141] Corresponding to the aforementioned embodiment of a beam splitter chip, this application also provides a method for fabricating a beam splitter chip. The method for fabricating the beam splitter chip provided in this application will be described below.

[0142] Figure 5 This is a flowchart illustrating a method for fabricating a beam splitter chip, as shown in an exemplary embodiment of this application. Please refer to... Figure 5 The method for fabricating a beam splitter chip provided in this embodiment is used to fabricate the beam splitter chip described in any of the first aspects of this application; the method includes:

[0143] S501. Deposit an optical waveguide material layer on a substrate and form a pattern on the optical waveguide material layer that is identical to the optical waveguide core layer to be prepared.

[0144] Specifically, a substrate material with good optical transparency and mechanical stability can be selected. In this embodiment, the substrate material can be silicon dioxide.

[0145] It should be noted that the substrate material and specific dimensional parameters are described above and will not be repeated here.

[0146] Furthermore, an optical waveguide material layer can be deposited on the substrate surface using methods such as chemical vapor deposition, plasma-enhanced chemical vapor deposition, or sputtering deposition. Subsequently, a predetermined pattern structure, identical to the optical waveguide core layer to be fabricated, can be formed on the optical waveguide material layer using photolithography.

[0147] It should be noted that the refractive index of the optical waveguide material layer can be adjusted by doping. For details on the specific implementation methods and principles of doping, please refer to the descriptions in relevant technologies, which will not be elaborated here.

[0148] S502. The optical waveguide material layer is etched to form an optical waveguide core layer on the substrate.

[0149] Specifically, in this step, dry etching or wet etching processes can be used to remove the areas not protected by photoresist, forming an optical waveguide core layer consistent with the predetermined pattern structure. This optical waveguide core layer determines the subsequent optical signal propagation path.

[0150] S503. Deposit an optical waveguide cladding on the optical waveguide core layer.

[0151] Specifically, in this step, a layer of optical waveguide cladding material is coated onto the surface of the optical waveguide core layer using methods such as chemical vapor deposition or plasma-enhanced chemical vapor deposition.

[0152] Understandably, the main function of the optical waveguide cladding is to achieve optical cladding, enabling the optical signal to propagate through total internal reflection within the waveguide core, while simultaneously isolating it from external environmental influences, reducing scattering loss, and improving the stability of the optical waveguide.

[0153] In practice, the material of the optical waveguide core layer can be silicon dioxide, which can be silicon dioxide doped with germanium, phosphorus, or boron to adjust its refractive index.

[0154] S504. A cover plate is bonded to the optical waveguide cladding to form a beam splitter chip.

[0155] In this step, a cover plate can be bonded to the optical waveguide cladding using methods such as thermosetting bonding, UV-curing adhesive, or molecular bonding to encapsulate the entire structure. It is understood that the cover plate not only provides mechanical protection but also improves the chip's thermal stability and environmental isolation, thereby forming a complete planar beam splitter chip.

[0156] Furthermore, in one possible implementation, after the cover plate is bonded, the splitter chip is sequentially cut and polished to make the inclination angle of the input end -8° and the inclination angle of the output end +8°, ​​so as to reflect the echo, improve the fiber coupling efficiency, and reduce the interference between multiple optical paths.

[0157] The method for fabricating the beam splitter chip provided in this embodiment can produce any beam splitter chip provided in the first aspect of this application through processes such as deposition and etching. The beam splitter chip has strong channel expansion capability.

[0158] Optionally, in one possible implementation, before depositing the optical waveguide material layer on the substrate, the method further includes:

[0159] The width of the optical waveguide core layer is determined based on the spacing between two adjacent final output waveguides.

[0160] Based on the fundamental mode transmission constraint and the aspect ratio constraint of the optical waveguide core layer, the height of the optical waveguide core layer is determined according to the desired operating wavelength, the refractive index deviation of the beam splitter chip, and the width of the optical waveguide core layer; the refractive index deviation is the difference between the refractive index of the optical waveguide core layer and the refractive index of the optical waveguide cladding; the height of the optical waveguide core layer is inversely proportional to the refractive index deviation of the beam splitter chip.

[0161] For details on the specific implementation process and principles of each step, please refer to the descriptions in the previous embodiments, which will not be repeated here.

[0162] Furthermore, this application also provides an optical device, which includes the beam splitter chip described in any of the first aspects of this application.

[0163] Specifically, the optical device may be a magnetometer, an optical imaging system, a fiber optic sensing system, etc., but in this embodiment, it is not limited to any particular type.

[0164] Optional, Figure 6 This is a schematic diagram of an optical device illustrating an exemplary embodiment of this application. Please refer to... Figure 6 In one possible implementation, the optical device is a spin-exchange-relaxed free SERF magnetometer; the optical device also includes a laser and a probe array;

[0165] The laser is coupled to the input waveguide of the primary beam splitter;

[0166] Each probe in the probe array is coupled to a final output waveguide in the output waveguide assembly via an optical fiber.

[0167] Specifically, in one possible implementation, the laser is a distributed feedback DFB (DFB) laser with a center wavelength of 795 nm, used to generate a single optical signal.

[0168] Furthermore, the laser's output is coupled to the input waveguide of the primary beam splitter via optical fiber, allowing a single optical signal to be introduced into the beam splitter chip. The beam splitter chip then performs multi-channel power distribution on the single optical signal. For example, the single optical signal can be split into 256 output optical signals.

[0169] Furthermore, each probe is coupled to a final output waveguide of the beam splitter chip via an optical fiber, which is used to receive the split optical signal and illuminate the detection cavity.

[0170] During operation, the 795 nm laser is distributed to each probe via a beam splitter chip at equal power for optical pumping and detection of the rubidium atom gas cell. When an external magnetic field is applied to the atom gas cell, the spin polarization state of the atoms changes, and the magnetic field strength signal is obtained through optical detection, achieving highly sensitive vector magnetic field measurement.

[0171] The optical device provided in this embodiment provides optical signals to the probe array through a beam splitter chip, which can easily expand the number of channels of the beam splitter chip, thereby expanding the number of probe arrays and improving the spatial resolution of imaging.

[0172] It should be noted that the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0173] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0174] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A beam splitter chip, characterized in that, The beam splitter chip includes a substrate, an optical waveguide core layer, an optical waveguide cladding layer, and a cover plate sequentially disposed on the substrate; The optical waveguide core layer includes a first beam splitting structure, a beam splitting component, and an output waveguide component connected in sequence; the beam splitting component includes at least one beam splitting array; each beam splitting array includes multiple sub-beam splitting structures; along the direction of light transmission, any one of the first beam splitting structure and the sub-beam splitting structures includes an input waveguide, a multimode interference waveguide, and multiple output waveguides; Each output waveguide of the first beam splitting structure is coupled to the input waveguide of a sub-beam splitting structure in the first column of the beam splitting assembly via a transition waveguide; each output waveguide of each sub-beam splitting structure in each column of the beam splitting assembly is coupled to the input waveguide of a sub-beam splitting structure in the next column of the beam splitting array following that column via a transition waveguide. The output waveguide assembly includes multiple final output waveguides; each output waveguide of each sub-splitter in the last column of the beam splitter array is coupled to one of the final output waveguides in the output waveguide assembly.

2. The beam splitter chip according to claim 1, characterized in that, The input waveguide includes a straight input waveguide and a tapered input waveguide that are coupled to each other; each output waveguide includes a tapered output waveguide and a straight output waveguide that are coupled to each other. Both the direct input waveguide and the direct output waveguide are rectangular structures; The tapered input waveguide is a trapezoidal structure including a first input end and a first output end; the width of the first input end is smaller than the width of the first output end; The tapered output waveguide is a trapezoidal structure including a second input terminal and a second output terminal; the width of the second input terminal is greater than the width of the second output terminal.

3. The beam splitter chip according to claim 2, characterized in that, The beam splitting component includes a beam splitting array; each beam splitting structure includes 2 to 16 output waveguides. The height of the optical waveguide core layer is 0.2~5μm; The length of the direct input waveguide is 200~2000μm; The tapered input waveguide has an isosceles trapezoidal structure; the length of the tapered input waveguide is 50~1000μm; the width of the first input end is the same as the width of the straight input waveguide, and the width of the first output end is 5~20μm; The multimode interference waveguide has a rectangular structure; the length of the multimode interference waveguide is 200~8000μm, and the width of the multimode interference waveguide is 20~300μm. The tapered output waveguide has an isosceles trapezoidal structure; the length of the tapered output waveguide is 50~1000μm; the width of the second input end is 3~20μm; the width of the second output end is the same as the width of the straight output waveguide; The length of the direct output waveguide is 1~200μm; The widths of both the direct input waveguide and the direct output waveguide are equal to the height of the optical waveguide core layer.

4. The beam splitter chip according to claim 3, characterized in that, Each of the beam splitting structures includes 8 output waveguides; The length of the tapered input waveguide is 500~600μm, and the width of the first output end is 9~10μm; The length of the multimode interference waveguide is 3000~5000μm, and the width of the multimode interference waveguide is 100~130μm; The tapered output waveguide has a length of 300~450μm, and the width of the second input end is 5~8μm.

5. The beam splitter chip according to claim 3 or 4, characterized in that, The dimensional parameters of the optical waveguide core layer are determined according to the following method: The width of the optical waveguide core layer is determined based on the spacing between two adjacent final output waveguides; Based on the fundamental mode transmission constraint and the aspect ratio constraint of the optical waveguide core layer, the height of the optical waveguide core layer is determined according to the desired operating wavelength, the refractive index deviation of the beam splitter chip, and the width of the optical waveguide core layer; the refractive index deviation is the difference between the refractive index of the optical waveguide core layer and the refractive index of the optical waveguide cladding; the height of the optical waveguide core layer is inversely proportional to the refractive index deviation of the beam splitter chip.

6. The beam splitter chip according to claim 5, characterized in that, The width of each of the tapered output waveguides satisfies the following linear gradient function: Wx = W0 + (W1 - W0) (a / L); Wherein, W0 is the width of the second input terminal, W1 is the width of the second output terminal, L is the length of the tapered output waveguide, and a is a preset value; The W0, W1, L, and the spacing between two adjacent tapered output waveguides are all optimized and determined using the beam propagation method based on the desired operating wavelength and the refractive index of the optical waveguide core layer.

7. A method for fabricating a beam splitter chip, characterized in that, The preparation method is used to prepare the beam splitter chip according to any one of claims 1 to 6; the preparation method includes: An optical waveguide material layer is deposited on a substrate, and a pattern identical to that of the optical waveguide core layer to be prepared is formed on the optical waveguide material layer. The optical waveguide material layer is etched to form an optical waveguide core layer on the substrate; An optical waveguide cladding is deposited on the optical waveguide core layer; A cover plate is bonded to the optical waveguide cladding to form a beam splitter chip.

8. The method according to claim 7, characterized in that, Before depositing the optical waveguide material layer on the substrate, the method further includes: The width of the optical waveguide core layer is determined based on the spacing between two adjacent final output waveguides; Based on the fundamental mode transmission constraint and the aspect ratio constraint of the optical waveguide core layer, the height of the optical waveguide core layer is determined according to the desired operating wavelength, the refractive index deviation of the beam splitter chip, and the width of the optical waveguide core layer; the refractive index deviation is the difference between the refractive index of the optical waveguide core layer and the refractive index of the optical waveguide cladding; the height of the optical waveguide core layer is inversely proportional to the refractive index deviation of the beam splitter chip.

9. An optical device, characterized in that, The optical device includes the beam splitter chip according to any one of claims 1 to 6.

10. The optical device according to claim 9, characterized in that, The optical device is a spin-exchange-relaxed free SERF magnetometer; the optical device also includes a laser and a probe array; The laser is coupled to the input waveguide of the primary beam splitter; Each probe in the probe array is coupled to a final output waveguide in the output waveguide assembly via an optical fiber.

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