Polarization-insensitive large-bandwidth 3dB power divider

Abstract

The invention relates to a polarization-insensitive large-bandwidth 3dB power divider, which comprises a first input waveguide and a second input waveguide, and is characterized in that the first input waveguide and the second input waveguide are of conical gradual change structures; the multi-mode interference waveguide is of a conical gradual change structure, the width of an input port of the multi-mode interference waveguide is larger than that of an output port of the multi-mode interference waveguide, and the input port of the multi-mode interference waveguide is connected with output ports of the first input waveguide and the second input waveguide; input ports of the first output waveguide and the second output waveguide are connected with an output port of the multi-mode interference waveguide, and the first output waveguide and the second output waveguide are both of a conical gradual change structure. At least the self-imaging distance of multimode interference can be shortened, so that the occupied area of the device is smaller.

Description

Technical Field

[0001] The present disclosure relates to the technical field of optical power distributors, and in particular to an alignment pattern and a preparation method thereof, a semiconductor device, a memory, and an electronic device. Background Art

[0002] Optical power dividers, also known as power splitters, play a vital role in modern optical communication systems. Their core function is to evenly distribute the optical power from a single input to multiple outputs, thereby achieving efficient optical signal transmission. These devices are widely used in data centers, communication networks, and various photonic integrated circuits (PICs) to effectively manage the distribution and transmission of optical signals. With the increase in data center demand and the complexity of communication systems, the development of power dividers with high performance and efficiency has become the key to technological progress.

[0003] The structures of optical power beam splitters include Y-type power beam splitters, multimode interference (MMI) type power beam splitters, and DC type power beam splitters. Compared with directional couplers and Y branches, multimode interference couplers have the advantages of simple and compact structure, good tolerance of manufacturing process, and low insertion loss, and are widely used in photonic integrated chips.

[0004] As early as 1836, Tabolt proposed the self-mirror phenomenon. In 1995, Lucas B. Soldano explained the splitting principle of multimode interference couplers based on guided mode analysis and gave a theoretical model, which laid the foundation for subsequent research. Since then, multimode interference couplers have been often used to design optical beam splitters / combiners, among which 3 dB power dividers are the most common. The power divider designed based on multimode interference couplers has very low additional loss characteristics and can ensure good splitting uniformity. Subwavelength gratings have the advantages of controllable structural refractive index and can effectively suppress reflection and diffraction effects. Introducing subwavelength structures into multimode interference couplers can improve the bandwidth characteristics of multimode interference couplers.

[0005] The 3 dB power divider in the related technology still has obvious disadvantages. The existing 3 dB power divider is a polarization-sensitive device and is only effective for the TE mode. In addition, the length of the existing 3 dB power divider exceeds 45 um, which is not conducive to the compact design of the overall system. Summary of the invention

[0006] Based on this, it is necessary to provide a polarization-insensitive large-bandwidth 3dB power divider to address the above technical problems. A 3 dB power divider effective for both TE and TM modes is realized by connecting the ports among the first input waveguide, the second input waveguide, the multimode interference waveguide, the first output waveguide and the second output waveguide. By adopting a multimode interference waveguide with a tapered gradient structure, the self-imaging distance of the multimode interference is shortened, so that the device occupies a smaller area.

[0007] In order to achieve the above-mentioned and other purposes, the present disclosure provides a polarization-insensitive large-bandwidth 3dB power splitter, comprising: a first input waveguide and a second input waveguide, both of which are tapered gradient structures;

[0008] A multimode interference waveguide, the multimode interference waveguide is a tapered gradual structure, the width of the input port of the multimode interference waveguide is greater than the width of the output port of the multimode interference waveguide, and the input port of the multimode interference waveguide is connected to the output ports of the first input waveguide and the second input waveguide;

[0009] A first output waveguide and a second output waveguide, input ports of the first output waveguide and the second output waveguide are connected to the output port of the multimode interference waveguide, and both the first output waveguide and the second output waveguide are tapered gradient structures.

[0010] In the polarization-insensitive large-bandwidth 3 dB power divider in the above embodiment, a 3 dB power divider effective for both TE and TM modes is realized by connecting the ports among the first input waveguide, the second input waveguide, the multimode interference waveguide, the first output waveguide, and the second output waveguide. By adopting a multimode interference waveguide with a tapered gradient structure, the self-imaging distance of the multimode interference is shortened, so that the device occupies a smaller area.

[0011] At the same time, the present disclosure also designs a first input waveguide, a second input waveguide, a multimode interference waveguide, a first output waveguide and a second output waveguide with a tapered gradient structure, thereby reducing transmission and coupling losses.

[0012] In one embodiment, a wide bandwidth 3dB power divider includes: a substrate; an upper cladding layer located on the substrate; a silicon nitride thin film layer formed in the upper cladding layer; wherein the silicon nitride thin film layer is used to form a first input waveguide, a second input waveguide, a multimode interference waveguide, a first output waveguide and a second output waveguide.

[0013] In one embodiment, the cross-sectional widths of the first input waveguide and the second input waveguide linearly widen along the transmission direction; wherein the cross-sectional widths of the first output waveguide and the second output waveguide linearly narrow along the transmission direction.

[0014] In one embodiment, the first input waveguide and the second input waveguide are symmetrically arranged along the central axis of the multimode interference waveguide as the symmetry axis; wherein the first output waveguide and the second output waveguide are symmetrically arranged along the central axis of the multimode interference waveguide as the symmetry axis.

[0015] In one embodiment, the first input waveguide, the second input waveguide, the multimode interference waveguide, the first output waveguide and the second output waveguide are all sub-wavelength grating structures.

[0016] In one embodiment, the power divider calculates the additional loss by the following formula:

[0017] ;

[0018] in, is the additional loss of the power divider, is the optical power output from the output waveguide, is the optical power input to the input waveguide.

[0019] In one embodiment, the power divider calculates the non-uniformity by the following formula:

[0020] ;

[0021] in, is the minimum optical power output by the power divider, The maximum optical power output by the power splitter.

[0022] In one embodiment, the positions of the input port and the output port of the multimode interference waveguide are ;in, is the effective width of the fundamental mode / multimode waveguide.

[0023] In one embodiment, the multimode interference waveguide is a paired imaging waveguide, the multimode interference waveguide is not excited when the mode number is a first mode group, and the multimode interference waveguide contributes to imaging in pairs when the mode number is a second mode group.

[0024] In one embodiment, the first double image of the power divider appears at length; where is the beat length of the multimode interference waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 It is a schematic structural diagram of a polarization-insensitive large-bandwidth 3dB power divider provided in one embodiment;

[0027] Figure 2 A schematic structural diagram of another polarization-insensitive, wide-bandwidth 3dB power divider provided in an embodiment;

[0028] Figure 3 A diagram of the simulated light field intensity at 1550 nm provided in an embodiment;

[0029] Figure 4 3dB power divider provided in one embodiment has a transmission spectrum in TE and TM modes;

[0030] Figure 5 A schematic diagram of simulation calculation of additional loss and power non-uniformity in TE and TM modes provided in an embodiment;

[0031] Figure 6 is a schematic structural diagram of a power divider provided in a comparative embodiment;

[0032] Figure 7 It is a schematic structural diagram of a power divider provided in another comparative embodiment.

[0033] Description of reference numerals:

[0034] 101, input waveguide; 102, multimode interference waveguide; 103, output waveguide; Port1, first input waveguide; Port2, second input waveguide; Port3, first output waveguide; Port4, second output waveguide; 201, substrate; 202, upper cladding; 203, silicon nitride thin film layer. DETAILED DESCRIPTION

[0035] 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.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present disclosure. 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.

[0037] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. On the contrary, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types and / or parts, these elements, components, regions, layers, doping types and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, doping type or part from another element, component, region, layer, doping type or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer, doping type or portion discussed below may be represented as a second element, component, region, layer or portion; for example, the first doping type may be referred to as the second doping type, and similarly, the second doping type may be referred to as the first doping type; the first doping type and the second doping type are different doping types, for example, the first doping type may be P-type and the second doping type may be N-type, or the first doping type may be N-type and the second doping type may be P-type.

[0038] 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.

[0039] When used herein, the singular forms "a", "an" and " / the" may also include the 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 features, integers, steps, operations, elements and / or components can be determined, but the presence or addition of one or more other features, integers, steps, operations, elements, components 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.

[0040] Embodiments of the invention are described herein with reference to cross-sectional views which are schematic representations of ideal embodiments (and intermediate structures) of the present disclosure, such that variations in the shapes shown due to, for example, manufacturing techniques and / or tolerances are anticipated. Thus, embodiments of the present disclosure should not be limited to the particular shapes of the regions shown herein, but rather include deviations in shapes due to, for example, manufacturing techniques. For example, an implanted region shown as a rectangle typically has rounded or curved features and / or an implant concentration gradient at its edges rather than a binary change from an implanted region to a non-implanted region. Similarly, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation is performed. Thus, the regions shown in the figures are schematic in nature, their shapes do not represent the actual shape of the region of the device, and do not limit the scope of the present disclosure.

[0041] First of all, please refer to Figure 6 , Figure 6 This is a schematic diagram of the structure of a power divider provided in a comparative embodiment. Figure 6 , ZhenSheng et al. from the Chinese Academy of Sciences optimized the structural parameters of the multimode interference coupler by using the mode matching method, such as Figure 6 As shown in Figure a, a 1×2 3dB power divider was fabricated on a 220 nm standard SOI wafer using a 0.13-μm CMOS process. The size of the entire power divider is about 3.6×11.5μm2, and the additional loss is about 0.06 dB. It can work perfectly in the communication C band, but the device can only be used for TE polarization optical power distribution. In 2013, HaifengZhou et al. designed a series of 1×2 3dB power dividers based on multimode interference couplers. The width of the designed multimode waveguide ranged from 1.1 μm–3.2 μm. The additional loss tested on a standard 220 nm SOI wafer was less than 0.1 dB, and the power imbalance was about 0.2 dB. It can be seen that the power divider designed based on the multimode interference coupler has a very low additional loss characteristic and can ensure good light splitting uniformity.

[0042] Please continue to refer to Figure 6 Subwavelength gratings have the advantages of controllable structural refractive index and can effectively suppress reflection and diffraction effects. Introducing subwavelength structures into multimode interference couplers can improve the bandwidth characteristics of multimode interference couplers. In 2013, A. Maese-Novo et al. proposed a subwavelength multimode interference coupler, such as Figure 6 As shown in Figure b, by reasonably designing the duty cycle of the subwavelength structure and adjusting the wavelength dispersion characteristics of the multimode waveguide, a 2×2 power divider with a bandwidth of 450nm is obtained. The additional loss of the entire device is less than 1 dB, and the device length is reduced by nearly half compared to the multimode interference coupler of conventional waveguide.

[0043] Please continue to refer to Figure 6 In 2016, Professor Lukas Chrostowski's research group at Columbia University designed and verified a power divider based on subwavelength gratings. Figure 6 As shown in Figure c. The SWG structure with two gradient widths in the upper and lower sections achieves the function of equally dividing the input optical field power. The device has excellent performance, with a bandwidth of 130 nm within the range of insertion loss less than 0.5 dB. However, the device still has obvious disadvantages. First, the device is a polarization-sensitive device and is only effective for the TE mode. Second, the length of the device exceeds 45 um, which is not conducive to the compact design of the overall system.

[0044] Please continue to refer to Figure 6 In 2018, Zhenzhao Guo et al. proposed an ultra-compact polarization-independent power divider based on a sub-wavelength grating structure. Figure 6 As shown in Figure d in the figure. The device combines a tapered waveguide structure, and connects the input and output tapered waveguide structures through a SWG structure to split the input light field power equally. The device has excellent performance, a very small size of 2.5 um, a loss of less than 0.05 dB, and an operating bandwidth sufficient to cover the O, E, S, C, L and part of the U band of the communication band, but the manufacturing process of the device is relatively complicated.

[0045] Please refer to Figure 1-Figure 5 The embodiment of the present disclosure provides a polarization-insensitive large-bandwidth 3dB power divider, including: a first input waveguide Port1 and a second input waveguide Port2, both of which are tapered gradient structures; a multimode interference waveguide 102, the multimode interference waveguide 102 is a tapered gradient structure, the width of the input port of the multimode interference waveguide 102 is greater than the width of the output port of the multimode interference waveguide 102, and the input port of the multimode interference waveguide 102 is connected to the output ports of the first input waveguide Port1 and the second input waveguide Port2; a first output waveguide Port3 and a second output waveguide Port4, the input ports of the first output waveguide Port3 and the second output waveguide Port4 are connected to the output port of the multimode interference waveguide 102, and both of the first output waveguide Port3 and the second output waveguide Port4 are tapered gradient structures.

[0046] In the polarization-insensitive large-bandwidth 3 dB power divider in the above embodiment, a 3 dB power divider effective for both TE and TM modes is realized by connecting the first input waveguide Port1, the second input waveguide Port2, the multimode interference waveguide 102, the first output waveguide Port3, and the second output waveguide Port4. By adopting the multimode interference waveguide 102 with a tapered gradient structure, the self-imaging distance of the multimode interference is shortened, so that the device occupies a smaller area.

[0047] Here, the multimode interference coupler (MMI) is used as an optical power divider. Its basic principle is to utilize the multimode interference effect in the optical waveguide so that the input optical signal can achieve self-imaging and power distribution after a certain propagation distance in the waveguide due to the mutual interference of the excited modes of each order. It can realize precise control of the optical signal in different applications.

[0048] In the multimode interference waveguide 102, W em represents the equivalent width of the m-th order mode, W em It can usually be calculated by the equivalent width W of the fundamental mode. e0 For the TE mode, σ=0, and for the TM mode, σ=1.

[0049] The width of each mode in the MMI waveguide can be simplified by We, as shown in the following formula:

[0050] ;

[0051] The width of the waveguide is , the effective refractive index is The central wavelength of the input light is definition is the beat length of the two lowest-order modes (fundamental mode and first-order mode), which can be expressed as: .

[0052] Please refer to Figure 1 Specifically, the cross-sectional widths of the first input waveguide Port1 and the second input waveguide Port2 linearly widen along the transmission direction.

[0053] The cross-sectional widths of the first output waveguide Port3 and the second output waveguide Port4 narrow linearly along the transmission direction.

[0054] Please refer to Figure 1 Specifically, the first input waveguide Port1 and the second input waveguide Port2 are symmetrically arranged along the central axis of the multimode interference waveguide 102 as a symmetry axis;

[0055] Please refer to Figure 1Specifically, the first output waveguide Port3 and the second output waveguide Port4 are symmetrically arranged with the central axis of the multimode interference waveguide 102 as the symmetry axis.

[0056] In one embodiment, the first input waveguide Port1, the second input waveguide Port2, the multimode interference waveguide 102, the first output waveguide Port3 and the second output waveguide Port4 are all sub-wavelength grating structures.

[0057] Please refer to Figure 1 In the design of this scheme, the MMI coupler is a key to the design. First of all, the width of the MMI coupler is an important design parameter. A wide enough waveguide is required to support a sufficient number of modes. However, a wider MMI width corresponds to a longer device length, resulting in a narrower bandwidth. In the design of this scheme, an 8 μm width (W1) is selected at the input port of the MMI. The MMI adopts a paired interference design, so the positions of the input and output ports need to be ,in, is approximately the effective width of the fundamental mode / multimode waveguide. By introducing a uniform and symmetrical input field at , the modes can be selectively excited, so that the modes with modes m = 2, 5, 8, etc. are not excited, and the modes with modes 0, 1, 3, 4, 6, 7, etc. contribute to the imaging in pairs. Therefore, the period length of the self-imaging is reduced by a factor of three, and the first double image appears at the length Lπ / 2.

[0058] Please continue to refer to Figure 1 As an example, by introducing SWG (subwavelength grating) into the traditional multimode interference coupler, by reasonably designing the duty cycle of the subwavelength structure, the wavelength dispersion characteristics of the multimode waveguide are adjusted to improve the bandwidth characteristics of the multimode interference coupler and use the SWG to manipulate the refractive index to adjust the beat length of the TE and TM modes, which can shorten the self-imaging distance of the multimode interference coupler, thereby reducing the device size / reducing the footprint.

[0059] Please continue to refer to Figure 1 As an example, the width of the MMI taper can be adjusted to assist in constructing different effective interference lengths for the TE and TM modes. In the design, the MMI region adopts a positive cone (taper, gradually narrowing) structure, which gradually changes from the 8μm width of the input port (W1) to the 5.3μm output port width (W2). This design further shortens the self-imaging distance of the MMI and provides a more compact structural solution.

[0060] The positions of the input port and the output port of the multimode interference waveguide 102 are: .

[0061] in, is the effective width of the fundamental mode / multimode waveguide.

[0062] The multimode interference waveguide 102 is a paired imaging waveguide. The multimode interference waveguide 102 is not excited when the mode number is a first mode group, and contributes to imaging in pairs when the mode number is a second mode group.

[0063] Among them, the first double image of the power divider appears at the length of Lπ / 2.

[0064] Wherein, Lπ is the beat length of the multimode interference waveguide 102, that is, the beat length of the two lowest-order modes (fundamental mode and first-order mode).

[0065] Here, please refer to Figure 7 , Figure 7 It is a schematic diagram of the structure of the power divider provided in another comparative embodiment. In the prior art, the main method to achieve polarization-insensitive MMI is to balance the coupling lengths of TE and TM modes. By selecting appropriate waveguide width and length, the beat lengths of TE and TM modes are made the same. Another method to balance the coupling length is to use a subwavelength grating (SWG), which has great advantages in refractive index manipulation and polarization control. Through the engineering anisotropy of MMI, the current research realizes polarization-insensitive MMI based on subwavelength grating of SOI platform, and achieves the same effective refractive index difference in the first two TE and TM modes. The specific device structure is as follows: Figure 7 shown.

[0066] Please refer to Figure 2 Specifically, the large bandwidth 3 dB power divider includes: a substrate 201 ; an upper cladding layer 202 located on the substrate 201 ; and a silicon nitride thin film layer 203 formed in the upper cladding layer 202 .

[0067] The silicon nitride film layer 203 is used to form a first input waveguide Port1, a second input waveguide Port2, a multimode interference waveguide 102, a first output waveguide Port3 and a second output waveguide Port4.

[0068] Wherein, the substrate 201 can be made of semiconductor material, insulating material, conductor material or any combination thereof. The substrate 201 can be a single-layer structure or a multi-layer structure. For example, the substrate 201 can be a silicon substrate 201, a silicon germanium substrate 201, a silicon germanium carbon substrate 201, a silicon carbide substrate 201, a gallium arsenide substrate 201, an indium arsenide substrate 201, an indium phosphide substrate 201 or other III / V semiconductor substrates 201 or II / VI semiconductor substrates 201. Alternatively, for example, the substrate 201 can be a layered substrate 201 including silicon / silicon carbide, silicon on insulator or silicon germanium on insulator. Therefore, the type of substrate 201 should not limit the scope of protection of the present disclosure.

[0069] Specifically, the silicon nitride film layer 203 is a 800 nm thick silicon nitride (Si3N4) film.

[0070] As an example, a typical structure size under 800 nm SiN film can be about 8 μm×51.5 μm.

[0071] As an example, the upper cladding layer 202 may be silicon dioxide.

[0072] Here, it should be noted that Si3N4 (Silicon Nitride) benefits from the large refractive index contrast between it and silicon dioxide, so that the optical signal can be well confined in the silicon nitride waveguide for transmission. Silicon nitride thin film waveguides deposited by low-pressure chemical evaporation (LPCVD) have the advantages of low transmission loss and low bending loss, and silicon nitride has a high third-order nonlinear coefficient. Thick silicon nitride waveguides (waveguide thickness greater than 600 nm) further enhance the mode confinement capability and are conducive to dispersion engineering, which can achieve both positive dispersion and anomalous dispersion. This makes the silicon nitride platform an important material for nonlinear optical applications such as supercontinuum generation and Kerr micro-combs.

[0073] Here, compared with the traditional silicon platform, the silicon nitride platform has stronger dispersion control capabilities and higher photonic integration, and is compatible with microelectronic CMOS processes, which makes the miniaturization and large-scale integration of devices possible. At present, silicon nitride photonic integrated circuits have shown broad application prospects in the fields of dense spiral waveguides, nonlinear frequency conversion, and frequency comb generation. With the development of technology, the application of silicon nitride platforms in photonic integrated circuits will be further expanded, providing a solid foundation for the development of advanced photonic functional devices. Therefore, it is of great research significance to explore the optical power distribution technology based on thick Si3N4 films.

[0074] In related technologies, the high refractive index contrast and complementary metal oxide semiconductor compatible properties of silicon nitride materials make it a research focus, but the on-chip SiN platform has a strong polarization correlation. For the same device, optical signals with different polarization modes will have different forms of output, which is not conducive to the application of optical switches and optical communications. It is often necessary to add additional devices (e.g., polarization beam splitters / polarization rotators) to achieve polarization control, thereby achieving polarization-insensitive multimode 3 dB splitting. However, the additional devices increase the complexity and loss of the overall device. Moreover, the polarization characteristics of the on-chip device are inconsistent with the optical fiber with random polarization direction, which causes undesirable fiber chip link problems in various applications such as optical switches and communications. Therefore, designing a good polarization-insensitive 3 dB power splitter is of great value in polarization-related applications. In addition, in order not to affect the working performance of other devices cascaded with the power splitter, the insertion loss, compactness and bandwidth of the power splitter need to be further improved and optimized.

[0075] In summary, multimode interference couplers based on subwavelength grating structures have only been verified on thin film platforms such as SOI and 300 nm SiN. There is currently little research on MMI devices that introduce SWG structures in 800 nm thick silicon nitride films; and the polarization characteristics of the 3 dB power divider on the thick silicon nitride platform have not yet been verified; the bandwidth, compactness and insertion loss of the power divider need to be further improved and optimized.

[0076] Moreover, from a structural point of view, the device can be prepared by a one-step etching process, which is simple and easy to expand.

[0077] Specifically, the power divider calculates the additional loss by the following formula:

[0078] ;

[0079] in, is the additional loss of the power divider, is the optical power output from the output waveguide, is the optical power input to the input waveguide.

[0080] Specifically, the power divider calculates the unevenness by the following formula:

[0081] ;

[0082] in, is the minimum optical power output by the power divider, The maximum optical power output by the power splitter.

[0083] As an example, see Figure 3-Figure 6 , please refer to Figure 3 , Figure 3FIG. 1 is a diagram of the simulated light field intensity at 1550 nm provided in an embodiment. Figure 3 As shown in Figure a, Figure 3 Figure a in the figure is the simulated light field intensity diagram of TE of MMI in the 1550 nm band. Figure 3 As shown in Figure b, Figure 3 Figure b is a simulated optical field intensity diagram of TM of MMI in the 1550 nm band. The large-bandwidth 3dB power divider proposed in this application can well realize the polarization-insensitive (TE / TM) characteristics within a large bandwidth range (1400 nm-1750 nm), which is conducive to supporting large-bandwidth communications.

[0084] As an example, see Figure 4 , Figure 4 The transmission spectrum of the 3dB power divider in TE and TM modes provided in one embodiment is as follows: Figure 4 As shown in Figure 4 The transmission spectrum (Transmission Spectrum) of the 3db power divider proposed in this application is shown, and the transmission characteristics in different wavelength ranges. Specifically, the transmission intensity of the TE mode (transverse electric field mode) and the TM mode (transverse magnetic field mode) at two different ports (Port 3 and Port 4) is in decibels (dB). Among them, the horizontal axis represents the wavelength range (1400 nm to 1700 nm), and the vertical axis represents the transmission intensity (Transmission) in dB.

[0085] Specifically, Figure 4 The different curves represent the transmission conditions of the TE mode and the TM mode on Port 3 and Port 4 respectively. By observing the curves, it can be seen that the transmission spectrum does not change much in the entire wavelength range, indicating that the power divider proposed in this application has relatively stable transmission characteristics and low loss in a wider wavelength range.

[0086] As an example, see Figure 5 , Figure 5 FIG. 1 is a schematic diagram of simulation calculation of additional loss and power non-uniformity in TE and TM modes provided in an embodiment, wherein: Figure 5 Figure a is a schematic diagram of the simulation calculation of additional losses in TE and TM modes. Figure 5 Figure b is a schematic diagram of the simulation calculation of power non-uniformity in TE and TM modes. Figure 5As shown in Figure a, the power divider proposed in this application has a wavelength range from 1400 nm to 1800 nm. The loss of the TE mode remains low and relatively stable in most wavelength ranges, about 0.5 dB, and only slightly increases when the wavelength exceeds 1750 nm. The loss of the TM mode first decreases and then slowly increases in the range of 1400 nm to 1600 nm, and is generally lower than that of the TE mode, especially reaching the lowest point near the wavelength of 1550 nm. Figure 5 As shown in Figure a, the power divider proposed in this application has low loss in the range of 1400 nm to 1750 nm. Please continue to refer to Figure 5 , Figure 5 As shown in Figure b, the power divider proposed in this application has a power imbalance between 0.5db-1.5db in the TE mode and between 0db-1db in the TM mode within the range of 1400 nm to 1800 nm, which is relatively stable.

[0087] The present application proposes a polarization-insensitive, large-bandwidth 3 dB power divider, which realizes a 3 dB power divider effective for both TE and TM modes by connecting the first input waveguide Port1, the second input waveguide Port2, the multimode interference waveguide 102, the first output waveguide Port3, and the second output waveguide Port4. By adopting the multimode interference waveguide 102 with a tapered gradient structure, the self-imaging distance of the multimode interference is shortened, so that the device occupies a smaller area.

[0088] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features of the above 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.

[0089] The above embodiments only express several implementation methods of the present disclosure, 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 disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure shall be subject to the attached claims.

Claims

1. A polarization-insensitive, wide-bandwidth 3dB power divider, characterized in that: include: A first input waveguide and a second input waveguide, wherein the first input waveguide and the second input waveguide are both tapered gradual structures; A multimode interference waveguide, wherein the multimode interference waveguide is a tapered gradual structure, the width of the input port of the multimode interference waveguide is greater than the width of the output port of the multimode interference waveguide, and the input port of the multimode interference waveguide is connected to the output ports of the first input waveguide and the second input waveguide; A first output waveguide and a second output waveguide, wherein input ports of the first output waveguide and the second output waveguide are connected to the output port of the multimode interference waveguide, and both the first output waveguide and the second output waveguide are tapered gradient structures.

2. The power divider according to claim 1, characterized in that: The large bandwidth 3dB power divider comprises: substrate; an upper cladding layer, located on the substrate; A silicon nitride thin film layer is formed in the upper cladding layer; The silicon nitride thin film layer is used to form a first input waveguide, a second input waveguide, a multimode interference waveguide, a first output waveguide and a second output waveguide.

3. The power divider according to claim 1, characterized in that: The cross-sectional widths of the first input waveguide and the second input waveguide widen linearly along the transmission direction; The cross-sectional widths of the first output waveguide and the second output waveguide narrow linearly along the transmission direction.

4. The power divider according to claim 1, characterized in that: The first input waveguide and the second input waveguide are symmetrically arranged with the central axis of the multimode interference waveguide as the symmetry axis; The first output waveguide and the second output waveguide are symmetrically arranged with the central axis of the multimode interference waveguide as the symmetry axis.

5. The power divider according to claim 1, characterized in that: The first input waveguide, the second input waveguide, the multimode interference waveguide, the first output waveguide and the second output waveguide are all sub-wavelength grating structures.

6. The power divider according to claim 1, characterized in that: The power divider calculates the additional loss by the following formula: ； in, is the additional loss of the power divider, is the optical power output from the output waveguide, is the optical power input to the input waveguide.

7. The power divider according to claim 1, characterized in that: The power divider calculates the unevenness by the following formula: ； in, is the minimum optical power output by the power divider, The maximum optical power output by the power splitter.

8. The power divider according to claim 1, characterized in that: The positions of the input port and the output port of the multimode interference waveguide are ; in, is the effective width of the fundamental mode / multimode waveguide.

9. The power divider according to claim 1, characterized in that: The multimode interference waveguide is a paired imaging waveguide. The multimode interference waveguide is not excited when the mode number is a first mode group, and contributes to imaging in pairs when the mode number is a second mode group.

10. The power divider according to claim 1, characterized in that: The first double image of the power divider appears in length; in, is the beat length of the multimode interference waveguide.

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