CN115980926A - A Hybrid Integrated Multimode Waveguide Coupler - Google Patents

Abstract

The invention discloses a hybrid integrated multimode waveguide coupler, which belongs to the field of optoelectronic communication devices. The coupler includes a mode multiplexing three-dimensional integrated waveguide, a mode demultiplexer and a single-mode array connector, and is used to realize the coupling conversion of multiple modes in the multimode waveguide and the few-mode fiber. Among them, the mode demultiplexer can convert the high-order mode in the multimode waveguide into the fundamental mode of different channels, and further couple to the mode multiplexing three-dimensional integrated waveguide through the single-mode array connector, and finally use the mode multiplexing three-dimensional integrated waveguide to convert the fundamental mode multiplexed into the corresponding modes in the few-mode fiber. The hybrid integrated multimode waveguide coupler can realize the coupling conversion of multiple modes between the multimode waveguide and the few-mode fiber. It has the characteristics of compatible polarization multiplexing, simple process and high coupling efficiency, and meets the needs of multimode optical fiber communication and on-chip communication. actual needs in other fields.

Description

A Hybrid Integrated Multimode Waveguide Coupler

technical field

The invention belongs to the field of optical interconnection communication, and more specifically relates to a hybrid integrated multimode waveguide coupler.

Background technique

Advanced multiplexing technology can transmit multiple signals at the same time, which is of great significance to meet the growing demand for large-capacity optical interconnection. The optical field has multiple physical dimension resources, which can be used to implement various multiplexing technologies, demonstrating the feasibility of ultra-large capacity in optical communication, such as wavelength division multiplexing (WDM) using the wavelength dimension, and using the time dimension Time Division Multiplexing (TDM), Polarization Division Multiplexing (PDM) using the polarization dimension, advanced modulation formats using the amplitude and phase dimensions, etc. In the past few decades, the above multiplexing technologies have achieved rapid development, which has continuously promoted the improvement of the transmission capacity of optical communication networks. However, the existing light field dimension resources will also face the problem that the development and utilization are close to the limit. At the same time, in order to solve the predicted "capacity bottleneck" in single-mode optical fiber communication networks, mode division multiplexing (MDM) utilizes different spatially orthogonal modes in multimode waveguides/fibers to simultaneously transmit different signals, which greatly improves the performance of optical communication systems. capacity.

For optical fiber-based optical communication networks, mode division multiplexing technology has become an effective way to further improve the transmission capacity of optical fiber communication. Hybrid combinations of single-mode multi-core fibers (MCF), multi-mode fibers (MMF) and their few-mode multi-core fibers (FM-MCF) have demonstrated ultra-high capacity data transmission. Among them, because few-mode fibers (FMF) can avoid the difficulty of controlling high-order modes in traditional multimode fibers (MMF), the weakly coupled MDM technology based on few-mode fibers has attracted extensive attention. Furthermore, by introducing the dimension of spatial mode parallelism into silicon photonic integrated circuits (PICs), mode-division multiplexing can significantly expand the communication density of on-chip interconnects and also has great potential in multimode optical communications. For the on-chip mode division multiplexing system, the integrated mode (de)multiplexer is the key device to realize the efficient conversion, excitation and (de)multiplexing of the guided mode. Silicon photonics is considered one of the best integrated photonic platforms due to its unique advantages such as strong light confinement, small size and mature complementary metal-oxide-semiconductor (CMOS) compatible technology. Current silicon-based mode (de)multiplexers can also be fabricated by mature fabrication techniques, such as adiabatic couplers, asymmetric Y-junctions, asymmetric directional couplers (ADCs), and reverse-engineered photonic chips. Although there has been a lot of work on chip-level or fiber-based MDM technologies, due to the size and shape mismatch between multimode waveguides and few-mode fiber modes, efficient multimode couplers serve as the link between on-chip multimode waveguides and few-mode Fiber-optic bridges remain a challenging task.

In order to overcome the above challenges, some integrated schemes for coupling multimode waveguides and few-mode fibers have been proposed, which can be divided into vertical coupling schemes and end-face coupling schemes. For vertical coupling schemes, a 2D grating coupler is a common device because of its large process tolerance and small footprint. However, special defects of gratings, namely limited bandwidth and large insertion loss, greatly limit the application of 2D grating couplers. In contrast, the end-face coupling scheme theoretically has wider operating bandwidth, lower coupling loss and more compact packaging. It is reported that the three-pointed inverted cone structure with 1 × 3 splitter can achieve high-efficiency four-mode coupling with a large operating bandwidth range, however, the number of coupled modes is theoretically difficult to increase. In addition, the multilevel inverted tapered coupler based on heterogeneous waveguides can realize the direct coupling of six guided modes, but its wavelength sensitivity hinders its further application.

Contents of the invention

Aiming at the defects of the prior art, the object of the present invention is to provide a hybrid integrated multimode waveguide coupler, aiming at solving the coupling problem of multimode waveguide and few-mode fiber, using mode multiplexing three-dimensional integrated waveguide, for multimode Optical communication is of great significance.

To achieve the above object, the present invention provides a hybrid integrated multimode waveguide coupler, including sequentially connected mode demultiplexer, single-mode array connector and mode multiplexing three-dimensional integrated waveguide, used to realize multimode waveguide and Coupling conversion of multiple modes in few-mode fibers. One end of the mode demultiplexer is connected to the multi-mode silicon-based waveguide, which can convert the high-order modes in the multi-mode waveguide into the fundamental modes of different channels, and further couple to the mode-multiplexed three-dimensional integrated waveguide through the single-mode array connector, and finally use the mode The output port of the multiplexing three-dimensional integrated waveguide is connected to the few-mode fiber, and the fundamental mode is multiplexed into the corresponding mode in the few-mode fiber.

Preferably, the mode-multiplexing three-dimensional integrated waveguide adopts femtosecond laser direct writing technology, and is processed on transparent material chips such as glass, crystal, and optical ceramics to realize mode multiplexing and couple the modes into few-mode fibers.

Further, the mode demultiplexer can adopt an asymmetric Y branch structure, a reverse design structure or an asymmetric directional coupling structure, which is used to demultiplex multiple modes in the multimode waveguide into fundamental modes of different channels. Preferably, the asymmetric directional coupling structure includes a multi-mode coupling waveguide, a single-mode coupling waveguide, an input multi-mode straight waveguide, an output multi-mode straight waveguide, a single-mode input curved waveguide and a single-mode output s-shaped waveguide; a single-mode input curved waveguide, The multi-mode coupling waveguide and the single-mode output s-shaped waveguide are connected in sequence, the input multi-mode straight waveguide, the single-mode coupling waveguide and the output multi-mode straight waveguide are connected in sequence, and connected with the single-mode input curved waveguide, the multi-mode coupling waveguide and the single-mode output s Type waveguides maintain a preset spacing.

Furthermore, the single-mode array connector can adopt a strip waveguide inverted cone structure or a slot waveguide inverted cone structure, which can realize efficient coupling of the transverse electric fundamental mode and the transverse magnetic fundamental mode.

Furthermore, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-independent, the multimode waveguide coupler can realize the same-order mode coupling conversion of arbitrary polarization in the multimode waveguide and few-mode fiber.

Furthermore, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-dependent, the multimode waveguide coupler can realize the coupling conversion corresponding to different modes of different polarizations in the multimode waveguide and the few-mode fiber.

Furthermore, the mode-multiplexed three-dimensional integrated waveguide includes a single-mode input waveguide, a three-dimensional transition region coupling waveguide and a few-mode output waveguide. First, the single-mode tapered input waveguide is a tapered waveguide, which is arranged in a linear and equidistant manner, and then slowly transformed into a triangular arrangement, and then the power is coupled and distributed through the coupling waveguide in the three-dimensional transition region by means of adiabatic and slow change, and finally multiplexed into Different modes in a few-mode fiber and coupled into the few-mode fiber.

Further, the mode demultiplexing device can be processed on a silicon platform, the thickness of the silicon waveguide of the polarization-dependent mode demultiplexer is 220nm, and the thickness of the silicon waveguide of the polarization-independent mode demultiplexer is greater than 220nm.

Further, the multimode waveguide coupler can realize the corresponding coupling conversion of 6 or 10 or even more modes in the multimode waveguide and the few-mode fiber, and the 6 modes include TE ₀ , TM ₀ in the multimode waveguide , TE ₁ , TM ₁ , TE ₂ , TM ₂ modes and LP ₀₁ ^x , LP ₀₁ ^y , LP _11a ^x , LP _11a ^y , LP _11b ^x , LP _11b ^y modes in few-mode fibers; the 10 modes described Including TE ₀ , TM ₀ , TE ₁ , TM 1 , TE ₂ , TM ₂ , TE ₃ , TM _{3 ,} TE ₄ , TM ₄ modes in multimode waveguides and LP ₀₁ ^x , LP ₀₁ ^y in few-mode fibers, LP _11a ^x , LP _11a ^y , LP _11b ^x , LP _11b ^y , LP _21a ^x , LP _21a ^y , LP _21b ^x , LP _21b ^y mode.

Through the above technical solutions conceived by the present invention, compared with the prior art, the present invention has the following beneficial effects:

1. A hybrid integrated multimode waveguide coupler proposed by the present invention uses a mode-multiplexed three-dimensional integrated waveguide as a multiplexer for few-mode fiber modes, and the waveguide is processed on glass, crystal or Optical ceramics have low loss, low crosstalk, simple process, low cost, and can be mass-produced; and the existing silicon-based device processing technology is mature. Therefore, the hybrid integrated multimode coupler has high feasibility for factory mass production.

2. Whether the reported multimode waveguide and few-mode fiber couplers adopt the vertical coupling scheme or the end-face coupling scheme, the number of coupled modes is limited, but it is a challenge for multimode couplers with more modes. In contrast, the mode coupling number of the hybrid integrated multimode waveguide coupler proposed by the present invention depends on the mode number of the silicon-based demultiplexer or the mode multiplexing three-dimensional integrated waveguide, which is more than that of the reported multimode coupler number, and the number of mode couplings of the multimode coupler is scalable, which has great significance and many application scenarios for multimode optical communication networks.

Description of drawings

Fig. 1 is a schematic structural diagram of a hybrid integrated multimode waveguide coupler provided by the present invention.

Fig. 2 is a schematic structural diagram of a polarization-independent hybrid integrated multimode waveguide coupler.

Fig. 3 is a schematic structural diagram of a mode demultiplexer.

Fig. 4 is a schematic structural diagram of a polarization-dependent hybrid integrated multimode waveguide coupler.

Fig. 5 is a schematic structural diagram of a single-mode connector.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute conflicts with each other.

The invention provides a hybrid integrated multimode waveguide coupler, which includes sequentially connected mode demultiplexers, single-mode array connectors and mode multiplexed three-dimensional integrated waveguides, which are used to realize multimode waveguides and few-mode optical fibers. Coupling conversion of two modes. One end of the mode demultiplexer is connected to the multi-mode silicon-based waveguide, which can convert the high-order modes in the multi-mode waveguide into the fundamental modes of different channels, and further couple to the mode-multiplexed three-dimensional integrated waveguide through the single-mode array connector, and finally use the mode The output port of the multiplexing three-dimensional integrated waveguide is connected to the few-mode fiber, and the fundamental mode is multiplexed into the corresponding mode in the few-mode fiber.

Specifically, the mode-multiplexing three-dimensional integrated waveguide adopts femtosecond laser direct writing technology, and is processed on transparent material chips such as glass, crystal, and optical ceramics to realize mode multiplexing and couple modes into few-mode fibers.

Specifically, the mode demultiplexer can adopt an asymmetric Y branch structure, an inverse design structure or an asymmetric directional coupling structure, which is used to demultiplex multiple modes in the multimode waveguide into fundamental modes of different channels.

Specifically, the single-mode array connector can adopt a strip waveguide inverted cone structure or a slot waveguide inverted cone structure, which can realize efficient coupling of the transverse electric fundamental mode and the transverse magnetic fundamental mode.

Specifically, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-independent, the multimode waveguide coupler can realize the same-order mode coupling conversion of the multimode waveguide and the arbitrary polarization in the few-mode fiber, and the mode demultiplexing The waveguide thickness of the device is 340nm.

Specifically, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-dependent, the multimode waveguide coupler can realize the coupling conversion corresponding to different modes of different polarizations in the multimode waveguide and the few-mode fiber, and the mode demultiplexer The waveguide thickness of the device is 220nm.

Specifically, the mode-multiplexed three-dimensional integrated waveguide includes a single-mode input waveguide, a three-dimensional transition region coupling waveguide and a few-mode output waveguide. First, the single-mode tapered input waveguide is a tapered waveguide, which is arranged in a linear and equidistant manner, and then slowly transformed into a triangular arrangement, and then the power is coupled and distributed through the coupling waveguide in the three-dimensional transition region by means of adiabatic and slow change, and finally multiplexed into Different modes in a few-mode fiber and coupled into the few-mode fiber.

Specifically, the multimode waveguide coupler can realize the corresponding coupling conversion of 6 or 10 or even more modes in the multimode waveguide and few-mode fiber, and the 6 modes include TE ₀ , TM ₀ in the multimode waveguide , TE ₁ , TM ₁ , TE ₂ , TM ₂ modes and LP ₀₁ ^x , LP ₀₁ ^y , LP _11a ^x , LP _11a ^y , LP _11b ^x , LP _11b ^y modes in few-mode fibers; the 10 modes described Including TE ₀ , TM ₀ , TE ₁ , TM 1 , TE ₂ , TM ₂ , TE ₃ , TM _{3 ,} TE ₄ , TM ₄ modes in multimode waveguides and LP ₀₁ ^x , LP ₀₁ ^y in few-mode fibers, LP _11a ^x , LP _11a ^y , LP _11b ^x , LP _11b ^y , LP _21a ^x , LP _21a ^y , LP _21b ^x , LP _21b ^y mode.

Example

The invention discloses a hybrid integrated multimode waveguide coupler, which belongs to the field of optical calculation. It includes mode demultiplexer I, single-mode array connector II and mode multiplexing three-dimensional integrated waveguide III, as shown in Figure 1. The coupler can solve the problem of size and shape mismatch of multiple modes in the multimode waveguide and few-mode fiber, and can realize coupling conversion of multiple modes in the multimode waveguide and few-mode fiber. The mode demultiplexer I is connected to a multimode silicon-based waveguide at one end, and can convert the high-order mode coupling in the silicon-based multimode waveguide into a single-mode waveguide fundamental mode. Then, it is further coupled to the mode-multiplexing three-dimensional integrated waveguide III through the single-mode array connector II, and finally the fundamental mode is multiplexed into the corresponding mode in the few-mode fiber by using the mode-multiplexing three-dimensional integrated waveguide. Then the single-mode array connector is also located on the silicon-based platform for connecting the single-mode output waveguide of the mode demultiplexer and the single-mode input waveguide of the mode-multiplexed 3D integrated waveguide. Finally, the output port of the mode-multiplexed three-dimensional integrated waveguide is connected to the few-mode fiber, which can realize the function of mode multiplexing, and excite the fundamental mode into the corresponding high-order mode in the few-mode fiber, and couple it to the few-mode fiber.

Specifically, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-independent, the multimode coupling device can realize multimode waveguides (TE ₀ /TM ₀ , TE ₁ /TM ₁ , TE ₂ /TM ₂ ) and The same-order mode coupling conversion of any polarization in a few-mode fiber (LP ₀₁ ^x/y , LP _11a ^x/y , LP _11b ^x/y ) is shown in Fig. 2 . The waveguide thickness of this mode demultiplexer is 340nm. The silicon-based mode multiplexer in the multimode coupler adopts a two-stage biconical asymmetric directional coupler structure, including a tapered multimode coupling waveguide 2, a tapered single-mode coupling waveguide 5, and an input multimode coupling waveguide. Mode straight waveguide 4, output multimode straight waveguide 6, single-mode input curved waveguide 1 and single-mode output s-shaped waveguide 3, as shown in FIG. 3 . The parameters of the biconical asymmetric directional coupler structure corresponding to TE ₂ /TM ₂ are: w ₁ =0.15 μm, w ₂ =0.25 μm, w ₃ =1 μm, w ₄ =0.79 μm, gap=0.2 μm, L= 100 μm; TE ₁ /TM ₁ corresponds to the biconical asymmetrical directional coupler structure parameters: w ₁ = 0.18 μm, w ₂ = 0.28 μm, w ₃ = 0.63 μm, w ₄ = 0.4 μm, gap = 0.2 μm , L=100 μm. The parameters of the polarization-independent mode multiplexing three-dimensional integrated waveguide are: the diameter of all single-mode waveguides is about 9 μm, and the diameter of all multi-mode waveguides is about 15 μm; the diameter of the input port of the tapered single-mode input waveguide is about 5 μm.

Specifically, when the mode demultiplexer and the mode multiplexing three-dimensional integrated waveguide are polarization-dependent, the multimode coupling device can realize multimode waveguides (TE ₀ , TM ₀ , TE ₁ , TM ₁ , TE ₂ , TM ₂ ) and The coupling conversion corresponding to different modes of different polarizations in few-mode fibers (LP ₀₁ ^x , LP ₀₁ ^y , LP _11a ^x , LP _11a ^y , LP _11b ^x , LP _11b ^y ) is shown in Fig. 4 . The silicon-based mode multiplexer in the multimode coupler adopts a four-stage biconical asymmetric directional coupler structure. Among them, the TE ₂ and TM ₂ modes are demultiplexed into two polarized fundamental modes through two cascaded biconical asymmetric directional coupler structures and coupled to two adjacent channels, and the TE ₁ and TM ₁ modes are demultiplexed through another Two cascaded biconical asymmetric directional coupler structures are demultiplexed into two polarized fundamental modes and coupled to two adjacent channels. Finally, the TE ₀ and TM ₀ modes are separated by a polarization beam splitter into two adjacent channels. The polarization-dependent mode multiplexing three-dimensional integrated waveguide is divided into two parts, one part is to realize the function of polarization beam combining, and the fundamental modes of input adjacent different polarizations are combined into a single-mode waveguide through a polarization beam combiner. One part is to realize the mode multiplexing function, multiplex the fundamental mode in multiple channels into multiple modes in the multimode waveguide, and finally couple into the few-mode fiber. The diameter size of the multimode waveguide matches the diameter of the few-mode fiber, which can realize low-loss mode coupling.

Specifically, the single-mode array connector can adopt a strip waveguide inverted cone structure or a slot waveguide inverted cone structure, as shown in Figure 5, where the strip waveguide inverted cone structure includes an input straight waveguide 7 and a tapered waveguide 8, and the narrow waveguide The inverted tapered slot waveguide structure includes an input straight waveguide 9 , an asymmetrical slot waveguide 10 and a symmetrical slot waveguide 11 . The inverted cone structure of the slot waveguide adopted in this embodiment can realize efficient coupling of TE ₀ mode and TM ₀ mode, and reduce the loss of the multimode coupler. The slit width and the waveguide width of the symmetrical slit waveguide 11 are changing, the closer to the coupling boundary, the larger the waveguide slit, the smaller the waveguide width; the asymmetrical slit waveguide 10 is that the waveguide slit remains unchanged, The width variation is used to realize the waveguide docking of the slot waveguide and the strip waveguide, and has the characteristics of low loss, thereby reducing the loss of the multimode coupler.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (10)

1. A mixed-integrated multimode waveguide coupler is characterized in that it comprises a mode demultiplexer (I), a single-mode array connector (II) and a mode multiplexed three-dimensional integrated waveguide (III) connected in sequence for realizing Connection coupling between multimode waveguide and few-mode fiber; the mode demultiplexer (I), one end connected to multimode waveguide, is used to convert the high-order mode coupling in multimode waveguide into fundamental mode; the single-mode array connector (II) used to connect the single-mode output waveguide of the mode demultiplexer (I) and the single-mode input waveguide of the mode multiplexing three-dimensional integrated waveguide (III) to realize the transmission of the fundamental mode; the mode multiplexing three-dimensional integrated waveguide ( Ⅲ), the output port is connected to a few-mode fiber for mode multiplexing, and the fundamental mode is excited into a corresponding high-order mode in the few-mode fiber. 2. A kind of hybrid integrated multimode waveguide coupler according to claim 1, characterized in that, said mode multiplexed three-dimensional integrated waveguide (Ⅲ) adopts femtosecond laser direct writing technology, processed in transparent material, for Modes are implemented to multiplex the fundamental modes of different channels into multiple modes in a few-mode fiber. 3. A kind of hybrid integrated multimode waveguide coupler according to claim 1, characterized in that, said mode demultiplexer (I) adopts asymmetric Y branch structure, reverse design structure or asymmetric directional coupling structure , for demultiplexing multiple modes in a multimode waveguide into fundamental modes for different channels. 4. A hybrid integrated multi-mode waveguide coupler according to claim 1, characterized in that said single-mode array connector (II) adopts a strip waveguide inverted cone structure or a slot waveguide inverted cone structure. 5. a kind of hybrid integrated multimode waveguide coupler according to claim 1, is characterized in that, when described mode demultiplexer (I) and mode multiplexing three-dimensional integrated waveguide (III) are polarization-independent, The multimode waveguide coupler realizes the same-order mode coupling conversion of arbitrary polarization in the multimode waveguide and the few-mode fiber. 6. a kind of hybrid integrated multimode waveguide coupler according to claim 1, is characterized in that, when described mode demultiplexer (I) and mode multiplexing three-dimensional integrated waveguide (III) are polarization dependent, The multimode waveguide coupler realizes coupling conversion corresponding to different modes of different polarizations in the multimode waveguide and the few-mode fiber. 7. A kind of hybrid integrated multimode waveguide coupler according to claim 1 or 2, is characterized in that, described mode multiplexing three-dimensional integrated waveguide (Ⅲ) comprises single-mode input waveguide, three-dimensional transition region coupling waveguide and The few-mode output waveguide; the single-mode input waveguide is arranged at linear intervals, and the coupling waveguide in the three-dimensional transition region adopts adiabatic and slow-changing mode for power coupling and distribution; the port size of the few-mode output waveguide and the few-mode fiber Sizes match. 8. A hybrid integrated multimode waveguide coupler according to claim 1 or 3, characterized in that, said mode demultiplexer (I) is processed on a silicon-based platform, and polarization-dependent mode demultiplexing The thickness of the waveguide of the device is 220nm, the thickness of the silicon waveguide of the polarization-independent mode demultiplexer is greater than 220nm, and the thickness of the waveguide of the polarization-independent mode demultiplexer is 340nm. 9. a kind of hybrid integrated multimode waveguide coupler according to claim 1, is characterized in that, described multimode waveguide coupler is used for realizing the intercept coupling of 6 or 10 in multimode waveguide and few-mode fiber; The 6 modes mentioned include TE ₀ , TM ₀ , TE ₁ , TM ₁ , TE ₂ , TM ₂ modes in multimode waveguides and LP ₀₁ ^x , LP ₀₁ ^y , LP _11a ^x , LP _11a in few-mode fibers ^y , LP _11b ^x , LP _11b ^y mode; said 10 modes include TE ₀ , TM ₀ , TE ₁ , TM 1 , TE ₂ , TM ₂ , TE _{3 ,} TM ₃ , TE ₄ , TM ₄ modes and LP ₀₁ ^x , LP ₀₁ ^y , LP _11a ^x , LP _11a ^y , LP 11b x , LP _11b ^y , LP _21a ^x , ^{LP 21a y , LP 21b x , LP 21b y} _modes ⁱⁿ _few ^- _{mode fibers} ^. 10. A hybrid integrated multimode waveguide coupler according to claim 3, characterized in that the asymmetric directional coupling structure comprises a multimode coupling waveguide (2), a single-mode coupling waveguide (5), an input multi-mode Mode straight waveguide (4), output multi-mode straight waveguide (6), single-mode input curved waveguide (1) and single-mode output S-shaped waveguide (3); single-mode input curved waveguide (1), multi-mode coupling waveguide (2 ) and the single-mode output s-type waveguide (3) are sequentially connected, the input multi-mode straight waveguide (4), the single-mode coupling waveguide (5) and the output multi-mode straight waveguide (6) are sequentially connected, and are connected with the single-mode input curved waveguide ( 1), the multi-mode coupling waveguide (2) and the single-mode output s-type waveguide (3) maintain a preset distance.

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