Hybrid integrated space division multiplexer based on 3D printing

Abstract

The invention relates to the technical field of optical communication devices, in particular to a hybrid integrated space division multiplexer based on 3D printing, which comprises a single-mode array waveguide, a mode multiplexing / demultiplexing device, a 3D printing few-mode waveguide and a multi-core few-mode optical fiber which are connected in sequence, the single-mode array waveguide is used for realizing multi-mode energy coupling between the single-mode array waveguide and a fiber core in the multi-core few-mode optical fiber; the mode multiplexing / demultiplexing device couples energy of a fundamental mode in the single-mode array waveguide to a high-order mode of the 3D printing few-mode waveguide, and the 3D printing few-mode waveguide couples the energy to each fiber core of the multi-core few-mode fiber; and the single-mode array waveguide, the mode multiplexing / demultiplexing device and the 3D printing few-mode waveguide are integrally printed and formed by a 3D two-photon printing technology. The space division multiplexer disclosed by the invention integrates the functions of a mode multiplexer and a space division fan-in and fan-out device, has the characteristics of high integration level, capability of realizing polarization multiplexing, high efficiency and the like, reduces the difficulty of the whole device, and meets the actual requirements in the fields of optoelectronic communication and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of optical communication devices, and more specifically, to a hybrid integrated space division multiplexer based on 3D printing. Background Art

[0002] With the increasing demand for transmission capacity in optical transmission systems, traditional methods of increasing the capacity of optical transmission systems, such as high-order modulation formats, digital coherent reception, polarization multiplexing and other optical transmission technologies, have been used to the fullest extent and are close to the limit. At present, new multiplexing dimensions using modes and cores have begun to be applied one after another. Using these new multiplexing dimensions can break through the capacity limit of single-mode optical fiber and solve the capacity problem of current optical transmission systems. With the development of mode division multiplexing systems and core division multiplexing systems, more dimensional space division multiplexing systems have emerged: few-mode multi-core transmission systems. The medium of this transmission system is mainly few-mode multi-core optical fiber.

[0003] Through the few-mode multi-core multiplexing technology, the multi-core multiplexing technology is combined with the few-mode multiplexing technology. Few-mode multi-core multiplexing mainly relies on few-mode multi-core optical fiber as the transmission medium. There are multiple few-mode cores in the cladding of few-mode multi-core optical fiber, and each core can transmit multiple LP modes (Linear polarization). The advantages of few-mode multi-core optical fiber are very prominent, including: 1. The capacity is equivalent to multiplying the number of cores and the number of modes, and the spectrum efficiency will far exceed the current transmission capacity of single-mode optical fiber. 2. A certain compromise is made between the crosstalk damage and refractive index design difficulty in mode multiplexing in few-mode optical fiber, and the difficulty of optical fiber setting and manufacturing in multi-core optical fiber. While ensuring the increase in transmission capacity, the difficulty of further improving mode multiplexing and core multiplexing is reduced. Under the same spatial channel, the requirements for receiver MIMO-DSP (Multiple Input Multiple Output-Digital Signal Processing) equalization processing can be reduced. When multiple dimensions such as mode multiplexing, core multiplexing, wavelength division multiplexing, and polarization multiplexing are combined, the capacity of traditional optical transmission systems will be further exceeded. Problems with the few-mode multi-core multiplexing system: 1. The compatibility of mode multiplexing devices with 3D printed few-mode waveguides is poor; 2. Mode multiplexing devices and 3D printed few-mode waveguides increase the complexity of space division multiplexing devices. 3. Due to the high complexity of mode multiplexing devices and 3D printed few-mode waveguides and the relatively large size of the devices, the integration and compatibility of the devices will be more difficult. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiency of the prior art optical fiber multiplexer that is not compatible with core multiplexing and mode multiplexing, and to provide a hybrid integrated space division multiplexer based on 3D printing that is compatible with both core multiplexing and mode multiplexing.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] Provided is a hybrid integrated space division multiplexer based on 3D printing, comprising a single-mode array waveguide, a mode multiplexer / demultiplexer, a 3D printed few-mode waveguide and a multi-core few-mode optical fiber connected in sequence, for realizing energy coupling of multiple modes between the single-mode array waveguide and the cores in the multi-core few-mode optical fiber; the mode multiplexer / demultiplexer couples the energy of the fundamental mode in the single-mode array waveguide to the high-order mode of the 3D printed few-mode waveguide, and the 3D printed few-mode waveguide then couples the energy to each core of the multi-core few-mode optical fiber; the single-mode array waveguide, the mode multiplexer / demultiplexer and the 3D printed few-mode waveguide are integrally printed by 3D two-photon printing technology.

[0007] A hybrid integrated space division multiplexer based on 3D printing of the present invention includes a single-mode array waveguide, a mode multiplexer / demultiplexer, and a 3D printed few-mode waveguide connected between the mode multiplexer / demultiplexer and the multi-core few-mode optical fiber, which is used to realize the energy coupling of multiple modes between the core of the multi-core few-mode optical fiber and the single-mode array waveguide. The mode multiplexer / demultiplexer can couple the energy of the fundamental mode to the high-order mode of the 3D printed few-mode waveguide, and then use the 3D printed few-mode waveguide to couple the energy to each core of the multi-core few-mode optical fiber. The single-mode array waveguide, the mode multiplexer / demultiplexer and the 3D printed few-mode waveguide are integrally printed and formed by 3D two-photon printing technology, and have high integration; the space division multiplexer of the present invention integrates the functions of the mode multiplexer and the space division fan-in and fan-out devices, and has the characteristics of high integration, polarization multiplexing and high efficiency, which reduces the difficulty of the overall device and meets the actual needs of optoelectronic communications and other fields.

[0008] Furthermore, the mode multiplexer / demultiplexer comprises a tapered coupler or a sub-wavelength grating waveguide.

[0009] Furthermore, the tapered coupler includes a first tapered waveguide and a second tapered waveguide; energy in the first tapered waveguide can be coupled to the second tapered waveguide to perform mode conversion.

[0010] Further, the length of the first tapered waveguide is smaller than the length of the second tapered waveguide; the diameter of the first tapered waveguide at the larger end is smaller than the diameter of the second tapered waveguide at the larger end, and the diameter of the first tapered waveguide at the smaller end is smaller than the diameter of the second tapered waveguide at the smaller end.

[0011] Furthermore, along the direction of energy propagation, the diameter of the first tapered waveguide gradually decreases from 2um to 4um to 1um to 2um; the diameter of the second tapered waveguide gradually increases from 2um to 5um to 3.5um to 6.5um; the interval between the first tapered waveguide and the second tapered waveguide is 0um to 0.6um; the length of the coupling region between the first tapered waveguide and the second tapered waveguide is 0.2um to 2um.

[0012] Furthermore, the sub-wavelength grating waveguide includes a rectangular waveguide and a sub-wavelength grating etched on the rectangular waveguide.

[0013] Furthermore, the refractive index of the rectangular waveguide is 2-2.5; the duty cycle of the sub-wavelength grating is 0.4-0.6, and the grating period is 0.3um-0.5um; the width of the sub-wavelength grating waveguide is 0.3um-2um, and the height is 0.3um-2um.

[0014] Further, the 3D printed few-mode waveguide is obtained by the following steps:

[0015] Using waveguide mode analysis theory, calculate the number of modes that can be supported in the waveguide and the effective refractive index difference between the modes;

[0016] Determine the core and cladding materials of the optical waveguide, use the fiber waveguide perturbation theory to adjust the processing materials and structural parameters used in the waveguide, and reduce the inter-mode coupling coefficient of the waveguide;

[0017] Based on the mode to be transmitted, the geometric parameters of the free-form surface reflector are optimized through the wavefront matching inverse design algorithm to obtain the final reflective surface profile of the 3D printed few-mode waveguide;

[0018] Finally, the preparation of 3D printed few-mode waveguides was realized based on 3D two-photon printing technology.

[0019] Furthermore, the wavefront matching inverse design algorithm is based on the beam diffraction propagation model, and realizes the optimal design of the phase plane by minimizing the wavefront error of the input and output light fields at a fixed position, so that the light field overlap integral of the input light field when it passes through the free-form surface reflection surface and the output light field propagates to the same position is maximized; after obtaining the corresponding phase plane, the surface fitting phase method is used to obtain the final contour of the reflection surface, that is, the final structural shape of the 3D printed few-mode waveguide.

[0020] Furthermore, the refractive index of the optical waveguide core is 1.3-1.7, and the refractive index of the cladding material is smaller than the refractive index of the optical waveguide core.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The hybrid integrated space division multiplexer based on 3D printing of the present invention integrates the functions of a mode multiplexer and a space division fan-in and fan-out device, has the characteristics of high integration, ability to realize polarization multiplexing and high efficiency, reduces the difficulty of the overall device, and meets the actual needs of optoelectronic communications and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of a hybrid integrated space division multiplexer based on 3D printing;

[0024] Figure 2 This is a schematic diagram of the structure of the tapered coupler from a first viewing angle in the first embodiment;

[0025] Figure 3 It is a schematic structural diagram of the tapered coupler from a second viewing angle in the first embodiment;

[0026] Figure 4 It is an image of the light field energy in the first tapered waveguide in the first embodiment being gradually coupled to the second tapered waveguide through the tapered coupling region;

[0027] Figure 5 Schematic diagram of the structure of the sub-wavelength grating waveguide and 3D printed few-mode waveguide prepared in Example 2;

[0028] Figure 6 This is an image of the light field energy being gradually coupled from the sub-wavelength grating waveguide to the 3D printed few-mode waveguide in Example 2;

[0029] Figure 7 This is a mode field image output from the 3D printed few-mode waveguide in Example 2;

[0030] Figure 8 An image of the optical path of the light reflected by the designed free reflection surface in Example 3;

[0031] Fig. 9 Schematic diagram of the phase and profile of the reflection surface designed in Example 3;

[0032] Fig.10 Schematic diagram of the design process of 3D printed few-mode waveguide in Example 3.

[0033] In the attached drawings: 1. single-mode array waveguide; 2. mode multiplexer / demultiplexer; 21. tapered coupler; 211. first tapered waveguide; 212. second tapered waveguide; 22. subwavelength grating waveguide; 3. 3D printed few-mode waveguide; 4. multi-core few-mode optical fiber. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific implementation methods. The accompanying drawings are only used for exemplary descriptions and are only schematic diagrams, not actual drawings, and cannot be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0035] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] Embodiment 1

[0037] This embodiment is a first embodiment of a hybrid integrated space division multiplexer based on 3D printing. Figure 1 As shown, it includes a single-mode array waveguide 1, a mode multiplexer / demultiplexer 2, a 3D printed few-mode waveguide 3 and a multi-core few-mode optical fiber 4 connected in sequence, which are used to realize energy coupling of multiple modes between the single-mode array waveguide 1 and the cores of the multi-core few-mode optical fiber 4; the mode multiplexer / demultiplexer 2 couples the energy of the fundamental mode in the single-mode array waveguide 1 to the high-order mode of the 3D printed few-mode waveguide 3, and the 3D printed few-mode waveguide 3 then couples the energy to each core of the multi-core few-mode optical fiber 4; the single-mode array waveguide 1, the mode multiplexer / demultiplexer 2 and the 3D printed few-mode waveguide 3 are integrally printed by 3D two-photon printing technology.

[0038] This embodiment proposes a hybrid integrated space division multiplexer based on 3D printing, which integrates the functions of a mode multiplexer and a 3D printed few-mode waveguide. The design of the mode multiplexer / demultiplexer 2 is based on the principle of evanescent wave coupling. When a light wave propagates to an interface in a medium, if the incident angle is greater than the critical angle, the light wave cannot completely penetrate the interface, but will form an attenuated electromagnetic wave near the interface. This wave is called an evanescent wave. The intensity of the evanescent wave decreases rapidly with the increase of the distance from the interface. In a waveguide, when two waveguides are very close, the evanescent wave will couple between the two waveguides. Through proper design, the field of the evanescent wave can be generated in one waveguide and coupled in another waveguide.

[0039] In this embodiment, a structure of a mode multiplexer / demultiplexer 2 is provided. In this embodiment, the waveguide structure of the mode multiplexer / demultiplexer 2 is printed using 3D two-photon printing technology, and an approximately adiabatic cone is introduced in one or two waveguides. If the cross-section of the device changes slowly enough, power transmission will be performed between the waveguides as long as the propagation constant of the mode crosses somewhere along the cone. The advantage of using 3D two-photon printing technology for waveguide printing is that 3D two-photon printing technology is based on nonlinear multiphoton polymerization, and a pulsed laser is used to tightly focus the volume of photosensitive resin. By scanning the laser focus in three-dimensional space, any 3D structure can be created. This direct and powerful 3D structure processing capability enables it to complete tasks that traditional photolithography processing technology cannot or is difficult to complete. Compared with laser-etched waveguides based on glass platforms, 3D printed waveguides can be performed on a variety of materials and substrates, and can be integrated into photonic circuits, thereby achieving compact and efficient designs for a wide range of optical applications. A wider range of material selection allows the creation of waveguides with a wide refractive index contrast. The refractive index of the photoresist material selected is between 1.3-1.7.

[0040] like Figure 2 and Figure 3 As shown, the mode multiplexer / demultiplexer 2 is a tapered coupler 21, comprising a first tapered waveguide 211 and a second tapered waveguide 212; the energy in the first tapered waveguide 211 can be coupled to the second tapered waveguide 212 for mode conversion.

[0041] The length of the first tapered waveguide 211 is smaller than the length of the second tapered waveguide 212; the diameter of the first tapered waveguide 211 at the larger end is smaller than the diameter of the second tapered waveguide 212; the diameter of the first tapered waveguide 211 at the smaller end is smaller than the diameter of the second tapered waveguide 212. The size of the first tapered waveguide 211 is smaller than the size of the second tapered waveguide 212, and the size of the waveguide changes gradually along the propagation direction, and the energy is gradually coupled to the second tapered waveguide 212 along the slowly changing taper. Figure 4 shown.

[0042] In this embodiment, PDMS with a refractive index of 1.379 is used as a cladding material on the outside of the first tapered waveguide 211 and the second tapered waveguide 212; along the energy propagation direction, the diameter value of the first tapered waveguide 211 gradually decreases from 2um to 4um to 1um to 2um; the diameter value of the second tapered waveguide 212 gradually increases from 2um to 5um to 3.5um to 6.5um; the interval between the first tapered waveguide 211 and the second tapered waveguide 212 is 0um to 0.6um; the length value of the coupling region between the first tapered waveguide 211 and the second tapered waveguide 212 is 0.2um to 2um.

[0043] Embodiment 2

[0044] This embodiment is a second embodiment of a hybrid integrated space division multiplexer based on 3D printing. This embodiment is similar to the first embodiment, except that, in this embodiment, the mode multiplexer / demultiplexer 2 is a sub-wavelength grating waveguide 22. This embodiment uses the waveguide structure of the sub-wavelength grating to regulate the refractive index of the on-chip waveguide. The sub-wavelength grating is a special photonic structure whose periodic structure size is much smaller than the wavelength of the light wave. The design and application of this structure are based on the physical principle of the interaction between light and matter, especially the interaction when the wavelength of light is much larger than the grating period. The "sub-wavelength" feature of the sub-wavelength grating refers to the size of its periodic structure (period Λ) is less than a small part of the wavelength (λ) of the operating light wave. This usually means that the period Λ is much smaller than λ, so that the light wave cannot resolve the periodic structure of the grating, thereby suppressing the diffraction effect. Since the grating period is much smaller than the wavelength of the light wave, the light wave does not see a periodic structure, but an effective uniform medium. This medium has an equivalent refractive index that can be adjusted by designing the grating parameters. By regulating the refractive index of the on-chip waveguide using a sub-wavelength grating structure, the refractive index of the on-chip waveguide can be made close to the refractive index of the 3D printed few-mode waveguide 3, thereby coupling the energy transmitted in the on-chip waveguide to the 3D printed few-mode waveguide 3.

[0045] This embodiment takes the As20S80 rectangular waveguide as an example, whose refractive index is about 2.2, and the refractive index of the material of the 3D printed few-mode waveguide 3 is selected as 1.53. Since the refractive index difference between the rectangular waveguide and the photoresist waveguide is large, this embodiment uses the form of etching a subwavelength grating in the rectangular waveguide to reduce the refractive index of the rectangular waveguide, so as to achieve the phase matching condition between the subwavelength grating waveguide 22 and the 3D printed few-mode waveguide 3. In this embodiment, the refractive index of the rectangular waveguide is 2 to 2.5; the duty cycle of the subwavelength grating is 0.4 to 0.6, and the grating period is 0.3um to 0.5um; the width of the subwavelength grating waveguide 22 is 0.3um to 2um, and the height is 0.3um to 2um. The equivalent refractive index of the waveguide is calculated using the equivalent refractive index formula:

[0046]

[0047] In the formula, n2 is the refractive index of the material of the cladding silica, which is 1.444 in this embodiment, and the equivalent refractive index of the subwavelength grating waveguide 22 is 1.86, so that the core layer of the subwavelength grating waveguide 22 can be equivalent to a material with a uniform refractive index distribution, and the refractive index of the equivalent material is 1.86. Based on FDTD, a two-dimensional model is established, and the cladding material is set to silica, the core material is set to a subwavelength grating equivalent medium, and the material refractive index is 1.86. The estimated effective refractive index of the TE1 mode of the subwavelength grating waveguide 22 can be obtained to be 1.496, which exactly matches the effective refractive index of the TE2 mode in the 3D printed few-mode waveguide 3, meets the phase matching condition, and can achieve mode coupling from the on-chip subwavelength grating waveguide 22 to the 3D printed few-mode waveguide 3.

[0048] like Figure 5 As shown, the light field undergoes the following process in the designed mode multiplexer / demultiplexer 2: A) the light field propagating in the waveguide is modulated by the periodic structure of the sub-wavelength grating; B) at this time, the sub-wavelength grating waveguide 22 can be equivalent to a dielectric waveguide with a uniform refractive index distribution. Since the modulated refractive index is close to that of the 3D printed few-mode waveguide 3, the light field energy is gradually coupled into the 3D printed few-mode waveguide 3; C) the coupled light field energy continues to be transmitted in the waveguide of the 3D printed few-mode waveguide 3 to achieve mode conversion. Figure 6 and Figure 7 , showing the conversion process of the light field coupled from the subwavelength grating waveguide 22 to the waveguide of the 3D printed few-mode waveguide 3 and the final mode field output by the 3D printed few-mode waveguide 3.

[0049] Embodiment 3

[0050] This embodiment is a third embodiment of a hybrid integrated space division multiplexer based on 3D printing. This embodiment is similar to the first embodiment, except that this embodiment provides a design and preparation method for a multi-core fan-in and fan-out.

[0051] In this embodiment, in the 3D printed few-mode waveguide 3, a free-formed curved reflector is used to realize the connection between the high-order mode from the mode multiplexer / demultiplexer 2 to the multi-core few-mode optical fiber 4. Fig.10As shown, the propagation direction of the light beam is changed based on total internal reflection, and the iterative phase plane is precisely manufactured by 3D two-photon printing processing technology. Based on the beam diffraction propagation model, the phase plane is optimized by minimizing the wavefront error of the input and output light fields at a fixed position, so that the light field overlap integral of the input light field after passing through the free-form surface reflection surface and the output light field when propagating to the same position is maximized, thereby improving the coupling efficiency and mode purity. The compactness of the waveguide structure in the 3D printed few-mode waveguide 3 is improved. The smaller size of the waveguide structure can reduce the loss of light during transmission and improve the transmission efficiency of the optical signal. In the design, the refractive index and optical properties of the waveguide core and cladding materials need to be comprehensively considered, and the preparation process is used to select the photoresist material for processing the optical waveguide. The waveguide mode analysis theory is used to analyze the number of modes that can be supported in the optical waveguide and the effective refractive index difference between the modules. The fiber waveguide perturbation theory is used to adjust the processing materials and structural parameters used in the optical waveguide to reduce the inter-mode coupling coefficient of the waveguide. The wavefront matching inverse algorithm is based on a basic idea, that is, when the light field propagates in free space, the forward propagation light field at any point in the space should be consistent with the reverse propagation field from the receiving surface to the same position. Therefore, after setting the input field and output field in the system, the purpose is to add a reasonable phase modulation plane in the system and modify the light field path so that the light field input and output field at each point in the system space are consistent, and the input field is converted into the output field after passing through multiple phase planes. The free-form surface reflector is used to realize the functions of beam propagation direction redirection and beam mode field adaptation. The geometric parameters of the free-form surface reflector are optimized through the wavefront matching inverse design algorithm. Finally, the preparation of 3D printed few-mode waveguide 3 is realized based on 3D two-photon printing technology.

[0052] Specifically, in terms of the 3D printed few-mode waveguide 3 functions, based on femtosecond laser processing, a connecting waveguide from the on-chip waveguide to the multi-core few-mode optical fiber 4 is prepared. This embodiment comprehensively considers the refractive index and optical properties of the waveguide core and cladding materials, and the preparation process to select the photoresist material for processing the optical waveguide. For example, the waveguide core refractive index can be selected to be approximately 1.53, and the cladding refractive index can be selected to be approximately 1.379. The waveguide mode analysis theory is used to calculate the number of modes that can be supported in the waveguide and the effective refractive index difference between modules. Based on the mode to be transmitted, the geometric parameters of the free-form surface reflector are optimized by the wavefront matching inverse design algorithm; wherein the wavefront matching algorithm is based on the beam diffraction propagation model, and the phase plane is optimized by minimizing the wavefront error of the input and output light fields at a fixed position, so that the input light field is maximized when it propagates backward to the same position as the output light field after passing through the free-form surface reflection surface. Fig. 9 As shown, after obtaining the corresponding phase plane, the final reflection surface profile can be obtained by using the surface fitting phase method. Preferably, the optimized reflection surface is close to a perfect parabola.

[0053] The final space division multiplexing device is as follows Figure 1 As shown, the light field transmitted in the single-mode array waveguide 1 composed of 7 single-mode waveguides is coupled to the 3D printed few-mode waveguide 3 by a tapered coupler 21 or a sub-wavelength grating waveguide 22 to achieve mode conversion. The multi-core few-mode optical fiber 4 is a 7-core optical fiber, and the mode field energy emitted by the mode multiplexer / demultiplexer 2 is coupled to the 7-core multi-core few-mode optical fiber 4 through the free reflection curved waveguide of the 3D printed few-mode waveguide 3.

[0054] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features 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.

[0055] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A hybrid integrated space division multiplexer based on 3D printing, characterized in that: The invention comprises a single-mode array waveguide (1), a mode multiplexer / demultiplexer (2), a 3D printed few-mode waveguide (3) and a multi-core few-mode optical fiber (4) which are connected in sequence, and is used to realize energy coupling of multiple modes between the single-mode array waveguide (1) and the fiber cores of the multi-core few-mode optical fiber (4); the mode multiplexer / demultiplexer (2) couples the energy of the fundamental mode in the single-mode array waveguide (1) to the high-order mode of the 3D printed few-mode waveguide (3), and the 3D printed few-mode waveguide (3) then couples the energy to each fiber core of the multi-core few-mode optical fiber (4); the single-mode array waveguide (1), the mode multiplexer / demultiplexer (2) and the 3D printed few-mode waveguide (3) are integrally printed and formed by 3D two-photon printing technology.

2. The hybrid integrated space division multiplexer based on 3D printing according to claim 1, characterized in that: The mode multiplexer / demultiplexer (2) includes a tapered coupler (21) or a sub-wavelength grating waveguide (22).

3. The hybrid integrated space division multiplexer based on 3D printing according to claim 2, characterized in that: The tapered coupler (21) comprises a first tapered waveguide (211) and a second tapered waveguide (212); energy in the first tapered waveguide (211) can be coupled to the second tapered waveguide (212) to perform mode conversion.

4. The hybrid integrated space division multiplexer based on 3D printing according to claim 3, characterized in that: The length of the first tapered waveguide (211) is smaller than the length of the second tapered waveguide (212); the diameter of the larger end of the first tapered waveguide (211) is smaller than the diameter of the larger end of the second tapered waveguide (212); and the diameter of the smaller end of the first tapered waveguide (211) is smaller than the diameter of the smaller end of the second tapered waveguide (212).

5. The hybrid integrated space division multiplexer based on 3D printing according to claim 4, characterized in that: Along the energy propagation direction, the diameter value of the first tapered waveguide (211) gradually decreases from 2um to 4um to 1um to 2um; the diameter value of the second tapered waveguide (212) gradually increases from 2um to 5um to 3.5um to 6.5um; the interval between the first tapered waveguide (211) and the second tapered waveguide (212) is 0um to 0.6um; and the length value of the coupling region between the first tapered waveguide (211) and the second tapered waveguide (212) is 0.2um to 2um.

6. The hybrid integrated space division multiplexer based on 3D printing according to claim 2, characterized in that: The sub-wavelength grating waveguide (22) comprises a rectangular waveguide and a sub-wavelength grating etched on the rectangular waveguide.

7. The hybrid integrated space division multiplexer based on 3D printing according to any one of claims 1 to 6, characterized in that: 。 8. The hybrid integrated space division multiplexer based on 3D printing according to claim 7, characterized in that: The 3D printed few-mode waveguide (3) is obtained by the following steps: Using waveguide mode analysis theory, calculate the number of modes that can be supported in the waveguide and the effective refractive index difference between the modes; Determine the optical waveguide core and cladding materials; Based on the mode to be transmitted, the geometric parameters of the free-form surface reflector are optimized by using a wavefront matching inverse design algorithm to obtain the final reflective surface profile of the 3D printed few-mode waveguide (3); Finally, the preparation of 3D printed few-mode waveguide (3) was realized based on 3D two-photon printing technology.

9. The hybrid integrated space division multiplexer based on 3D printing according to claim 8, characterized in that: The wavefront matching inverse design algorithm is based on a beam diffraction propagation model, and realizes the optimization design of the phase plane by minimizing the wavefront errors of the input and output light fields at fixed positions, so that the light field overlap integral is maximized when the input light field passes through the free-form surface reflection surface and the output light field propagates to the same position; after obtaining the corresponding phase plane, the surface fitting phase method is used to obtain the final reflection surface profile, that is, the final structural shape of the 3D printed few-mode waveguide (3).

10. The hybrid integrated space division multiplexer based on 3D printing according to claim 9, characterized in that: The refractive index of the optical waveguide core is 1.3-1.7, and the refractive index of the cladding material is smaller than the refractive index of the optical waveguide core.

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