A pattern converter

Abstract

The present invention relates to a mode spot converter, comprising a substrate, a lower cladding layer and a covering layer are sequentially arranged on the substrate from bottom to top, a bottom inverted cone waveguide, a first waveguide structure and a second waveguide structure are sequentially arranged on the upper end of the lower cladding from bottom to top, the bottom inverted cone waveguide, the first waveguide structure and the second waveguide structure are located in the covering layer, the bottom inverted cone waveguide and the first cone waveguide of the first waveguide structure form a first light field transition conversion structure, the first inverted cone waveguide of the first waveguide structure and the second cone waveguide of the second waveguide structure form a second light field transition conversion structure, and the second inverted cone waveguide of the second waveguide structure and the covering layer form a mode spot enlargement structure. The present invention adopts the bottom inverted cone waveguide and two groups of double cone waveguide structures to realize the pull-up effect of the light field, reduce the influence of the substrate silicon material on the mode spot shape, and realize the amplification function of the mode spot through the top inverted cone waveguide, thereby improving the coupling efficiency with the standard single-mode optical fiber.

Description

Technical Field

[0001] The invention belongs to the technical field of optical communication, and in particular relates to a mode spot converter. Background Art

[0002] In recent years, the rapid development of cloud services, 5G communications, and high-definition television has put forward great demands on communication speed and capacity. Optical communication adopts the method of loading the transmission signal on the optical carrier and using optical fiber as the medium for transmission. It has the advantages of high bandwidth, high speed and low cost, which has made revolutionary development in the field of communication. Among them, silicon photonics technology is a research hotspot in the field of optical communications. Due to its high refractive index difference, the size of optical devices has been reduced by one or even several orders of magnitude compared with traditional optical devices. In addition, because the silicon photonics process is compatible with the traditional CMOS process, it has brought the advantages of low cost and easy mass production to silicon photonics technology. It is precisely based on these advantages that after nearly two decades of rapid development, silicon photonics technology has established a complete platform for designing, manufacturing, testing and packaging optical transceivers and optical signal processing devices for telecommunications and data center fields.

[0003] However, there are still some problems that need to be solved in silicon photonics technology. One of the important issues is the effective coupling between small-sized silicon photonic chips and optical fibers. Due to the advantage of high refractive index difference, silicon photonic chips can reduce the cross-sectional size of optical waveguides to the order of hundreds of nanometers. Therefore, the spot size of the light field guided by silicon photonic waveguides is much smaller than the spot size of about 10 microns of single-mode optical fiber. The mismatch of the spot size between the two causes huge energy loss when the silicon photonic chip is coupled with the optical fiber, thus affecting the performance of the entire optical communication system. In order to improve the coupling efficiency, a mode spot converter is made at the light entrance of the silicon photonic chip. There are two main types of mode spot converters. One is a grating coupler based on vertical coupling. Although it has the advantages of good coupling alignment tolerance and convenient wafer-level testing, it also has the disadvantages of narrow working wavelength range and large polarization correlation. The other is a mode spot converter based on edge coupling, which has the advantages of wide working wavelength range and polarization insensitivity. The edge-coupled mode converters currently used have a suspended structure and an inverted cone structure. The suspended structure has a high process complexity because it needs to hollow out the bottom of the SiO2 waveguide and the surrounding materials, and the entire waveguide structure is supported only by the SiO2 suspension wall, so the mechanical performance and device reliability will be big problems. As for the inverted cone structure, due to the limited thickness of the BOX isolation layer, when the light spot is large, the substrate will cause deformation of the light spot and leakage loss, and when the light spot is small, the coupling mismatch with the optical fiber spot is large, resulting in large coupling loss. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a pattern spot converter, which can greatly improve the mechanical properties of the pattern spot converter and the reliability of the device.

[0005] The technical solution of the present invention is implemented as follows: The present invention discloses a mode spot converter, including a substrate, on which a lower cladding layer and a covering layer are arranged in sequence from bottom to top, and the upper end of the lower cladding layer is provided with a bottom layer inverted cone waveguide and a first layer waveguide structure in sequence from bottom to top, the bottom layer inverted cone waveguide and the first layer waveguide structure are located in the covering layer, the first layer waveguide structure includes a first layer cone waveguide and a first layer inverted cone waveguide, the first layer cone waveguide is located directly above the bottom layer inverted cone waveguide, the bottom layer inverted cone waveguide and the first layer cone waveguide form a first light field transition conversion structure to realize the pull-up of the light field, after the light field is pulled up, the light is transmitted from the first layer cone waveguide to the first layer inverted cone waveguide, and the mode spot amplification function is realized through the first layer inverted cone waveguide.

[0006] Furthermore, the first-layer conical waveguide and the first-layer inverted conical waveguide are located in the same plane, and the right surface of the first-layer conical waveguide is connected to the left surface of the first-layer inverted conical waveguide; the bottom-layer inverted conical waveguide has a width that gradually decreases from left to right, the first-layer conical waveguide has a width that gradually increases from left to right, and the first-layer inverted conical waveguide has a width that gradually decreases from left to right.

[0007] Furthermore, the first layer of waveguide structure also includes a first layer of straight waveguide, which is located between the first layer of tapered waveguide and the first layer of inverted tapered waveguide, and the first layer of tapered waveguide, the first layer of straight waveguide, and the first layer of inverted tapered waveguide are located in the same plane; the left surface of the first layer of straight waveguide is connected to the right surface of the first layer of tapered waveguide, and the right surface of the first layer of straight waveguide is connected to the left surface of the first layer of inverted tapered waveguide; the bottom layer of inverted tapered waveguide gradually decreases in width from left to right, the first layer of tapered waveguide gradually increases in width from left to right, and the first layer of inverted tapered waveguide gradually decreases in width from left to right.

[0008] Furthermore, the mode spot converter of the present invention also includes a second layer of waveguide structure located in the covering layer, the second layer of waveguide structure includes a second layer of tapered waveguide and a second layer of inverted tapered waveguide, the second layer of tapered waveguide is located directly above the first layer of inverted tapered waveguide, the first layer of inverted tapered waveguide and the second layer of tapered waveguide form a second light field transition conversion structure to achieve further pulling up of the light field, after the light field is further pulled up, the light is transmitted from the second layer of tapered waveguide to the second layer of inverted tapered waveguide; the second layer of inverted tapered waveguide and the covering layer form a mode spot expansion structure; a gap is provided between the lower surface of the second layer of tapered waveguide and the upper surface of the first layer of inverted tapered waveguide.

[0009] Furthermore, the second-layer tapered waveguide and the second-layer inverted tapered waveguide are located in the same plane, and the right surface of the second-layer tapered waveguide is connected to the left surface of the second-layer inverted tapered waveguide; the width of the first-layer inverted tapered waveguide gradually decreases from left to right, the width of the second-layer tapered waveguide gradually increases from left to right, and the width of the second-layer inverted tapered waveguide gradually decreases from left to right.

[0010] Furthermore, the second layer of waveguide structure also includes a second layer of straight waveguide, which is located between the second layer of tapered waveguide and the second layer of inverted tapered waveguide, and the second layer of tapered waveguide, the second layer of straight waveguide, and the second layer of inverted tapered waveguide are located in the same plane; the left surface of the second layer of straight waveguide is connected to the right surface of the second layer of tapered waveguide, and the right surface of the second layer of straight waveguide is connected to the left surface of the second layer of inverted tapered waveguide; the width of the first layer of inverted tapered waveguide gradually decreases from left to right, the width of the second layer of tapered waveguide gradually increases from left to right, and the width of the second layer of inverted tapered waveguide gradually decreases from left to right.

[0011] Furthermore, the lower cladding layer is made of SiO2 material; the cover layer is made of SiO2 material; the substrate is made of SOI wafer Si substrate; the bottom layer inverted cone waveguide is made of Si material, and the first layer waveguide structure is made of SiN material.

[0012] The second waveguide structure is made of SiN material.

[0013] Furthermore, the first layer of inverted tapered waveguide and the covering layer form a mode spot expansion structure; the lower surface of the bottom layer of inverted tapered waveguide is connected to the upper surface of the lower cladding; a gap is provided between the lower surface of the first layer of tapered waveguide and the upper surface of the bottom layer of inverted tapered waveguide; the lower surface of the covering layer is connected to the upper surface of the lower cladding; and the lower surface of the lower cladding is connected to the upper surface of the substrate.

[0014] The present invention has at least the following beneficial effects: the present invention is an effective improvement on the current suspended bridge structure mode spot converter. The bottom inverted cone waveguide and double cone waveguide structure of the present invention realize the pull-up effect of the light field, reduce the influence of the substrate silicon material on the mode spot shape, and realize the amplification function of the mode spot through the inverted cone structure of the top SiN waveguide, and finally improve the coupling efficiency with the standard single-mode optical fiber. The present invention replaces the suspended structure with a gradient laminated inner cladding, which can greatly improve the mechanical properties of the mode spot converter and the reliability of the device. Therefore, the present invention not only has good optical performance, but also has good reliability.

[0015] All the processes in the novel silicon-based large-size pattern spot converter designed by the present invention are fully compatible with the current CMOS process, which can realize large-scale mass production of devices and help promote the widespread application of silicon photonic integrated devices. The present invention has broad application prospects in the research fields of optical fiber communication, military, medical treatment, biology, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic structural diagram of a pattern spot converter provided in Embodiment 1 of the present invention;

[0018] Figure 2 A top view of a bottom inverted tapered waveguide of a pattern spot converter provided in the first embodiment of the present invention;

[0019] Figure 3 A top view of a first-layer waveguide structure of a pattern spot converter provided in Embodiment 1 of the present invention.

[0020] Figure 4 A three-dimensional diagram of a pattern spot converter provided in the second embodiment of the present invention;

[0021] Figure 5 A schematic structural diagram of a pattern spot converter provided in the second embodiment of the present invention;

[0022] Figure 6 A top view of a pattern spot converter provided in the second embodiment of the present invention;

[0023] Figure 7 A top view of the second layer waveguide structure of a pattern spot converter provided in the second embodiment of the present invention.

[0024] In the drawings, 1 is a substrate, 2 is a lower cladding, 3 is a bottom layer inverted tapered waveguide, 4 is a first layer waveguide structure, 41 is a first layer tapered waveguide, 42 is a first layer straight waveguide, 43 is a first layer inverted tapered waveguide, 5 is a second layer waveguide structure, 51 is a second layer tapered waveguide, 52 is a second layer straight waveguide, 53 is a second layer inverted tapered waveguide, and 6 is a covering layer. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Embodiment 1

[0027] See also Figures 1 to 3The embodiment of the present invention provides a pattern spot converter, including a substrate 1, on which a lower cladding layer 2 and a covering layer 6 are sequentially arranged from bottom to top, and the upper end of the lower cladding layer 2 is sequentially arranged from bottom to top with a bottom layer inverted tapered waveguide and a first layer waveguide structure 4, and the bottom layer inverted tapered waveguide and the first layer waveguide structure 4 are located in the covering layer 6. The lower surface of the covering layer 6 is connected to the upper surface of the lower cladding layer 2, and encloses the bottom layer inverted tapered waveguide and the first layer waveguide structure 4. The bottom layer inverted tapered waveguide 3 gradually decreases in width from left to right.

[0028] The first layer waveguide structure 4 of the present invention has two different solutions, and one of them can be selected according to needs.

[0029] One solution of the first layer waveguide structure 4 of the present invention is: the first layer waveguide structure 4 includes a first layer tapered waveguide 41 and a first layer inverted tapered waveguide 43, the first layer tapered waveguide 41 and the first layer inverted tapered waveguide 43 are located in the same plane, and the right surface of the first layer tapered waveguide 41 is connected to the left surface of the first layer inverted tapered waveguide 43; the bottom layer inverted tapered waveguide 3 gradually decreases in width from left to right, the first layer tapered waveguide 41 gradually increases in width from left to right, and the first layer inverted tapered waveguide 43 gradually decreases in width from left to right.

[0030] Another solution of the first layer waveguide structure 4 of the present invention is: the first layer waveguide structure 4 includes a first layer tapered waveguide 41, a first layer straight waveguide 42, and a first layer inverted tapered waveguide 43; the first layer straight waveguide 42 is located between the first layer tapered waveguide 41 and the first layer inverted tapered waveguide 43; the first layer tapered waveguide 41, the first layer straight waveguide 42, and the first layer inverted tapered waveguide 43 are located in the same plane; the left surface of the first layer straight waveguide 42 is connected to the right surface of the first layer tapered waveguide 41, and the right surface of the first layer straight waveguide 42 is connected to the left surface of the first layer inverted tapered waveguide 43; the bottom layer inverted tapered waveguide 3 gradually decreases in width from left to right, the first layer tapered waveguide 41 gradually increases in width from left to right, and the first layer inverted tapered waveguide 43 gradually decreases in width from left to right. The first layer straight waveguide 42 has a constant width from left to right.

[0031] The first-layer conical waveguide 41 is located directly above the bottom-layer inverted conical waveguide 3. The bottom-layer inverted conical waveguide 3 and the first-layer conical waveguide 41 form a first light field transition conversion structure to realize the pull-up of the light field. After the light field is pulled up, the light is transmitted from the first-layer conical waveguide 41 to the first-layer inverted conical waveguide 43, and the mode spot amplification function is realized through the first-layer inverted conical waveguide 43.

[0032] In this embodiment, only the bottom layer inverted tapered waveguide and the first layer waveguide structure 4 are provided. The first layer inverted tapered waveguide 43 of the first layer waveguide structure 4 and the cover layer 6 form a mode spot expansion structure.

[0033] Further, the lower cladding layer 2 is a SiO2BOX layer. The cover layer 6 is a SiO2 cover layer 6; the substrate 1 is a SOI wafer Si substrate 1; the bottom layer inverted cone waveguide is a Si material, the first layer waveguide structure is a SiN material; the second layer waveguide structure is a SiN material. The bottom layer cone waveguide is an inverted cone silicon waveguide. The first layer cone waveguide 41 is a SiN cone waveguide. The first layer straight waveguide 42 is a SiN straight waveguide. The first layer inverted cone waveguide 43 is a SiN inverted cone waveguide.

[0034] Furthermore, the lower surface of the bottom inverted tapered waveguide is connected to the upper surface of the lower cladding 2; a spacing is provided between the lower surface of the first tapered waveguide 41 and the upper surface of the bottom inverted tapered waveguide 3, and the spacing is set as required; the lower surface of the covering layer 6 is connected to the upper surface of the lower cladding 2; the lower surface of the lower cladding 2 is connected to the upper surface of the substrate 1.

[0035] Embodiment 2

[0036] See also Figures 2 to 7 The pattern spot converter of the embodiment of the present invention, based on the embodiment 1, further includes a second waveguide structure 5 located in the cover layer 6. The lower surface of the cover layer 6 is connected to the upper surface of the lower cladding layer 2, and encloses the bottom inverted tapered waveguide, the first waveguide structure 4, and the second waveguide structure 5.

[0037] The second waveguide structure 5 of the present invention has two different solutions, and one of them can be selected according to the needs.

[0038] One scheme of the second-layer waveguide structure 5 is: the second-layer waveguide structure 5 includes a second-layer tapered waveguide 51 and a second-layer inverted tapered waveguide 53; the second-layer tapered waveguide 51 and the second-layer inverted tapered waveguide 53 are located in the same plane; the right surface of the second-layer tapered waveguide 51 is connected to the left surface of the second-layer inverted tapered waveguide 53; the width of the first-layer inverted tapered waveguide 43 gradually decreases from left to right, the width of the second-layer tapered waveguide 51 gradually increases from left to right, and the width of the second-layer inverted tapered waveguide 53 gradually decreases from left to right.

[0039] Another scheme of the second layer waveguide structure 5 is: the second layer waveguide structure 5 includes a second layer tapered waveguide 51, a second layer straight waveguide 52, and a second layer inverted tapered waveguide 53; the second layer straight waveguide 52 is located between the second layer tapered waveguide 51 and the second layer inverted tapered waveguide 53; the second layer tapered waveguide 51, the second layer straight waveguide 52, and the second layer inverted tapered waveguide 53 are located in the same plane; the left surface of the second layer straight waveguide 52 is connected to the right surface of the second layer tapered waveguide 51, and the right surface of the second layer straight waveguide 52 is connected to the left surface of the second layer inverted tapered waveguide 53; the first layer inverted tapered waveguide 43 gradually decreases in width from left to right, the second layer tapered waveguide 51 gradually increases in width from left to right, and the second layer inverted tapered waveguide 53 gradually decreases in width from left to right. The second layer straight waveguide 52 has a constant width from left to right.

[0040] The second-layer conical waveguide 51 is located directly above the first-layer inverted conical waveguide 43. The first-layer inverted conical waveguide 43 and the second-layer conical waveguide 51 form a second light field transition conversion structure to achieve further pulling up of the light field. After the light field is further pulled up, the light is transmitted from the second-layer conical waveguide 51 to the second-layer inverted conical waveguide 53. The second-layer inverted conical waveguide 53 and the covering layer 6 form a pattern spot expansion structure. A spacing is provided between the lower surface of the second-layer conical waveguide 51 and the upper surface of the first-layer inverted conical waveguide 43, and the spacing is set according to needs.

[0041] The second waveguide structure is provided in the present invention to further pull the light field upward and away from the silicon substrate. According to the simulation verification results, the performance is better after adopting the second waveguide structure.

[0042] Furthermore, the lower cladding layer 2 is a SiO2BOX layer. The cover layer 6 is a SiO2 cover layer 6; the substrate 1 is a SOI wafer Si substrate 1; all waveguides are made of SiN material. The bottom tapered waveguide is an inverted tapered silicon waveguide. The first tapered waveguide 41 and the second tapered waveguide 51 are SiN tapered waveguides. The first straight waveguide 42 and the second straight waveguide 52 are SiN straight waveguides. The first inverted tapered waveguide 43 and the second inverted tapered waveguide 53 are SiN inverted tapered waveguides.

[0043] A specific embodiment is now listed, in which the thickness of the lower cladding layer 2 is 3um, the thickness of the bottom inverted tapered waveguide 3 is 220nm, the thickness of the first tapered waveguide 41, the first straight waveguide 42 and the first inverted tapered waveguide 43 are all 400nm, the thickness of the second tapered waveguide 51, the second straight waveguide 52 and the second inverted tapered waveguide 53 are all 150nm, the thickness of the cover layer 6 is 5um, and the distance between the upper surface of the bottom inverted tapered waveguide 3 and the lower surface of the first tapered waveguide 41 is 200nm. m, the distance between the upper surface of the first layer of inverted tapered waveguide 43 and the lower surface of the second layer of tapered waveguide 51 is 600nm; the length of the bottom layer of inverted tapered waveguide 3 is 90um, the length of the first layer of tapered waveguide 41 is 90um, the length of the first layer of straight waveguide 42 is 20um, the length of the first layer of inverted tapered waveguide 43 is 100um, the length of the second layer of tapered waveguide 51 is 100um, the length of the second layer of straight waveguide 52 is 20um, and the length of the second layer of inverted tapered waveguide 53 is 150um. The present invention is not limited to the above embodiments.

[0044] The working principle of the present invention is:

[0045] Step 1: The bottom inverted tapered waveguide 3 and the first tapered waveguide 41 form the first light field transition conversion structure. The signal light is first transmitted from the left side of the bottom inverted tapered waveguide 3 from left to right. Since the width of the bottom inverted tapered waveguide 3 gradually decreases from left to right, the restriction on the light field gradually weakens, while the width of the first tapered waveguide 41 gradually increases from left to right, and the restriction on the light field gradually increases. At the same time, the width variation range of the two is adjusted to meet the phase matching condition, so that the light field can slowly transition from the bottom inverted tapered waveguide 3 to the first tapered waveguide 41, realizing the initial pull-up of the light field;

[0046] Step 2: After the initial pull-up of the light field is completed, the light of the first-layer tapered waveguide 41 is transmitted through the first-layer straight waveguide 42 to the left side of the first-layer inverted tapered waveguide 43. The first-layer inverted tapered waveguide 43 and the second-layer tapered waveguide 51 form a second light field transition conversion structure. The signal light first starts from the left side of the first-layer inverted tapered waveguide 43 and is transmitted from left to right. Since the width of the first-layer inverted tapered waveguide 43 gradually decreases from left to right, the restriction on the light field gradually weakens, while the width of the second-layer tapered waveguide 51 gradually increases from left to right, and the restriction on the light field gradually increases. At the same time, the width variation range of the two is adjusted to meet the phase matching condition, so that the light field can slowly transition from the first-layer inverted tapered waveguide 43 to the second-layer tapered waveguide 51, and further pull-up of the light field is achieved, so that even if the light spot is larger, the substrate 1 will not have a significant impact on the light spot deformation and light field leakage.

[0047] Step 3:

[0048] After the light field is pulled up again, the light of the second-layer conical waveguide 51 is transmitted through the second-layer straight waveguide 52 to the left side of the second-layer inverted conical waveguide 53. The second-layer inverted conical waveguide 53 and the covering layer 6 form a mode spot expansion structure. The signal light first starts from the left side of the second-layer inverted conical waveguide 53 and is transmitted from left to right. Since the width of the second-layer inverted conical waveguide 53 gradually decreases from left to right, the restriction on light gradually weakens, so that the light field slowly diverges into the covering layer 6. Since the cross-sectional area of ​​the covering layer 6 is large, there is basically no constraint on the light field, so the light spot can be expanded to a large extent and the center is far away from the substrate 1, so the coupling loss with the large light spot of the SMF28 single-mode optical fiber can be improved.

[0049] The first and second waveguide structures of the present invention both adopt a conical structure plus an inverted conical structure. The gradual reduction of the size of the inverted conical structure causes the light field to be unable to be well restricted and slowly leaks to the surrounding cladding layer, thereby achieving the effect of expanding the light field. The manufacturing process used in the present invention is compatible with the CMOS process, and the process complexity is low. It does not require the substrate 1 to be hollowed out, so it has good mechanical stability and reliability, and can achieve a larger spot size. At the same time, the light field is not affected by the silicon material of the substrate 1, thereby reducing the coupling loss with the optical fiber and improving the coupling alignment tolerance. The silicon-based large-size spot converter of the present invention belongs to the field of silicon optical communication technology.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A pattern spot converter, comprising a substrate, characterized in that: The substrate is provided with a lower cladding layer and a covering layer in sequence from bottom to top, and the upper end of the lower cladding is provided with a bottom layer inverted tapered waveguide and a first layer of waveguide structure in sequence from bottom to top, the bottom layer inverted tapered waveguide and the first layer of waveguide structure are located in the covering layer, the first layer of waveguide structure includes a first layer of tapered waveguide and a first layer of inverted tapered waveguide, the first layer of tapered waveguide is located directly above the bottom layer inverted tapered waveguide, the bottom layer inverted tapered waveguide and the first layer of tapered waveguide form a first light field transition conversion structure to achieve the pull-up of the light field, after the light field is pulled up, the light is transmitted from the first layer of tapered waveguide to the first layer of inverted tapered waveguide, and the mode spot amplification function is achieved through the first layer of inverted tapered waveguide; The first-layer tapered waveguide and the first-layer inverted tapered waveguide are located in the same plane, and the right surface of the first-layer tapered waveguide is connected to the left surface of the first-layer inverted tapered waveguide; the bottom-layer inverted tapered waveguide has a gradually decreasing width from left to right, the first-layer tapered waveguide has a gradually increasing width from left to right, and the first-layer inverted tapered waveguide has a gradually decreasing width from left to right; The first layer of waveguide structure also includes a first layer of straight waveguide, which is located between the first layer of tapered waveguide and the first layer of inverted tapered waveguide, and the first layer of tapered waveguide, the first layer of straight waveguide, and the first layer of inverted tapered waveguide are located in the same plane; the left surface of the first layer of straight waveguide is connected to the right surface of the first layer of tapered waveguide, and the right surface of the first layer of straight waveguide is connected to the left surface of the first layer of inverted tapered waveguide; the bottom layer of inverted tapered waveguide has a gradually decreasing width from left to right, the first layer of tapered waveguide has a gradually increasing width from left to right, and the first layer of inverted tapered waveguide has a gradually decreasing width from left to right; The second waveguide structure also includes a second waveguide structure located in the cover layer, the second waveguide structure includes a second tapered waveguide and a second inverted tapered waveguide, the second tapered waveguide is located directly above the first inverted tapered waveguide, the first inverted tapered waveguide and the second tapered waveguide form a second light field transition conversion structure to further pull up the light field, after the light field is further pulled up, the light is transmitted from the second tapered waveguide to the second inverted tapered waveguide; the second inverted tapered waveguide and the cover layer form a pattern spot expansion structure; a gap is provided between the lower surface of the second tapered waveguide and the upper surface of the first inverted tapered waveguide; The second-layer tapered waveguide and the second-layer inverted tapered waveguide are located in the same plane, and the right surface of the second-layer tapered waveguide is connected to the left surface of the second-layer inverted tapered waveguide; the width of the first-layer inverted tapered waveguide gradually decreases from left to right, the width of the second-layer tapered waveguide gradually increases from left to right, and the width of the second-layer inverted tapered waveguide gradually decreases from left to right; The second layer of waveguide structure also includes a second layer of straight waveguide, which is located between the second layer of tapered waveguide and the second layer of inverted tapered waveguide, and the second layer of tapered waveguide, the second layer of straight waveguide, and the second layer of inverted tapered waveguide are located in the same plane; the left surface of the second layer of straight waveguide is connected to the right surface of the second layer of tapered waveguide, and the right surface of the second layer of straight waveguide is connected to the left surface of the second layer of inverted tapered waveguide; the width of the first layer of inverted tapered waveguide gradually decreases from left to right, the width of the second layer of tapered waveguide gradually increases from left to right, and the width of the second layer of inverted tapered waveguide gradually decreases from left to right.

2. The pattern spot converter according to claim 1, characterized in that: The lower cladding layer is made of SiO2 material; the cover layer is made of SiO2 material; the substrate is made of SOI wafer Si substrate; the bottom inverted cone waveguide is made of Si material, and the first waveguide structure is made of SiN material.

3. The pattern spot converter according to claim 1, characterized in that: The second waveguide structure is made of SiN material.

4. The pattern spot converter according to claim 1, characterized in that: The first layer of inverted tapered waveguide and the covering layer form a mode spot expansion structure.

5. The pattern spot converter according to claim 1, characterized in that: The lower surface of the bottom inverted cone waveguide is connected to the upper surface of the lower cladding; a gap is provided between the lower surface of the first tapered waveguide and the upper surface of the bottom inverted cone waveguide; the lower surface of the cover layer is connected to the upper surface of the lower cladding; and the lower surface of the lower cladding is connected to the upper surface of the substrate.

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