Spot Converter

Abstract

The present invention relates to the field of integrated optics and provides a spot converter comprising: a substrate layer; an input waveguide disposed on the substrate layer and having a greater refractive index than the substrate layer; an output waveguide disposed on the substrate layer and having a greater refractive index than the substrate layer; and a surface plasmon waveguide disposed between and in communication with the input and output waveguides, configured to induce a surface plasmon effect in electromagnetic waves transmitted from the input waveguide. The present invention effectively addresses the issues of large size and low extinction ratio in conventional spot converters, thereby achieving a compact size and high extinction ratio, saving raw material and process costs.

Description

Technical Field

[0001] The present invention relates to the field of integrated optical technology, and in particular to a pattern spot converter. Background Art

[0002] On-chip polarization multiplexing systems place very high demands on the purity of polarization states, that is, to effectively filter out unwanted polarization states and retain only the desired polarization states. Spot-type converters that significantly improve the purity of the system's polarization states have important applications in many fields, such as quantum communications and biosensing. Although spot-type converters made of traditional optical dielectric materials are easy to process, due to the weak birefringence effect, the device requires a very long length to achieve the accumulation of polarization effects, which leads to a large size. Although the use of sub-wavelength grating structures can shorten the device size, it still cannot achieve the ideal extinction effect for highly integrated optical interconnect systems. How to obtain a spot-type converter with a small device size and a high extinction ratio is an urgent problem that those skilled in the art need to solve. Summary of the Invention

[0003] The present invention provides a pattern spot converter, which is used to solve the problems of large size and low extinction ratio of pattern spot converters in the prior art, achieves the purpose of short size and high extinction ratio, and saves raw material and process costs.

[0004] The present invention provides a pattern spot converter, comprising: a substrate layer; an input waveguide, arranged on the substrate layer, and having a refractive index greater than that of the substrate layer; an output waveguide, arranged on the substrate layer, and having a refractive index greater than that of the substrate layer; and a surface plasmon waveguide, arranged between the input waveguide and the output waveguide, and connected to the input waveguide and the output waveguide, for generating a surface plasmon effect on electromagnetic waves transmitted from the input waveguide.

[0005] According to the pattern spot converter provided by the present invention, the surface plasmon waveguide includes: an effect plate for exciting the surface plasmon effect of the electromagnetic wave, the effect plate is arranged on both sides of the central axis of the input waveguide and the output waveguide, and there is a gap between the effect plates, and the dielectric constant of the effect plate is negative.

[0006] According to the pattern spot converter provided by the present invention, a transmission waveguide is provided between the effect plates, both ends of the transmission waveguide are smoothly connected to the input waveguide and the output waveguide respectively, and a gap is left between the effect plate and the transmission waveguide.

[0007] According to the pattern spot converter provided by the present invention, the input waveguide includes: an input part; a first conversion part, which is smoothly connected to the wave output end of the input part; the materials of the first conversion part and the input part are both optical medium materials, the wave input end and the wave output end of the input part are of the same width, and the width of the wave input end of the first conversion part is greater than the width of its wave output end.

[0008] According to the pattern spot converter provided by the present invention, the output waveguide includes: a second conversion part; an output part, which is smoothly connected to the wave output end of the second conversion part; the second conversion part and the output part are both made of optical medium materials; the input end and the output end of the output part are of the same width, and the input end of the second conversion part is smaller than the width of its output end.

[0009] According to the pattern spot converter provided by the present invention, the input part and the output part are rectangular parallelepiped structures with equal width and height, the first conversion part and the second conversion part have the same structure and are both right quadrangular prism structures with an isosceles trapezoidal bottom surface, wherein the height of the quadrangular prism is equal to the height of the rectangular parallelepiped, and the opposite surface of the smallest side surface of the right quadrangular prism is congruent with and connected to the cross-section of the rectangular parallelepiped; the height of the transmission waveguide is less than the height of the first conversion part and the second conversion part, and the height of the transmission waveguide is equal to the height of the effect plate.

[0010] According to the spot converter provided by the present invention, the transmission waveguide, input waveguide and output waveguide are all made of the same optical medium material.

[0011] According to the spot converter provided by the present invention, the optical medium material includes: silicon on insulator or silicon nitride.

[0012] According to the pattern spot converter provided by the present invention, a plurality of extinction teeth arranged along the axis direction of the transmission waveguide are provided at the outer edge of the effect plate, and the extinction teeth and the effect plate are made of the same material.

[0013] According to the pattern spot converter provided by the present invention, the extinction teeth are in a rectangular parallelepiped shape, the thickness of the extinction teeth is equal to the thickness of the effect plate, and the spacing between the extinction teeth is equal.

[0014] According to the pattern spot converter provided by the present invention, the number of extinction teeth on a single side of the effect plate is greater than or equal to 18.

[0015] According to the pattern spot converter provided by the present invention, the material of the substrate layer is silicon dioxide.

[0016] The pattern converter provided by the present invention utilizes the surface plasmon effect of the surface plasmon waveguide by arranging a surface plasmon waveguide between the input waveguide and the output waveguide. This effect breaks through the diffraction limit of traditional optical dielectric materials, confines the light field to a very small area on the metal surface of the surface plasmon waveguide and enhances it. This solves the problem that traditional optical dielectric devices require a long length to achieve polarization effect accumulation. At the same time, the surface plasmon effect can filter out most of the TM waves (transverse magnetic waves) in the electromagnetic waves transmitted from the input waveguide, while retaining most of the TE waves (transverse electric waves). In this way, a high extinction ratio can be achieved, solving the problem in the prior art of not being able to achieve an ideal extinction effect for highly integrated optical interconnect systems.

[0017] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 This is a schematic diagram of the three-dimensional structure of the pattern spot converter provided by the present invention;

[0020] Figure 2 This is a schematic diagram of the setting position of the effect plate provided by the present invention;

[0021] Figure 3 It is a schematic diagram of the connection structure of the transmission waveguide, the input waveguide and the output waveguide provided by the present invention;

[0022] Figure 4 yes Figure 3 Enlarged view of point A;

[0023] Figure 5 This is a schematic diagram of the cross-sectional structure of the pattern spot converter provided by the present invention;

[0024] Figure 6 Schematic diagram of the three-dimensional structure of the input waveguide and output waveguide provided by the present invention;

[0025] Figure 7 This is a schematic diagram of the location of the matte teeth provided by the present invention;

[0026] Figure 8 It is a schematic diagram of the three-dimensional structure of the matte tooth and the effect plate provided by the present invention;

[0027] Figure 9 This is a light field intensity distribution diagram obtained in an experiment using the pattern spot converter provided by the present invention.

[0028] Reference numerals:

[0029] 1-substrate layer, 2-input waveguide, 201-input part, 202-first conversion part, 3-surface plasmon waveguide, 301-effect plate, 302-extinction tooth, 4-output waveguide, 401-output part, 402-second conversion part, 5-transmission waveguide, 6-effect gap. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0031] In the description of the embodiments of the present invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the embodiments of the present invention and to simplify the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. Furthermore, the terms "first," "second," etc., etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] In the description of the embodiments of the present invention, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; and direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on the specific circumstances.

[0033] In the embodiments of the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," or "above" a second feature may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," or "below" a second feature may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0034] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0035] First, some optical concepts are explained:

[0036] Surface plasmon effect: When a light wave (electromagnetic wave) is incident on the interface between metal and dielectric, the free electrons on the metal surface oscillate collectively. The electromagnetic wave couples with the free electrons on the metal surface to form a near-field electromagnetic wave that propagates along the metal surface. If the oscillation frequency of the electrons is consistent with the frequency of the incident light wave, resonance will occur. In the resonant state, the energy of the electromagnetic field is effectively converted into the collective vibration energy of the free electrons on the metal surface. At this time, a special electromagnetic mode is formed: the electromagnetic field is confined to a very small range on the metal surface and enhanced. This phenomenon is called the surface plasmon phenomenon.

[0037] Birefringence in optical waveguides: Birefringence is a well-known phenomenon in physical optics, occurring in uniaxial or biaxial crystals. This phenomenon involves the different propagation velocities of o- and e-light within the crystal (reflecting the different refractive indices of the crystal for o- and e-light). A similar phenomenon occurs in waveguides. When light propagating through a waveguide (or optical fiber) has different polarization directions, the light waves propagate at different speeds (thus, different polarization modes have different effective refractive indices). This is also a form of birefringence. If the performance of an optical device is dependent on the polarization of the light it transmits, the device is polarization-sensitive. Because the polarization state of signal light undergoes random variations after transmission through conventional optical fibers, polarization insensitivity is crucial for optical devices in optical fiber lines. Birefringence is primarily caused by the waveguide structure and materials themselves.

[0038] The following combination Figure 1 The embodiment shown describes the technical solution of the present invention:

[0039] An embodiment of the present invention provides a pattern spot converter, comprising: a substrate layer 1, an input waveguide 2, an output waveguide 4, and a surface plasmon waveguide 3, wherein the input waveguide 2 is arranged on the substrate layer 1, and has a refractive index greater than the refractive index of the substrate layer; the output waveguide 4 is arranged on the substrate 1 layer, and has a refractive index greater than the refractive index of the substrate layer; the plasmon waveguide 3 is arranged between the input waveguide 2 and the output waveguide 4, and is connected to the input waveguide 2 and the output waveguide 4, and is used to generate a surface plasmon effect on the electromagnetic waves transmitted from the input waveguide.

[0040] In a specific application, substrate layer 1 is a silicon dioxide insulating plate with a thickness of 2 μm and a refractive index of 1.444. Both input waveguide 2 and output waveguide 4 are made of silicon with a refractive index of 3.478. The input waveguide 2 and output waveguide 4 are fabricated into strips using photolithography technology so that light waves can be transmitted therein. At the same time, a surface plasmon waveguide 3 is arranged between the input waveguide 2 and the output waveguide 4. The input waveguide 2, the surface plasmon waveguide 3, and the output waveguide 4 are all arranged on the same straight line and connected in sequence, so that the light waves can smoothly reach the surface plasmon waveguide 3, thereby generating a surface plasmon effect. In this embodiment, the surface plasmon waveguide is composed of two silver metal plates, and the two silver metal plates are respectively located on both sides of the middle area of ​​the input waveguide 2 and the output waveguide 4 and fixed on the silicon dioxide plate of the substrate layer 1. A gap is left between the two silver metal plates. When the light wave is transmitted into the gap, a surface plasmon effect will be generated. Under the surface plasmon effect, the main electric field component exists in a form perpendicular to the metal surface, while the electric field component parallel to the metal surface can hardly exist. This hinders the TM wave (transverse magnetic wave) in the input waveguide and retains most of the TE wave (transverse electric wave), thereby achieving the purpose of a high extinction ratio.

[0041] The pattern converter provided in an embodiment of the present invention, by arranging a surface plasmon waveguide between the input waveguide and the output waveguide, can utilize the surface plasmon effect of the surface plasmon waveguide. This effect breaks through the diffraction limit of traditional optical dielectric materials, confines the light field to a very small range on the metal surface of the surface plasmon waveguide and enhances it. This solves the problem that traditional optical dielectric devices require a long length to achieve polarization effect accumulation. At the same time, the surface plasmon effect can filter out most of the TM waves (transverse magnetic waves) in the electromagnetic waves transmitted from the input waveguide, while retaining most of the TE waves (transverse electric waves). In this way, the purpose of high extinction ratio can be achieved, which solves the problem in the prior art that high-integration optical interconnection systems cannot achieve ideal extinction effect.

[0042] According to the embodiment of the present invention, the pattern spot converter is provided. Figure 2 As shown, based on the above scheme, the above-mentioned surface plasmon waveguide 3 includes: an effect plate 301 for exciting the surface plasmon effect of the electromagnetic wave, the effect plate 301 is arranged on both sides of the central axis of the input waveguide and the output waveguide, and there is a gap between the effect plates, and the dielectric constant of the effect plate is negative.

[0043] In a specific application, the surface plasmon waveguide 3 is composed of two effect plates 301. These effect plates are preferably gold plates with a refractive index of 0.238 + 11.263i and a thickness of 40nm. Alternatively, they can be made of copper, aluminum, conductive glass, alkali metals, alloys, intermetallic compounds, or graphene layers. As long as their dielectric constant is negative, it will suffice, as surface plasmons are surface waves that exist at the interface between materials with positive and negative dielectric constants. The properties of surface plasmons require that the dielectric constant of one of the materials be negative; otherwise, the surface plasmon phenomenon cannot exist. The effect plates 301 are positioned on either side of the central axis of the input and output waveguides, with a gap between the effect plates. Within this gap, a surface plasmon effect can occur. Specifically, the primary electric field component of the surface plasmon exists perpendicular to the metal surface, while the electric field component parallel to the metal surface is almost nonexistent, thus hindering TM waves in the input waveguide. The opposite ends of the above-mentioned input waveguide and output waveguide are also provided with a mode spot conversion structure, that is, the light wave mode spot size in the input waveguide is converted into a mode spot size that can propagate in the metal gap. After the surface plasmon waveguide 3 filters the components of the input light wave, the filtered pure light wave is converted from the slit mode spot size to the mode spot size of the output waveguide.

[0044] The pattern spot converter provided in an embodiment of the present invention, by configuring the surface plasmon waveguide 3 to include two 40nm thick gold thin plates with a metal slit between the two plates, can effectively utilize the inner side of the gold effect plate to excite surface plasmons. By configuring the pattern spot converter structure, a filtering effect can be achieved while adapting to the pattern spot size of the input waveguide and the output waveguide.

[0045] According to the embodiment of the present invention, the pattern spot converter is provided. Figure 3-5 As shown, on the basis of the above technical solution, a transmission waveguide 5 is arranged between the effect plates, and the two ends of the transmission waveguide 5 are smoothly connected to the input waveguide 2 and the output waveguide 4 respectively, and a gap is left between the effect plate 301 and the transmission waveguide 5.

[0046] In a specific application, the transmission waveguide 5 is also photolithographically formed into a strip shape from silicon material, and its two ends are smoothly connected to the pattern conversion structure of the input waveguide 2 and the output waveguide 4. The purpose of setting up a smooth connection here is to prevent the light wave pattern size of the input waveguide from abruptly changing, thereby allowing the light wave to be smoothly transmitted from the input waveguide to the transmission waveguide, and finally from the transmission waveguide to the output waveguide; during the photolithographic molding, the transmission waveguide, the input waveguide, and the output waveguide can be formed into an integral body; the transmission waveguide 5 is set in the metal slit of the above-mentioned effect plate 301, and the length and height are equal to the metal slit, except that the width of the transmission waveguide is smaller than the width of the metal slit (see Figure 5 ), the transmission waveguide 5 is a rectangular parallelepiped structure, with its axis and the central axis of the metal slit in the same vertical plane. That is, the effective gaps 6 on both sides of the transmission waveguide are of equal width. The installation of the transmission waveguide 5 within the metal slit enables the generation of mixed-state surface plasmons, thereby largely blocking the TM (transverse magnetic) waves of light on the silicon waveguide while allowing the majority of TE (transverse electric) waves to pass through, thereby filtering out TM waves (transverse magnetic waves). This design also offers improved practical applicability, lower losses, and longer transmission distances.

[0047] The pattern spot converter provided in an embodiment of the present invention can filter out most of the TM waves in the silicon waveguide by providing a silicon transmission waveguide made of the same material as the input waveguide and the output waveguide in the metal slit of the effect plate 301. Compared with the case where no transmission waveguide is provided, it has better practical applicability, lower loss and longer transmission distance.

[0048] According to the embodiment of the present invention, the pattern spot converter is provided. Figure 6 As shown, the above-mentioned input waveguide 2 includes: an input part 201 and a first conversion part 202, and the first conversion part 202 is smoothly connected to the wave output end of the input part 201; the materials of the first conversion part 202 and the input part 201 are both optical medium materials, the input end and the wave output end of the input part are of the same width, and the input end of the first conversion part 202 is wider than the width of its wave output end.

[0049] The output waveguide 4 includes a second conversion portion 402 and an output portion 401, wherein the output portion 401 is smoothly connected to the wave output end of the second conversion portion 402; the second conversion portion 402 and the output portion 401 are both made of optical medium materials; the input and output ends of the output portion 401 are of equal width, and the input width of the second conversion portion 402 is smaller than the width of its wave output end.

[0050] In practical applications, the input portion 201 can be photolithographically fabricated into a strip shape, which is made of silicon. The size of its cross-sectional width determines the size of the light wave mode spot. Therefore, during the input stage, the input end and the output end of the input portion 201 need to be kept equal in width to ensure that the mode spot size of the input light wave is constant. At the same time, the first conversion portion 202 is smoothly connected to the output end of the input portion 201. The main purpose is to ensure that the mode spot size of the light wave does not suddenly change when the light wave turns from the input portion 201 to the first conversion portion 202; at the same time, the width of the input end of the first conversion portion 202 is greater than the width of its output end. This setting is to convert the larger light wave mode size in the input portion into a light wave mode size that can be confined and transmitted within the metal slit or transmission waveguide 5, and at the same time, it can also enable the light wave to produce a surface plasmon effect.

[0051] Similarly, the output portion 401 can be photolithographically fabricated into a strip shape, made of silicon. After filtering the light waves through the surface plasmon waveguide 3, a relatively pure TE wave (transverse electric wave) needs to be output. At this point, the TE wave (transverse electric wave) with a smaller pattern size within the surface plasmon waveguide 3 needs to be converted to a normal output pattern size, or a desired output pattern size. Therefore, the input and output ends of the output portion 401 are of equal width, and the input end width of the second conversion portion 402 is smaller than the output end width. Of course, the widths of the input portion 201 and the output portion 401 can be equal or unequal, and can be flexibly selected based on actual needs.

[0052] The mode spot converter provided in the embodiment of the present invention can better achieve stable propagation of input light waves and convert a large mode spot size into a small mode spot size required for the surface plasmon effect by setting the input waveguide 2 as the input part 201 and the first conversion part 202. Finally, the TE wave (transverse electric wave) retained after filtering is converted and output according to the required mode spot size.

[0053] According to the embodiment of the present invention, the pattern spot converter is provided. Figure 3-6As shown, on the basis of the above technical solution, the input part 201 and the output part 401 are rectangular parallelepiped structures with equal width and height, the first conversion part 202 and the second conversion part 402 have the same structure and are both right quadrangular prism structures with an isosceles trapezoidal bottom surface, wherein the height of the quadrangular prism is equal to the height of the rectangular parallelepiped, and the opposite surfaces of the smallest side surface of the right quadrangular prism are congruent with and connected to the cross-section of the rectangular parallelepiped; the height of the transmission waveguide is less than the height of the first conversion part and the second conversion part, and the height of the transmission waveguide 5 is equal to the height of the effect plate.

[0054] In practical applications, the input portion 201 and the output portion 401 are both made of silicon and are manufactured by a photolithography process. The height and width of the first conversion portion 202 and the second conversion portion 402 are preferably 220 nm and 400 nm, respectively, at the contact surfaces with the input portion 201 and the output portion 401. Since the first conversion portion 202 and the second conversion portion 402 have the same structure and are both right quadrangular prism structures with isosceles trapezoidal bottom surfaces, the angles between the two congruent side surfaces of the first conversion portion 202 and the second conversion portion 402 relative to the central axis are equal, and the distances are also equal. The input light wave mode spot size can be infinitely reduced until it reaches the size required by the surface plasmon waveguide 3. At the same time, the transmission waveguide 5 is also a rectangular parallelepiped structure, with a width equal to the minimum surface of the first conversion part 202 and the second conversion part 402, and a height consistent with the height of the effect plate. In this embodiment, the thickness of the gold effect plate is preferably 40 nm, so the height of the transmission waveguide 5 is 40 nm. After the filtering is completed, the TE (transverse electric wave) mode spot size is converted to the same size as the input part 201 through the same conversion mode, ensuring the consistency of the front and rear light wave input and output sizes.

[0055] According to the spot converter provided by the embodiment of the present invention, the transmission waveguide 5, the input waveguide 2 and the output waveguide 4 are all made of the same optical medium material, which includes silicon on insulator, silicon nitride and other semiconductor materials.

[0056] Silicon-on-insulator (SOI) refers to a technology that replaces traditional bulk silicon substrates with engineered substrates. This substrate consists of three layers: a single-crystal silicon top layer, on which the etched circuitry is formed; a relatively thin insulating silicon dioxide middle layer (referred to as substrate layer 1 in this invention); and a very thick substrate bottom layer, which primarily provides mechanical support for the two upper layers. SOI, with its mature manufacturing process, can achieve dielectric isolation of components in integrated circuits, completely eliminating the parasitic latch-up effect found in bulk silicon CMOS circuits. Silicon nitride and other semiconductor materials can also serve as waveguide materials, as long as their refractive index is greater than that of the substrate layer. Silicon nitride, with a refractive index as high as approximately 2.0, is also a promising material for waveguide fabrication.

[0057] According to the embodiment of the present invention, the pattern spot converter is provided. Figure 7-8 As shown, the outer edge of the effect plate 301 is provided with multiple extinction teeth 302 arranged along the transmission waveguide axis. The extinction teeth 302 are made of the same material as the effect plate 301. The extinction teeth are rectangular, with a thickness equal to that of the effect plate, and the spacing between the extinction teeth is also equal. The number of extinction teeth on a single side of the effect plate is greater than or equal to 18.

[0058] In practical applications, photolithography can be used to cut the outer edge of the effect plate 301 and create extinction teeth 302 with a rectangular structure. Therefore, the thickness of the extinction teeth is equal to the thickness of the effect plate, and the spacing between each extinction tooth is equal. In this embodiment, the number of extinction teeth is preferably set to 18 on a single side and 36 on a double side. The purpose of this setting is to perform multi-level conversion on the residual TM wave (transverse magnetic wave) in the transmission waveguide 5, thereby better eliminating the intrinsic mode (TM mode) with low similarity to the TE mode, so that the extinction ratio of the entire device is very high. Among them, the number of extinction teeth on a single side of the effect plate is set to 18 because it strikes the best balance between the extinction performance and the device length. Of course, it can also be greater than 18, which has a better extinction effect, but the overall length of the device will increase. Of course, it can also be set to less than 18, but the extinction effect will be weakened as the number of extinction teeth decreases.

[0059] The pattern spot converter provided in an embodiment of the present invention can further filter out residual TM waves (transverse magnetic waves) under the action of the effect plate 301 without extinction teeth through the setting of multi-stage extinction teeth, thereby having a better filtering effect than the above embodiment, so that the polarization state purity of the output light wave is higher.

[0060] In the spot pattern converter provided by the present invention, the extinction teeth and effect plate are made of gold, silver, copper, aluminum, conductive glass, alkali metals, alloys, intermetallic compounds, or graphene layers. Any negative dielectric constant is sufficient, as surface plasmons are surface waves that exist at the interface between materials with positive and negative dielectric constants. The properties of surface plasmons require that the dielectric constant of one of the materials be negative; otherwise, surface plasmon phenomena cannot occur.

[0061] According to the embodiment of the present invention, the pattern spot converter is provided. Figure 9 As shown in the figure, this is a light field intensity distribution diagram of a multi-stage extinction tooth spot converter. It is obtained by numerical simulation technology of the 3D full-wave vector finite element method (FEM) to obtain the light field energy flow distribution in the spot converter. Figure 9(a) is a light field intensity distribution diagram of the spot converter provided by the present invention when a TE polarization light wave is input from a top-down perspective; Figure 9 (b) Yes Figure 9 (a) The cross-sectional light field intensity distribution; Figure 9 (c) is a light field intensity distribution diagram of the spot converter provided by the present invention when a TM polarization light wave is input; Figure 9 (d) Yes Figure 9 (c) The cross-sectional light field intensity distribution diagram; the hardware parameters of the device are as follows:

[0062] The substrate material is silicon, with a refractive index of 3.478;

[0063] The buried oxide material layer is silicon dioxide with a thickness of 2 μm and a refractive index of 1.444;

[0064] The cladding material is silicon dioxide with a refractive index of 1.444;

[0065] The input waveguide, transmission waveguide, and output waveguide are all made of silicon, with a refractive index of 3.478, a height of 220 nm, and a width of 400 nm.

[0066] The negative dielectric constant material of the multi-level extinction teeth and effect plate is gold, with a refractive index of 0.238+11.263i and a thickness of 40nm;

[0067] The number of comb-like serrations on the outer side of the effect plate is 18 per side;

[0068] The wavelength of the input light wave is 1550nm;

[0069] Depend on Figure 9 It can be seen that after the TE polarization input light passes through the spot conversion device in this embodiment, most of the light is retained, while after the TM polarization input light passes through the spot converter in this embodiment, the optical power is greatly weakened due to the surface plasmon effect and the multi-level extinction teeth, and its extinction ratio can reach 16.8dB.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A spot converter, characterized in that: include: substrate layer; an input waveguide, disposed on the substrate layer and having a refractive index greater than that of the substrate layer; an output waveguide, disposed on the substrate layer and having a refractive index greater than that of the substrate layer; a surface plasmon waveguide, disposed between the input waveguide and the output waveguide and in communication with the input waveguide and the output waveguide, for generating a surface plasmon effect on the electromagnetic wave transmitted from the input waveguide; The surface plasmon waveguide comprises: Effect plates, used to excite surface plasmon effects of electromagnetic waves, the effect plates being arranged on both sides of the central axis of the input waveguide and the output waveguide, with gaps between the effect plates; A transmission waveguide is provided between the effect plates, and both ends of the transmission waveguide are smoothly connected to the input waveguide and the output waveguide respectively, and a gap is left between the effect plate and the transmission waveguide; A plurality of extinction teeth are arranged at the outer edge of the effect plate and are arranged along the axis direction of the transmission waveguide. The extinction teeth and the effect plate are made of the same material.

2. The pattern converter according to claim 1, characterized in that: The dielectric constant of the effect plate is negative.

3. The pattern converter according to claim 1, wherein: The input waveguide comprises: Input unit; a first conversion part, smoothly connected to the wave output end of the input part; The first conversion part and the input part are both made of optical medium materials. The input end and the output end of the input part have the same width, and the input end of the first conversion part has a width greater than that of the output end.

4. The pattern converter according to claim 3, characterized in that: The output waveguide comprises: a second conversion unit; an output portion, smoothly connected to the wave output end of the second conversion portion; The second conversion part and the output part are both made of optical medium materials; the input end and the output end of the output part have the same width, and the input end of the second conversion part is smaller than the output end.

5. The pattern converter according to claim 4, characterized in that: The input portion and the output portion are rectangular parallelepiped structures of equal width and height, and the first conversion portion and the second conversion portion have the same structure and are both right quadrangular prism structures with isosceles trapezoidal bottom surfaces, wherein the height of the quadrangular prism is equal to the height of the rectangular parallelepiped, and the opposite surface of the smallest side surface of the right quadrangular prism is congruent with and connected to the cross section of the rectangular parallelepiped; The height of the transmission waveguide is smaller than the heights of the first conversion portion and the second conversion portion, and the height of the transmission waveguide is equal to the height of the effect plate.

6. The pattern converter according to claim 5, characterized in that: The transmission waveguide, input waveguide and output waveguide are all made of the same optical medium material.

7. The pattern converter according to claim 6, characterized in that: The optical medium material includes silicon on insulator or silicon nitride.

8. The pattern converter according to claim 1, characterized in that: The extinction teeth are in a rectangular parallelepiped shape, and the thickness of the extinction teeth is equal to the thickness of the effect plate, and the intervals between the extinction teeth are equal.

9. The pattern converter according to claim 8, characterized in that: The number of extinction teeth on a single side of the effect plate is greater than or equal to 18.

10. The pattern spot converter according to any one of claims 1 to 9, characterized in that: The substrate layer is made of silicon dioxide.

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