Alkali metal hybrid plasmonic y-branch splitter and applications thereof

Abstract

The application relates to an alkali metal hybrid plasmonic Y-type beam splitter and application thereof, the Y-type beam splitter comprising an alkali metal layer, a first material layer and a second material layer which are placed in a vertical direction (y-axis) in a stacking mode, the refractive index of the first material layer being lower than that of the second material layer, and the first material layer being between the alkali metal layer and the second material layer; the second material layer has a Y-type structure in a horizontal direction (x-z plane) section, the second material layer comprising an input section, a bending section and an output section, the output section comprising two parallel first and second output sections, and light waves entering the input section being output from the first and second output sections through the bending section; and a protective layer is coated outside the alkali metal layer, and the protective layer is used for preventing oxidation of the alkali metal. The beam splitter has the characteristics of high transmission, strong localization and small size.

Description

TECHNICAL FIELD

[0001] The application relates to a beam splitter, in particular to an alkali metal hybrid plasmonic Y-type beam splitter and application thereof. BACKGROUND

[0002] With the gradual maturity of technology and industry chain, optical devices are developing towards high integration. Traditional optical devices have been unable to meet the growing demand. At this time, photonic integrated chips are favored in the fields of optical interconnection and optical communication due to their small size, low energy consumption, and large bandwidth. Photonic integrated chips can be made of different materials, including silicon, indium phosphide, silicon nitride, polymer, silicon dioxide, lithium niobate, etc. At the same time, the plasmonic effect of alkali metals (mainly sodium) has the characteristics of strong constraint and low loss, which can further improve the integration and propagation length of waveguides compared to traditional metals (such as gold / silver / copper), and thus be applied to the field of subwavelength photonic integration.

[0003] The surface plasmonic effect of alkali metals belongs to the metal surface plasmonic effect. Because the real part of the refractive index of alkali metals is larger than that of noble metals, it means that the dispersion of the medium to electromagnetic waves is weak, the mode area is small, and therefore more compact photonic devices can be obtained. At the same time, the imaginary part of the refractive index of alkali metals is smaller than that of noble metals, which means that the absorption of the medium to electromagnetic waves is small, so the loss of electromagnetic wave transmission is small and the transmission distance is longer. Such photonic devices made by using the surface plasmonic effect of alkali metals are becoming one of the effective paths to break the diffraction limit and realize subwavelength photonic integration.

[0004] Hybrid coupling of silicon-based waveguide modes and metal surface plasmon modes can simultaneously achieve low transmission loss, nanoscale light field restriction capability, small cross-crosstalk between waveguides, and wide frequency band operation characteristics. Due to its excellent characteristics, this kind of plasmonic hybrid waveguide is currently being highly concerned by the industry. The metal materials mainly used are gold, silver, and copper, and the device size of the Y-type beam splitter based on the above materials is in the micron level.

[0005] Traditional hybrid plasmonic Y-type beam splitters are mostly based on Y-type beam splitter structures of metals (gold / silver / copper). There are mainly metal-silicon dioxide-silicon type, metal-silicon dioxide-silicon-silicon dioxide-metal type, etc. However, in order to improve the transmittance, the supported plasmonic mode has a weak level of binding to the light field, so the device size is large. Further improving the transmittance of the hybrid Y-type beam splitter, improving the mode field confinement capability, and reducing the device size are key problems that need to be solved in this field. SUMMARY

[0006] In order to solve the above problems, the application provides an alkali metal hybrid plasmonic Y-type beam splitter, which creatively combines the Y-type beam splitter in the on-chip photonic integration and the alkali metal surface plasmon, and improves the device integration, light wave transmittance and light field confinement ability.

[0007] In order to solve the above problems, the application provides an alkali metal hybrid plasmonic Y-type beam splitter, which creatively combines the Y-type beam splitter in the on-chip photonic integration and the alkali metal surface plasmon, and improves the device integration, light wave transmittance and light field confinement ability.

[0008] As a preferred scheme, the second material layer is coated with the first material layer on the side. More specifically, the first material layer is composed of one or more materials, and the refractive index of all materials in the first material layer is lower than that of the second material layer. In the case of a specific material, the first material layer is silicon dioxide or organic photoresist. The second material layer is silicon, silicon nitride, gallium arsenide, polymer or lithium niobate.

[0009] As another preferred scheme, the second material layer is directly in contact with the substrate without the first material layer, and the first material layer is only arranged on the side and above the second material layer. Figure 2 As another preferred scheme, the second material layer is directly in contact with the substrate without the first material layer, and the first material layer is only arranged on the side and above the second material layer.

[0010] In order to support the device and at the same time play a protective role, the Y-type beam splitter of the application further comprises a substrate layer, and the first material layer is arranged on the substrate layer.

[0011] The alkali metal layer is sodium, potassium or lithium, and sodium or potassium can be selected for safety and stability.

[0012] In the Y-type beam splitter based on alkali metal, the length of each section affects the transmission efficiency and loss value of light, and the width of the curved section affects the interference performance of light waves in the two output sections. The length of the curved section based on hybrid is 100-900 nm, and the width is 200 nm. The bending diameter of the curved section affects the light wave loss and at the same time affects the size of the device. Based on the characteristics of forming a nanoscale device and low loss, the bending diameter of the curved section is 450-600 nm.

[0013] The width range W of the high-refractive-index waveguide is greater than 20 nm, and as the waveguide width W increases, the number of modes supported by the hybrid waveguide also increases, gradually evolving from a single-mode waveguide to a multi-mode waveguide.

[0014] The thickness of the second material layer is 150 nm to 350 nm. When the thickness of the second material layer is less than 150 nm, the longitudinal mode field leaks too much, which is not conducive to realizing a Y-type beam splitter with small loss. When the thickness of the second material layer is greater than 350 nm, it is not conducive to realizing a Y-type beam splitter with high integration.

[0015] As a preferred solution, the spacing between the alkali metal layer and the second material layer is 20 nm to 400 nm. The beam splitter in the application is preferably suitable for optical waves with a wavelength of 1200 nm to 1700 nm.

[0016] The alkali metal hybrid plasmonic Y-type beam splitter in the application is used in a Mach-Zehnder modulator.

[0017] The beneficial effects of the application include that the alkali metal-based hybrid plasmonic Y-type beam splitter in the application can realize beam splitting and regulation in a subwavelength photonic transmission process in a communication waveband. The Y-type beam splitter has the characteristics of high transmission, strong localization and small size, and can be further applied in a Mach-Zehnder electro-optical modulator. The more specific effects will be embodied in the specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The structure diagram of the alkali metal hybrid plasmonic Y-type beam splitter in the application;

[0019] Figure 2 The side view of the alkali metal hybrid plasmonic Y-type beam splitter in the application;

[0020] Figure 3 The top view of the alkali metal hybrid plasmonic Y-type beam splitter;

[0021] Figure 4 The x-y plane eigenmode field distribution diagram of the alkali metal hybrid plasmonic Y-type beam splitter in the application when the waveguide width is 200 nm;

[0022] Figure 5 The x-z plane mode field distribution diagram of the alkali metal hybrid plasmonic Y-type beam splitter in the application when the width is 200 nm, the bending diameter (D) is 450 nm, and the bending length (Ls) is 400 nm;

[0023] Figures 6-8 The structure diagram of the alkali metal hybrid plasmonic Y-type beam splitter in the application with different structures;

[0024] 1, protective layer, 2, alkali metal layer, 3, first refractive index material layer, 4, second refractive index material layer, 5, substrate layer, 6, input section, 7, output section, 8, bending section. DETAILED DESCRIPTION

[0025] The application will be further described in detail below with reference to the drawings and specific embodiments, but it should be understood that the scope of protection of the application is not limited by the specific embodiments.

[0026] The alkali metal hybrid plasmonic Y-type beam splitter in the application comprises a stacked alkali metal layer and a first material layer, a coordinate system is established with the light wave propagation direction as the Z-axis direction and the stacking direction as the y-axis direction, the value of each layer in the y direction is the thickness of the corresponding layer, a second material layer is embedded in the first material layer, the refractive index of the second material layer is higher than that of the first material layer, and the first material layer is between the second material layer and the alkali metal layer. The first material layer is in direct contact with the alkali metal layer, and the second material layer is in direct contact with the first material layer, so that a refractive index difference is formed between the first material layer and the second material layer, and then a waveguide mode is formed, the alkali metal layer forms a plasmonic mode, and the two modes form a hybrid mode on the first material layer.

[0027] The light wave propagates in the first material layer between the alkali metal layer and the second material layer, and the light wave in this region is hybridly formed based on the surface plasmonic mode of the alkali metal and the waveguide mode of the second refractive index material waveguide. After hybridization, the light wave combines the high localization and high loss characteristics of the metal plasmonic mode and the low loss and low localization characteristics of the waveguide mode. The thickness of the first material layer between the second material layer and the alkali metal layer is 20 nm to 400 nm, and above this thickness, the waveguide characteristics are obvious, the localization is low, which is not conducive to size reduction and high integration, and below this thickness, the plasmonic characteristics are obvious, and the loss is high.

[0028] The plasmonic mode of the alkali metal has strong localization and low loss compared to other metal plasmonic modes. Combining the alkali metal plasmonic mode and the waveguide mode is conducive to forming nanoscale devices.

[0029] The second material layer in the application is surrounded by the first material layer on all four sides (i.e. excluding the two end faces in the direction of the light wave). It can also be understood that in the cross section of the device perpendicular to the Z-axis direction, the second material layer is surrounded by the first material layer on all four sides. The first material layer can be any material with a lower refractive index than the second material layer, and can be a single material or multiple materials. If it is multiple materials, it can be a composite material composed of multiple materials, or it can be different materials on the top, bottom, left and right sides of the second refractive index material, i.e. the top side is the first material, the bottom side is the second material, the left side is the third material, and the right side is the fourth material. The four materials are different, but the refractive indices of all the materials are lower than that of the second refractive index material. The light beam propagates in the waveguide mode in the second material layer.

[0030] The protective layer is arranged around the alkali metal. The alkali metal is easy to corrode and oxidize, unstable and strong. The protective layer is arranged on the alkali metal to enhance the stability of the alkali metal, thereby increasing the service life of the device. The protective layer can be any material that does not react with the alkali metal at room temperature. Further, the protective layer can be any material that does not react with the alkali metal and air and / or water at room temperature. Still further, the protective layer can be any material that does not react with the alkali metal and air and / or water at room temperature or high temperature. More specifically, the protective layer can be silicon dioxide, spin-on glass, organic photoresist, or aluminum oxide. These materials are stable and can be made of the same material as the first refractive index material, which is beneficial to the stability and uniformity of the device.

[0031] The first refractive index material and the second refractive index material only need to satisfy the difference in refractive index. Since they are in direct contact with the alkali metal, they need to satisfy the condition of not reacting with the alkali metal and the second refractive index material. Therefore, the first refractive index material can be silicon dioxide, spin-on glass (SOG), organic photoresist, or aluminum oxide, and the second refractive index material can be silicon, silicon nitride, gallium arsenide, a polymer, lithium niobate, etc. Among them, the polymer mainly includes polymethyl methacrylate (PMMA) and its fluoride and deuteride, epoxy resin, polystyrene, polyorganosilooxane, cross-linked benzocyclobutane (BCB), cross-linked acrylic salt polymer, fluorine-containing polyarylsulfide and fluorine-containing polyarylether, epoxy resin, polyimide and fluorine-containing polyimide, etc. The hybrid mode formed by these materials has low loss in the optical communication band and low manufacturing cost, which is beneficial to optical transmission.

[0032] The second refractive index material layer in the application is a Y-shaped structure, forming a Y-shaped beam splitter for splitting a light beam into two beams, which comprises an input section at the starting end, an output section at the end, and the two are connected by a bending section, the light beam is input through the input section and then split into two beams through the bending section, and the two beams are output through the first output section and the second output section respectively, wherein the first output section and the second output section are parallel, the distance between the two affects the coupling of the two output lights, and the bending section and the output section jointly affect the light splitting performance, in the application, the two output sections can be designed to be completely the same, that is, a completely symmetrical Y-shaped beam splitter, the bending section is designed as shown in the figure, wherein Ls is the bending length, D is the bending diameter, the height value H (the thickness of the second refractive index material layer, that is, the y-axis value) of the second refractive index material is 150 nm to 350 nm, which is usually the thickness of the silicon layer of the SOI wafer, and the width value W (the x-axis value) is about 200 nm, preferably the height H = 220 nm and the width W = 200 nm. The values of Ls and D jointly affect the light loss value, the bending length ranges from 100 nm to 900 nm, and the bending diameter ranges from 450 nm to 600 nm. The bending length and the bending diameter cooperatively, when the bending length is 400 nm, the total transmittance of the light beam is more than 80%. The obtained beam splitter has low loss and strong light field binding ability.

[0033] A hybrid mode is formed between the alkali metal layer and the second refractive index material layer, and the distance between the two affects the performance of the hybrid mode, and the preferred hybrid mode is obtained when the distance is 20 nm to 400 nm.

[0034] In the x-y plane, the alkali metal layer, the first refractive index material layer and the second refractive index material layer are stacked in order, thereby forming an alkali metal hybrid plasmonic Y-shaped beam splitter structure, thereby reducing the size of the photonic device. The intrinsic mode of the Y-shaped beam splitter of the alkali metal hybrid plasmonic Y-shaped beam splitter is formed by the hybridization of the surface plasmon mode of the alkali metal layer and the waveguide mode in the high refractive index material Y-shaped beam splitter. The energy of the hybrid mode is mainly concentrated in the low refractive index material layer. Because the surface plasmon mode has the characteristics of high localization and high loss, and the waveguide mode has the characteristics of low loss and low localization, the hybrid mode combines the characteristics of the two. At the same time, in the x-z plane, the alkali metal hybrid plasmonic waveguide adopts the same width, which can reduce the process difficulty and make the light pass through the Y-shaped beam splitter on average. Adjusting the bending diameter of the bending section can effectively avoid the weak coupling phenomenon that occurs when the light passes through the two parallel waveguides (two output sections). The bending length (Ls) and the bending diameter jointly determine the radius of curvature of the bending waveguide. The smaller the radius of curvature, the smaller the bending leakage loss of the Y-shaped beam splitter. The ratio of the bending length to the bending diameter is optimized, which can further reflect the low loss characteristics of the Y-shaped beam splitter.

[0035] In addition, the structure of the Y-shaped beam splitter is not limited to Figure 1The middle layer structure can also take the form of (1) Figure 6 The middle alkali metal layer is embedded in the first refractive index material, surrounded by the first refractive index material, and the second refractive index material is placed on the upper end of the first refractive index material. In this and the rest of the text, the lower end is close to the substrate layer, and the upper end is far from the substrate layer. (2) Figure 7 The middle alkali metal layer is embedded in the first refractive index material, surrounded by the first refractive index material, and the second refractive index material is placed on the upper end of the first refractive index material. In this and the rest of the text, the lower end is close to the substrate layer, and the upper end is far from the substrate layer. (2) Figure 8 The middle alkali metal layer is embedded in the first refractive index material, surrounded by the first refractive index material, and the second refractive index material is placed on the upper end of the first refractive index material. In this and the rest of the text, the lower end is close to the substrate layer, and the upper end is far from the substrate layer. (2) Figure 2 The difference between the structure and the structure is that the lower end of the alkali metal layer is embedded in the first refractive index material layer, forming a lower convex structure embedded in the upper surface of the first refractive index material, and the rest is wrapped by a protective layer. Any of the above structures forms a Y-shaped structure for the second refractive index material layer.

[0036] The following is an example of a hybrid plasmonic Y-shaped beam splitter with an alkali metal layer as shown in the structure. Figure 2 The following is an example of a hybrid plasmonic Y-shaped beam splitter with an alkali metal layer as shown in the structure.

[0037] Example 1

[0038] Silicon dioxide is used as the material for the protective layer and the first refractive index material layer, metallic sodium is used as the material for the alkali metal layer, and silicon is used as the material for the second refractive index material layer. The refractive index of silicon dioxide is 1.44, the refractive index of metallic sodium is 0.105+7.095i, and the refractive index of silicon is 3.4. The difference in refractive index between silicon and silicon dioxide is 1.96, forming a waveguide mode. The side of the alkali metal opposite the second refractive index material is smooth to prevent the formation of an air gap and affect the light transmission mode. The distance between the alkali metal and the second refractive index material is 50 nm; the thickness of the alkali metal layer is about 1 um; for the second refractive index material layer, when the height is 220 nm, the width (W) is 200 nm, the curved segment length (Ls) is 200 nm, and the curved diameter (D) is 450 nm, the transmittance of the Y-shaped beam splitter reaches 82.80%, and the loss reaches 0.0981 dB / um. The electric field distribution of the Y-shaped beam splitter in the x-z and x-y directions is shown in Figure 4 and Figure 5 It can be seen from Figure 4 that the Y-shaped beam splitter in this embodiment has high transmittance and strong localization in the x-y plane, and from Figure 5 that the Y-shaped beam splitter in this embodiment has strong localization in the x-z plane.

[0039] Example 2

[0040] Silicon dioxide is used as the material of the protective layer and the first refractive index material layer, sodium is used as the material of the alkali metal layer, and silicon is used as the material of the second refractive index material layer, wherein the refractive index of silicon dioxide is 1.44, the refractive index of sodium is 0.105+7.095i, the refractive index of silicon is 3.4, the refractive index difference between silicon and silicon dioxide is 1.96, a waveguide mode is formed, the side of sodium opposite to the second refractive index material is smooth to prevent the formation of an air gap and affect the light transmission mode, the distance between the alkali metal and the second refractive index material is 50 nm, the thickness of the alkali metal layer is about 1 um, and for the second refractive index material layer, when the height is 220 nm, the width (W) is 200 nm, the curved segment length (Ls) is 400 nm, and the curved diameter (D) is 450 nm, it is known from the test performance that the transmittance of the Y-type beam splitter reaches 82.05%, and the loss reaches 0.0981 dB / um.

[0041] Example 3

[0042] Silicon dioxide is used as the material of the protective layer and the first refractive index material layer, sodium is used as the material of the alkali metal layer, and silicon is used as the material of the second refractive index material layer, wherein the refractive index of silicon dioxide is 1.44, the refractive index of sodium is 0.105+7.095i, the refractive index of silicon is 3.4, the refractive index difference between silicon and silicon dioxide is 1.96, a waveguide mode is formed, the side of sodium opposite to the second refractive index material is smooth to prevent the formation of an air gap and affect the light transmission mode, the distance between the alkali metal and the second refractive index material is 50 nm; the thickness of the alkali metal layer is about 1 um; for the second refractive index material layer, when the height is 220 nm, the width (W) is 200 nm, the curved segment length (Ls) is 600 nm, and the curved diameter (D) is 550 nm, it is known from the test performance that the transmittance of the Y-type beam splitter reaches 74.83%, and the loss reaches 0.0979 dB / um.

[0043] Example 4

[0044] Silicon dioxide is used as the material of the protective layer and the first refractive index material layer, sodium is used as the material of the alkali metal layer, and silicon is used as the material of the second refractive index material layer, wherein the refractive index of silicon dioxide is 1.44, the refractive index of sodium is 0.105+7.095i, the refractive index of silicon is 3.4, the refractive index difference between silicon and silicon dioxide is 1.96, a waveguide mode is formed, the side of sodium opposite to the second refractive index material is smooth to prevent the formation of an air gap and affect the light transmission mode, the distance between the alkali metal and the second refractive index material is 20 nm, the thickness of the alkali metal layer is about 1 um, and for the second refractive index material layer, when the height is 150 nm, the width (W) is 200 nm, the curved segment length (Ls) is 400 nm, and the curved diameter (D) is 450 nm, it is known from the test performance that the transmittance of the Y-type beam splitter reaches 81.33%, and the loss reaches 0.2186 dB / um.

[0045] Example 5

[0046] Silicon dioxide is used as the material of the protective layer and the first refractive index material layer, sodium is used as the material of the alkali metal layer, and silicon is used as the material of the second refractive index material layer, wherein the refractive index of silicon dioxide is 1.44, the refractive index of sodium is 0.105+7.095i, the refractive index of silicon is 3.4, the refractive index difference between silicon and silicon dioxide is 1.96, a waveguide mode is formed, the side of sodium opposite to the second refractive index material is smooth to prevent the formation of an air gap and affect the light transmission mode, the distance between the alkali metal and the second refractive index material is 20 nm; the thickness of the alkali metal layer is about 1 um; for the second refractive index material layer, when the height is 300 nm, the width (W) is 250 nm, the curved segment length (Ls) is 300 nm, and the curved diameter (D) is 400 nm, it is known from the test performance that the transmittance of the Y-type beam splitter reaches 84.44%, and the loss reaches 0.1187 dB / um.

[0047] Example 6

[0048] Silicon dioxide is used as the material of the protective layer and the first refractive index material layer, sodium is used as the material of the alkali metal layer, and silicon is used as the material of the second refractive index material layer, wherein the refractive index of silicon dioxide is 1.44, the refractive index of sodium is 0.105+7.095i, the refractive index of silicon is 3.4, the refractive index difference between silicon and silicon dioxide is 1.96, a waveguide mode is formed, the side of sodium opposite to the second refractive index material is smooth to prevent the formation of an air gap and affect the light transmission mode, and the distance between the alkali metal and the second refractive index material is 100 nm; the thickness of the alkali metal layer is about 1 um; for the second refractive index material layer, when the height is 300 nm, the width (W) is 200 nm, the curved segment length (Ls) is 300 nm, and the curved diameter (D) is 400 nm, it is known from the test performance that the transmittance of the Y-type beam splitter reaches 90.01%, and the loss reaches 0.0287 dB / um.

[0049] Example 7

[0050] Silicon dioxide is used as the material of the protective layer and the first refractive index material layer, potassium is used as the material of the alkali metal layer, and silicon is used as the material of the second refractive index material layer, wherein the refractive index of silicon dioxide is 1.44, the refractive index of potassium is 0.04+7.02i, the refractive index of silicon is 3.4, the refractive index difference between silicon and silicon dioxide is 1.96, a waveguide mode is formed, the side of potassium opposite to the second refractive index material is smooth to prevent the formation of an air gap and affect the light transmission mode, and the distance between the alkali metal and the second refractive index material is 50 nm; the thickness of the alkali metal layer is about 1 um; for the second refractive index material layer, when the height is 220 nm, the width (W) is 200 nm, the curved segment length (Ls) is 400 nm, and the curved diameter (D) is 450 nm, it is known from the test performance that the transmittance of the Y-type beam splitter reaches 79.96%, and the loss reaches 0.1211 dB / um.

[0051] Example 8

[0052] The Y-type beam splitter obtained in Example 1 is used for a Mach-Zehnder modulator, and the beam splitter is reversely used (that is, the input end and the output port are interchanged) to realize the function of the Mach-Zehnder modulator. By applying a voltage on the waveguide arm, a carrier dispersion effect is generated, so as to change the optical waveguide phase on the waveguide arm, so as to cause interference constructive (“1” level) and interference destructive (“0” level), and finally the “0-1” modulation of the signal can be realized, and the extinction ratio of the Mach-Zehnder modulator can reach 18 dB.

[0053] In addition to the above embodiments, the Y-type beam splitter selects organic photoresist as the material of the protective layer and the first refractive index material layer; potassium or sodium as the alkali metal layer; silicon nitride, gallium arsenide or lithium niobate as the material of the second refractive index material layer. The refractive index of the organic photoresist is about 1.5; the refractive index of the metal potassium is 0.04+7.02i, the refractive index of the metal sodium is 0.105+7.095i; the refractive index of the silicon nitride is 1.9963, the refractive index of the lithium niobate is 2.2, and the refractive index of the gallium arsenide is 3.374. The size of each layer is set the same as that of Embodiment 7. The listed embodiments are tested, and the transmittance is all above 80%, and the loss is lower than 0.0287 dB / um.

[0054] The above embodiments have made a detailed introduction to the present application, and a number of modifications or conventional improvements made by the person skilled in the art after referring to the present application are all covered in the protection scope of the present application.

Claims

1. An alkali metal hybrid plasmonic Y-type beam splitter, characterized in that: include An alkali metal layer, a first material layer, and a second material layer are stacked in a vertical direction. The refractive index of the first material layer is lower than that of the second material layer. The first material layer is located between the alkali metal layer and the second material layer. The second material layer has a Y-shaped structure in the horizontal cross section. The second material layer includes an input section, a bending section and an output section. The output section includes two parallel first output sections and a second output section. Light waves enter from the input section, pass through the bending section and are output from the first output section and the second output section. A protective layer is applied to the outside of the alkali metal layer to prevent oxidation of the alkali metal, wherein the alkali metal is sodium or potassium.

2. The alkali metal hybrid plasmonic Y-type beam splitter according to claim 1, characterized in that: The second material layer is embedded within the first material layer.

3. The alkali metal hybrid plasmonic Y-type beam splitter according to claim 2, characterized in that: The second material layer is surrounded by the first material layer.

4. The alkali metal hybrid plasmonic Y-type beam splitter according to claim 3, characterized in that: The first material layer is composed of one or more materials, and the refractive index of all materials in the first material layer is lower than that of the second material layer.

5. The alkali metal hybrid plasmonic Y-type beam splitter according to claim 1, characterized in that: It also includes a substrate layer, on which the first material layer is placed.

6. The alkali metal hybrid plasmonic Y-type beam splitter according to claim 1, characterized in that: The first material layer is silicon dioxide or organic photoresist.

7. The alkali metal hybrid plasmonic Y-type beam splitter according to claim 1, characterized in that: The second material layer is silicon, silicon nitride, gallium arsenide, polymer, or lithium niobate.

8. The alkali metal hybrid plasmonic Y-type beam splitter according to claim 1, characterized in that: The length Ls of the curved section is 100~900 nm, and the width W is 150~250 nm.

9. The alkali metal hybrid plasmonic Y-type beam splitter according to claim 1, characterized in that: The bending diameter D of the bent section is 450~600nm.

10. The alkali metal hybrid plasmonic Y-type beam splitter according to claim 1, characterized in that: The thickness of the second material layer is 150 nm to 350 nm.

11. The alkali metal hybrid plasmonic Y-type beam splitter according to claim 1, characterized in that: The distance between the alkali metal layer and the second material layer is 20 nm to 400 nm.

12. The alkali metal hybrid plasmonic Y-type beam splitter according to claim 1, characterized in that: The wavelength of the light wave is 1200 nm to 1700 nm.

13. The alkali metal hybrid plasmon Y-type beam splitter of claim 1 is used in a Mach-Zehnder modulator.

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