Metastructure surface beam splitter

Abstract

The invention discloses a super-structure surface beam splitter, and relates to the field of beam splitting devices. The beam splitter comprises a substrate and a superstructure array, the super-structure array comprises a first super-structure array and a second super-structure array; the first super-structure array and the second super-structure array are arranged on the same side of the substrate and are arranged in a crossed manner; incident light enters from one side of the substrate, sequentially passes through the substrate and the super-structure array, and then emits a first target light beam and a second target light beam with different emergent angles; the first super-structure array is used for adjusting the phase of a light beam emitted from the other side opposite to one side of the substrate and emitting a first target light beam with a polarization characteristic; and the second superstructure array is used for adjusting the phase of the light beam emitted from the other side opposite to the side of the substrate and focusing the adjusted light beam to the target position to obtain a second target light beam with the off-axis focusing characteristic. According to the invention, miniaturization and multifunctionalization of an optical system using the beam splitter can be realized.

Description

Technical Field

[0001] The present invention relates to the field of beam splitting devices, and particularly to a metasurface beam splitter. Background Art

[0002] A beam splitter, as a fundamental and crucial functional element in the field of optics, has a very wide range of applications, covering multiple optical system fields such as interferometers, optical communication systems, and precision optical detection. With the continuous progress of modern optical technologies, optical systems are increasingly developing rapidly towards multi-branch designs and miniaturization. Therefore, the importance of a beam splitter, a conventional device used to accurately split an incident light beam into two independent light beams, has become increasingly prominent.

[0003] Most traditional beam splitters are constructed relying on structures such as coated prisms or glass plates. Although these designs meet the basic requirements of beam splitting to a certain extent, their characteristics such as large volume and fixed output direction at a right angle greatly limit the flexibility of optical path design and also pose quite a challenge to system integration.

[0004] In recent years, with the continuous improvement of semiconductor process manufacturing technologies, photonic integrated systems have been widely applied in multiple fields such as optical fiber communication, optical computing, and optoelectronic detection. These systems not only require higher integration and smaller sizes, but also have an urgent need for miniaturization and multifunctionality of their components. The traditional simple beam splitting function has been difficult to meet the diverse requirements of these complex application scenarios. Summary of the Invention

[0005] The objective of the present invention is to provide a metasurface beam splitter, which helps to achieve the miniaturization and multifunctionality of an optical system applying the beam splitter.

[0006] To achieve the above objective, the present invention provides the following solution:

[0007] One aspect of the present invention provides a metasurface beam splitter. The beam splitter includes: a substrate and a metasurface array; the metasurface array includes a first metasurface array and a second metasurface array; the first metasurface array and the second metasurface array are arranged on the same side of the substrate and cross each other; incident light is incident from one side of the substrate, and after passing through the substrate and the metasurface array in sequence, a first target light beam and a second target light beam with different emission angles are emitted; the first metasurface array is used to adjust the phase of the light beam emitted from the other side opposite to one side of the substrate, and emit a first target light beam with polarization characteristics; the second metasurface array is used to adjust the phase of the light beam emitted from the other side opposite to one side of the substrate, and focus the adjusted light beam to a target position to obtain a second target light beam with off-axis focusing characteristics.

[0008] According to an embodiment of the present invention, the transmittance of the materials of the above-mentioned substrate, the above-mentioned first metasurface array, and the above-mentioned second metasurface array in the visible light band is greater than a preset transmittance.

[0009] According to an embodiment of the present invention, the above-mentioned substrate is a transparent substrate.

[0010] According to an embodiment of the present invention, the material of the above-mentioned substrate includes SiO 2 , Ta 2 O 5 , TiO 2 , ITO, AZO, PMMA, polycarbonate, ZnS, ZnO, Si 3 N 4 , and Nb 2 O 5 .

[0011] According to an embodiment of the present invention, the material of the above-mentioned first metasurface array includes SiO 2 , Ta 2 O 5 , TiO 2 , ITO, AZO, PMMA, polycarbonate, ZnS, ZnO, Si 3 N 4 , and Nb 2 O 5 .

[0012] According to an embodiment of the present invention, the material of the above-mentioned second metasurface array includes SiO 2 , Ta 2 O 5 , TiO 2 , ITO, AZO, PMMA, polycarbonate, ZnS, ZnO, Si 3 N 4 , and Nb 2 O 5 .

[0013] According to an embodiment of the present invention, the above-mentioned first metasurface array is a rectangular column array with a birefringence effect or an elliptical column array with a birefringence effect.

[0014] According to an embodiment of the present invention, the above-mentioned second metasurface array is a rectangular column array with a birefringence effect or an elliptical column array with a birefringence effect.

[0015] According to an embodiment of the present invention, the above-mentioned first metasurface array includes a plurality of first unit structures; the plurality of first unit structures are arranged in an array; the maximum size of each first unit structure is less than the working wavelength of the above-mentioned metasurface beam splitter.

[0016] According to an embodiment of the present invention, the second metasurface array includes a plurality of second unit structures; the plurality of second unit structures are arranged in an array; the maximum size of each second unit structure is less than the operating wavelength of the metasurface beam splitter.

[0017] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0018] The present invention discloses a metasurface beam splitter, which realizes precise phase addition and differential deflection angle control of two beams of light by making full use of the excellent capabilities of the metasurface in functional integration and wavefront manipulation, enabling them to refract in two different directions. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a schematic structural diagram of the metasurface beam splitter of the present invention;

[0021] Figure 2 It is a schematic diagram of the metasurface beam splitter of the present invention for processing circularly polarized light;

[0022] Figure 3 It is a schematic diagram of the shape of the metasurface array of the metasurface beam splitter of the present invention.

[0023] Description of the Reference Numerals:

[0024] Substrate - 1, First metasurface array - 2, Second metasurface array - 3. Detailed Embodiments

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] The emergence of metasurfaces provides a new solution for the miniaturization and multifunctionalization of photonic integrated systems. With its ability to freely control electromagnetic waves, as well as its significant advantages such as small size, light weight, and easy integration, metasurfaces have shown great potential in the research and development of micro-nano optical devices. This feature makes metasurfaces an ideal choice for the development of on-chip integrated micro-nano beam splitters, providing new possibilities for the miniaturization and functionalization of optical systems.

[0027] The purpose of the present invention is to provide a metasurface beam splitter, aiming to achieve miniaturization and multifunctionality of the optical system of the beam splitter.

[0028] The core of the present invention is to cleverly use metasurface technology to achieve efficient beam processing and regulation. The present invention uses metasurfaces to achieve beam splitting while separately regulating two beams of light. For one of the beams of light, the required polarization characteristics can be given when it exits the metasurface; for the other beam of light, off-axis focusing can be achieved when it exits the metasurface. The present invention uses metasurfaces to achieve miniaturization and multifunctionality of the optical system of the beam splitter.

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] like Figure 1 As shown, the metasurface beam splitter in this embodiment includes: a substrate 1 and a metasurface array; the metasurface array includes a first metasurface array 2 and a second metasurface array 3.

[0031] The first metastructure array 2 and the second metastructure array 3 are arranged on the same side of the substrate 1 and are cross-arranged; the incident light is incident from one side of the substrate 1, passes through the substrate 1 and the metastructure array in sequence, and then emits the first target light beam and the second target light beam with different emission angles.

[0032] The first metastructure array 2 is used to adjust the phase of the light beam emitted from the other side opposite to one side of the substrate 1, and emit a first target light beam with polarization characteristics; the second metastructure array 3 is used to adjust the phase of the light beam emitted from the other side opposite to one side of the substrate 1, and focus the adjusted light beam to the target position, so as to obtain a second target light beam with off-axis focusing characteristics.

[0033] In practical applications, the substrate 1 includes an upper surface and a lower surface opposite to the upper surface. The first metastructure array 2 and the second metastructure array 3 can be arranged on the upper surface or on the lower surface at the same time; the first metastructure array 2 and the second metastructure array 3 are cross-arranged on the upper surface or the lower surface.

[0034] When the first metastructure array 2 and the second metastructure array 3 are simultaneously arranged on the upper surface, the incident light is incident from the lower surface of the substrate 1; when the first metastructure array 2 and the second metastructure array 3 are simultaneously arranged on the lower surface, the incident light is incident from the upper surface of the substrate 1; when the incident light is incident from the upper surface, it is emitted from the lower surface; when the incident light is incident from the lower surface, it is emitted from the upper surface; the emitted incident light is incident on the first metastructure array 2 and the second metastructure array 3.

[0035] The phase of the incident light incident to the first metastructure array 2 changes after passing through the first metastructure array 2, and a phase shift is generated with respect to the phase of the incident light incident to the substrate 1. The value of the generated phase shift is related to the modulus of the wave vector of the incident light incident to the first metastructure array 2, the effective refractive index of the first metastructure array 2, and the height of the first metastructure array 2.

[0036] The phase of the incident light incident to the second metastructure array 3 changes after passing through the second metastructure array 3, and a phase shift is generated with respect to the phase of the incident light incident to the substrate 1. The value of the generated phase shift is related to the modulus of the wave vector of the incident light incident to the second metastructure array 3, the effective refractive index of the second metastructure array 3, and the height of the second metastructure array 3. The incident light with the phase shift will be focused on a point, which is an off-axis position.

[0037] As a specific implementation, the transmittance of the materials of the substrate 1, the first meta-array 2, and the second meta-array 3 in the visible light band is greater than the preset transmittance. Specifically, the substrate 1, the first meta-array 2, and the second meta-array 3 are all made of materials with high transmittance in the visible light band. The materials of the substrate 1, the first meta-array 2, and the second meta-array 3 all include SiO 2 、 2 O 5 、TiO 2 、ITO、AZO、PMMA、pc(Polycarbonate),ZnS、ZnO、Si 3 N 4 and Nb 2 O 5 .

[0038] Furthermore, the substrate 1 is a transparent substrate. The material of the substrate 1 can be SiO 2 、 2 O 5 、TiO 2 , ITO, AZO, PMMA, polycarbonate, ZnS, ZnO, Si 3 N 4 and Nb 2 O 5 The material of the first meta-array 2 may be SiO 2 、 2O 5 、TiO 2 、ITO, AZO, PMMA polycarbonate, ZnS, ZnO, Si 3 N 4 and Nb 2 O 5 One of those in 2 , the material of the second metasurface array 3 can be SiO 2 、Ta 2 O 5 、TiO 2 、ITO, AZO, PMMA polycarbonate, ZnS, ZnO, Si3N4 and Nb 2 O 5 One of those. To ensure the efficient regulation of electromagnetic waves by the metaelement, the refractive index of the first metasurface array should be greater than or equal to that of the substrate, and the refractive index of the second metasurface array should be greater than or equal to that of the substrate. The materials of the substrate 1, the first metasurface array 2, and the second metasurface array 3 can be the same or different.

[0039] As a specific implementation, the first metasurface array 2 is a rectangular column array with birefringence effect or an elliptical column array with birefringence effect. The second metasurface array 3 is a rectangular column array with birefringence effect or an elliptical column array with birefringence effect.

[0040] Furthermore, the first metasurface array 2 can be composed of one or more first unit structures; the multiple first unit structures are distributed in an array; the maximum size of each first unit structure is less than the working wavelength of the metasurface beam splitter. The second metasurface array 3 can be composed of one or more second unit structures; the multiple second unit structures are distributed in an array; the maximum size of each second unit structure is less than the working wavelength of the metasurface beam splitter.

[0041] The first metasurface array 2 includes multiple columns of first metasurface sets, and each column of first metasurface sets includes the same number of first unit structures. The second metasurface array 3 includes multiple columns of second metasurface sets, and each column of second metasurface sets includes the same number of second unit structures. Among them, the first metasurface array 2 and the second metasurface array 3 are cross - arranged on the substrate, which means that there is a column of second metasurface sets between two adjacent columns of first metasurface sets.

[0042] In practical applications, when the first unit structure is a rectangular column, the dimensions of the length and width of the rectangular column are both less than the working wavelength of the metasurface beam splitter. When the first unit structure is an elliptical column, the dimensions of the major axis and minor axis of the bottom surface of the elliptical column are both less than the working wavelength of the metasurface beam splitter.

[0043] When the second unit structure is a rectangular column, the dimensions of the length and width of the rectangular column are both smaller than the operating wavelength of the metasurface beam splitter. When the second unit structure is an elliptical cylinder, the dimensions of the major axis and minor axis of the bottom surface of the elliptical cylinder are both smaller than the operating wavelength of the metasurface beam splitter.

[0044] The metasurface of the present invention exhibits powerful functional integration characteristics through the cross-distribution design of unit structures. Based on the phase gradient satisfying extraordinary refraction, polarization characteristics are added to one of the light beams. When light passes through the metasurface, by selecting unit structures with a phase difference between the x-direction and the y-direction stabilized at π, the polarization characteristics of linearly polarized light and circularly polarized light can be adjusted. When s-polarized light passes through the metasurface, the first metasurface array 2 is responsible for precisely controlling the deflection of the reference beam and simultaneously generating the required phase difference. At this time, the outgoing light becomes p-polarized light; while the second metasurface array 3 focuses on the dual processing of deflecting and focusing the object beam, achieving the flexibility and precision of beam manipulation. Finally, the outgoing light in this part has the characteristics of off-axis focusing.

[0045] As Figure 2 shown, the present invention also demonstrates the application potential of the metasurface in processing circularly polarized light. When the incident light is left-handed circularly polarized light, the metasurface can convert the incident light into right-handed circularly polarized light and endow it with a specific deflection angle to achieve outgoing. At the same time, the other beam of light is guided to an off-axis position for focusing, further broadening the application scenarios and functional diversity of the metasurface.

[0046] As Figure 3 shown, the shape selection of the first unit structure and the second unit structure of the present invention has diversity, providing more possibilities for the customized design of the metasurface. By flexibly selecting the first unit structure or the second unit structure with different shapes, the performance of the metasurface can be further optimized to meet a wider range of application requirements. For example, the shapes of the first unit structure and the second unit structure can include cones, triangular pyramids, frustums of pyramids, and other combined shapes, etc. Among them, the combined shapes can be T-shaped columns, cross-shaped columns, etc. composed of two rectangular columns.

[0047] In addition, the beam splitter provided by the present invention can be designed and applied in various bands, such as ultraviolet, infrared, microwave and other bands. The beam splitter of the present invention can also achieve extraordinary refraction at various deflection angles, and can adjust the polarization characteristics and design different focal positions according to different design requirements. Through the above design, the present invention can obtain a multifunctional metasurface beam splitter with polarization control, off-axis focusing and parallel outgoing.

[0048] The design principle of the metasurface beam splitter provided by the present invention is described below, specifically as follows:

[0049] According to the principle of the generalized Snell's law, as Figure 1As shown, when the incident light passes through the metasurface, it is split into two beams of light that exit at different deflection angles. The polarization characteristics of one of the beams of light change significantly, and its polarization direction forms an orthogonal relationship with the polarization direction of the original incident light; while the other beam of light exhibits the unique property of off-axis focusing after passing through the metasurface.

[0050] The core principle of metasurface design lies in the ingenious manipulation of the spatial layout and arrangement of the unit geometric forms of the microstructure units of the metasurface, thereby introducing field discontinuities at the metasurface interface and further achieving precise control of the wavefront of the reflected or refracted light beam. Figure 1 Intuitively demonstrates the functional mechanism of the all-dielectric metasurface. When the incident light penetrates the metasurface, it causes the Mie resonance effect with the metasurface unit as the dielectric unit, which significantly adjusts the effective refractive index of the metasurface unit and further induces a specific phase delay. This process can be explained by the truncated waveguide effect of the metasurface unit:

[0051]

[0052] Among them, represents the phase shift introduced by the transmission phase; k 0 is the modulus of the wave vector; n eff represents the effective refractive index of the unit waveguide of the metasurface; H is the height of the metasurface. According to the generalized Snell's law, the deflection angles of the two emerging light beams can be accurately described by the following mathematical expressions:

[0053]

[0054] Among them, θ 1 is the exit angle of the transmitted light, θ 2 is the exit angle of the reflected light, θ i , is the angle of the incident light; n t , n r , n i correspond to the refractive indices of the transmission medium, the reflection medium, and the incident medium respectively; reflects the spatial change rate of the phase gradient at the metasurface interface, and λ represents the incident wavelength.

[0055] In the present invention, the microstructure unit, the unit waveguide, the dielectric unit, the meta-surface unit, and the unit structure are all the first unit structures in the first metasurface array or the second unit structures in the second metasurface array, representing the unit structures at different (x, y) positions. The sub-wavelength array and the all-dielectric metasurface represent many sets of unit structures. Therefore, both the first metasurface array and the second metasurface array are arrays of unit structures, and can also be said to be a metasurface.

[0056] The generalized Snell's law forms the theoretical basis for the design of beam splitters. Among them, meta - surface units with different phase gradients are carefully arranged adjacent to each other to achieve diverse beam deflection angles. The metasurface beam splitter designed in this invention has multiple functions. When parallel light with s - polarization is incident on the metasurface, two beams of light are emitted from the metasurface, and the two beams of light travel along different deflection paths respectively. In this invention, the incident light is taken as an example of parallel light with s - polarization. One beam of light emitted from the metasurface is equivalent to imposing an overall π - phase difference on the incident s - polarized light, adjusting the polarization characteristic of this beam of light to become p - polarized light perpendicular to the incident s - polarized light, and this p - polarized light is still parallel light. For the other beam of light emitted from the metasurface, while achieving abnormal deflection, it is also given an additional focusing phase distribution, that is, the off - axis focusing effect is achieved. The specific realization of the off - axis focusing effect depends on the following focusing formula:

[0057]

[0058] where represents the phase that the unit structure at different (x, y) positions needs to satisfy, λ represents the wavelength of the incident s - polarized light, f represents the focal length in the z - direction, and (x0, y0, f) represents the focal position of the other beam of light in space.

[0059] The core of this invention is that only the metasurface is required to achieve the deflection and splitting of the incident light. The first metasurface array 2 realizes the change of the polarization characteristic of the incident light; the second metasurface array 3 realizes the off - axis focusing of the incident light. This invention makes full use of the powerful electromagnetic wave regulation ability of the metasurface, and greatly expands its application scope and functional diversity on the basis of the traditional beam splitter. For the two beams of light emitted at different deflection angles, unique functional characteristics are respectively given to them. This innovation not only opens up new application prospects for functional beam splitters, but also provides an important research direction for the miniaturization, functionalization and integrated design of optical systems.

[0060] The present invention aims to address the problems of large-scale and difficult integration faced by traditional beam splitters, and realizes the miniaturization and multifunctionality of beam splitters by introducing metasurfaces. The core of the present invention is to cleverly utilize the ability of metasurfaces to accurately and efficiently control the electromagnetic properties of light waves, and on this basis realize the multifunctionality of beam splitters. Specifically, the present invention draws on the advanced design concept of Huygens electromagnetic metasurfaces, and carefully selects medium artificial atoms with high transmittance and flexible phase control as the basic units for constructing metasurfaces. Among them, the first metaarray 2 and the second metaarray 3 realize precise beam splitting of the incident light, splitting the incident light into two beams, and through the fine control of their structures, one beam of light is given polarization characteristics, and the other beam of light is converged. This design cleverly solves the function of the beam splitter that requires multiple optical elements to work together to achieve, greatly improving the integration and efficiency of the system.

[0061] In summary, the introduction of the present invention provides a new idea for the large-scale and integrated problems of beam splitters in optical systems, and proposes a multifunctional metasurface. The selected dielectric material effectively reduces energy loss due to its high transmittance characteristics, and its relatively simple processing technology provides a new method with great potential for realizing multifunctional sub-surface devices and further simplifying optical systems. This compact and efficient multifunctional beam splitter based on metasurfaces not only demonstrates the great potential for realizing new compact optical systems, but also makes important contributions to promoting the development of functional integrated photonic applications based on metasurfaces. It indicates that future optical systems will take a new step in terms of performance improvement, size reduction and functional diversification.

[0062] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A metasurface beam splitter, characterized in that: The beam splitter comprises: a substrate and a superstructure array; The superstructure array includes a first superstructure array and a second superstructure array; The first metastructure array and the second metastructure array are arranged on the same side of the substrate and are arranged crosswise; The incident light is incident from one side of the substrate, and after passing through the substrate and the metastructure array in sequence, emits a first target light beam and a second target light beam with different emission angles; The first metastructure array is used to adjust the phase of the light beam emitted from the other side opposite to the one side of the substrate to emit a first target light beam with polarization characteristics; The second metaarray is used to adjust the phase of the light beam emitted from the other side opposite to the one side of the substrate, and focus the adjusted light beam to a target position to obtain a second target light beam with off-axis focusing characteristics.

2. The metasurface beam splitter according to claim 1, characterized in that: The transmittance of the materials of the substrate, the first metaarray and the second metaarray in the visible light band is greater than a preset transmittance.

3. The metasurface beam splitter according to claim 1, characterized in that: The substrate is a transparent substrate.

4. The metasurface beam splitter according to claim 1, characterized in that: Materials of the substrate include SiO2, Ta2O5, TiO2, ITO, AZO, PMMA, polycarbonate, ZnS, ZnO, Si3N4 and Nb2O5.

5. The metasurface beam splitter according to claim 1, characterized in that: Materials of the first superstructure array include SiO2, Ta2O5, TiO2, ITO, AZO, PMMA, polycarbonate, ZnS, ZnO, Si3N4 and Nb2O5.

6. The metasurface beam splitter according to claim 1, characterized in that: Materials of the second superstructure array include SiO2, Ta2O5, TiO2, ITO, AZO, PMMA, polycarbonate, ZnS, ZnO, Si3N4 and Nb2O5.

7. The metasurface beam splitter according to claim 1, characterized in that: The first metastructure array is a rectangular column array with a birefringence effect or an elliptical column array with a birefringence effect.

8. The metasurface beam splitter according to claim 1, wherein: The second metastructure array is a rectangular column array with a birefringence effect or an elliptical column array with a birefringence effect.

9. The metasurface beam splitter according to claim 1, characterized in that: The first metasurface array includes one or more first unit structures; the multiple first unit structures are distributed in an array; the maximum size of each first unit structure is smaller than the operating wavelength of the metasurface beam splitter.

10. The metasurface beam splitter according to claim 1, wherein: The second metasurface array includes one or more second unit structures; the multiple second unit structures are distributed in an array; and the maximum size of each second unit structure is smaller than the operating wavelength of the metasurface beam splitter.

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