Multifunctional optical regulation and control device of metasurface embedded photonic crystal and preparation method of multifunctional optical regulation and control device

Abstract

A multifunctional optical regulation and control device of a metasurface embedded photonic crystal comprises a topological photonic crystal structure which is composed of dielectric units arranged periodically and used for supporting momentum space topological singular points and a bound state (BIC) in a continuous spectrum and providing a robust optical mode; the embedded metasurface is integrated in the dielectric unit of the topological photonic crystal structure, geometric parameters of the embedded metasurface are adjustable, and the embedded metasurface is used for regulating and controlling polarization, phase and non-Hermite characteristics of a light field through local perturbation; and the substrate is used for bearing the topological photonic crystal structure and the embedded metasurface. According to the multifunctional optical regulation and control device, after the metasurface is embedded into the topological photonic crystal, the original topological characteristics can be kept from being damaged. The metasurface is combined with the topological photonic crystal, so that the integration of multifunctional integration and topological robustness of a single optical device is realized. High-precision light field control is achieved in an integrated device, the requirement for compactness of a free space is met, and the application of the device in vortex generation and topological optics is expanded.

Description

Technical Field

[0001] The invention relates to a topological photonic device, and in particular to a multifunctional optical control device of a super-surface embedded photonic crystal and a preparation method thereof. Background Art

[0002] In recent years, topological photonics has attracted widespread attention due to its unique robust transmission properties. Traditional photonic crystal structures can form photonic band gaps through periodic dielectric modulation, supporting special optical modes including bound states (BICs) in the continuous spectrum. As a non-radiative state with infinite quality factor, BIC appears as a topological singularity in momentum space, usually accompanied by the generation of polarization vortices. This topological protection property makes BIC extremely resistant to structural defects and environmental perturbations, providing new possibilities for the construction of high-stability optical devices. However, traditional BIC-based topological photonic devices often have a single function and are difficult to achieve dynamic regulation, which severely limits their application in integrated optical systems.

[0003] On the other hand, as an artificial material composed of subwavelength structures, metasurfaces can flexibly control properties such as light wavefront, polarization, and phase through carefully designed nanostructured units. Typical metasurface devices include polarization converters, superlenses, and holographic elements. Although metasurfaces show great potential in multifunctional optical control, due to the lack of inherent topological protection mechanisms, their performance is easily affected by manufacturing errors and external environments, leading to stability problems in practical applications.

[0004] In the existing technology, researchers have tried to combine metasurfaces with photonic crystals to balance functional diversity and robustness. For example, additional light field control functions are achieved by attaching a metasurface structure to the surface of a photonic crystal. However, this simple stacking design often leads to mode mismatch between the two structures, which not only makes it difficult to maintain the topological properties of the photonic crystal, but also introduces additional insertion loss. More importantly, this discrete design cannot achieve the coordinated optimization of topological properties and metasurface control functions, resulting in limited device performance.

[0005] Therefore, it is urgent to develop a new type of optical control device that can truly integrate the robustness of topological photonic crystals with the multifunctional control capabilities of metasurfaces, and realize diversified functions such as chiral control, wavefront engineering, and singular point generation while maintaining the topological protection characteristics. Such a device needs to solve the following key technical problems: (1) How to embed the metasurface structure without destroying the topological properties of photonic crystals; (2) How to achieve the synergy between topological patterns and metasurface control; (3) How to achieve integrated integration of the structure through a scalable preparation process.

[0006] It should be noted that the information disclosed in the above background technology section is only used for understanding the background of the present application, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the invention

[0007] The main purpose of the present invention is to overcome the defects existing in the above-mentioned background technology and provide a multifunctional optical control device of a metasurface embedded photonic crystal and a preparation method thereof.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A multifunctional optical control device of a metasurface embedded photonic crystal, comprising:

[0010] Topological photonic crystal structures, consisting of periodically arranged dielectric units, are used to support topological singularities in momentum space and bound states (BICs) in the continuum, providing robust optical modes;

[0011] An embedded metasurface, integrated in the dielectric unit of the topological photonic crystal structure, with adjustable geometric parameters, used to control the polarization, phase and non-Hermitian properties of the light field through local perturbations;

[0012] A substrate supports the topological photonic crystal structure and the embedded metasurface.

[0013] A method for preparing the multifunctional optical control device of the metasurface embedded photonic crystal comprises the following steps:

[0014] forming a periodic photonic crystal structure pattern on a dielectric substrate by electron beam lithography;

[0015] The photonic crystal structure and the super-surface groove unit embedded therein are processed simultaneously by using a reactive ion etching process to achieve integrated molding;

[0016] The geometric parameters of the metasurface groove unit are adjustable, and the integration of the photonic crystal topological characteristics and the metasurface control function is achieved through a single photolithography process.

[0017] The present invention has the following beneficial effects:

[0018] The multifunctional optical control device of the metasurface embedded photonic crystal of the present invention integrates the embedded metasurface with adjustable geometric parameters into the topological photonic crystal structure composed of periodic dielectric units, and only introduces local perturbations to maintain the infinite high quality factor and momentum space topological vortex of the topological photonic crystal, thereby achieving topological robustness. At the same time, the metasurface and the topological photonic crystal work together to achieve multifunctional optical responses such as chirality control, phase gradient wavefront deflection and Jones matrix singular point generation, breaking through the single function limitation of traditional topological photonic devices, and achieving stable generation of wavefront deflection and topological vortex, which can be applied to holographic display, virtual imaging, multi-channel vortex optical communication, non-Hermitian optical sensing and other fields. In addition, the device does not require complex external field control elements, has the characteristics of free space compactness and lightweight, is suitable for on-chip integration and free space optical systems, and greatly expands its scope of application. The specific advantages include the following aspects:

[0019] (1) Multifunctional integration: A single device can stably realize wavefront deflection and topological vortex generation simultaneously, breaking through the single function limitation of traditional topological photonic devices and having multiple applications such as holographic display and virtual imaging.

[0020] (2) Topological robustness: The embedded metasurface only introduces local perturbations, while still maintaining the characteristics of topological photonic crystals: infinite high quality factor and topological vortex characteristics in momentum space.

[0021] (3) Free-space compactness and lightweight: No large and complex optical components or waveguide structures are required for external field control, which is suitable for on-chip integration and free-space optical systems.

[0022] (4) Application expansion: It can be applied to multi-channel vortex optical communication, non-Hermitian optical sensing and other fields.

[0023] Other beneficial effects of the embodiments of the present invention will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the metasurface embedded photonic crystal structure and phase gradient control according to an embodiment of the present invention.

[0025] Figure 2 This is an actual scanning electron microscope image of the embodiment of the present invention after micro-nano processing.

[0026] Figure 3 This is a far-field cross-polarized light beam deflection test diagram of an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram of the coexistence of topological vortex and phase gradient in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope and application of the present invention.

[0029] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for fixing as well as for coupling or communication.

[0030] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0031] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0032] See also Figure 1 The embodiment of the present invention provides a multifunctional optical control device of a metasurface embedded photonic crystal, comprising: a topological photonic crystal structure 1, which is composed of periodically arranged dielectric units, and is used to support topological singularities in momentum space and bound states (BICs) in a continuous spectrum, and provide robust optical modes; an embedded metasurface 2, which is integrated in the dielectric units of the topological photonic crystal structure 1, and has adjustable geometric parameters, and is used to control the polarization, phase and non-Hermitian characteristics of the light field through local perturbations; a substrate 3, which carries the topological photonic crystal structure 1 and the embedded metasurface 2, and provides mechanical support. The device is a compact free-space optical structure. The embedded metasurface 2 works synergistically with the topological photonic crystal structure 1 to achieve multifunctional optical responses of chirality control, phase gradient wavefront deflection and Jones matrix singular point generation while maintaining topological protection characteristics.

[0033] In some embodiments, the embedded metasurface 2 includes a rotatable metasurface unit, which realizes the conversion of the polarization state from linear to circular polarization by adjusting the rotation angle (φ), and forms a chiral BIC near the Γ point.

[0034] In some embodiments, the embedded metasurface 2 is an anisotropic structure, which forms a 90° Pancharatnam-Berry phase gradient through spatial gradient arrangement to achieve deflection control of cross-polarized light beams while retaining the topological vortex characteristics of the momentum space.

[0035] In some embodiments, the combination of the embedded metasurface 2 and the topological photonic crystal structure 1 can generate chiral singular points in the Jones matrix, achieving the coexistence of polarization conversion singularity and topological BIC, wherein the RL / LR components of the reflected Jones matrix exhibit divergent characteristics.

[0036] In some embodiments, the topological photonic crystal structure 1 is a periodic array of square columns with a period of 320nm and a column side length of 260nm; the embedded metasurface 2 is a rectangular groove structure with a length and width of 80nm and 40nm respectively, which is integrated with the photonic crystal structure through electron beam lithography and reactive ion etching processes.

[0037] In some embodiments, the embedded metasurface 2 unit is a groove structure, and its cross-sectional shape is selected from one or more combinations of rectangle, circle or trapezoid; the geometric parameters of the groove structure include depth, aspect ratio and rotation angle (φ), and the local light field distribution can be precisely controlled by adjusting the geometric parameters while maintaining the overall topological characteristics of the photonic crystal structure.

[0038] The embodiment of the present invention further provides a method for preparing the multifunctional optical control device of the metasurface embedded photonic crystal, comprising the following steps:

[0039] forming a periodic photonic crystal structure pattern on a dielectric substrate by electron beam lithography;

[0040] The photonic crystal structure and the super-surface groove unit embedded therein are processed simultaneously by using a reactive ion etching process to achieve integrated molding;

[0041] The geometric parameters of the metasurface groove unit are adjustable, and the integration of the photonic crystal topological characteristics and the metasurface control function is achieved through a single photolithography process.

[0042] In some embodiments, the cross-sectional shape of the supersurface groove unit is selected from at least one of a rectangle, a circle or a trapezoid.

[0043] In some embodiments, the single photolithography process includes:

[0044] First, the photonic crystal periodic structure and the metasurface groove pattern are simultaneously defined on the photoresist by electron beam lithography.

[0045] Reactive ion etching is then used to transfer the pattern to the dielectric substrate.

[0046] Form an integrated structure that has both topological protection characteristics and multifunctional optical regulation capabilities.

[0047] In some embodiments, by adjusting the rotation angle φ, aspect ratio and depth parameters of the groove unit, coordinated regulation of the polarization state, phase distribution and non-Hermitian characteristics of the light field is achieved.

[0048] The multifunctional optical control device of the metasurface embedded photonic crystal proposed in the present invention can keep the original topological characteristics intact after the metasurface is embedded in the topological photonic crystal. By combining the metasurface with the topological photonic crystal, the integration of multifunctional integration of a single optical device (such as dynamic adjustability and coordinated control of multiple physical fields) and topological robustness is achieved. The present invention realizes high-precision light field manipulation in integrated devices, meets the demand for free space compactness, and expands its application in vortex generation and topological optics.

[0049] The specific embodiments of the present invention are further described below.

[0050] Embodiment 1:

[0051] Multifunctional optical control devices of metasurface embedded photonic crystals include:

[0052] 1. Base material.

[0053] 2. Topological photonic crystal structure: A square dielectric column array with a period of 320nm is prepared on a substrate. The side length of a single dielectric column is 260nm. This structure supports the Γ-point BIC mode near the wavelength of 1550nm, which manifests as a polarization vortex in momentum space.

[0054] 3. Embedded metasurface: A rectangular groove is machined at the center of each square dielectric column as a metasurface unit. The groove size is 80nm×40nm and the depth is 60nm. The long axis direction of the groove can be rotated, and the rotation angle φ can be adjusted in the range of 0-90°. Make the Bailey phase gradient satisfy Δφ=90°, such as Figure 1 The actual scanning electron microscope image of micro-nano processing is shown in Figure 2 shown.

[0055] The cross-sectional shape of the groove structure can be selected to be rectangular, circular or trapezoidal, and multi-parameter regulation can be achieved by adjusting the aspect ratio (1:1 to 3:1, such as 2:1) and depth (50-100nm).

[0056] Chirality control is achieved by adjusting the rotation angle of the metasurface unit:

[0057] When all metasurface units are rotated by an angle of φ = 30°, the system generates a circularly polarized BIC near the Γ point, and the Stokes parameter S3 ≈-1, corresponding to the left-handed circular polarization state. Through electron beam exposure and reactive ion etching processes, regional arrays with different rotation angles can be prepared on the same chip The spatial encoding of polarization state is realized. Experiments confirm that the structure has an extremely high quality factor at the Γ point, verifying the maintenance of topological protection characteristics.

[0058] Wavefront control is achieved by gradient arrangement of metasurface units:

[0059] The rotation angle of adjacent hypersurface units is φ 1 =0°、φ 2 =30°,φ 3 =60°、φ 4 =90°, forming a 90° Pancharatnam-Berry phase gradient. The deflection angle of the cross-polarized beam was measured to be 90°, and momentum space imaging confirmed the coexistence of the phase gradient and the topological vortex. Momentum space measurements confirmed that while the beam deflection was achieved, the topological vortex characteristics of the Γ point remained unchanged.

[0060] Achieving singularities by optimizing metasurface parameters:

[0061] When the embedded rectangular hole is rotated at a certain angle, the RL and LR components of the Jones matrix are observed to diverge. Eigenvalue analysis confirms the existence of a chiral singular point at this wavelength, while the BIC mode at the Γ point remains stable.

[0062] Preparation process:

[0063] The period is 320nm, the side length of the square column is 260nm, and the length and width of the rectangular groove are 80nm and 40nm respectively.

[0064] The rectangular groove metasurface can control the field distribution by rotating the angle φ, and the gradient is rotated at different angles (φ 1 to φ, represents the rotation angle of the nth metasurface unit) so that the Bailey phase gradient satisfies Δφ=90°, such as Figure 1 shown.

[0065] Based on electron beam lithography (EBL) and reactive ion etching (RIE) processes, periodic dielectric structures (such as square column arrays) are used as topological photonic crystals, and adjustable groove structures (such as rectangular, circular, and trapezoidal) are processed simultaneously to embed the metasurface units into the photonic crystals, and the integration of the metasurface and the photonic crystals is achieved through a single lithography. Changing the geometric parameters (rotation angle φ, aspect ratio, depth) can regulate the light field response, while maintaining the functions of the photonic crystals, achieving 1+1 integration of functions, and improving space utilization and multi-dimensionality.

[0066] Experimental verification

[0067] The results of physical field simulation, soft analysis and optical experimental tests show that for metasurfaces without rotation Measured far-field Stokes parameter S 3 = 0, and the polarization angle distribution shows the characteristics of a linear polarization vortex with a charge number of 1. The deflection angle of the cross-polarized beam was measured to be 90°, and the momentum space imaging confirmed the phase gradient (such as Figure 3 as shown) and coexist with topological vortices (as shown Figure 4 shown).

[0068] Topological protection (via photonic crystal periodicity) and multifunctional regulation (via metasurface parameter design) are achieved through single-shot lithography.

[0069] It should be noted that the above embodiments are only typical implementations of the present invention, and those skilled in the art can make various modifications and substitutions without departing from the concept of the present invention. For example, the shape of the dielectric column can be changed to a circular or hexagonal shape, and the depth of the metasurface groove can be adjusted within the range of 50-100nm, and these changes should be included in the protection scope of the present invention.

[0070] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target 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 the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A multifunctional optical control device of a metasurface embedded photonic crystal, characterized in that: include: Topological photonic crystal structures, consisting of periodically arranged dielectric units, are used to support topological singularities in momentum space and bound states (BICs) in the continuum, providing robust optical modes; An embedded metasurface, integrated in the dielectric unit of the topological photonic crystal structure, with adjustable geometric parameters, used to control the polarization, phase and non-Hermitian properties of the light field through local perturbations; A substrate supports the topological photonic crystal structure and the embedded metasurface.

2. The multifunctional optical control device of the metasurface embedded photonic crystal according to claim 1, characterized in that: The embedded metasurface includes a rotatable metasurface unit, which can realize the conversion of the polarization state from linear to circular polarization by adjusting the rotation angle (φ) and form a chiral BIC near the Γ point.

3. The multifunctional optical control device of the metasurface embedded photonic crystal according to claim 1 or 2, characterized in that: The embedded metasurface is an anisotropic structure, which forms a 90° Pancharatnam-Berry phase gradient through spatial gradient arrangement, realizes the deflection control of the cross-polarized light beam, and retains the topological vortex characteristics of the momentum space.

4. The multifunctional optical control device of the metasurface embedded photonic crystal according to any one of claims 1 to 3, characterized in that: The combination of the embedded metasurface and the topological photonic crystal structure can generate chiral singular points in the Jones matrix, achieving the coexistence of polarization conversion singularities and topological BIC, wherein the RL / LR components of the reflected Jones matrix exhibit divergent characteristics.

5. The multifunctional optical control device of the metasurface embedded photonic crystal according to any one of claims 1 to 4, characterized in that: The topological photonic crystal structure is a periodic array of square columns with a period of 320nm and a column side length of 260nm; the embedded metasurface is a rectangular groove structure with a length and width of 80nm and 40nm respectively, which is integrated with the photonic crystal structure through electron beam lithography and reactive ion etching processes.

6. The multifunctional optical control device of the metasurface embedded photonic crystal according to any one of claims 1 to 5, characterized in that: The embedded metasurface unit is a groove structure, and its cross-sectional shape is selected from one or more combinations of rectangle, circle or trapezoid; the geometric parameters of the groove structure include depth, aspect ratio and rotation angle (φ), and precise control of the local light field distribution is achieved by adjusting the geometric parameters while maintaining the overall topological characteristics of the photonic crystal structure.

7. A method for preparing a multifunctional optical control device of a metasurface embedded photonic crystal according to any one of claims 1 to 6, characterized in that: The following steps are involved: forming a periodic photonic crystal structure pattern on a dielectric substrate by electron beam lithography; The photonic crystal structure and the super-surface groove unit embedded therein are processed simultaneously by using a reactive ion etching process to achieve integrated molding; The geometric parameters of the metasurface groove unit are adjustable, and the integration of the photonic crystal topological characteristics and the metasurface control function is achieved through a single photolithography process.

8. The preparation method according to claim 7, characterized in that: The cross-sectional shape of the supersurface groove unit is selected from at least one of a rectangle, a circle or a trapezoid.

9. The preparation method according to claim 7, characterized in that: The single photolithography process comprises: First, the photonic crystal periodic structure and the metasurface groove pattern are simultaneously defined on the photoresist by electron beam lithography. Reactive ion etching is then used to transfer the pattern to the dielectric substrate. Form an integrated structure that has both topological protection characteristics and multifunctional optical regulation capabilities.

10. The preparation method according to claim 7, characterized in that: By adjusting the rotation angle φ, aspect ratio and depth parameters of the groove unit, the coordinated control of the polarization state, phase distribution and non-Hermitian characteristics of the light field can be achieved.

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