An order control method and structure based on a metasurface blazed grating

Abstract

This invention discloses a method and structure for order control based on metasurface blazed gratings, relating to the field of metasurface technology. The method independently designs phase gradients for at least two wavelength bands within a single-layer metasurface, arranging two types of phase control units in an alternating manner. Utilizing the differences in the dispersion characteristics of these units, different equivalent phase distributions are formed in different wavelength bands. The diffraction order distribution in each wavelength band is independently controlled by adjusting the phase coverage. The structure includes a substrate and an alternating array of subwavelength nanopillars, achieving polarization-independent dual-band blazed control, capable of single-blazed, mixed-blazed, or dual-blazed operating modes. This invention uses single-crystal silicon nanopillars as control units, independently designed for the visible and near-infrared wavelengths, achieving efficient, spatially separated beam deflection control. The device is polarization-insensitive, suitable for natural light and arbitrary linearly polarized incident conditions, significantly improving practicality and environmental adaptability.

Description

Technical Field

[0001] This invention relates to the field of metasurface technology, and in particular to a method and structure for order control based on metasurface blazed gratings. Background Technology

[0002] Blazed gratings are fundamental optical devices for controlling wavelength dispersion and beam orientation, playing a crucial role in spectral analysis, hyperspectral imaging, and optical communication. By introducing a specific blaze angle, conventional blazed gratings can efficiently concentrate incident light energy to a predetermined diffraction order, achieving high-efficiency spectral separation and directional radiation. However, limited by their geometric configuration and material dispersion characteristics, conventional blazed gratings typically maintain high efficiency only within a limited wavelength band: blazed structures optimized for a specific center wavelength often exhibit significant efficiency drops in other bands. Furthermore, asymmetric trench structures not only introduce significant polarization sensitivity but also face challenges in morphology control during micro- and nano-scale fabrication. These inherent limitations restrict the further application of conventional blazed gratings in broadband, polarization-robust, and highly integrated optical systems.

[0003] In recent years, metasurface planar optics technology has achieved flexible control over the phase, amplitude, and polarization state of light fields through two-dimensional arrays composed of subwavelength artificial structural units, providing a new design paradigm for the miniaturization and functional integration of optical devices. Metagrating, which incorporates metasurfaces into grating design, achieves diffraction order control through phase engineering rather than geometric grooving. This extends the working mechanism of blazed gratings from geometric optics to wavefront manipulation at the subwavelength scale, providing a new path for compact beam deflection, spectral dispersion, and multifunctional wavefront shaping.

[0004] To overcome the limitations of single-layer supergratings in terms of degrees of freedom, various structural extension schemes have been proposed, such as using cascaded, bilayer, or multilayer metasurface structures to distribute phase modulation across different planes, thereby achieving multi-band or broadband operation. However, these schemes are usually accompanied by complex fabrication processes, stringent interlayer alignment requirements, and problems such as Fabry-Perot resonance, which to some extent increase the difficulty of device realization and system integration. Therefore, achieving multi-band, high-efficiency, and polarization-independent blazed diffraction in a single-layer, planar structure remains a challenging research topic.

[0005] Another commonly used wavefront modulation scheme is based on metasurfaces using the Pancharatnam–Berry (PB) geometric phase mechanism, where phase modulation is achieved through planar rotation of anisotropic nanostructures. Although PB metasurfaces can provide wavelength-independent geometric phase responses under ideal conditions, their performance typically depends on the polarization state of the incident light, and there is a coupling relationship between phase modulation and efficiency. Furthermore, the PB phase mechanism is mainly applicable to circularly polarized light, and still has significant limitations in achieving independent phase modulation across multiple wavelength bands and polarization-independent responses. Summary of the Invention

[0006] To achieve the above-mentioned objectives and other advantages of the present invention, a first objective of the present invention is to provide a method for order control based on metasurface blazed gratings, comprising the following steps: In a single-layer planar metasurface, independent phase gradients are designed for at least two different target operating bands; Phase control units designed for different target operating bands are arranged in an alternating manner to form a combined phase gradient metasurface. By utilizing the difference in dispersion characteristics of the phase modulation unit under different operating bands, the combined phase gradient metasurface can form different equivalent phase distributions in each target operating band. By adjusting the phase coverage within each target's working band, the distribution of transmitted energy among different diffraction orders can be controlled, thereby achieving independent control of the blaze behavior of each target's lower-order working band.

[0007] Furthermore, the control of the phase coverage refers to selecting the geometric parameters of the phase control unit to achieve near-complete 0-2π phase coverage in one target operating band to achieve a single blaze, or to achieve a phase coverage of less than 2π in another target operating band to achieve a dual blaze, thereby achieving dual-band hybrid blaze in the same device.

[0008] A second objective of this invention is to provide a structure based on a metasurface blazed grating for implementing the above-described method, comprising: A single-layer planar substrate; Multiple subwavelength nanopillars are arranged in an array on the substrate to form a metasurface; The plurality of subwavelength nanopillars include a first type of phase modulation unit and a second type of phase modulation unit; The first type of phase modulation unit is configured to provide a first linear phase gradient within the first target operating band; The second type of phase modulation unit is configured to provide a second linear phase gradient within the second target operating band; The first type of phase modulation unit and the second type of phase modulation unit are arranged in an alternating-staggered pattern in space, together forming a super-period, which is used to realize different equivalent grating periods and phase modulation characteristics in the first target working band and the second target working band, respectively, so as to independently control the diffraction order distribution in the two bands.

[0009] Furthermore, the nanopillar is an all-dielectric nanopillar with a circularly symmetrical cross-section to achieve polarization-independent propagation phase modulation.

[0010] Furthermore, the nanopillars are single-crystal silicon nanopillars.

[0011] Furthermore, the first target operates in a different wavelength band than the second target, and they are located in the visible light band and the near-infrared band, respectively.

[0012] Furthermore, the first target operating wavelength is 620-660nm, and the second target operating wavelength is 970-1010nm.

[0013] Furthermore, the contribution of the first type of phase modulation unit to the equivalent phase distribution of the combined phase gradient metasurface in the second target operating band is less than that of the second type of phase modulation unit; the contribution of the second type of phase modulation unit to the equivalent phase distribution in the first target operating band is less than that of the first type of phase modulation unit.

[0014] Furthermore, by adjusting the geometric parameters of the first type of phase control unit and the second type of phase control unit, the phase response of each unit in its non-target operating band can be continuously controlled, thereby controlling the equivalent phase coverage of the entire supercycle in the corresponding band, and realizing a continuous and controllable transition from a single blaze to a double blaze.

[0015] Furthermore, the structure is configured to implement at least one of the following operating modes: Dual-band single blaze mode: In both the first and second target operating bands, the concentration of transmitted energy in a single non-zero diffraction order is higher than that in any other diffraction order; Hybrid blaze mode: Within the first target operating band, the concentration of transmitted energy at the 0th order and one non-zero diffraction order is higher than the concentration at other diffraction orders; within the second target operating band, the concentration of transmitted energy at a single non-zero diffraction order is higher than the concentration at any other diffraction order; or, Dual-band dual-blaze mode: In the first target operating band and the second target operating band, the concentration of transmitted energy in the 0th order and one non-zero diffraction order is higher than that in other diffraction orders.

[0016] Furthermore, in the hybrid blaze mode, the diffraction order of energy concentration in the first target working band is -1, and the diffraction order of energy concentration in the second target working band is +1, thereby achieving diffraction modulation of opposite orders in the two bands.

[0017] Furthermore, the staggered arrangement allows the local phase distribution to exhibit segmented continuity within a single working band, while maintaining monotonic evolution on a global superperiodic scale, thereby suppressing undesigned diffraction orders and concentrating energy on the target diffraction orders.

[0018] Furthermore, the diameter of the nanopillar is in the range of 50-150 nm, and the transmission phase can be continuously controlled from 0 to 2π by adjusting the diameter.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention proposes a hierarchical control method and structural design based on metasurface blazed gratings. Using single-crystal silicon nanopillars as control units, the design is independently tailored for the visible light band (620-660 nm) and the near-infrared band (970-1010 nm), achieving efficient, spatially separated beam deflection control. The device is insensitive to polarization and is suitable for natural light and arbitrary linearly polarized incident conditions, significantly improving its practicality and environmental adaptability.

[0020] This invention introduces a dual-band independent phase gradient design mechanism into a single-layer planar metasurface, enabling phase modulation of different bands to coexist within the same physical structure without interfering with each other. This avoids the order crosstalk and energy aliasing problems commonly found in traditional multi-band schemes, thereby achieving high-fidelity separation of different spectral channels in the spatial dimension.

[0021] Compared to existing technologies that rely on multi-layer structures or cascaded multiple devices to achieve multi-band modulation, this invention can achieve dual-band blazed order modulation using a single-layer all-dielectric metasurface architecture, which significantly reduces device thickness and system complexity, and is beneficial for the miniaturization, integration and mass production of optical systems.

[0022] This invention realizes blazed diffraction behavior based on subwavelength scale phase engineering. Its diffraction characteristics are mainly determined by the phase response and spatial arrangement of the unit cells, rather than relying on the asymmetric groove geometry of traditional gratings. Thus, while maintaining high directional selectivity, it avoids the limitations of traditional blazed gratings in terms of processing accuracy, polarization sensitivity and band adaptability.

[0023] By using high-refractive-index, low-loss single-crystal silicon nanopillars as functional units, the metasurface device proposed in this invention has a stable transmission response and good phase continuity in the target operating band, which makes the energy distribution in the blaze order more concentrated, effectively suppresses non-target diffraction orders, and improves the directional stability of beam modulation and the system signal-to-noise ratio.

[0024] The single-layer metasurface structure proposed in this invention combines multi-band response, high directional output, polarization independence, and structural compactness. It is not only suitable for dual-band beam splitting, but can also be extended to applications such as tunable beam deflectors, on-chip spectrometers, broadband imaging systems, and optical neural networks with spectral selectivity. It provides a new path for building a miniaturized, highly integrated, and multifunctional photonics platform.

[0025] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0026] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram illustrating the working principle of metasurfaces. Figure 2 This is a schematic diagram of the staggered arrangement of dual-band phase gradient units; Figure 3 A working mechanism diagram for staggered and interleaved arrangement design; Figure 4 The phase distribution diagram of a single cell under dual-band blaze; Figure 5 The phase distribution diagram of the unit under dual-band hybrid blaze; Figure 6 The phase distribution diagram of the unit under dual-band dual-blazed conditions; Figure 7 This is a far-field distribution map of a single blaze in two bands; Figure 8 This is a far-field distribution map of a dual-band hybrid blaze; Figure 9 This is a far-field distribution map of the dual-band dual-blazed array; Figure 10 For metasurface processing flow Figure 1 ; Figure 11 For metasurface processing flow Figure 2 ; Figure 12 For metasurface processing flow Figure 3 ; Figure 13 For metasurface processing flow Figure 4 ; Figure 14The experimental diffraction results of the dual-band metasurface device under the key operating band are shown in the figure. Figure 15 Normalized diffraction efficiency diagrams for each order in the 570-1050nm band. Figure 16 A quantitative analysis diagram of the diffraction spot displacement characteristics with wavelength was provided. Detailed Implementation

[0027] The present invention will now be further described with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0028] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0030] To address the technical problems existing in the prior art, this invention proposes a single-layer, all-dielectric blazed supergrating design strategy. This structure utilizes the propagation phase introduced by circularly symmetric silicon nanopillars to achieve polarization-independent phase modulation, and supports independent phase responses between different operating bands through structural parameter design. By staggering nanopillar units optimized for different bands within a single-layer plane and further controlling the phase coverage within each band, the proposed design framework can realize multiple blazed operating modes in the same device, including single blazed, double blazed, and hybrid blazed modes.

[0031] Based on the above design concept, this invention conducted focused experimental verification of the hybrid blaze operating state. Experimental results show that the supergrating exhibits significantly different diffraction behaviors in different wavelength bands: in the shorter wavelength band (620–660 nm), the transmitted energy is mainly distributed in the 0th and −1st order diffraction channels, exhibiting stable partial blaze characteristics; while in the longer wavelength band (970–1010 nm), the diffraction energy is highly concentrated in the +1st order diffraction channel, corresponding to typical single blaze behavior. The coexistence of different blaze modes in the dual wavelength bands experimentally verifies the supergrating design principle combining phase coverage modulation and staggered arrangement. The specific scheme is as follows: Example 1 A structure based on metasurface blazed gratings, such as Figure 1 As shown, it includes: A single-layer planar substrate; Multiple subwavelength nanopillars are arranged in an array on the substrate to form a metasurface; The plurality of subwavelength nanopillars include a first type of phase modulation unit and a second type of phase modulation unit; The first type of phase modulation unit is configured to provide a first linear phase gradient within the first target operating band; The second type of phase modulation unit is configured to provide a second linear phase gradient within the second target operating band; The first type of phase modulation unit and the second type of phase modulation unit are arranged in an alternating-staggered pattern in space, together forming a super-period, which is used to realize different equivalent grating periods and phase modulation characteristics in the first target working band and the second target working band, respectively, so as to independently control the diffraction order distribution in the two bands.

[0032] In some embodiments, the nanopillar is an all-dielectric nanopillar with a circularly symmetric cross-section to achieve polarization-independent propagation phase modulation. Preferably, the nanopillar is a single-crystal silicon nanopillar. The diameter of the nanopillar is in the range of 50-150 nm, and the transmission phase can be continuously modulated from 0 to 2π by adjusting the diameter.

[0033] To achieve controllable beam deflection on the transmission side, this invention designs a dual-phase gradient metasurface composed of subwavelength silicon nanopillars, whose unit geometry parameters gradually vary along the spatial direction. By precisely controlling the geometry of each nanopillar unit, the transmission phase can be continuously adjusted and a linear phase gradient can be constructed, thereby guiding the outgoing wavefront to the target diffraction order. Its basic working principle is as follows: Figure 1 As shown, at two representative operating wavelengths ( and The opposite order of anomalous diffraction can be achieved under these conditions, and the corresponding experimental diffraction pattern is shown in the attached figure.

[0034] This embodiment performed parameter scanning on silicon nanopillars with diameters ranging from 50 to 150 nm. The results show that each unit exhibits a clear and continuous transmission phase response in both target operating wavelengths, with an overall phase coverage approaching the complete 0–2π range. Complete phase coverage is a key condition for achieving efficient blazed diffraction, as the phase difference between adjacent units must satisfy… , where m is the target diffraction order and N is the number of units within a supercycle. Only when the cumulative phase within a supercycle spans a complete 2π can the corresponding transmitted energy be effectively concentrated into the target diffraction channel, while simultaneously suppressing other undesigned diffraction orders.

[0035] This embodiment constructs a combined phase gradient metasurface structure, such as Figure 2 As shown, two types of metasurface units with different phase functions are introduced in the same plane. Preferably, the first target operating wavelength band and the second target operating wavelength band are different, and are located in the visible light band and the near-infrared band, respectively. Further, the contribution of the first type of phase modulation unit to the equivalent phase distribution of the combined phase gradient metasurface in the second target operating wavelength band is less than that of the second type of phase modulation unit; the contribution of the second type of phase modulation unit to the equivalent phase distribution in the first target operating wavelength band is less than that of the first type of phase modulation unit. That is, one type of unit provides an approximately linear phase gradient in the target operating wavelength band, serving as a phase modulation unit; the other type of unit has a small phase response change in the same wavelength band and can be regarded as a phase reference unit. Thanks to the dispersive properties of the nanostructure, these two types of units exhibit significantly different phase modulation capabilities in different wavelength bands. Further, the first target operating wavelength band is 620-660 nm, and the second target operating wavelength band is 970-1010 nm.

[0036] When phase modulation units and phase reference units are periodically multiplexed in a staggered-interleaved manner in space, the overall phase distribution no longer exhibits a simple continuous linear change, but rather forms an equivalent periodic phase modulation feature within an extended superperiodic scale. This equivalent phase distribution exhibits piecewise continuity at the local scale, while maintaining monotonic evolution at the global scale, thus exhibiting typical grating-type diffraction behavior in the far field. In other words, the staggered-interleaved arrangement ensures that the local phase distribution exhibits piecewise continuity within a single operating band, while maintaining monotonic evolution at the global superperiodic scale, thereby suppressing undesigned diffraction orders and concentrating energy on the target diffraction orders. It should be noted that the diffraction characteristics of this structure do not originate from traditional geometrically grooved gratings, but are jointly determined by the structural dispersion characteristics of the units and the spatial construction method of the phase gradient. The working mechanism of the staggered-interleaved arrangement design is as follows: Figure 3 As shown.

[0037] From a physical perspective, this structure can be viewed as a supergrating realized through phase engineering. By achieving an equivalent phase coverage close to 0–2π within the supercycle and reconstructing the equivalent grating period through staggered arrangement, this supergrating structure can effectively suppress parasitic diffraction orders and concentrate energy to the target diffraction orders. When the operating band switches, the modulation roles of different units interchange according to the dispersion characteristics, thereby achieving coordinated control of dual-band blazed diffraction within the same metasurface.

[0038] While maintaining the phase gradient construction method and staggered arrangement, the phase coverage in different wavebands can be continuously controlled by adjusting the combination of nanopillar geometric parameters, thereby significantly changing the distribution of transmitted energy among diffraction channels in the far field. Specifically, by adjusting the geometric parameters of the first and second type of phase control units, the phase response in their respective non-target operating wavebands can be continuously controlled, thereby controlling the equivalent phase coverage of the entire supercycle in the corresponding waveband, achieving a continuous and controllable transition from single blaze to double blaze. Specifically, the structure is configured to achieve at least one of the following operating modes: Dual-band single blaze mode: In both the first and second target operating bands, the concentration of transmitted energy in a single non-zero diffraction order is higher than that in any other diffraction order; Hybrid blaze mode: In the first target operating band, the concentration of transmitted energy at the 0th order and one non-zero diffraction order is higher than the concentration at other diffraction orders; in the second target operating band, the concentration of transmitted energy at a single non-zero diffraction order is higher than the concentration at any other diffraction order; furthermore, in the hybrid blaze mode, the diffraction order in which energy is concentrated in the first target operating band is -1 order, and the diffraction order in which energy is concentrated in the second target operating band is +1 order, thereby achieving diffraction modulation of opposite orders in two bands.

[0039] Alternatively, dual-band dual-blaze mode: In the first and second target operating bands, the concentration of transmitted energy in the 0th order and one non-zero diffraction order is higher than that in other diffraction orders.

[0040] This invention presents the relative transmission phase distribution of three representative design schemes in the visible band (620–660 nm) and near-infrared band (970–1010 nm), as well as the far-field angle distribution at the representative wavelengths of the corresponding two working bands λ=640 nm and λ=990 nm.

[0041] When near-complete 0–2π phase coverage is achieved in both operating bands, such as Figure 4 As shown, under the condition of λ=640nm, the transmitted energy is mainly distributed to the −1st order diffraction; while under the condition of λ=990nm, the transmitted energy is mainly concentrated in the +1st order diffraction. At this time, both bands exhibit single blaze characteristics, corresponding to the dual-band single blaze operating state, and the far-field distribution is as follows. Figure 7 As shown.

[0042] When the phase coverage in the visible light band weakens, while the near-infrared band maintains a relatively ideal linear phase gradient, such as Figure 5As shown, the transmitted energy at λ=640nm is simultaneously distributed across the 0th and −1st order diffractions, forming a stable double-main-lobe far-field distribution, exhibiting double blaze behavior; meanwhile, λ=990nm maintains a single +1st order blaze behavior. This state constitutes a hybrid blaze operating mode, with the far-field distribution as shown... Figure 8 As shown.

[0043] After further adjusting the unit parameters, when the phase coverage in both working bands is insufficient to support a pure single-channel blaze, such as Figure 6 As shown, under the conditions of λ=640nm and λ=990nm, the transmitted energy is redistributed between the 0th order and the corresponding diffraction order, respectively. Both bands exhibit stable double-blaze characteristics. The far-field distribution corresponding to the double-blaze state in both bands is as follows: Figure 9 As shown.

[0044] The results above demonstrate that, while maintaining the anomalous deflection direction, the staggered-arranged combined phase gradient metasurfaces can achieve a continuous and controllable transition from single blaze to double blaze by adjusting the phase coverage, and flexibly combine different blaze states within the dual-band. These diverse blaze behaviors do not originate from phase gradient failure or random scattering, but rather from the controllable redistribution of transmitted energy between the 0th order and the anomalous diffraction channel, fully demonstrating the high flexibility of this supergrating structure in dual-band wavefront manipulation and energy control.

[0045] Based on the above considerations, this invention ultimately selected the hybrid blaze operating mode as the experimental verification object. This mode maintains a stable output of a single anomalous deflection channel in one band, while introducing dual-channel energy distribution characteristics in another band. It can simultaneously demonstrate the band-selective blaze behavior and far-field energy modulation capability of metasurfaces in a single device, and has high experimental observability and verification value.

[0046] To verify the feasibility of the proposed design, metasurface samples were fabricated on silicon / sapphire (SOS) substrates using methods such as... Figure 10 The five-step process shown is completed. The specific steps include spin-coating electron beam resist, electron beam lithography (EBL), chromium (Cr) hard mask deposition, inductively coupled plasma (ICP) etching, and resist removal. First, an electron beam resist layer is spin-coated onto an SOS substrate, and the designed nanopillar array pattern is formed by EBL etching. Then, a thin chromium film is deposited as a hard mask, and the pattern is highly anisotropically transferred to the silicon layer by ICP etching. Finally, the chromium mask and remaining resist are removed to obtain a periodic silicon nanopillar array on a sapphire substrate.

[0047] The prepared structure was characterized using scanning electron microscopy (SEM). Figure 11As shown, the metasurface exhibits uniform periodicity and good structural integrity over a large area. Figure 12 Magnified top-view SEM images further confirmed the clear morphology of the nanopillars, with diameters and spacing consistent with the design parameters. Tilt-view SEM revealed vertical sidewalls and smooth surfaces on the nanopillars, validating the high precision and fidelity of the fabrication process. These results demonstrate that the proposed metasurface design is not only feasible but also compatible with scalable nanofabrication techniques, providing a reliable foundation for its practical application in integrated photonics systems.

[0048] To verify the diffraction response characteristics of staggered-staggered metasurfaces over a wide spectral range, a structure was constructed as follows: Figure 13 The optical experimental system shown is as follows. In the experiment, monochromatic light from a tunable monochromatic light source is collimated and then incident perpendicularly onto the metasurface sample through an aperture and a microscope objective. The transmitted diffracted light spot is collected by the imaging system and recorded on a CCD camera, thereby enabling systematic measurement of diffraction behavior under different wavelength conditions.

[0049] Figure 14 Transmission diffraction patterns obtained in two representative wavelength bands are presented, corresponding to the 620–660 nm and 960–1000 nm bands, respectively. In the short-wavelength operating band (620–660 nm), the transmitted energy is mainly distributed in the −1 and 0 order directions, forming two main diffraction spots with similar intensities. However, in the long-wavelength operating band (960–1000 nm), the transmitted energy is significantly concentrated in the +1 order direction, exhibiting clear single-channel blaze characteristics. This experimental phenomenon is consistent with the aforementioned numerical simulation results, indicating that the designed staggered-staggered metasurface can achieve differentiated diffraction order modulation in different wavelength bands.

[0050] Figure 15 Experimental results showing the relative diffraction efficiencies of the −1, 0, and +1 orders as a function of wavelength are presented to quantitatively characterize the distribution of transmitted energy among different diffraction orders. For ease of comparison with design goals, the main operating wavelength range selected during the design phase is indicated by different colored shading areas in the figure. It can be seen that within the short-wavelength design band (620–660 nm, corresponding to the red shading area in the figure), the −1 and 0 order diffraction efficiencies remain consistently high, while the +1 order diffraction efficiency is relatively low, indicating that transmitted energy is mainly distributed between the −1 and 0 order channels, highly consistent with the expected mixed blaze operating state in the design. As the wavelength gradually deviates from this design band, the energy distribution of each diffraction order begins to change, reflecting the influence of phase response dispersion on diffraction efficiency.

[0051] In contrast, within the long-wavelength design band (970–1010 nm, corresponding to the blue shaded area in the figure), the +1st order diffraction efficiency is significantly improved and dominates, while the -1st and 0th order diffraction efficiencies are significantly reduced, indicating that the device achieves single-channel blazed deflection in this band. This experimental result is highly consistent with the aforementioned phase gradient design and far-field simulation predictions, verifying the effectiveness of the dual-band opposite-order control strategy from the perspective of energy distribution.

[0052] Figure 16 The wavelength-dependent displacement characteristics of the diffraction spots were quantitatively analyzed. The measured trajectories of the -1st order (red) and +1st order (blue) spots diverged almost linearly with wavelength, further verifying that the metasurface can achieve efficient, polarization-independent, and wavelength-selective beam deflection. These results demonstrate that the staggered-arranged metasurface effectively achieves broadband diffraction of opposite orders in two wavelength bands within a compact device size, showcasing its potential in wavelength-tunable free-space beam splitting applications.

[0053] In summary, through joint analysis of the energy distribution of diffraction orders and their spatial deflection behavior as a function of wavelength, the experimental results systematically demonstrate the ability of staggered-staggered metasurfaces to achieve broadband diffraction control of opposite orders in two bands within a compact device size, showcasing their application potential in wavelength-tunable free-space beam separation and multi-band integrated optical systems.

[0054] Example 2 A method for order control based on metasurface blazed gratings is provided. Based on the structure of the metasurface blazed grating in Example 1, a detailed description of the structure can be found in the corresponding description in the above structural embodiments, and will not be repeated here. The method includes the following steps: In a single-layer planar metasurface, independent phase gradients are designed for at least two different target operating bands; Phase control units designed for different target operating bands are arranged in an alternating manner to form a combined phase gradient metasurface. By utilizing the difference in dispersion characteristics of the phase modulation unit under different operating bands, the combined phase gradient metasurface can form different equivalent phase distributions in each target operating band. By adjusting the phase coverage within each target's working band, the distribution of transmitted energy among different diffraction orders can be controlled, thereby achieving independent control of the blaze behavior of each target's lower-order working band.

[0055] To achieve controllable beam deflection on the transmission side, this invention designs a dual-phase gradient metasurface composed of subwavelength silicon nanopillars, whose unit geometry parameters gradually vary along the spatial direction. By precisely controlling the geometry of each nanopillar unit, the transmission phase can be continuously adjusted and a linear phase gradient can be constructed, thereby guiding the outgoing wavefront to the target diffraction order. Its basic working principle is as follows: Figure 1 As shown, at two representative operating wavelengths ( and The opposite order of anomalous diffraction can be achieved under these conditions, and the corresponding experimental diffraction pattern is shown in the attached figure.

[0056] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0057] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

[0058] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0059] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0060] The above description is merely an embodiment of this specification and is not intended to limit the scope of one or more embodiments of this specification. Various modifications and variations can be made to one or more embodiments of this specification by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of one or more embodiments of this specification should be included within the scope of the claims of one or more embodiments of this specification.

Claims

1. A method for order control based on metasurface blazed grating, characterized in that, The method comprises the following steps: In a single-layer planar metasurface, independently designed phase gradients are respectively designed for at least two different target operating wavebands; The phase control units designed for different target operating wavebands are staggered and arranged to form a combined phase gradient metasurface; The combined phase gradient metasurface is formed by using the dispersion characteristics of the phase control units at different operating wavebands to form different equivalent phase distributions in each target operating waveband; By adjusting the phase coverage in each target operating waveband, the distribution of transmitted energy between different diffraction orders is controlled, thereby independently adjusting the order blazed behavior in each target operating waveband.

2. The order control method based on the metasurface blazed grating according to claim 1, characterized in that, The phase coverage adjustment refers to selecting the geometric parameters of the phase control units to achieve nearly complete 0-2π phase coverage in one target operating waveband to achieve single blazed, or less than 2π phase coverage in another target operating waveband to achieve double blazed, thereby realizing double-band mixed blazed in the same device.

3. A metasurface blazed grating based structure for implementing the method of any one of claims 1 to 2, characterized in that, The method comprises: A single-layer planar substrate; A plurality of sub-wavelength nanocolumns arranged in an array on the substrate to form a metasurface; The plurality of sub-wavelength nanocolumns comprise first type phase control units and second type phase control units; The first type phase control units are configured to provide a first linear phase gradient in a first target operating waveband; The second type phase control units are configured to provide a second linear phase gradient in a second target operating waveband; The first type phase control units and the second type phase control units are staggered and arranged in a staggered staggered manner to form a super-period, which is used to realize different equivalent grating periods and phase modulation characteristics in the first target operating waveband and the second target operating waveband, respectively, to independently adjust the diffraction order distribution in the two wavebands.

4. A metasurface blazed grating based structure as claimed in claim 3, wherein, The nanocolumns are full dielectric nanocolumns with circularly symmetric cross sections to realize polarization-independent propagation phase modulation.

5. A metasurface blazed grating based structure as claimed in claim 4, wherein, The nanocolumns are single-crystal silicon nanocolumns.

6. A metasurface blazed grating based structure according to claim 3 or 4, wherein, The first target operating waveband and the second target operating waveband are different and are located in the visible light waveband and the near-infrared waveband, respectively.

7. A metasurface blazed grating based structure according to claim 6, wherein, The first target operating waveband is 620-660 nm, and the second target operating waveband is 970-1010 nm.

8. A metasurface blazed grating based structure as claimed in claim 3, wherein, The first type phase control units contribute less to the equivalent phase distribution of the combined phase gradient metasurface in the second target operating waveband than the second type phase control units; and the second type phase control units contribute less to the equivalent phase distribution in the first target operating waveband than the first type phase control units.

9. A metasurface blazed grating based structure according to claim 3 or 8, wherein, By adjusting the geometric parameters of the first type phase control units and the second type phase control units, the phase response of each in its non-target operating waveband is continuously adjusted, and then the equivalent phase coverage of the entire super-period in the corresponding waveband is adjusted, to realize a continuously controllable transition from single blazed to double blazed.

10. A metasurface blazed grating based structure as claimed in claim 3, wherein, The structure is configured to realize at least one of the following operating modes: A double-band single blazed mode: in the first target operating waveband and the second target operating waveband, the concentration of transmitted energy on a single non-zero diffraction order is higher than the concentration on any other diffraction order. Hybrid blaze mode: Within the first target operating band, the concentration of transmitted energy in the 0th order and one non-zero diffraction order is higher than that in other diffraction orders; Within the second target operating band, the concentration of transmitted energy at a single non-zero diffraction order is higher than that at any other diffraction order; or, Dual-band dual-blaze mode: In the first target operating band and the second target operating band, the concentration of transmitted energy in the 0th order and one non-zero diffraction order is higher than that in other diffraction orders.

11. A metasurface blazed grating based structure as claimed in claim 10, wherein, In the hybrid blaze mode, the diffraction order of energy concentration in the first target working band is -1, and the diffraction order of energy concentration in the second target working band is +1, thereby achieving diffraction modulation of opposite orders in the two bands.

12. A metasurface blazed grating based structure as claimed in claim 3, wherein, The staggered arrangement allows the local phase distribution to exhibit segmented continuity within a single working band, while maintaining monotonic evolution on a global superperiodic scale, thereby suppressing undesigned diffraction orders and concentrating energy on the target diffraction orders.

13. A metasurface blazed grating based structure as claimed in claim 3, wherein, The diameter of the nanopillars is in the range of 50-150 nm, and the transmission phase can be continuously controlled from 0 to 2π by adjusting the diameter.

Images