Subwavelength nanostructure, method for preparing same, and metasurface laser

Abstract

This invention provides a subwavelength nanostructure, its fabrication method, and a metasurface laser. The fabrication method includes the following steps: providing a substrate; forming a subwavelength nanostructure template on the substrate; and growing a perovskite gain material in the microcavity of the subwavelength nanostructure template using a self-assembly process to obtain the subwavelength nanostructure. This invention fabricates a subwavelength nanostructure with symmetry breaking, achieving precise mode control and multi-channel radiation. By growing perovskite in situ in the microcavity using a self-assembly process, in-situ fusion and monolithic integration of the luminescent material and the microcavity are achieved, effectively enhancing light-matter interaction and facilitating disordered-phase modulation of the laser spatial mode. Under laser pumping, low-threshold, high-quality-factor laser emission can be obtained, and the radiation mode and emission channel can be precisely controlled, providing a new approach for constructing high-precision, programmable, and on-demand controllable metasurface lasers.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano manufacturing technology and optoelectronic devices, specifically relating to a subwavelength nanostructure and its preparation method and a metasurface laser. Background Technology

[0002] As the core light source of modern optoelectronic technology, lasers play an irreplaceable role in numerous fields such as fiber optic communication, lidar, precision measurement, industrial processing, optical storage, biological imaging, and laser displays due to their unique advantages such as high coherence, high directionality, and monochromaticity. With the development of information technology towards integration and miniaturization, optoelectronic devices are placing even more urgent demands on the small size, low power consumption, and integrability of laser light sources.

[0003] Traditional lasers are primarily fabricated using III-V semiconductor materials (such as gallium arsenide and indium phosphide) or doped fiber / crystal materials. While III-V semiconductor lasers possess excellent properties such as high photoelectric conversion efficiency and fast response speed, their fabrication processes are complex, requiring expensive epitaxial growth and cleavage processes, and they are difficult to be compatible with mainstream complementary metal-oxide-semiconductor (CMOS) processes, limiting their application in optoelectronic integrated chips. Fiber lasers and solid-state lasers, while offering high output power and good beam quality, are bulky, making it difficult to meet the requirements of on-chip integration. Furthermore, the resonant cavity of traditional lasers typically relies on mirrors or Bragg gratings, whose size is limited by the diffraction limit, making it difficult to achieve mode confinement below the wavelength scale, thus restricting the possibility of further miniaturization of the devices.

[0004] To overcome these bottlenecks, researchers have attempted to introduce metasurface structures and optical microcavities into laser design. Metasurfaces, as two-dimensional artificial interfaces composed of subwavelength unit structures, can flexibly control the amplitude, phase, and polarization of light waves within the subwavelength scale, providing a new approach for constructing planar, multifunctional integrated lasers. Optical microcavities (such as whispering-gallery mode microcavities and photonic crystal microcavities) can confine the light field within a very small mode volume through resonance effects, significantly enhancing the interaction between light and matter, thereby reducing the laser threshold and increasing the modulation rate. Combining metasurfaces and microcavities allows for precise control of lasing modes, output directions, and polarization characteristics while achieving optical field localization, opening new avenues for developing high-performance on-chip laser sources.

[0005] In recent years, overcoming the limitations of high-quality factor laser cavity mode modulation by introducing engineered disordered structures has become a research hotspot. Studies have shown that introducing rotational disorder into the resonant cavity enables artificial manipulation of the geometric phase, offering possibilities for novel devices such as spin-valley-locked lasers, narrowband superlenses, and holographic metasurface lasers. However, existing research is mostly limited to a single form of rotational disorder, making it difficult to achieve on-demand modulation of intracavity intrinsic modes. From the perspective of laser mechanisms, directly integrating gain materials into the resonant cavity can maximize the spatial overlap between the mode and the gain medium, thereby reducing the lasing threshold and enhancing light-matter interaction. This maximized overlap also provides favorable conditions for achieving effective phase modulation from disordered structures to laser spatial modes, but current integration methods struggle to achieve this goal.

[0006] In summary, current metasurface lasers and microcavity lasers still have significant shortcomings in terms of mode control mechanisms: disordered engineering methods are limited, control precision is insufficient, and the integration of gain materials and resonant cavities has not yet achieved optimal mode and gain superposition.

[0007] Therefore, how to provide a method for preparing subwavelength nanostructures that can achieve richer symmetry breaking mechanisms, obtain high-precision, programmable, and on-demand tunable metasurface lasers, and promote their practical application and on-chip integration is an urgent technical challenge to be solved. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention aims to provide a subwavelength nanostructure, its fabrication method, and a metasurface laser. This invention fabricates a subwavelength nanostructure with symmetry breaking, overcoming the limitation of traditional single-mode laser emission control. It enables precise mode control and multiple independently controllable radiation channels. Specifically, through a self-assembly process, perovskite gain material is grown in situ within the microcavity of the subwavelength nanostructure, achieving in-situ fusion and monolithic integration of the luminescent material and the microcavity structure. This integrated structure effectively enhances the interaction between light and matter and facilitates effective disordered-phase modulation of the laser spatial mode. Based on this, under laser pumping, this subwavelength nanostructure can achieve low-threshold, high-quality-factor laser emission and precisely control the radiation mode and emission channels. It enables multi-channel laser output within the same device, establishing a mode control mechanism for metasurface lasers and an integration method for materials and resonant cavities. This provides a new solution for realizing high-precision, programmable, and on-demand controllable metasurface lasers.

[0009] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing subwavelength nanostructures, the method comprising the following steps: Provide a base.

[0010] A subwavelength nanostructure template is formed on the substrate.

[0011] The subwavelength nanostructure is obtained by growing a perovskite gain material in the microcavity of the subwavelength nanostructure template through a self-assembly process.

[0012] The fabrication method provided by this invention overcomes the limitations of traditional methods that separately fabricate gain materials and optical microcavities and then integrate them. It proposes an integrated process route to fabricate a subwavelength nanostructure with symmetry breaking, overcoming the limitation of single-mode control in traditional laser emission. This allows for precise control of the mode mechanism and multiple independently controllable radiation channels. Specifically, by using a self-assembly process to grow perovskite gain materials in situ within the microcavity of the subwavelength nanostructure, in-situ fusion and monolithic integration of the luminescent material and the microcavity structure are achieved. This integrated structure effectively enhances the interaction between light and matter and facilitates effective disordered-phase modulation of the laser spatial mode. Based on this, under laser pumping, this subwavelength nanostructure can achieve low-threshold, high-quality-factor laser emission and precisely control the radiation mode and emission channels. It enables multi-channel laser output within the same device, constructing a mode control mechanism for metasurface lasers and an integration method for materials and resonant cavities. This provides a new solution for realizing high-precision, programmable, and on-demand controllable metasurface lasers.

[0013] The fabrication method provided by this invention can also be used to improve nonlinear conversion efficiency and emission mode coupling strength, thereby supporting efficient resonant wavefront shaping, structured single-photon sources and the generation of high-dimensional quantum entangled photon pairs, providing new ideas for the development of next-generation multifunctional ultra-compact photonic devices.

[0014] Preferably, the substrate comprises a silicon wafer and a silicon dioxide layer disposed on the surface of the silicon wafer. It should be noted that the present invention does not limit the deposition method of the silicon dioxide layer; for example, it may be inductively coupled plasma chemical vapor deposition, using a Plasma Pro 100 device.

[0015] Preferably, the method for forming the subwavelength nanostructure template includes the following steps: A photoresist layer is coated on the surface of the substrate, and then photolithography and etching are performed sequentially.

[0016] Preferably, the overall outer contour of the subwavelength nanostructure template is circular, and the radius of the circle is 50-70μm, for example, it can be 50μm, 52μm, 54μm, 56μm, 58μm, 60μm, 62μm, 64μm, 66μm, 68μm or 70μm, etc.

[0017] Preferably, in the subwavelength nanostructure template, the cross-sectional shape of each nanostructure unit is a circle with several rectangular notches, and the rectangular notches are evenly distributed along the outer periphery of the nanostructure unit. It should be noted that "several" refers to at least one, such as three rectangular notches evenly distributed along the circumferential edge of the circle.

[0018] Preferably, the thickness of the photoresist layer is 350-450nm, for example, it can be 350nm, 375nm, 400nm, 425nm or 450nm.

[0019] Preferably, the photolithography process includes pre-baking, exposure, development, fixing, rinsing and post-baking performed sequentially.

[0020] Preferably, the etching method includes inductively coupled plasma etching (ICP-380). An exemplary device for ICP-380 is used for ICP-380 etching.

[0021] Preferably, the etching depth is 150-190nm, for example, it can be 150nm, 160nm, 170nm, 180nm or 190nm.

[0022] Preferably, the radius of the circle is 100-150nm, for example, it can be 100nm, 110nm, 125nm, 135nm, or 150nm.

[0023] Preferably, the center-to-center spacing between adjacent nanostructure units is 300-340 nm, for example, it can be 300 nm, 310 nm, 320 nm, 330 nm or 340 nm.

[0024] Preferably, the width of the rectangular cut-off region is 40-60nm, for example, 40nm, 50nm or 60nm, and the height is 150-190nm, for example, 150nm, 160nm, 170nm, 180nm or 190nm.

[0025] It should be noted that the width here refers to the side length of the rectangular excised area, and the height refers to the depth of the sample etching.

[0026] Preferably, the self-assembly process includes the following steps: (a) Preparation of perovskite solution.

[0027] (b) The perovskite solution is spin-coated onto the subwavelength nanostructure template and then annealed.

[0028] Preferably, the perovskite solution has the general chemical formula ABX3, wherein A includes any one or a combination of at least two of formamidinium ions, methylamine ions, or cesium ions, B includes lead ions and / or tin ions, and X is a halide ion. For example, it could be a FAPbBr3 solution, etc. Furthermore, the cation at position A can be, in addition to the above-mentioned types of cations, selected from phenylethylamine ions, etc., and its general chemical formula could be FA. 0.8 PEA 0.2 PbBr3 solution, etc.

[0029] Preferably, the concentration of the perovskite solution is 0.3-0.5 mol / L, for example, it can be 0.3 mol / L, 0.4 mol / L or 0.5 mol / L.

[0030] Preferably, the spin coating speed of the perovskite solution is 3000-4000 rpm, such as 3000 rpm, 3200 rpm, 3500 rpm, 3700 rpm or 4000 rpm, and the spin coating time is 45-55 s, such as 45 s, 50 s or 55 s.

[0031] Preferably, the annealing temperature is 90-110℃, for example, 90℃, 100℃ or 110℃, and the annealing time is 5-10min, for example, 5min, 7min, 8min, 9min or 10min.

[0032] Preferably, the subwavelength nanostructure template is hydrophilically modified before the perovskite gain material is formed.

[0033] Preferably, after the perovskite gain material is formed, the step of forming a protective layer is further included, the protective layer comprising a polymethyl methacrylate (PMMA) layer.

[0034] Preferably, the thickness of the protective layer is 300-500nm, for example, it can be 300nm, 400nm or 500nm.

[0035] Preferably, the preparation method includes the following steps: (1) Provide a substrate; the substrate includes a silicon wafer and a silicon dioxide layer disposed on the surface of the silicon wafer, the thickness of the silicon dioxide layer being 350-450nm (e.g., 350nm, 400nm or 450nm, etc.).

[0036] The silicon dioxide layer is irradiated with ultraviolet ozone for 8-12 minutes (e.g., 8, 10, or 12 minutes). Then, photoresist is spin-coated onto the silicon dioxide layer at a speed of 2500-3500 rpm (e.g., 2500, 3000, or 3500 rpm) for 50-70 seconds (e.g., 50, 60, or 70 seconds), resulting in a photoresist layer with a thickness of 350-450 nm. Following this, electron beam lithography is performed, including pre-baking, exposure, development, fixing, rinsing, and post-baking. A photoresist layer with a predetermined pattern is obtained; wherein the photoresist is an electron beam photoresist, and the electron beam photoresist includes ZEP520A positive photoresist; the pre-baking temperature is 170-190℃ (e.g., 170℃, 180℃, or 190℃, etc.), and the time is 4-6 min (e.g., 4 min, 5 min, or 6 min, etc.); the post-baking temperature is 90-110℃ (e.g., 90℃, 100℃, or 110℃, etc.), and the time is 25-35 min (e.g., 25 min, 30 min, or 35 min, etc.).

[0037] The photoresist layer with the predetermined pattern is etched using inductively coupled plasma etching for 40-50 seconds and 150-190 nm to obtain a subwavelength nanostructure template.

[0038] The overall outer contour of the subwavelength nanostructure template is circular, with a radius of 50-70 μm. Each nanostructure unit in the subwavelength nanostructure template has a cross-sectional shape of a circle with several rectangular notches, which are uniformly distributed along the outer periphery of the nanostructure unit. The radius of the circle is 100-150 nm. The center-to-center distance between adjacent nanostructure units is 300-340 nm. The width of the rectangular notches is 40-60 nm, and the height is 150-190 nm.

[0039] (2) Prepare a perovskite solution with a concentration of 0.3-0.5 mol / L.

[0040] The subwavelength nanostructure template is hydrophilically modified for 5-15 minutes (e.g., 5 min, 10 min, or 15 min) using ozone plasma. Then, the perovskite solution is dropped onto the subwavelength nanostructure template and spin-coated at 3000-4000 rpm for 45-55 seconds. During the spin-coating process, an anti-solvent (e.g., toluene) is added. After spin-coating, the template is annealed at 90-110°C for 5-10 minutes to form a perovskite gain material. The volume ratio of the perovskite solution to the anti-solvent is (60-100):(150-200). (The perovskite solution is selected in the range of "60-100", which can be 60, 70, 80, 90, or 100, etc., and the anti-solvent is selected in the range of "150-200", which can be 150, 160, 170, 180, 190, or 200, etc.).

[0041] A polymethyl methacrylate solution is spin-coated onto the surface of the perovskite gain material at a rotation speed of 1000-2000 rpm (e.g., 1000 rpm, 1500 rpm, or 2000 rpm, etc.). After annealing, a polymethyl methacrylate layer is formed for 50-70 s (e.g., 50 s, 60 s, or 70 s, etc.), thus completing the preparation of the subwavelength nanostructure.

[0042] In a second aspect, the present invention provides a subwavelength nanostructure, which is prepared by the preparation method described in the first aspect.

[0043] The subwavelength nanostructure provided by this invention is not only compatible with existing surface-emitting laser technology of photonic crystals, but can also be extended to the field of electrically pumped structured lasers.

[0044] Thirdly, the present invention provides a metasurface laser comprising a pump source and a subwavelength nanostructure as described in the second aspect, wherein the pump source generates pump light to excite a perovskite gain material in the subwavelength nanostructure to emit a structured beam laser.

[0045] The subwavelength nanostructure provided by this invention, with the help of a pump light source, can achieve laser emission with low threshold and high quality factor, and the radiation mode and emission channel can be precisely controlled, providing a new technical path for developing optoelectronic devices that combine high-performance gain materials and fine microstructures with tunable radiation modes and emission channels.

[0046] Preferably, the pump source is a 400nm femtosecond laser with a pump power of 15-40μW, such as 15μW, 25μW, or 40μW.

[0047] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0048] Compared with the prior art, the present invention has the following beneficial effects: The fabrication method provided by this invention overcomes the limitations of traditional methods that separately fabricate gain materials and optical microcavities and then integrate them. It proposes an integrated process route to fabricate a subwavelength nanostructure with symmetry breaking, overcoming the limitation of single-mode control in traditional laser emission. This allows for precise control of the mode mechanism and multiple independently controllable radiation channels. Specifically, by using a self-assembly process to grow perovskite gain materials in situ within the microcavity of the subwavelength nanostructure, in-situ fusion and monolithic integration of the luminescent material and the microcavity structure are achieved. This integrated structure effectively enhances the interaction between light and matter and facilitates effective disordered-phase modulation of the laser spatial mode. Based on this, under laser pumping, this subwavelength nanostructure can achieve low-threshold, high-quality-factor laser emission and precisely control the radiation mode and emission channels. It enables multi-channel laser output within the same device, constructing a mode control mechanism for metasurface lasers and an integration method for materials and resonant cavities. This provides a new solution for realizing high-precision, programmable, and on-demand controllable metasurface lasers. Attached Figure Description

[0049] Figure 1 The flowchart shows the fabrication process of the subwavelength nanostructure provided in Example 1 of this invention.

[0050] Figure 2 This is a partial scanning electron microscope (SEM) image of a subwavelength nanostructure template prepared using different predetermined patterns in Embodiment 1 of the present invention.

[0051] Figure 3 An optical fluorescence microscope image of the subwavelength nanostructure provided in Embodiment 1 of the present invention.

[0052] Figure 4 Based on the subwavelength nanostructure provided in Embodiment 1 of the present invention ( Figure 2 (Left) An angular-resolved spectrum of spin valley-locked laser emission, and a threshold versus linewidth function plot.

[0053] Figure 5 Based on the subwavelength nanostructure provided in Embodiment 1 of the present invention ( Figure 2 (Right) An angular-resolved spectrum of spin valley-locked laser emission, and a threshold versus linewidth function plot.

[0054] Figure 6The image shows the reciprocal space spectrum of a vortex laser emission with a topological charge of 2, realized based on the subwavelength nanostructure provided in Embodiment 1 of the present invention.

[0055] Figure 7 The angle-resolved spectrum and reciprocal space spectrum of the vortex laser emission with a topological charge of 1, realized based on the subwavelength nanostructure provided in Embodiment 1 of the present invention.

[0056] Figure 8 The angle-resolved spectrum and reciprocal space spectrum of the vortex laser emission with a topological charge of 3 realized based on the subwavelength nanostructure provided in Embodiment 1 of the present invention are shown.

[0057] Figure 9 The images show the reciprocal space spectrum of a one-dimensional Airy beam emission realized based on the subwavelength nanostructure provided in Embodiment 1 of the present invention, as well as the intensity distribution along the K direction.

[0058] Figure 10 The images show the reciprocal space spectrum of the two-dimensional Airy beam emission and the intensity distribution along the K direction, based on the subwavelength nanostructure provided in Embodiment 1 of the present invention.

[0059] Figure 11 The reciprocal space spectrum of the Laguerre-Gaussian beam emission and the intensity distribution along the K direction are shown in Embodiment 1 of the present invention.

[0060] Figure 12 The reciprocal space spectrum of the Hermitian-Gaussian beam emission and the intensity distribution along the K direction are shown in Embodiment 1 of the present invention. Detailed Implementation

[0061] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0062] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0063] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0064] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0065] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0066] In one specific embodiment, the present invention provides a method for preparing subwavelength nanostructures, the method comprising the following steps: Provide a base.

[0067] A subwavelength nanostructure template is formed on the substrate.

[0068] The subwavelength nanostructure is obtained by growing a perovskite gain material in the microcavity of the subwavelength nanostructure template through a self-assembly process.

[0069] The fabrication method provided by this invention overcomes the limitations of traditional methods that separately fabricate gain materials and optical microcavities and then integrate them. It proposes an integrated process route to fabricate a subwavelength nanostructure with symmetry breaking, overcoming the limitation of single-mode control in traditional laser emission. This allows for precise control of the mode mechanism and multiple independently controllable radiation channels. Specifically, by using a self-assembly process to grow perovskite gain materials in situ within the microcavity of the subwavelength nanostructure, in-situ fusion and monolithic integration of the luminescent material and the microcavity structure are achieved. This integrated structure effectively enhances the interaction between light and matter and facilitates effective disordered-phase modulation of the laser spatial mode. Based on this, under laser pumping, this subwavelength nanostructure can achieve low-threshold, high-quality-factor laser emission and precisely control the radiation mode and emission channels. It enables multi-channel laser output within the same device, constructing a mode control mechanism for metasurface lasers and an integration method for materials and resonant cavities. This provides a new solution for realizing high-precision, programmable, and on-demand controllable metasurface lasers.

[0070] The fabrication method provided by this invention can also be used to improve nonlinear conversion efficiency and emission mode coupling strength, thereby supporting efficient resonant wavefront shaping, structured single-photon sources and the generation of high-dimensional quantum entangled photon pairs, providing new ideas for the development of next-generation multifunctional ultra-compact photonic devices.

[0071] Furthermore, the substrate includes a silicon wafer and a silicon dioxide layer disposed on the surface of the silicon wafer. It should be noted that the present invention does not limit the deposition method of the silicon dioxide layer; exemplary methods include inductively coupled plasma chemical vapor deposition (ICP-CVD), using a Plasma Pro 100 apparatus.

[0072] Furthermore, the method for forming the subwavelength nanostructure template includes the following steps: A photoresist layer is coated on the surface of the substrate, and then photolithography and etching are performed sequentially.

[0073] Furthermore, the overall outer contour of the subwavelength nanostructure template is circular, and the radius of the circle is 50-70μm, for example, it can be 50μm, 52μm, 54μm, 56μm, 58μm, 60μm, 62μm, 64μm, 66μm, 68μm or 70μm, etc.

[0074] Furthermore, in the subwavelength nanostructure template, the cross-sectional shape of each nanostructure unit is a circle with several rectangular notches, and the rectangular notches are uniformly distributed along the outer periphery of the nanostructure unit. It should be noted that "several" refers to at least one, such as three rectangular notches uniformly distributed along the circumferential edge of the circle.

[0075] The present invention designs nanostructure units with the above-mentioned specific shapes, which helps to satisfy the designed metasurface microcavities, generate continuous domain bound states (BIC), and realize laser emission with low threshold and high quality factor.

[0076] Furthermore, the thickness of the photoresist layer is 350-450nm, for example, it can be 350nm, 375nm, 400nm, 425nm or 450nm, etc.

[0077] Furthermore, the photolithography process includes pre-baking, exposure, development, fixing, rinsing, and post-baking performed sequentially.

[0078] Furthermore, the etching method includes inductively coupled plasma etching (ICP-380). An exemplary device for ICP-380 is used for ICP-380 etching.

[0079] Furthermore, the etching depth is 150-190nm, for example, it can be 150nm, 160nm, 170nm, 180nm or 190nm, etc.

[0080] In this invention, a suitable etching depth helps to meet the required optical mode coupling.

[0081] Furthermore, the radius of the circle is 100-150nm, for example, it can be 100nm, 110nm, 125nm, 135nm, or 150nm, etc.

[0082] In this invention, the circular cross-sectional shape radius of each nanostructure unit is 100-150 nm, which helps to meet the required optical mode coupling.

[0083] Furthermore, the center-to-center spacing between adjacent nanostructure units is 300-340 nm, for example, it can be 300 nm, 310 nm, 320 nm, 330 nm or 340 nm, etc.

[0084] The present invention designs the center-to-center spacing between adjacent nanostructure units to be 300-340 nm, that is, the period between nanostructure units is 300-340 nm, which is beneficial to meet the required optical mode coupling.

[0085] Furthermore, the width of the rectangular cut-off region is 40-60nm, for example, it can be 40nm, 50nm or 60nm, etc., and the height is 150-190nm, for example, it can be 150nm, 160nm, 170nm, 180nm or 190nm, etc.

[0086] It should be noted that the width here refers to the side length of the rectangular cut-off area. The height refers to the sample etching depth.

[0087] Furthermore, the self-assembly process includes the following steps: (a) Preparation of perovskite solution.

[0088] (b) The perovskite solution is spin-coated onto the subwavelength nanostructure template and then annealed.

[0089] This invention employs a self-assembly process, involving spin-coating and annealing a perovskite solution onto a subwavelength nanostructure template. The aim is to grow the perovskite gain material in situ within the microcavity of the subwavelength nanostructure, achieving in-situ fusion and monolithic integration of the luminescent material and the microcavity structure. This integrated structure effectively enhances the interaction between light and matter and facilitates efficient disordered-phase modulation of the laser spatial mode. Due to its fully monolithic integrated structure, this invention is not only compatible with existing photonic crystal surface-emitting laser technology but can also be extended to the field of electrically pumped structured lasers.

[0090] Further, the perovskite solution has the general chemical formula ABX3, where A includes any one or a combination of at least two of formamidinium ions, methylamine ions, or cesium ions; B includes lead ions and / or tin ions; and X is a halide ion. For example, it could be a FAPbBr3 solution, etc. In addition, the cation at position A can be one of the above-mentioned types of cations, or it can be selected from phenylethylamine ions, etc., with the general chemical formula FA. 0.8 PEA 0.2 PbBr3 solution, etc.

[0091] Furthermore, the concentration of the perovskite solution is 0.3-0.5 mol / L, for example, it can be 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, etc.

[0092] Furthermore, the spin coating speed of the perovskite solution is 3000-4000 rpm, for example, 3000 rpm, 3200 rpm, 3500 rpm, 3700 rpm or 4000 rpm, and the spin coating time is 45-55 s, for example, 45 s, 50 s or 55 s.

[0093] Furthermore, the annealing temperature is 90-110℃, for example, 90℃, 100℃ or 110℃, and the annealing time is 5-10min, for example, 5min, 7min, 8min, 9min or 10min.

[0094] In this invention, a suitable annealing temperature helps to accelerate the nucleation and growth of perovskite films, suppress the appearance of large grains, improve fluorescence intensity, and reduce film roughness.

[0095] Furthermore, before the perovskite gain material is formed, the subwavelength nanostructure template is first hydrophilically modified.

[0096] The purpose of pre-modifying the subwavelength nanostructure template with hydrophilicity in this invention is to ensure the uniformity of wetting of the perovskite solution during spin coating, thereby obtaining a low-roughness perovskite film with high and uniform fluorescence intensity.

[0097] Furthermore, after the perovskite gain material is formed, the step of forming a protective layer is also included, the protective layer comprising a polymethyl methacrylate (PMMA) layer.

[0098] This invention also designs a protective layer after the perovskite gain material is formed, with the aim of isolating the perovskite material from the influence of water and oxygen in the air, which greatly enhances the lifespan and stability of the perovskite material.

[0099] Furthermore, the thickness of the protective layer is 300-500nm, for example, it can be 300nm, 400nm or 500nm, etc.

[0100] Furthermore, the preparation method includes the following steps: (1) Provide a substrate; the substrate includes a silicon wafer and a silicon dioxide layer disposed on the surface of the silicon wafer, the thickness of the silicon dioxide layer being 350-450nm (e.g., 350nm, 400nm or 450nm, etc.).

[0101] The silicon dioxide layer is irradiated with ultraviolet ozone for 8-12 minutes (e.g., 8, 10, or 12 minutes). Then, photoresist is spin-coated onto the silicon dioxide layer at a speed of 2500-3500 rpm (e.g., 2500, 3000, or 3500 rpm) for 50-70 seconds (e.g., 50, 60, or 70 seconds), resulting in a photoresist layer with a thickness of 350-450 nm. Following this, electron beam lithography is performed, including pre-baking, exposure, development, fixing, rinsing, and post-baking. A photoresist layer with a predetermined pattern is obtained; wherein the photoresist is an electron beam photoresist, and the electron beam photoresist includes ZEP520A positive photoresist; the pre-baking temperature is 170-190℃ (e.g., 170℃, 180℃, or 190℃, etc.), and the time is 4-6 min (e.g., 4 min, 5 min, or 6 min, etc.); the post-baking temperature is 90-110℃ (e.g., 90℃, 100℃, or 110℃, etc.), and the time is 25-35 min (e.g., 25 min, 30 min, or 35 min, etc.).

[0102] The photoresist layer with the predetermined pattern is etched using inductively coupled plasma etching for 40-50 seconds and 150-190 nm to obtain a subwavelength nanostructure template.

[0103] The overall outer contour of the subwavelength nanostructure template is circular, with a radius of 50-70 μm. Each nanostructure unit in the subwavelength nanostructure template has a cross-sectional shape of a circle with several rectangular notches, which are uniformly distributed along the outer periphery of the nanostructure unit. The radius of the circle is 100-150 nm. The center-to-center distance between adjacent nanostructure units is 300-340 nm. The width of the rectangular notches is 40-60 nm, and the height is 150-190 nm.

[0104] (2) Prepare a perovskite solution with a concentration of 0.3-0.5 mol / L.

[0105] The subwavelength nanostructure template is hydrophilically modified for 5-15 minutes (e.g., 5 min, 10 min, or 15 min) using ozone plasma. Then, the perovskite solution is dropped onto the subwavelength nanostructure template and spin-coated at 3000-4000 rpm for 45-55 seconds. During the spin-coating process, an anti-solvent (e.g., toluene) is added. After spin-coating, the template is annealed at 90-110°C for 5-10 minutes to form a perovskite gain material. The volume ratio of the perovskite solution to the anti-solvent is (60-100):(150-200). (The perovskite solution is selected in the range of "60-100", which can be 60, 70, 80, 90, or 100, etc., and the anti-solvent is selected in the range of "150-200", which can be 150, 160, 170, 180, 190, or 200, etc.).

[0106] A polymethyl methacrylate solution is spin-coated onto the surface of the perovskite gain material at a rotation speed of 1000-2000 rpm (e.g., 1000 rpm, 1500 rpm, or 2000 rpm, etc.). After annealing, a polymethyl methacrylate layer is formed for 50-70 s (e.g., 50 s, 60 s, or 70 s, etc.), thus completing the preparation of the subwavelength nanostructure.

[0107] In another specific embodiment, the present invention provides a subwavelength nanostructure, which is prepared by the preparation method described above.

[0108] The subwavelength nanostructure provided by this invention is not only compatible with existing surface-emitting laser technology of photonic crystals, but can also be extended to the field of electrically pumped structured lasers.

[0109] In another specific embodiment, the present invention provides a metasurface laser, the metasurface laser comprising a pump source and a subwavelength nanostructure as described above, wherein the pump source generates pump light to excite the perovskite gain material in the subwavelength nanostructure to emit structured beam laser.

[0110] The subwavelength nanostructure provided by this invention, with the help of a pump light source, can achieve laser emission with low threshold and high quality factor, and the radiation mode and emission channel can be precisely controlled, providing a new technical path for developing optoelectronic devices that combine high-performance gain materials and fine microstructures with tunable radiation modes and emission channels.

[0111] Furthermore, the pump source is a 400nm femtosecond laser with a pump power of 15-40μW, for example, it can be 15μW, 25μW or 40μW.

[0112] It should be noted that the structured beam laser emitted by the metasurface laser can be characterized using a spectrometer (HORIBA iHR550), which has a slit width of 0.2-7 mm and an integration time of 0.005-20 s.

[0113] Example 1 This embodiment provides a method for preparing subwavelength nanostructures, and its process flow diagram is shown below. Figure 1 As shown, the preparation method includes the following steps: (1) An inductively coupled plasma chemical vapor deposition (IPC) method (equipment is Plasma Pro 100) was used to deposit a silicon dioxide layer with a thickness of 400 nm on the silicon wafer to obtain the substrate.

[0114] The silicon dioxide layer was irradiated with ultraviolet ozone using an ultraviolet ozone cleaner for 10 minutes. Then, electron beam photoresist was spin-coated onto the silicon dioxide layer at 3000 rpm for 60 seconds to obtain a photoresist layer with a thickness of 400 nm. Electron beam lithography was then performed, including pre-baking, exposure, development, fixing, rinsing, and post-baking, to obtain a photoresist layer with a predetermined pattern. The electron beam photoresist used was ZEP520A positive photoresist. The pre-baking temperature was 180°C for 5 minutes, and the post-baking temperature was 100°C for 30 minutes.

[0115] The photoresist layer with the predetermined pattern was etched using inductively coupled plasma etching (ICP-380 equipment) for 45 s at a depth of 170 nm to obtain a subwavelength nanostructure template. Scanning electron microscope (SEM) images of the subwavelength nanostructure templates prepared with different predetermined patterns are shown below. Figure 2 As shown ( Figure 2 Zuohe Figure 2 right).

[0116] The overall outer contour of the subwavelength nanostructure template is circular with a radius of 60 μm. In the scanning electron microscope image of a portion of the subwavelength nanostructure template, the yellow dashed area represents the region where the subwavelength nanostructure units rotate sequentially at equal angles. Each three-notch disk structure (i.e., each nanostructure unit has a cross-sectional shape of a circle with three rectangular notches, which are symmetrically and uniformly distributed at 120° along the outer periphery of the disk) within this region rotates clockwise around its center along the row and column direction, with the notch orientation changing continuously. The radius of the three-notch disk structure is 125 nm. The center-to-center distance between adjacent nanostructure units is 320 nm. The width of the notch is 50 nm, and the height is 170 nm. The surface roughness of the subwavelength nanostructure template is <2 nm.

[0117] (2) PbBr2 powder and FABr powder are added to DMF in a predetermined stoichiometric ratio to prepare a perovskite solution with a concentration of 0.4 mol / L (i.e., FAPbBr3 solution).

[0118] The subwavelength nanostructure template was hydrophilically modified using ozone plasma for 10 min. Then, 80 μL of perovskite solution was dropped onto the subwavelength nanostructure template, and spin-coated at 3500 rpm for 55 s. During the spin-coating process, 175 μL of toluene was added. After spin-coating, the template was annealed at 100 °C for 7 min to form a perovskite gain material. The volume ratio of the perovskite solution to the antisolvent was 80:175.

[0119] A polymethyl methacrylate solution was spin-coated onto the surface of the perovskite gain material at a speed of 1500 rpm. After annealing, a polymethyl methacrylate layer with a thickness of 400 nm was formed in 60 s, thus completing the preparation of the subwavelength nanostructure.

[0120] This embodiment also provides a metasurface laser, which includes a pump source and a subwavelength nanostructure as described above. The pump source generates pump light to excite the perovskite gain material in the subwavelength nanostructure to emit structured beam laser; wherein the pump source is a 400nm femtosecond laser with a pump power of 15-40μW (test power is 25μW).

[0121] The emitted structured laser beam was characterized using a spectrometer (HORIBA iHR550) with a slit width of 0.2-7 mm and an integration time of 0.005-20 s.

[0122] Figure 3 An optical fluorescence microscope image of the subwavelength nanostructure provided in this embodiment is shown. As can be seen from the image, the subwavelength nanostructure has bright green fluorescence with uniform intensity and high contrast compared to the background, further illustrating the efficient light-matter interaction after the perovskite gain material is monolithically integrated with the resonant cavity.

[0123] Using the metasurface laser provided in this embodiment, laser emission of various structural beams was performed, specifically: 1) Spin valley locked laser emission, based on Figure 2 The subwavelength nanostructures obtained on the left yielded the following results: Figure 4 The left figure shows an angle-resolved spectrum, and the relationship between pump power and emission intensity can be used to obtain... Figure 4 The right figure shows the threshold versus linewidth function. As can be seen from the figure, this invention achieves laser emission with a low threshold and high quality factor.

[0124] based on Figure 2 The subwavelength nanostructures obtained on the right yielded the following results: Figure 5 The left figure shows an angle-resolved spectrum, and the relationship between pump power and emission intensity can be used to obtain... Figure 5 The right figure shows the threshold versus linewidth function. As can be seen from the figure, this invention achieves laser emission with a low threshold and high quality factor.

[0125] 2) Vortex laser emission, obtaining vortex laser emission with different topological charges, including such as Figure 6 The reciprocal space spectrum with a topological charge of 2 is shown below. Figure 7 The left image shows the angle-resolved spectrum with a topological charge of 1, and the right image shows the reciprocal space spectrum. Figure 8 The left image shows the angular-resolved spectrum (left plot) and the right image shows the reciprocal space spectrum (right plot) for a topological charge of 3. (From...) Figure 6 , Figure 7 and Figure 8 It can be seen that the present invention has successfully achieved high-angle vortex laser emission with different topological charge numbers.

[0126] 3) Airy beam is emitted, resulting in... Figure 9 and Figure 10 The diagram shows the reciprocal space spectrum of one-dimensional and two-dimensional Airy beam emission (left), and the intensity distribution along the K direction (right). As can be seen from the figures, this invention successfully achieves uniform one-dimensional and two-dimensional Airy beam emission.

[0127] 4) Laguerre-Gaussian beam emission, resulting in... Figure 11 The reciprocal space spectrum (left) and intensity distribution along the K direction (right) are shown. As can be seen from the figures, this invention successfully achieves uniform Laguerre-Gaussian beam emission.

[0128] 5) Hermetic-Gaussian beam emission, resulting in... Figure 12 The reciprocal space spectrum (left) and intensity distribution along the K direction (right) are shown. As can be seen from the figures, this invention successfully achieves uniform Laguerre-Gaussian beam emission.

[0129] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing subwavelength nanostructures, characterized in that, The preparation method includes the following steps: Provide a base; A subwavelength nanostructure template is formed on the substrate; The subwavelength nanostructure is obtained by growing a perovskite gain material in the microcavity of the subwavelength nanostructure template through a self-assembly process.

2. The preparation method according to claim 1, characterized in that, The substrate includes a silicon wafer and a silicon dioxide layer disposed on the surface of the silicon wafer; And / or, the method for forming the subwavelength nanostructure template includes the following steps: A photoresist layer is coated on the surface of the substrate, and then photolithography and etching are performed sequentially. And / or, the overall outer contour of the subwavelength nanostructure template is circular, and the radius of the circle is 50-70 μm; And / or, in the subwavelength nanostructure template, the cross-sectional shape of each nanostructure unit is a circle with several rectangular notches, and the rectangular notches are uniformly distributed along the outer periphery of the nanostructure unit.

3. The preparation method according to claim 2, characterized in that, The thickness of the photoresist layer is 350-450 nm; And / or, the photolithography process includes pre-baking, exposure, development, fixing, rinsing and post-baking performed sequentially; And / or, the etching method includes inductively coupled plasma etching; And / or, the etching depth is 150-190 nm; And / or, the radius of the circle is 100-150 nm; And / or, the center-to-center spacing between adjacent nanostructure units is 300-340 nm; And / or, the width of the rectangular cut-off region is 40-60nm and the height is 150-190nm.

4. The preparation method according to any one of claims 1-3, characterized in that, The self-assembly process includes the following steps: (a) Preparation of perovskite solution; (b) The perovskite solution is spin-coated onto the subwavelength nanostructure template and then annealed.

5. The preparation method according to claim 4, characterized in that, The chemical formula of the perovskite solution is ABX3, wherein A includes any one or a combination of at least two of formamidinium ions, methylamine ions, or cesium ions, B includes lead ions and / or tin ions, and X is a halide ion. And / or, the concentration of the perovskite solution is 0.3-0.5 mol / L; And / or, the spin coating speed of the perovskite solution is 3000-4000 rpm, and the spin coating time is 45-55 s; And / or, the annealing temperature is 90-110℃ and the annealing time is 5-10 min.

6. The preparation method according to claim 4 or 5, characterized in that, Before the perovskite gain material is formed, the subwavelength nanostructure template is first hydrophilically modified. And / or, after the perovskite gain material is formed, the step of forming a protective layer is further included, the protective layer comprising a polymethyl methacrylate layer.

7. The preparation method according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: (1) Providing a substrate; the substrate includes a silicon wafer and a silicon dioxide layer disposed on the surface of the silicon wafer, the thickness of the silicon dioxide layer being 350-450 nm; The silicon dioxide layer is irradiated with ultraviolet ozone for 8-12 minutes, and then photoresist is spin-coated onto the silicon dioxide layer at a speed of 2500-3500 rpm for 50-70 seconds to obtain a photoresist layer with a thickness of 350-450 nm. Then, electron beam lithography is performed, including pre-baking, exposure, development, fixing, rinsing, and post-baking, to obtain a photoresist layer with a predetermined pattern. The photoresist is an electron beam photoresist, including ZEP520A positive photoresist. The pre-baking temperature is 170-190℃ for 4-6 minutes, and the post-baking temperature is 90-110℃ for 25-35 minutes. The photoresist layer with the predetermined pattern is etched using inductively coupled plasma etching for 40-50 s and 150-190 nm to obtain a subwavelength nanostructure template. The subwavelength nanostructure template has a circular outer contour with a radius of 50-70 μm. Each nanostructure unit within the template has a cross-sectional shape of a circle with several rectangular notches, evenly distributed along the outer periphery of the nanostructure unit. The radius of the circle is 100-150 nm. The center-to-center distance between adjacent nanostructure units is 300-340 nm. The width of each rectangular notch is 40-60 nm, and its height is 150-190 nm. (2) Prepare a perovskite solution with a concentration of 0.3-0.5 mol / L; The subwavelength nanostructure template is hydrophilically modified using ozone plasma for 5-15 minutes. Then, the perovskite solution is dropped onto the subwavelength nanostructure template and spin-coated at 3000-4000 rpm for 45-55 seconds. During the spin-coating process, an anti-solvent is added. After spin-coating, the template is annealed at 90-110℃ for 5-10 minutes to form a perovskite gain material. The volume ratio of the perovskite solution to the anti-solvent is (60-100):(150-200). A polymethyl methacrylate solution was spin-coated onto the surface of the perovskite gain material at a speed of 1000-2000 rpm. After annealing, a polymethyl methacrylate layer was formed in 50-70 s, thus completing the preparation of the subwavelength nanostructure.

8. A subwavelength nanostructure, characterized in that, The subwavelength nanostructure was prepared using the preparation method described in any one of claims 1-7.

9. A metasurface laser, characterized in that, The metasurface laser includes a pump source and a subwavelength nanostructure as described in claim 8, wherein the pump source generates pump light to excite the perovskite gain material in the subwavelength nanostructure to emit a structured beam laser.

10. The metasurface laser according to claim 9, characterized in that, The pump source is a 400nm femtosecond laser with a pump power of 15-40μW.

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