Structured light excitation unit and plasma structured lighting source

Abstract

The invention discloses a structured light excitation unit and a plasma structured lighting source, and the structured light excitation unit comprises a transparent substrate; and a first metal layer disposed on the first surface of the transparent substrate, the first metal layer being configured to generate an anti-ermitus conjugate coupling effect. Because the first metal layer can generate an anti-Erhi conjugate coupling effect, localized surface plasmon polaritons can be excited to serve as structured light under the irradiation of light, the illumination light source with the different structures is different from a traditional illumination light source with the different structures, and the spatial resolution limit of the SIM is improved under the condition of low illumination intensity.

Description

Technical Field

[0001] This invention relates to the field of super-resolution microscopy imaging technology, specifically to a structured light excitation unit and a plasma structured illumination source. Background Technology

[0002] Due to the diffraction effect of waves, the resolving power of a microscope is limited by its working wavelength λ and the numerical aperture NA of the objective lens. Microscopic objects smaller than d=0.61λ / NA cannot be distinguished under traditional microscopes. Therefore, for more than a hundred years, the spatial resolution of visible light (390~780nm) microscopes has been limited to 200nm.

[0003] Structured illumination microscopy uses illumination light from specific structures to transfer information outside the optical transfer function range into the range during the imaging process. Specific algorithms are then used to move high-frequency information within the range back to its original position, thereby expanding the sample's frequency domain information through the microscopic system and enabling the reconstructed image resolution to exceed the diffraction limit.

[0004] Based on the characteristics of low phototoxicity and fast imaging speed, structured illumination imaging technology has unique advantages in observing dynamic processes in living cells. It has been used to track the morphological changes and interactions of organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus in real time, which plays an important role in revealing the intrinsic mechanisms of metabolic diseases.

[0005] However, due to limitations in the spatial frequency and control method of structured illumination sources, the spatial resolution, imaging speed, and integration of structured illumination micro-imaging also face challenges. Summary of the Invention

[0006] To address at least one of the aforementioned problems, according to one aspect of the present invention, a structured light excitation unit is provided.

[0007] The structured light excitation unit includes a transparent substrate and a first metal layer disposed on a first surface of the transparent substrate. The first metal layer is configured to generate an anti-Hermitian conjugate coupling effect. Because the first metal layer can generate an anti-Hermitian conjugate coupling effect, it can excite localized surface plasmons (LSPs) as structured light (localized plasmon structured light source) under illumination. This different structured illumination source differs from traditional structured illumination sources and improves the spatial resolution limit of SIM (Structure Illumination Microscopy) under low illumination conditions.

[0008] In some implementations, the first metal layer capable of generating an anti-Hermitian conjugate coupling effect is implemented as an anisotropic metastructure, which can excite localized surface plasmons as structured light under illumination.

[0009] In some embodiments, the first metal layer is a nanoantenna array, which includes at least one set of array elements, each set of array elements including n×n metal nanoantennas, where n is an integer and n≥3.

[0010] Because the number of phase control points available when n ≤ 2 is very limited, higher-order and more complex structured light modes cannot be achieved. However, when n ≥ 3, a finer sampling grid can be provided, allowing the metasurface to achieve more complex and steeper phase distributions in the range of 0 to 2π within one period. Moreover, n ≥ 3 allows the target phase distribution (such as spiral phase) to be discretized onto a larger grid, meaning that continuous phase can be approximated with smaller "steps," which reduces phase quantization errors and makes the generated beam wavefront closer to the ideal, thus achieving more accurate phase fitting. At the same time, when n ≥ 3, the phase change is smoother, allowing more energy to be concentrated on the desired diffraction order (e.g., only on the +1 order, generating pure vortex light), thus significantly improving conversion efficiency and mode purity. In addition, n ≥ 3 provides a large degree of freedom, allowing n to be designed separately for x-polarization and y-polarization. 2 The independent phase profiles and the huge degree of freedom allow you to manipulate multiple polarization channels simultaneously and independently, which makes it possible to realize polarization multiplexing and multi-functional integration. The design of n≥3 also makes the required phase difference between adjacent antennas in the supercell smaller and the electromagnetic field transition more natural. This helps to reduce scattering loss and makes the performance of the actual manufactured device closer to the theoretical simulation. Moreover, a larger n can sometimes improve the robustness to manufacturing errors. At the same time, since structured illumination super-resolution imaging usually requires more than 3 phase structured light fringes to achieve good super-resolution imaging reconstruction, n≥3 is usually required.

[0011] In some embodiments, a photoresist layer is further disposed on the first surface of the transparent substrate, and the thickness H of the photoresist layer is greater than the thickness h of the first metal layer, covering the first metal layer. This ensures the smoothness of the upper surface while protecting the metal nanoantenna array from oxidation; it also prevents direct contact between fluorescent molecules and the metal of the first metal layer, thus avoiding fluorescence quenching.

[0012] In some implementations, the array elements are arranged in a square shape. This allows for a high degree of alignment with electromagnetic wave characteristics and anisotropy requirements: First, the core of anisotropic nanoantennas (such as "nanobricks," elliptical, or V-shaped antennas) lies in their principal axis directions, which respond differently to light polarized along different principal axis directions. The square arrangement possesses two naturally orthogonal lattice vector directions (typically defined as the x and y axes), which perfectly align with the two fundamental, orthogonal linear polarization states of light waves (such as horizontal x-polarization and vertical y-polarization). This alignment allows designers to intuitively and independently design phase profiles for x- and y-polarization, and the design parameters (such as rotation angle and dimensions) of each nanoantenna can be customized. The phases of two orthogonal polarization components can be independently controlled, and the coupling and crosstalk between them can be minimized in a square lattice, which greatly simplifies the design process and numerical simulation. The nano-antenna array of this application mainly utilizes anti-Hermitian coupling to improve the Q value of the plasma resonance, eliminates crosstalk between different metal nano-antenna resonances within a limited wavelength range, and realizes the movement of structured light stripes. Through the anisotropy of the rectangular nano-antenna, xy polarized light can be used to excite LSPs structured light in two orthogonal directions respectively. The LSPs structured light is only localized near the metal nano-antenna, without far-field transmission, and does not involve transmission phase and geometric phase.

[0013] In some implementations, the cross-section of the metallic nanoantenna is rectangular. This allows for, on the one hand, a strong and intuitive anisotropic response: because the rectangular structure naturally possesses two asymmetric axes: a major axis and a minor axis. When the electric field direction of the incident light is parallel to the major axis of the nanobrick, a strong electric dipole resonance is excited; when the electric field is parallel to the minor axis, an electric dipole resonance with different resonant frequencies and intensities is excited. This highly polarization-direction-sensitive response is the basis for constructing anisotropic metasurfaces. Furthermore, by changing the length L and width W of the nanobrick, its optical response (including resonant phase) to two orthogonally linearly polarized (e.g., x-pol (x-polarization) and y-pol (y-polarization)) incident light can be independently tuned, enabling complex polarization conversions. On the other hand, the propagation phase can be adjusted by modifying the length and width of the rectangle. Moreover, this allows for nanofabrication... From a technical perspective, rectangular structures have significant advantages: mainstream micro-nano fabrication technologies such as electron beam lithography and ion beam lithography are very adept at defining patterns with straight edges, and rectangular and square structures are among the easiest and most precise patterns for them to process. Furthermore, due to strong anisotropy, rectangular nanobricks can effectively convert the energy of incident light from one polarization state to another (e.g., from x-polarization to y-polarization, or from left-handed circular polarization to right-handed circular polarization). This efficient polarization conversion is a prerequisite for generating structured light (such as generating vortex light using geometric phase) because it ensures that most of the light energy carries the designed phase information. In addition, super-resolution imaging requires structured light to scan in two orthogonal directions, and setting the cross-section of the metal nanoantenna to be rectangular can control the scanning direction of the structured light in the x and y orthogonal directions by adjusting the polarization of the incident light.

[0014] In some implementations, the array elements are arranged in multiple groups in a periodic array P, where P < λ. e , λ e The wavelength of fluorescence excited by structured light is given. Therefore, diffraction can be controlled to concentrate energy into the desired light field mode and detection direction: First, according to grating diffraction theory, when a light wave passes through a periodic structure, multiple diffraction orders are generated. The diffraction angle θ is determined by the grating equation: Psinθ = mλ, where m is the diffraction order. When P < λ... e Time: For fluorescence wavelength λ e The equation becomes sinθ=mλ e / P>m. Since sinθ≤1, the only possible solution is m=0th order, which means that fluorescence cannot produce any higher order (m≥1) diffraction, thus achieving energy concentration, improved signal-to-noise ratio, and avoidance of crosstalk; secondly, when P<λ eFurthermore, it ensures that the excitation light itself only has one diffraction order (i.e., the principal functional order) after passing through the metasurface. This results in more ideal morphology and purer topological charge of the generated structured light (such as vortex spots), enabling more precise excitation and manipulation of fluorescent samples. Additionally, a period P < λ e The metasurface can generate a diffraction-free, high-frequency excitation light field. The fluorescence signal produced after this excitation light field interacts with the sample exhibits high fluorescence intensity due to its wavelength λ. e >P itself does not diffract, which allows high-frequency sample information to be captured by the objective lens as an m=0 order signal, thereby reconstructing an image that exceeds the diffraction limit through subsequent algorithms; in addition, the smaller P is, the higher the spatial frequency of the structured light, and the higher the resolution of the super-resolution imaging reconstructed using this structured light.

[0015] In some implementations, all metal nanoantennas have the same thickness h. This greatly simplifies the manufacturing process, improves yield and consistency, while ensuring the purity of phase modulation and the accuracy of the design; moreover, it helps to achieve uniform optical efficiency and impedance matching, while ensuring the quality of the generated structured light field, and can enhance the mechanical stability and reliability of the device.

[0016] In some implementations, the center-to-center distance d between adjacent metallic nanoantennas in each array element is the same, and d = P / n. This allows for precise, continuous, and crosstalk-free wavefront sampling within the supercell, while also ensuring infinite periodicity and seamless splicing of optical functions between supercells.

[0017] In some embodiments, the metal nanoantenna is made of at least one of Al (aluminum), Au (gold), and Ag (silver). This not only ensures the stability of the metal nanoantenna's performance and a long service life due to the low degradation rate of these materials, but also results in higher efficiency of LSPs excited by the metal nanoantenna using these materials.

[0018] In some implementations, the thickness h of the first metal layer is ≥ 30 nm. This allows for sufficient phase modulation while providing adequate "optical thickness," and also enables the formation of enhanced, low-loss plasmon resonance.

[0019] In some implementations, the thickness H of the photoresist layer ranges from Hh ≥ 10 nm. This ensures a smooth upper surface while protecting the metal nanoantenna array from oxidation and reducing fluorescence quenching.

[0020] In some implementations, within each array element, the metal nanoantennas in the same row have the same length, while their width increases sequentially along the array direction. This allows for precise and linear modulation of the phase of another orthogonal polarization state while maintaining a stable response to a particular polarization state.

[0021] In some implementations, within each array unit, the width of the same column of metallic nanoantennas is the same, while the length increases sequentially along the array direction. In a supercell, the "rows" employ a "fixed length, variable width" design to control X-polarized light, while the "columns" employ a "fixed width, variable length" design to control Y-polarized light. These two designs can be perfectly integrated into the same n×n grid, thereby achieving completely independent and parallel wavefront modulation of two orthogonal linear polarization states.

[0022] Within each array element, metal nanoantennas in the same row maintain the same length, while those in different rows have progressively increasing lengths. When x-polarized light is incident, the resonant frequency of the metal nanoantenna is primarily related to its length (x-direction), with minimal influence from changes in its width (y-direction). Therefore, only the length parameter is considered for x-polarized incidence. Metal nanoantennas in the same row have the same resonant wavelength, while those in adjacent rows have different widths and thus different resonant wavelengths λ1, λ2, ... λ. n Furthermore, anti-Hermitian conjugate coupling can be generated between different rows of metallic nanoantennas, leading to a superposition of sharp resonances across a wide range of superradiant states (SS). This increases the Q-value of the resonances between different rows of nanoantennas, allowing for the generation of different wavelengths λ1, λ2, ... λ. n Incident light sequentially excites the LSPs of different rows of metallic nanoantennas to resonate, achieving phase modulation of the striped structured light in the y-direction. In each array unit, the metallic nanoantennas in the same column maintain the same width (y-direction), while the metallic nanoantennas in different rows have increasing widths. When y-polarized light is incident, the resonant frequency of the metallic nanoantennas is mainly related to its width (y-direction) and has little effect on its length (x-direction); therefore, only the width parameter is considered when y-polarized light is incident. The metallic nanoantennas in the same column have the same resonant wavelength, while the metallic nanoantennas in adjacent columns have different lengths and different resonant wavelengths λ1, λ2, ..., λn. In addition, anti-Hermitian conjugate coupling can be generated between metallic nanoantennas in different columns, which can produce a superposition phenomenon of sharp resonances in a wide superradiant states (SS), thereby increasing the Q value of the resonance of different columns of nanoantennas. This allows incident light of different wavelengths λ1, λ2, ..., λn to sequentially excite the LSPs of different columns of metallic nanoantennas to resonate, achieving phase modulation of the striped structured light in the x-direction.

[0023] In some embodiments, the transparent substrate is made of glass, sapphire, SiO2 (silicon dioxide), or Si3N4 (silicon nitride). This ensures that the transparent substrate is transparent to visible light, thereby guaranteeing the excitation effect of the structured light excitation unit.

[0024] In some implementations, the photoresist is transparent to visible light. Its core advantage lies in minimizing the absorption and scattering of light by the photoresist within the optical functional wavelength range, thereby ensuring the final optical performance of the metasurface.

[0025] In some implementations, within each array element group, the width of the metallic nanoantennas in the same row increases sequentially along the array direction, with the increase being < d / 2, where d = P / n, d is the distance between the center points of two adjacent metallic nanoantennas in each array element group, and P is the period of the arrangement of multiple array elements, where P < λ. e , λ e This is the fluorescence wavelength excited by structured light. Therefore, relatively well-defined striped LPSs structured light can be excited in the near field.

[0026] In some implementations, within each array element, the length of the same column of metallic nanoantennas increases sequentially along its array direction, with an increase of < d / 2; d is the distance between the center points of two adjacent metallic nanoantennas in each array element, and P is the period of the arrangement of multiple array elements, P < λ. e , λ e This is the fluorescence wavelength excited by structured light. Therefore, relatively well-defined striped LPSs structured light can be excited in the near field.

[0027] According to one aspect of the present invention, a plasma structured illumination source is provided, comprising the aforementioned structured light excitation unit. Because the first metal layer can generate an anti-Hermitian conjugate coupling effect, it can excite localized surface plasmons as structured light (localized plasma structured light source) under illumination. This different structured illumination source differs from conventional structured illumination sources, improving the spatial resolution limit of structured illumination micro-imaging under low light intensity conditions.

[0028] In some embodiments, the plasma structure illumination source further includes a liquid crystal polarizer and a tunable light source capable of adjusting the wavelength of the incident light, sequentially disposed on the side of the transparent substrate opposite to the first metal layer. Thus, the wavelength and polarization of the incident light can be adjusted by the liquid crystal polarizer and the tunable light source, thereby exciting a movable subwavelength structure light source on the surface of a metallic nanoantenna array. This results in a tunable localized plasma structure light source excited on an anisotropic metallic metasurface. This tunable nanostructure light source can be used to achieve super-resolution imaging with fluorescent structure illumination. Moreover, using a liquid crystal polarizer not only reduces costs but also provides a faster modulation polarization speed. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a structured light excitation unit according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a structured light excitation unit according to an embodiment of the present invention; Figure 3 for Figure 2 The diagram shows the structure of the optical excitation unit and its partially enlarged structure. Figure 4 This is a schematic diagram of the structure of a plasma structure lighting source according to an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the excitation and control of plasma structured light when the plasma structured lighting source has n=3, according to one embodiment of the present invention; wherein... Figure 5 Figure a shows the absorption and radiation spectra of the organic dye, where λ1, λ2, and λ3 are the incident wavelengths, respectively. e The wavelength of dye fluorescence excited by structured light; Figure 5 Figure b in the figure shows the tunable structured light excited by x-polarization; Figure 5 Figure c in the diagram shows the tunable structured light excited by x-polarization; Reference numerals: 20, transparent substrate; 30, first metal layer; 31, array unit; 311, metal nanoantenna; 40, photoresist layer; 50, liquid crystal polarizer; 60, tunable light source. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0031] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising" or "including" include not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. The terminology used herein is generally that commonly used by those skilled in the art; in case of any discrepancy with commonly used terminology, the terminology used herein shall prevail.

[0032] Furthermore, for ease of description, spatial relative terms such as “below,” “under,” “lower,” “above,” and “upper” may be used herein to describe the relationship between one element or component and another (or other) element or component as shown in the figure. In addition to the orientation shown in the figure, spatial relative terms are intended to include different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein can be interpreted accordingly.

[0033] In this invention, the term "structural illumination microscopy" refers to a high-end fluorescence microscopy technique that breaks through the resolution limits of traditional optical microscopes through special illumination modes and complex image reconstruction algorithms. It can improve the resolution to approximately twice that of traditional microscopes.

[0034] In this invention, the term "objective numerical aperture NA" is a physical quantity describing the ability of an objective lens to collect light. It is defined as: NA = n × sin(θ), where n is the refractive index of the medium between the objective lens and the object being observed, and θ is the maximum half-angle when light enters the objective lens, that is, half of the maximum angle between the light ray and the optical axis of the objective lens.

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] To address the aforementioned issues, the inventors conducted extensive research and development, discovering that while metal antennas can excite LSPs and generate near-field localizations much smaller than the excitation wavelength, the plasmonic resonance Q value of the metal nanoantenna 311 is very low due to the inherent losses and mode losses of the material. Furthermore, the absorption wavelength range of organic dyes is typically limited (usually <100nm), making it difficult to eliminate crosstalk between different metal nanoantenna resonances within a limited wavelength range. This results in the metal nanoantenna array being unable to excite high-contrast tunable LSP structured light.

[0037] During extensive research and development, the inventors accidentally discovered that anti-Hermitian conjugate coupling can reconstruct eigenstates with different lifetimes, thereby generating a superposition phenomenon of sharp resonances within a wide range of superradiant states (SS). Utilizing the anti-Hermitian conjugate coupling effect of metallic nanoantennas, multiple eigenstates can be excited simultaneously, and these eigenstates can interfere constructively on specific antennas while interfering destructively on other antennas, forming LSP structured light with a period much smaller than the excitation wavelength. LSPR can be achieved by exciting specific sites with specific wavelengths, thus realizing phase modulation of LSP structured light within a limited wavelength range (the absorption spectrum of organic dyes).

[0038] Based on this, this application proposes a structured light excitation unit (such as...) Figures 1 to 3 (As shown).

[0039] like Figure 1 As shown, the structured light excitation unit includes a transparent substrate 20 and a first metal layer 30 disposed on a first surface of the transparent substrate 20. The first metal layer 30 is configured to generate an anti-Hermitian conjugate coupling effect.

[0040] As one embodiment of the first metal layer 30 capable of generating an anti-Hermitian conjugate coupling effect, it is implemented as having an anisotropic metastructure and capable of exciting localized surface plasmon resonances as structured light under illumination.

[0041] The inventors discovered that the anti-Hermitian conjugate coupling effect in anisotropic metasurfaces can generate two-dimensional tunable localized plasma structure light sources. Unlike traditional structured illumination sources, this localized plasma structured light source combines the strong anti-Hermitian conjugate coupling and anisotropic properties of metasurfaces. Within the absorption wavelength range of organic dyes, it can achieve two-dimensional control of the excited structured light by adjusting the wavelength and polarization state of the incident light. This enables precise and rapid control of the structured light phase and scanning direction, providing a fully solid-state control scheme for structured light illumination. It avoids the problems of low signal-to-noise ratio, low integration, poor system stability, and high cost associated with mechanical motion devices, while significantly simplifying the structured illumination imaging system. Furthermore, the localized surface plasmons (LSPs) excited by the metal metasurface as structured light, compared to spatial photons, can generate structured light with higher spatial frequencies, improving the spatial resolution limit of SIM under low illumination conditions. Moreover, through anisotropic nanoantenna design, different polarizations can excite subwavelength structured light in different directions, extending the excitation and control of structured light to a two-dimensional plane, and also enabling control of the structured light scanning direction.

[0042] As one embodiment of the first metal layer 30 capable of generating an anti-Hermitian conjugate coupling effect, such as Figure 2 and Figure 3 As shown, the first metal layer 30 is a nano-antenna array, which includes at least one set of array elements 31. Each set of array elements 31 includes n×n metal nano-antennas 311, where n is an integer and n≥3. Since the phase control points that can be provided when n≤2 are very limited, it is impossible to realize higher-order and more complex structured light modes. When n≥3, a finer sampling grid can be provided, enabling the metasurface to achieve more complex and steeper phase distributions in the range of 0 to 2π within one period. Furthermore, n≥3 allows the target phase distribution (such as a spiral phase) to be discretized onto a larger grid, meaning that continuous phases can be approximated with smaller "steps." This reduces phase quantization errors, resulting in a beam wavefront closer to the ideal and achieving more accurate phase fitting. Simultaneously, when n≥3, phase changes are smoother, allowing more energy to be concentrated on the desired diffraction order (e.g., only the +1 order, generating pure vortex light), significantly improving conversion efficiency and mode purity. Moreover, n≥3 provides a large degree of freedom, allowing for the design of n values ​​for x-polarization and y-polarization respectively. 2 The independent phase profiles and the huge degree of freedom allow you to manipulate multiple polarization channels simultaneously and independently, which makes it possible to realize polarization multiplexing and multi-functional integration. The design of n≥3 also makes the required phase difference between adjacent antennas in the supercell smaller and the electromagnetic field transition more natural. This helps to reduce scattering loss and makes the performance of the actual manufactured device closer to the theoretical simulation. Moreover, a larger n can sometimes improve the robustness to manufacturing errors. At the same time, since structured illumination super-resolution imaging usually requires more than 3 phase structured light fringes to achieve good super-resolution imaging reconstruction, n≥3 is usually required.

[0043] In some embodiments, continue to refer to Figure 2 and Figure 3As shown, the array elements 31 are arranged in a square shape to perfectly match the electromagnetic wave characteristics and anisotropy requirements: First, the core of anisotropic nanoantennas (such as "nanobricks," elliptical, or V-shaped antennas) is their principal axis direction, which responds differently to light polarized along different principal axis directions: The square arrangement has two naturally orthogonal lattice vector directions (usually defined as the x and y axes), which perfectly align with the two fundamental, orthogonal linear polarization states of light waves (such as horizontal x-polarization and vertical y-polarization); this alignment allows designers to intuitively and independently design phase profiles for x-polarization and y-polarization, and the design parameters of each nanoantenna (such as rotation angle, ...) are also considered. The phase of the two orthogonal polarization components can be independently controlled (size), and the coupling and crosstalk between them can be minimized in a square lattice, which greatly simplifies the design process and numerical simulation. The nano-antenna array of this application mainly utilizes anti-Hermitian coupling to improve the Q value of the plasma resonance, eliminates the crosstalk of different metal nano-antenna 311 resonances within a limited wavelength range, realizes the movement of structured light stripes, and realizes the excitation of LSPs structured light in two orthogonal directions by xy polarized light through the anisotropy of the rectangular nano-antenna. The LSPs structured light is only localized near the metal nano-antenna 311, without far-field transmission, and does not involve transmission phase and geometric phase.

[0044] In some embodiments, continue to refer to Figure 2 and Figure 3As shown, the cross-section of the metallic nanoantenna 311 is rectangular. On one hand, it enables a strong and intuitive anisotropic response: this is because the rectangular structure naturally has two asymmetric axes: a major axis and a minor axis. When the electric field direction of the incident light is parallel to the major axis of the nanobrick, a strong electric dipole resonance is excited; when the electric field is parallel to the minor axis, an electric dipole resonance with different resonant frequencies and intensities is excited. This highly sensitive response to polarization direction is the basis for constructing anisotropic metasurfaces. Moreover, by changing the length L and width W of the nanobrick, its optical response (including the resonant phase) to two orthogonally linearly polarized (e.g., x-pol and y-pol) incident lights can be independently tuned, which provides the possibility for complex polarization conversion. On the other hand, the propagation phase can be adjusted by adjusting the length and width of the rectangle. Furthermore, from a nanofabrication perspective, the rectangular... The structure has significant advantages: mainstream micro-nano fabrication technologies such as electron beam lithography and ion beam lithography are very good at defining patterns with straight edges, and rectangular and square structures are among the easiest and most precise patterns to process. Furthermore, due to strong anisotropy, rectangular nanobricks can effectively convert the energy of incident light from one polarization state to another (e.g., from x-polarization to y-polarization, or from left-handed circular polarization to right-handed circular polarization). This efficient polarization conversion is a prerequisite for generating structured light (such as generating vortex light using geometric phase) because it ensures that most of the light energy carries the designed phase information. In addition, super-resolution imaging requires structured light to scan in two orthogonal directions. The rectangular cross-section of the metal nanoantenna 311 can control the scanning direction of structured light in the x and y orthogonal directions by polarizing the incident light.

[0045] In some embodiments, such as Figure 1 As shown, all metal nanoantennas 311 have the same thickness h, which greatly simplifies the manufacturing process, improves yield and consistency, while ensuring the purity of phase modulation and the accuracy of the design. Furthermore, it helps to achieve uniform optical efficiency and impedance matching, while ensuring the quality of the generated structured light field and enhancing the mechanical stability and reliability of the device. In some embodiments, the thickness h of the first metal layer 30 is ≥30 nm, which enables sufficient phase modulation while providing adequate "optical thickness," and allows for the formation of enhanced, low-loss plasmon resonance.

[0046] In some embodiments, such as Figure 3 As shown, the array unit 31 is provided with multiple groups arranged in a periodic array P, where P < λ. e , λ eThe fluorescence wavelength excited by structured light is used to control diffraction and concentrate energy into the desired light field mode and detection direction. First, according to grating diffraction theory, when a light wave passes through a periodic structure, multiple diffraction orders are generated. The diffraction angle θ is determined by the grating equation: Psinθ = mλ, where m is the diffraction order. When P < λ... e Time: For fluorescence wavelength λ e The equation becomes sinθ=mλ e / P>m. Since sinθ≤1, the only possible solution is m=0th order, which means that fluorescence cannot produce any higher order (m≥1) diffraction, thus achieving energy concentration, improved signal-to-noise ratio, and avoidance of crosstalk; secondly, when P<λ e Furthermore, it ensures that the excitation light itself only has one diffraction order (i.e., the principal functional order) after passing through the metasurface. This results in more ideal morphology and purer topological charge of the generated structured light (such as vortex spots), enabling more precise excitation and manipulation of fluorescent samples. Additionally, a period P < λ e The metasurface can generate a diffraction-free, high-frequency excitation light field. The fluorescence signal produced after this excitation light field interacts with the sample exhibits high fluorescence intensity due to its wavelength λ. e >P itself does not diffract, which allows high-frequency sample information to be captured by the objective lens as an m=0 order signal, thereby reconstructing an image that exceeds the diffraction limit through subsequent algorithms; in addition, the smaller P is, the higher the spatial frequency of the structured light, and the higher the resolution of the super-resolution imaging reconstructed using this structured light.

[0047] In some embodiments, continue to refer to Figure 3 As shown, the center point spacing d between two adjacent metal nanoantennas 311 in each array unit 31 is the same, and d=P / n, so as to achieve accurate, continuous and crosstalk-free wavefront sampling within the supercell, and also to ensure the infinite periodicity and seamless splicing of optical functions between supercells.

[0048] In some embodiments, the metal nanoantenna 311 is made of at least one of Al, Au, and Ag to ensure the stability of the performance and long service life of the metal nanoantenna 311 while ensuring the high efficiency of the excited LSPs.

[0049] In some embodiments, such as Figure 3 As shown, in each array element 31, the metal nanoantennas 311 in the same row have the same length, and their width increases sequentially along the array direction. For example, each metal antenna element is labeled C. i，j , (i,j=1,2,…n), where i and j represent the row and column respectively; the length-x and width-y of the metal antenna are represented by a. i，j and b i，j (a)i，j , b i，j <(d); wherein, for the metal antennas in the same row, the length - x is equal, and the width - y increases sequentially, i.e., a i，j = a i，1 , and b i，j+1 > b i，j , so as to accurately and linearly control the phase of another orthogonal polarization state while maintaining a stable response to a certain polarization state.

[0050] In some embodiments, as Figure 3 shown, in each group of array units 31, the widths of the metal nano - antennas 311 in the same column are the same, and the lengths increase sequentially along their array direction. For example, each metal antenna unit is marked as C i，j , (i, j = 1, 2, … n), where i and j respectively represent the row and column where they are located; the length - x and width - y of the metal antenna are respectively represented as a i，j and b i，j (a i，j , b i，j (d); wherein, for the metal antennas in the same column, the length - x increases sequentially, and the height - y is equal, i.e., b i，j = b 1，j , and a i+1 , j > a i，j . When a supercell, its "rows" adopt a "fixed - length, variable - width" design to control the X - polarized light, and its "columns" adopt a "fixed - width, variable - length" design to control the Y - polarized light. These two designs can be perfectly integrated in the same n×n grid, so as to achieve completely independent and parallel wave - front control of two orthogonal linear polarization states.

[0051] In each group of array units 31, the metal nano - antennas 311 in the same row maintain the same length, and the metal nano - antennas 311 in different rows have increasing lengths; when x - polarized light is incident, the resonance frequency of the metal nano - antenna 311 is mainly related to its length (x - direction), and the influence of the change in its width (y - direction) is very small; therefore, only the length parameter is considered when x - polarized light is incident; the metal nano - antennas 311 in the same row have the same resonance wavelength, while the widths of the metal nano - antennas 311 between adjacent rows are different, having different resonance wavelengths λ1, λ2, … λ n ; in addition, anti - Hermitian conjugate coupling can occur between the metal nano - antennas 311 in different rows, and a sharp resonance superposition phenomenon can occur within a wide super - radiant state (Superradiant States - SS), thereby increasing the Q - value of the resonance of different - row nano - antennas, making different wavelengths λ1, λ2, … λ nIncident light sequentially excites LSPs resonances in different rows of metal nanoantennas 311, achieving phase modulation of the striped structured light in the y-direction. In each array unit 31, the metal nanoantennas 311 in the same column maintain the same width (y-direction), while the metal nanoantennas 311 in different rows have progressively increasing widths. When y-polarized light is incident, the resonant frequency of the metal nanoantennas 311 is mainly related to their width (y-direction), with little influence from changes in their length (x-direction); therefore, only the width parameter is considered for y-polarized incident light. The metal nanoantennas 311 in the same column have the same resonant wavelength, while the metal nanoantennas 311 in adjacent columns have different lengths and different resonant wavelengths λ1, λ2, ... λ. n Furthermore, anti-Hermitian conjugate coupling can be generated between different columns of metallic nanoantennas 311, enabling the superposition of sharp resonances within a wide range of superradiant states (SS), thereby increasing the Q-value of the resonances of different columns of nanoantennas and allowing different wavelengths λ1, λ2, ... λ to be coupled. n Incident light sequentially excites LSPs resonances in different columns of metal nanoantennas 311, achieving phase modulation of the striped structured light in the x-direction.

[0052] In some embodiments, within each array element 31, the width of the metal nanoantennas 311 in the same row increases sequentially along its array direction, with the increase being < d / 2, where d = P / n, d is the distance between the center points of two adjacent metal nanoantennas 311 in each array element 31, and P is the period of the arrangement of multiple array elements 31, where P < λ. e , λ e The fluorescence wavelength is the one excited by structured light.

[0053] In some embodiments, in each array element 31, the length of the same column of metal nanoantennas 311 increases sequentially along its array direction, with an increase of < d / 2; d is the distance between the center points of two adjacent metal nanoantennas 311 in each array element 31, and P is the period of the arrangement of multiple array elements 31, P < λ. e , λ e The fluorescence wavelength is the one excited by structured light.

[0054] In some embodiments, C i，j The length-x and width-y can be designed through FDTD (Finite-Difference Time-Domain) simulation.

[0055] In some embodiments, the transparent substrate 20 is made of glass, sapphire, SiO2 or Si3N4 to ensure that the transparent substrate 20 is transparent to visible light, thereby ensuring the excitation effect of the structured light excitation unit.

[0056] In some embodiments, such as Figure 1As shown, a photoresist layer 40 is spin-coated on the first surface of the transparent substrate 20. The thickness H of the photoresist layer 40 (from the upper surface of the photoresist layer 40 (the surface facing away from the transparent substrate 20) to the upper surface of the transparent substrate 20 (the surface where the first metal layer 30 is disposed)) is greater than the thickness h of the first metal layer 30, and covers the first metal layer 30. This ensures the smoothness of the upper surface while protecting the metal nanoantenna 311 array from oxidation. It also prevents fluorescent molecules from directly contacting the metal of the first metal layer 30, thereby avoiding fluorescence quenching. In some embodiments, the thickness H of the photoresist layer 40 is in the range of Hh ≥ 10 nm, ensuring the smoothness of the upper surface while protecting the metal nanoantenna 311 array from oxidation, and also reducing fluorescence quenching. In some embodiments, the photoresist is a photoresist transparent to visible light, for example, PMMA (poly(methyl methacrylate)) or SU-8 is used as the photoresist material. Its core advantage lies in minimizing the absorption and scattering of light by the photoresist within the optical functional band, thereby ensuring the final optical performance of the metasurface.

[0057] Figure 4 An exemplary embodiment of the plasma structure lighting source of the present invention is shown.

[0058] like Figure 4 As shown, the plasma structured illumination source includes the aforementioned structured light excitation unit. Because the first metal layer 30 can generate an anti-Hermitian conjugate coupling effect, it can excite localized surface plasmons as structured light (localized plasma structured light source) under illumination. This different structured illumination source differs from traditional structured illumination sources, significantly improving the spatial resolution limit of structured illumination micro-imaging under low light intensity conditions.

[0059] In some embodiments, continue to refer to Figure 4 As shown, the plasma structure illumination source also includes a liquid crystal polarizer 50 and a tunable light source 60 that can adjust the wavelength of the incident light, which are sequentially disposed on the side of the transparent substrate 20 opposite to the first metal layer 30. By adjusting the wavelength and polarization of the incident light through the liquid crystal polarizer 50 and the tunable light source 60, a movable subwavelength structure light source can be excited on the surface of the metal nanoantenna array, resulting in a tunable local plasma structure light source excited by an anisotropic metal metasurface. This tunable nanostructure light source can be used to realize super-resolution imaging with fluorescence structure illumination. Moreover, the use of the liquid crystal polarizer 50 not only reduces costs but also has a faster modulation polarization speed.

[0060] In some embodiments, the tunable light source 60 can be implemented as a tunable laser, or a broadband light source and a tunable filter. A tunable laser changes the wavelength of the incident light by tuning the laser wavelength, which is a relatively simple adjustment method; a broadband light source and a tunable filter change the wavelength of the incident light by filtering, which is more complex in terms of adjustment method, but can reduce costs and allows for more flexible wavelength adjustments.

[0061] This invention proposes a tunable localized plasma structure light source excited by an anisotropic metallic metasurface. By adjusting the wavelength and polarization of the incident light, a movable subwavelength structure light source can be excited on the surface of a metallic antenna array. This tunable nanostructure light source can be used to achieve super-resolution imaging with fluorescent structure illumination.

[0062] In use, light shines from the transparent substrate 20 onto the array unit 31 composed of metal nanoantennas 311. The wavelength of the incident light is controlled by the tunable light source 60. Different linearly polarized light is filtered by the liquid crystal polarizer 50, thus achieving the control of polarized light. By controlling the wavelength and polarization of the incident light, tunable LSP patterns can be excited on the surface of the structured light unit. These subwavelength LSPs can serve as the structured illumination source for super-resolution imaging.

[0063] Figure 4 To simulate and verify the tunable plasmonic structured light in the case of n=3, the absorption wavelength range of the dye molecules is shown in the green line. Phase tuning of the plasmonic structured light needs to be achieved within this absorption wavelength range. After absorbing incident light, the dye molecules emit fluorescence, with the fluorescence wavelength range shown in the blue line. A wavelength λ, where the dye molecules exhibit high fluorescence intensity and weak absorption, is selected. e Super-resolution imaging is achieved using this as a far-field probe light. By tuning the incident light wavelengths λ1, λ2, and λ3, the plasma structured light can be shifted at subwavelengths. Furthermore, by tuning the linear polarization direction of the incident light using a liquid crystal polarizer 50, the scanning direction of the plasma structured light can be controlled. This subwavelength tunable structured light can excite the fluorescence emission of dye molecules on the photoresist surface, and combined with structured light imaging algorithms, super-resolution imaging can be achieved.

[0064] according to Figure 5 As shown in Figure a of the light spectrum, incident light λ1, λ2, and λ3 excites structured light of different phases (λ1, λ2, and λ3 are all within the absorption spectrum of the fluorescent molecule and all have high absorption efficiency). The fluorescent molecule absorbs the structured light and emits fluorescence. By detecting the fluorescence emitted by the fluorescent molecule at a wavelength of λ... e By observing the fluorescence, fluorescence images excited by different structured lights can be obtained. These fluorescence images excited by different structured lights can then be reconstructed into super-resolution images using algorithms. Based on... Figure 5 As shown in Figure b, when x-polarized light is incident, LSP structured light fringes excited by different wavelengths achieve scanning of the y-direction of the fringe structured light. According to... Figure 5 As shown in Figure c, when y-polarized light is incident, LSP structured light stripes excited by different wavelengths achieve scanning of the striped structured light in the x-direction.

[0065] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A structured light excitation unit, characterized in that The structure light excitation unit comprises: a transparent substrate; and a first metal layer arranged on a first surface of the transparent substrate, the first metal layer being arranged to be capable of generating a reverse evanescent coupling effect.

2. The structured light excitation unit of claim 1, wherein, The first metal layer is a nano antenna array, the nano antenna array comprising at least one array unit group, each array unit group comprising n×n metal nano antennas, wherein n is an integer and n≥3; and / or The first surface of the transparent substrate is further provided with a photoresist layer, and the thickness H of the photoresist layer is greater than the thickness h of the first metal layer and covers the first metal layer.

3. The structured light excitation unit of claim 2, wherein, The array unit is arranged in a square shape; and / or The cross section of the metal nano antenna is rectangular.

4. The structured light excitation unit of claim 3, wherein, The array unit is arranged in multiple groups and in a period P array, wherein P < λ e , λ e is the fluorescent wavelength excited by the structured light. And / or The thickness h of all the metal nano antennas is the same.

5. The structured light excitation unit of claim 4, wherein, The spacing d of the center points of two adjacent metal nano antennas in each array unit group is the same, and d=P / n; and / or The material of the metal nano antenna is at least one of Al, Au and Ag.

6. The structured light excitation unit of claim 2, wherein, The thickness h of the first metal layer is≥30nm; and / or The thickness H of the photoresist layer is in the range of H-h≥10nm.

7. The structured light excitation unit according to any one of claims 2 to 6, characterized in that, In each array unit group, the lengths of the metal nano antennas in the same row are the same, and the widths of the metal nano antennas in the same row increase in the array direction of the metal nano antennas; and / or In each array unit group, the widths of the metal nano antennas in the same column are the same, and the lengths of the metal nano antennas in the same column increase in the array direction of the metal nano antennas.

8. The structured light excitation unit of claim 7, wherein, The material of the transparent substrate is glass, sapphire, SiO2 or Si3N4; and / or The photoresist is a photoresist transparent to visible light.

9. The structured light excitation unit of claim 7, wherein, In each array unit group, the widths of the metal nano antennas in the same row increase in the array direction of the metal nano antennas, and the increasing amplitude is< d / 2, d=P / n; and / or In each array unit group, the lengths of the metal nano antennas in the same column increase in the array direction of the metal nano antennas, and the increasing amplitude is< d / 2. d is the distance between the center points of two adjacent metal nanoantennas in each array unit, P is the period of the arrangement of multiple array units, P < λ e , λ e is the wavelength of the fluorescence excited by the structured light.

10. A plasma-structured illumination light source, characterized in that The structure light excitation unit comprises: The structure light excitation unit further comprises a liquid crystal polarizer arranged on the side of the transparent substrate away from the first metal layer and a tunable light source capable of adjusting the wavelength of incident light.

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