Wavelength multiplexing metasurface and design method for snapshot HiLo microscopy imaging

Abstract

The present invention belongs to the field of micro-nano optical technology, and relates to a wavelength multiplexing metasurface and design method for snapshot HiLo optical sectioning microscopic imaging, comprising the following steps: Step 1: Determine the relationship curves between the transmission phase and the transmission phase difference under the two working wavelengths of uniform illumination light and structured illumination light and the structural parameters of dielectric nanocolumns, and establish a basic unit structure phase library; Step 2: Determine the target phase difference between the uniform illumination light and the structured illumination light; Step 3: Screen the dielectric nanocolumns with equal target phase difference under the two working wavelengths in the basic structure unit library; Arrange the two screened dielectric nanocolumns according to the designed phase distribution equation to obtain a wavelength multiplexing metasurface structure. Compared with conventional HiLo microscopic imaging technology, the present invention effectively improves the imaging speed and imaging stability, reduces the complexity of the imaging and reconstruction process, and provides a new idea for snapshot HiLo microscopic imaging.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano optical technology, and specifically relates to a wavelength multiplexing metasurface for snapshot HiLo microscopic imaging and a design method thereof. Background Art

[0002] As a basic technology in biological microscopy, widefield microscopy is often used for non-contact, fast, and low-cost high-resolution imaging of the structural details of biological samples. However, traditional widefield microscopes do not have the ability to perform optical sectioning, and often require biological samples to be pre-processed before observation. Therefore, the system architecture can only provide high-resolution imaging for thin samples. For thick samples, the defocused background noise introduced by the system depth of field reduces the image quality, resulting in poor image contrast in widefield microscopes.

[0003] In order to suppress or eliminate the defocus noise during the imaging process, a variety of optical sectioning microscopy imaging technologies have been developed, including laser confocal microscopy, structured light illumination microscopy, and HiLo microscopy. Among them, laser confocal microscopy uses a single focus scanning method to achieve optical sectioning capabilities, which inevitably leads to a reduction in imaging speed. The advantage of structured light microscopy is that it significantly improves the speed of single optical sectioning imaging by using non-scanning illumination methods. However, this technology requires the collection of three sinusoidal stripe illumination images with different phase shifts to reconstruct the optical sectioning image, which to a certain extent still limits the imaging speed of structured light microscopes and their application in dynamic biological processes.

[0004] HiLo microscopy is a simple, fast and effective wide-field optical sectioning imaging technology. Compared with the three-step phase shift method of structured light illumination, HiLo technology can reconstruct a high-resolution image by only taking one uniform illumination image and one structured light illumination image. Although HiLo microscopy has further improved the imaging speed, in order to obtain the required uniform illumination image and structured light illumination image, the detection camera is still required to perform two image capture acquisitions, which will challenge the balance between imaging speed and imaging quality. First, ideally, two image acquisitions mean that the imaging speed of HiLo microscopy is only half of that of the detection camera. Secondly, the rapid switching of illumination light will reduce imaging stability and thus reduce image quality. Summary of the invention

[0005] In order to solve the above limitations in traditional HiLo imaging, the purpose of the present invention is to propose a wavelength multiplexing metasurface for snapshot HiLo optical sectioning microscopy imaging.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] On the one hand, the present invention discloses a design method of a wavelength multiplexing metasurface for snapshot HiLo optical sectioning microscopy imaging, which specifically comprises the following steps:

[0008] Step 1: Determine the relationship curves between the transmission phase and the transmission phase difference under the two working wavelengths of uniform illumination light and structured illumination light and the structural parameters of the dielectric nanocolumns, and establish a basic unit structure phase library;

[0009] Step 2: Determine the target phase difference between the uniform illumination light and the structured illumination light: When the wavelength of the incident light is λ1, the target phase of the structured illumination light is:

[0010]

[0011] When the wavelength of the incident light is λ2, the target phase of the uniform illumination light is:

[0012]

[0013] Among them, x is the horizontal coordinate of the basic unit structure; m is the sinusoidal modulation parameter; L is the period interval; is the reference phase; C is a constant; subscripts 1 and 2 represent two working wavelengths respectively;

[0014] Calculate the target phase difference at two working wavelengths:

[0015]

[0016] Step 3: Select the basic structural unit library obtained in step 1 that has a phase difference equal to the target at two working wavelengths. The two selected dielectric nanocolumns are arranged according to the designed phase distribution equation to obtain a wavelength multiplexing metasurface structure, and the designed phase distribution equation is as follows:

[0017]

[0018] Furthermore, the step 1 is performed by electromagnetic simulation software, in which the transmission phase is obtained according to the following transmission phase control principle:

[0019]

[0020] in, is the transmission phase; n eff is the effective refractive index; H is the height of the dielectric nanocolumn; λ1 and λ2 are the wavelengths of the two incident lights, respectively.

[0021] Furthermore, λ1 is 532 nm, λ2 is 633 nm; H=700 nm, P=350 nm.

[0022] On the other hand, the present invention discloses a wavelength multiplexing metasurface for snapshot HiLo optical sectioning microscopy imaging, which is designed by the wavelength multiplexing metasurface method for snapshot HiLo optical sectioning microscopy imaging of the present invention mentioned above.

[0023] Further, it includes a transparent substrate and a plurality of basic unit structures arranged on the transparent substrate, wherein the basic unit structure is a dielectric nanoantenna, and the dielectric nanoantenna includes a lattice and a dielectric nanocolumn arranged at the center of the upper surface of the lattice; the lattice is a cube with a side length P of 350nm, the dielectric nanocolumn is cylindrical, with a height H of 700nm, and a bottom diameter D of two specifications: 109nm and 108nm; the shape of the transparent substrate is a square; the dielectric nanocolumns of two bottom diameters are arranged according to the designed phase distribution equation, and the designed phase distribution equation is as follows:

[0024]

[0025] Among them, x is the horizontal coordinate of the basic unit structure; m is the sinusoidal modulation parameter; L is the period interval; is the reference phase; C is a constant; subscripts 1 and 2 represent two working wavelengths respectively.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The metasurface designed in the present invention has the characteristic of wavelength multiplexing. Therefore, under the condition of dual-wavelength mixed-color light source incidence, it can simultaneously meet the two illumination light requirements of HiLo optical sectioning microscopy imaging, and realize the function of reconstructing high-resolution images with a single shot acquisition.

[0028] 2. The metasurface designed by the present invention has a basic unit structure of cylindrical dielectric nanorods with a sub-wavelength size, so the metasurface has the characteristics of planarization, light weight, and easy photon integration. Therefore, the metasurface is suitable for miniaturization of optical systems.

[0029] 3. For different application scenarios, the working band of the metasurface can be adjusted accordingly, including the materials and structural parameters of the basic unit structure, which can be designed accordingly to match the working band. Therefore, the present invention has the flexibility and scalability of wavelength regulation and is not limited to a certain working band.

[0030] 4. By using the wavelength multiplexing metasurface proposed in the present invention for illumination, only one dual-light field illumination image needs to be taken during HiLo optical sectioning microscopy to reconstruct a high-resolution image, thus avoiding the switching of illumination light in traditional HiLo imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1An overall schematic diagram of a metasurface provided by an embodiment of the present invention;

[0032] Figure 2 A schematic diagram of a basic unit structure of a metasurface provided by an embodiment of the present invention;

[0033] Figure 3 A phase scanning result diagram of a metasurface structure unit provided by an embodiment of the present invention;

[0034] Figure 4 A phase distribution diagram of a structured illumination light and a uniform illumination light design provided by an embodiment of the present invention;

[0035] Figure 5 A light field distribution diagram of sinusoidal structured light generated by a metasurface provided in an embodiment of the present invention;

[0036] Figure 6 A metasurface provided in an embodiment of the present invention generates a uniform plane wave light field distribution diagram;

[0037] Figure 7 The embodiment of the present invention provides Figure 5 Light intensity distribution at the middle white dashed line;

[0038] Figure 8 The embodiment of the present invention provides Figure 6 Light intensity distribution at the white dashed line in the middle. DETAILED DESCRIPTION

[0039] The following will be combined with the accompanying drawings and specific examples to clearly and completely describe the implementation methods, principle designs and technical effects of the present invention. The following examples are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the scope of protection of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0040] The structure of the wavelength multiplexing metasurface for snapshot HiLo optical sectioning microscopy imaging of the present invention is a universal structure, such as Figure 1 , Figure 2 As shown, it includes a transparent substrate and a plurality of basic unit structures arranged on the transparent substrate, wherein the basic unit structure is a dielectric nanoantenna, and the dielectric nanoantenna includes a lattice and a dielectric nanocolumn arranged at the center of the upper surface of the lattice; the size of the basic unit structure is sub-wavelength; and the shape of the transparent substrate is square. The method specifically includes the following steps:

[0041] Step 1: Based on the transmission phase control principle, analyze the response mechanism between the basic unit structure and the incident light, determine the relationship curves between the transmission phase and the transmission phase difference at two working wavelengths and the structural parameters of the dielectric nanocolumns, and establish a basic unit structure phase library. It includes the following sub-steps:

[0042] Step 11, using electromagnetic simulation software, obtain a relationship curve between the transmission phase and the bottom diameter D of the dielectric nanorod at two working wavelengths.

[0043] The specific operation is as follows: when the incident light is 532nm, the height H of the dielectric nanocolumn is fixed at 700nm, and the bottom diameter D of the dielectric nanocolumn is scanned in the range of 0.2P to 0.8P, where P refers to the side length of the lattice and the scanning interval is 1nm, so as to establish the first transmission phase point by point Similarly, when the incident light is 633nm, the height H of the dielectric nanocolumn is fixed at 700nm, and the bottom diameter D of the dielectric nanocolumn is scanned in the range of 0.2P to 0.8P, with a scanning interval of 1nm, so as to establish the second transmission phase point by point The relationship curve between the bottom diameter D of the dielectric nanocolumn and the transmission phase can be obtained according to the following transmission phase control principle in electromagnetic simulation software:

[0044]

[0045] in, is the transmission phase; n eff is the effective refractive index, which is determined by the bottom diameter D of the dielectric nanorod. By changing the bottom diameter D of the dielectric nanorod, the transmission phase Covering 0~2π, to meet the needs of phase control; the height H of the dielectric nanocolumn is 700nm; λ i is the wavelength of incident light, λ1 and λ2 are 532nm and 633nm respectively. (λ1 and λ2 are selected according to the requirements of incident light)

[0046] Step 12: Calculate the transmission phase difference between the two working wavelengths And draw a curve of its relationship with the bottom diameter D of the dielectric nanocolumn, and the calculation formula is:

[0047]

[0048] Figure 3 A phase scanning result diagram of a super surface structure unit provided in this embodiment, such as Figure 3 As shown, The relationship curve between the bottom diameter D of the dielectric nanocolumn is used as the data basis to establish the basic unit structure phase library.

[0049] Step 2: Determine the design phase of uniform illumination light and structured illumination light and the target phase difference between uniform illumination light and structured illumination light. The details are as follows:

[0050] Figure 4 A phase distribution diagram of a structured illumination light and a uniform illumination light design provided in this embodiment. For the sinusoidal stripes required for the structured illumination light, the metasurface design phase at this working wavelength is determined based on the phase distribution of the phase-type sinusoidal grating. The design phase distribution of the sinusoidal stripe structured illumination light realized by the wavelength multiplexing metasurface is:

[0051]

[0052] The horizontal coordinate x of the basic unit structure ranges from -10 to 10 μm; the sinusoidal modulation parameter m = π / 2; the period interval L = 500 nm; the reference phase

[0053] As described in formula (3), we can get that at different horizontal coordinates x, for λ1, For λ2,

[0054] For the plane wave required for uniform light, the designed phase distribution of the wavelength multiplexing metasurface to achieve uniform illumination light is:

[0055]

[0056] Among them, for λ1, For λ2,

[0057] Calculate the target phase difference at two working wavelengths:

[0058]

[0059] It can be obtained that for λ1, For λ2,

[0060] Step 3: Calculate the target phase difference according to step 2 In the basic unit structure phase library established in step 1, select the phase difference equal to the target at two working wavelengths. The height H of the selected dielectric nanocolumns is 700 nm, the bottom diameters D are 109 nm and 118 nm respectively, and the side length P of the lattice is 350 nm. The selected dielectric nanocolumns with two different bottom diameters D are arranged according to the design phase distribution equation described in formula (3) to establish a wavelength multiplexing metasurface structure, in which the side length of the transparent substrate is 20 μm.

[0061] Since the basic unit structure size is at the sub-wavelength level, the metasurface of the present invention has the characteristics of planarization, light weight, and easy photon integration, so the metasurface of the present invention is suitable for the miniaturization of optical systems.

[0062] The light field distribution diagram of the metasurface at different working wavelengths is calculated by electromagnetic simulation software. Figure 5 A metasurface provided in an embodiment of the present invention generates a light field distribution diagram of a sinusoidal structured light, such as Figure 5 As shown, under the condition that the incident light wavelength is 633nm, the metasurface generates sinusoidal stripe structured light with a period interval of 500nm and a stripe size of 700nm. Figure 7 A metasurface provided in an embodiment of the present invention generates a uniform plane wave light field distribution diagram, such as Figure 7 As shown, when the incident light wavelength is 532nm, the metasurface generates a plane wave with uniform intensity. Figure 7 The embodiment of the present invention provides Figure 5 Light intensity distribution at the white dashed line. Figure 8 The embodiment of the present invention provides Figure 6 Light intensity distribution at the white dashed line.

[0063] The light field distribution and light intensity distribution results shown in the above figures indicate that the wavelength multiplexing metasurface proposed in the technical solution of the present invention can realize the wavelength multiplexing function for incident lights of two different wavelengths. When light with a wavelength of λ1 is incident on the metasurface, a phase-flat uniform illumination light is generated; when light with a wavelength of λ2 is incident on the metasurface, a structured illumination light with a sinusoidal stripe distribution is generated; when a dual-wavelength mixed-color light source with a wavelength of λ1 and a wavelength of λ2 sharing a common optical path is used as the incident light, the metasurface can simultaneously generate the two illumination lights required for HiLo microscopy, which can meet the two illumination light requirements for HiLo optical sectioning microscopy.

[0064] Therefore, the metasurface can realize the function of reconstructing high-resolution images with a single shot acquisition. Compared with conventional HiLo microscopy technology, the method of the present invention can effectively improve the imaging speed and imaging stability and reduce the complexity of the imaging and reconstruction process.

Claims

1. A design method for wavelength multiplexing metasurface for snapshot HiLo optical sectioning microscopy, characterized in that: The specific steps include: Step 1: Determine the relationship curves between the transmission phase and the transmission phase difference under the two working wavelengths of uniform illumination light and structured illumination light and the structural parameters of the dielectric nanocolumns, and establish a basic unit structure phase library; Step 2: Determine the target phase difference between the uniform illumination light and the structured illumination light: When the wavelength of the incident light is λ1, the target phase of the structured illumination light is: When the wavelength of the incident light is λ2, the target phase of the uniform illumination light is: Among them, x is the horizontal coordinate of the basic unit structure; m is the sinusoidal modulation parameter; L is the period interval; is the reference phase; C is a constant; subscripts 1 and 2 represent two working wavelengths respectively; Calculate the target phase difference at two working wavelengths: Step 3: Select the basic structural unit library obtained in step 1 that has a phase difference equal to the target at two working wavelengths. The two selected dielectric nanocolumns are arranged according to the designed phase distribution equation to obtain a wavelength multiplexing metasurface structure, and the designed phase distribution equation is as follows:

2. The method for designing a wavelength multiplexing metasurface for snapshot HiLo optical sectioning microscopy as claimed in claim 1, characterized in that: The step 1 is performed by electromagnetic simulation software. In the electromagnetic simulation software, the transmission phase is obtained according to the following transmission phase control principle: in, is the transmission phase; n eff is the effective refractive index; H is the height of the dielectric nanocolumn; λ1 and λ2 are the wavelengths of the two incident lights, respectively.

3. The method for designing a wavelength multiplexing metasurface for snapshot HiLo optical sectioning microscopy as claimed in claim 2, characterized in that: λ1 is 532nm, λ2 is 633nm; H=700nm, P=350nm.

4. A wavelength multiplexing metasurface for snapshot HiLo optical sectioning microscopy, characterized in that: It is designed by the wavelength multiplexing metasurface method for snapshot HiLo optical sectioning microscopy imaging described in claim 1.

5. The wavelength multiplexing metasurface for snapshot HiLo optical sectioning microscopy according to claim 4, characterized in that: It comprises a transparent substrate and a plurality of basic unit structures arranged on the transparent substrate, wherein the basic unit structure is a dielectric nano-antenna, and the dielectric nano-antenna comprises a lattice and a dielectric nano-column arranged at the center of the upper surface of the lattice; The lattice is a cube with a side length P of 350nm. The dielectric nanocolumns are cylindrical with a height H of 700nm. The bottom diameter D has two specifications: 109nm and 108nm. The transparent substrate is in a square shape. The dielectric nanocolumns with two bottom diameters are arranged according to the designed phase distribution equation, which is as follows: Among them, x is the horizontal coordinate of the basic unit structure; m is the sinusoidal modulation parameter; L is the period interval; is the reference phase; C is a constant; subscripts 1 and 2 represent two working wavelengths respectively.

Images