Light sheet generators, optical fibers, and imaging systems

Abstract

The present invention discloses a light sheet generator, which includes a metasurface configured to diffract light having a predetermined wavelength, wherein the metasurface includes a first micro-nano structure and a second micro-nano structure respectively located on both sides of a reference line, wherein the first micro-nano structure and the second micro-nano structure each include a plurality of micro-nano units, and are configured to introduce a phase change to the light incident on the first micro-nano structure and the second micro-nano structure, so that the light diffracted by the first micro-nano structure and the light diffracted by the second micro-nano structure interfere constructively in a predetermined sheet-like region, thereby generating a light sheet. The present invention also discloses an optical fiber for use with a metasurface and an optical microscopic imaging device having the above-mentioned light sheet generator. According to the present invention, by utilizing the characteristics of the small size and strong light field control capability of the metasurface, the problems of large size and difficult integration of existing light sheet generation systems can be at least partially overcome.

Description

Technical Field

[0001] The present invention relates to optical technology based on metasurface, and in particular to a light sheet generator based on metasurface, an optical fiber used for the light sheet generator, and an imaging system having the light sheet generator. Background Art

[0002] In recent years, people have proposed the new concept of metasurface. Metasurface is a planar structure that can control the wavefront of a light beam. It is composed of densely arranged micro-nano units, and each unit structure has a subwavelength (smaller than the wavelength of light) size. For the light band, subwavelength means the size is in the micrometer or nanometer scale. Therefore, the structure that constitutes the metasurface can be called a micro-nano structure. On the one hand, the metasurface has a powerful ability to manipulate the light field, and has the advantages of low loss, easy integration, and simple preparation process, which makes it have broad application prospects; on the other hand, new applications of metasurfaces are still waiting for people to continue to explore.

[0003] At the same time, beam shaping technology is widely used in different fields. Depending on the field, the shaped beam can have different forms, such as flat-top beam, Airy beam, etc. In the fields of fluorescence microscopy and medical imaging, light sheets play an irreplaceable role. The existing light sheet forming technology is generally based on cylindrical lenses, such as Figure 1 As schematically shown, the incident light beam is spatially converged through a cylindrical lens a to form a linear light source; the light spot within the range of two Rayleigh distances centered on the focal position of the linear light source is usually used as a sheet light beam, for example, as an illumination light sheet in a fluorescence microscopy imaging system. However, the inventors of the present invention have found that the light sheet forming device based on a cylindrical lens is large in size, difficult to integrate, and difficult to implement in some environments. Therefore, a new light sheet forming technology is needed. Summary of the invention

[0004] The object of the present invention is to provide a light sheet forming technology based on a metasurface to at least partially overcome the deficiencies in the existing light sheet forming technology.

[0005] According to one aspect of the present invention, a light sheet generator is provided, comprising a metasurface configured to diffract light having a predetermined wavelength, the metasurface comprising a first micro-nano structure and a second micro-nano structure respectively located on both sides of a reference line, the first micro-nano structure and the second micro-nano structure each comprising a plurality of micro-nano units, and configured to introduce a phase change to light incident on the first micro-nano structure and the second micro-nano structure, so that the light diffracted by the first micro-nano structure and the light diffracted by the second micro-nano structure interfere constructively in a predetermined sheet-like area, thereby generating a light sheet.

[0006] Preferably, the sheet-like region extends substantially perpendicular to the supersurface.

[0007] Preferably, the optical sheet has a length l, a width w and a thickness d, and l≥2d, w≥2d, and the full width at half maximum of the optical sheet in the thickness direction is less than or equal to 10 μm, preferably less than or equal to 2 μm.

[0008] In some embodiments, the first phase change δ introduced by the micro-nano units in the first micro-nano structure and the second micro-nano structure at positions symmetrical about the reference line is 1 and the second phase change δ 2 , satisfying δ 1 =δ 2 .

[0009] In some other embodiments, the first phase change δ introduced by the micro-nano units located at positions symmetrical about the reference line in the first micro-nano structure and the second micro-nano structure is 1 and the second phase change δ 2 , satisfying δ 1 -δ 2 =(2m+1)π, where m is an integer.

[0010] The first micro-nano structure and the second micro-nano structure may be configured to diffract light incident therein and form two plane waves respectively.

[0011] Alternatively, the first micro-nanostructure and the second micro-nanostructure can be configured to diffract the light incident therein and form two curved surface waves, respectively, and preferably, the sections of the wavefronts of the two curved surface waves in the cross section perpendicular to the reference line have a tangent slope that gradually decreases as they move away from the reference line.

[0012] Preferably, the plurality of micro-nano units of the first micro-nano structure and the second micro-nano structure are arranged at first periodic intervals in a direction perpendicular to the reference line. The plurality of micro-nano units of the first micro-nano structure may constitute a plurality of first micro-nano unit groups arranged at second periodic intervals along the direction of the reference line, and the plurality of micro-nano units of the second micro-nano structure may constitute a plurality of second micro-nano unit groups arranged at second periodic intervals along the direction of the reference line. Preferably, the plurality of first micro-nano unit groups have the same structure; the plurality of second micro-nano unit groups also have the same structure. In addition, the first period is preferably equal to the second period.

[0013] Preferably, the light sheet generator further comprises an optical fiber, the metasurface is arranged on the exit end face of the optical fiber, and the light emitted from the optical fiber is diffracted by the metasurface to generate the light sheet. The optical fiber preferably has a core with an oblong cross-section.

[0014] Preferably, the optical fiber is configured to form an output light having more than one light intensity extreme value at the output end face, the light intensity distribution of the output light is symmetrical about the reference line, and the output light is incident on the first micro-nano structure and the second micro-nano structure. To this end, the optical fiber may have more than one core and / or at least one core of the optical fiber has a high-order mode.

[0015] Preferably, the optical fiber has two fiber cores that are symmetrical about the reference line, and the two fiber cores have oblong cross-sections.

[0016] In some advantageous embodiments, the metasurface may further include at least one auxiliary micro-nano structure, the at least one auxiliary micro-nano structure including a plurality of micro-nano units and configured to cause a phase change to the light incident on the auxiliary micro-nano structure, so that the light diffracted by the at least one auxiliary micro-nano structure causes interference in at least a portion of the sheet-like region, thereby adjusting the light intensity distribution of the light sheet. The at least one auxiliary micro-nano structure may cause constructive interference at least in a local region of the sheet-like region, thereby increasing the light intensity in the local region. Alternatively or additionally, the at least one auxiliary micro-nano structure may cause destructive interference at least in a local region of the sheet-like region, thereby reducing the light intensity in the local region.

[0017] Preferably, the at least one auxiliary micro-nano structure comprises at least a third micro-nano structure and a fourth micro-nano structure, and positions of the third micro-nano structure and the fourth micro-nano structure are symmetrical about the reference line.

[0018] In some embodiments, the third phase change δ introduced by the micro-nano units in the third micro-nano structure and the fourth micro-nano structure at positions symmetrical about the reference line is 3 and the fourth phase change δ 4 , satisfying δ 3 =δ 4 .

[0019] In some other embodiments, the third phase change δ introduced by the micro-nano units in the third micro-nano structure and the fourth micro-nano structure at positions symmetrical with respect to the reference line is 3 and the fourth phase change δ 4 , satisfying δ 3 -δ 4 =(2n+1)π, where n is an integer.

[0020] Preferably, the third micro-nano structure and the fourth micro-nano structure are arranged outside the first micro-nano structure and the second micro-nano structure respectively relative to the reference line.

[0021] In some advantageous embodiments, the light sheet generator may further include an optical fiber, the metasurface is disposed on an exit end face of the optical fiber, the optical fiber is configured to form an exit light having more than one light intensity extreme value on the exit end face, and the exit light is incident on the first micro-nano structure, the second micro-nano structure and the at least one auxiliary micro-nano structure. To this end, the optical fiber may have more than one core and / or at least one core of the optical fiber may have a high-order mode.

[0022] In some embodiments, the optical fiber may have at least one main fiber core corresponding to the first micro-nanostructure and the second micro-nanostructure of the metasurface and at least one auxiliary fiber core corresponding to at least one auxiliary micro-nanostructure of the metasurface.

[0023] Preferably, the at least one auxiliary fiber core comprises at least two auxiliary fiber cores symmetrically arranged about the reference line.

[0024] Preferably, the at least one main fiber core comprises two main fiber cores symmetrically arranged about the reference line.

[0025] Preferably, the optical fiber has two main fiber cores with elongated cross sections which are symmetrically arranged about the reference line, and two auxiliary fiber cores with elongated cross sections which are symmetrically arranged about the reference line and located outside the two main fiber cores.

[0026] In some embodiments, the plurality of micro-nano units are directly formed on the exit end face of the optical fiber and are configured to have the same height in the axial direction of the optical fiber and to have micro-nano columns of different sizes in at least one direction perpendicular to the axial direction of the optical fiber.

[0027] According to another aspect of the present invention, there is also provided an optical fiber for use with a metasurface, which is configured to form an output light having more than one light intensity extreme value at an output end face. To this end, the optical fiber may have more than one core and / or at least one core of the optical fiber has a high-order mode.

[0028] Preferably, the core of the optical fiber is symmetrical about a reference line.

[0029] In some embodiments, the optical fiber has two cores that are symmetrical about the reference line, and the two cores have prolate cross-sections.

[0030] In some embodiments, the optical fiber has at least one main fiber core and at least two auxiliary fiber cores, the at least one main fiber core is symmetrical about the reference line, and the at least two auxiliary fiber cores are symmetrically arranged about the reference line and are located outside the main fiber core. Preferably, the at least one main fiber core includes two main fiber cores symmetrically arranged about the reference line.

[0031] In some embodiments, the optical fiber has two main fiber cores with elongated cross sections symmetrically arranged about the reference line and two auxiliary fiber cores with elongated cross sections symmetrically arranged about the reference line and located outside the two main fiber cores.

[0032] Preferably, the cross section of the main fiber core is larger than the cross section of the auxiliary fiber core.

[0033] According to another aspect of the present invention, there is also provided an optical microscopic imaging device, comprising an illumination system and a detection system, wherein the illumination system comprises the light sheet generator as described above. The optical microscopic imaging device may be a fluorescence microscopic imaging device, wherein the light sheet generated by the light sheet generator is projected onto a sample to excite fluorescence. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0035] Figure 1 A schematic diagram of the prior art of forming a light sheet using a cylindrical lens;

[0036] Figure 2 is a schematic diagram of an example of a light sheet generator according to an embodiment of the present invention;

[0037] Figure 3 is a schematic diagram of another example of a light sheet generator according to an embodiment of the present invention;

[0038] Figure 4 are schematic structural diagrams of several examples of optical fibers that can be used in a light sheet generator according to an embodiment of the present invention;

[0039] Figure 5 A schematic diagram of a micro-nano unit that can be used for a light sheet generator;

[0040] Figure 6 is a schematic diagram of the optical principle of a light sheet generator based on plane wave interference according to an embodiment of the present invention;

[0041] Figure 7 Schematic diagrams of two examples of optical fiber output light modes that can be used for a light sheet generator according to an embodiment of the present invention;

[0042] Figure 8 A schematic diagram of a phase change introduced by a metasurface of a light sheet generator according to a first embodiment of the present invention;

[0043] Fig. 9 A partial schematic diagram of an example of the arrangement of the super-surface micro-nano structure of the light sheet generator according to the first embodiment of the present invention;

[0044] Fig.10 Shows that there is Fig. 9 Simulation results of the light sheet formed by the light sheet generator of the micro-nano structure shown;

[0045] Fig.11 A schematic diagram showing a phase change introduced by a metasurface of a light sheet generator according to a second embodiment of the present invention;

[0046] Fig.12 A partial schematic diagram of an example of the arrangement of the super-surface micro-nano structure of the light sheet generator according to the second embodiment of the present invention;

[0047] Fig.13 A partial schematic diagram of an example of the arrangement of the super-surface micro-nano structure of the light sheet generator according to the third embodiment of the present invention;

[0048] Fig.14 Shows that there is Fig.13 The simulation results of multiple light sheets formed by the light sheet generator of the micro-nano structure shown;

[0049] Fig.15 A schematic diagram of a situation in which a light sheet generator according to an embodiment of the present invention forms a light sheet based on curved wave interference;

[0050] Fig.16 A schematic diagram of another situation in which a light sheet generator according to an embodiment of the present invention forms a light sheet based on curved wave interference;

[0051] Fig.17 Schematically shows Fig.16 A situation of phase change introduced by the metasurface of the light sheet generator, in which the light incident on the first and second micro-nano structures has the same phase;

[0052] Fig.18 Another situation of phase change introduced by the metasurface of the curved wave-based light sheet generator is schematically shown, where the phases of the light incident on the first and second micro-nano structures differ by π;

[0053] Fig.19 is a schematic diagram of a light sheet generator with auxiliary micro-nano structures according to a fourth embodiment of the present invention;

[0054] Fig. 20 Schematically shows Fig.19 The structure of the optical fiber in the light sheet generator and the output light thereof;

[0055] Fig.21 for Fig.19 A schematic diagram of an example of a phase change introduced by a metasurface of a light sheet generator;

[0056] Fig. 22 for Fig.19 A partial schematic diagram of an example of the arrangement of the super-surface micro-nanostructure of the light sheet generator shown;

[0057] Fig.23 Shows that there is Fig. 22 The simulation results of the light sheet formed by the light sheet generator of the micro-nano structure shown, wherein the light intensity distribution in the xz plane and the yz plane is shown;

[0058] Fig.24 Shows that there is Fig. 22 The simulation results of the light sheet formed by the light sheet generator of the micro-nano structure shown, wherein the light intensity distribution along the z-axis and along the x-axis is shown;

[0059] Fig.25 and Fig.26 FIG. 4 shows the simulation results of the light sheet formed by the light sheet generator according to the comparative example of the fourth embodiment of the present invention, wherein Fig.25 shows the light intensity distribution in the xz plane, Fig.26 shows the light intensity distribution along the z-axis; and

[0060] Fig. 27 An optical microscopic imaging device according to an embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0061] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0062] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0063] First, refer to Figure 2 and Figure 3 The light sheet generator according to an embodiment of the present invention is summarized. Figure 2 and Figure 3As shown, the light sheet generator 1 according to an embodiment of the present invention includes a metasurface 10 configured to diffract light having a predetermined wavelength, the metasurface 10 includes a first micro-nano structure 11 and a second micro-nano structure 12 respectively located on both sides of a reference line 10a, and the first micro-nano structure 11 and the second micro-nano structure 12 each include a plurality of micro-nano units 10b. Here, the predetermined wavelength may be a certain wavelength or a certain wavelength range. As will be described in detail below in conjunction with more drawings, according to an embodiment of the present invention, the plurality of micro-nano units 10b included in the first micro-nano structure 11 and the second micro-nano structure 12 are configured to introduce a phase change to the light incident on the first micro-nano structure 11 and the second micro-nano structure 12, so that the light diffracted by the first micro-nano structure 11 and the light diffracted by the second micro-nano structure 12 interfere constructively in a predetermined sheet-like region, thereby generating a light sheet LS (see Figure 5 , Fig.15 , Fig.16 , Fig.19 ). The light sheet LS preferably extends substantially perpendicular to the metasurface 10.

[0064] In some embodiments, assuming that the light sheet LS has a length l, a width w and a thickness d, preferably l≥2d, w≥2d. In addition, the full width at half maximum (FWHM) of the light sheet LS in its thickness direction is less than or equal to 10 μm, preferably less than or equal to 2 μm.

[0065] exist Figure 2 In the example shown, the metasurface 10 is formed on a specially provided, for example, sheet-shaped substrate 1a. The substrate 1a plays a supporting role, and the substrate is preferably formed of a material that has no significant absorption of the working wavelength of the light sheet generator. When in use, light with a predetermined working wavelength can be irradiated on the side of the light sheet generator 1 opposite to the metasurface 10, and the light is transmitted through the substrate 1a and phase-modulated by the micro-nano units 10b of the first micro-nano structure 11 and the second micro-nano structure 12 in the metasurface 10. The phase-modulated light interferes constructively in the sheet-shaped region to form a light sheet.

[0066] Figure 3 A preferred example is shown, in which a dedicated substrate 1a is no longer provided, but the metasurface 10 is directly formed on the output end face of the optical fiber 20, so that the light emitted from the optical fiber 20 is diffracted by the metasurface 10 to generate a light sheet. The metasurface 10 can at least partially cover the end face of the core 21 of the optical fiber 20. It should be understood that the present invention is not limited in this respect.

[0067] The integration of the metasurface 10 and the optical fiber 20 is conducive to fully combining and utilizing the advantages of the small size of the metasurface, the strong light field control ability and the good flexibility of the optical fiber. The integration of the metasurface 10 and the optical fiber 20 to form the light sheet generator 1 according to the embodiment of the present invention does not require strict spatial collimation and coupling optical paths, which is conducive to obtaining advantages such as high resolution, high integration, small structure, flexible operation, system stability and strong anti-interference ability, and overcomes the shortcomings of the traditional light sheet generation system, which is large in size and difficult to integrate.

[0068] According to the embodiment of the present invention, the optical fiber used for the light sheet generator 1 may have different structures and types. Figure 4 As shown, conventional single-mode optical fiber, few-mode optical fiber, and multimode optical fiber (see Figure 4 (a) of the ), or a specially designed optical fiber (see Figure 4 Preferably, the core 21 of the light 20 has an axial symmetry. Figure 4 As shown, the specially designed optical fiber used for the light sheet generator 1 according to the embodiment of the present invention preferably has a core with a prolate cross-section.

[0069] In order to facilitate the formation of a sharper and / or uniform light sheet, preferably, the optical fiber 20 is configured to form an output light having more than one light intensity extreme value at the output end face, the light intensity distribution of the output light is symmetrical about the reference line 10a, and is incident on the first micro-nano structure 11 and the second micro-nano structure 12. The output light having more than one light intensity extreme value can be achieved by, for example, an optical fiber having more than one core and or an optical fiber having at least one core with a high-order mode. In some preferred embodiments, such as Figure 4 As shown in parts (b), (c), and (d) of FIG. 1 , the optical fiber 20 may have a plurality of Figure 4 The two fiber cores 20B, 20C, and 20D are symmetrical (not shown), and the two fiber cores 20B, 20C, and 20D have a cross section of a flat and long shape. However, it should be understood that Figure 4 The examples shown are only some examples of optical fibers that can be used in the light sheet generator according to the embodiment of the present invention, and the present invention is not limited in this respect. In addition, other examples of optical fibers that can be used in the light sheet generator 1 will be introduced below in conjunction with specific embodiments.

[0070] By setting different micro-nano units 10b at different positions in the metasurface 10, phase changes are introduced to control the wavefront emitted by the metasurface 10. Figure 5 Schematically shown are several examples of micro-nano units that can be used in a light sheet generator according to an embodiment of the present invention. Figure 5 As shown, the micro-nano unit 10b used for the metasurface 10 can be constructed as a column (such as Figure 5(a), (b), (c), (d), (e) in FIG. 1 ), or it can be constructed as a groove structure (such as Figure 5 As shown in part (f) of FIG. 1 ), the micro-nano units usually used in the metasurface have a uniform height H in the direction perpendicular to the metasurface, and the effect of the micro-nano units on the phase can be adjusted by controlling the length L and width W of the micro-nano units.

[0071] In different embodiments, the light sheet generator may or may not have polarization selectivity according to the shape of the micro-nano unit. When a micro-nano unit with a cross section of a shape such as a rectangle or an ellipse with different sizes in one direction and another direction is used, the size of the cross section of the micro-nano unit in one direction can be changed while keeping the size in the other direction unchanged (for example, only changing the length or width of the rectangle of the cross section of different micro-nano units, or only changing the major axis or minor axis of the ellipse), so that phase modulation is only generated for the incident light polarized in the direction where the size changes, thereby achieving polarization selectivity of phase modulation. On the contrary, when a micro-nano unit with a cross section of a shape such as a square or a circle with the same size in two directions is used, by changing the size in two directions in the same way (for example, changing the side length of the square or the radius of the circle), phase regulation can be achieved for light polarized in both directions. In other words, phase modulation without polarization selectivity can be achieved.

[0072] The micro-nano units of the column structure can be selected from, for example, including but not limited to: dielectric materials such as Si (silicon), SiN (silicon nitride), Ge (germanium), TiO2 (titanium dioxide); metal materials such as Au (gold), Ag (silver), Cu (copper); and tunable materials such as liquid crystal, ITO (indium tin oxide), and lithium niobate.

[0073] The following will take the first micro-nano structure 11 and the second micro-nano structure 12 as examples of forming a plane wave and a curved wave respectively, and introduce different implementations of the light sheet generator 1 in more detail in combination with specific embodiments. It should be understood that the implementation of the light sheet generator based on plane waves and curved waves is only an example, and as long as constructive interference can be formed in the sheet region of the target, the first micro-nano structure 11 and the second micro-nano structure 12 of the light sheet generator 1 according to the embodiment of the present invention can respectively perform various phase modulations on the light wavefront.

[0074] Figure 6 Schematic diagram of the optical principle of the light sheet generator based on plane wave interference. Figure 6As shown, light is incident on the metasurface 10 of the light sheet generator, and after diffraction by the first micro-nanostructure 11 and the second micro-nanostructure 12, two plane waves with wavefronts wf1 and wf2 tilted relative to the metasurface 10 are formed respectively. The reference numerals "v1" and "v2" represent the propagation direction of light, that is, the direction of the wave vector. The first micro-nanostructure 11 and the second micro-nanostructure 12 are constructed so that the phases of the two wavefronts that meet in the predetermined sheet-shaped area are the same or the phase difference is an integer multiple of 2π, so that the two interfere constructively, thereby forming a light sheet LS.

[0075] According to an embodiment of the present invention, preferably, the metasurface of the light sheet generator is designed according to incident light with a plane wavefront. The specific embodiments described below in conjunction with the accompanying drawings are all based on incident light with a plane wavefront as an example, but those skilled in the art should understand that the present invention is not limited in this regard.

[0076] [First embodiment]

[0077] The following reference Figures 7 to 10 A light sheet generator according to a first embodiment of the present invention is introduced. The light sheet generator includes an optical fiber and a metasurface formed on an output end face of the optical fiber. Figure 6 The plane waves shown interfere to form a light sheet.

[0078] In this embodiment, the optical fiber is a few-mode optical fiber with a circular core having a diameter of 25 μm, and the selected output light mode is the fundamental mode (such as Figure 7 The first micro-nanostructure and the second micro-nanostructure of the metasurface have the same phase.

[0079] Assuming that in the plane where the metasurface 10 is located, the direction perpendicular to the reference line 10a is the x direction, and the reference line 10a is the y axis, then according to the first embodiment, the phase change introduced by the multiple micro-nano units 10b of the metasurface of the light sheet generator in the direction perpendicular to the reference line 10a (x direction) is as follows: Figure 8 As shown, the portion where x is greater than zero corresponds to the first micro-nanostructure 111 (see Fig. 9 ) of the micro-nano unit, the part where x is less than zero corresponds to the second micro-nano structure 112 (see Fig. 9 ) The phase change introduced by the micro-nano unit of the first micro-nano structure 111 and the second micro-nano structure 112 is symmetrical about the reference line 10a, and the phase change introduced by each micro-nano structure is repeated with a period of 2π, and in each 2π phase change period, the distance between the micro-nano unit 10b and the reference line 10a is linearly proportional to the magnitude of the phase change introduced by the micro-nano unit.

[0080] According to this embodiment, if a light sheet generator without polarization selectivity is designed for incident light with a wavelength of 1550nm, as an example and not a limitation, the micro-nano unit 10b can be a column with a square cross section formed of silicon material, the height of the column is 1000nm, and the cross-sectional side length of the micro-nano unit 10b is changed to achieve phase regulation. An example of the arrangement of the super-surface micro-nano structure of the light sheet generator according to the first embodiment is as follows Fig. 9 As shown, the first micro-nano structure 111 and the second micro-nano structure 112 are symmetrically distributed about the reference line (y axis), so that the first phase change δ introduced by the micro-nano units 10b located at positions symmetrical to the reference line in the first micro-nano structure 111 and the second micro-nano structure 112 is 1 and the second phase change δ 2 , satisfying δ 1 =δ 2 .exist Fig. 9 In the example shown, the distance between adjacent micro-nano units 10b is 900nm (i.e., they have the same arrangement period of 900nm along the x-direction and along the y-direction), and eight different sizes of micro-nano units 10b are used to cover / simulate the phase change within a 2π period. The side lengths of the square cross-sections of the eight sizes of micro-nano units 10b and the introduced phase changes are shown in Table 1:

[0081] Table 1:

[0082] Serial number 1 2 3 4 5 6 7 8 Phase / rad 0.38 1.18 1.89 2.72 3.49 4.34 5.14 5.89 Side length / nm 150.0 255.0 279.0 291.0 301.0 313.5 324.0 345.5

[0083] exist Fig. 9 In the example shown, it can be seen that the multiple micro-nano units 10b of the first micro-nano structure 111 constitute a plurality of first micro-nano unit groups 111i arranged at periodic intervals along the direction of the reference line (y direction), and the multiple micro-nano units 10b of the second micro-nano structure 112 constitute a plurality of second micro-nano unit groups 112j arranged at periodic intervals along the direction of the reference line (y direction), and the multiple first micro-nano unit groups 111i have the same structure, and the multiple second micro-nano unit groups 112j also have the same structure. In this way, the design of the overall micro-nano structure of the super surface of the light sheet generator can be formed by repeatedly arranging the first micro-nano unit group and the second micro-nano unit group along the y direction, which is conducive to simplifying the design and manufacturing. However, it should be understood that the present invention is not limited to the configuration in which the multiple first micro-nano unit groups have the same structure and / or the multiple second micro-nano unit groups have the same structure. For example, the super surface of the light sheet generator according to an embodiment of the present invention may have, for example, a substantially circular shape, so that the multiple first or second micro-nano unit groups arranged along the y direction may have different numbers of micro-nano units, thereby having different structures.

[0084] In addition, it should be noted that although in the example, the period of arrangement of multiple micro-nano units in the metasurface of the light sheet generator according to an embodiment of the present invention along the x-direction is the same as the period of arrangement along the y-direction, in some other examples, they may also be different.

[0085] Fig.10 Shows that there is Fig. 9 The light field intensity simulation results of the light sheet formed by the micro-nanostructure light sheet generator in the xz plane are shown, where the thickness d of the light sheet in the direction perpendicular to the reference line (x direction) is about 2 μm, and the length l in the direction perpendicular to the metasurface (z direction) is about 8 μm.

[0086] [Second embodiment]

[0087] The following will refer to Fig.11 and Fig.12 A light sheet generator according to a second embodiment of the present invention is described.

[0088] The difference between the second embodiment of the present invention and the first embodiment is that, in the first embodiment, as described above, the light incident on the first micro-nano structure 111 and the second micro-nano structure 112 of the metasurface of the light sheet generator has the same phase; while in the second embodiment, the phase of the light incident on the first micro-nano structure 211 and the second micro-nano structure 212 differs by π. Accordingly, the phase change introduced by the metasurface of the light sheet generator according to the second embodiment is as follows: Fig.11 As shown, the phase change introduced by the first micro-nano structure 211 is compared with Figure 8 The phase change introduced by the first micro-nano structure 111 in the metasurface of the light sheet generator according to the first embodiment is shown to have a misalignment of π.

[0089] In this way, light is incident on the metasurface of the light sheet generator according to the second embodiment, and after diffraction by the first micro-nanostructure 211 and the second micro-nanostructure 212, two plane waves with wavefronts tilted relative to the metasurface are still formed respectively, and the two wavefronts meeting in the predetermined sheet area have the same phase or a phase difference of an integer multiple of 2π, so that the two interfere constructively to form a light sheet LS.

[0090] By way of example only and not limitation, Fig.12 A partial view of an example of a super-surface micro-nano structure arrangement of a light sheet generator according to the second embodiment is shown. Fig.12 The example shown uses Fig. 9The micro-nano units in the example shown have the same shape, size and arrangement spacing, but the difference is that the first micro-nano structure 211 and the second micro-nano structure 212 are not symmetrical with respect to the reference line (y axis), and the micro-nano units in the first micro-nano structure 211 and the second micro-nano structure 212 are arranged so that the first phase change δ introduced by the micro-nano units at the positions symmetrical with respect to the reference line is 1 and the second phase change δ 2 Satisfy δ 1 -δ 2 =(2m+1)π, where m is an integer.

[0091] In the light sheet generator according to an embodiment of the present invention based on plane wave interference, the slope of the outgoing wavefront relative to the metasurface can be controlled by changing the structure and arrangement period of the micro-nano units in the micro-nano structure. The smaller the slope, the larger the light sheet formed in space.

[0092] [Third embodiment]

[0093] In the light sheet generator according to the embodiment of the present invention based on plane wave interference, when the slope of the outgoing wavefront is increased, multiple light sheets will be formed due to the large spatial interference area of ​​the light on both sides of the symmetry axis. Fig.13 and 14 A light sheet generator for forming a plurality of light sheets based on plane wave interference according to a third embodiment of the present invention is described.

[0094] Fig.13 The figure shows a partial example of the arrangement of the super-surface micro-nano structures of the light sheet generator according to the third embodiment of the present invention. It is assumed here that the wavelength of light is 1550nm; the phase difference of the light incident on the first micro-nano structure 311 and the second micro-nano structure 312 is π; the micro-nano unit 10b is a column with a square cross section formed of silicon material, and the height of the column is 1000nm. Fig.13 In the example shown, the distance between adjacent micro-nano units 10b is 600nm (i.e., they have the same arrangement period of 600nm along the x direction and along the y direction), and eight different sizes of micro-nano units 10b are used to cover / simulate the phase change within a 2π period. The side lengths of the square cross sections of the eight sizes of micro-nano units 10b and the introduced phase changes are shown in Table 2:

[0095] Table 2:

[0096] Serial number 1 2 3 4 5 6 7 8 Phase / rad 4.69 5.58 0.19 0.98 1.61 2.36 3.12 3.90 Side length / nm 150.0 240.0 270.0 290.0 301.0 313.5 324.0 345.5

[0097] Thus, the phase change introduced by the multiple micro-nano units 10b in the direction (x direction) perpendicular to the reference line 10a of the metasurface of the light sheet generator according to the third embodiment of the present invention remains the same. Figure 8 shown.

[0098] like Fig.14 As shown, Fig.13 The light sheet generator of the micro-nano structure shown forms a plurality of separated light sheets in space.

[0099] It should be noted that the number of different micro-nano units used to cover / simulate the phase change within a 2π period can be arbitrarily selected. For example, eight micro-nano structures of different sizes as shown in Table 1 can be used to cover the phase of 2π, or more or fewer micro-nano structures can be used to cover 2π, such as 16, 32 or 3. The present invention is not limited in this regard.

[0100] The following introduces a light sheet generator based on curved wave interference according to an embodiment of the present invention. Fig.15 The wavefront wf0 shown by the dotted line in the figure is the spherical wave wavefront focused to the focal point P. In order to constructively interfere with each other in a predetermined sheet-like region to form a light sheet LS, according to an embodiment of the present invention, the curved wavefronts, the first wavefront wf1 and the second wavefront wf2, respectively formed by the first micro-nanostructure 11 and the second micro-nanostructure 12, deviate from the spherical wave wavefront, and make the two wavefronts wf1 and wf2 have the same phase or a phase difference of an integer multiple of 2π when they meet in the predetermined sheet-like region, so that the two wavefronts constructively interfere with each other to form a light sheet LS.

[0101] Fig.15 and Fig.16 Different situations of generating a light sheet based on curved wave interference according to an embodiment of the present invention are respectively shown. Although not shown, it should be understood that Fig.15 and Fig.16 In the illustrated case, in different xz cross sections corresponding to different positions on the y-axis, the phase changes introduced by the first micro-nanostructure 11 and the second micro-nanostructure 12 are the same. Fig.16 As shown, the section lines of the first wavefront wf1 and the second wavefront wf2 in the cross section (xz plane) perpendicular to the reference line (y axis) have tangent slopes that gradually decrease as they move away from the center position (yz plane where the reference line is located).

[0102] Fig.17 Schematically shows Fig.16 A scenario of phase change introduced by the metasurface of the light sheet generator shown, where the light incident on the first and second micro-nanostructures has the same phase. Fig.17 The dashed line schematically shows the Fig.15 The spherical wave front wf0 is shown converging and focusing to point P. The phase change that needs to be introduced by the metasurface is schematically shown in solid lines in order to obtain Fig.16The wavefronts wf1 and wf2 shown in the figure are the phase changes to be introduced by the first micro-nano structure 11 and the second micro-nano structure 12. It can be seen that compared with the formation of the spherical wavefront wf0, in order to obtain the wavefronts wf1 and wf0 used to form the light sheet, the modulation effect of the micro-nano units in the first micro-nano structure 11 and the second micro-nano structure 12 on the phase (amplitude of phase change) gradually decreases as it moves away from the reference line (x=0).

[0103] Corresponds to Fig.17 The phase change shown in FIG. 1 is a phase change of the first phase of the first micro-nano structure 11 and the second micro-nano structure 12. The first phase change δ is introduced by the micro-nano units 10b located at positions symmetrical to the reference line in the first micro-nano structure 11 and the second micro-nano structure 12. 1 and the second phase change δ 2 , satisfying δ 1 =δ 2 .

[0104] Fig.18 Another situation of phase change introduced by the metasurface of the light sheet generator based on curved wave interference is schematically shown, in which the light d incident on the first and second micro-nano structures has a phase difference of π. It can be seen that at this time, as long as the phase difference introduced by the first micro-nano structure 11 and the second micro-nano structure 12 is staggered by π, thereby compensating for the phase difference π between the incident light, a curved wave for realizing a light sheet can also be obtained.

[0105] Corresponds to Fig.18 The phase change shown in FIG. 1 is a phase change of the first phase of the first micro-nano structure 11 and the second micro-nano structure 12. In the metasurface micro-nano structure of the light sheet generator based on curved wave interference according to an embodiment of the present invention, the micro-nano units in the first micro-nano structure 11 and the second micro-nano structure 12 are arranged so that the micro-nano units located at positions symmetrical about the reference line respectively introduce the first phase change δ 1 and the second phase change δ 2 Satisfy δ 1 -δ 2 =(2m+1)π, where m is an integer.

[0106] Fig.15 In the case where the light sheet generator shown in the figure forms a light sheet based on curved wave interference, in order to obtain the wavefronts wf1 and wf2 used to form the light sheet, the curve of the phase change introduced by the first micro-nano structure 11 and the second micro-nano structure 12 (not shown in the figure) can be located at Fig.17 or Fig.18 Between the dashed line and the solid line, in other embodiments, the portion may be located inside the dashed line (closer to the longitudinal axis).

[0107] It should be understood that the light sheet generator according to the embodiment of the present invention is not limited to any specific phase change curve as long as constructive interference can be formed in a predetermined sheet-shaped area through surface wave interference to form a light sheet.

[0108] In the light sheet generator according to the embodiment of the present invention, a light sheet is formed based on the constructive interference of two parts of light from the first micro-nano structure and the second micro-nano structure in the metasurface. However, according to different applications of the light sheet, the light sheet may be required to have a higher uniformity, or there are some special requirements for the light intensity distribution of the light sheet. To this end, the inventor of the present invention further proposed a light sheet generator that also includes at least one auxiliary micro-nano structure in the metasurface, wherein the at least one auxiliary micro-nano structure includes a plurality of micro-nano units and is configured to cause a phase change to the light incident on the auxiliary micro-nano structure, so that the light diffracted by the auxiliary micro-nano structure causes interference in at least a part of the predetermined sheet area, thereby adjusting the light intensity distribution of the light sheet. For example, at least one auxiliary micro-nano structure can cause constructive interference in a local area of ​​the sheet area or cause constructive interference of different degrees in the entire sheet area; or, it can cause destructive interference in a local area of ​​the sheet area or cause destructive interference of different degrees in the entire sheet area; or cause constructive interference in a local area and destructive interference in other local areas, thereby adjusting the light intensity distribution of the light sheet.

[0109] [Fourth embodiment]

[0110] Fig.19 An example of a light sheet generator according to a fourth embodiment of the present invention is schematically shown, and the light sheet generator includes an optical fiber 20' and a metasurface 10' formed on the output end face of the optical fiber 20'. The metasurface 10' includes not only the first micro-nano structure 11 and the second micro-nano structure 12, but also the third micro-nano structure 13 and the fourth micro-nano structure 14. In this embodiment, the third micro-nano structure 13 and the fourth micro-nano structure 14 are located outside the first micro-nano structure 11 and the second micro-nano structure 12, and serve as auxiliary micro-nano structures.

[0111] In this embodiment, the optical fiber can be, for example, a single-mode optical fiber, a few-mode optical fiber, or a multi-mode optical fiber. However, in order to more easily control the distribution of light intensity, Fig.19 As shown, it is preferred to use an optical fiber 20' having a specially designed core structure. Fig. 20 Part (a) of FIG. 2 further illustrates the core structure of the optical fiber 20' through a cross-sectional view. Fig.19 and Fig. 20It can be seen that the optical fiber 20' has two main fiber cores 21a, 21a corresponding to the first micro-nano structure 11 and the second micro-nano structure 12 of the metasurface 10', and two auxiliary fiber cores 21b, 21b corresponding to the third micro-nano structure 13 and the fourth micro-nano structure 14 of the metasurface 10'. Preferably, the two main fiber cores 21a, 21a and the two auxiliary fiber cores 21b, 21b are symmetrically arranged. Preferably, the two main fiber cores 21a, 21a and the two auxiliary fiber cores 21b, 21b each have a flat and long cross-section, for example Fig. 20 The elliptical cross section shown in part (a).

[0112] Return to reference Fig.19 According to the light sheet generator of the fourth embodiment, the first micro-nanostructure 11 and the second micro-nanostructure 12 in the metasurface 10' respectively receive the light from the main cores 21a and 21a of the optical fiber 20' and introduce phase changes, so that the two parts of light (the light parts shown by the solid lines in the figure) interfere constructively in the sheet-like area to form a light sheet LS. The light intensity distribution of the light sheet LS, for example, along the light propagation direction is approximately a Gaussian distribution. In order to increase the uniformity of the light sheet LS along the light propagation direction, the third micro-nanostructure 13 and the fourth micro-nanostructure 14 in the metasurface 10' respectively receive the light from the auxiliary cores 21b and 21b of the optical fiber 20' and introduce phase changes, so that these lights (the light parts shown by the dotted lines in the figure) cause interference in at least part of the predetermined sheet-like area, for example, cause destructive interference in the central part of the predetermined sheet-like area and / or cause constructive interference in the surrounding part of the sheet-like area, thereby adjusting the light intensity distribution of the light sheet LS to be more uniform, for example, making the light sheet LS have along the light propagation direction. Fig.19 The light intensity distribution profile is shown by the midpoint line.

[0113] Fig.21 Schematically shows Fig.19 An example of the phase change introduced by the metasurface of the light sheet generator shown.

[0114] The outgoing light of the optical fiber 20' is as follows Fig. 20 As shown in part (b) of the diagram, assuming that the light emitted from the four fiber cores is a plane wave with the same phase, then Fig.19 The metasurface 10' of the light sheet generator shown can be introduced as Fig.21 The phase changes shown are used to form a light sheet LS and adjust the light intensity distribution of the light sheet. Fig.21 The I, II, III, and IV segments of the phase change curve respectively correspond to the phase changes introduced by the first micro-nano structure 11, the second micro-nano structure 12, the third micro-nano structure 13, and the fourth micro-nano structure 14 in the metasurface 10'. Fig.21In the example shown, the phase changes introduced by the first micro-nanostructure 11 and the second micro-nanostructure 12 are symmetrical about the reference line (the position of x=0), and the micro-nano units in the third micro-nanostructure 13 and the fourth micro-nanostructure 14 located at positions symmetrical about the reference line respectively introduce a third phase change δ 3 and the fourth phase change δ 4 , satisfying δ 3 =δ 4 .

[0115] According to this embodiment, if a light sheet generator with polarization state selectivity is designed for incident light with a wavelength of 532 nm, by way of example only and not limitation, the micro-nano units in the first to fourth micro-nano structures may all be made of, for example, TiO 2 The formed columns are rectangular in cross section, the height of the columns is 600nm, the width of the rectangular cross section is 95nm, and the length of the rectangle is changed to achieve phase control. An example of the arrangement of the super-surface micro-nano structure of the light sheet generator according to the fourth embodiment is as follows Fig. 22 For clarity, Fig. 22 Only the first micro-nano structure 411 and the third micro-nano structure 413 in the micro-nano structure arrangement are enlarged and shown; the second micro-nano structure and the fourth micro-nano structure (not shown in the figure) are symmetrical structures with respect to the reference line (y-axis) with respect to the first micro-nano structure 411 and the third micro-nano structure 413. Fig. 22 In the example shown, the distance between adjacent micro-nano units is 325 nm (i.e., the arrangement period is the same as 325 nm along the x direction and along the y direction), and eight different sizes of micro-nano units 10b are used to cover / simulate the phase change within a 2π period. The eight sizes of micro-nano units 10b have different lengths of rectangular cross sections. The cross-sectional lengths and the corresponding introduced phase changes are shown in Table 3:

[0116] Table 3:

[0117] Serial number 1 2 3 4 5 6 7 8 Phase / rad 0.31 1.08 1.84 2.68 3.33 4.13 5.02 5.81 Length / nm 175.0 193.0 230.0 50.0 95.6 123.0 138.0 160.0

[0118] exist Fig. 22 In the example shown, the length direction of the rectangular cross section of the micro-nano unit is arranged along the x direction, and the width direction is arranged along the y direction. Fig. 22 On the light sheet generator with the arrangement of the metasurface micro-nano structure shown in the figure, a light sheet is formed; however, when the y-direction polarized light is incident on the light sheet generator, no phase adjustment occurs and a light sheet cannot be formed. Therefore, the light sheet generator has polarization state selectivity.

[0119] Fig.23 and Fig.24 Shows that there is Fig. 22Simulation results of the light sheet formed by the light sheet generator with the micro-nano structure shown. Fig.23 Part (a) and part (b) in FIG. 3 show the light intensity distribution of the light sheet in the xz plane and the yz plane, respectively. Fig.23 In the light intensity distribution of the light sheet in the yz plane shown in part (b), it can be seen that the light sheet has a width w of about 10 μm or more along the y-axis direction. Further, Fig.24 Part (a) shows Fig.23 In part (a), the light intensity distribution of the light sheet along the z-axis at position x=0 shows that the light sheet has a relatively wide uniform distribution along the light propagation direction (the full width at half maximum of the main lobe of the light intensity distribution along the z-axis is taken as the length l of the light sheet, which is about 80 μm); Fig.24 Part (b) shows Fig.23 From the light intensity distribution along the x-axis at z=80μm in part (a), it can be seen that the light sheet has a relatively small thickness (the full width at half maximum of the main lobe of the light intensity distribution along the x-axis is taken as the thickness d of the light sheet, and the thickness d is about 1.8μm), and the intensity of the side lobe of the light intensity distribution is significantly lower than the intensity of the main lobe. In general, the light sheet generator according to the fourth embodiment of the present invention achieves a good light sheet shaping effect.

[0120] In order to more clearly show the role of the auxiliary micro-nanostructure in helping to adjust the light intensity distribution of the light sheet, the above reference Figures 19 to 22 The third auxiliary micro-nano structure and the fourth auxiliary micro-nano structure and the two auxiliary fiber cores 21b, 21b in the light sheet generator described above are removed, and the light sheet generator obtained is used as a comparative example of the fourth embodiment, and the light sheet formed by the comparative example is simulated and calculated. The simulation results are shown in FIG. Fig.25 and Fig.26 shown. Fig.25 The light intensity distribution of the light sheet formed in the comparative example in the xz plane is shown. Fig.26 The light intensity distribution along the z-axis is shown. Fig.23 Part (a) of Fig.25 , and contrast Fig.24 Part (a) of Fig.26 It can be seen that the auxiliary micro-nano structure in the metasurface of the light sheet generator according to the fourth embodiment of the present invention and the auxiliary fiber core in the optical fiber have a great regulating effect on the light intensity distribution of the light sheet.

[0121] For the light sheet generator according to the fourth embodiment of the present invention, it should be understood that, depending on the desired light intensity modulation method, the phase changes introduced by the third micro-nano structure 13 and the fourth micro-nano structure 14 are not limited to being the same. In other embodiments, the micro-nano units in the third micro-nano structure 13 and the fourth micro-nano structure 14 located at symmetrical positions with respect to the reference line (x=0) respectively introduce a third phase change δ 3 and the fourth phase change δ 4 Can satisfy δ 3 -δ 4 =(2n+1)π, where n is an integer. In other embodiments, there may be no regular relationship between the phase changes introduced by the third micro-nanostructure 13 and the fourth micro-nanostructure 14. Even in other embodiments, the metasurface 10' of the light sheet generator may have a greater or lesser number of auxiliary micro-nanostructures.

[0122] The optical fiber used in the light sheet generator according to the fourth embodiment of the present invention is preferably capable of forming an output light having more than one light intensity extreme value at the output end face. Fig.19 and Fig. 20 In the light sheet generator described, the optical fiber has multiple cores corresponding to the number of micro-nano structures on the metasurface, so as to flexibly adjust the position of the cores and / or flexibly control the amount of light provided to different micro-nano structures. However, it should be understood that this is not necessary. For example, the optical fiber may have only one core corresponding to the first micro-nano structure and the second micro-nano structure of the metasurface, and the light emitted by the core may be a fundamental mode or a high-order mode corresponding to the first and second micro-nano structures, for example Figure 7 As shown in part (b) of the figure. In addition, for example, the optical fiber may have a core corresponding to the first micro-nano structure and the third micro-nano structure of the metasurface, and a core corresponding to the second micro-nano structure and the fourth micro-nano structure. For another example, the optical fiber may have only one core of a high-order mode, and the core outputs multiple light spots corresponding to different micro-nano structures.

[0123] In addition, it should be understood that the metasurface of the light sheet generator according to the embodiment of the present invention may include other micro-nano structures in addition to the first micro-nano structure, the second micro-nano structure and at least one auxiliary micro-nano structure described above, and the present invention is not limited in this respect.

[0124] The light sheet generator based on the metasurface according to the embodiment of the present invention has the outstanding advantages of small size and strong light field control capability. In particular, when the metasurface is integrated with the optical fiber to form the light sheet generator, the structure of the light sheet generator is further simplified and the stability, anti-interference capability and operational flexibility of the system are provided, so that the light sheet can be applied more widely and conveniently. The inventors of the present invention have found that the light sheet generator according to the embodiment of the present invention is applied to an optical microscopic imaging device.

[0125] Fig. 27 The optical microscopic imaging device according to an embodiment of the present invention is schematically shown, which includes an illumination system and a detection system, wherein the illumination system includes a light sheet generator 1 according to an embodiment of the present invention, and the detection system includes, for example, a detection optical path 2. In some embodiments, the optical microscopic imaging device is a fluorescence microscopic imaging device, such as Fig. 27 As shown, the light sheet LS generated by the light sheet generator 1 is projected onto the sample 3 to excite fluorescence, and then the fluorescence emitted by the sample 3 is detected and imaged by the detection optical path 2 .

[0126] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. A light sheet generator, comprising a metasurface configured to diffract light having a predetermined wavelength, the metasurface comprising a first micro-nano structure and a second micro-nano structure respectively located on both sides of a reference line, the first micro-nano structure and the second micro-nano structure each comprising a plurality of micro-nano units, and configured to introduce a phase change to light incident on the first micro-nano structure and the second micro-nano structure, so that the light diffracted by the first micro-nano structure and the light diffracted by the second micro-nano structure have the same phase or a phase difference of an integer multiple of 2π when they meet in a predetermined sheet-shaped area, so that the two interfere constructively, thereby generating a light sheet, The first micro-nano structure and the second micro-nano structure are configured to diffract incident light therein and form two curved surface waves, respectively, and the wavefronts of the two curved surface waves deviate from the wavefront of the spherical wave.

2. The light sheet generator of claim 1, wherein: The sheet-like region extends substantially perpendicular to the metasurface.

3. The light sheet generator of claim 1, wherein: The optical sheet has a length l, a width w and a thickness d, and l≥2d, w≥2d. The full width at half maximum of the optical sheet in the thickness direction is less than or equal to 10 μm, preferably less than or equal to 2 μm.

4. The light sheet generator of claim 1, wherein: The first phase change δ1 and the second phase change δ2 introduced by the micro-nano units in the first micro-nano structure and the second micro-nano structure at positions symmetrical with respect to the reference line respectively satisfy δ1=δ2.

5. The light sheet generator of claim 1, wherein: The first phase change δ1 and the second phase change δ2 introduced by the micro-nano units in the first micro-nano structure and the second micro-nano structure at positions symmetrical about the reference line respectively satisfy δ1-δ2=(2m+1)π, where m is an integer.

6. The light sheet generator of claim 1, wherein: The section lines of the wavefronts of the two curved surface waves in the cross section perpendicular to the reference line have tangent slopes that gradually decrease as they go away from the reference line.

7. The light sheet generator of claim 1, wherein: The plurality of micro-nano units of the first micro-nano structure and the second micro-nano structure are arranged at first periodic intervals in a direction perpendicular to the reference line.

8. The light sheet generator of claim 7, wherein: The multiple micro-nano units of the first micro-nano structure constitute multiple first micro-nano unit groups arranged at second periodic intervals along the direction of the reference line, and the multiple micro-nano units of the second micro-nano structure constitute multiple second micro-nano unit groups arranged at second periodic intervals along the direction of the reference line.

9. The light sheet generator of claim 8, wherein: The plurality of first micro-nano unit groups have the same structure; the plurality of second micro-nano unit groups also have the same structure.

10. The light sheet generator of claim 8, wherein: The first period is equal to the second period.

11. The light sheet generator according to any one of claims 1 to 10, wherein: The light sheet generator further includes an optical fiber, the metasurface is arranged on an exit end face of the optical fiber, and the light emitted from the optical fiber is diffracted by the metasurface to generate the light sheet.

12. The light sheet generator of claim 11, wherein: The optical fiber has a core having a prolate cross-section.

13. The light sheet generator of claim 11, wherein: The optical fiber is configured to form output light having more than one intensity extreme value at the output end face, the intensity distribution of the output light is symmetrical about the reference line, and the output light is incident on the first micro-nano structure and the second micro-nano structure.

14. The light sheet generator of claim 13, wherein: The optical fiber has more than one core and / or at least one core of the optical fiber has a high-order mode.

15. The light sheet generator of claim 14, wherein: The optical fiber has two cores that are symmetrical about the reference line, and the two cores have a prolate cross-section.

16. The light sheet generator according to any one of claims 1 to 10, wherein: The metasurface also includes at least one auxiliary micro-nano structure, which includes a plurality of micro-nano units and is configured to cause a phase change in light incident on the auxiliary micro-nano structure, so that light diffracted by the at least one auxiliary micro-nano structure causes interference in at least a portion of the sheet-like area, thereby adjusting the light intensity distribution of the light sheet.

17. The light sheet generator of claim 16, wherein: The at least one auxiliary micro-nanostructure causes constructive interference at least in a local region of the sheet-shaped region, thereby increasing the light intensity in the local region.

18. The light sheet generator of claim 16, wherein: The at least one auxiliary micro-nanostructure causes destructive interference at least in a local region of the sheet-shaped region, thereby reducing the light intensity in the local region.

19. The light sheet generator of claim 16, wherein: The at least one auxiliary micro-nano structure includes at least a third micro-nano structure and a fourth micro-nano structure, and positions of the third micro-nano structure and the fourth micro-nano structure are symmetrical about the reference line.

20. The light sheet generator of claim 19, wherein: The third phase change δ3 and the fourth phase change δ4 introduced by the micro-nano units in the third micro-nano structure and the fourth micro-nano structure at positions symmetrical with respect to the reference line respectively satisfy δ3=δ4.

21. The light sheet generator of claim 19, wherein: The third phase change δ3 and the fourth phase change δ4 introduced by the micro-nano units in the third micro-nano structure and the fourth micro-nano structure at positions symmetrical about the reference line respectively satisfy δ3-δ4=(2n+1)π, where n is an integer.

22. The light sheet generator according to any one of claims 19 to 21, wherein: The third micro-nano structure and the fourth micro-nano structure are respectively arranged outside the first micro-nano structure and the second micro-nano structure relative to the reference line.

23. The light sheet generator of claim 16, wherein: The light sheet generator also includes an optical fiber, the metasurface is arranged on the output end face of the optical fiber, and the optical fiber is configured to form output light having more than one light intensity extreme value on the output end face, and the output light is incident on the first micro-nano structure, the second micro-nano structure and the at least one auxiliary micro-nano structure.

24. The light sheet generator of claim 22, wherein: The light sheet generator also includes an optical fiber, the metasurface is arranged on the output end face of the optical fiber, and the optical fiber is configured to form output light having more than one light intensity extreme value on the output end face, and the output light is incident on the first micro-nano structure, the second micro-nano structure and the at least one auxiliary micro-nano structure.

25. The light sheet generator of claim 23 or 24, wherein: The optical fiber has more than one core and / or at least one core of the optical fiber has a high-order mode.

26. The light sheet generator of claim 25, wherein: The optical fiber has at least one main fiber core corresponding to the first micro-nano structure and the second micro-nano structure of the metasurface and at least one auxiliary fiber core corresponding to at least one auxiliary micro-nano structure of the metasurface.

27. The light sheet generator of claim 26, wherein: The at least one auxiliary fiber core includes at least two auxiliary fiber cores symmetrically arranged about the reference line.

28. The light sheet generator of claim 27, wherein: The at least one main fiber core includes two main fiber cores symmetrically arranged about the reference line.

29. The light sheet generator of claim 27, wherein: The optical fiber comprises two main fiber cores with elongated cross sections symmetrically arranged about the reference line and two auxiliary fiber cores with elongated cross sections symmetrically arranged about the reference line and located outside the two main fiber cores.

30. The light sheet generator of claim 11, wherein: The plurality of micro-nano units are directly formed on the exit end face of the optical fiber and are configured to have the same height in the axial direction of the optical fiber and to have micro-nano columns of different sizes in at least one direction perpendicular to the axial direction of the optical fiber.

31. The light sheet generator of claim 23 or 24, wherein: The plurality of micro-nano units are directly formed on the exit end face of the optical fiber and are configured to have the same height in the axial direction of the optical fiber and to have micro-nano columns of different sizes in at least one direction perpendicular to the axial direction of the optical fiber.

32. An optical fiber for use in conjunction with the metasurface of a light sheet generator as described in claim 1, which is constructed to be able to form output light with more than one light intensity extreme value at the output end face, wherein the optical fiber has two fiber cores that are symmetrical about the reference line, and the two fiber cores have a prolate cross-section.

33. The optical fiber of claim 32, wherein: The optical fiber has more than one core and / or at least one core of the optical fiber has a high-order mode.

34. The optical fiber of claim 32 or 33, wherein: The core of the optical fiber is symmetrical about a reference line.

35. The optical fiber of claim 32, wherein: The optical fiber has at least one main fiber core and at least two auxiliary fiber cores, the at least one main fiber core is symmetrical about the reference line, and the at least two auxiliary fiber cores are symmetrically arranged about the reference line and are located outside the main fiber core.

36. The optical fiber of claim 35, wherein: The at least one main fiber core includes two main fiber cores symmetrically arranged about the reference line.

37. The optical fiber of claim 32, wherein: The optical fiber comprises two main fiber cores with elongated cross sections symmetrically arranged about the reference line and two auxiliary fiber cores with elongated cross sections symmetrically arranged about the reference line and located outside the two main fiber cores.

38. The optical fiber of claim 35, wherein: The cross section of each of the main fiber cores is greater than the cross section of each of the auxiliary fiber cores.

39. An optical microscopic imaging device, comprising an illumination system and a detection system, wherein: The illumination system comprises a light sheet generator as claimed in claims 1-31.

40. The optical microscopic imaging device of claim 39, wherein: The optical microscopic imaging device is a fluorescence microscopic imaging device, and the light sheet generated by the light sheet generator is projected onto a sample to excite fluorescence.

Images