Equivalent negative refractive index flat lens and its manufacturing method

Abstract

An equivalent negative refractive index flat lens and a manufacturing method thereof, the method comprising the steps of: (1) forming reflective layers (20) on both opposing sides of a transparent substrate layer (10); (2) forming a protective layer (30) on each reflective layer (20); (3) forming a first bonding metal layer (40) on one of the protective layers (30) and a second bonding metal layer (50) on the other; and (4) stacking at least two flat optical waveguides along a first direction, and the first bonding metal layer (40) of each flat optical waveguide being bonded to an adjacent flat optical waveguide. The method includes a step (4) of contacting the second bonding metal layer (50) of the plate optical waveguide with heat and energization; a step (5) of taking two sets of multilayer planar optical waveguides, cutting one of the multilayer planar optical waveguides into a plurality of first striped planar optical waveguides and cutting the other into a plurality of second striped planar optical waveguides; and a step (6) of overlapping the first optical waveguide array (102) and the second optical waveguide array (103) along a first direction, and then adding protective window sheets (101, 104) on both sides.

Description

[Technical Field]

[0001] The present disclosure relates to the field of optical manufacturing technology, and more particularly to an equivalent negative refractive index planar lens and a method for manufacturing the same. [Background technology]

[0002] The official name of the flat lens is an equivalent negative refractive index flat lens, which uses two layers of periodically distributed arrayed optical waveguides that are mutually orthogonal, and the light undergoes one total reflection within each of the two layers of arrayed optical waveguides, and because of the mutually orthogonal rectangular structure, the incident angle at the first total reflection and the outgoing angle at the second total reflection are the same. After all the light rays within the divergence angle of the light source pass through the flat lens, they converge into a three-dimensional space that is plane-symmetrical to the flat lens, thereby forming a 1:1 floating real image.

[0003] In the conventional technology, the equivalent negative refractive index flat lens manufacturing process uses adhesive to bond the multilayer flat plates and uses spacers, which have high spacer precision requirements and reduce the adhesive strength between the optical waveguides, making the optical waveguide array prone to fracture. Direct bonding with adhesive is prone to introducing air bubbles, and the organic adhesive is prone to hardening shrinkage, resulting in local deformation. Meanwhile, the conventional equivalent negative refractive index flat lens optical waveguide manufacturing process uses resin adhesive to bond the multilayer flat plates, which has a large hardening shrinkage rate and whose hardening is a heat dissipation process, resulting in temperature variations during hardening, making it easy for stress distortion to occur, which adversely affects the quality of the equivalent negative refractive index flat lens.

[0004] Therefore, there is room for improvement in the manufacturing method of the conventional equivalent negative refractive index flat lens. Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure aims to solve at least to some extent one of the technical problems in the related art, and therefore aims to provide an equivalent negative refractive index flat lens and a manufacturing method thereof that avoids stress distortion, improves the imaging quality of the lens, and enhances aging performance. [Means for solving the problem]

[0006] In one aspect of the present disclosure, the present disclosure provides a method for manufacturing an equivalent negative refractive index planar lens, according to an embodiment of the present disclosure, the method comprising: Step (1) of forming a reflective layer on both opposing sides of a transparent substrate layer; (2) forming a protective layer on each of the reflective layers; (3) forming a first bonding metal layer on one side of the protective layer and a second bonding metal layer on the other side to form a planar optical waveguide; Step (4) of stacking at least two of the planar optical waveguides along a first direction, and the first bonding metal layer of one planar optical waveguide is brought into contact with the second bonding metal layer of the adjacent planar optical waveguide, and heating and energizing are performed to integrally form the first bonding metal layer and the second bonding metal layer that are brought into contact with each other, and then annealing is performed to obtain a multilayer planar optical waveguide; (5) taking two sets of the multilayer planar optical waveguides, cutting one of the multilayer planar optical waveguides into a plurality of first striped planar optical waveguides to obtain a first optical waveguide array, and cutting the other into a plurality of second striped planar optical waveguides to obtain a second optical waveguide array, the extension direction of the first striped planar optical waveguides and the extension direction of the second striped planar optical waveguides being perpendicular to each other; The first optical waveguide array and the second optical waveguide array are overlapped along the first direction, and after the overlapping, the extension direction of the first striped plate optical waveguide and the extension direction of the second striped plate optical waveguide are perpendicular to each other; and then, a protective window sheet is added on both sides to obtain an equivalent negative refractive index plate lens (step (6)).

[0007] A method for fabricating an equivalent negative refractive index flat lens according to an embodiment of the present disclosure includes forming a first bonding metal layer and a second bonding metal layer on the protective layers above and below the reflective layer, respectively, to obtain a flat optical waveguide. The flat optical waveguides are then stacked one after the other, and the first and second bonding metal layers of adjacent flat optical waveguides are brought into contact with each other. Then, heating and biasing are performed to allow the metal atoms in the first and second bonding metal layers to diffuse into each other and form an integral metal alloy, thereby bonding adjacent flat optical waveguides to each other via metal. This avoids the need for resin adhesives as in conventional techniques, which can cause stress and strain in the bonding layer. At the same time, using metal as the bonding layer reduces the thickness of the bonding layer, improving imaging quality while also enhancing the stability of the metal and its aging resistance. Annealing is then performed to obtain a multilayer flat optical waveguide. Next, two sets of the multilayer planar optical waveguides are taken, and one set of the multilayer planar optical waveguides is cut into a plurality of first striped planar optical waveguides to obtain a first optical waveguide array, thereby obtaining a first striped optical waveguide array. The other set of multilayer planar optical waveguides is cut into a plurality of second striped planar optical waveguides to obtain a second striped optical waveguide array. The two sets of striped optical waveguide arrays are then stacked, and after stacking, the extension directions of the first striped planar optical waveguide and the second striped planar optical waveguide are perpendicular to each other, thereby achieving aberration-free point-to-point imaging on the object side and the image side. Finally, by adding protective window sheets on both sides, an equivalent negative refractive index planar lens can be manufactured. This method avoids stress-strain in the connecting layer, improves aging performance, and simultaneously improves the imaging quality of the manufactured lens.

[0008] In addition, the method for manufacturing an equivalent negative refractive index flat lens according to the above embodiments of the present disclosure may further have the following additional technical features.

[0009] In some embodiments of the present disclosure, in step (1), the transparent substrate layer has a length of 10 mm to 10,000 mm, a width of 10 mm to 10,000 mm, and a thickness of 0.2 mm to 4 mm.

[0010] In some embodiments of the present disclosure, the material of the transparent substrate layer includes at least one of transparent glass and quartz, and the thickness of the reflective layer is 50 nm to 10 μm.

[0011] In some embodiments of the present disclosure, the material of the reflective layer includes at least one of a metal reflective film and a dielectric reflective film.

[0012] In some embodiments of the present disclosure, the metallic reflective film includes at least one of aluminum, silver, gold, and copper, and the dielectric reflective film is a non-metal oxide film.

[0013] In some embodiments of the present disclosure, in step (2), the thickness of the protective layer is 10 nm to 1 μm.

[0014] In some embodiments of the present disclosure, the material of the protective layer includes at least one of silicon monoxide, magnesium fluoride, silicon dioxide, and aluminum trioxide.

[0015] In some embodiments of the present disclosure, in step (3), the material of the first bonding metal layer along its thickness direction is Ni / Au / In, Ni / Au, Cr / Au, Ni / Au / In, Ti / Au, Cr / Au / Ni / AuGe, Pd, Ti, Pt, Cr / Al / Cr / In, Ti / Cu, AuBe, or Cr / Sn, and the material of the second bonding metal layer along its thickness direction is In / Au / Ni, In / Ni, In / Cr, In / Au / Pt / Ti, Au / Ti, GeAu / Ni / Au / Cr, Pd, Ti, Pt, In / Cr / Al / Cr, Cu / Ti, BeAu, or Sn / Cr, respectively.

[0016] In some embodiments of the present disclosure, the material of the first bonding metal layer along its thickness direction is In / Au / Ni, In / Ni, In / Cr, In / Au / Pt / Ti, Au / Ti, GeAu / Ni / Au / Cr, Pd, Ti, Pt, In / Cr / Al / Cr, Cu / Ti, BeAu, or Sn / Cr, and the material of the second bonding metal layer along its thickness direction is Ni / Au / In, Ni / Au, Cr / Au, Ni / Au / In, Ti / Au, Cr / Au / Ni / AuGe, Pd, Ti, Pt, Cr / Al / Cr / In, Ti / Cu, AuBe, or Cr / Sn, respectively.

[0017] In some embodiments of the present disclosure, in step (3), the thickness ratio of the metal Ni, metal Au, and metal In in the Ni / Au / In is (10-100):(10-100):(10-50).

[0018] In some embodiments of the present disclosure, the thickness ratio of the metallic Ni to the metallic Au in the Ni / Au layer is (10-100):(50-1000).

[0019] In some embodiments of the present disclosure, the thickness ratio of the metal Cr to the metal Au in the Cr / Au layer is (10-100):(50-1000).

[0020] In some embodiments of the present disclosure, the thickness ratio of the metal Ni, metal Au, and metal In in the Ni / Au / In is (10-100):(10-100):(10-100).

[0021] In some embodiments of the present disclosure, the thickness ratio of the metallic Ti to the metallic Au in the Ti / Au is (10-100):(100-3000).

[0022] In some embodiments of the present disclosure, the thickness ratio of the metal Cr, metal Au, metal Ni, and metal AuGe in the Cr / Au / Ni / AuGe is (10-100):(10-100):(10-100):(100-3000).

[0023] In some embodiments of the present disclosure, the thickness of the metallic Pd in ​​the Pd is 50 nm to 3000 nm.

[0024] In some embodiments of the present disclosure, the thickness of the metallic Ti in the Ti is 50 nm to 3000 nm.

[0025] In some embodiments of the present disclosure, the thickness of the metallic Pt in the Pt is 50 nm to 3000 nm.

[0026] In some embodiments of the present disclosure, the thickness ratio of metal Cr, metal Al, metal Cr, and metal In in the Cr / Al / Cr / In is (10-100):(10-100):(10-100):(10-100).

[0027] In some embodiments of the present disclosure, the thickness ratio of the metallic Ti to the metallic Cu in the Ti / Cu is (10-100):(100-3000).

[0028] In some embodiments of the present disclosure, the thickness of the metallic AuBe in the AuBe layer is 50 nm to 3000 nm.

[0029] In some embodiments of the present disclosure, the thickness ratio of the metal Cr to the metal Sn in the Cr / Sn is (10-100):(100-3000).

[0030] In some embodiments of the present disclosure, in step (3), the thickness ratio of the metal In, metal Au, and metal Ni in the In / Au / Ni is (10-50):(10-100):(10-100).

[0031] In some embodiments of the present disclosure, the thickness ratio of the metal In to the metal Ni in the In / Ni is (10-100):(10-100).

[0032] In some embodiments of the present disclosure, the thickness ratio of the metal In to the metal Cr in the In / Cr is (10-100):(10-100).

[0033] In some embodiments of the present disclosure, the thickness ratio of the metal In, metal Au, metal Pt, and metal Ti in the In / Au / Pt / Ti is (10-100):(10-100):(10-100):(10-100).

[0034] In some embodiments of the present disclosure, the thickness ratio of the metallic Au to the metallic Ti in the Au / Ti is (100-3000):(10-100).

[0035] In some embodiments of the present disclosure, the thickness ratio of metal GeAu, metal Ni, metal Au, and metal Cr in the GeAu / Ni / Au / Cr is (100-3000):(10-100):(10-100):(10-100).

[0036] In some embodiments of the present disclosure, the thickness of the metallic Pd in ​​the Pd is 50 nm to 3000 nm, and the thickness of the metallic Ti in the Ti is 50 nm to 3000 nm.

[0037] In some embodiments of the present disclosure, the thickness of the metallic Pt in the Pt is 50 nm to 3000 nm.

[0038] In some embodiments of the present disclosure, the thickness ratio of metal In, metal Cr, metal Al, and metal Cr in the In / Cr / Al / Cr is (10-100), or (10-100):(10-100):(10-100).

[0039] In some embodiments of the present disclosure, the thickness ratio of the metallic Cu to the metallic Ti in the Cu / Ti is (100-3000)(10-100).

[0040] In some embodiments of the present disclosure, the thickness of the metal BeAu in the BeAu layer is 50 nm to 3000 nm.

[0041] In some embodiments of the present disclosure, the thickness ratio of metallic Sn to metallic Cr in the Sn / Cr layer is (100-3000):(10-100).

[0042] In some embodiments of the present disclosure, the biasing pressure is 1 kgf to 50 kgf.

[0043] In some embodiments of the present disclosure, the Ni / Au / In and In / Au / Ni are heated at a temperature of 150° C. to 200° C. for a time of 1 hour to 20 hours.

[0044] In some embodiments of the present disclosure, the Ni / Au and In / Ni are heated at a temperature of 130° C. to 200° C. for a time of 0.2 hours to 5 hours.

[0045] In some embodiments of the present disclosure, the heating temperature of the Cr / Au and the In / Cr is 130° C. to 200° C., and the heating time is 0.2 hours to 5 hours.

[0046] In some embodiments of the present disclosure, the heating temperature of the Ni / Au / In and the In / Au / Pt / Ti is 150° C. to 200° C., and the heating time is 1 hour to 20 hours.

[0047] In some embodiments of the present disclosure, the heating temperature of the Ti / Au and the Au / Ti is 250° C. to 350° C., and the heating time is 1 hour to 12 hours.

[0048] In some embodiments of the present disclosure, the heating temperature of the Cr / Au / Ni / AuGe and the GeAu / Ni / Au / Cr is 150° C. to 220° C., and the heating time is 1 hour to 20 hours.

[0049] In some embodiments of the present disclosure, the Pd is heated to a temperature of 100° C. to 160° C. for a time of 1 hour to 20 hours.

[0050] In some embodiments of the present disclosure, the heating temperature of the Ti is 200° C. to 400° C., and the heating time is 1 hour to 20 hours.

[0051] In some embodiments of the present disclosure, the Pt is heated to a temperature of 200° C. to 400° C. for a time of 1 hour to 20 hours.

[0052] In some embodiments of the present disclosure, the heating temperature of the Cr / Al / Cr / In and the In / Cr / Al / Cr is 150°C to 200°C, and the heating time is 1 hour to 20 hours.

[0053] In some embodiments of the present disclosure, the heating temperature of the Ti / Cu and Cu / Ti is 350° C. to 500° C., and the heating time is 1 hour to 20 hours.

[0054] In some embodiments of the present disclosure, the heating temperature of the AuBe and the AuBe is 150°C to 250°C, and the heating time is 1 hour to 20 hours.

[0055] In some embodiments of the present disclosure, the heating temperature of the Cr / Sn and the Sn / Cr is 90°C to 120°C, and the heating time is 1 hour to 20 hours.

[0056] In some embodiments of the present disclosure, the annealing temperature of the Ni / Au / In and the In / Au / Ni is 230° C. to 300° C., and the annealing time is 0.2 to 5 hours.

[0057] In some embodiments of the present disclosure, the annealing temperature of the Ni / Au and the In / Ni is 300° C. to 450° C., and the annealing time is 0.2 hours to 5 hours.

[0058] In some embodiments of the present disclosure, the annealing temperature of the Cr / Au and the In / Cr is 300° C. to 450° C., and the annealing time is 0.2 hours to 5 hours.

[0059] In some embodiments of the present disclosure, the annealing temperature of the Ni / Au / In and the In / Au / Pt / Ti is 230° C. to 300° C., and the annealing time is 0.2 to 5 hours.

[0060] In some embodiments of the present disclosure, the annealing temperature of the Ti / Au and the Au / Ti is 400° C. to 500° C., and the annealing time is 0.2 hours to 10 hours.

[0061] In some embodiments of the present disclosure, the annealing temperature of the Cr / Au / Ni / AuGe and the GeAu / Ni / Au / Cr is 300° C. to 450° C., and the annealing time is 0.5 to 10 hours.

[0062] In some embodiments of the present disclosure, the annealing temperature of the Pd is 200° C. to 300° C., and the annealing time is 0.1 h to 5 h.

[0063] In some embodiments of the present disclosure, the annealing temperature of the Cr / Al / Cr / In and the In / Cr / Al / Cr is 250° C. to 350° C., and the annealing time is 0.1 h to 5 h.

[0064] In some embodiments of the present disclosure, the annealing temperature of the Ti / Cu and Cu / Ti is 550° C., and the annealing time is 0.3 to 5 hours.

[0065] In some embodiments of the present disclosure, the annealing temperature of the AuBe and the BeAu is 280° C. to 350° C., and the annealing time is 0.1 h to 2 h.

[0066] In some embodiments of the present disclosure, the annealing temperature of the Cr / Sn and the Sn / Cr is 140° C. to 200° C., and the annealing time is 0.5 hours to 5 hours.

[0067] In some embodiments of the present disclosure, step (4) further includes the steps of stacking at least two of the planar optical waveguides along the first direction, providing a first bonding sheet on the stacked planar optical waveguides, and providing a second bonding sheet on one side of the stacked planar optical waveguides away from the first bonding sheet.

[0068] In some embodiments of the present disclosure, the first bonding sheet comprises a transparent substrate layer, reflective layers formed on opposite sides of the transparent substrate layer, protective layers formed on each of the reflective layers, and a second bonding metal layer formed on the bottom surface of the protective layer and abutting the first bonding metal layer of the planar optical waveguide.

[0069] In some embodiments of the present disclosure, the second bonding sheet comprises a transparent substrate layer, reflective layers formed on opposite sides of the transparent substrate layer, protective layers formed on each of the reflective layers, and a first bonding metal layer formed on the protective layers and abutting the second bonding metal layer of the planar optical waveguide.

[0070] In a second aspect of the present disclosure, the present disclosure provides an equivalent negative refractive index planar lens. According to an embodiment of the present disclosure, the equivalent negative refractive index planar lens is manufactured using the above-mentioned method, thereby improving the imaging quality of the lens.

[0071] Additional aspects and advantages of the disclosure will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the disclosure.

[0072] The above and / or additional aspects and advantages of the present disclosure will become apparent and easier to understand from the following description of the embodiments taken in conjunction with the drawings. [Brief explanation of the drawings]

[0073] [Figure 1] 1 is a flowchart of a method for manufacturing an equivalent negative index planar lens according to one embodiment of the present disclosure. [Figure 2] 10 is a flowchart of a method for manufacturing an equivalent negative refractive index planar lens according to another embodiment of the present disclosure. [Figure 3] FIG. 2 is a schematic diagram of a transparent substrate layer according to one embodiment of the present disclosure. [Figure 4] 1 is a schematic diagram of a planar optical waveguide according to an embodiment of the present disclosure; [Figure 5] FIG. 2 is a schematic diagram of a multilayer planar optical waveguide after bonding according to one embodiment of the present disclosure. [Figure 6] 1 is a schematic diagram of a bonding process according to one embodiment of the present disclosure. [Figure 7] FIG. 10 is a schematic diagram of a multilayer planar optical waveguide before bonding according to another embodiment of the present disclosure. [Figure 8] FIG. 10 is a schematic diagram of a multilayer planar optical waveguide after bonding according to another embodiment of the present disclosure. [Figure 9] FIG. 1 is a schematic diagram of an equivalent negative refractive index flat lens according to an embodiment of the present disclosure. [Figure 10] 10 is a front structural schematic diagram of FIG. 9 of the present disclosure along the thickness direction. [Figure 11] FIG. 1 is an exploded view of an equivalent negative index planar lens according to one embodiment of the present disclosure. [Figure 12] 2A and 2B are schematic diagrams illustrating imaging of a first optical waveguide array and a second optical waveguide array according to the present disclosure. [Figure 13] 13A and 13B are schematic diagrams of an exploded first optical waveguide array of FIG. 12 of the present disclosure, in which (1) is a diagram illustrating the imaging principle in which light rays are reflected and collected inside the first optical waveguide array, and (2) is a diagram illustrating the light collection principle of the imaging light rays of the first optical waveguide array. [Figure 14] FIG. 2 is a diagram illustrating the imaging optical path principle of an equivalent negative refractive index flat lens according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0074] Hereinafter, the embodiments of the present disclosure shown in the drawings will be described in detail, and in all the drawings, the same or similar reference numerals indicate the same or similar elements or elements having the same or similar functions. The embodiments described through the following reference drawings are illustrative and are intended to explain the present disclosure, and should not be understood as limitations on the present disclosure.

[0075] In the present disclosure, terms indicating directions and positional relationships, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," are based on the directions or positional relationships shown in the drawings and are intended merely to facilitate and simplify the description of the present disclosure, and do not indicate or imply that the referred devices or elements must have a particular orientation, configuration, or operation in a particular direction, and cannot be considered to limit the present disclosure.

[0076] It should be noted that the terms "first" and "second" are for descriptive purposes only and cannot be considered to indicate or imply relative importance or the number of technical features. Thus, a feature qualified as "first" or "second" can expressly or imply the inclusion of one or more of the feature, and in the description of this disclosure, unless otherwise expressly and specifically limited, the concept of "plurality" is at least two, e.g., two or three.

[0077] In this disclosure, unless otherwise clearly defined and limited, terms such as "attached," "coupled," "connected," and "fixed" should be understood in a broad sense, and may mean, for example, fixedly connected, detachably connected, or integrated, mechanically connected, directly connected, indirectly connected via an intermediate medium, internal communication between two elements, or an interactive relationship between two elements. Those skilled in the art will be able to understand the specific concepts of the above technical terms in this disclosure depending on the specific circumstances, unless otherwise clearly limited.

[0078] In this disclosure, unless otherwise specified or limited, a first feature being "above" or "below" a second feature may refer to direct contact between the first and second features or indirect contact between the first and second features via an intermediate medium. Furthermore, a first feature being "above," "above," and "on the upper surface" of a second feature may refer to the first feature being directly above or diagonally above the second feature, or may simply indicate that the first feature has a higher horizontal height than the second feature. A first feature being "below," "below," and "on the lower surface" of a second feature may refer to the first feature being directly below or diagonally below the second feature, or may simply indicate that the first feature has a lower horizontal height than the second feature.

[0079] In a first aspect of the present disclosure, the present disclosure provides a method for manufacturing an equivalent negative refractive index flat lens 1. According to an embodiment of the present disclosure, referring to FIG. 1, the method includes the following steps:

[0080] S100: Forming reflective layers on both opposing sides of a transparent substrate layer In this step, reflective layers 20 are formed on opposite sides of the transparent substrate layer 10. A schematic diagram of the transparent substrate layer 10 is shown in FIG. 3. Specifically, the transparent substrate layer 10 is removed and cleaned using a cleaning agent to remove dust and organic matter from its surface. The cleaning agent can be deionized water, anhydrous ethanol, acetone, diethyl ether, or other organic solvents. The cleaning agent can then be dried using a thermal drying method or an air knife. The reflective layers 20 are then plated on both the top and bottom surfaces of the dried transparent substrate layer 10. The plating method for the reflective layers 20 is not particularly limited and may be, for example, vacuum thermal evaporation, ion beam evaporation, magnetron sputtering, vacuum reactive evaporation, or pulsed laser deposition, with magnetron sputtering being preferred. Furthermore, the length of the transparent substrate layer 10 is 10 mm to 10,000 mm, the width is 10 mm to 10,000 mm, and the thickness is 0.2 mm to 4 mm. The material of the transparent substrate layer 10 includes at least one of transparent glass and quartz. The thickness of the reflective layer 20 is 50 nm to 10 μm, and preferably 80 nm to 500 nm. The material of the reflective layer 20 includes at least one of a metal reflective film and a dielectric reflective film. The metal reflective film includes at least one of aluminum, silver, gold, and copper. The dielectric reflective film is a non-metal oxide film, preferably a multilayer dielectric film. The reflectance spectral range of the dielectric reflective film may be broadband or narrowband. The wavelength of the reflective layer 20 may cover all or part of the ultraviolet, visible, and infrared ranges, and may be used for imaging all or part of the ultraviolet, visible, and infrared ranges. The length of the transparent substrate layer 10 may be any value between 10 mm and 10,000 mm, such as 10 mm, 20 mm, 100 mm, or 10,000 mm; the width may be any value between 10 mm and 10,000 mm, such as 10 mm, 20 mm, 100 mm, or 10,000 mm; the thickness may be any value between 0.2 mm and 4 mm, such as 0.2 mm, 1 mm, 3 mm, or 4 mm; and the thickness of the reflective layer 20 may be any value between 50 nm and 10 μm, such as 50 nm, 1 μm, or 10 μm.

[0081] S200: A protective layer is formed on each reflective layer. In this step, a protective layer 30 is formed on each reflective layer 20. Specifically, a reflective layer 20 is formed on both the top and bottom of the transparent substrate layer 10, and then the protective layer 30 is plated on each of the two reflective layers 20. The plating method for the protective layer 30 is the same as the plating method for the reflective layer 20 described above, and will not be described again here. The thickness of the protective layer 30 is 10 nm to 1 μm, and preferably 50 nm to 200 nm. The material of the protective layer 30 includes at least one of silicon monoxide, magnesium fluoride, silicon dioxide, and aluminum trioxide, and the thickness of the protective layer 30 may be any value within the range of 10 nm to 1 μm, such as 10 nm, 20 nm, or 1 μm.

[0082] S300: A first bonding metal layer is formed on one side of the protective layer, and a second bonding metal layer is formed on the other side. In this step, a first bonding metal layer 40 is formed on one of the protective layers 30, and a second bonding metal layer 50 is formed on the other, thereby obtaining a planar optical waveguide, a schematic diagram of which is shown in Figure 4. Specifically, two protective layers 30 are formed on the reflective layer 20, and one of the protective layers 30 is plated with the first bonding metal layer 40, and the other protective layer 30 is plated with the second bonding metal layer 50.

[0083] Furthermore, if the material of the first bonding metal layer 40 along its thickness direction is Ni / Au / In, Ni / Au, Cr / Au, Ni / Au / In, Ti / Au, Cr / Au / Ni / AuGe, Pd, Ti, Pt, Cr / Al / Cr / In, Ti / Cu, AuBe, or Cr / Sn, the material of the second bonding metal layer 50 along its thickness direction is correspondingly In / Au / Ni, In / Ni, In / Cr, In / Au / Pt / Ti, Au / Ti, GeAu / Ni / Au / Cr, Pd, Ti, Pt, In / Cr / Al / Cr, Cu / Ti, BeAu, or Sn / Cr. As can be seen, if the first bonding metal layer 40 is made of Ni / Au / In, the second bonding metal layer 50 is made of In / Au / Ni. The Ni metal adheres to the protective layer 30 and acts as a bond between the Au metal and the protective layer 30. The In metal is located in the outermost layer and is used for subsequent bonding. The Au metal is located in the middle layer and serves as a bonding and bonding aid, forming an AuIn alloy after bonding. Note that Ni / Au / In refers to a three-layer structure consisting of Ni, Au, and In, stacked from top to bottom. In / Au / Ni refers to a three-layer structure consisting of In, Au, and Ni, stacked from top to bottom. The other bonding metal layers are similar to those described above and will not be described again here. The first bonding metal layer 40 and the second bonding metal layer 50 are made of a combination of multiple metals, with the aim of ensuring the adhesive strength between the metal and the protective layer 30, the strength of the alloy adhesive after bonding, and simplifying the bonding process.

[0084] Furthermore, if the material of the first bonding metal layer 40 along its thickness direction is In / Au / Ni, In / Ni, In / Cr, In / Au / Pt / Ti, Au / Ti, GeAu / Ni / Au / Cr, Pd, Ti, Pt, In / Cr / Al / Cr, Cu / Ti, BeAu, or Sn / Cr, the material of the second bonding metal layer 50 along its thickness direction is Ni / Au / In, Ni / Au, Cr / Au, Ni / Au / In, Ti / Au, Cr / Au / Ni / AuGe, Pd, Ti, Pt, Cr / Al / Cr / In, Ti / Cu, AuBe, or Cr / Sn, respectively. Note that the understanding of the above arrangement is the same as that described above, and therefore will not be repeated here.

[0085] Furthermore, the thickness ratio of metallic Ni, metallic Au, and metallic In in Ni / Au / In is (10-100):(10-100):(10-50), the thickness ratio of metallic Ni and metallic Au in Ni / Au is (10-100):(50-1000), the thickness ratio of metallic Cr and metallic Au in Cr / Au is (10-100):(50-1000), the thickness ratio of metallic Ni, metallic Au, and metallic In in Ni / Au / In is (10-100):(10-100):(10-100), the thickness ratio of metallic Ti and metallic Au in Ti / Au is (10-100):(100-3000), and the thickness ratio of metallic Cr, metallic Au, metallic Ni, and metallic AuGe in Cr / Au / Ni / AuGe is (10-100):(1 the thickness ratio of metallic Cr to metallic Al to metallic Cr to metallic In in Cr / Al / Cr / In is (10-100):(10-100):(10-100):(10-100), the thickness of metallic AuBe in AuBe is 50nm to 3000nm, and the thickness ratio of metallic Cr to metallic Sn in Cr / Sn is (10-100):(100-3000). This is advantageous for bonding the first bonding metal layer 40 and the second bonding metal layer 50 together.

[0086] Furthermore, the thickness ratio of metal In to metal Au to metal Ni in In / Au / Ni is (10-50):(10-100):(10-100), the thickness ratio of metal In to metal Ni in In / Ni is (10-100):(10-100), the thickness ratio of metal In to metal Cr in In / Cr is (10-100):(10-100), the thickness ratio of metal In to metal Au to metal Pt to metal Ti in In / Au / Pt / Ti is (10-100):(10-100):(10-100):(10-100), and the thickness ratio of metal Au to metal Ti in Au / Ti is (100-3000):(10-100). This is advantageous for bonding the first bonding metal layer 40 and the second bonding metal layer 50.

[0087] Furthermore, the thickness ratio of metallic GeAu, metallic Ni, metallic Au and metallic Cr in GeAu / Ni / Au / Cr is (100-3000):(10-100):(10-100):(10-100), the thickness of metallic Pd in ​​Pd is 50nm-3000nm, the thickness of metallic Ti in Ti is 50nm-3000nm, the thickness of metallic Pt in Pt is 50nm-3000nm, and the thickness of metallic In / Cr / Al / Cr is 50nm-3000nm. The thickness ratio of metal In to metal Cr to metal Al to metal Cr is (10-100), (10-100):(10-100):(10-100), the thickness ratio of metal Cu to metal Ti in Cu / Ti is (100-3000)(10-100), the thickness of metal BeAu in BeAu is 50nm-3000nm, and the thickness ratio of metal Sn to metal Cr in Sn / Cr is (100-3000):(10-100). This advantageously bonds the first bonding metal layer 40 and the second bonding metal layer 50.

[0088] S400: At least two planar optical waveguides are stacked along a first direction, and a first bonding metal layer in one planar optical waveguide is abutted against a second bonding metal layer in an adjacent planar optical waveguide, and heating and biasing are performed to integrally form the abutted first bonding metal layer and the second bonding metal layer, followed by annealing. In this step, at least two planar optical waveguides are stacked in their thickness direction, and the first bonding metal layer 40 of one planar optical waveguide is brought into contact with the second bonding metal layer 50 of the adjacent planar optical waveguide. Heating and biasing are performed so that the mutually contacting first bonding metal layer 40 and second bonding metal layer 50 form an integrated bonding layer 501. Next, annealing is performed to obtain a multilayer planar optical waveguide, a schematic diagram of which is shown in Figure 5. Note that the "first direction" refers to the vertical direction in Figure 5, i.e., the thickness direction of the planar optical waveguide. Specifically, taking two planar optical waveguides as an example, after stacking them, the two stacked planar optical waveguides are placed in a vacuum of -90 kPa or more, and then a pressure plate 11 is applied to the top layer and a heating plate 12 is applied to the bottom layer, so that the first bonding metal layer 40 of one planar optical waveguide and the second bonding metal layer 50 of the other planar optical waveguide are bonded together, as shown in Figure 6. Taking three planar optical waveguides as an example, the first bonding metal layer 40 of the middle planar optical waveguide is bonded to the second bonding metal layer 50 of the second planar optical waveguide, and simultaneously the second bonding metal layer 50 of the middle planar optical waveguide is bonded to the first bonding metal layer 40 of the third planar optical waveguide. Specifically, the first bonding metal layer 40 of one planar optical waveguide is Ni / Au / In, and the second bonding metal layer 50 of the other planar optical waveguide is In / Au / Ni. When the first bonding metal layer 40 is brought into contact with the second bonding metal layer 50, the In layer of the first bonding metal layer 40 contacts the In layer of the second bonding metal layer 50. Then, heating and energizing are performed, so that the Au and In metals of the Ni / Au / In first bonding metal layer 40 and the Au and In metals of the second bonding metal layer 50 merge into one, i.e., form an AuIn alloy. This allows the metal atoms in the connecting layer between any adjacent planar optical waveguides to diffuse into each other and form a single metal. This avoids the internal stress distortion that occurs when the connecting layer is made of a resin adhesive during curing in conventional processes, reduces the thickness of the connecting layer, and improves imaging quality. At the same time, the high stability of metals improves aging performance when used as a connecting layer.Next, the at least two planar optical waveguides formed integrally are annealed. Annealing can remove internal stress in the alloy or metal formed after bonding the first bonding metal layer 40 and the second bonding metal layer 50, prevent bending or breaking after cutting the material, and improve bonding strength. Here, the annealing temperature is reduced slowly, at a rate of 0.5°C / min or less.

[0089] The number of layers in the laminate ranges from 2 to 10,000 and can be selected by those skilled in the art according to actual needs. The bonding process between the first bonding metal layer 40 and the second bonding metal layer 50 is preferably carried out in a high-vacuum environment, with a relative vacuum of -90 kPa or higher, to prevent oxidation of the metal surfaces. At the same time, the bonding process is preferably carried out in a dust-free environment, with a cleanliness level of 100 or higher, to prevent dust particles from affecting the bonding quality.

[0090] Furthermore, the applied pressure is 1 kgf to 50 kgf. Furthermore, the heating temperature for Ni / Au / In and In / Au / Ni is 150°C to 200°C, and the heating time is 1 hour to 20 hours, the heating temperature for Ni / Au and In / Ni is 130°C to 200°C, and the heating time is 0.2 hours to 5 hours, the heating temperature for Cr / Au and In / Cr is 130°C to 200°C, and the heating time is 0.2 hours to 5 hours, the heating temperature for Ni / Au / In and In / Au / Pt / Ti is 150°C to 200°C, and the heating time is 1 hour to 20 hours, the heating temperature for Ti / Au and Au / Ti is 250°C to 350°C, and the heating time is 1 hour to 12 hours, and the heating temperature for Cr / Au / Ni / AuGe and GeAu / Ni / Au / Cr is 150°C to 220°C, and the heating time is 1 hour to 2 hours. The heating temperature for Pd is 100°C to 160°C for 1 hour to 20 hours, the heating temperature for Ti is 200°C to 400°C for 1 hour to 20 hours, the heating temperature for Pt is 200°C to 400°C for 1 hour to 20 hours, the heating temperature for Cr / Al / Cr / In and In / Cr / Al / Cr is 150°C to 200°C for 1 hour to 20 hours, the heating temperature for Ti / Cu and Cu / Ti is 350°C to 500°C for 1 hour to 20 hours, the heating temperature for AuBe and AuBe is 150°C to 250°C for 1 hour to 20 hours, and the heating temperature for Cr / Sn and Sn / Cr is 90°C to 120°C for 1 hour to 20 hours. This results in better bonding between the first bonding metal layer 40 and the second bonding metal layer 50.

[0091] Furthermore, the annealing temperature for Ni / Au / In and In / Au / Ni is 230°C-300°C, and the annealing time is 0.2-5h; the annealing temperature for Ni / Au and In / Ni is 300°C-450°C, and the annealing time is 0.2-5h; the annealing temperature for Cr / Au and In / Cr is 300°C-450°C, and the annealing time is 0.2-5h; the annealing temperature for Ni / Au / In and In / Au / Pt / Ti is 230°C-300°C, and the annealing time is 0.2-5h; the annealing temperature for Ti / Au and Au / Ti is 400°C-500°C, and the annealing time is 0.2-10h; and the annealing temperature for Cr / Au / Ni / AuGe and GeAu / The annealing temperature for Ni / Au / Cr is 300°C to 450°C, and the annealing time is 0.5 to 10 hours. The annealing temperature for Pd is 200°C to 300°C, and the annealing time is 0.1 to 5 hours. The annealing temperature for Cr / Al / Cr / In and In / Cr / Al / Cr is 250°C to 350°C, and the annealing time is 0.1 to 5 hours. The annealing temperature for Ti / Cu and Cu / Ti is 550°C, and the annealing time is 0.3 to 5 hours. The annealing temperature for AuBe and BeAu is 280°C to 350°C, and the annealing time is 0.1 to 2 hours. The annealing temperature for Cr / Sn and Sn / Cr is 140°C to 200°C, and the annealing time is 0.5 to 5 hours. This eliminates stress strain within the material and prevents bending or fracture after cutting.

[0092] Furthermore, referring to FIG. 2, after at least two planar optical waveguides are stacked in a first direction, a first bonding sheet 110 is provided on the planar optical waveguides after the stacking, and a second bonding sheet 120 is provided on one side of the planar optical waveguides after the stacking, away from the first bonding sheet 110. The schematic diagram before bonding is shown in FIG. 7, and the schematic diagram after bonding is shown in FIG. 8. The first bonding sheet 110 includes a transparent substrate layer 10, a reflective layer 20, a protective layer 30, and a second bonding metal layer 50, and the reflective layer 20 is formed on both opposing sides of the transparent substrate layer 10. a protective layer 30 is formed on each reflective layer 20, a second bonding metal layer 50 is formed on the bottom surface of the protective layer 30 and abuts against the first bonding metal layer 40 of the planar optical waveguide, and the second bonding sheet 120 comprises a transparent substrate layer 10, a reflective layer 20, a protective layer 30 and a first bonding metal layer 40, the reflective layers 20 are formed on opposite sides of the transparent substrate layer 10, a protective layer 30 is formed on each reflective layer 20, and the first bonding metal layer 40 is formed on the protective layer 30 and abuts against the second bonding metal layer 50 of the planar optical waveguide. This makes full use of the first bonding metal layer 40 and the second bonding metal layer 50, one side of which is not bonded, in the planar optical waveguide, saving materials and simplifying the process.

[0093] S500: Taking two sets of multilayer planar optical waveguides, cutting one set of multilayer planar optical waveguides into a plurality of first stripe planar optical waveguides, and cutting the other set into a plurality of second stripe planar optical waveguides, the extension direction of the first stripe planar optical waveguide and the extension direction of the second stripe planar optical waveguide being perpendicular to each other. In this step, two sets of multilayer planar optical waveguides are taken, and one set of multilayer planar optical waveguides is cut into a plurality of first striped planar optical waveguides 1021 to obtain a first optical waveguide array 102, and the other set is cut into a plurality of second striped planar optical waveguides 1031 to obtain a second optical waveguide array 103, in which the extension direction of the first striped planar optical waveguide 1021 and the extension direction of the second striped planar optical waveguide 1031 are perpendicular to each other. See Figures 10 and 11 for schematic diagrams. Specifically, two sets of multilayer planar optical waveguides are taken, and the surfaces of each set of multilayer planar optical waveguides are polished to make the surfaces of the two sets of multilayer planar optical waveguides parallel to each other. Then, the two sets of multilayer planar optical waveguides are cut, and one set of multilayer planar optical waveguides is cut into a plurality of first striped planar optical waveguides 1021 to obtain a first optical waveguide array 102, and the other set of multilayer planar optical waveguides is cut into a plurality of second striped planar optical waveguides 1031 to obtain a second optical waveguide array 103, and the extension direction of the first striped planar optical waveguide 1021 and the extension direction of the second striped planar optical waveguide 1031 are kept perpendicular to each other. The extension directions of the first striped planar optical waveguide 1021 and the second striped planar optical waveguide 1031 form an angle θ with the up-down direction of the multilayer planar optical waveguide, which is 30°≦θ≦60°, and preferably θ=45°. The external shapes of the first optical waveguide array 102 and the second optical waveguide array 103 obtained at the same time are the same except that the extension directions of the cut first striped planar optical waveguide 1021 and the second striped planar optical waveguide 1031 are perpendicular to each other. For example, the extension direction of the first striped planar optical waveguide 1021 is the X direction, the extension direction of the second striped planar optical waveguide 1031 is the Y direction, the Z direction is the thickness direction of the multilayer planar optical waveguide, and the X direction, Y direction, and Z direction are perpendicular to each other.

[0094] S600: The first optical waveguide array and the second optical waveguide array are stacked along a first direction, and the extension directions of the first striped planar optical waveguide and the second striped planar optical waveguide after stacking are perpendicular to each other. Then, protective window sheets are added on both sides.

[0095] In this step, the first optical waveguide array 102 and the second optical waveguide array 103 are overlapped along a first direction, such that the extension directions of the first striped planar optical waveguide 1021 and the second striped planar optical waveguide 1031 are perpendicular to each other. Next, a first protective window sheet 101 and a second protective window sheet 104 are added on both sides, respectively, to obtain an equivalent negative refractive index planar lens 1 (see FIG. 9). Note that the first direction is the Z direction in FIG. 10, i.e., the thickness direction of the first optical waveguide array 102 and the second optical waveguide array 103. Here, the first optical waveguide array 102 and the second optical waveguide array 103 are both planar with one row and multiple columns, and the first optical waveguide array 102 is perpendicular to the second optical waveguide array 103, thereby achieving aberration-free point-to-point imaging on the object side and the image side, as shown in FIG. 12. The manufactured equivalent negative refractive index flat lens 1 can directly image a two-dimensional or three-dimensional light source in air to realize a true holographic image, achieving a large field of view, large aperture, high resolution, no distortion, and no dispersion, while also achieving naked-eye three-dimensional stereoscopic display characteristics.

[0096] As described above, this method uses the first and second bonding metal layers 40 and 50 as connecting layers, avoiding the internal stress strain that occurs during curing when using a resin adhesive as a connecting layer in conventional processes, which adversely affects imaging quality. This reduces the thickness of the connecting layer, further improving imaging quality, and at the same time, the metal has high stability and improved aging performance.

[0097] In a second aspect of the present disclosure, the present disclosure provides an equivalent negative refractive index planar lens 1. According to an embodiment of the present disclosure, the equivalent negative refractive index planar lens 1 is manufactured using the above method, thereby improving the imaging quality of the equivalent negative refractive index planar lens 1. Note that the features and advantages described in the above method for manufacturing the equivalent negative refractive index planar lens 1 also apply to the equivalent negative refractive index planar lens 1, and will not be repeated here.

[0098] The imaging principle of the equivalent negative refractive index flat lens 1 according to the embodiment of the present disclosure is as follows: By separating the first optical waveguide array 102 and the second optical waveguide array 103 and taking the first optical waveguide array 102 as an example, as shown in FIG. 13 , a single-point ray of light on the object side of the single-layer first optical waveguide array 102 passes through the one-sided equivalent negative refractive index flat lens 1, is split and mirror-modulated by the optical waveguides in each row, and is then refocused into a straight line parallel to the long side of the optical waveguide, forming a one-dimensional point-to-line imaging effect. As shown in Figure 14, in order to achieve the intersection of both directions at a single point, the first optical waveguide array 102 and the second optical waveguide array 103 must be used together, so that the distribution directions of the first striped planar optical waveguide 1021 in the first optical waveguide array 102 and the second striped planar optical waveguide 1031 in the second optical waveguide array 103 are perpendicular to each other, and the target object image can be modulated point-to-point. Therefore, light rays in any direction can pass through these two orthogonal optical waveguide arrays and reconverge at the symmetrical position of the optical waveguide array to form a floating real image. The distance of the floating real image to the original image is the same as that of the original image, so it is an equidistant image. Furthermore, the position of the floating real image is in the air, so no medium carrier is required and the real image can be directly displayed in the air.

[0099] In the description herein, a statement referring to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples" means that a particular feature, structure, material, or characteristic described with reference to that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, general references to such terms do not necessarily refer to the same embodiment or example. In addition, a particular feature, structure, material, or characteristic described may be incorporated in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art can combine and combine the various embodiments or examples described herein and the features of the various embodiments or examples without mutual contradiction.

[0100] Although the embodiments of the present disclosure have been presented and described, the above embodiments are illustrative and cannot be understood as limiting the present disclosure, and it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to the above embodiments within the scope of the present disclosure.

[0101] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to and benefits from patent application number 202310138976.4, filed with the State Intellectual Property Office of China on February 10, 2023, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0102] 1. Equivalent negative refractive index flat lens; 101, a first protective window sheet; 102, a first optical waveguide array; 1021, a first stripe planar optical waveguide; 103, a second optical waveguide array; 1031, a second stripe planar optical waveguide; 104, second protective window sheet; 10, transparent base material layer, 20, reflective layer; 30, protective layer, 40, first bonding metal layer; 50, second bonding metal layer, 501, bonding layer, 110, first bonding sheet; 120, second bonding sheet; 11, pressure plate, 12, heating plate.

Claims

1. A method for manufacturing an equivalent negative refractive index planar lens, comprising the steps of: Step (1) of forming a reflective layer on both opposing sides of a transparent substrate layer; (2) forming a protective layer on each of the reflective layers; (3) forming a first bonding metal layer on one side of the protective layer and a second bonding metal layer on the other side of the protective layer to form a planar optical waveguide; Step (4) of stacking at least two of the planar optical waveguides along a first direction, and the first bonding metal layer of one planar optical waveguide is brought into contact with the second bonding metal layer of the adjacent planar optical waveguide, and heating and biasing are performed to integrally form the first bonding metal layer and the second bonding metal layer that are brought into contact with each other, and then annealing is performed to obtain a multi-layer planar optical waveguide; (5) taking two sets of the multilayer planar optical waveguides, cutting one of the multilayer planar optical waveguides into a plurality of first striped planar optical waveguides to obtain a first optical waveguide array, and cutting the other into a plurality of second striped planar optical waveguides to obtain a second optical waveguide array, wherein the extension direction of the first striped planar optical waveguide and the extension direction of the second striped planar optical waveguide are perpendicular to each other; a step (6) of overlapping the first optical waveguide array and the second optical waveguide array along the first direction, and after the overlapping, the extension directions of the first striped plate optical waveguide and the second striped plate optical waveguide are perpendicular to each other; and then adding protective window sheets on both sides to obtain an equivalent negative refractive index plate lens.

2. 2. The method according to claim 1, wherein in step (1), the transparent substrate layer has a length of 10 mm to 10,000 mm, a width of 10 mm to 10,000 mm, and a thickness of 0.2 mm to 4 mm.

3. 3. The method according to claim 1, wherein the material of the transparent substrate layer includes at least one of transparent glass and quartz.

4. The method according to any one of claims 1 to 3, wherein the thickness of the reflective layer is from 50 nm to 10 µm.

5. 5. The method according to claim 1, wherein the material of the reflective layer includes at least one of a metal reflective film and a dielectric reflective film.

6. 6. The method of claim 5, wherein the metallic reflective film comprises at least one of aluminum, silver, gold, and copper, and the dielectric reflective film is a non-metal oxide film.

7. The method according to any one of claims 1 to 6, wherein in step (2), the thickness of the protective layer is 10 nm to 1 µm.

8. The method according to any one of claims 1 to 7, wherein the material of the protective layer includes at least one of silicon monoxide, magnesium fluoride, silicon dioxide, and aluminum trioxide.

9. In step (3), the material of the first bonding metal layer along its thickness direction is Ni / Au / In, Ni / Au, Cr / Au, Ni / Au / In, Ti / Au, Cr / Au / Ni / AuGe, Pd, Ti, Pt, Cr / Al / Cr / In, Ti / Cu, AuBe or Cr / Sn, and the material of the second bonding metal layer along its thickness direction is In / Au / Ni, In / Ni, In / Cr, In / Au / Pt / Ti, Au / Ti, GeAu / Ni / Au / Cr, Pd, Ti, Pt, In / Cr / Al / Cr, Cu / Ti, BeAu or Sn / Cr, respectively. The method according to any one of claims 1 to 8.

10. In step (3), the material of the first bonding metal layer along its thickness direction is In / Au / Ni, In / Ni, In / Cr, In / Au / Pt / Ti, Au / Ti, GeAu / Ni / Au / Cr, Pd, Ti, Pt, In / Cr / Al / Cr, Cu / Ti, BeAu or Sn / Cr, and the material of the second bonding metal layer along its thickness direction is Ni / Au / In, Ni / Au, Cr / Au, Ni / Au / In, Ti / Au, Cr / Au / Ni / AuGe, Pd, Ti, Pt, Cr / Al / Cr / In, Ti / Cu, AuBe or Cr / Sn, respectively. The method according to any one of claims 1 to 8.

11. 11. The method according to claim 9 or 10, wherein in step (3), the thickness ratio of the metallic Ni, metallic Au, and metallic In in the Ni / Au / In is (10-100):(10-100):(10-50).

12. The method according to any one of claims 9 to 11, wherein the thickness ratio of the metallic Ni to the metallic Au in the Ni / Au film is (10 to 100):(50 to 1000).

13. The method according to any one of claims 9 to 12, wherein the thickness ratio of the metallic Cr to the metallic Au in the Cr / Au layer is (10 to 100):(50 to 1000).

14. The method according to any one of claims 9 to 13, wherein the thickness ratio of the metal Ni, metal Au, and metal In in the Ni / Au / In is (10-100):(10-100):(10-100).

15. The method according to any one of claims 9 to 14, wherein the thickness ratio of the metallic Ti to the metallic Au in the Ti / Au film is (10 to 100):(100 to 3000).

16. The method according to any one of claims 9 to 15, wherein the thickness ratio of the metal Cr, the metal Au, the metal Ni, and the metal AuGe in the Cr / Au / Ni / AuGe is (10 to 100):(10 to 100):(10 to 100):(100 to 3000).

17. The method according to any one of claims 9 to 16, wherein the thickness of the metallic Pd in ​​the Pd is 50 nm to 3000 nm.

18. The method according to any one of claims 9 to 17, wherein the thickness of the metallic Ti in the Ti is 50 nm to 3000 nm.

19. The method according to any one of claims 9 to 18, wherein the thickness of the metallic Pt in the Pt is 50 nm to 3000 nm.

20. The method according to any one of claims 9 to 19, wherein the thickness ratio of the metal Cr, the metal Al, the metal Cr, and the metal In in the Cr / Al / Cr / In is (10-100):(10-100):(10-100):(10-100).

21. The method according to any one of claims 9 to 20, wherein the thickness ratio of the metallic Ti to the metallic Cu in the Ti / Cu is (10 to 100):(100 to 3000).

22. The method according to any one of claims 9 to 21, wherein the thickness of the metallic AuBe in the AuBe is 50 nm to 3000 nm.

23. The method according to any one of claims 9 to 22, wherein the thickness ratio of the metallic Cr to the metallic Sn in the Cr / Sn is (10 to 100):(100 to 3000).

24. 24. The method according to any one of claims 9 to 23, wherein in step (3), the thickness ratio of the metal In, the metal Au, and the metal Ni in the In / Au / Ni is (10-50):(10-100):(10-100).

25. The method according to any one of claims 9 to 24, wherein the thickness ratio of metallic In to metallic Ni in the In / Ni film is (10 to 100):(10 to 100).

26. The method according to any one of claims 9 to 25, wherein the thickness ratio of metallic In to metallic Cr in the In / Cr film is (10 to 100):(10 to 100).

27. The method according to any one of claims 9 to 26, wherein the thickness ratio of metal In, metal Au, metal Pt, and metal Ti in the In / Au / Pt / Ti is (10 to 100):(10 to 100):(10 to 100):(10 to 100).

28. The method according to any one of claims 9 to 27, wherein the thickness ratio of metallic Au to metallic Ti in the Au / Ti is (100-3000):(10-100).

29. The method according to any one of claims 9 to 28, wherein the thickness ratio of the metal GeAu, metal Ni, metal Au, and metal Cr in the GeAu / Ni / Au / Cr is (100 to 3000):(10 to 100):(10 to 100):(10 to 100).

30. The method according to any one of claims 9 to 29, wherein the thickness of the metallic Pd in ​​the Pd is 50 nm to 3000 nm.

31. The method according to any one of claims 9 to 30, wherein the thickness of the metallic Ti in the Ti is 50 nm to 3000 nm.

32. The method according to any one of claims 9 to 31, wherein the thickness of the metallic Pt in the Pt is 50 nm to 3000 nm.

33. The method according to any one of claims 9 to 32, wherein the thickness ratio of the metal In, the metal Cr, the metal Al, and the metal Cr in the In / Cr / Al / Cr is (10 to 100), or (10 to 100):(10 to 100):(10 to 100).

34. The method according to any one of claims 9 to 33, wherein the thickness ratio of metallic Cu to metallic Ti in the Cu / Ti is (100 to 3000):(10 to 100).

35. The method according to any one of claims 9 to 34, wherein the thickness of the metal BeAu in the BeAu is 50 nm to 3000 nm.

36. The method according to any one of claims 9 to 35, wherein the thickness ratio of metallic Sn to metallic Cr in the Sn / Cr is (100-3000):(10-100).

37. The method according to any one of claims 1 to 36, wherein in step (4), the biasing pressure is 1 kgf to 50 kgf.

38. The method according to any one of claims 9 to 37, wherein the heating temperature of the Ni / Au / In and the In / Au / Ni is 150 ° C to 200 ° C, and the heating time is 1 h to 20 h.

39. The method according to any one of claims 9 to 38, wherein the heating temperature of the Ni / Au and the In / Ni is 130°C to 200°C, and the heating time is 0.2h to 5h.

40. The method according to any one of claims 9 to 39, wherein the heating temperature of the Cr / Au and the In / Cr is 130°C to 200°C, and the heating time is 0.2h to 5h.

41. The method according to any one of claims 9 to 40, wherein the heating temperature of the Ni / Au / In and the In / Au / Pt / Ti is 150°C to 200°C, and the heating time is 1 hour to 20 hours.

42. The method according to any one of claims 9 to 41, wherein the heating temperature of the Ti / Au and the Au / Ti is 250°C to 350°C, and the heating time is 1 hour to 12 hours.

43. The method according to any one of claims 9 to 42, wherein the heating temperature of the Cr / Au / Ni / AuGe and the GeAu / Ni / Au / Cr is 150 ° C to 220 ° C, and the heating time is 1 h to 20 h.

44. The method according to any one of claims 9 to 43, wherein the heating temperature of the Pd is 100°C to 160°C, and the heating time is 1 hour to 20 hours.

45. The method according to any one of claims 9 to 44, wherein the heating temperature of the Ti is 200°C to 400°C, and the heating time is 1 hour to 20 hours.

46. The method according to any one of claims 9 to 45, wherein the heating temperature of the Pt is 200°C to 400°C, and the heating time is 1 hour to 20 hours.

47. The method according to any one of claims 9 to 46, wherein the heating temperature of the Cr / Al / Cr / In and the In / Cr / Al / Cr is 150 ° C to 200 ° C, and the heating time is 1 h to 20 h.

48. The method according to any one of claims 9 to 47, wherein the heating temperature of the Ti / Cu and the Cu / Ti is 350°C to 500°C, and the heating time is 1h to 20h.

49. The method according to any one of claims 9 to 48, wherein the heating temperature of the AuBe and the AuBe is 150°C to 250°C, and the heating time is 1 hour to 20 hours.

50. The method according to any one of claims 9 to 49, wherein the heating temperature of the Cr / Sn and the Sn / Cr is 90 ° C to 120 ° C, and the heating time is 1 h to 20 h.

51. The method according to any one of claims 9 to 50, wherein in step (4), the annealing temperature of the Ni / Au / In and the In / Au / Ni is 230°C to 300°C, and the annealing time is 0.2 to 5h.

52. The method according to any one of claims 9 to 51, wherein the annealing temperature of the Ni / Au and the In / Ni is 300°C to 450°C, and the annealing time is 0.2h to 5h.

53. The method according to any one of claims 9 to 52, wherein the annealing temperature of the Cr / Au and the In / Cr is 300°C to 450°C, and the annealing time is 0.2h to 5h.

54. The method according to any one of claims 9 to 53, wherein the annealing temperature of the Ni / Au / In and the In / Au / Pt / Ti is 230°C to 300°C, and the annealing time is 0.2 to 5h.

55. The method according to any one of claims 9 to 54, wherein the annealing temperature of the Ti / Au and the Au / Ti is 400°C to 500°C, and the annealing time is 0.2h to 10h.

56. The method according to any one of claims 9 to 55, wherein the annealing temperature of the Cr / Au / Ni / AuGe and the GeAu / Ni / Au / Cr is 300°C to 450°C, and the annealing time is 0.5 to 10h.

57. The method according to any one of claims 9 to 56, wherein the annealing temperature of the Pd is 200°C to 300°C, and the annealing time is 0.1h to 5h.

58. The method according to any one of claims 9 to 57, wherein the annealing temperature of the Cr / Al / Cr / In and the In / Cr / Al / Cr is 250°C to 350°C, and the time is 0.1h to 5h.

59. The method according to any one of claims 9 to 58, wherein the annealing temperature of the Ti / Cu and the Cu / Ti is 550°C and the time is 0.3 to 5h.

60. The method according to any one of claims 9 to 59, wherein the annealing temperature of the AuBe and the BeAu is 280°C to 350°C, and the annealing time is 0.1h to 2h.

61. The method according to any one of claims 9 to 60, wherein the annealing temperature of the Cr / Sn and the Sn / Cr is 140°C to 200°C, and the time is 0.5h to 5h.

62. The method according to any one of claims 1 to 61, further comprising the steps of: in step (4), after stacking at least two of the planar optical waveguides along the first direction, providing a first bonding sheet on the stacked planar optical waveguides; and providing a second bonding sheet on one side of the stacked planar optical waveguides away from the first bonding sheet.

63. The method of claim 62, wherein the first bonding sheet comprises a transparent substrate layer, reflective layers formed on opposite sides of the transparent substrate layer, protective layers formed on each of the reflective layers, and a second bonding metal layer formed on the bottom surface of the protective layer and abutting the first bonding metal layer of the flat optical waveguide.

64. The method according to claim 62 or 63, wherein the second bonding sheet comprises a transparent substrate layer, reflective layers formed on opposite sides of the transparent substrate layer, protective layers formed on each of the reflective layers, and a first bonding metal layer formed on the protective layers and abutting the second bonding metal layer of the flat optical waveguide.

65. An equivalent negative refractive index flat lens manufactured using the method according to any one of claims 1 to 64.

Images