Superlens and camera

Abstract

This disclosure discloses a superlens and a camera. The superlens includes a substrate and a plurality of nanopillars. The substrate has a circular cross-section, and the nanopillars are disposed on the substrate. In the radial direction of the substrate, the height of the nanopillars gradually decreases from the center to the edge of the substrate. By using nanopillars with gradually decreasing heights, the superlens of this disclosure can be constructed by employing a structure that changes height. This superlens can extend the covered phase retardation by several times, achieving an achromatic superlens with a larger aperture and a larger aperture (NA).

Description

Technical Field

[0001] This disclosure relates to the technical field of achromatic lenses, and more specifically, to a superlens and a camera. Background Technology

[0002] In the field of lens imaging, achromatic technology has been developed for a long time. Currently, the industry-standard achromatic technology uses a combination of multiple lenses, each with different materials and shapes, to compensate for chromatic aberrations caused by different wavelengths of incident light.

[0003] In recent years, metasurface lens technology has been developed, which uses subwavelength structure to modulate the incident light wavefront. Recently, there has been some work on using metasurface lenses to eliminate chromatic aberration. This technology is still in the early stages of development.

[0004] However, metasurface lenses in related technologies can only cover a phase retardation range of about 5 fs when achromatic, ultimately achieving an achromatic metalens with NA = 0.106. Due to the small phase retardation range, it is difficult to increase the NA value and aperture of the final lens. Summary of the Invention

[0005] This disclosure aims to at least partially address one of the technical problems in the related art.

[0006] To this end, one aspect of the present disclosure proposes a superlens in which nanopillars of gradually decreasing height are arranged, and the superlens is constructed by adopting a structure that changes the height. This superlens can extend the covered phase retardation by several times, thereby realizing an achromatic superlens with a larger aperture and a larger NA.

[0007] Another embodiment of this disclosure provides a camera.

[0008] A superlens according to a first aspect of this disclosure includes: a substrate having a circular cross-section; and a plurality of nanopillars disposed on the substrate, wherein the height of the nanopillars gradually decreases from the center of the substrate to its edge in the radial direction of the substrate.

[0009] According to embodiments of the present disclosure, a superlens is constructed by setting nanopillars with gradually decreasing height and using a structure that changes the height. This superlens can extend the covered phase retardation by several times, thus realizing an achromatic superlens with a larger aperture and a larger NA.

[0010] In some embodiments, in the circumferential direction of the substrate, the plurality of nanopillars disposed at the same radius of the substrate have the same height.

[0011] In some embodiments, the cross-sectional areas of some or all of the plurality of nanopillars are different from each other in the radial direction of the substrate, from the center of the substrate to its edge.

[0012] In some embodiments, in the circumferential direction of the substrate, at least a portion of the nanopillars disposed at the same radius of the substrate have the same cross-sectional area.

[0013] In some embodiments, the height of the nanopillar and the cross-sectional area of ​​the nanopillar satisfy the following:

[0014]

[0015] Where ω is the frequency, c is the speed of light, h is the total altitude (including air), and n eff The cross-sectional area and height of the nanopillars are related to the effective refractive index.

[0016] In some embodiments, the nanopillars are made of materials including but not limited to GaN, TiO2, Si, or Si3N4.

[0017] In some embodiments, the height of the plurality of nanopillars is between 1 and 2000 nm.

[0018] In some embodiments, in the circumferential direction of the substrate, the multiple nanopillars located at the same radius of the substrate have the same turning angle.

[0019] In some embodiments, at least some of the nanopillars have different orientation angles in the radial direction of the matrix.

[0020] A camera according to a second aspect embodiment of the present disclosure includes: a housing; a lens assembly disposed within the housing; and a superlens, wherein the superlens is any superlens described in any embodiment of the present disclosure, the superlens being disposed within the housing, and the superlens cooperating with the lens assembly. Attached Figure Description

[0021] Figure 1 This is a perspective view of a superlens according to an embodiment of the present disclosure.

[0022] Figure 2 This is a top view of a superlens according to an embodiment of the present disclosure.

[0023] Figure 3 This is a side view of a superlens according to an embodiment of the present disclosure.

[0024] Figure 4 This is a schematic diagram of light propagating in a nanopillar within a superlens according to an embodiment of the present disclosure.

[0025] Figure 5 This is a distribution diagram of the phase and frequency of incident light when a superlens according to an embodiment of the present disclosure is applied to a mobile phone.

[0026] Figure 6 This is a distribution diagram of the diffraction efficiency and phase delay of incident light when a superlens according to an embodiment of the present disclosure is applied to a mobile phone.

[0027] Figure 7 This is a distribution diagram of the focal point of incident light in the 450-650nm range when the superlens according to an embodiment of this disclosure is applied to a mobile phone.

[0028] Figure label:

[0029] Superlens 100, substrate 1, nanopillar 2. Detailed Implementation

[0030] Embodiments of this disclosure are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this disclosure, and should not be construed as limiting it.

[0031] like Figures 1-3 As shown, the superlens 100 according to an embodiment of the present disclosure includes a substrate 1 and a plurality of nanopillars 2.

[0032] The cross-section of the substrate 1 is circular, and multiple nanopillars 2 are disposed on the substrate 1. In the radial direction of the substrate 1, the height of the nanopillars 2 gradually decreases from the center of the substrate 1 to its edge.

[0033] Specifically, such as Figures 1-3 As shown, the substrate 1 is generally a circular plate structure, with multiple nanopillars 2 disposed on the substrate 1, and the axis of the nanopillars 2 is perpendicular to the upper surface of the substrate 1.

[0034] Optionally, from the center of the substrate 1 to its edge, the greater the distance between the nanopillar 2 and the center of the substrate 1, the lower the height of the nanopillar 2. That is, the closer the nanopillar 2 is to the center of the substrate 1, the higher its height, and the farther the nanopillar 2 is from the center of the substrate 1, the lower its height. Alternatively, the height of the nanopillar 2 within a certain distance from the center of the substrate 1 (e.g., within 5 mm) can be higher than the height of the nanopillar 2 within another certain distance from the center of the substrate 1 (e.g., within 5 mm to 10 mm), and the height of the nanopillar 2 within another certain distance from the center of the substrate 1 (e.g., within 5 mm to 10 mm) can be higher than the height of the nanopillar 2 within yet another certain distance from the center of the substrate 1 (e.g., within 10 mm to 15 mm (or 10 mm to its edge)).

[0035] According to the embodiments of the present disclosure, the superlens 100 is constructed by setting nanopillars 2 with gradually decreasing height and using a structure that changes the height. The superlens 100 can extend the covered phase delay by several times, thus realizing a superlens 100 with a larger aperture and a larger NA.

[0036] In some embodiments, such as Figures 1-3 As shown, multiple nanopillars 2 with the same height are provided at the same radius of the substrate 1 in the circumferential direction.

[0037] It is understandable that the substrate 1 is generally a circular plate structure with a circular cross-section. With the center of the substrate 1 as the center, multiple nanopillars 2 are arranged on the circumference at the same radius from the center. The distance between the multiple nanopillars 2 and the center is consistent, and the height of the multiple nanopillars 2 is consistent.

[0038] In some embodiments, such as Figures 1-3 As shown, in the radial direction of the substrate 1, from the center of the substrate 1 to its edge, the cross-sectional areas of some or all of the multiple nanopillars 2 are different.

[0039] In some embodiments, such as Figures 1-3 As shown, in the circumferential direction of the substrate 1, at least some of the nanopillars 2 provided at the same radius of the substrate 1 have the same cross-sectional area.

[0040] It is understandable that the substrate 1 is generally a circular plate structure with a circular cross-section. With the center of the substrate 1 as the center, multiple nanopillars 2 are arranged on the circumference at the same radius from the center. The distance between the multiple nanopillars 2 and the center is consistent, and at least some of the nanopillars 2 have the same cross-sectional area.

[0041] In some embodiments, the material of the nanopillar 2 includes, but is not limited to, GaN, TiO2, Si, or Si3N4.

[0042] In some embodiments, the height of the plurality of nanopillars 2 is between 1 and 2000 nm.

[0043] Optionally, the height of the multiple nanopillars 2 may include, but is not limited to, 2000 nm, 1600 nm, or 800 nm.

[0044] Optionally, the focal length of the nanopillar 2 is 19 μm.

[0045] In some embodiments, multiple nanopillars located at the same radius of the substrate have the same orientation angle in the circumferential direction of the substrate.

[0046] Understandably, in the field of achromatic lens technology, the phase at the surface of an achromatic lens can be divided into two terms: the first term is the phase at the intermediate wavelength, and the second term is the phase difference required for incident light of different frequencies.

[0047] The first item involves only a single wavelength and can be achieved by the geometric phase of the superlens unit, that is, by changing the orientation angle of the nanopillar 2, the phase requirement can be met.

[0048] Meanwhile, in order to further eliminate color difference, the second requirement must also be met. This disclosure achieves this by changing the size of the nanopillar 2 to generate different propagation phases for incident light at different frequencies.

[0049] In some embodiments, at least some of the nanopillars have different orientation angles in the radial direction of the matrix.

[0050] According to a second aspect of this disclosure, the camera includes a housing, a lens assembly, and a superlens 100.

[0051] The lens assembly is disposed inside the housing. The superlens 100 is the superlens 100 of any embodiment of this disclosure. The superlens 100 is disposed inside the housing and cooperates with the lens assembly.

[0052] Specifically, a specific implementation of the superlens 100 according to the embodiments of this disclosure is as follows:

[0053] First, current achromatic superlens solutions can only cover a phase retardation of about 5 fs, which limits the lens's field of view (NA) and aperture, hindering practical applications. Existing solutions cannot effectively expand the phase retardation range.

[0054] For a broadband achromatic lens, the phase distribution of light of different frequencies on the lens surface is as follows:

[0055]

[0056] Where ω is the angular frequency of the incident light, r is the radial coordinate of the lens surface, c is the speed of light, and F is the focal length of the lens. As can be seen from the above equation, incident light at different positions on the lens surface will acquire different phase values; and at the same position on the lens surface, light of different frequencies will also acquire different phase values.

[0057] Expanding equation (1) using Taylor series yields a new expression:

[0058]

[0059] Where, ω d It is a certain frequency in the middle of the wide band. Equation (2) shows that the phase at the surface of the achromatic lens can be split into two terms: the first term is the phase at the middle wavelength, and the second term is the phase difference required for incident light of different frequencies.

[0060] Substituting equation (1) into the second term of equation (2), we get:

[0061]

[0062] As can be seen from equation (3), the phase difference value, i.e., the phase delay, obtained by incident light of different frequencies has different values ​​at different coordinates. Therefore, in order to meet the achromatic requirements, this disclosure needs to select unit structures with different phase delays and construct a superlens according to the calculation requirements.

[0063] It can be calculated from equation (3) that the larger the aperture or NA of the superlens, the greater the required phase delay will be.

[0064] In some embodiments, such as Figure 4 As shown, the height of nanopillar 2 and the cross-sectional area of ​​nanopillar 2 satisfy the following:

[0065]

[0066] Where ω is the frequency, c is the speed of light, h is the total altitude (including air), and n eff For the effective refractive index, the cross-sectional area and height of the nanopillars are related to the effective refractive index.

[0067] like Figure 4 As shown, a nanopillar with length l, width w, and height h is placed in a region with length p, width p, and height h. The effective refractive index of the entire nanopillar is n. eff And it varies with the size of the nanopillar. When the incident light propagates from the upper surface to the lower surface, the magnitude of the propagation phase is...

[0068]

[0069] Substituting equation (4) into the second term of equation (2), we obtain the phase delay of the beam as follows:

[0070]

[0071] As can be seen from equation (5), to cover a larger range of phase retardation, on the one hand, the total height h of the nanopillar and air needs to be increased, and on the other hand, the effective refractive index n needs to be changed. eff That is, changing the size of the nanopillars.

[0072] It is understandable that, with the height of the nanopillar remaining constant, the effective refractive index n of the nanopillar can be adjusted by changing its cross-sectional area. eff This, in turn, changes the magnitude of the phase delay of the incident light.

[0073] In some embodiments, at least some of the nanopillars 2 have the same height and at least some of the nanopillars 2 have different cross-sectional areas.

[0074] It is understandable that the magnitude of the phase delay of light is related to the effective refractive index n of the nanopillar 2. eff Relatedly, the effective refractive index n of nanopillar 2eff Related to the cross-sectional area of ​​nanopillar 2, the effective refractive index n of nanopillar 2 can be changed by altering its cross-sectional area (i.e., the size of nanopillar 2) while keeping its height constant. eff This, in turn, changes the magnitude of the phase delay of light.

[0075] It is understandable that, with the cross-sectional area of ​​nanopillar 2 remaining constant, the phase delay of light can be changed by altering the height of nanopillar 2.

[0076] In this application, an achromatic metalens is constructed by changing the unit structure of length, width, and height. Each height of the structure can cover a portion of the phase retardation, ultimately achieving a phase retardation several times wider than existing methods. For ease of explanation, three GaN structures of different heights are used here to construct the achromatic metasurface lens. Figures 1-3 As shown, the three structures are arranged in a square periodic pattern with a period of P = 300 nm and heights of H = 800 nm, 1600 nm, and 2000 nm, respectively. The arrangement can use square periodic patterns, hexagonal periodic patterns, etc., and the period size can vary. The height can be changed to other values, and there can be many more variations.

[0077] Specifically, this disclosure constructs a superlens 100 with D=21um and F=19um, and the superlens 100 of this disclosure embodiment can be applied to mobile phones.

[0078] in, Figure 5 This is a distribution diagram of phase and frequency of light incident on five different sized structures when a superlens according to an embodiment of this disclosure is applied to a mobile phone. Figure 6 When a superlens according to an embodiment of this disclosure is applied to a mobile phone, a database is constructed for structures of all sizes, including distribution maps of diffraction efficiency and phase delay of incident light. Figure 7 This is a distribution diagram of the focal point of incident light in the 450-650nm range when the superlens according to an embodiment of this disclosure is applied to a mobile phone.

[0079] according to Figures 5-7 As shown, the focal lengths of all wavelengths are the same, and the focal points overlap, thus achieving the function of eliminating chromatic aberration. The achromatic lens 100 of this embodiment has an NA of 0.48, which is a significant improvement compared to existing results. By constructing achromatic lenses with a wider variety of heights and sizes, even larger NA and aperture values ​​can be achieved.

[0080] In the description of this disclosure, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0081] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0082] In this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0083] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0084] In this disclosure, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0085] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A superlens, characterized in that, include: The matrix has a circular cross-section; Multiple nanopillars are disposed on the substrate, and the height of the nanopillars gradually decreases from the center of the substrate to its edge in the radial direction of the substrate to expand the phase retardation range. In the circumferential direction of the substrate, the height of the plurality of nanopillars provided at the same radius of the substrate is consistent or at least some of the nanopillars have the same cross-sectional area; In the radial direction of the matrix, from the center of the matrix to its edge, some or all of the plurality of nanopillars have different cross-sectional areas.

2. The superlens according to claim 1, characterized in that, The height of the nanopillar and the cross-sectional area of ​​the nanopillar satisfy the following: Where ω is the frequency, c is the speed of light, h is the total height, and n eff The cross-sectional area and height of the nanopillars are related to the effective refractive index.

3. The superlens according to claim 1, characterized in that, The materials of the nanopillars include, but are not limited to, GaN, TiO2, Si, or Si3N4.

4. The superlens according to claim 1, characterized in that, The height of the multiple nanopillars is between 1 and 2000 nm.

5. The superlens according to claim 1, characterized in that, In the circumferential direction of the substrate, the multiple nanopillars located at the same radius of the substrate have the same turning angle.

6. The superlens according to claim 1, characterized in that, In the radial direction of the matrix, at least some of the nanopillars have different orientation angles.

7. A camera, characterized in that, include: case; A lens assembly, wherein the lens assembly is disposed within the housing; A superlens, wherein the superlens is any one of claims 1-6, the superlens is disposed within the housing, and the superlens cooperates with the lens assembly.

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