Wide-view-field super lens based on unit inclination angle independent control

Abstract

The invention provides a wide-view-field super lens based on independent control of unit inclination angles, and relates to the technical field of super lenses, the wide-view-field super lens comprises a diaphragm, a silicon dioxide substrate located above the diaphragm and a super structure unit located on the silicon dioxide substrate, and the super structure unit is a cylindrical silicon column. And each cylindrical silicon column is inclined at a certain angle alpha relative to the normal direction of the silicon dioxide substrate. According to the technical scheme, the problems that in the prior art, a super lens cannot achieve high-precision imaging, the structure is complex, and complete field-of-view imaging cannot be achieved are solved.

Description

Technical Field

[0001] The present invention relates to the field of metalenses, and in particular to a wide-field metalenses based on independent control of unit tilt angles. Background Art

[0002] A superlens is a new type of planar optical device that can precisely control the wavefront of light. It is composed of several meta-units that carry the focusing phase. By changing the geometric parameters of the meta-units, the properties of light such as amplitude, phase, and polarization can be flexibly controlled. Compared with traditional optical devices, superlenses have the advantages of being ultra-thin, ultra-light, and flexible to control. However, under large-angle illumination, superlenses inevitably have aberrations such as coma, field curvature, and astigmatism, which affect the imaging quality of superlenses in wide field of view and hinder their application in actual scenarios.

[0003] In order to overcome the above problems, the prior art has proposed a variety of solutions, mainly covering aspects such as multi-layer metasurface lens design, metasurface lens convergence phase correction and metalens structure design.

[0004] The multi-layer metasurface lens design effectively reduces the control pressure on a single metasurface layer by increasing the control dimension. However, while this method improves the imaging effect, it not only greatly increases the complexity of the design, but also destroys the original planar characteristics of the metasurface lens.

[0005] For the method of convergence phase correction of metasurface lenses, quadratic phase distribution is a typical means. It can convert the linear phase generated by oblique incidence into spatial phase shift, so that the focus of the oblique incident light beam produces a spatial displacement related to the incident angle. However, this method has limitations. The light only meets the quadratic phase focusing criterion under the condition of paraxial approximation. Other light will form background noise and affect the imaging quality. To solve this problem, a filter aperture is usually used to limit the incident light to achieve wide-angle field imaging without background noise. However, although this method improves the wide-angle field imaging performance, it inevitably introduces spherical aberration. Therefore, only when the focal length of the metasurface lens is much larger than its own size can relatively accurate imaging be barely achieved.

[0006] As for the design method of super lens structure, Li Tao's research team at a certain university uses the overall tilt of all units of the super lens to manufacture a super surface lens, achieving efficient focusing of large-angle light beams. However, to achieve full field of view imaging, multiple lenses must be combined, which undoubtedly increases the complexity of the structure.

[0007] Therefore, there is a need for a wide-field metalens based on independent control of the unit tilt angle that can achieve high-precision imaging. Summary of the invention

[0008] The main purpose of the present invention is to provide a wide-field metalens based on independent control of the unit tilt angle, so as to solve the problems that the metalens in the prior art cannot achieve high-precision imaging, has a complex structure, and cannot achieve full-field imaging.

[0009] To achieve the above objectives, the present invention provides a wide-field metalens based on independent control of the unit tilt angle, comprising: an aperture, a silicon dioxide substrate located above the aperture, and a metastructure unit located on the silicon dioxide substrate, wherein the metastructure unit is a cylindrical silicon column, and each cylindrical silicon column is tilted at a certain angle α relative to the normal direction of the silicon dioxide substrate.

[0010] Furthermore, multiple cylindrical silicon pillars are evenly distributed on the silicon dioxide substrate, and the multiple cylindrical silicon pillars form multiple angles α with the normal direction of the silicon dioxide substrate. The range formed by the multiple angles α is the same as the range of the field of view of the super lens, that is, the angle α covers the entire field of view.

[0011] Furthermore, the height H of the cylindrical silicon pillar is in the range of 0.1 to 2 micrometers.

[0012] Further, the height of the cylindrical silicon pillar is H=740 nm.

[0013] Furthermore, the distance between the aperture and the silicon dioxide substrate is L, and a coordinate system is established with the center of the silicon dioxide substrate as the origin, then:

[0014]

[0015] where x and y are the coordinates of the metacell on the silicon dioxide substrate.

[0016] Furthermore, the theoretical phase carried by the metalens is:

[0017]

[0018] in, represents the phase value, λ represents the working wavelength of the superlens, and f is the preset focal length.

[0019] Furthermore, the preset focal length f ranges from 10 to 200 micrometers.

[0020] Furthermore, the focal length f=20 μm is preset.

[0021] Furthermore, the axial direction of the meta-unit points to the center of the aperture.

[0022] Furthermore, the aperture is made of PVC material, and the superstructure unit is made of silicon.

[0023] The present invention has the following beneficial effects:

[0024] The present invention can achieve wide-field imaging in the near-infrared band with only a single metalens, and has the characteristics of high resolution, high integration, and ultra-wide field of view. Compared with the traditional quadratic phase metalens, it has higher precision, a larger field of view than the hyperbolic phase metalens, and a simple and compact structure. It has broad application prospects in the fields of projection, videography, infrared detection, medical diagnosis, etc., and provides new ideas for the design of wide-field metalens elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the specific implementation or the prior art description. Obviously, the drawings described below are some implementations of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0026] Figure 1 A schematic diagram of the principle of a wide-field metalens based on independent control of the unit tilt angle of the present invention is shown.

[0027] Figure 2 A stereoscopic diagram of a wide-field metalens based on independent control of the unit tilt angle of the present invention is shown.

[0028] Figure 3 A schematic diagram of the tilt angle of the superstructure unit is shown.

[0029] Figure 4 The wide-field focusing light field of the wide-field superlens provided by the present invention is shown.

[0030] Figure 5 Shows Figure 2 The full width at half maximum of the focal point of the wide-field focusing of the metalens.

[0031] Figure 6 Shows Figure 2 Modulation transfer function of the metalens wide-field focusing.

[0032] The reference numerals in the above drawings are:

[0033] 10. Aperture; 21. Silicon dioxide substrate; 22. Metacell; 30. Focal plane. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] like Figure 1 and Figure 2 A wide-field metalens based on independent control of the unit tilt angle is shown, comprising: an aperture, a silicon dioxide substrate located above the aperture, and a metastructure unit located on the silicon dioxide substrate, wherein the metastructure unit is a cylindrical silicon column, each of which is tilted at a certain angle α relative to the normal direction of the silicon dioxide substrate. The light wave is incident on the aperture along a certain angle, propagates through the aperture to the silicon dioxide substrate, and the tilt phase of the incident light is compensated by the tilt of the metastructure unit, so that the light beam is redirected and focused to the preset focal length of the metastructure unit.

[0036] like Figure 1 and Figure 2 As shown, a light beam incident at a certain angle passes through the aperture 10 and irradiates the meta-unit 22. The meta-unit here is tilted relative to the normal direction of the metalens. The tilt angle is set to be related to the distance L from the aperture to the silicon dioxide substrate 21 and the position r of the meta-unit. The tilt of the meta-unit can compensate for the phase difference caused by the tilt of the light beam. The metalens is set to carry a hyperbolic phase profile that can accurately focus the light beam. The light beam after the wavefront phase is compensated will be focused to the focal plane 30 at a preset distance f from the metalens, thereby achieving high-precision wide-field imaging.

[0037] Specifically, Figure 3 As shown, multiple cylindrical silicon pillars are evenly distributed on the silicon dioxide substrate, and the multiple cylindrical silicon pillars form multiple angles α with the normal direction of the silicon dioxide substrate. The range formed by the multiple angles α is the same as the range of the field of view of the super lens, that is, the angle α covers the entire field of view.

[0038] Specifically, the height H of the cylindrical silicon column is in the range of 0.1 to 2 micrometers, and specifically H=740 nm.

[0039] Specifically, the distance between the aperture and the silicon dioxide substrate is L, and a coordinate system is established with the center of the silicon dioxide substrate as the origin, then:

[0040]

[0041] where x and y are the coordinates of the metacell on the silicon dioxide substrate.

[0042] The independent setting of the tilt angles of the super-structure units at different positions can not only achieve a wide-field imaging effect, but also improve the imaging accuracy.

[0043] Specifically, the theoretical phase carried by the metalens is:

[0044]

[0045] in, represents the phase value, λ represents the working wavelength of the superlens, and f is the preset focal length.

[0046] Specifically, the preset focal length f is 10 to 200 micrometers.

[0047] Specifically, the focal length f=20 μm is preset.

[0048] Specifically, the axial direction of the meta-unit points to the center of the aperture.

[0049] Specifically, the aperture is made of PVC material and the superstructure unit is made of silicon.

[0050] like Figure 4 As shown, the first row of images is the focused light field intensity distribution in the axial xz plane, and the second row of images is the focused light field intensity distribution in the radial xy plane. The preset focal length f = 20μm, the working wavelength λ = 0.94μm. When the incident light angle changes from 0° to 60°, the focused spot shape remains well-shaped and there is no sidelobe interference.

[0051] like Figure 5 and Figure 6 As shown, the imaging performance of this embodiment is quantitatively evaluated by introducing the modulation transfer function (MTF) and the full width at half maximum (FWHM). At low spatial frequencies, the metasurface lens presents similar MTF values ​​for incident light at different angles. At higher spatial frequencies, the MTF value of the metasurface lens decreases slightly as the angle of incidence increases. The smaller the FWHM value, the higher the focusing resolution. In the entire field of view, the minimum FWHM value is 1.1 wavelengths and the maximum is 2.6 wavelengths, which means that the wide-field metalens provided by the present invention can still maintain good imaging quality at a larger field of view.

[0052] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A wide-field metalens based on independent control of unit tilt angles, characterized in that: include: An aperture, a silicon dioxide substrate located above the aperture, and a superstructure unit located on the silicon dioxide substrate, wherein the superstructure unit is a cylindrical silicon column, and each cylindrical silicon column is inclined at a certain angle α relative to the normal direction of the silicon dioxide substrate.

2. A wide-field metalens based on independent control of unit tilt angles according to claim 1, characterized in that: A plurality of cylindrical silicon pillars are evenly distributed on a silicon dioxide substrate, and the plurality of cylindrical silicon pillars form a plurality of angles α with the normal direction of the silicon dioxide substrate. The range formed by the plurality of angles α is the same as the range of the field of view of the super lens, that is, the angle α covers the entire field of view.

3. A wide-field metalens based on independent control of unit tilt angles according to claim 1, characterized in that: The height H of the cylindrical silicon column ranges from 0.1 to 2 microns.

4. A wide-field metalens based on independent control of unit tilt angles according to claim 3, characterized in that: The height of the cylindrical silicon pillar is H = 740 nm.

5. A wide-field metalens based on independent control of unit tilt angles according to claim 1, characterized in that: The distance between the aperture and the silicon dioxide substrate is L. The coordinate system is established with the center of the silicon dioxide substrate as the origin, then: where x and y are the coordinates of the metacell on the silicon dioxide substrate.

6. A wide-field metalens based on independent control of unit tilt angles according to claim 1, characterized in that: The theoretical phase carried by the superlens is: in, represents the phase value, λ represents the working wavelength of the superlens, and f is the preset focal length.

7. A wide-field metalens based on independent control of unit tilt angles according to claim 6, characterized in that: The preset focal length f ranges from 10 to 200 microns.

8. A wide-field metalens based on independent control of unit tilt angles according to claim 7, characterized in that: The preset focal length f=20 μm.

9. A wide-field metalens based on independent control of unit tilt angles according to claim 1, characterized in that: The axis of the superstructure unit points to the center of the aperture.

10. A wide-field metalens based on independent control of unit tilt angles according to claim 1, characterized in that: The aperture is made of PVC material and the superstructure unit is made of silicon.

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