A broadband achromatic superlens with large field of view

Abstract

The present application relates to the field of optics, in particular to a broadband achromatic superlens with a large field of view. The superlens is composed of a cylindrical base embedded with a non-equal-height circular hole array and a nano-pillar array with a multi-ring structure. The non-equal-height circular hole array serves as the light entrance surface, and the nano-pillar array serves as the light exit surface. The circular hole array on the base has different depths and radii, and the nano-pillar array unit structure layer is composed of multiple ring bands, each ring band corresponding to a wavelength to achieve broadband achromatism. The nano-pillars arranged in the unit structure layer have various structures, such as cylindrical, annular, cross-shaped, etc. Different nano-pillar structures are used from the center to the outside, thereby reducing the mutual interference between adjacent ring bands. The materials of the unit structure layer and the base are transparent or low-absorption materials, and appropriate materials are selected according to different wavelength ranges. The superlens proposed in the present application can focus light beams of any wavelength range under a large field of view and a large spectral bandwidth.

Description

Technical Field

[0001] This invention relates to the field of optics, and more specifically to a broadband achromatic metalens with a large field of view. Background Technology

[0002] With the development of science and technology, the requirements for optical systems are trending towards miniaturization, lightweighting, and integration. Because the modulation mechanisms of traditional optical devices generally rely on the optical properties of materials and spatial geometry, traditional optical systems are typically bulky and difficult to meet these requirements. Metalenses, on the other hand, have attracted widespread attention due to their small size, ease of integration, and ability to perform flexible wavefront manipulation through subwavelength structures.

[0003] The optical properties of metalenses depend primarily on the specific geometry and arrangement of the subwavelength structures, offering unprecedented advantages in light wave control. The interaction between light and the subwavelength structures causes abrupt changes in phase, amplitude, and polarization state. Current metalens design methods can only achieve focusing under either a large field of view or a large spectral bandwidth. Metalenses capable of simultaneously achieving both a large field of view and a large spectral bandwidth have yet to be realized. Summary of the Invention

[0004] The technical problem this invention aims to solve is achieving good focusing performance under large field of view and wide spectral bandwidth. To address this problem, we propose a broadband achromatic metalens with a large field of view. The broadband achromatic metalens proposed in this invention can achieve good focusing within a wide field of view and a large spectral bandwidth.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: an array of circular holes is etched on one side of a cylindrical substrate, and a multi-ring nanopillar array is arranged on the other side of the substrate.

[0006] The invention is further configured such that the circular aperture array on the substrate has different depths and radii to modulate the aberrations of the beam with a large field of view.

[0007] The present invention is further configured such that: the nanopillar array unit structure layer is composed of multiple rings, the nanopillars are arranged in concentric circles, and each ring is arranged sequentially from the center to the edge, each ring corresponding to a wavelength, thereby achieving broadband achromaticity.

[0008] The invention is further configured such that: the central ring band adopts a cylindrical structure, the second ring band adopts a circular ring structure, and each ring band outwards adopts a different structure.

[0009] The present invention is further configured such that the coverage range of the ring band corresponding to each wavelength is determined by the size of the lens and specific requirements, and different ratios will have different effects.

[0010] The present invention is further configured such that: the material of the unit structure layer is a transparent or low-absorption material, which is Si3N4 or TiO2 in the visible light and near-infrared bands, and Si or Ge in the mid-infrared band.

[0011] The present invention is further configured such that: the substrate is a transparent or low-absorption material, which is SiO2 or Al2O3 under visible light and near-infrared light, and Si or MgF2 under mid-infrared light.

[0012] Compared with the prior art, the advantages of the present invention are as follows:

[0013] 1) The structure is simple and compact, using a variety of subwavelength unit structures. The volume of a single subwavelength structure is very small, which enables precise modulation of the phase.

[0014] 2) By adopting a structure with one side etched with circular holes and the other side arranged with multi-ring nanopillars, a good focusing effect is achieved while reducing the processing difficulty and increasing the overall stability of the structure.

[0015] 3) The different shapes of the subwavelength unit structures arranged in adjacent rings can reduce the influence between structures corresponding to different wavelengths.

[0016] 4) The materials of the substrate and nanopillars can be changed according to different wavelength ranges, thus making it suitable for incident light of any wavelength range.

[0017] 5) It can effectively focus beams with a large bandwidth and wide field of view. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the embodiments of the present invention or the prior art will be briefly described below with reference to the accompanying drawings.

[0019] Figure 1 A side view of an achromatic metalens;

[0020] Figure 2 A diagram showing the arrangement of nanopillars in an achromatic metalens;

[0021] Figure 3 Diagram showing the arrangement of the circular aperture array for an achromatic metalens;

[0022] Figure 4 Three-dimensional schematic diagrams of the subwavelength structures corresponding to wavelengths of 600nm and 900nm;

[0023] Figure 5 A three-dimensional schematic diagram of the subwavelength structure corresponding to a wavelength of 750nm; Detailed Implementation

[0024] The following is a more detailed description of a broadband achromatic metalens with a large field of view according to the present invention, with reference to the accompanying drawings. The present invention will also be further detailed below with reference to the embodiments:

[0025] A broadband achromatic metalens with a large field of view, as referenced Figure 1 The thickness H of the substrate is 30 μm. Holes are drilled under the substrate, with a depth D and a diameter D2, both of which are variables. Subwavelength structures are arranged on the top of the substrate. The meta-lens structure proposed in this invention can achieve a 60% focusing effect at an incident angle of 20° and a bandwidth of 300 nm.

[0026] Reference Figure 2 The substrate radius R1 is 15 μm, and the subwavelength unit structure coverage area radius R2 is 11 μm. Subwavelength structures with wavelengths of 600 nm, 750 nm, and 900 nm are arranged sequentially from the center to the edge. Each ring only has a subwavelength structure corresponding to the same wavelength, which can effectively reduce the influence between different wavelength structures.

[0027] Reference Figure 3 The radius R1 of the substrate is 15μm, the radius of the coverage area of ​​the circular hole is 6μm, and the size of the circular hole depends on its location.

[0028] Reference Figure 4 Since only three wavelengths were selected in this embodiment, only two unit structures were used to meet the requirements. The same structure was used for wavelengths of 600nm and 900nm. The height L1 of the subwavelength structure corresponding to wavelength 600nm is 1.2μm, and the diameter D1 is related to the specific position of the unit structure on the substrate. The height L3 of the subwavelength structure corresponding to wavelength 900nm is 1.55μm, and the diameter D3 is also related to the specific position of the unit structure on the substrate. The period W of the unit structure for both wavelengths is 0.45μm.

[0029] Reference Figure 5 The height L2 of the subwavelength structure corresponding to 750nm is 1.47μm, and the ratio of the radius r1 of the hollow portion to the radius r2 of the outer ring is 1:2. r2 is related to the specific position of the unit structure on the substrate. The period W of the unit structure is 0.45μm.

[0030] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the concept and scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the design concept of the present invention should fall within the protection scope of the present invention. The technical content for which protection is sought in the present invention has been fully described in the claims.

Claims

1. A broadband achromatic metalens with a large field of view, characterized in that: The meta-lens consists of a cylindrical substrate with an embedded array of non-uniform circular apertures and a nanopillar array with a multi-ring structure. The non-uniform circular aperture array is the incident surface of light, and the nanopillar array is the exit surface of light. The circular aperture array on the substrate has different depths and radii to modulate aberrations in a large field of view beams. The nanopillar array consists of multiple rings, with the nanopillars arranged concentrically. Each ring is arranged sequentially from the center to the edge, and each ring corresponds to a wavelength, thereby achieving broadband achromatic light transmission.

2. The broadband achromatic metalens with a large field of view as described in claim 1, characterized in that: Nanopillars have various structures, such as cylindrical, ring-shaped, and cross-shaped structures.

3. A broadband achromatic metalens with a large field of view as described in claim 1, characterized in that: From the central ring outwards, each ring has a different nanopillar structure, thus avoiding interference between adjacent rings.

4. A broadband achromatic metalens with a large field of view as described in claim 1, characterized in that: The material of the unit structure layer is transparent or low-absorption material, which is Si3N4 or TiO2 in the visible and near-infrared range, and Ge or Si in the mid-infrared range.

5. A broadband achromatic metalens with a large field of view as described in claim 1, characterized in that: The substrate is a transparent or low-absorption material, which is SiO2 or Al2O3 in the visible and near-infrared range, and Si or MgF2 in the mid-infrared range.

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