Metasurface unit structure and metasurface formed by metasurface unit structure

Abstract

The utility model discloses a metasurface unit structure and a metasurface formed by the metasurface unit structure, and belongs to the technical field of nonlinear optics. The metasurface unit structure comprises a substrate layer and a dielectric layer which are arranged from bottom to top, wherein a convex groove or a concave groove is formed in the dielectric layer. The sections of the substrate layer and the dielectric layer are square, and the sizes are nanoscale; the substrate layer is made of SiO2, and the dielectric layer is made of DAST crystals. The metasurface is formed by periodically arranging a plurality of metasurface unit structures. According to the utility model, the convex or concave grooved structure, the substrate layer with low refractive index, the DAST dielectric layer which has a higher damage threshold and is easy to process and the like are introduced, so that the loss can be reduced, the asymmetry degree can be conveniently adjusted by changing the grooved structure, the quality factor Q can be changed, the local electric field distribution can be optimized, and different application requirements can be met.

Description

TECHNICAL FIELD

[0001] The utility model belongs to nonlinear optics technical field, more specifically relates to a kind of metasurface unit structure and metasurface by its composition. BACKGROUND

[0002] Nonlinear optics is an important part of modern optics;Nonlinear optical effects have wide applications in optical signal processing, optical sensing, laser technology, etc. Metasurface is a kind of artificial composite structure, which can control the phase, amplitude and polarization of electromagnetic waves (such as light, microwave). Traditional metasurface unit structure usually adopts overall symmetric structure, which has the problems of single structure, high loss and low Q value, which cannot meet different application requirements. SUMMARY

[0003] Therefore, the utility model provides a kind of metasurface unit structure and metasurface by its composition to at least solve part of the technical problems described above, which is beneficial to reduce loss, enhance quality factor Q value, etc. by introducing "convex" or "concave" groove structure design, to adapt to different application requirements.

[0004] To achieve the above purpose, the utility model adopts the following technical solutions:

[0005] In one preferred embodiment, the metasurface unit structure adopts a subwavelength structure, and the cross sections of the substrate layer and the dielectric layer are both square with a nanoscale size.

[0006] In one preferred embodiment, the substrate layer and the dielectric layer are both square with a side length of 600 nm, the substrate layer has a height of 1200 nm, and the dielectric layer has a height of 300 nm.

[0007] In one preferred embodiment, the substrate layer is composed of SiO2.

[0008] In one preferred embodiment, the dielectric layer is composed of 4-(4-dimethylaminostyryl) methylpyridine p-toluenesulfonic acid base salt (i.e. DAST crystal).

[0009] In one preferred embodiment, the dielectric layer is composed of 4-(4-dimethylaminostyryl) methylpyridine p-toluenesulfonic acid base salt (i.e. DAST crystal).

[0010] In one preferred embodiment, the dielectric layer is composed of 4-(4-dimethylaminostyryl) methylpyridine p-toluenesulfonic acid base salt (i.e. DAST crystal).

[0011] Compared with the prior art, the utility model has at least the following advantages:

[0012] 1.The utility model provides a kind of super surface unit structure, by introducing the slot structure of " convex " or " concave " change single symmetry structure, it is helpful to reduce loss, improve quality factor Q value.

[0013] 2.In the utility model, the medium layer is grooved, which can adjust the asymmetry of the super surface unit structure by adjusting the size of the groove, and the specific asymmetry can be set according to the specific application requirements, which helps to optimize the local electric field distribution and adapt to different application requirements.

[0014] 3.In the utility model, the size of the super surface unit structure is accurate to nanometer level, which ensures the local enhancement effect of light wave on the surface. Specifically, the super surface unit structure adopts square cross section, and the size of each unit cell is accurately adjusted (such as 600nm side length and different height), which can make the super surface unit structure have strong electromagnetic field localization effect and improve the quality factor Q.

[0015] 4.In the utility model, the substrate layer is composed of SiO2, and the medium layer is composed of DAST crystal. DAST crystal has high damage threshold; it can effectively reduce the efficiency reduction caused by light loss, and DAST material is easy to process and cut.

[0016] Other features and advantages of the utility model will be described in the subsequent specification, and some of them will become apparent from the specification, or be understood by implementing the utility model. The purpose and other advantages of the utility model can be achieved and obtained by the structure specially pointed out in the written specification and drawings.

[0017] The technical scheme of the utility model will be further described in the following drawings and examples. DETAILED DESCRIPTION

[0018] The drawings are used to provide further understanding of the utility model, and constitute part of the specification, together with the embodiments of the utility model, to explain the utility model, and do not constitute limitation on the utility model; in the drawings:

[0019] Figure 1 The " convex " super surface unit structure schematic diagram provided by the utility model.

[0020] Figure 2 The " concave " super surface unit structure schematic diagram provided by the utility model.

[0021] Figure 3 The super surface schematic diagram composed of " convex " super surface unit structure provided by the utility model.

[0022] Figure 4The utility model provides a by "concave" character shape super surface unit structure composition's super surface schematic diagram.

[0023] Figure 5 The utility model provides a "convex" character shape super surface unit structure's transmissivity schematic drawing.

[0024] Figure 6 The utility model provides a "convex" character shape super surface unit structure's electric field distribution schematic drawing, wherein, (a) part is x-y plane electric field distribution, (b) part is y-z plane electric field distribution, (c) part is z-x plane electric field distribution.

[0025] Figure 7 The utility model provides a "convex" character shape super surface unit structure's transmissivity curve schematic drawing under 4 kinds of d, wherein, (a) part in d = 90nm, (b) part in d = 70nm, (c) part in d = 50nm, (d) part in d = 30nm.

[0026] Figure 8 The utility model provides a "convex" character shape super surface unit structure's Q value changes with asymmetry curve schematic drawing.

[0027] Figure 9 The utility model provides a "concave" character shape super surface unit structure's transmissivity schematic drawing

[0028] Figure 10 The utility model provides a "concave" character shape super surface unit structure's electric field distribution schematic drawing, wherein, (a) part is x-y plane electric field distribution, (b) part is y-z plane electric field distribution, (c) part is z-x plane electric field distribution.

[0029] Figure 11 The utility model provides a "concave" character shape super surface unit structure's transmissivity curve schematic drawing under 4 kinds of d, wherein, (a) part in d = 10nm, (b) part in d = 20nm, (c) part in d = 30nm, (d) part in d = 40nm.

[0030] Figure 12 The utility model provides a "concave" character shape super surface unit structure's Q value changes with asymmetry curve schematic drawing. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the utility model.

[0032] Referring to Figures 1-2 The utility model embodiment provides a kind of metasurface unit structure, which includes substrate layer and dielectric layer arranged from bottom to top. Wherein, the dielectric layer is "convex" slot or "concave" slot, by adjusting the value of length d in convex slot and concave slot, the asymmetry of metasurface unit structure can be changed, and the specific asymmetry can be set according to specific application requirements, without specific limitation.

[0033] The utility model introduces slot structure design, changes the shape structure of traditional metasurface unit structure usually adopts symmetric structure, which is beneficial to reduce loss, improve quality factor Q etc. A unit is composed of dielectric layer and substrate layer, its top is nonlinear material DAST layer, substrate is SiO2 layer, the asymmetry of metasurface unit structure is controlled by the difference of slot structure, and the size and shape of asymmetric structure can be set according to specific application requirements. The working principle and specific implementation of the utility model are described in detail as follows:

[0034] In the embodiment, metasurface unit structure adopts subwavelength structure, and the size is accurate to nanometer level, which ensures the local enhancement effect of light wave on surface. In a specific embodiment, referring to Figure 1 And Figure 2 As shown in the drawings, the cross section of metasurface unit structure is regular polygon, and the cross section of substrate layer and dielectric layer of metasurface unit structure is square; in a preferred embodiment, the side length Px and the side length Py are 600nm, the substrate layer height is 1200nm, the dielectric layer height H is 300nm; the height of slot is 300nm; the size of "convex" structure of slot is: side length L=340nm, side length W=160nm, side length d=90nm; the size of "concave" structure of slot is: side length L=340nm, side length W=160nm, side length d=40nm.

[0035] Further, based on the above metasurface unit structure is periodically arranged, the utility model further provides metasurface composed of "convex" metasurface unit structure and metasurface composed of "concave" metasurface unit structure, and the specific structure is shown in Figure 3 And Figure 4 .

[0036] Further, the utility model discloses the advantage of the above-mentioned super surface unit structure through experiment verification, and specifically as follows:

[0037] As shown in Figure 5 And Figure 9 In the experiment, by changing the groove structure, the transmission band can be effectively adjusted, the "convex" groove produces a transmission valley at 1014nm, and the "concave" groove produces a transmission valley at 1043nm. Figure 6 And Figure 10 As shown in, at the designed groove area, the electric field intensity is significantly enhanced, high-quality resonance is carried out in the asymmetric structure, so that the Q factor is significantly increased. Figure 7 And Figure 11 As shown in, by changing the asymmetry in the super surface unit structure, the transmission valley of the transmittance curve moves towards the direction of larger wavelength, the bandwidth at the resonance of the transmission spectrum gradually decreases, and the valley value shows a downward trend. Figure 8 And Figure 12 As shown in, by changing the asymmetry in the super surface unit structure, the Q value can be effectively adjusted, the peak value range can be flexibly adjusted in the range of 500-1500, and the Q value continuously increases with the increase of the asymmetry, and the application scene is more extensive.

[0038] From the description of the above embodiment, those skilled in the art can know that the utility model provides a super surface unit structure and a super surface composed of the same, and the specific advantages are as follows:

[0039] (1) structural innovation:

[0040] The specific shape and structure are as follows:

[0041] Asymmetry structure: the conventional super surface unit structure usually adopts a symmetric structure, and the utility model introduces groove design, so that the geometric shape of each super surface unit structure is associated with the structure of the groove. The distribution of the light field can be accurately controlled by adjusting the value of the side length d, so as to improve the quality factor Q. This structure design is flexible and can effectively adjust the quality factor in multiple wave bands, and is particularly suitable for different demand applications.

[0042] Unit size structure: each super surface unit structure adopts a subwavelength structure, and the size is accurate to nanometer level, which ensures the local enhancement effect of light waves on the super surface. The design of the super surface unit includes a substrate layer and a dielectric layer, each layer has specific optical functions and interactions. Specifically, a single super surface unit adopts a square cross section, and the size is accurately adjusted (such as a side length of 600nm and different heights), so that the super surface has a strong electromagnetic field localization effect, which helps to improve the generation efficiency of the second harmonic.

[0043] (2) asymmetry and optical effect enhancement:

[0044] The medium layer groove design adopted by the utility model is convenient for improving the performance of the super surface in nonlinear optics. The design breaks the limitation of traditional symmetric design by introducing an asymmetric structure in each super surface unit structure, and brings the following remarkable effects:

[0045] Asymmetry adjustment: the asymmetry is adjusted and set through the groove design of the medium layer, and the groove shape and size can be changed to realize accurate adjustment of the optical performance of the super surface. Under different wave bands and working conditions, the Q can be controlled by changing the asymmetry, thereby meeting more extensive application requirements.

[0046] Enhancement of local electric field: the asymmetric structure can effectively enhance the local electric field, improve the interaction between light and material, and thus significantly improve the quality factor Q.

[0047] (3) Optimization design of multi-layer structure:

[0048] Substrate layer: the substrate layer adopts a low refractive index material (such as SiO2), and its main function is to provide support for light transmission and reduce light loss on the surface. The thickness and structure size of the substrate layer are optimized to ensure effective propagation of light and reduce scattering and reflection.

[0049] Medium layer: the medium layer selects DAST material, which can ensure the best nonlinear optical conversion efficiency, effectively enhance the second harmonic effect, and reduce loss. DAST material is also relatively easy to process and cut, so that the super surface is easier to manufacture, reduces the processing difficulty, and reduces the cost of high-precision nanometer processing.

[0050] The above is only the preferred embodiment of the utility model, and it should be pointed out that for ordinary technical personnel in the technical field, some improvements and refinements can be made without departing from the principle of the utility model. The above description of the disclosed embodiments enables a person skilled in the art to implement or use the utility model. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the utility model. Therefore, the utility model will not be limited to these embodiments shown in the text, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A metasurface unit structure, characterized in that, The super surface unit structure comprises, from bottom to top, a substrate layer and a medium layer, wherein: the medium layer is provided with convex grooves or concave grooves.

2. A metasurface unit structure according to claim 1, wherein, The cross sections of the substrate layer and the medium layer are both square, and the size is nanoscale.

3. A metasurface unit structure according to claim 2, wherein, The side length of the substrate layer and the medium layer is both 600 nm, the height of the substrate layer is 1200 nm, and the height of the medium layer is 300 nm.

4. The metasurface unit structure of claim 1, wherein, The substrate layer is composed of SiO2.

5. The metasurface unit structure of claim 1, wherein, The medium layer is composed of DAST crystal.

6. A metasurface characterized in that, An arrangement of the super surface unit structure according to any one of claims 1-5.

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