Optical dielectric metal metagrating based on Fabry-Perot resonance

Abstract

The present invention discloses an optical dielectric metal metagrating based on Fabry - Perot resonance, which is characterized in that the metagrating comprises a number of periodically distributed supercells, each supercell comprising a metal matrix, on which a number of periodically repeated grooves are provided, and the grooves are filled with dielectric materials of different thicknesses, and satisfy: #imgabs0# where k0 = 2π / λ is the wave vector of the plane wave in vacuum, N is a positive integer, ε is the dielectric constant of the dielectric material, the magnetic permeability of the dielectric material is 1, m is the number of units of the dielectric material in the supercell, that is, the number of grooves in a supercell, d i and d i+1 are the heights of the dielectric materials in the i - th and (i + 1)-th units. In the present invention, the optical dielectric metal metagrating based on Fabry - Perot resonance has a simple structure and is easy to implement. By simply filling the same dielectric material with a gradually changing thickness (impedance mismatch) in the unit, an extraordinary diffraction phenomenon with nearly perfect efficiency can be achieved.

Description

Technical Field

[0001] The invention relates to the field of optical technology, and in particular to an optical medium metal metagrating based on Fabry-Perot resonance. Background Art

[0002] In recent years, metagratings have attracted great attention in the field of electromagnetic wave control, and have realized various abnormal optical phenomena and devices. Recently, a study revealed a new diffraction law of metagratings, namely the abnormal transmission / reflection conversion related to the parity of the number of grating units m. The principle is that the phase gradient causes additional multiple total reflections in the high-order diffraction of the grating, and the number of total reflections is related to m. Therefore, this principle can also be used to realize the angular asymmetric absorption of metal gratings, and the degree of asymmetric absorption is also related to m.

[0003] Therefore, the number of units m of the metagrating is a very important degree of freedom, and studying the impact of different numbers of m on the metagrating is a very important aspect. Among them, the study of anomalous transmission / reflection conversion related to the parity of m is based on the design of acoustic metagrating, and each unit of the metagrating is designed with a microstructure to meet the required gradual phase change on the transmission interface. However, for optical metagratings, artificially designed microstructures will increase the complexity of the metagrating system. The simplest way to meet the gradual phase change of the transmission interface is to fill the unit with dielectric material, such as a dielectric material of the same thickness but with a gradual refractive index. In addition, in order to ensure that the optical metagrating has a high transmittance, the material filled in the unit is usually required to be impedance matched.

[0004] The above design method is difficult to implement in experiments, because it is almost impossible to find several materials with gradual refractive index and impedance matching. How to use only one dielectric material with impedance mismatch to achieve the requirements of gradual interface phase change and ensure high transmittance of metagrating is an urgent problem to be solved.

[0005] There have been many studies on how to improve the transmittance of gratings. FP resonance is a very important method. For example, when a wave is incident on a one-dimensional acoustic grating, the resonance of FP is excited in the grating slit, resulting in high transmission of the grating. There is also a combination of a single slit and a metal grating, and the transmission efficiency of a single slit is improved by using FP resonance.

[0006] Therefore, in order to solve the above technical problems, it is necessary to provide an optical medium metal metagrating based on Fabry-Perot resonance. Summary of the invention

[0007] In view of this, an object of the present invention is to provide an optical medium metal metagrating based on Fabry-Perot resonance to achieve a nearly perfect anomalous diffraction phenomenon.

[0008] In order to achieve the above purpose, the technical solution provided by an embodiment of the present invention is as follows:

[0009] An optical medium metal metagrating based on Fabry-Perot resonance, the metagrating comprising a plurality of periodically distributed supercells, each supercell comprising a metal substrate, a plurality of periodically repeatedly distributed grooves are provided on the metal substrate, the grooves are filled with dielectric materials of different thicknesses, and the following conditions are satisfied:

[0010]

[0011]

[0012] Where k0 = 2π / λ is the wave vector of the plane wave vacuum, N is a positive integer, ε is the dielectric constant of the dielectric material, the magnetic permeability of the dielectric material is 1, m is the number of units of the dielectric material in the supercell, that is, the number of grooves in a supercell, d i and d i+1 is the height of the dielectric material in the i-th and i+1-th units.

[0013] As a further improvement of the present invention, the phase of the plane wave when it passes through the dielectric material in the i-th groove in the supercell and reaches the transmission interface is:

[0014]

[0015] The phase of the plane wave when it passes through the dielectric material in the i+1th groove in the supercell and reaches the transmission interface is:

[0016]

[0017] in, is the initial phase of the plane wave incident on the metagrating, and h is the total thickness of the metagrating.

[0018] As a further improvement of the present invention, the transmission phase difference of adjacent units in the supercell on the transmission interface is

[0019] As a further improvement of the present invention, the number of units of the dielectric material in the supercell of the metagrating is m≥2.

[0020] As a further improvement of the present invention, in the metagrating, N=1, 2 or 3.

[0021] As a further improvement of the present invention, the transmission phase difference of adjacent units in the supercell on the transmission interface is

[0022] As a further improvement of the present invention, in the metagrating, the number of units of the dielectric material in the supercell is m=3, the dielectric constant of the dielectric material is ε=9, N=1, and the thicknesses of the dielectric material in the three units are d1=0.48μm, d2=0.97μm, and d3=1.46μm respectively.

[0023] As a further improvement of the present invention, the transmission phase difference of adjacent units in the supercell on the transmission interface is

[0024] As a further improvement of the present invention, in the metagrating, the number of units of the dielectric material in the supercell is m=4, the dielectric constant of the dielectric material ε=4, N=1, and the thicknesses of the dielectric material in the 4 units are d1=0.73μm, d2=1.45μm, d3=2.18μm, and d4=2.9μm respectively.

[0025] As a further improvement of the present invention, the transmission phase difference of adjacent units in the supercell on the transmission interface is

[0026] The beneficial effects of the present invention are:

[0027] The optical medium metal metagrating structure based on Fabry-Perot resonance in the present invention is simple and easy to implement. It only needs to fill the unit with the same medium material with gradient thickness (impedance mismatch) to achieve abnormal diffraction phenomenon with near-perfect efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a schematic cross-sectional structure diagram of the optical medium metal metagrating based on Fabry-Perot resonance of the present invention;

[0030] Figure 2 The phase difference of the transmission interface of the optical medium metal super grating of the present invention is Theoretical relationship curve with dielectric constant ε;

[0031] Figure 3 is a curve diagram showing the variation of the transmittance and transmission phase of the metagrating with the material thickness when the dielectric constant ε of the dielectric material is 9 in one embodiment of the present invention;

[0032] Figure 4The total magnetic field diagram and the corresponding magnetic field intensity and phase diagram of the metagrating when the dielectric constant ε of the dielectric material is 9 and the thickness of the dielectric material is d1=0.48μm, d2=0.97μm, and d3=1.46μm in one embodiment of the present invention;

[0033] Figure 5 is a graph showing the variation of transmittance / reflectivity of different orders of the meta-grating with the incident angle when the number of units m=3 and the dielectric constant ε of the dielectric material is 9 in one embodiment of the present invention;

[0034] Figure 6 In one embodiment of the present invention, the number of units m=3, the dielectric constant ε of the dielectric material=9, and the incident angle θ i =-30°, total magnetic field diagram of the metagrating;

[0035] Figure 7 In one embodiment of the present invention, the number of units m=3, the dielectric constant ε of the dielectric material=9, and the incident angle θ i =30°, the total magnetic field diagram of the metagrating;

[0036] Figure 8 is a curve diagram showing the variation of the transmittance and transmission phase of the metagrating with the material thickness when the dielectric constant ε of the dielectric material is 4 in another embodiment of the present invention;

[0037] Fig. 9 is a curve diagram showing the variation of transmittance / reflectivity of different orders of the metagrating with the incident angle when the number of units m=4 and the dielectric constant ε of the dielectric material is 4 in another embodiment of the present invention;

[0038] Fig.10 In one embodiment of the present invention, the number of units m=4, the dielectric constant ε of the dielectric material=4, and the incident angle θ i =-30°, total magnetic field diagram of the metagrating;

[0039] Fig.11 In one embodiment of the present invention, the number of units m=4, the dielectric constant ε of the dielectric material=4, and the incident angle θ i Total magnetic field diagram of the metagrating when =30°. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0041] The present invention discloses a simple optical dielectric metal metagrating based on Fabry-Perot resonance, that is, a dielectric material (magnetic permeability = 1) with the same dielectric constant and impedance mismatch is filled in the unit of the metagrating, and the dielectric thickness d in different units is gradually changed. When FP resonance (Fabry-Perot resonance) occurs inside the medium, the phase distribution requirements on the transmission interface of the metagrating can be met, and at the same time, it has extremely high diffraction efficiency. In addition, in the designed dielectric metal metagrating, not only is the abnormal transmission / reflection of the metagrating related to the parity of the unit number m, but the dielectric constant and material thickness d of the material filled in the unit are also completely determined by the value of m. The dielectric constant and thickness d of the material are respectively intrinsically related to m, and the present invention provides a clear expression of the dielectric constant related to m.

[0042] Ginseng Figure 1 As shown, the optical medium metal metagrating 100 based on Fabry-Perot resonance in the present invention includes a plurality of periodically distributed supercells 10, each of which includes a metal substrate 11, on which a plurality of periodically repeatedly distributed grooves 12 are provided, and the grooves are filled with dielectric materials 13 of different thicknesses, and satisfy the following conditions:

[0043]

[0044]

[0045] Where k0 = 2π / λ is the wave vector of the plane wave vacuum, N is a positive integer, ε is the dielectric constant of the dielectric material, the magnetic permeability of the dielectric material is 1, m is the number of units of the dielectric material in the supercell, that is, the number of grooves in a supercell, d i and d i+1 is the height of the dielectric material in the i-th and i+1-th units.

[0046] Specifically, the optical dielectric metal metagrating in the present invention is a one-dimensional periodic phase gradient dielectric metal metagrating. Figure 1 As shown, it is assumed that a TM polarized plane wave (the incident wave vector is in the xy plane, and the magnetic field is along the z direction) is incident on the metagrating. The metagrating in the figure is illustrated by taking two periods as an example. The total thickness of the metagrating is h, and it is periodic in the y direction with a period length of p. Each supercell contains m units, and the unit length is a. The metal matrix 11 is made of metal material, such as silver, etc. The upper part of the groove 12 represents air, and the lower part is the same dielectric material. The dielectric width is w, the dielectric constant is ε, and the magnetic permeability is 1. The thickness of the dielectric material filled in different units is d1,...,d i , ..., d m .

[0047] The phase distribution on the transmission interface of the metagrating within one period is required to be gradual and the range of change must cover 2π. Therefore, in order to meet the phase change requirements of the metagrating, the dielectric constant and thickness of the medium must also meet certain conditions. After research, it was found that in this dielectric metal metagrating, not only is the abnormal diffraction characteristics of the metagrating related to m, but more importantly, the dielectric constant and thickness of the required medium are also determined by the value of m, that is, for different numbers of units m, the corresponding dielectric constant and thickness can be found to meet the requirements of the gradual phase change of the metagrating.

[0048] First, we theoretically analyze the relationship between the number of units m and the dielectric constant ε. Assume that a TM polarized plane wave is incident on the metagrating and the wave passes through the i-th groove (filled with a dielectric thickness of d i ) reaches the transmission interface, the phase is:

[0049]

[0050] Similarly, the wave passes through the adjacent i+1th groove (filled with a dielectric thickness of d i+1 ) reaches the transmission interface, the phase is:

[0051]

[0052] in, is the initial phase of the plane wave incident on the metagrating. Therefore, the transmission phase difference between two adjacent grooves on the transmission interface is:

[0053]

[0054] At the same time, in order to ensure that the metagrating has a high transmittance, it is assumed that the wave undergoes FP resonance inside the medium (in the x direction), that is, the medium thickness d i and d i+1 All of them meet the conditions for FP resonance. Therefore, the waves pass through the thickness d i and d i+1 When the dielectric material is π, the increased phase difference between the two is also an integer multiple of π:

[0055]

[0056] Substituting formula (2) into formula (1), we can obtain:

[0057]

[0058] The phase gradient metagrating requires the phase difference between adjacent units on the transmission interface to be Therefore, for different m, there is a corresponding ε that satisfies the requirement of phase gradient on the transmission interface of the metagrating.

[0059] Ginseng Figure 2 The formula 3 shows and ε, which represent the wave passing through the thickness d i and d i+1 When the dielectric material is π, 2π and 3π, the phase difference between the two is π, 2π and 3π, that is, N = 1, 2 and 3. In theory, N can be other larger integers, but we will not draw too many here. In addition, when designing a phase gradient metagrating, the number of units is generally required to be m / 2, and the transmission phase difference between adjacent units is generally in the range of Therefore, only the range within which and ε, the light red and light blue areas in the figure represent the transmission phase difference respectively. and situation.

[0060] Next, we take N=1 as an example to explain different values ​​of m and ε. When the dielectric constant is in the range of ε>1. For example, m=3, ε=9, that is, when the thickness of the dielectric material with a dielectric constant of 9 meets the conditions for FP resonance, the transmission phase difference between adjacent units on the transmission interface is Similarly, when m = 4, ε = 4, the corresponding transmission phase difference becomes As shown in the figure, as m increases (m = 3, 4, 5, 6, ...), the required dielectric constant gradually decreases. In particular, in the limiting case, when (m tends to infinity), ε = 1, as shown at the intersection of the curves in the figure. At this time, the phase gradient metagrating degenerates into a uniform air metal grating, and there is no abnormal diffraction characteristic. However, as long as m is 2 and is a finite value, there is always a corresponding ε that meets the phase gradient requirement of the metagrating. Therefore, the proposed theoretical formula 3 is universal for optical metagratings.

[0061] When the transmission phase difference range is For different values ​​of m, a unique ε can also be found on the curve, satisfying the phase gradient condition on the transmission interface of the metagrating. becomes a negative number, but When is positive, the metagrating has the same abnormal diffraction phenomenon. The case of positive numbers is discussed further.

[0062] In a specific embodiment of the present invention, Taking ε=9 as an example, the thickness d when FP resonance occurs inside the medium is discussed. i The relationship with m.

[0063] Assume that the plane wave is incident on the i-th unit (the thickness of the medium in the groove is d i ) is a uniform grating with a period, and the specific parameters of the grating are set as follows: wavelength = 3 μm, grating thickness h = 2 μm, period length a = 1 μm, groove width w = 0.8 μm, medium thickness d i The thickness of the dielectric filled in the groove is obtained by simulation using comsol software. i Changes in the transmittance T and transmission phase of the grating of changes.

[0064] Ginseng Figure 3 As shown, curves 1 and 2 represent the transmittance and transmission phase of the uniform grating, respectively. In the transmittance curve, it can be seen that the transmittance T = 1 at several peaks (indicated by dotted lines). These full-transmittance points are caused by the FP resonance inside the medium of the grating, rather than by the overall grating thickness h (the overall grating thickness h is fixed to 2μm). Figure 3 The transmission phases corresponding to the three adjacent FP resonance points are shown by solid points 1, 2, and 3. At the same time, the transmission phase difference between them is To prove this statement, assume that the thickness of the medium in the groove of the uniform grating is i The thickness values ​​at the solid points 1, 2, and 3 in the figure are: d1=0.48μm, d2=0.97μm, d3=1.46μm, and the total magnetic field diagram of the uniform grating is drawn for further explanation.

[0065] Ginseng Figure 4 As shown in the figure, the right side is the total magnetic field diagram of a unit of the uniform grating, and the plane wave is incident from the left side. The arrows represent its incident direction and transmission direction. When the grating medium thickness is d1 = 0.48μm, d2 = 0.97μm, and d3 = 1.46μm, it can be observed from the total magnetic field diagram that the magnetic field intensity inside the medium is significantly enhanced than that in the air. Moreover, as the thickness of the medium increases, the amplitude of the magnetic field intensity inside the medium also increases, that is, the intensity of the FP resonance also increases.

[0066] In order to see the change of magnetic field more clearly, the magnetic field intensity and phase at the black dotted line in the figure are drawn. Figure 4 As shown on the left. The curve without solid points in the figure represents the magnetic field intensity, and the curve with solid points represents the phase of the magnetic field. The gray area represents the inside of the medium. It can be seen that as the thickness of the medium increases, the magnetic field amplitude inside the medium also increases. In addition, the two solid points on the curve represent the phase of the magnetic field at the upper and lower surfaces of the medium. It can be seen that the increased phase of the plane wave inside the medium with thicknesses of d1, d2 and d3 are π, 2π and 3π respectively, which conforms to the characteristics of FP resonance.

[0067] The above analysis proves that for the optical medium metal metagrating of the present invention, for different numbers of units m, the dielectric constant ε required by the medium can be determined according to equation (3), and the required thickness d of the medium can be known by using the condition of FP resonance inside the medium. i The phase difference on the transmission interface obtained by this method can indeed meet the phase gradient requirement of the metagrating. Next, the dielectric constant and dielectric thickness found in the above analysis are used to construct a metagrating, and the transmission / reflection curve and field diagram of the metagrating are obtained through numerical simulation to verify the effect of high-efficiency anomalous diffraction achieved by the dielectric metal metagrating. Assume that the thickness of the metagrating is h = 2μm, the period length is p = 3μm, one period contains 3 grooves, the groove width is w = 0.8μm, the dielectric constant of the medium in the groove is ε = 9, and the dielectric thickness is d1 = 0.48μm, d2 = 0.97μm, and d3 = 1.46μm.

[0068] The curves of the transmittance / reflectivity of the metagrating at different levels as a function of the incident angle are shown in Figure 5 As shown. Figure 5 It can be seen that when the incident angle of the plane wave is θ i When θ is less than 0°, it mainly shows low-order (n=-1) transmission (blue solid line), where i =-30°, the efficiency of anomalous transmission reaches 99.7%; when the incident angle of the plane wave is θ i When θ > 0°, since m = 3 is an odd number, it mainly manifests as a high-order (n = 1) reflection (red dashed line), where i =30°, the efficiency of abnormal reflection reaches 99.3%.

[0069] Figure 6 and Figure 7 The incident angles are given as θ i = -30° and θ i =30°, the black arrows in the figure indicate the incident direction and the anomalous transmission / reflection direction of the plane wave. The field diagram well reflects that when m=3, the dielectric metal metagrating can almost perfectly convert the incident wave into an anomalous transmission / reflection wave.

[0070] In another specific embodiment of the present invention, Taking ε=4 as an example, the required thickness of the medium is found, a dielectric metal metagrating is constructed, and its anomalous diffraction characteristics are verified.

[0071] like Figure 8 As shown in the figure, similar to the case of m=3, assuming that the plane wave is incident on the uniform grating, the specific parameters of the grating are set as follows: wavelength = 3μm, grating thickness h = 3.5μm, period length a = 0.75μm, groove width w = 0.6μm, medium thickness di The numerical simulation shows that the transmittance T (curve without solid points) and transmission phase of the grating change with the change of the medium thickness di. There are 4 transmission peaks caused by FP resonance in the medium in the figure. Their corresponding transmission phases are represented by solid dots, and the corresponding medium thicknesses are represented by gray dashed lines, which are d1 = 0.73μm, d2 = 1.45μm, d3 = 2.18μm, and d4 = 2.9μm. It can be seen that when the medium thickness meets the FP resonance condition, the corresponding transmission phase difference between adjacent ones also meets The dielectric constant and medium thickness found at this time are used to construct a metagrating. Assume that the thickness of the metagrating is h = 3.5μm, the period length is p = 3μm, one period contains 4 grooves, the groove width w = 0.6μm, the dielectric constant of the medium in the groove is ε = 4, and the medium thickness is d1 = 0.73μm, d2 = 1.45μm, d3 = 2.18μm, and d4 = 2.9μm.

[0072] The transmission / reflection curve of the metagrating is obtained through numerical simulation, such as Fig. 9 As shown. When the incident angle of the plane wave is θ i When <0°, it mainly shows low-order (n=-1) transmission (T -1 ), where in θ i =-30°, the efficiency of anomalous transmission reaches 98.5%; when the incident angle of the plane wave is θ i When θ > 0°, since m = 4 is an even number, it mainly shows high-order (n = 1) transmission (T1), where i When φ = 30°, the efficiency of anomalous transmission reaches 98.5%.

[0073] Fig.10 , Fig.11 The incident angles are given as θ i = -30° and θ i =30°, the black arrows in the figure indicate the incident direction and anomalous transmission direction of the plane wave. The field diagram well reflects that when m=4, the dielectric metal metagrating can also achieve high-efficiency wavefront control.

[0074] Therefore, combining the examples of m=3 and m=4, it is proved that in the dielectric metal metagrating of the present invention, the dielectric constant of the filling material in the unit and the thickness of the material do have a definite relationship with the number of units m and conform to the theoretical formula (3) given by us.

[0075] The optical medium metal metagrating structure of the present invention is simple and easy to realize. It only needs to fill the unit with the same medium material with gradient thickness (impedance mismatch) to achieve the abnormal diffraction phenomenon with nearly perfect efficiency.

[0076] The optical meta-grating in the present invention not only has its anomalous diffraction characteristics related to the parity of the number of units m, but more importantly, the dielectric constant ε and material thickness of the material filled in the unit are also determined by the value of m. The principle is that for different numbers of units m, there is a certain dielectric constant, so that when FP resonance occurs inside the medium, the phase accumulation provided by the air part and the medium part in the groove just meets the phase distribution required by the transmission interface of the meta-grating. And the present invention provides a clear relationship between the dielectric constant ε and m.

[0077] Therefore, the metagrating model and theoretical formula in the present invention have certain guiding significance for realizing an optical metagrating with simple structure and high efficiency.

[0078] It can be seen from the above technical solutions that the present invention has the following beneficial effects:

[0079] The optical medium metal metagrating structure based on Fabry-Perot resonance in the present invention is simple and easy to implement. It only needs to fill the unit with the same medium material with gradient thickness (impedance mismatch) to achieve abnormal diffraction phenomenon with near-perfect efficiency.

[0080] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0081] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An optical medium metal metagrating based on Fabry-Perot resonance, characterized in that: The metagrating includes a plurality of periodically distributed supercells, each of which includes a metal substrate, on which a plurality of periodically repeatedly distributed grooves are provided, and the grooves are filled with dielectric materials of different thicknesses and satisfy the following conditions: Where k0 = 2π / λ is the wave vector of the plane wave vacuum, N is a positive integer, ε is the dielectric constant of the dielectric material, the magnetic permeability of the dielectric material is 1, m is the number of units of the dielectric material in the supercell, that is, the number of grooves in a supercell, d i and d i+1 is the height of the dielectric material in the i-th and i+1-th units; The phase of the plane wave when it passes through the dielectric material in the i-th groove in the supercell and reaches the transmission interface is: The phase of the plane wave when it passes through the dielectric material in the i+1th groove in the supercell and reaches the transmission interface is: in, is the initial phase of the plane wave incident on the metagrating, h is the total thickness of the metagrating; The transmission phase difference of adjacent units in the supercell on the transmission interface is The number of units of the dielectric material in the supercell of the metagrating is m≥2.

2. The optical medium metal metagrating based on Fabry-Perot resonance according to claim 1, characterized in that: In the metagrating, N=1, 2 or 3.

3. The optical medium metal metagrating based on Fabry-Perot resonance according to claim 1, characterized in that: The transmission phase difference of adjacent units in the supercell on the transmission interface is 4. The optical medium metal metagrating based on Fabry-Perot resonance according to claim 1, characterized in that: In the metagrating, the number of units of the dielectric material in the supercell is m=3, the dielectric constant of the dielectric material ε=9, N=1, and the thicknesses of the dielectric materials in the three units are d1=0.48μm, d2=0.97μm, and d3=1.46μm respectively.

5. The optical medium metal metagrating based on Fabry-Perot resonance according to claim 4, characterized in that: The transmission phase difference of adjacent units in the supercell on the transmission interface is 6. The optical medium metal metagrating based on Fabry-Perot resonance according to claim 1, characterized in that: In the metagrating, the number of units of the dielectric material in the supercell is m=4, the dielectric constant of the dielectric material is ε=4, N=1, and the thicknesses of the dielectric materials in the four units are d1=0.73μm, d2=1.45μm, d3=2.18μm, and d4=2.9μm respectively.

7. The optical medium metal metagrating based on Fabry-Perot resonance according to claim 6, characterized in that: The transmission phase difference of adjacent units in the supercell on the transmission interface is

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