WO2022067616A1 - Transmission structure, optical device and optical system - Google Patents

Abstract

A transmission structure (100), an optical device and an optical system. The transmission structure (100) comprises a plurality of transmission units (10) periodically arranged in one surface. Each transmission unit (10) comprises: a first transmission element (I, 11); and a second transmission element (II, 12) in contact with the first transmission element (I, 11); an electromagnetic wave incident surface (P12) of the second transmission element (II, 12) and an electromagnetic wave incident surface (P11) of the first transmission element (I, 11) jointly form an electromagnetic wave incident surface of the transmission unit (10), wherein the transmission phase of the electromagnetic wave of the second transmission element (II, 12) is the same as or similar to the transmission phase of the electromagnetic wave of the first transmission element (I, 11), and a reflection coefficient of the electromagnetic wave of the second transmission element (II, 12) is different from a reflection coefficient of the electromagnetic wave of the first transmission element (I, 11). According to the transmission structure (100), the reflection wave can form grating diffraction in the reflection side space, and meanwhile, the transmission wave reserves wave front information of the incident wave.

Description

Transmission structure, optical device and optical system technical field

The invention relates to the technical field of electromagnetic metamaterials, in particular to a transmission structure, an optical device and an optical system.

Background technique

Optical elements composed of a large number (thousands or even tens of thousands) of parallel slits of equal width and equal spacing are called diffraction gratings. However, there are many types of modern gratings, and the diffraction units of some gratings are no longer slits in the usual sense. To allow the definition of diffraction gratings to also be included within these gratings, gratings are defined as optical elements that produce periodic spatial modulation of the amplitude or phase, or both, of incident light. A generalized grating can be defined as all optical devices that can play the role of periodic division of wavefronts. The periodic division of wavefronts mainly includes three situations: (1) the amplitude of the periodic division of wavefronts; (2) ) the phase on the periodic segmented wavefront; (3) the amplitude and phase on the periodic segmented wavefront. In a broad definition, only one of the three conditions is satisfied to determine that the optical device is a grating (or at least has the function of a grating).

Specifically, gratings are classified according to their modulation effects on incident light, and can be divided into amplitude gratings and phase gratings:

The amplitude grating mainly includes a rectangular grating that can modulate the amplitude of incident light waves according to the change of a rectangular function, and a sine grating that can be modulated according to the change of the sine and cosine function. However, the traditional amplitude grating has low modulation efficiency for incident light, and causes periodic division of the amplitude in the incident light wavefront, so that the transmitted light cannot accurately maintain the wavefront information of the incident light.

Phase gratings mainly include transmissive binary phase gratings and reflective binary phase gratings. Among them, the transmission type binary phase grating can be fabricated by processing high transmission optical materials into periodic structures of plateaus and depressions. Among them, the phase in the incident light wavefront is periodically divided, and the transmitted wave has two kinds of phase delays in the plateau and the depression respectively (that is, the grating diffraction is formed in the transmission side space), however, the wavefront of the transmitted light is seriously disturbed at this time. , the wavefront information of the incident light cannot be preserved. Reflective binary phase gratings can be fabricated by processing high-reflection optical materials into periodic structures of plateaus and depressions, or by adding high-reflection coatings to similar periodic structures. The phase in the incident light wavefront is periodically divided, and the reflected wave has two phase delays in the plateau and the depression respectively (that is, the grating diffraction is formed in the reflection side space). However, at this time, the incident light cannot pass through the grating at all, There is no transmitted light.

SUMMARY OF THE INVENTION

According to various embodiments of the present application, a transmissive structure is provided.

A transmission structure, comprising a plurality of transmission units arranged periodically in one side, the transmission units comprising,

a first transmissive element; and,

The second transmission element, the electromagnetic wave incidence surface of the second transmission element and the electromagnetic wave incidence surface of the first transmission element together form the electromagnetic wave incidence surface of the transmission unit; the electromagnetic wave incidence of the plurality of transmission units The surfaces together form the electromagnetic wave incident surface of the transmission structure;

Wherein, the difference between the transmission phase of the electromagnetic wave of the second transmission element and the transmission phase of the electromagnetic wave of the first transmission element is within a preset range, and the reflection coefficient of the electromagnetic wave of the second transmission element is the same as that of the first transmission element. The reflection coefficients of the electromagnetic waves of the transmission elements are different.

According to another aspect of the present application, an optical device is provided, including the transmission structure described in the above embodiments.

According to yet another aspect of the present application, an optical system is provided, including the optical device described in the above embodiments.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the present application will become apparent from the description, drawings and claims.

Description of drawings

In order to better describe and illustrate embodiments or examples of those inventions disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the drawings should not be construed as limiting the scope of any of the disclosed inventions, the presently described embodiments or examples, and the best mode presently understood of these inventions.

1 is a schematic diagram of the electromagnetic wave incident effect of the transmission structure of the application;

Fig. 2 is the transflective phase schematic diagram of the transmission structure of the present application;

3 is a schematic structural diagram of a transmission structure according to another embodiment of the present application;

4 is a schematic structural diagram of a transmission unit according to another embodiment of the present application;

FIG. 5 is a schematic structural diagram of the first transmission element 11 and the second transmission element 12 according to still another embodiment of the present application;

FIG. 6 is a schematic structural diagram of the transmission structure of the embodiment shown in FIG. 5;

Figures (a) to (d) in FIG. 7 respectively show the electromagnetic wave transmission phase curve, reflection phase difference curve, Transmission curve and reflectance curve;

Figures (a) to (d) in Figure 8 respectively show schematic diagrams of far-field radiation when electromagnetic waves of different wavelengths are normally incident on the transmission structure of the embodiment shown in Figure 5;

Figures (a) to (d) in Figure 9 respectively show schematic diagrams of far-field radiation when electromagnetic waves of different wavelengths are incident at an oblique angle of 10° to the transmission structure of the embodiment shown in Figure 5;

Figures (a) to (d) in Figure 10 respectively show schematic diagrams of far-field radiation when electromagnetic waves of different wavelengths are obliquely incident at 20° to the transmission structure of the embodiment shown in Figure 5;

Figures (a) to (d) in Figure 11 respectively show schematic diagrams of far-field radiation when electromagnetic waves of different wavelengths are obliquely incident at 30° to the transmission structure of the embodiment shown in Figure 5;

FIG. 12 is a schematic structural diagram of the first transmission element 11 and the second transmission element 12 according to still another embodiment of the application;

FIG. 13 is a schematic structural diagram of the first transmission element 11 and the second transmission element 12 according to still another embodiment of the application;

FIG. 14 is a schematic structural diagram of the first transmission element 11 and the second transmission element 12 according to still another embodiment of the present application.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for the purpose of illustration only and do not represent the only embodiment.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used herein in the specification of the application are for the purpose of describing specific embodiments only, and are not intended to limit the application. The technical features of the above embodiments can be combined arbitrarily. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features It is considered to be the range described in this specification.

Traditional gratings can be used as spectrometers for spectral decomposition, or as waveguide gratings for input and output coupling of optical waveguides. Specifically, the grating equation can be used:

to describe the principle of diffraction and spectroscopy of electromagnetic waves, where d represents the grating constant,

represents the diffraction angle, θ represents the incident angle, m represents the spectral order of the bright fringes, and λ represents the wavelength of the incident electromagnetic wave. When the length of the grating slit or obstacle is close to or less than the wavelength of the electromagnetic wave, significant diffraction phenomenon can occur. It can be inferred from the grating equation that the diffraction angle of the m-order diffracted light of a grating with a given period is related to the wavelength. The larger the wavelength, the larger the diffraction angle. For example, when visible white light is incident, color diffraction with different diffraction orders can be formed. pattern.

However, neither the traditional transmission grating nor the reflection grating can keep the wavefront of the transmitted light from being disturbed while splitting the light. At this time, the transmitted light cannot keep the wavefront information of the incident light, which causes certain limitations for the application of the grating.

Referring to FIGS. 1 and 2 , the present application provides a transmission structure 100 , which can transmit waves without changing the wavefront of the transmitted waves, maintain the wavefront information of the incident light, and at the same time diffract the reflected waves. Wherein x represents the extension direction of the transmission structure 100 , z represents the normal direction of the electromagnetic wave incident surface of the transmission structure 100 , and y represents the direction perpendicular to the x-z plane.

As shown in FIG. 1 , the transmissive structure 100 includes a plurality of transmissive units 10 periodically arranged along the x direction in the x-z plane, each transmissive unit 10 is adjacent to each other in sequence, and the transmissive unit 10 includes at least one first transmissive element I and at least one second transmissive element I Transmissive element II. Taking the example shown in FIG. 1 , the transmissive unit 10 is composed of a first transmissive element I and a second transmissive element II, and the first transmissive element I and the second transmissive element II are arranged in contact with each other.

Further, the electromagnetic wave incident surface of the first transmission element I and the electromagnetic wave incident surface of the second transmission element II together form the electromagnetic wave incident surface of the transmission unit 10, and the electromagnetic wave incident surfaces of the plurality of transmission units 10 can be formed together. The electromagnetic wave incident surface of the transmission structure 100 . In addition, when the electromagnetic wave incident surface of the transmission structure 100 needs to be set as a special-shaped surface (such as a curved surface), the size of the first transmission element I and the second transmission element II can be appropriately reduced, and then the first transmission element I and the second transmission element II can be appropriately reduced. The electromagnetic wave incident surface of the second transmission element II should be arranged on the special-shaped surface. Therefore, the present application does not limit the surface type of the electromagnetic wave incident surface of the transmission structure 100 .

The transmission phase of the electromagnetic wave of the second transmission element II is the same or similar to the transmission phase of the electromagnetic wave of the first transmission element I, and the reflection coefficient of the electromagnetic wave of the second transmission element II is different from the reflection coefficient of the electromagnetic wave of the first transmission element I. .

Specifically, in the electromagnetic wave theory, the transmission coefficient includes the amplitude and phase of the transmitted wave, the mode of the transmission coefficient indicates the amplitude of the transmitted wave, and the square of the mode of the transmission coefficient indicates the transmittance of the electromagnetic wave; correspondingly, the reflection coefficient includes the amplitude of the reflected wave With phase, the mode of the reflection coefficient indicates the amplitude of the reflected wave, and the square of the mode of the reflection coefficient indicates the reflectivity of the electromagnetic wave. The difference between the transmission phases of the first transmission element I and the second transmission element II is within a preset range, so that the transmitted wave can maintain the wavefront information of the incident electromagnetic wave, which is conducive to the spatial imaging of the electromagnetic wave on the transmission side. Further, the preset range can be

in

represents the transmission phase of the electromagnetic wave of the second transmission element II,

Indicates the transmission phase of the electromagnetic wave of the first transmission element I. By controlling the transmission phase of the electromagnetic wave of the second transmission element II and the transmission phase of the electromagnetic wave of the first transmission element I to satisfy the above relationship, the electromagnetic wave transmitted from the transmission structure 100 can better retain the wavefront information of the incident wave, which is beneficial to The transmission side of the transmission structure 100 is spatially imaged, and the formed image has a certain clarity. Specifically, the transmission phase difference of the two transmission elements

Can be 0, 0.1π, 0.2π, 0.3π, 0.4π, or 0.5π. In addition, if the transmittances of the first transmission element I and the second transmission element II are also the same or similar, it is beneficial to further improve the imaging quality of the transmitted wave.

The reflection coefficient of the electromagnetic wave of the second transmission element II is different from the reflection coefficient of the electromagnetic wave of the first transmission element I, which includes the following three cases:

(1) The reflection phase of the electromagnetic wave of the second transmission element II is different from the reflection phase of the electromagnetic wave of the first transmission element I;

(2) The mode of the reflection coefficient of the electromagnetic wave of the second transmission element II (used to characterize the reflectivity) is different from the mode of the reflection coefficient of the electromagnetic wave of the first transmission element I. At this time, the reflection of the electromagnetic wave of the second transmission element II The phase can be the same as the reflection phase of the electromagnetic wave of the first transmission element I;

(3) The reflection phase of the electromagnetic wave of the second transmission element II is different from the reflection phase of the electromagnetic wave of the first transmission element I, and the mode of the reflection coefficient of the electromagnetic wave of the second transmission element II is different from the reflection coefficient of the electromagnetic wave of the first transmission element I model is different.

In the case (1), after the electromagnetic wave is incident on the transmission structure 100, as shown in FIG. 2, the reflected wave has different phase responses, and each reflected phase is divided periodically, and spatial interference occurs on the reflection side Constructive and interference are destructive to form an uneven distribution of diffraction orders, that is, a phase grating-like effect can be achieved in the reflection side space. As shown in Figure 1, 2 orders (m=1 and m=2) can be formed Diffraction pattern. Meanwhile, since the transmission phase of the transmitted wave is not disturbed by the transmission structure 100, the transmitted wave still maintains the wavefront information of the incident wave.

In case (2), after the electromagnetic wave is incident on the transmission structure 100, the reflected waves have different amplitude responses, and each reflected amplitude is periodically divided, and the waves are superimposed and subtracted in the space of the reflection side to form The distribution of diffracted orders with uneven strength and weakness, that is, in the reflection side space, can achieve the effect similar to the amplitude grating. Meanwhile, since the transmission phase of the transmitted wave is not disturbed by the transmission structure 100, the transmitted wave still maintains the wavefront information of the incident wave.

In case (3), after the electromagnetic wave is incident on the transmission structure 100, the reflected wave has different phase responses and amplitude responses, and each type of reflection phase and each type of reflection amplitude are periodically divided, and the reflection side The spatial formation of the corresponding waves is constructive and destructive to form a distribution of diffracted orders with uneven strength and weakness. Meanwhile, since the transmission phase of the transmitted wave is not disturbed by the transmission structure 100, the transmitted wave still maintains the wavefront information of the incident wave.

On the other hand, if a clear diffraction pattern is to be formed on the reflection side space of the transmission structure 100, the size of the first transmission element I and the second transmission element II can be made smaller than or equal to the wavelength of the incident electromagnetic wave, so as to better satisfy the diffraction requirements. condition.

It should be noted that the aforementioned transmission unit 10 is composed of a first transmission element I and a second transmission element II, and the transmission units 10 are periodically arranged along the x direction in the x-z plane to form a one-dimensional transmission structure 100 . In other embodiments, the first transmission element I and the second transmission element II may also be periodically arranged in the x-direction and the y-direction, respectively, so as to form a two-dimensional transmission structure 200, as shown in FIG. 3 , At this time, the transmission unit 20 includes two diagonally arranged first transmission elements I and two diagonally arranged second transmission elements II, and the plurality of transmission units 20 are periodically arranged in columns along the x direction in the x-y plane (or Periodically arranged in rows along the y-direction), so that a finer amplitude and/or phase division of the spatial reflection wave on the reflection side can be achieved, and the applicable range of the transmission structure is broadened.

The above-mentioned transmission structure 100 uses the first transmission element I and the second transmission element II with the same or similar transmission phases and different reflection coefficients to form the transmission unit 10, and the transmission units 10 are periodically arranged in one surface, so that when the electromagnetic wave is incident on the transmission unit 10 When the structure 100 is transmitted, the amplitude and/or phase of the spatially reflected wave on the reflection side is periodically divided, thereby forming multiple diffraction orders, realizing the function of the grating; at the same time, the wavefront of the spatially transmitted wave on the transmission side will not be disturbed, The wavefront information of the incident light can be accurately maintained, which is beneficial to the further utilization of the transmitted wave. In addition, the size of the first transmission element I and the second transmission element II can also be adjusted so that the transmission structure 100 is suitable for different wavelength bands, such as visible light wavelength band and microwave wavelength band, so as to achieve application coverage of different wavelength bands.

In an exemplary embodiment, the reflection phase of the electromagnetic wave of the second transmission element II

and the reflection phase of the electromagnetic wave of the first transmission element I

Satisfy

By controlling the reflection phase of the electromagnetic wave of the second transmission element II and the reflection phase of the electromagnetic wave of the first transmission element I to satisfy the above relationship, since the transmission units 10 are periodically arranged in the x direction, various types of responses with different periodic phases can be made. The reflected wave is diffracted in the space on the reflection side of the transmission structure 100 to form a plurality of diffraction order patterns to achieve a function similar to a phase grating. Specifically, the reflection phase difference of the two transmission elements may be 0.6π, 0.7π, 0.8π, 0.9π, 1.0π, 1.1π, 1.2π, 1.3π or 1.4π. It can be understood that, according to the sine and cosine function diagram, the reflection phase difference of the electromagnetic wave can be substantially up to π, where 1.4π means that the reflection phase difference of the two transmission elements has been substantially further reduced.

In the exemplary embodiment, the mode r ₂ of the reflection coefficient of the electromagnetic wave of the second transmission element II and the mode r ₁ of the reflection coefficient of the electromagnetic wave of the first transmission element I satisfy

Alternatively, r ₂ /r ₁ ≥3. By controlling the mode r ₂ of the reflection coefficient of the electromagnetic wave of the second transmission element II and the mode r ₁ of the reflection coefficient of the electromagnetic wave of the first transmission element I to satisfy the above relationship, since the transmission units 10 are periodically arranged in the x direction, it is possible to make A variety of reflected waves with different periodic amplitude responses are spatially diffracted on the reflection side of the transmission structure 100 to form a plurality of diffraction order patterns to achieve a function similar to an amplitude grating. Specifically, the ratio of the modes of the reflection coefficients of the two transmission elements may be 0.1, 0.15, 0.2, 0.25, 0.3, or may be 3, 4, 5, or 6.

In an exemplary embodiment, the transmissive structure can be designed through the manipulation of the effective relative permittivity and effective relative permeability of the material.

Specifically, please refer to FIG. 4 , the first transmission element I has an effective relative permittivity ε ₁ and an effective relative permeability μ ₁ , and the second transmission element II has an effective relative permittivity ε ₂ and an effective relative permeability μ ₂ . According to the transmission matrix theory of electromagnetics, the transmission coefficient and reflection coefficient of the first transmission element I and the second transmission element II are calculated respectively, so that the effective relative permittivity value ε ₁ of the first transmission element I and the second transmission The value of effective relative permeability μ ₂ of element II satisfies

And the value of the effective relative permeability μ ₁ of the first transmission element I and the value of the effective relative permittivity ε ₂ of the second transmission element II satisfy

Therefore, the first transmission element I and the second transmission element II have similar transmission coefficient and reflectivity, and the reflection phase difference is close to π, so that the transmission structure has better transmission wave to retain the incident wave front information, and the reflected wave forms The effect of grating diffraction.

Further, the first transmission element I includes a first electric resonance structure and a first magnetic resonance structure, the first electric resonance structure is used for adjusting the effective relative permittivity ε ₁ of the first transmission element I, and the first magnetic resonance structure is used for adjusting the effective relative permittivity ε 1 of the first transmission element I. Adjust the effective relative permeability μ ₁ of the first transmission element I; the second transmission element II includes a second electric resonance structure and a second magnetic resonance structure, and the second electric resonance structure is used to adjust the effective relative dielectric of the second transmission element II The electric constant ε ₂ , the second magnetic resonance structure is used to adjust the effective relative permeability μ ₂ of the second transmission element II. Electrical resonance means that the structure can generate an effective current under the excitation of an external electric field. From the perspective of energy transfer, the energy of the external electric field can be coupled into the structure through resonance, and the energy coupled into the structure can be generated by the oscillation of the effective current. Radiated outward; magnetic resonance means that the structure can generate effective magnetic current under the excitation of the external magnetic field. From the perspective of energy transfer, the energy of the external magnetic field can be coupled into the structure through resonance, and the energy coupled into the structure can pass through The resulting oscillations of the effective magnetic current radiate outward.

Preferably, the above-mentioned electrical resonance structures and magnetic resonance structures can be prepared by artificial metamaterials. For example, both the first transmission element I and the second transmission element II can adjust their respective effective relative dielectrics through electrical resonance structures such as metal wire arrays, metal sheet arrays, V-type metal arrays, cross-type metal arrays, or H-type metal arrays. Constant; both the first transmission element I and the second transmission element II can adjust their respective effective relative permeability through magnetic resonance structures such as C-shaped metal split ring array, metal helix array or dielectric column array. Further, by adjusting the electrical resonance structure and the magnetic resonance structure in the two transmission elements respectively, the effective relative permittivity value ε ₁ of the first transmission element I and the effective relative magnetic permeability of the second transmission element II can be achieved. The values of μ ₂ are equal, the value of the effective relative permeability μ ₁ of the first transmission element I is equal to the value of the effective relative permittivity ε ₂ of the second transmission element II, so that the transmission structure has better transmission wave retention. The incident wave has wavefront information, while the reflected wave forms the effect of grating diffraction.

In another embodiment, the first transmission element I and the second transmission element II have an array of metal rods for adjusting the effective relative permittivity and an array of metal split rings for adjusting the effective relative permeability; wherein the first transmission element The metal rods in element I and the metal rods in the second transmissive element II are of different sizes, and/or the metal split rings in the first transmissive element I and the metal split rings in the second transmissive element II are of different sizes. Preferably, a metal rod in the two transmission elements can be correspondingly arranged in a metal split ring, so as to form a "mountain" type (that is, an "E" type with the opening facing upwards) structure, and then, by adjusting the The size of the metal rod and the size of the metal split ring in each transmission element are such that the value ε ₁ of the effective relative permittivity of the first transmission element I and the value of the effective relative permeability μ ₂ of the second transmission element II satisfy

And the value of the effective relative permeability μ ₁ of the first transmission element I and the value of the effective relative permittivity ε ₂ of the second transmission element II satisfy

It can be understood that the size of the metal rod includes but is not limited to the length, width and thickness of the metal rod, and the size of the metal split ring includes but is not limited to the inner diameter and thickness of the metal split ring. Further, the sizes of the metal rod arrays and the metal ring arrays in the two transmission elements can be adjusted to make the effective relative permittivity value ε ₁ of the first transmission element I and the effective relative magnetic permeability of the second transmission element II. The value of the ratio μ ₂ is equal, the value of the effective relative permeability μ ₁ of the first transmission element I is equal to the value of the effective relative permittivity ε ₂ of the second transmission element II, so that the transmission structure has a better transmission wave The wavefront information of the incident wave is preserved, while the reflected wave forms the effect of grating diffraction.

In addition, the transmission structure of the present application can also be prepared using materials in nature. For example, nickel-zinc ferrite materials, whose relative permittivity can be adjusted in the range of 10-1000, and the relative permeability of magnetic materials existing in nature and the effective relative permeability of artificial composite materials can also cover a large range. Therefore, by selecting two suitable uniform materials in nature, the relative permittivity value of the first transmission element I and the relative magnetic permeability value of the second transmission element II can also be satisfied.

And the relative permeability value of the first transmission element I and the relative permittivity value of the second transmission element II satisfy

In an exemplary embodiment, the first transmission element I includes a first part and a second part arranged in sequence along the normal direction of the electromagnetic wave incident surface of the transmission unit, wherein the effective relative permittivity of the first part is the same as that of the second part. The effective relative permittivity of the parts is different, and/or the effective relative permeability of the first part is different from that of the second part; the second transmission element II includes a normal line along the electromagnetic wave incident surface of the transmission unit The second part and the first part are arranged in sequence, and the second transmission element II and the first transmission element I are stacked along the normal direction of the electromagnetic wave incident surface of the transmission unit to form a mirror-symmetrical structure. The mirror symmetry here means that the second transmission element II and the first transmission element I can be mirror images of each other after being stacked along the normal direction of the electromagnetic wave incident surface of the transmission unit, and the mirror surface is the second transmission element II and the first transmission element I. interface.

Specifically, please refer to FIG. 5 and FIG. 6 , FIG. 5 shows a schematic structural diagram of the first transmission element I and the second transmission element II, and FIG. 6 shows a schematic structural diagram of the transmission structure 300 formed by the transmission element structure. Wherein, the first transmission element I is indicated by the symbol "11", the second transmission element II is indicated by the symbol "12", the first transmission element 11 has an electromagnetic wave incident surface P11, and the second transmission element 12 has an electromagnetic wave incident surface. P12 , the electromagnetic wave incident plane P11 and the electromagnetic wave incident plane P12 together form the electromagnetic wave incident plane of the transmission unit 30 . It can be seen from FIG. 6 that the transmission unit 30 is obtained by arranging the first transmission element 11 and the second transmission element 12 in a plane parallel to the x-y plane. At this time, the electromagnetic wave of the first part 1 of the first transmission element 11 emits The entrance surface P11 and the electromagnetic wave entrance surface P12 of the second part 2 of the second transmission element 12 together form the electromagnetic wave entrance surface of the transmission unit 30 , and the transmission structure 300 is obtained by arranging the transmission units 30 periodically along the x direction.

Further, referring to FIGS. 5 and 6 , the first transmission element 11 is made of two materials (the first part 1 and the second part 2 ) along the normal direction of the electromagnetic wave incident surface of the transmission unit 30 (ie, z in the figure). The electromagnetic wave incident surface P11 of the first transmission element 11 is the electromagnetic wave incident surface of the first part 1, wherein the first part 1 and the second part 2 have different relative permittivity and/ Or a single material with different relative magnetic permeability; correspondingly, the second transmission element 12 is formed by arranging the second part 2 and the first part 1 along the normal direction of the electromagnetic wave incident surface of the transmission unit 30, and the second transmission element 12 The electromagnetic wave incident surface P12 is the electromagnetic wave incident surface of the second part 2 . Under the structure of the transmission element, the transmission coefficient of the first transmission element 11 and the transmission coefficient of the second transmission element 12 can be calculated by the transmission matrix theory to be approximately the same, and the reflection coefficient of the first transmission element 11 is the same as that of the second transmission element 12. The different reflection coefficients may specifically include the situations (1), (2), and (3) described above.

Further, taking silicon dioxide (SiO2) as the material of the first part 1, the length d1=110nm of the first part 1, taking silicon (Si) as the material of the second part 2, the length d2=110nm of the second part 2 , a mirror-symmetric structure can be formed when the first transmission element 11 and the second transmission element 12 are stacked along the normal direction of the electromagnetic wave incident surface of the transmission unit 30 . The transmittance, reflectance, transmission phase, and reflection phase difference of the first transmission element 11 and the second transmission element 12 can be calculated by the above conditions. Figures (a) to (d) in FIG. 7 show the transmittance curve, reflectivity curve, transmission phase curve and reflection phase difference of the first transmission element 11 and the second transmission element 12 under silicon dioxide and silicon materials, respectively curve. Among them, in the figures (a) to (c), the solid line represents the first transmission element 11, and the dotted line represents the second transmission element 12. It can be seen that the first transmission element 11 and the second transmission element 12 transmit in the visible light frequency band The reflectivity is basically the same as the transmission phase, and the reflectivity is also approximately the same. As can be seen from Figure (d), the reflection phase difference between the first transmission element 11 and the second transmission element 12 maintains a large value in a wide frequency band. , especially in the vicinity of 630nm, the phase difference of the two transmission elements reaches π (that is, it can be used as a phase grating), which is more conducive to the transmission wave of the corresponding transmission structure to retain the wavefront information of the incident wave, while the reflected wave has obvious The effect of grating diffraction.

Next, simulation software is used to simulate the far-field radiation of the transmission structure 300 under different incident angles of electromagnetic waves.

(1) Normal incidence (incidence along the z-axis direction)

The Gaussian electromagnetic waves with wavelengths of 650 nm, 635 nm, 580 nm and 540 nm are taken to be normal incident on the transmission structure 300 , and the corresponding far-field radiation results are shown in (a) to (d) of FIG. 8 , respectively. The dashed line in the figure represents the orientation of the transmissive structure 300. Taking the arrangement shown in FIG. 8 as an example, the upper part of the dashed line represents the reflection side space of the transmissive structure 300, and the lower part of the dashed line represents the transmission side space of the transmissive structure 300. It can be seen that in the transmission side space, the transmission of electromagnetic waves of each wavelength is concentrated in one direction (180°), indicating that the wavefront of the transmitted wave is not disturbed, and the wavefront information of the incident Gaussian wave can be better maintained; In the reflection side space, since the wavefront of the reflected wave is periodically cut and has different phase responses, multiple diffraction orders will be formed in different directions, and the reflected waves of different wavelengths in the non-zero diffraction order The diffractive angles are different (that is, the grating equation can be better satisfied), which means that the transmission structure 300 can achieve a good diffracted light splitting effect on the reflected wave under normal incidence.

(2) 10° oblique incidence (the angle formed by the incident electromagnetic wave and the z-axis is 10°)

Gaussian electromagnetic waves with wavelengths of 650 nm, 635 nm, 580 nm and 540 nm are incident on the transmission structure 300 at an oblique angle of 10°, and the corresponding far-field radiation results are shown in (a) to (d) of FIG. 9 , respectively. The dashed line in the figure represents the orientation of the transmissive structure 300 . Taking the arrangement shown in FIG. 9 as an example, the upper part of the dashed line represents the reflection side space of the transmissive structure 300 , and the lower part of the dashed line represents the transmission side space of the transmissive structure 300 . It can be seen that in the transmission side space, the transmission of electromagnetic waves of each wavelength is concentrated in one direction (180°), indicating that the wavefront of the transmitted wave is not disturbed, and the wavefront information of the incident Gaussian wave can be better maintained; In the reflection side space, the reflected waves form multiple diffraction orders in different directions, and the diffraction angles of the reflected waves of different wavelengths in the non-zero diffraction orders are different (that is, the grating equation can be better satisfied), indicating that the transmission structure 300 At 10° oblique incidence, it can achieve a good diffraction and splitting effect on the reflected wave.

(3) 20° oblique incidence (the angle formed by the incident electromagnetic wave and the z-axis is 20°)

Gaussian electromagnetic waves with wavelengths of 650 nm, 635 nm, 580 nm and 540 nm are incident on the transmission structure 300 at an oblique angle of 20°, and the corresponding far-field radiation results are shown in (a) to (d) of FIG. 10 respectively. The dashed line in the figure represents the orientation of the transmissive structure 300 . Taking the arrangement shown in FIG. 10 as an example, the upper part of the dashed line represents the reflection side space of the transmissive structure 300 , and the lower part of the dashed line represents the transmission side space of the transmissive structure 300 . It can be seen that in the transmission side space, the transmission of electromagnetic waves of each wavelength is concentrated in one direction (180°), indicating that the wavefront of the transmitted wave is not disturbed, and the wavefront information of the incident Gaussian wave can be better maintained; In the reflection side space, the reflected wave forms multiple diffraction orders in different directions, and the diffraction angles of the reflected waves of different wavelengths in the non-zero diffraction order are different (that is, the grating equation can be better satisfied), indicating the transmission structure. The 300 can achieve good diffraction and splitting effect on reflected waves at 20° oblique incidence.

(4) 30° oblique incidence (the angle formed by the incident electromagnetic wave and the z-axis is 30°)

Gaussian electromagnetic waves with wavelengths of 650 nm, 635 nm, 580 nm and 540 nm are incident on the transmission structure 300 obliquely at 30°, and the corresponding far-field radiation results are shown in (a) to (d) of FIG. 11 respectively. The dashed line in the figure represents the orientation of the transmissive structure 300 . Taking the arrangement shown in FIG. 11 as an example, the upper part of the dashed line represents the reflection side space of the transmissive structure 300 , and the lower part of the dashed line represents the transmission side space of the transmissive structure 300 . It can be seen that in the transmission side space, the transmission of electromagnetic waves of each wavelength is concentrated in one direction (180°), indicating that the wavefront of the transmitted wave is not disturbed, and the wavefront information of the incident Gaussian wave can be better maintained; In the reflection side space, the reflected wave forms multiple diffraction orders in different directions, and the diffraction angles of the reflected waves of different wavelengths in the non-zero diffraction order are different (that is, the grating equation can be better satisfied), indicating the transmission structure. The 300 can achieve good diffraction and splitting effect on reflected waves at 30° oblique incidence.

In the exemplary embodiment, the first transmission element 11 and the second transmission element 12 also have structures of other shapes. Please refer to FIG. 12 , the first transmissive element 11 and the second transmissive element 12 are formed of the same single material, and the shape of the side of the first portion 1 away from the second portion 2 is the same as the shape of the side of the second portion 2 away from the first portion 1 . The shapes of the sides are different. Taking the example shown in FIG. 11, the single material can be a trapezoidal material. In the first transmission element 11, the lower bottom surface of the trapezoidal material is the incident surface P11 of the electromagnetic wave, and the upper bottom surface is the electromagnetic wave exit surface. The first part 1 of the element 11 is the part including the incident surface P11, and the second part 2 is the other part including the exit surface; correspondingly, in the second transmission element 12, the upper bottom surface of the trapezoidal material is the radiation of electromagnetic waves. The entrance surface P12 and the lower bottom surface are the electromagnetic wave exit surface, and the electromagnetic wave entrance surface P11 and the electromagnetic wave entrance surface P12 together form the electromagnetic wave entrance surface of this type of transmission unit. At this time, when the first transmission element 11 and the second transmission element 12 are stacked along the normal direction of the electromagnetic wave incident plane P11 (or the electromagnetic wave incident plane P12 ), a mirror-symmetric structure can be formed. Through the transmission matrix theory, it can also be proved that the transmission coefficients of the first transmission element 11 and the second transmission element 12 are substantially the same, but the reflection coefficients are different. It can be understood that, the shape of the single material may also be other shapes such as a triangle, a sector, and the like, and this embodiment does not limit the specific shape of the single material.

In the exemplary embodiment, the above single material can be selected as a light-transmitting material, so as to realize the application of this embodiment in the optical frequency band. The light-transmitting material includes at least one of glass, resin, transparent crystal, liquid crystal, transparent liquid, and gas. Furthermore, the light-transmitting material can be selected from glass, resin, transparent crystal (eg crystal), liquid crystal, transparent liquid or air. The transparent liquid can be water, sodium chloride solution, alcohol and other transparent non-metallic liquids.

In exemplary embodiments, the first portion and/or the second portion may be compositely formed of at least two different materials such that the effective relative permittivity of the first portion is different from the effective relative permittivity of the second portion and/or Or the effective relative permeability of the first part is different from the effective relative permeability of the second part. The effective parameters of the composite material can be calculated by Maxwell-Garnett theory, Bruggeman theory, etc. according to the corresponding applicable conditions.

Specifically, please refer to FIG. 13 , the first part and the second part of the first transmission element 11 can be respectively formed by arranging a variety of materials with different dielectric constants and/or magnetic permeability along the normal direction of the incident surface of the transmission structure , that is, the first transmission element 11 is formed by the arrangement of material 1, material 2...material n-1, material n, wherein the first part can be composed of any material between material 1 and material n-1, and the second part can be composed of Any material between material 2 and material n is combined, for example, the first part is composed of material 1 to material n-2, and the second part 2 is composed of material n-1 and material n; correspondingly, the second transmission element 12 It is composed of material n, material n-1 . . . material 2 and material 1. The arrangement of the second part and the first part is the same as the above arrangement, and will not be repeated here. Further, when the first transmission element 11 and the second transmission element 12 are stacked in a direction perpendicular to the plane M, a mirror-symmetrical structure can be formed. The plane M passes through the center of the first transmission element 11 and is parallel to the electromagnetic wave incident plane P11 . Likewise, it can be proved by transmission matrix theory that the first transmission element 11 and the second transmission element 12 have the same transmission coefficient to electromagnetic waves but different reflection coefficients. In this embodiment, the effective relative permittivity and effective relative permeability of the first part and the second part can be calculated by Maxwell-Garnett theory.

Further, in the above-mentioned embodiment, the first part and the second part can be arranged in a layered structure, which is beneficial to the application of preparing optical films. The optical film can be used in optical path design or optical instruments requiring light splitting and transmission, thereby simplifying optical path design or increasing the application range of optical instruments.

In an exemplary embodiment, please refer to FIG. 14 , the first part of the first transmission element 11 includes a first base body 111 , the second part includes a second base body 112 , and a first insert is provided on the surface or inside of the first base body 111 , and/or a second insert block is arranged on the surface or inside of the second base body 112 . Taking the example shown in FIG. 14 , the first base body 111 has no inserts inside, and the second base body is provided with inserts 1121 . At this time, the inserts 1121 can be arranged at any position in the second part, and the number of inserts 1121 can also be multiple. . Of course, the first insert block can also be arranged inside the first base body 111, and the second insert piece can be arranged inside the second base body 112. In this case, the shape and/or material of the first insert piece and the second insert piece need to be different. Or the positions of the two in the first substrate 111 and the second substrate 112 make the first transmissive element 11 form an asymmetric structure, so as to ensure that the first part of the first transmissive element 11 and the second part of the first transmissive element 11 are connected. The effective permittivity and/or effective permeability are different. It should be pointed out that the asymmetry here means that when the shape and material of the first insert and the second insert are the same, the second transmissive element 12 cannot overlap with the first transmissive element 11 through translation. In addition, since metal particles have been widely used in nanofabrication technology, the first block and the second block can be not only dielectric blocks, but also metal blocks and semiconductor blocks, such as copper blocks, Iron nuggets, silver nuggets, plastics, sphalerite, etc. Continuing to refer to FIG. 14 , the first transmission element 11 can be set as a cube, the insert 1121 is set as a cylindrical shape and extends inward from the electromagnetic wave exit surface of the first transmission element 11 , and the second transmission element 12 is perpendicular to the first transmission element 11 along the A mirror-symmetrical structure can be formed when the plane M is stacked in the direction, and the plane M passes through the center of the first transmission element 11 and is parallel to the electromagnetic wave incident plane P11 .

The present application also provides an optical device comprising the transmissive structure as described above. The above-mentioned optical device can transmit the incident wave without disturbing the wavefront of the transmitted wave, and simultaneously diffract the spatially reflected wave on the reflection side to form multiple diffraction orders, which reflects the function of the grating.

The present application also provides an optical system including the optical device as described above. The above-mentioned optical system can obtain the image formed by the transmitted light in the space of the transmission side of the optical device, and can also obtain the spectral line distribution pattern of the reflected light in the space of the reflection side of the optical device, which is conducive to simplifying the design of the optical path and improving the optical design effect.

The above-mentioned embodiments only represent several embodiments of the present application, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the scope of protection of the patent of the present application shall be subject to the appended claims.

Claims (20)

1. A transmission structure, characterized in that it comprises a plurality of transmission units arranged periodically in one surface, the transmission units comprising:

   a first transmissive element; and,

   The second transmission element is arranged in contact with the first transmission element, and the electromagnetic wave incident surface of the second transmission element and the electromagnetic wave incident surface of the first transmission element together form the electromagnetic wave incident surface of the transmission unit;

   Wherein, the difference between the transmission phase of the electromagnetic wave of the second transmission element and the transmission phase of the electromagnetic wave of the first transmission element is within a preset range, and the reflection coefficient of the electromagnetic wave of the second transmission element is the same as that of the first transmission element. The reflection coefficients of the electromagnetic waves of the transmission elements are different.
2. The transmission structure according to claim 1, wherein the transmission phase of the electromagnetic wave of the second transmission element

   

   and the transmission phase of the electromagnetic wave of the first transmission element

   

   Satisfy

   
3. The transmission structure according to claim 1, wherein the reflection coefficient of the electromagnetic wave of the second transmission element is different from the reflection coefficient of the electromagnetic wave of the first transmission element, and specifically includes:

   The reflection phase of the electromagnetic wave of the second transmission element is different from the reflection phase of the electromagnetic wave of the first transmission element; and/or the mode of the reflection coefficient of the electromagnetic wave of the second transmission element is different from that of the first transmission element. The modes of reflection coefficients of electromagnetic waves are different.
4. The transmission structure according to claim 3, wherein the reflection phase of the electromagnetic wave of the second transmission element

   

   and the reflection phase of the electromagnetic wave of the first transmission element

   

   Satisfy

   
5. The transmission structure according to claim 3, wherein the mode r ₂ of the reflection coefficient of the electromagnetic wave of the second transmission element and the mode r ₁ of the reflection coefficient of the electromagnetic wave of the first transmission element satisfy

   

   Alternatively, r ₂ /r ₁ ≥3.
6. The transmission structure according to any one of claims 1-5, wherein the value of the effective relative permittivity of the first transmission element and the value of the effective relative permeability of the second transmission element satisfy

   

   The value of the effective relative permeability of the first transmission element and the value of the effective relative permittivity of the second transmission element satisfy

   
7. The transmission structure according to claim 6, wherein,

   The first transmission element includes a first electric resonance structure and a first magnetic resonance structure, the first electric resonance structure is used to adjust the effective relative permittivity of the first transmission element, and the first magnetic resonance structure is used for adjusting the effective relative permittivity of the first transmission element. for adjusting the effective relative permeability of the first transmission element;

   The second transmission element includes a second electrical resonance structure and a second magnetic resonance structure, the second electrical resonance structure is used to adjust the effective relative permittivity of the second transmission element, and the second magnetic resonance structure is used for adjusting the effective relative permittivity of the second transmission element. for adjusting the effective relative permeability of the second transmission element.
8. The transmissive structure according to claim 7, wherein the first transmissive element and the second transmissive element each comprise an array of metal rods for adjusting the effective relative permittivity and an array for adjusting the effective relative permeability Array of metal split rings;

   The sizes of the metal rods in the first transmission element and the metal rods in the second transmission element are different, and/or the metal split ring in the first transmission element is different from the metal rod in the second transmission element Metal split rings come in different sizes.
9. The transmission structure according to any one of claims 1-5, wherein,

   The first transmission element includes a first part and a second part arranged in sequence along the normal direction of the electromagnetic wave incident surface of the transmission unit, wherein the effective relative permittivity of the first part is the same as that of the second part. the effective relative permittivity of the parts is different, and/or the effective relative permeability of the first part is different from the effective relative permeability of the second part;

   The second transmission element includes the second part and the first part arranged in sequence along the normal direction of the electromagnetic wave incident surface of the transmission unit, and the second transmission element and the first transmission element A mirror-symmetrical structure is formed when stacked along the normal direction of the electromagnetic wave incident surface of the transmission unit.
10. The transmissive structure according to claim 9, wherein the first part and the second part are respectively formed of different single materials.
11. The transmission structure according to claim 9, wherein the first part and the second part are formed of the same single material, and wherein the shape of the side of the first part away from the second part The shape of the side of the second part away from the first part is different.
12. The transmission structure according to claim 9, wherein the first part and/or the second part are formed by a composite of at least two different materials.
13. The transmission structure according to claim 12, wherein the first part and/or the second part are formed by at least two different materials arranged along the normal direction of the electromagnetic wave incident surface of the transmission unit.
14. The transmission structure according to claim 13, wherein the first part and the second part are both arranged in a layered structure.
15. The transmission structure according to claim 13 or 14, wherein the first part and the second part are both formed of a light-transmitting material.
16. The transmission structure according to claim 12, wherein the first part comprises a first base body, and the second part comprises a second base body; wherein the first base body is provided with a first inlay on the surface or inside. block, and/or a second insert block is arranged on the surface or inside of the second base body.
17. The transmission structure according to claim 16, wherein the first substrate and the second substrate are made of the same material, and the material includes a light-transmitting material.
18. The transmission structure according to claim 16 or 17, wherein the material of the first slug and the second slug includes any one of metal, dielectric or semiconductor.
19. An optical device, characterized by comprising the transmission structure according to any one of claims 1-18.
20. An optical system, characterized by comprising the optical device as claimed in claim 19 .

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