阅读说明：本技术 一种基于磁电耦合的完美圆偏振分离器 (Perfect circular polarization separator based on magnetoelectric coupling ) 是由 李汶佳 刘建龙 王东彬 史金辉 关春颖 朱正 李玉祥 吕博 徐文霞 于 2021-08-27 设计创作，主要内容包括：本发明提供了一种基于磁电耦合的完美圆偏振分离器,由陶瓷圆盘和中心空气孔构成,陶瓷圆盘和中心空气孔的旋转轴重合,中心空气孔不能贯穿陶瓷圆盘,目的是实现结构的磁电耦合,入射光为线偏振平面光,传播方向垂直于结构的旋转轴；所述的线偏振平面光的极化方向平行或垂直于结构的旋转轴。本发明采用了陶瓷材料作为基础材料,具备成本低廉的优势；平面光入射简化了以往实现完美圆偏振分离的复杂光源装置；陶瓷圆盘和中心空气孔复合结构的磁电耦合特性有益于激发一般结构很难激发的纵向偶极模式,进而构建横向自旋偶极矩,能够有效实现左旋和右旋圆偏振的完美分离。(The invention provides a perfect circular polarization separator based on magnetoelectric coupling, which consists of a ceramic disc and a central air hole, wherein the rotating shafts of the ceramic disc and the central air hole are superposed, and the central air hole cannot penetrate through the ceramic disc, so that the magnetoelectric coupling of a structure is realized, incident light is linearly polarized planar light, and the propagation direction is vertical to the rotating shaft of the structure; the polarization direction of the linear polarization plane light is parallel to or vertical to the rotating shaft of the structure. The ceramic material is used as a base material, so that the ceramic material has the advantage of low cost; the planar light incidence simplifies the prior complex light source device for realizing perfect circular polarization separation; the magnetoelectric coupling characteristic of the ceramic disc and central air hole composite structure is beneficial to exciting a longitudinal dipole mode which is difficult to excite by a common structure, so that a transverse spin dipole moment is constructed, and the perfect separation of left-handed circular polarization and right-handed circular polarization can be effectively realized.)

1. A perfect circular polarization separator based on magnetoelectric coupling is characterized by comprising a ceramic disc and a central air hole, wherein the rotating shafts of the ceramic disc and the central air hole are superposed, and the central air hole cannot penetrate through the ceramic disc, so that the magnetoelectric coupling of a structure is realized, incident light is linearly polarized planar light, and the propagation direction is vertical to the rotating shaft of the structure; the polarization direction of the linear polarization plane light is parallel to or vertical to the rotating shaft of the structure.

2. A perfect circular polarization separator based on magnetoelectric coupling according to claim 1, characterized in that the radius of said ceramic disc is 15 mm.

3. A perfect circular polarization separator based on magnetoelectric coupling according to claim 1, characterized in that the height of said ceramic disk is 12 mm.

4. A perfect circular polarization separator based on magnetoelectric coupling according to claim 1, characterized in that the radius of the central air hole is 4.5 mm.

5. A perfect circular polarization separator based on magnetoelectric coupling according to claim 1, characterized in that the height of said central air hole is 9.4 mm.

Technical Field

The invention relates to an orthogonal circular polarization state separation device for an input optical signal, in particular to a perfect circular polarization separator based on magnetoelectric coupling, which is mainly used for transversely and symmetrically separating and outputting the input optical signal according to a left-hand circular polarization state and a right-hand circular polarization state in a scattering far field.

Background

Light can be decomposed into two orthogonal left-and right-handed circular states of polarization. Perfect circular polarization separation refers to the phenomenon of transversely symmetrical separation of left-handed and right-handed circularly polarized light. The traditional single structure device needs to rely on focusing beams to realize perfect circular polarization separation, and the principle is that the longitudinal dipole mode of the structure is excited by the focusing beams, so that the transverse spin electric dipole moment is constructed. However, the method is difficult to implement and is not universal.

In recent years, the magnetoelectric coupling structure attracts attention by virtue of its unique physical characteristics. Magnetoelectric coupling is the cross-coupling between an electromagnetic field and an electromagnetic dipole moment, i.e. the coupling of an electric field to a magnetic dipole moment and the coupling of a magnetic field to an electric dipole moment. The magnetoelectric coupling characteristic of the structure can provide an additional degree of freedom for the regulation and control of a scattering far field, and different types of dipole modes can be effectively excited.

Therefore, the method is a feasible scheme for realizing perfect circular polarization separation by using structural magnetoelectric coupling to excite a proper longitudinal dipole mode and a proper transverse dipole mode and constructing transverse spin dipole moment, and has the advantages of simplicity and high efficiency.

Disclosure of Invention

The invention aims to provide a novel perfect circular polarization separator based on magnetoelectric coupling in order to overcome the problems that most of the prior single structures rely on focused beams and surface waves to realize perfect circular polarization separation and the realization method is complex. The adjustment of the magnetoelectric coupling characteristic of the structure can be realized by changing the frequency, the polarization state and the parameters of the structure of the linear polarization plane light incidence. Through reasonable magnetoelectric coupling characteristic of the adjusting structure, the transverse spinning dipole moment is constructed, the defect that the difficulty of realizing perfect circular polarization separation by a single structure is high can be overcome, and different types of transverse spinning dipole moments can be effectively constructed, so that simple and efficient left-handed and right-handed circular polarization transverse symmetric separation is realized.

The technical scheme of the invention is as follows:

the invention adopts the following technical scheme: the perfect circular polarization separator based on magnetoelectric coupling is composed of a ceramic disc and a central air hole, and rotating shafts of the ceramic disc and the central air hole are overlapped. The central air hole cannot penetrate through the ceramic disc in order to achieve the magnetoelectric coupling of the structure. The incident light is linearly polarized planar light, and the propagation direction is perpendicular to the rotation axis of the structure.

In two embodiments of the invention, the radius of the ceramic disc is 15 mm;

in two embodiments of the invention, the height of the ceramic disc is 12 mm;

in two embodiments of the invention, the radius of the central air hole is 4.5 mm;

in two embodiments of the invention, the height of the central air hole is 9.4 mm;

in embodiment 1 of the present invention, the polarization direction of the linearly polarized planar light is parallel to the rotation axis of the structure.

In embodiment 2 of the present invention, the polarization direction of the linearly polarized planar light is perpendicular to the rotation axis of the structure.

Compared with the prior art, the invention has the following beneficial effects:

the ceramic material is used as a base material, so that the ceramic material has the advantage of low cost; the planar light incidence simplifies the prior complex light source device for realizing perfect circular polarization separation; the magnetoelectric coupling characteristic of the ceramic disc and central air hole composite structure is beneficial to exciting a longitudinal dipole mode which is difficult to excite by a common structure, so that a transverse spin dipole moment is constructed, and the perfect separation of left-handed circular polarization and right-handed circular polarization can be effectively realized.

Drawings

Fig. 1 is a schematic structural diagram of a perfect circular polarization separator based on magnetoelectric coupling according to the present invention, wherein fig. 1(a) is a schematic structural diagram of sub-wavelength in two embodiments, and fig. 1(b) is a schematic structural diagram of a perfect circular polarization separator in scattering far field;

fig. 2 is a comparison graph of a magnetoelectric coupling structure and a non-magnetoelectric coupling structure and their far-field polarization as a function of incident light angle in two embodiments of the present invention, wherein (a) and (b) are schematic diagrams of the magnetoelectric coupling structure and the non-magnetoelectric coupling structure, and (c) and (d) are graphs of the far-field polarization as a function of incident light angle of the magnetoelectric coupling structure and the non-magnetoelectric coupling structure;

FIG. 3 shows the polarizability tensor and far-field average Stokes polarization parameter S of the magnetoelectric coupling structure in two embodiments of the present invention₃A graph of the change with the structure size and the frequency of incident light, wherein (a) and (b) are graphs of the change of the polarization rate tensor of the magnetoelectric coupling structure with the structure size and the frequency of incident light, and (c) and (d) are far-field average Stokes polarization parameters S₃Plot of variation with structure size and incident light frequency;

FIG. 4 is a scattering far field polarization and intensity profile for perfect circular polarization separation in a first embodiment of the present invention, wherein (a) is the far field polarization profile and (b) is the far field intensity profile in the x-y plane and the x-z plane;

FIG. 5 is a graph comparing the far field polarization of a magnetoelectric coupling structure and a non-magnetoelectric coupling structure in a first embodiment of the present invention, wherein (a) and (b) are polarization singular point distribution diagrams of a far field x >0 hemisphere and an x <0 hemisphere of the magnetoelectric coupling structure, and (c) and (d) are polarization singular point distribution diagrams of a far field x >0 hemisphere and an x <0 hemisphere of the non-magnetoelectric coupling structure;

FIG. 6 is a scattering far field polarization and intensity profile for perfect circular polarization separation in one embodiment of the present invention, where (a) is the polarization profile for the far field and (b) is the far field intensity profile for the x-y plane and the x-z plane.

Detailed Description

The following provides an example, and a circular polarization separator based on magnetoelectric coupling is further described. The method is a conventional method unless otherwise specified. The starting materials are commercially available from the open literature unless otherwise specified.

Example one

The structural schematic diagram of an air hole ceramic disk circular polarization separator based on magnetoelectric coupling is shown in fig. 1(a), the air hole ceramic disk based on magnetoelectric coupling is composed of a central air hole and a ceramic disk, and the polarization direction of incident linear polarization plane light is parallel to a rotating shaft of the structure. FIG. 1(b) is a schematic diagram of perfect circular polarization separation of the scattering far field, where the transverse spin dipole moment of the structure needs to be excited. The average Stokes polarization parameter S of the scattering hemisphere can be obtained by theoretical calculation by utilizing a dipole model₃The polarization separation effect of the scattering far field is measured.

FIG. 2(a) depicts a schematic diagram of a linearly polarized light incident magneto-electrically coupled circular polarization splitter with the incident light at an angle β to the z-axis. Radius R of ceramic disc₀And height H₀15mm and 12mm, respectively, radius r of the central air hole₀And height h₀4.5mm and 9.4mm, respectively, and the frequency of incident light is 2.55 GHz. With the change of the propagation direction of the incident linearly polarized light, the polarization separation effect of the scattering far field of the structure changes, and the change relationship is shown in fig. 2 (c). Polarization separation effect of scattering far field by mean stokes polarization parameter S of scattering hemisphere₃To indicate. It can be seen from fig. 2(c) that the polarization splitting effect is strongest when the incident angle is 90 °, i.e. the incident direction is perpendicular to the rotation axis of the structure. FIG. 2(b) depicts a schematic diagram of a linearly polarized light incident upon a non-magnetic electrical coupling structure, the incident light having an angle β with the z-axis. The non-magnetic electric coupling structure is composed of a solid ceramic disk with a radius R₀And height H₀15mm and 12mm, respectively, and the incident light frequency is 2.55 GHz. FIG. 2(d) shows the scattering far field polarization separation of the ceramic disk as a function of angle of incidence. The ceramic cylinder does not have the magnetoelectric coupling characteristic, and compared with a structure with the magnetoelectric coupling characteristic, the polarization separation effect is very weak, and the average polarization state of the scattering hemisphere changes along with the incidence angle according to the rule of a cosine function.

When the propagation direction of incident linearly polarized light is vertical to the rotating shaft of the structure, the polarizability of the magnetoelectric coupling structure is changed along with the change of the structure size and the incident light frequencyThe tensors are changed, and the changing relationship is shown in fig. 3(a) and 3(b), wherein,are the electric susceptibility tensors in the x and y directions,is the electric susceptibility tensor in the z-direction,are the magnetic polarizability tensors in the x-and y-directions,is the magnetic polarizability tensor in the z-direction, and γ represents the magnetoelectric coupling polarizability tensor. FIGS. 3(c) and 3(d) are average Stokes polarizations S for laterally opposite hemispheres₃The dotted line represents the theoretical calculation result and the solid line represents the simulation result along with the curves of the structural size and the incident light frequency. Average Stokes polarization parameter S₃The polarization state of the scattering far field is described. When the radius and the height of the ceramic disc are respectively 15mm and 12mm, the radius and the height of the central air hole are respectively 4.5mm and 9.4mm, and the incident light frequency is 2.55GHz, the average Stokes polarization parameter of the transversely opposite hemisphere of the scattering far field reaches the maximum value, and the maximum degree of polarization separation is obtained.

The polarization distribution of the scattering far field at the maximum of polarization separation in the example is shown in fig. 4(a), and the left-and right-handed circularly polarized light is perfectly polarization-separated in the scattering far field. The reason for achieving perfect polarization separation in this example is that a transverse spin electric dipole moment is constructed. Different from the principle of constructing the transverse spin electric dipole moment in the past, the scheme can construct the transverse spin electric dipole moment only by a simple incident light source from the magnetoelectric coupling characteristic of the structure. At this time, the intensity distribution of the scattering far field in the x-y plane and the x-z plane is as shown in fig. 4(b), and perfect polarization separation is accompanied by the intensity distribution of the scattering far field laterally.

While the perfect circular polarization state separation is accompanied by the polarization singular point movement, fig. 5(a) and 5(b) show the polarization singular point distribution diagrams of the x >0 hemisphere and the x <0 hemisphere of the scattering far field of the magnetoelectric coupling polarization separator in this example, and the color in the diagrams represents the phase of E · E, where E represents the electric field of the scattering far field. The white line segments in the figure represent the major axes of the polarizing ellipsoids, from whose distribution the position of the polarization singularities can be determined. The rotating arrows in the figure are the directions of phase gradients and are used for describing the positive and negative of the phase topological index, the counterclockwise rotation represents that the topological charge is positive, and the clockwise rotation represents that the topological charge is negative. It can be seen that the phase topological indices of the polarization singularities are of the same sign in the same hemisphere and the polarization topological indices are the same as 1/2, indicating that the polarization properties of the polarization singularities within the same hemisphere are the same when perfect circular polarization separation is achieved.

Fig. 5(c) and 5(d) show polarization singular point distribution diagrams of x >0 hemisphere and x <0 hemisphere of scattering far field of ceramic disk without magnetoelectric coupling property, in which colors represent phases of E · E, where E represents an electric field of scattering far field. The white line segments in the figure represent the major axes of the polarizing ellipsoids, from whose distribution the position of the polarization singularities can be determined. The rotating arrows in the figure are the directions of phase gradients and are used for describing the positive and negative of the phase topological index, the counterclockwise rotation represents that the topological charge is positive, and the clockwise rotation represents that the topological charge is negative. It can be seen that the phase topological indices of the polarization singularities in the same hemisphere are opposite in sign, and the polarization topological indices are the same as 1/2, indicating that the polarization properties of the polarization singularities in the same hemisphere are opposite when perfect polarization separation is not achieved.

Example two

Unlike the first embodiment, the polarization direction of the incident linearly polarized light is perpendicular to the rotation axis of the structure, which is aimed at achieving perfect circular polarization state separation for the excitation of the transverse spin magnetic dipole moment. Usually the method to achieve perfect circular polarization state separation can only start from the construction of transverse spin electric dipole moment. The magnetoelectric coupling characteristic of the structure in the scheme enables the principle of realizing perfect circular polarization separation to be more diverse.

The polarization profile of the scattering far field with the polarization direction of the incident linearly polarized light perpendicular to the axis of rotation of the structure in the example is shown in fig. 6(a), where the transverse spin magnetic dipole moment is excited. The intensity distributions of the scattering far field in the x-y plane and the x-z plane are shown in fig. 6(b), and perfect polarization separation is accompanied by an intensity distribution transverse to the scattering far field.