阅读说明：本技术 一种基于磁光介质与pt对称结构的多通道信号选择器及其使用方法 (Multi-channel signal selector based on magneto-optical medium and PT symmetrical structure and using method thereof ) 是由 余观夏 张晓萌 梅长彤 朱剑刚 赵莉 于 2019-09-27 设计创作，主要内容包括：本发明公开了一种基于磁光介质与PT对称结构的多通道信号选择器及其使用方法,属于微型光电子器件领域。该信号选择器包括介质基板和设置在其上的介质柱阵列,第一阵列和第三阵列对称地设置在介质基板的两端,第二阵列设置在第一阵列和第三阵列之间,第四阵列和第五阵列设置在第一阵列与第二阵列之间,第四阵列和第五阵列之间设有第一通道,第六阵列和第七阵列设置在第二阵列与第三阵列之间,第六阵列和第七阵列之间设有第二通道,第四阵列和第五阵列、第六阵列和第七阵列为宇称-时间对称结构。本发明可通过改变外加磁场方向控制电磁信号在两个通道进行选择性传输,或实现信号局域存储,具有传输稳定、方向可控、多通道非互易性传输的优点。(The invention discloses a multi-channel signal selector based on a magneto-optical medium and PT symmetrical structure and a using method thereof, belonging to the field of micro optoelectronic devices. The signal selector comprises a dielectric substrate and a dielectric column array arranged on the dielectric substrate, wherein a first array and a third array are symmetrically arranged at two ends of the dielectric substrate, a second array is arranged between the first array and the third array, a fourth array and a fifth array are arranged between the first array and the second array, a first channel is arranged between the fourth array and the fifth array, a sixth array and a seventh array are arranged between the second array and the third array, a second channel is arranged between the sixth array and the seventh array, and the fourth array, the fifth array, the sixth array and the seventh array are of an astronomical-time symmetric structure. The invention can control the electromagnetic signal to be selectively transmitted in the two channels by changing the direction of the external magnetic field or realize the local signal storage, and has the advantages of stable transmission, controllable direction and multi-channel nonreciprocal transmission.)

1. A multi-channel signal selector based on magneto-optical medium and PT symmetrical structure comprises a medium substrate and a medium column array arranged on the medium substrate, and is characterized in that the medium column array comprises a first array (1), a second array (2), a third array (3), a fourth array (4), a fifth array (5), a sixth array (6) and a seventh array (7), the first array (1) and the third array (3) are symmetrically arranged at two ends of the medium substrate, the second array (2) is arranged between the first array (1) and the third array (3), the fourth array (4) and the fifth array (5) are arranged between the first array (1) and the second array (2), a first channel (8) is arranged between the fourth array (4) and the fifth array (5), the sixth array (6) and the seventh array (7) are arranged between the second array (2) and the third array (3), a second channel (9) is arranged between the sixth array (6) and the seventh array (7), and the fourth array (4), the fifth array (5), the sixth array (6) and the seventh array (7) respectively form an astronomical-time symmetric structure.

2. A multi-channel signal selector according to claim 1, wherein said first (1), second (2) and third (3) arrays are of square lattice structure, and said fourth (4), fifth (5), sixth (6) and seventh (7) arrays are of single row structure.

3. A multi-channel signal selector based on a symmetric structure of a magneto-optical medium and PT according to claim 2, wherein the lattice constant of the tetragonal lattice structure is a, and the radius of the medium column is 0.125 a; the distance between the medium columns of the single-row structure is a, wherein the radius of the medium columns is 0.24 a; the width of the first channel (8) and the second channel (9) is 1.5 a.

4. The multi-channel signal selector based on a symmetric structure of a magneto-optical medium and PT of claim 3, wherein a is 100 nm.

5. A multi-channel signal selector based on a symmetric structure of a magneto-optical medium and PT according to claim 1, characterized in that the first array (1), the second array (2) and the third array (3) are each composed of magneto-photonic crystal cylinders.

6. A multi-channel signal selector based on symmetric structure of magneto-optical medium and PT as claimed in claim 5, wherein said magneto-optical crystal cylinder is ferrite yttrium iron garnet and has a relative dielectric constant of 15 ε under applied magnetic field₀，ε₀Is a vacuum dielectric constant, the relative permeability is in tensor form,

7. A multi-channel signal selector according to claim 1, wherein said fourth array (4) and said sixth array (6) are each comprised of a loss cylinder, and said fifth array (5) and said seventh array (7) are each comprised of a gain cylinder, said loss cylinder attenuating incident light and said gain cylinder increasing incident light gain.

8. The multi-channel signal selector based on symmetric structure of magneto-optical medium and PT of claim 7, wherein said loss cylinder and gain cylinder are made of InGaAsP quantum well semiconductor.

9. The multi-channel signal selector based on symmetric structure of magneto-optical medium and PT as claimed in claim 7 or 8, wherein the relative dielectric constant ε of said loss cylinder₂＝9ε₀+0.5i, the relative dielectric constant ε of said gain cylinder₂＝9ε₀0.5i, i is an imaginary unit, ε₀For the vacuum dielectric constant, the relative permeability of the loss and gain cylinders is 1.

10. A method of using a multi-channel signal selector based on symmetric structure of magneto-optical medium and PT as claimed in claims 1-9, characterized in that a positive or negative external magnetic field is applied to the first array (1), the second array (2) and the third array (3), respectively, and optical signals are applied to any point or four ports of the first channel (8) and the second channel (9).

Technical Field

The invention belongs to the field of micro optoelectronic devices, and particularly relates to a multi-channel signal selector based on a magneto-optical medium and PT symmetrical structure and a using method thereof.

Background

Photonic crystals are a synthetic material consisting of a variety of material periods or aperiodicity, and have attracted increasing attention due to their superior control of electromagnetic wave propagation. The magneto-optical photonic crystal is a special photonic crystal, the permeability or the dielectric constant of the magneto-optical photonic crystal is in a tensor form under the action of an external static magnetic field, the external magnetic field breaks time reversal symmetry to enable signals to be transmitted in a single direction, the single-direction transmission electromagnetic wave mode in the two-dimensional photonic crystal is a propagation state mode bound at the boundary of the special composite magneto-optical crystal, the generation of the single-direction transmission electromagnetic wave mode is similar to the quantum Hall effect under the action of a strong magnetic field, and therefore the single-direction transmission electromagnetic wave mode is called as the boundary state (edge states) of the photonic crystal. Meanwhile, the one-way propagation characteristic is very stable, and the transmission can be stably carried out without being influenced by obstacles. This phenomenon provides a new mechanism for designing new nonreciprocal optical devices, and accordingly, the developed optical devices with unidirectional transmission become a focus of research, such as new magneto-optical circulators, tunable unidirectional crossed waveguide distributors and magneto-optical switches.

On the other hand, in scientific development and the technical requirements of modern society, light local and slow light effects occupy very important positions, and the related range includes: optical information storage, enhanced optical signals, all-optical communications, and the like. To achieve optical localization, external mechanisms are typically employed, for example, using metallic materials to cause light reflection or utilizing photonic bandgaps. When the periodicity of the photonic crystal is complete, due to the band gap characteristics of the photonic crystal, the optical flow cannot be transmitted in the photonic crystal, and only by constructing defect state local light or controlling the transmission direction of the light, for example, a point defect is a part which destroys the periodic structure of the photonic crystal, the optical flow can be 'constrained' in the microcavity. The optical local area realized without defects has more important practical significance, the adjustable and easily realized local state is very important, and the two points are opposite in group velocity direction, so that energy flows move in opposite directions and are mutually counteracted to cause the optical flow velocity to become slow or generate a self-trapping phenomenon.

Meanwhile, in recent years, a space-Time (PT) symmetric optical waveguide system is discovered to have many unique optical properties, and has important application values in the aspects of photonic information processing and integrated optics.

However, there is a clear study on the basis of magneto-optical materials and the space-time (PT) structure, and particularly, the results of the study on the structure combining magneto-optical and PT structures in the design of two-dimensional photonic crystals and waveguides and the results of the study on the special optical characteristics thereof are very popular, and in modern microwave and optical communications, there are only few reports on the non-reciprocity characteristics of optical local or magnetic storage and unidirectional transmission in a micro-optoelectronic device, and it is urgently needed to design and develop a novel component with composite multiple functions.

Disclosure of Invention

In view of the above problems in the prior art, an object of the present invention is to provide a multi-channel signal selector based on PT symmetric structure and magneto-optical material, which fully utilizes the advantages of signal amplification of the magneto-optical medium and PT symmetric structure, and can realize unidirectional transmission with selectable and controllable optical local area and direction.

In order to solve the problems, the technical scheme adopted by the invention is as follows:

a multi-channel signal selector based on magneto-optical medium and PT symmetrical structure comprises a medium substrate and medium column arrays arranged on the medium substrate, wherein the medium column arrays comprise a first array, a second array, a third array, a fourth array, a fifth array, a sixth array and a seventh array, the first array and the third array are symmetrically arranged at two ends of the medium substrate, the second array is arranged between the first array and the third array, the fourth array and the fifth array are arranged between the first array and the second array, a first channel is arranged between the fourth array and the fifth array, the sixth array and the seventh array are arranged between the second array and the third array, a second channel is arranged between the sixth array and the seventh array, and the fourth array and the fifth array, The sixth array and the seventh array are respectively of an astronomical-time symmetric structure.

Further, the first array, the second array and the third array are of a square lattice structure, and the fourth array, the fifth array, the sixth array and the seventh array are of a single-row structure.

Furthermore, the lattice constant of the tetragonal lattice structure is a, wherein the radius of the dielectric column is 0.125 a; the lattice constant of the single-row structure is a, wherein the radius of the dielectric column is 0.24 a; the width of the first channel and the width of the second channel are both 1.5 a.

Further, a is 100 nm.

Further, the first array, the second array and the third array are all composed of magnetic photonic crystal cylinders.

Furthermore, the magneto-optic crystal cylinder is ferrite yttrium iron garnet, and the relative dielectric constant of the magneto-optic crystal cylinder is 15 epsilon under an applied magnetic field₀，ε₀Is a vacuum dielectric constant, the relative permeability is in tensor form,

μ₁＝14,μ₂i is an imaginary unit 12.4.

Furthermore, the fourth array and the sixth array are both composed of loss cylinders, the fifth array and the seventh array are both composed of gain cylinders, the loss cylinders generate attenuation effects on incident light, and the gain cylinders generate gain effects on the incident light.

Furthermore, the material of the loss cylinder and the gain cylinder is InGaAsP quantum well semiconductor.

Furthermore, the relative dielectric constant ε of the loss cylinder₂＝9ε₀+0.5i, the relative dielectric constant ε of said gain cylinder₂＝9ε₀0.5i, i is an imaginary unit, ε₀For the vacuum dielectric constant, the relative permeability of the loss and gain cylinders is 1.

A use method of the multi-channel signal selector based on the magneto-optical medium and PT symmetrical structure is characterized in that positive and negative external magnetic fields are applied to the first array, the second array and the third array respectively, and optical signals act on any one point or four channel ports in the first channel and the second channel.

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

(1) the single-row gain column and the single-row loss column form a PT symmetrical system, the nonreciprocal transmission property of the multichannel signal selector is based on the unidirectional boundary transmission property of magneto-optical materials and a PT symmetrical structure, the property is different from a common unilateral state and is a unilateral state in a nonreciprocal forbidden band caused by breaking time reversal symmetry, so that the transmission is very stable, and the unidirectional transmission property is not changed due to the existence of obstacles.

(2) The invention adopts a multi-channel structure combining magneto-optical medium materials and PT symmetrical structures, is different from the traditional non-reciprocal transmission device, corresponds to two completely different unidirectional boundary modes, can realize unidirectional transmission of electromagnetic signals in a specific frequency domain range, and has good backscattering inhibition effect and obvious non-reciprocal effect.

(3) The multichannel signal selector can realize the localization of optical signals and the storage of electromagnetic signals by externally adding magnetic fields in the same direction.

(4) The multi-channel signal selector can achieve selective multi-channel electromagnetic signal transmission by artificially changing the positive and negative of partial magnetic fields of the first array, the second array and the third array according to the unidirectional transmission characteristic of the ferrite columns under the action of an external magnetic field, can perform single-channel and double-channel signal transmission or signal storage according to actual needs, and is short in magnetic response time, sensitive in response and simple in operation.

(5) The power divider of the magneto-optical material belongs to a micro-optoelectronic device, has a size in the nanometer level, has an excellent effect and can realize integration.

Drawings

FIG. 1 is a schematic diagram of a multi-channel power divider according to the present invention;

in the figure: 1. a first array; 2. a second array; 3. a third array; 4. a fourth array; 5. a fifth array; 6. a sixth array; 7. a seventh array; 8. a first channel; 9. a second channel;

FIG. 2 shows an energy band structure obtained when a positive magnetic field is applied to the upper part and a negative magnetic field is applied to the lower part;

FIG. 3 shows an energy band structure obtained when a negative magnetic field is applied to the upper portion of the strip, and a positive magnetic field is applied to the upper portion of the strip;

FIG. 4 is a graph showing the calculated energy band diagram of the composite photonic crystal when the magnetic fields in the same direction are applied from top to bottom, corresponding to the distribution of the characteristic fields;

FIG. 5 shows the steady-state electric field Ez obtained in example 1;

FIG. 6 shows the steady-state electric field Ez obtained in example 2;

FIG. 7 shows the steady-state electric field Ez obtained in example 3;

FIG. 8 shows the steady-state electric field Ez obtained in example 4;

FIG. 9 shows the steady-state electric field Ez obtained in example 5;

FIG. 10 shows the steady-state electric field Ez obtained in example 6.

Detailed Description

The invention is further described with reference to specific examples.

As shown in fig. 1, the multi-channel signal selector based on a magneto-optical medium and PT symmetric structure comprises a rectangular medium substrate, a photonic crystal cylindrical array is arranged on the medium substrate, a first array 1 is arranged on one side of the medium substrate, a second array 2 is arranged in the middle of the medium substrate, a third array 3 is arranged on the other side of the medium substrate, a fourth array 4 and a fifth array 5 are arranged between the first array 1 and the second array 2, and a first channel 8 is arranged between the fourth array 4 and the fifth array 5; a sixth array 6 and a seventh array 7 are arranged between the second array 2 and the third array 3, a second channel 9 is arranged between the sixth array 6 and the seventh array 7, and the signal selector is arranged in an air environment.

The first array 1, the second array 2 and the third array 3 are tetragonal ferrite yttrium iron garnet columns (YIG), the lattice constant is 100nm, the radius of the column is 0.125a, and the relative dielectric constant is epsilon₁＝15ε₀，ε₀Is a vacuum dielectric constant, the relative permeability is in tensor form,

μ₁＝14,μ₂i is an imaginary unit 12.4.

The fourth array 4 and the sixth array 6 are formed by a row of loss cylinders and the fifth array 5 and the seventh array 7 are formed by a row of gain cylinders. The material of the loss cylinder and the gain cylinder is InGaAsP with a refractive index of 3, which is a quantum hydrazine semiconductor material, and the relative dielectric constant is lost when not irradiated by the pump light, i.e., with a positive imaginary part (loss cylinder), and is gained when irradiated by the pump light, i.e., with a negative imaginary part (gain cylinder). The loss cylinders have an attenuation effect on incident light, the gain cylinders have a gain effect on the incident light, and the adjacent row of loss cylinders and the row of gain cylinders form an astronomical-time (PT) symmetrical structure.

In the present invention, the relative dielectric constant ε of the gain cylinder₂＝9ε₀-0.5i, relative dielectric constant ε of loss cylinder₂＝9ε₀+0.5i, i is the imaginary unit, ε₀For the vacuum dielectric constant, the relative permeability of the loss and gain cylinders is 1. This structure forms two channels, a first channel 8 and a second channel 9, both of which have a width of 1.5 a.

The magneto-optical sub-crystals of the first array 1, the second array 2 and the third array 3 can be externally applied with magnetic fields in positive or negative directions, and point sources, namely optical signals, can act on any point or four channel ports in a channel.

When no magnetic field is applied, the ferrite has a magnetic permeability of mu₀When a 0.16T steady bias magnetic field acts, strong anisotropy of gyromagnetic force can be induced, so that the magnetic permeability of the magneto-optical YIG material is expressed as tensorFormula (II):

μ₁＝14,μ₂＝12.4。

the boundary mode of the two-dimensional photonic crystal can be obtained by a modified plane wave expansion method. The magnetic field component is eliminated by a Maxwell equation system to obtain:

in the equation

Using the bloch principle of periodic structures, the electric field components can be developed as follows:

in the above equation, k is a wave vector of the Brillouin wave in the first Brillouin zone, G is a lattice vector of the periodic structure inverted lattice space, and E (k + G) corresponds to an expansion coefficient of G. The elements in the permeability tensor can be expanded into the form of a fourier series:

in this equation:

wherein Au is the area of the Vigrener-Seitz protocell in the periodic structure. The calculation is continued to finally obtain the following equation:

the sum of an infinite number of reciprocal lattice vectors G' in the formula. The above equation is a characteristic value equation of the matrix, and when we determine a wave vector k first, one k corresponds to one matrix characteristic equation set. G and G 'both have N different values, and when G' is determined to be positive, a linear system of equations is obtained for solving the N G values, thereby transforming the problem into a problem for solving the N matrix eigenvalues. Therefore, for a given wave vector k, the energy band of the periodic structure can be obtained by solving the corresponding characteristic angular frequency, and the frequency corresponding to the boundary mode can be completely solved.

Then, we calculate the band structure according to the above method, first, we use the supercell with the external magnetic field of upper positive and lower negative, and the calculated band diagram is shown in fig. 2, and it can be seen that two single-side state dispersion curves appear, and one single-direction band represents the group velocity in one direction. The two dispersion curves have the same group velocity direction, which represents that two unidirectional boundary transmission modes occur, namely a surface wave constrained at the boundary of the magneto-optical photonic crystal, and the energy flow (or group velocity) of the surface wave only points to one direction. The structure can realize unidirectional transmission. The frequency of a certain point in a single-side state frequency domain range can be used for realizing the one-way transmission of electromagnetic signals, an external magnetic field can be controlled to realize the dynamic storage and transmission of optical signals, and the optical signal transmission device has the anti-interference performance of a one-way boundary state and can transmit stably through obstacles. After the directions of the external magnetic fields are exchanged, namely, the negative magnetic field is applied outside the upper part, and the energy band structures obtained by solving the external positive magnetic field of the lower part are completely opposite, two energy bands with completely opposite group velocities appear in fig. 3, which shows that the directions of the obtained unidirectional transmission are completely opposite when the directions of the external magnetic fields of the upper part and the lower part are exchanged. The transmission of the signal direction can be completely controlled by applying magnetic fields with different positive and negative directions. It is also noteworthy that the unique PT structure and magneto-optical photonic crystal combination results in two parallel unidirectional energy bands, indicating two unidirectional propagation modes corresponding to two completely different modes. One corresponding to the even mode propagating in the PT symmetric structure and one corresponding to the odd mode at the boundary of the magneto-optical crystal and the PT structure.

While the calculated band structure when we apply the magnetic field in the same direction (plus positive or minus direction magnetic field) is shown in fig. 4, since the structure is composed of magneto-optical material and space-time, special coupling and transmission modes may occur. Firstly, the ferrite of the upper part and the lower part is externally provided with external magnetic fields with the same positive direction and negative direction, and the relative dielectric constants of the gain column and the loss column are 9-0.5i and 9+0.5 i. The band structure calculated from the band theory is shown in fig. 2 and 3, and it can be seen that a very horizontal dispersion curve is located in the second forbidden band of the band structure. The horizontal energy band means that the group velocity is close to zero, and therefore the light transmission speed in the waveguide is close to zero, and the light can be localized and self-trapped as if it stops in the waveguide. The horizontal dispersion curve is very important, the Ez distribution when the characteristic frequency of the supercell is calculated according to the horizontal energy band can see that an electric field is concentrated at the boundary of a PT symmetrical system and a magneto-optical material ferrite medium column, and light with the horizontal energy band frequency can be transmitted in a waveguide at a group velocity close to zero, so that the horizontal dispersion curve is of great significance to slow optical waveguide and magnetic storage.