WO2018041186A1

WO2018041186A1 - Magnetic surface fast-mode arbitrary-angle unidirectional bent waveguide with low-loss magneto-optical gap

Info

Publication number: WO2018041186A1
Application number: PCT/CN2017/099823
Authority: WO
Inventors: 欧阳征标; 郑耀贤; 艾月霞
Original assignee: 深圳大学
Priority date: 2016-08-31
Filing date: 2017-08-31
Publication date: 2018-03-08
Also published as: CN106249352B; CN106249352A

Abstract

Disclosed is a magnetic surface fast-mode arbitrary-angle unidirectional bent waveguide with a low-loss magneto-optical gap, comprising an optical input port (1), an optical output port (2), magneto-optical material layers (3, 4), a medium layer (5) and two bias magnetic fields in opposite directions. The magneto-optical material layers (3, 4) and the medium layer (5) are a three-layer structure optical waveguide, wherein same is bent-shaped at an arbitrary angle. The two bias magnetic fields in opposite directions are arranged at the magneto-optical material layers (3, 4). In a gap between the magneto-optical material layers (3, 4) is the medium layer (5). The medium layer (5) is in the shape of a circular ring at a waveguide bend portion. The surfaces of the magneto-optical material layers (3, 4) and the medium layer (5) are provided with magnetic surface fast waves. The bent waveguide has a simple structure, is convenient to integrate, has a low loss, has a high transmission efficiency, and is applicable to large-scale optical path integration.

Description

Low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way curved waveguide

Technical field

The invention relates to a magneto-optical material, a magnetic surface wave, a unidirectional transmission and a curved waveguide, in particular to a low-loss magneto-optical magnetic surface fast mode arbitrary angle one-way cornering waveguide.

Background technique

A curved waveguide is an optical device used as a conversion optical path, which occupies an important position in an optical waveguide device. Bending in the optical waveguide is necessary due to the change in the direction of beam propagation in the optical waveguide, the displacement of the beam transmission axis, and the need to reduce the volume of the device. The bending of the waveguide causes a change in the optical characteristic distribution of the waveguide material in the direction of light transmission, so that the curved waveguide has a high loss. The field of turning waveguides has been extensively studied, and the curved turning type curved waveguide is the main content of this research. But even for this type of waveguide, the bending loss and transition loss that are present still severely restrict the transmission efficiency. In addition, structural defects and the like can also cause other losses to the waveguide.

Photodiodes and isolators are optics that only allow light to travel in one direction and are used to prevent unwanted light feedback. The main component of conventional photodiodes and isolators is the Faraday rotator, which applies the Faraday effect (magneto-optical effect) as its working principle. The traditional Faraday isolator consists of three polarizers, a Faraday rotator and an analyzer. This device is complex in structure and is usually used in free-space optical systems. For integrated optical paths, integrated optical devices such as fiber optics or waveguides are non-polarization-maintaining systems that cause loss of polarization angle and are therefore not suitable for use with pull-up isolators.

Summary of the invention

The object of the present invention is to overcome the deficiencies in the prior art and provide a low-loss magneto-optical magnetic surface fast mode arbitrary angle one-way with simple structure, low loss, high optical transmission efficiency, small volume and easy integration. Turn the waveguide.

In order to achieve the above object, the present invention adopts the following design:

The low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way bending waveguide of the invention comprises an optical input port 1, a light output port 2, a magneto-

optical material layer

3, 4, a dielectric layer 5 and two opposite directions. a magnetic field; the magneto-

optical material layers

3, 4 and the dielectric layer 5 are a three-layer structure optical waveguide, the three-layer structure is curved at an arbitrary angle, and two are disposed at the magneto-

optical material layers

3, 4. a bias magnetic field having opposite directions; a gap between the layers of magneto-

optical materials

3, 4 is a dielectric layer 5, port 1 of the unidirectional curved waveguide is an optical input port, and a right port 2 is a light output port; The layer 5 is in the shape of a ring in the curved portion of the waveguide; the surface of the magneto-

optical material

3, 4 and the surface of the dielectric layer 5 are magnetic surface fast waves.

The photodiode and the isolator are composed of magneto-

optical material layers

3, 4 and a dielectric layer 5.

The magneto-optical material is magneto-optical glass or various rare earth element-doped garnets and rare earth-transition metal alloy films.

The magneto-

optical material layers

3, 4 and the dielectric layer 5 are connected to the optical input port 1 and the light output port 2 by any angular bending.

The dielectric layer 5 is a vacuum, air, silicon dioxide, and a transparent plastic wave.

The three-layer structure is a flat structure.

The arbitrary angle curved shape is a 30 degree turn shape, a 45 degree turn shape, a 60 degree turn shape, a 90 degree turn shape, a 120 degree turn shape, a 135 degree turn shape, a 150 degree turn Shape, 180 degree turn shape.

The bias magnetic field is generated by an electromagnet or a permanent magnet.

The one-way cornering waveguide is composed of a magneto-optical gap waveguide; the working mode of the one-way cornering waveguide is a TE mode.

The invention is suitable for large-scale optical path integration and has broad application prospects. Compared with the prior art, it has the following positive effects.

1. The structure is simple and easy to implement.

2. Small size for easy integration.

3. Magnetic surface waves have immune characteristics to structural defects, have ultra-low loss and ultra-high transmission efficiency, and are widely used in the design of various optical waveguides.

DRAWINGS

1 is a structural view of a low-loss magneto-optical magnetic surface fast mode arbitrary angle one-way turning waveguide.

In the figure: optical input port 1 optical output port 2 first magneto-optical material layer 3 second magneto-optical material layer 4 dielectric layer 5 bias magnetic field ⊙H ₀ (outer) bias magnetic field ⊕H ₀ (inner) dielectric layer thickness w The radius of the inner arc of the ring r The radius of the outer arc of the ring is r+w

2 is a working principle diagram of a low-loss magneto-optical void magnetic surface fast mode unidirectional turning waveguide.

Fig. 3 is a graph showing a first embodiment of the forward-reverse transmission efficiency of the low-loss type magneto-optical gap unidirectional turning waveguide as a function of the optical frequency.

Fig. 4 is a graph showing a second embodiment of the forward and reverse transmission efficiency of the low loss type magneto-optical void unidirectional turning waveguide as a function of the light wave frequency.

Figure 5 shows the forward and reverse transmission efficiency of a low-loss magneto-optical void unidirectional bending waveguide with light waves. A graph of a third embodiment of frequency variation.

Fig. 6 is a graph showing a fourth embodiment of the forward-reverse transmission efficiency of the low-loss type magneto-optical void unidirectional turning waveguide as a function of the optical frequency.

detailed description

As shown in FIG. 1, the low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way turning waveguide of the present invention comprises an optical input port 1, an optical output port 2, a first magneto-optical material layer 3, and a second magnetic field. The optical material layer 4, a dielectric layer 5 and two opposite bias magnetic fields H ₀ ; the unidirectional turning waveguide is composed of a magneto-optical gap waveguide, and the unidirectional turning waveguide operates in a TE mode, and the first magneto-optical material layer 3 The second magneto-optical material layer 4 and the dielectric layer 5 are a three-layer optical waveguide. The optical waveguide can transmit optical signals in one direction, and is used as a photodiode and an isolator. The photodiode and the isolator are composed of a first magneto-optical material layer 3. The second magneto-optical material layer 4 and the dielectric layer 5 are formed. The three-layer structure is a flat waveguide structure, and the three-layer structure is curved at an arbitrary angle, and the shape bent at any angle is a circular arc shape (arc-shaped turning type curved waveguide), and the turning angle can be any between 0 degrees and 180 degrees. Angle, the bending angle of the unidirectional turning waveguide can also adopt an angle between 0 degrees and 180 degrees; several kinds of waveguide turning angles as shown in FIG. 1 include: 30 degrees, 45 degrees, 60 degrees, 90 degrees, 120 degrees. , 135 degrees, 150 degrees, 180 degrees. Figure 1 (a) one-way turning angle is 30 degrees, Figure 1 (b) one-way turning angle is 45 degrees, Figure 1 (c) one-way turning angle is 60 degrees, Figure 1 (d), (i) single The turning angle is 90 degrees, the one-way turning angle of Figure 1 (e) is 120 degrees, the one-way turning angle of Figure 1 (f) is 135 degrees, and the one-way turning angle of Figure 1 (g) is 150 degrees and Figure 1 (h) The one-way turning angle is 180 degrees. For example, when the turning angle is 45 degrees, it is one-eighth of a ring; when the turning angle is 90 degrees, it is a quarter ring; when the turning angle is 180 degrees, it is a half ring, etc. And so on. Since the device structure of the present invention satisfies the symmetry conservation, that is, its corresponding mirror structure can also work effectively, both of the structures of FIGS. 1(d) and (i) are mirror-symmetrical and have the same operational characteristics. The first magneto-optical material layer 3, the second magneto-optical material layer 4, and the dielectric layer are connected to the optical input port and the light output end by an arbitrary angle curved shape. The dielectric layer 5 is a region where the light energy is mainly concentrated, and the gap between the first magneto-optical material 3 and the second magneto-optical material 4 is the dielectric layer 5, and the dielectric layer 5 has a ring shape in the curved portion of the waveguide, and the inner arc of the ring The radius is r, the outer arc radius is r+w, the length of the curved portion depends on the turning angle; the dielectric layer 5 is vacuum, air, silicon dioxide (glass), and transparent plastic working wave. The first magneto-optical material layer 3, the second magneto-optical material layer 4 and the dielectric layer 5 constitute a photodiode and an isolator capable of unidirectionally transmitting optical signals, a first magneto-optical material layer 3, a second magneto-optical material layer 4 and a dielectric layer The surface of 5 is a magnetic surface fast wave. The magneto-optical material is magneto-optical glass or various rare earth-doped garnets and rare earth-transition metal alloy films. The first magneto-optical material layer 3 and the second magneto-optical material layer 4 are respectively provided with oppositely directed bias static magnetic fields H _{0 ,} that is, a bias magnetic field ⊙H ₀ (outer) and a bias magnetic field ⊕H ₀ (in), The bias magnetic field H ₀ is generated by an electromagnet or a permanent magnet. When the static magnetic field H ₀ to the drawing outwardly perpendicular magneto-optical material 3 is applied, the magneto-optical material 4 is applied perpendicular to the static magnetic field H ₀ in the paper facing, unidirectional turning port optical waveguide input port 1, port 2 Light output port.

The magnetic surface wave generated by the magneto-optical material-medium interface is a phenomenon similar to the metal surface plasmon (SPP). Under the action of the biased static magnetic field, the magneto-optical material has a magnetic permeability of tensor, and at the same time, its effective refractive index is negative in a certain optical band. Thus, the surface of the magneto-optical material is capable of producing a guided wave and has a property of unidirectional propagation, which is called a surface acoustic wave (Surface Magnetically Polarized Wave, SMP).

The low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way turning waveguide has a three-layer structure of a magneto-optical material-medium-magneto-optical material, and the magnetic surface fast wave generated by the magneto-optical material-medium interface is used for light One-way bending transmission.

The technical solution of the present invention is based on the optical non-reciprocity of the magneto-optical material and the unique conductive surface wave characteristic of the magneto-optical material-medium interface to realize the design of the unidirectional turning waveguide. The basic principles of this technical solution are as follows:

The magneto-optical material is a material having magnetic anisotropy, and the magnetic dipole inside the magneto-optical material is arranged in the same direction by the application of a static magnetic field, thereby generating a magnetic dipole moment. The magnetic dipole moment will interact strongly with the optical signal, which in turn produces a non-reciprocal transmission of light. The magnetic permeability tensor of the magneto-optical material is under the action of a bias magnetic field H ₀ oriented in the direction perpendicular to the vertical paper:

The matrix elements of the permeability tensor are given by the following equations:

Where μ ₀ is the magnetic permeability in vacuum, γ is the gyromagnetic ratio, H ₀ is the applied magnetic field, M _s is the saturation magnetization, ω is the operating frequency, and α is the loss coefficient. If the direction of the biasing magnetic field is changed to the vertical paper facing direction, H ₀ and M _s will change the sign.

The magnetic surface wave generated by the magneto-optical material-medium interface can be solved according to the magnetic permeability tensor of the magneto-optical material and Maxwell's equations. Satisfy surface waves (for TE waves) The electric and magnetic fields present in the surface should have the following form:

Where i=1 represents the magneto-optical material region and i=2 represents the dielectric region. Substituting Maxwell's equations:

According to the constitutive relation and the boundary conditions, the transcendental equation about the wave vector k _z of the magnetic surface wave can be obtained:

among them,

It is the effective permeability of magneto-optical materials. This transcendental equation can be solved by a numerical solution, and finally the value of k _z is obtained. It can also be seen from the equation that since the equation contains the term of μ _κ k _z , the surface acoustic wave has non-reciprocity (one-way propagation).

It can be seen that if a three-layer structure of magneto-optical material-medium-magneto-optical material is used, and a static magnetic field in the opposite direction is added at the first magneto-optical material layer 3 and the second magneto-optical material layer 4, an effective one-way is formed. waveguide. And due to the characteristics of the surface acoustic wave (SMP), the curved waveguide will theoretically have no loss due to the curved structure. As shown in Fig. 2, yttrium iron garnet (YIG) is used as the magnetic anisotropic material, the dielectric layer is air (n ₀ =1), the bias magnetic field is 900 Oe, and the thickness of the dielectric layer 5 is w=5 mm. The inner arc radius r=30mm, the operating frequency f of the device is determined by the dielectric constants ε ₁ , ε ₂ and the magnetic permeability [μ ₁ ], μ _{2 of} the magneto-optical material and the medium, and the operating frequency is f=6 GHz. The YIG material loss factor α = 3 × 10 ^-4 and the turning angle is 90°. The magnetic field at the first magneto-optical material layer 3 faces the vertical paper facing outward, and the magnetic field at the second magneto-optical material layer 4 is in the vertical paper facing direction, when the light is input from the port 1, simultaneously in the two magneto-optical materials-medium The interface generates a unidirectional forward-transferred magnetic surface wave, and finally outputs from port 2; when light is input from port 2, the light wave cannot be reversely transmitted inside the device due to the non-reciprocity of the surface acoustic wave, thereby failing to pass the port. 1 output, the light energy has been blocked at port 2. At the same time, it can be seen that the light wave can be well confined to the curved waveguide, and the loss value is very low.

The low loss type magneto-optical void magnetic surface fast mode arbitrary angle one-way turning waveguide of the device of the invention has three-layer structural characteristics of a magneto-optical material-medium-magneto-optical material, and its structural size and parameters, such as the inner arc radius of the ring r and the dielectric layer thickness w can be flexibly selected according to the working wavelength and actual needs. Changing the size has no major impact on device performance. Four embodiments are given below with reference to the accompanying drawings. In the embodiment, yttrium iron garnet (YIG) is used as the magnetic anisotropic material, the bias magnetic field size is 900 Oe, and the magnetic field direction at the first magneto-optical material layer 3 is The vertical paper faces outward, and the magnetic field direction at the second magneto-optical material layer 4 is in the vertical paper facing direction, the dielectric layer 5 is air (n ₀ =1), the thickness w=5 mm, and the radius of the inner arc of the ring is r = 30 mm, YIG material loss factor α = 3 × 10 ^-4 , the operating frequency f of the device is determined by the dielectric constants ε ₁ , ε ₂ and magnetic permeability [μ ₁ ], μ _{2 of} the magneto-optical material and the medium.

Example 1

Referring to Fig. 1(b), the one-way cornering waveguide is composed of a magneto-optical gap waveguide with a turning angle of 45 degrees. In the operating band, the light wave input from port 1 will generate a magnetic surface wave inside the device, which is then output from port 2 through the device; and the light wave input from port 2 will be blocked by the device and cannot be output from port 1. Referring to Figure 3, the operating frequency range of the unidirectional cornering waveguide is 5.12 GHz to 7.16 GHz. Consider material loss in the operating frequency range, one way The corner waveguide has a maximum forward and reverse transmission isolation of 23.6552 dB and a forward transmission insertion loss of 0.0194 dB.

Example 2

Referring to Figures 1(d) and (i), the unidirectional turning waveguide is composed of a magneto-optical gap waveguide having a turning angle of 90 degrees. In the operating band, the light wave input from port 1 will generate a magnetic surface wave inside the device, which is then output from port 2 through the device; and the light wave input from port 2 will be blocked by the device and cannot be output from port 1. Referring to Figure 4, the operating frequency range of the unidirectional cornering waveguide is 5.10 GHz to 7.22 GHz. In the operating frequency range, considering the material loss, the one-way cornering waveguide has a maximum forward-reverse transmission isolation of 25.8838 dB and a forward transmission insertion loss of 0.0112 dB.

Example 3

Referring to Fig. 1(f), the one-way cornering waveguide is composed of a magneto-optical gap waveguide with a turning angle of 135 degrees. In the operating band, the light wave input from port 1 will generate a magnetic surface wave inside the device, which is then output from port 2 through the device; and the light wave input from port 2 will be blocked by the device and cannot be output from port 1. Referring to Fig. 5, the operating frequency range of the unidirectional turning waveguide is 5.10 GHz to 7.18 GHz. In the operating frequency range, considering the material loss, the one-way cornering waveguide has a maximum forward-reverse transmission isolation of 23.6067 dB and a forward transmission insertion loss of 0.0120 dB.

Example 4

Referring to Fig. 1(h), the one-way cornering waveguide is composed of a magneto-optical gap waveguide with a turning angle of 180 degrees. In the operating band, the light wave input from port 1 will generate a magnetic surface wave inside the device, which is then output from port 2 through the device; and the light wave input from port 2 will be used by the device. Blocked, cannot be output from port 1. Referring to Figure 6, the unidirectional cornering waveguide has an operating frequency range of 5.00 GHz to 7.30 GHz. In the operating frequency range, considering the material loss, the one-way cornering waveguide has a maximum forward-reverse transmission isolation of 27.7469 dB and a forward transmission insertion loss of 0.0073 dB.

The transmission efficiency curve of the magneto-optical gap magnetic surface fast mode unidirectional turning waveguide with different turning angles of FIG. 3, FIG. 4, FIG. 5 and FIG. 6 can obtain the optical frequency range of the magnetic surface fast wave transmitted by the magneto-optical air-bending waveguide. That is, the operating frequency range of the unidirectional turning waveguide. It can be seen from the results that the low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way corner waveguide of the present invention can work effectively.

The invention described above is susceptible to modifications of the specific embodiments and applications, and should not be construed as limiting the invention.

Claims

A low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way turning waveguide, characterized in that it comprises an optical input port (1), a light output port (2), and a magneto-optical material layer (3, 4) a dielectric layer (5) and two opposite bias magnetic fields; the magneto-optical material layer (3, 4) and the dielectric layer (5) are a three-layer optical waveguide, the three-layer structure being of any angle a curved shape, two opposite bias magnetic fields are disposed at the magneto-optical material layer (3, 4); a gap between the magneto-optical material layers (3, 4) is a dielectric layer (5) The port (1) of the unidirectional turning waveguide is an optical input port, and the right port (2) is a light output port; the dielectric layer (5) is annular in a curved portion of the waveguide; the magneto-optical material layer (3) 4) and the surface of the dielectric layer (5) is a magnetic surface fast wave.
The low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way cornering waveguide according to claim 1, wherein the photodiode and the isolator are composed of a magneto-optical material layer (3, 4) and a dielectric layer (5). .
The low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way cornering waveguide according to claim 1, wherein the magneto-optical material is magneto-optical glass or various rare earth doped garnet and rare earth-transition Materials such as metal alloy films.
A low-loss magneto-optical-void magnetic surface fast mode arbitrary-angle unidirectional turning waveguide according to claim 1, wherein said magneto-optical material layer (3, 4) and dielectric layer (5) are bent at an arbitrary angle. Connected to the optical input port (1) and optical output port (2).
The low loss type magneto-optical gap magnetic surface fast mode arbitrary angle unidirectional turning waveguide according to claim 1, wherein the dielectric layer (5) is vacuum, air, silicon dioxide, and a working wave transparent plastic.
The low loss type magneto-optical gap magnetic surface fast mode arbitrary corner according to claim 1 A curved waveguide is characterized in that the three-layer structure is a flat structure.
The low-loss type magneto-optical gap magnetic surface fast mode arbitrary-angle one-way turning waveguide according to claim 1, wherein the arbitrary angle curved shape is a 30-degree curved shape, a 45-degree curved shape, a 60-degree curved shape, 90 degree turn shape, 120 degree turn shape, 135 degree turn shape, 150 degree turn shape and 180 degree turn shape.
The low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way corner waveguide according to claim 1, wherein the bias magnetic field is generated by an electromagnet or a permanent magnet.
The low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way corner waveguide according to claim 1, wherein the one-way corner waveguide is composed of a magneto-optical gap waveguide; and the working mode of the one-way corner waveguide For the TE mode.