WO2018041175A1

WO2018041175A1 - Magnetic surface fast-mode arbitrary-angle unidirectional bent waveguide with leakless low-loss magneto-optical thin film

Info

Publication number: WO2018041175A1
Application number: PCT/CN2017/099812
Authority: WO
Inventors: 欧阳征标; 郑耀贤
Original assignee: 深圳大学
Priority date: 2016-08-31
Filing date: 2017-08-31
Publication date: 2018-03-08
Also published as: CN106405729B; CN106405729A

Abstract

Disclosed is a magnetic surface fast-mode arbitrary-angle unidirectional bent waveguide with a leakless low-loss magneto-optical thin film, comprising an optical input end (1), an optical output end (2), a magneto-optical thin film (3), a background medium (4), two wave-absorbing layers (5, 6) and a bias magnetic field. The left end of the unidirectional bent waveguide is the optical input end (1), and the right end thereof is the optical output end (2). The magneto-optical thin film (3) is arranged in the background medium (4). The magneto-optical thin film (3) uses a magneto-optical material. The magneto-optical thin film (3) and the background medium (4) are bent-shaped at an arbitrary angle. The bias magnetic field is arranged at the magneto-optical thin film (3). A bent portion of the magneto-optical thin film (3) is in the shape of a circular ring. The surfaces of the magneto-optical material and the background medium (4) are provided with magnetic surface fast waves. The unidirectional bent waveguide has the advantages of a simple structure, small size, convenient integration, low loss and high transmission efficiency, is applicable to large-scale optical path integration, and can be broadly applied to the design of various optical waveguides.

Description

Non-leakage low loss type magneto-optical film magnetic surface fast mode arbitrary angle one-way curved waveguide

Technical field

The present invention relates to a magneto-optical material, a surface wave and a photodiode. More particularly, the present invention relates to a non-leakage low-loss magneto-optical thin film 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. Conventional Faraday isolators consist of a polarizer, a Faraday rotator, and an analyzer. This device is complex in structure and is commonly used in free-space optical systems. For integrated optical paths, integrated optical devices such as optical fibers or waveguides are non-polarization-maintaining systems that cause loss of polarization angle, thus Illegal Faraday isolator.

Summary of the invention

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

The object of the present invention is achieved by the following technical solutions.

The leakage-free low-loss type magneto-optical film magnetic surface fast mode arbitrary angle one-way bending waveguide comprises an optical input end 1, a light output end 2, a magneto-optical film 3, a background medium 4, and two absorbing

layers

5, 6 and a bias magnetic field; the left end of the unidirectional turning waveguide is a light input end 1, and the right end thereof is a light output end 2; the magneto-optical film 3 is disposed in the background medium 4; the magneto-optical film 3 is magnetic The magneto-optical film 3 and the background medium 4 are curved at an arbitrary angle; the magneto-optical film 3 is provided with a bias magnetic field; the curved portion of the magneto-optical film 3 is in the shape of a ring; the magneto-optical material At the surface of the background medium 4 is a magnetic surface fast wave.

The interface between the magneto-optical material and the background medium 4 constitutes an optical waveguide.

The magneto-optical film 3 and the background medium 4 are connected to the optical input port 1 and the light output port 2 by bending at an arbitrary angle.

The magneto-optical material film and the background medium 4 are structured as a flat waveguide structure.

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

The background medium 4 is a common dielectric material or air.

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

The absorbing

layers

5, 6 are the same or different absorbing materials; the absorbing materials are polyurethane, graphite, graphene, carbon black, carbon fiber epoxy resin mixture, graphite thermoplastic material mixture, boron fiber epoxy Resin mixture, graphite fiber epoxy resin mixture, epoxy polysulfide, silicone rubber, urethane, fluoroelastomer, polyether ether ketone, polyether sulfone, polyaryl sulfone or polyethyleneimine.

The absorbing

layers

5, 6 are each at a distance of 1/4 to 1/2 wavelength from the surface of the flat waveguide; the thickness of the absorbing

layers

5, 6 are each not less than 1/4 wavelength.

The bias magnetic field is generated by an electromagnet or a permanent magnet; the unidirectional turning waveguide is composed of a magneto-optical material thin film waveguide; and the unidirectional turning waveguide operates in a TE mode.

The invention is suitable for large-scale optical path integration and has wide 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

Fig. 1 is a structural view of a non-leakage low loss type magneto-optical thin film magnetic surface fast mode arbitrary angle one-way turning waveguide.

In the figure: light input end 1 light output end 2 magneto-optical film 3 (magneto-optical material film) background medium 4 first absorbing layer 5 second absorbing layer 6 bias magnetic field ⊙H ₀ thickness of (outer) magneto-optical film w The distance between the absorbing layer and the waveguide w ₁ The radius of the inner arc of the ring is r The radius of the outer arc of the ring r+w

2 is a working principle diagram of a magneto-optical thin film magnetic surface fast mode one-way turning waveguide.

Fig. 3 is a graph showing a first embodiment of the forward-reverse transmission efficiency of the magneto-optical film unidirectional turning waveguide as a function of the light wave frequency.

Fig. 4 is a graph showing a second embodiment of the forward-reverse transmission efficiency of the magneto-optical film unidirectional turning waveguide as a function of the optical frequency.

Fig. 5 is a graph showing a third embodiment of the forward-reverse transmission efficiency of the magneto-optical film unidirectional turning waveguide as a function of the optical wave frequency.

Fig. 6 is a graph showing a fourth embodiment of the forward-reverse transmission efficiency of the magneto-optical film unidirectional turning waveguide as a function of the light wave frequency.

detailed description

As shown in FIG. 1, the leakage-free ultra-low loss type magneto-optical film magnetic surface fast mode arbitrary angle one-way bending waveguide of the present invention comprises an optical input end 1, a light output end 2, a magneto-optical film 3, a background medium 4, The first absorbing layer 5, the second absorbing layer 6 and a bias magnetic field H ₀ , the unidirectional turning waveguide operates in a TE mode, and the unidirectional turning waveguide is composed of a magneto-optical material thin film waveguide, the magneto-optical film 3 and the background The interface of the medium 4 is a region where the light energy is mainly concentrated, the magneto-optical film 3 is disposed in the background medium 4, and the magneto-optical film 3 is a magneto-optical material, that is, a magneto-optical material film; the magneto-optical material is a magneto-optical glass or various rare earth elements. The material of the doped garnet and the rare earth-transition metal alloy film; the curved portion of the magneto-optical film 3 has a ring shape, the inner arc radius of the ring is r, and the outer arc radius is r+w. The turning angle may be an angle between 0 degrees and 180 degrees, and the bending angle of the unidirectional turning waveguide may also be: an angle between 0 degrees and 180 degrees; for example: 30 degrees, 45 degrees, 60 degrees, 90 degrees, 120 degrees Degrees, 135 degrees, 150 degrees and 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. The length of the curved portion depends on the angle of the bend. The magneto-optical material film 3 and the background medium 4 are curved at an arbitrary angle, and the shape bent at an arbitrary angle is a circular arc shape (arc-shaped turning type curved waveguide), for example, when the turning angle is 45 degrees, it is one-eighth of a circle. Ring; when the corner is 90 degrees, it is a quarter ring; when the corner is 180°, 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 surface of the magneto-optical material and the background medium 4 is a magnetic surface fast wave, and the magneto-optical material film 3 and the background medium 4 are structured as a straight waveguide structure; the interface between the magneto-optical material and the background medium 4 constitutes an optical waveguide, and the optical waveguide is unidirectional. Transmitting an optical signal for use as a photodiode or isolator; the magneto-optical material film 3 and the background medium 4 are connected to the optical input port 1 and the optical output port 2 by any angle bending; the background medium 4 is made of ordinary dielectric material or air; The wave layer 5 and the second absorbing layer 6 are the same or different absorbing materials, and the absorbing materials are polyurethane, graphite, graphene, carbon black, carbon fiber epoxy resin mixture, graphite thermoplastic material mixture, boron fiber epoxy Resin mixture, graphite fiber epoxy resin mixture, epoxy polysulfide, silicone rubber, urethane, fluoroelastomer, polyether ether ketone, polyether sulfone, polyaryl sulfone or polyethyleneimine; first absorbing layer 5. The distance between the second absorbing layer 6 and the surface of the straight waveguide is 1/4 to 1/2 wavelength, respectively, and the thickness of the first absorbing layer 5 and the second absorbing layer 6 are respectively not less than 1/4 wavelength. . The magneto-optical material film 3 is provided with a bias magnetic field ⊙H ₀ (outer), and the bias magnetic field is generated by an electromagnet or a permanent magnet. When the direction of the bias magnetic field is that the vertical paper faces outward or inward, the port 1 of the unidirectional turning waveguide is the light input end, and the port 2 is the light output end.

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 invention relates to a non-leakage low loss type magneto-optical film magnetic surface fast mode arbitrary angle one-way turning waveguide. The device is based on the non-reciprocity of magneto-optical materials, combined with the magneto-optical material-medium interface to produce surface wave characteristics and the excellent performance of the unidirectional turning waveguide. The magneto-optical material film is placed in a medium (air) background and combined with two absorbing layers, and the magnetic surface fast wave generated by the magneto-optical material-medium interface is used for unidirectional bending transmission of light, and the absorbing layer absorbs unnecessary waves. Eliminate optical path interference.

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. The electric and magnetic fields that satisfy the surface wave (which is a TE wave) at the interface 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 by adding a bias static magnetic field at the magneto-optical material film 3 and using a common dielectric material or air as the background material, an effective unidirectional waveguide will be formed. And due to the characteristics of the magnetic surface wave (SMP), the loss of the curved waveguide theoretically caused by the curved structure is very low. As shown in Fig. 2, yttrium iron garnet (YIG) is used as the magnetic anisotropic material, the background medium 4 is air (n ₀ =1), the bias magnetic field is 900 Oe, and the magneto-optical film thickness is w=5 mm. The distance between the absorbing layer 5 and the second absorbing layer 6 and the waveguide respectively is w ₁ = 5 mm, the radius of the inner arc of the ring is r = 30 mm, and the operating frequency f of the device is dielectric of the magneto-optical material and the medium. The constant ε ₁ , ε ₂ and magnetic permeability [μ ₁ ], determined by μ ₂ , the operating frequency is f = 6 GHz, the YIG material loss coefficient α = 3 × 10 ^-4 , and the turning angle is 90 degrees. The direction of the bias magnetic field is the vertical paper facing outward. When the light is input from the port 1, a magnetic surface wave which is unidirectionally forwardly transmitted is generated at the magneto-optical material-medium interface, and finally outputted from the port 2; when the light is input from the port 2, Due to the non-reciprocity of the surface acoustic wave, the light wave cannot be reversely transmitted inside the device, and thus cannot be output from the port 1. The light energy has all been blocked at port 2. At the same time, it can be seen that the light wave can be well confined to the magneto-optical film turning waveguide, and the loss value is very low.

The leakage-free low-loss magneto-optical film of the device of the invention has a magnetic surface fast mode arbitrary angle one-way turning waveguide which is arranged in a common dielectric material by a magneto-optical material, and its structural size and parameters, such as the inner arc radius r of the ring and the magnetic The thickness w of the light film can be flexibly selected according to the operating 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 is 900 Oe, the bias magnetic field is oriented perpendicular to the paper, and the background medium 4 For air (n ₀ =1), the thickness of the magneto-optical film is w=5 mm, and the distance between the first absorbing layer 5 and the second absorbing layer 6 and the waveguide is w ₁ =5 mm, respectively. Arc radius r=60mm, YIG material loss coefficient α=3×10 ^-4 , the operating frequency f of the device is the dielectric constant ε ₁ , ε ₂ and magnetic permeability [μ ₁ ], μ _{2 of the} magneto-optical material and the medium. Determined.

Example 1

Referring to Fig. 1(b), the unidirectional turning waveguide is composed of a magneto-optical film waveguide having a turning angle of 45°. 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 5.11 GHz to 7.38 GHz. In the operating frequency range, considering the material loss, the one-way cornering waveguide achieves a maximum forward-reverse transmission isolation of 28.446 dB and a forward transmission insertion loss of 0.0664 dB.

Example 2

Referring to Figures 1 (d) and (i), the unidirectional turning waveguide is composed of a magneto-optical film waveguide having a turning angle of 90°. 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 unidirectional cornering waveguide has an operating frequency range of 5.00 GHz to 7.40 GHz. In the operating frequency range, considering the material loss, the one-way cornering waveguide has a maximum forward-reverse transmission isolation of 31.993 dB and a forward transmission insertion loss of 0.0163 dB.

Example 3

Referring to Fig. 1(f), the unidirectional turning waveguide is composed of a magneto-optical film waveguide having a turning angle of 135°. 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 5, the operating frequency range of the unidirectional cornering waveguide is 5.06 GHz to 7.40 GHz. In the operating frequency range, considering the material loss, the one-way cornering waveguide has a maximum forward-reverse transmission isolation of 27.4473 dB and a forward transmission insertion loss of 0.0490 dB.

Example 4

Referring to Fig. 1(h), the unidirectional turning waveguide is composed of a magneto-optical film waveguide having a turning angle of 180°. 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 6, the unidirectional cornering waveguide has an operating frequency range of 5.00 GHz to 7.39 GHz. In the operating frequency range, considering the material loss, the unidirectional turning waveguide has a maximum forward-reverse transmission isolation of 35.753 dB and a forward transmission insertion loss of 0.0383 dB.

The transmission efficiency curve of the magneto-optical thin film 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 mode transmitted by the magneto-optical film turning 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 thin film magnetic surface fast mode arbitrary angle one-way turning 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 non-leakage low loss type magneto-optical film magnetic surface fast mode arbitrary angle one-way turning waveguide, characterized in that it comprises a light input end (1), a light output end (2), and a magneto-optical film (3) a background medium (4), two absorbing layers (5, 6) and a bias magnetic field; the left end of the unidirectional turning waveguide is an optical input end (1), and the right end thereof is a light output end (2); The magneto-optical film (3) is disposed in the background medium (4); the magneto-optical film (3) is made of a magneto-optical material; the magneto-optical film (3) and the background medium (4) are curved at an arbitrary angle; a magnetizing film (3) is provided with a bias magnetic field; the curved portion of the magneto-optical film (3) is in the shape of a ring; and the surface of the magneto-optical material and the background medium (4) is a magnetic surface fast wave .
The leak-free low-loss magneto-optical thin film magnetic surface fast mode arbitrary-angle unidirectional turning waveguide according to claim 1, wherein the interface between the magneto-optical material and the background medium (4) constitutes an optical waveguide.
A non-leakage low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way cornering waveguide according to claim 1, wherein said magneto-optical film (3) and said background medium are bent and lighted at an arbitrary angle The input port (1) is connected to the optical output port (2).
A non-leakage low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way cornering waveguide according to claim 1, wherein said magneto-optical film (3) and background medium (4) are structured as a straight waveguide structure. .
The non-leakage 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 garnets and rare earths. - Materials such as transition metal alloy films.
The leakage-free low-loss type magneto-optical film magnetic surface fast film according to claim 1 An unidirectional turning waveguide, characterized in that the background medium (4) is a common dielectric material or air.
The leak-free low-loss type magneto-optical gap magnetic surface fast mode arbitrary-angle one-way cornering waveguide according to claim 1, wherein the arbitrary angle curved shape is a 30-degree curved shape, a 45-degree curved shape, and a 60-degree curved shape. Shape, 90 degree turn shape, 120 degree turn shape, 135 degree turn shape, 150 degree turn shape, 180 degree turn shape.
A non-leakage low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way cornering waveguide according to claim 1, wherein said absorbing layer is the same or different absorbing materials; said absorbing material is Polyurethane, graphite, graphene, carbon black, carbon fiber epoxy resin mixture, graphite thermoplastic material mixture, boron fiber epoxy resin mixture, graphite fiber epoxy resin mixture, epoxy polysulfide, silicone rubber, urethane, Fluoroelastomer, polyetheretherketone, polyethersulfone, polyarylsulfone or polyethyleneimine.
A leak-free low-loss magneto-optical-void magnetic surface fast mode arbitrary-angle unidirectional turning waveguide according to claim 1, wherein said two absorbing layers (5, 6) are respectively associated with said straight waveguide The distance between the surfaces is 1/4 to 1/2 wavelength; the thickness of the two absorbing layers (5, 6) are each not less than 1/4 wavelength.
A non-leakage low loss type magneto-optical gap magnetic surface fast mode arbitrary angle one-way cornering waveguide according to claim 1, wherein said bias magnetic field is generated by an electromagnet or a permanent magnet; said one-way turning waveguide is The magneto-optical material is composed of a thin film waveguide; the working mode of the one-way curved waveguide is a TE mode.