CN106249443A - Magneto-optic thin film magnetic surface Fast-wave direction controllable light diode - Google Patents

Abstract

The invention discloses a kind of magneto-optic thin film magnetic surface Fast-wave direction controllable light diode, it includes a light input end mouth, optical output port, magneto-optic thin film, background media and a control bias magnetic field；Described magneto-optic thin film is arranged in background media；Described magneto-optic thin film uses magneto-optic memory technique；Described optical diode and isolator are made up of magneto-optic memory technique and background media；The left end of described optical diode and isolator is light input end mouth or optical output port, and its right-hand member is optical output port or light input end mouth；Described magneto-optic memory technique is magnetic surface fast wave with the surface of background media；Control bias magnetic field it is provided with at described magneto-optic thin film.Present configuration is simple, it is simple to realize, and light transmissioning efficiency is high, and volume is little, it is simple to integrated, is suitably applied extensive light path integrated, is with a wide range of applications.

Description

Magneto-optical film magnetic surface fast wave direction controllable photodiode

Technical Field

The invention relates to a magneto-optical material, a magnetic surface wave and a photodiode, in particular to a fast wave direction controllable photodiode of a magneto-optical film magnetic surface.

Background

A photodiode and an isolator are optical devices that allow light to travel in only one direction, and are used to prevent unwanted optical feedback. The main element of conventional photodiodes and isolators is a faraday rotator, which employs the faraday effect (magneto-optical effect) as its operating principle. The traditional Faraday isolator consists of a polarizer, a Faraday rotator and an analyzer, and the device has a complex structure and is generally applied to free-space optical systems. For integrated optical circuits, integrated optical devices such as optical fibers or waveguides are non-polarization maintaining systems, which cause loss of polarization angle, and thus are not suitable for faraday isolators.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides the magneto-optical film magnetic surface fast wave direction controllable photodiode which is simple and effective in structure, high in light transmission efficiency, small in size and convenient to integrate.

The purpose of the invention is realized by the following technical scheme.

The magneto-optical material film waveguide magnetic surface fast wave direction controllable photodiode comprises an optical input port, an optical output port, a magneto-optical film, a background medium and a controllable bias magnetic field; the magneto-optical film is arranged in a background medium; the magneto-optical film is made of magneto-optical materials; the photodiode and the isolator are made of magneto-optical materials and background media; the left ends of the optical diode and the isolator are an optical input port or an optical output port, and the right ends of the optical diode and the isolator are the optical output port or the optical input port; the surfaces of the magneto-optical material and the background medium are magnetic surface fast waves; and a controllable bias magnetic field is arranged at the magneto-optical film.

The magnetic surface fast wave photodiode is formed by arranging a magneto-optical film in a background medium.

The optical diode is an optical waveguide formed by the interface of magneto-optical material and background medium and can transmit optical signals in one direction.

The interface between the magneto-optical film and the background medium is a straight waveguide structure; the straight waveguide is a TE working mode waveguide.

The magneto-optical material is magneto-optical glass or various rare earth element doped garnet, rare earth-transition metal alloy film and other materials.

The background medium material is a material with transparent working wave; the background medium is a common medium material, air or glass.

The bias magnetic field is generated by an electromagnet or provided by a permanent magnet, the current of the electromagnet is direction controllable current, and the permanent magnet can rotate.

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

1. Simple structure and convenient realization.

2. The light transmission efficiency is high.

3. Small volume and convenient integration.

Drawings

FIG. 1 is a diagram of a fast wave direction controllable photodiode on the magnetic surface of a magneto-optical film.

FIG. 1 (a): light input end 1, light output end 2, magneto-optical film 3, background medium 4 bias magnetic field(inner) bias magnetic field ⊙ H₀Thickness w of (external) magneto-optical film

In FIG. 1(b), light output end 1, light input end 2, magneto-optical film 3, background medium 4, bias magnetic field ⊙ H₀Thickness w of (external) magneto-optical film

FIG. 2 is a diagram of the working principle of the rightward one-way conduction of a fast-wave direction controllable photodiode on the magnetic surface of a magneto-optical film.

FIG. 3 is a schematic diagram of the leftward unidirectional conduction operation of a fast-wave direction controllable photodiode on the magnetic surface of a magneto-optical film.

FIG. 4 is a graph showing the forward and reverse transmission efficiency of a fast wave direction controllable photodiode on the magnetic surface of a magneto-optical material film as a function of the frequency of light waves.

FIG. 5 is a graph showing the forward and reverse transmission efficiency of a fast wave direction controllable photodiode on the magnetic surface of a magneto-optical material film as a function of the frequency of light waves.

FIG. 6 is a graph showing the forward and reverse transmission efficiency of a fast wave direction controllable photodiode on the magnetic surface of a magneto-optical material film as a function of the frequency of light waves.

Detailed Description

As shown in figure 1, the fast wave direction controllable photodiode of the magneto-optical material film magnetic surface comprises an optical input port 1, an optical output port 2, a magneto-optical film 3, a background medium 4, a first wave absorbing layer 5, a second wave absorbing layer 6 and a controllable bias magnetic field H₀The magnetic surface fast wave light diode is formed by arranging a magneto-optical material film 3 in a background medium 4The film 3 is made of magneto-optical material, namely a magneto-optical material film, the interface of the magneto-optical material film 3 and the background medium 4 is an area in which light energy is mainly concentrated, an optical waveguide formed by the interface of the magneto-optical material film 3 and the background medium 4 can transmit optical signals in a single direction, namely a photodiode, and the photodiode and the isolator are formed by the magneto-optical material and the background medium. The magneto-optical material is magneto-optical glass or various rare earth element doped garnet, rare earth-transition metal alloy film and other materials; the interface of the magneto-optical material film 3 and the background medium 4 is a straight waveguide structure, and the waveguide is a TE working mode waveguide; as shown in fig. 1(a), the left end of the photodiode and the isolator is an optical input port 1, and the right end thereof is an optical output port 2; as shown in fig. 1(b), the right end of the photodiode is an optical input port 2, and the left end thereof is an optical output port 1; the surfaces of the magneto-optical material film 3 and the background medium 4 are magnetic surface fast waves; the background dielectric material is a material transparent to working waves, and can also be a common dielectric material, air or glass. A bias magnetic field H is arranged at the magneto-optical material film 3₀I.e. bias magnetic field(iii) or bias magnetic field ⊙ H₀(external), bias magnetic field H₀Generated by an electromagnet whose direction of current flow is controllable or provided by a rotatable permanent magnet, in a direction that will determine the conduction direction of the diode, by controlling the direction of current flow to change the conduction direction of the photodiode, or by rotating the permanent magnet. Controlling the direction of an external magnetic field of the magneto-optical material to be vertical to the paper surface and to face inwards through the electromagnet, wherein the left ends of the photodiode and the isolator are a light input end 1, the right ends of the photodiode and the isolator are a light output end 2, and the diode is conducted from the port 1 to the port 2; when the direction of the external control magnetic field is perpendicular to the paper surface and faces outwards, the right end of the diode is an optical input end 2, the left end of the diode is an optical output end 1, and the optical diode is conducted from the port 2 to the port 1.

The surface magnetic wave generated at the magneto-optical material-medium interface is a phenomenon similar to metal Surface Plasmon Polariton (SPP). Under the action of bias static magnetic field, the magnetic conductivity of the magneto-optical material is in tensor form, and meanwhile, the effective refractive index of the magneto-optical material is a negative value within a certain optical band range. Thus, the surface of the magneto-optical material can generate a guided wave and has the property of propagating in one direction, called a magnetic surface wave (surface magnetically polarized wavelet, SMP).

The magneto-optical material film waveguide photodiode with the controllable magnetic surface fast wave direction is formed by arranging a magneto-optical material film 3 in a background medium background 4, unidirectional light transmission is carried out by utilizing the magnetic surface fast wave generated by a magneto-optical material-medium interface, and the conduction direction of the photodiode is controlled by utilizing an electromagnet with controllable current direction.

The technical scheme of the invention is based on the optical nonreciprocal property of the magneto-optical material and the unique conductive surface wave characteristic of the magneto-optical material-medium interface, and realizes the design of the optical diode and the isolator. The basic principle of the technical scheme is as follows:

the magneto-optical material is a material with magnetic anisotropy, and magnetic dipoles in the magneto-optical material are arranged in the same direction due to an external static magnetic field, so that a magnetic dipole moment is generated. The magnetic dipole moment will interact strongly with the optical signal, resulting in a non-reciprocal transmission of light. A bias magnetic field H in a direction perpendicular to the paper surface₀The permeability tensor of the magneto-optical material is:

$\[{\mathrm{\μ}}_1\]=\left(\begin{array}{ccc}{\mathrm{\μ}}_r& {\mathrm{i\μ}}_{\mathrm{\κ}}& 0\\ -{\mathrm{i\μ}}_{\mathrm{\κ}}& {\mathrm{\μ}}_r& 0\\ 0& 0& {\mathrm{\μ}}_0\end{array}\right),---\left(1\right)$

the elements of the permeability tensor are given by the following system of equations:

${\mathrm{\μ}}_r={\mathrm{\μ}}_0(1+\frac{{\mathrm{\ω}}_m({\mathrm{\ω}}_0-i\mathrm{\α}\mathrm{\ω})}{{({\mathrm{\ω}}_0-i\mathrm{\α}\mathrm{\ω})}^2-{\mathrm{\ω}}^2}),{\mathrm{\μ}}_{\mathrm{\κ}}={\mathrm{\μ}}_0\frac{{\mathrm{\ω}}_m\mathrm{\ω}}{{({\mathrm{\ω}}_0-i\mathrm{\α}\mathrm{\ω})}^2-{\mathrm{\ω}}^2},{\mathrm{\ω}}_0={\mathrm{\μ}}_0{\mathrm{\γH}}_0,{\mathrm{\ω}}_m={\mathrm{\μ}}_0{\mathrm{\γM}}_s,---\left(2\right)$

wherein, mu₀Is magnetic permeability in vacuum, gamma is gyromagnetic ratio, H₀For application of a magnetic field, M_sTo saturation magnetization, ω is the operating frequency and α is the loss factor, H if the direction of the bias field is changed to be perpendicular to the paper, then H₀And M_sThe sign will change.

The surface magnetic wave generated at the magneto-optical material-medium interface can be solved according to the permeability tensor of the magneto-optical material and the Maxwell equation set. The electric field and the magnetic field existing at the interface of the surface wave (TE wave) should have the following forms:

$E_i=\left(\begin{array}{c}{e}_{xi}\\ 0\\ 0\end{array}\right)e^{i(k_{z}z+k_{yi}y-\mathrm{\ω}t)},H_i=\left(\begin{array}{c}0\\ h_{yi}\\ h_{zi}\end{array}\right)e^{i(k_{z}z+k_{yi}y-\mathrm{\ω}t)}---\left(3\right)$

where i-1 represents the region of magneto-optical material and i-2 represents the region of the medium. Substituting maxwell's equations:

$\▿\×E_i=-j\frac{\∂E_{xi}}{\∂z}-k\frac{\∂E_{xi}}{\∂y}=-\frac{\∂B_i}{\∂t},\▿\×H_i=-\frac{\∂D_i}{\∂t},---\left(4\right)$

then, based on the constitutive relation and the boundary condition, the wave vector k of the magnetic surface wave can be obtained_zTranscendental equation of (a):

$\frac{{\mathrm{\μ}}_e}{{\mathrm{\μ}}_0}\sqrt{{\mathrm{\ω}}^2{\mathrm{\μ}}_0{\mathrm{\ϵ}}_0-k_z^2}+\sqrt{{\mathrm{\ω}}^2{\mathrm{\μ}}_e{\mathrm{\ϵ}}_1-k_z^2}-\frac{{\mathrm{j\μ}}_k}{{\mathrm{\μ}}_r}{k}_z=0,---\left(5\right)$

wherein,is the effective permeability of the magneto-optical material. The transcendental equation can be solved by numerical solution to finally obtain k_zThe value of (c). It can also be seen from the equation that since the equation contains μ_κk_zTherefore, the magnetic surface wave has nonreciprocity (unidirectional propagation). From the solution of the equation, it can be concluded that when the magnetic field is changed to the opposite direction, the conduction direction of the photodiode also changes to the opposite direction.

Therefore, a bias magnetic field is added at the magneto-optical material film, the direction of the magnetic field of the electromagnet is controlled by current, and common dielectric materials, air or glass are used as background materials, so that an effective photodiode is formed. As shown in FIG. 2, Yttrium Iron Garnet (YIG) was used as the magnetic anisotropic material, and the background medium 4 was air (n)₀1) the magnitude of the bias field of the magneto-optical film 3 is 900Oe, the dimension l of the magneto-optical film 3 is 50mm, and the thickness w is 22.5 mm. The operating frequency f of the device being determined by the dielectric constants of the magneto-optical material and the medium₁，₂And magnetic permeability [ mu ]₁]，μ₂The determined working frequency is 6GHz, and the YIG material loss coefficient α is 3 × 10^-4. The magnetic field added by the magneto-optical material is vertical to the paper surface and faces inwards, when light is input from the port 1, a magnetic surface wave with unidirectional forward transmission is generated on a magneto-optical material-medium interface, and finally the light is output from the port 2, namely the direction controllable photodiode is conducted towards the right in a unidirectional mode; when light is input from port 2, the light wave cannot be transmitted backward inside the device due to the non-reciprocity of the magnetic surface wave and thus cannot be output from port 1, and the light energy is blocked at port 2. The conduction direction of the photodiode is determined by the direction of the applied magnetic field, and when the direction of the magnetic field is changed, as shown in FIG. 3, Yttrium Iron Garnet (YIG) is used as the magnetic anisotropic material, and the background medium is air (n)₀1), the magnitude of the bias field of the magneto-optical film is 900Oe, the dimension length l of the magneto-optical film 3 is 50mm,its thickness w is 22.5mm, and its working frequency f is determined by the dielectric constants of magneto-optical material and medium₁，₂And magnetic permeability [ mu ]₁]，μ₂The determined working frequency is 6GHz, and the YIG material loss coefficient α is 3 × 10^-4. As shown, the bias field is directed out of the plane of the paper, and the diode conduction direction is reversed. When light is input from the port 1, the inside of the device cannot transmit reverse light waves due to the non-reciprocity of the device, the port 1 does not have any light output, and all light energy is blocked at the port 2; when light is input from the port 2, a magnetic surface wave can be generated inside the device and then output from the port 2, namely, the left one-way conduction of the direction controllable photodiode.

Three embodiments are provided below with the accompanying drawings, in the embodiments, Yttrium Iron Garnet (YIG) is used as a magnetic anisotropic material, a bias magnetic field is generated by an electromagnet with controllable current direction, the magnitude is 900Oe, the direction is to determine the conduction direction of the diode, the thickness w of the magneto-optical film, and the loss coefficient α of the YIG material is 3 × 10^-4The operating frequency f of the device being determined by the dielectric constants of the magneto-optical material and the medium₁，₂And magnetic permeability [ mu ]₁]，μ₂And (4) determining.

Example 1

Referring to fig. 1(a) and (b), the photodiode with controllable fast wave direction on magnetic surface is composed of a magneto-optical film 3 disposed in a background medium 4, the material of the background medium 4 is air (n)₀1) the thickness w of the magneto-optical film 3 is 5 mm. In the working frequency band, the direction of an external magnetic field of the magneto-optical material is controlled to be vertical to the paper surface and to the inside by the electromagnet current, and the photodiode is conducted from a port 1 to a port 2; conversely, the direction of the control magnetic field is perpendicular to the paper and outwards, the photodiode is from the port 2 toTerminal "1 is conductive. The forward and reverse transmission efficiency is the same for both cases. Referring to fig. 4, the operating frequency range of the photodiode and the isolator of the straight waveguide structure is 4.52GHz to 7.26 GHz. In the working frequency range, the photodiode and the isolator can reach the highest forward and reverse transmission isolation degree of 21.9586dB and the forward transmission insertion loss of 0.0146dB by considering the material loss.

Example 2

Referring to fig. 1, the photodiode with controllable fast wave direction on magnetic surface is formed by arranging a magneto-optical film in a background medium 4 made of air (n)₀1) the thickness w of the magneto-optical film 3 is 7 mm. In the working frequency band, the direction of an external magnetic field of the magneto-optical material is controlled to be vertical to the paper surface and to the inside by the electromagnet current, and the photodiode is conducted from a port 1 to a port 2; conversely, the control field direction is out of the plane of the paper, and the photodiode will conduct from port 2 to port 1. The forward and reverse transmission efficiency is the same for both cases. Referring to fig. 5, the operating frequency range of the photodiode and the isolator of the straight waveguide structure is 4.58GHz to 7.20 GHz. In the working frequency range, the photodiode and the isolator can reach the highest forward and reverse transmission isolation degree of 25.0863dB and the forward transmission insertion loss of 0.0146dB by considering the material loss.

Example 3

Referring to fig. 1, the photodiode with controllable magnetic surface fast wave direction is formed by arranging a magneto-optical film in a background medium, and the material of the background medium 4 is glass (n)₀1.5), the thickness w of the magneto-optical film 3 is 7 mm. In the working frequency band, the direction of an external magnetic field of the magneto-optical material is controlled to be vertical to the paper surface and to the inside by the electromagnet current, and the photodiode is conducted from a port 1 to a port 2; conversely, the control field direction is out of the plane of the paper, and the photodiode will conduct from port 2 to port 1. The forward and reverse transmission efficiency is the same for both cases. Referring to fig. 6, the operating frequency range of the photodiode and the isolator of the straight waveguide structure is 4.62GHz to 7.16 GHz. In the range of the operating frequency, the frequency of the frequency,considering the material loss, the photodiode and the isolator reach the highest isolation degree of 23.6151dB in forward and reverse transmission and the insertion loss of 0.0622dB in forward transmission.

The optical frequency range of the magnetic surface fast wave transmitted by the magneto-optical film waveguide, that is, the operating frequency range of the direction controllable photodiode can be obtained from the transmission efficiency curve diagrams of the magneto-optical film magnetic surface fast wave direction controllable photodiode with different parameters in fig. 4, fig. 5 and fig. 6. From the results, the inventive magneto-optical material film waveguide-based photodiode with controllable fast wave direction on the magnetic surface can effectively work.

The invention described above is subject to modifications both in the specific embodiments and in the field of application and should not be understood as being limited thereto.

Claims (8)

1. A magneto-optical film magnetic surface fast wave direction controllable photodiode is characterized in that: the device comprises an optical input port, an optical output port, a magneto-optical film, a background medium and a controllable bias magnetic field; the magneto-optical film is arranged in a background medium; the magneto-optical film is made of magneto-optical materials; the photodiode and the isolator are made of magneto-optical materials and background media; the left ends of the optical diode and the isolator are an optical input port or an optical output port, and the right ends of the optical diode and the isolator are the optical output port or the optical input port; the surfaces of the magneto-optical material and the background medium are magnetic surface fast waves; and a controllable bias magnetic field is arranged at the magneto-optical film.

2. A magneto-optical film magnetic surface fast wave direction controllable photodiode according to claim 1, wherein: the magnetic surface fast wave photodiode is formed by arranging a magneto-optical film in a background medium.

3. A magneto-optical film magnetic surface fast wave direction controllable photodiode according to claim 1, wherein: the optical diode is an optical waveguide formed by the interface of magneto-optical material and background medium and can transmit optical signals in one direction.

4. A magneto-optical film magnetic surface fast wave direction controllable photodiode according to claim 1, wherein: the interface between the magneto-optical film and the background medium is a straight waveguide structure; the straight waveguide is a TE working mode waveguide.

5. A magneto-optical film magnetic surface fast wave direction controllable photodiode according to claim 4, wherein: the magneto-optical material is magneto-optical glass or various rare earth element doped garnet, rare earth-transition metal alloy film and other materials.

6. A magneto-optical film magnetic surface fast wave direction controllable photodiode according to claim 1, wherein: the background medium material is a material which is transparent to working waves.

7. A magneto-optical film magnetic surface fast wave direction controllable photodiode according to claim 1, wherein: the background medium is a common medium material, air or glass.

8. A magneto-optical film magnetic surface fast wave direction controllable photodiode according to claim 1, wherein: the bias magnetic field is generated by an electromagnet or provided by a permanent magnet, the current of the electromagnet is direction controllable current, and the permanent magnet can rotate.