WO2017140143A1

WO2017140143A1 - Photonic crystal cross-junction waveguide-based magnetically-controlled one-out-of-two optical path switch

Info

Publication number: WO2017140143A1
Application number: PCT/CN2016/106674
Authority: WO
Inventors: 欧阳征标; 吴昌义; 金鑫
Original assignee: 深圳大学
Priority date: 2016-02-15
Filing date: 2016-11-21
Publication date: 2017-08-24
Also published as: CN105572918B; CN105572918A

Abstract

A photonic crystal cross-junction waveguide-based magnetically-controlled one-out-of-two optical path switch, comprising one photonic crystal cross-junction waveguide having a TE band gap. The optical path switch also comprises one input end (1), three output ends (2, 3, and 4), a background silicon dielectric column (5), an isosceles right triangle defective dielectric rod (6), and a defective dielectric rod (7). The optical path switch also comprises one electromagnet (8) for providing a bias magnetic field. The left end of the photonic crystal cross-junction waveguide is the input end (1). The output ends (2, 3, and 4) respectively are arranged at the lower end, the right end, and the upper end of the photonic crystal cross-junction waveguide. The defective dielectric rod (7) is arranged at the center intersection of the cross-junction waveguide. A TE light is inputted to the photonic crystal waveguide via port (1); an output signal is outputted from port (2) or port (4). The optical path switch is structurally compact and convenient to assemble and allows short-range and efficient implementation of a TE carrier optical signal magnetically-controlled two-out-of-one optical path switch.

Description

Magnetron selective optical path switch based on photonic crystal cross waveguide

Technical field

The invention relates to a magnetically controlled two-selection optical path switch. More specifically, the present invention relates to a magnetron selective optical path switch based on a photonic crystal cross waveguide.

Background technique

The traditional magnetic control two-option optical switch uses geometric optics, so it is relatively large in size and cannot be used in optical path integration. The combination of magneto-optical materials and novel photonic crystals has led to the development of many photonic devices. The most important property is the gyromagnetic non-reciprocity of electromagnetic waves under bias magnetic fields, which makes magnetic photonic crystals not only have optical rotation characteristics, but also more Large transmission bandwidth and higher propagation efficiency. A tiny device based on a photonic crystal, such as a magnetron-selected optical path switch, whose photonic crystal cross-waveguide is constructed by introducing line defects. The optical switch is the most basic component of optical communication and optical computing, and has wide application value. The compact optical switch is the basic unit of the integrated optical circuit chip.

Summary of the invention

The object of the present invention is to overcome the deficiencies in the prior art and provide a photonic crystal magnetron selective optical path switch with small structure, high efficiency and short range for easy integration.

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

The invention is based on a magnetron selective optical path switch of a photonic crystal cross waveguide, comprising a photonic crystal cross waveguide with a TE forbidden band; the generator further comprises an input terminal 1, three output terminals 2, 3, 4, and a background a silicon dielectric column 5, an isosceles right triangle defect dielectric column 6 and a defect dielectric column 7, the optical path switch further comprising an electromagnet 8 for providing a bias magnetic field, the left end of the photonic crystal cross waveguide being an input end 1, The output ends 2, 34 are respectively located at the lower end, the right end, and the upper end of the photonic crystal cross waveguide; the defect The dielectric column 7 is located at the intersection of the center of the cross waveguide; the four isosceles right triangle defect dielectric columns 6 are respectively located at the four corners of the intersection of the cross waveguide; the photonic crystal waveguide is input with TE light from the port 1 and the output signal is from the port 2 Or port 4 output, ie input 1 is selectively connected to port 2 or port 4.

The modulator further includes a wire 9, a polarity controllable current source 10, and an electronic switch 11. One end of the electromagnet 8 is connected to one end of the controllable current source 10; the other end of the electromagnet 8 is connected to the other end of the polarity controllable current source 10 through a wire 9; the polarity controllable current The source 10 is connected to the electronic switch 11.

The photonic crystal is a two-dimensional square lattice photonic crystal.

The photonic crystal is composed of a high refractive index material and a low refractive index material; the high refractive index material is silicon or a medium having a refractive index greater than 2; and the low refractive index medium is air or a medium having a refractive index of less than 1.4.

The cross waveguide is a structure in which the middle one horizontal row and the middle one vertical dielectric column are removed in the photonic crystal.

The background dielectric column 5 at the cross corner of the cross waveguide deletes an angle to form an isosceles right triangle shaped defect dielectric column 6, which is a triangular column type.

The background silicon dielectric column 5 has a square shape.

The square silicon dielectric column is rotated 41 degrees counterclockwise in the z-axis direction of the dielectric column axis.

The defective dielectric column 7 is a ferrite square column having a square shape, the magnetic permeability of the ferrite square column is anisotropic, and is controlled by a bias magnetic field, and the bias magnetic field direction is along the ferrite. The axial direction of the body square.

The port 4 is a modulated output.

Compared with the prior art, the invention has the following advantages:

(1) The structure is small, the switching time response is fast, and the optical transmission efficiency is high, which is suitable for large-scale optical path integration;

(2) It is easy to integrate, and can realize the optical control of the TE optical signal by short-range and high-efficiency. Great practical value;

(3) Applying the characteristics that the photonic crystal can be scaled proportionally, by changing the lattice constant in equal proportions, the function of the magnetic switch of the different wavelengths can be realized;

(4) High contrast, high isolation, and a wide operating wavelength range, which can allow pulses with a certain spectral width, or Gaussian light, or light of different wavelengths, or multiple wavelengths of light to work simultaneously, Practical meaning.

DRAWINGS

1 is a schematic structural view of a magnetron selective optical path switch based on a photonic crystal cross waveguide according to the present invention.

In the figure: Input 1 Output 2 Output 3 Output 4 Background Silicon Media Column 5 Isosceles Right Triangle Defected Media Column 6 Defected Media Column 7

2 is a schematic view showing another structure of a magnetron selective optical path switch based on a photonic crystal cross waveguide according to the present invention.

In the figure: electromagnet 8 wire 9 polarity controllable current source 10 electronic switch 11

3 is a structural parameter distribution diagram of a magnetron selective optical path switch based on a photonic crystal cross waveguide according to the present invention.

4 is a switching waveform diagram of a magnetron selective optical path switch based on a photonic crystal cross waveguide of the present invention.

Fig. 5(a) is a switch contrast diagram of the forbidden band frequency of the magnetron selective optical path switch of the photonic crystal cross waveguide in the first embodiment.

Fig. 5 (b) is a switch isolation diagram of the forbidden band frequency of the magnetron selective optical path switch of the photonic crystal cross waveguide of the first embodiment.

Fig. 6(a) is a switch contrast diagram of the forbidden band frequency of the magnetron selective optical path switch of the photonic crystal cross waveguide of the second embodiment.

Fig. 6(b) is a diagram showing the switch isolation of the forbidden band frequency of the magnetron selective optical path switch of the photonic crystal cross waveguide in the second embodiment.

Fig. 7 (a) is a switch contrast diagram of the forbidden band frequency of the magnetron selective optical path switch of the photonic crystal cross waveguide in the third embodiment.

Fig. 7 (b) is a switch isolation diagram of the forbidden band frequency of the magnetron selective optical path switch of the photonic crystal cross waveguide in the third embodiment.

FIG. 8 is a schematic diagram showing the light field distribution of the magnetron selective optical path switch based on the photonic crystal cross waveguide of the present invention.

detailed description

As shown in FIG. 1, the present invention is based on a structural diagram of a magnetron selective optical path switch of a photonic crystal cross waveguide (deleting a bias circuit and a bias coil), and includes a photonic crystal cross waveguide having a TE forbidden band, the optical path The switch further includes an input terminal 1, three output terminals 2, 3, 4, a background silicon dielectric column 5, an isosceles right triangle defect dielectric column and a defective dielectric column 7; the initial signal light of the device is incident from the left port 1, the port 2 output light wave, port 3 and port 4 isolate the light wave; the left end of the photonic crystal cross waveguide is the input end 1, the output ports 2, 3, 4 are respectively located at the lower end, the right end and the upper end of the photonic crystal cross waveguide, and the photonic crystal waveguide is input by the port 1 TE light, switch 11 control signal is output from port 2 or port 4 respectively, that is, port 1 is selected to be connected to port 2 and port 4; background silicon dielectric column 5 is square in shape, optical axis direction is perpendicular to paper, and isosceles right angle The triangular defect dielectric column 6 is such that the background dielectric column 5 at the corner of the cross waveguide crosses an angle to form an isosceles right triangle defect dielectric column, the isosceles right triangle defect medium 6 is a triangular column type, and four isosceles right-angled triangular defect dielectric columns 6 are respectively located at four corners of the intersection of the cross waveguide, the optical axis direction is the same as the background dielectric column, and the defective dielectric column 7 is located at the intersection of the center of the cross waveguide, the defective dielectric column 7 is a ferrite square column, the shape of which is square, the magnetic permeability of the ferrite square column is anisotropic, and is controlled by the bias magnetic field, and the bias magnetic field direction is along the ferrite side. The axis direction of the column, the direction of the optical axis is perpendicular to the paper surface; the magnetic permeability of the ferrite square column is anisotropic, and is controlled by the bias magnetic field, and the bias magnetic field direction is along the axis direction of the ferrite square column. . As shown in FIG. 2, the present invention is based on a structure diagram of a magnetron selective optical path switch of a photonic crystal cross waveguide (including a bias circuit and a bias coil), and the optical path switch includes an electromagnet 8 (electromagnet) for providing a bias magnetic field. The coil circuit further includes a wire 9, a polarity controllable current source 10, and an electronic switch 11; one end of the electromagnet 8 is connected to one end of the polarity controllable current source 10, and the other end of the electromagnet 8 is passed through the wire 9 The other end of the polarity controllable current source 10 is connected; the polarity controllable current source 10 is connected to the electronic switch 11. The magnetic control two-selection optical path switch of the present invention adopts a Cartesian Cartesian coordinate system as shown in FIG. 1 and FIG. 3: the positive direction of the x-axis is horizontal to the right; the positive direction of the y-axis is vertical upward in the paper; the positive direction of the z-axis It is oriented perpendicular to the paper.

As shown in Figure 3, the relevant parameters of this device are:

d ₁ = a (lattice constant)

d ₂ =0.3a (square silicon column side length)

d ₃ =0.2817a (square defect media column side length)

d ₄ =0.3a (isoscelial right triangle defect column waist length)

d ₅ =1.2997a (the distance from the oblique side of the isosceles right triangle defect column to the center of the square defect column)

d ₆ =1.577a (waveguide width)

The photonic crystal of the invention has a square lattice, a lattice constant of a, a side length of the dielectric column of 0.3a, and a plane wave expansion method when the photonic crystal square silicon dielectric column rotates 41 degrees counterclockwise in the axial direction of the reference medium column (z axis). The TE forbidden band structure in the photonic crystal is obtained, and the photonic TE forbidden band is 0.3150 to 0.4548 (ωa/2πc), and the light wave of any frequency between them will be confined in the waveguide, and the square lattice dielectric column refers to the axis direction of the dielectric column (z The axis) rotated 41 degrees counterclockwise to obtain a larger and wider band gap.

The silicon dielectric waveguide used in the present invention needs to delete one row and one column of dielectric pillars to form a waveguide waveguide. Wave The guiding plane is perpendicular to the axis of the dielectric column in the photonic crystal. By introducing a ferrite square column (square defect column 7) at the intersection of the cross-wave center, the side length is 0.28a, and the four isosceles right-angled triangular defect dielectric columns 5 are inclined to the ferrite column (square) The distance of the axis of the defective dielectric column 7) is 1.2997a. The optical axis of the ferrite square column coincides with the optical axis direction of the background dielectric column.

The principles of the present invention are primarily explained for magneto-optical media. Ferrite is a material of magnetic anisotropy, and the magnetic anisotropy of ferrite is induced by an applied DC bias magnetic field. This magnetic field causes the magnetic dipoles in the ferrite to align in the same direction, resulting in a resultant magnetic dipole moment and precession of the magnetic dipole at a frequency controlled by the biasing magnetic field strength. By adjusting the bias magnetic field strength, the interaction with the external microwave signal can be controlled, thereby realizing the magnetron selective optical path switch of the photonic crystal cross waveguide. Under the action of the bias magnetic field, the permeability tensor of ferrite exhibits asymmetry, in which the ferrite tensor permeability [μ] is:

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

ω ₀ =μ ₀ γH ₀ (2)

ω _m =μ ₀ γM _s (3)

ω=2πf (4)

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, is the operating frequency, and p=k/μ is the normalized magnetization frequency, also called separation. factor, k, and the parameters determined different μ ferrite material having this form tensor permeability magnetic material is referred to spin, assuming the direction is reversed biased, then the M _S H ₀ or changes sign, So the direction of rotation will be reversed.

The optical axis of the ferrite square column coincides with the optical axis direction of the background dielectric column.

The bias magnetic field is generated by a bias electromagnet loaded with a bias current, which is a control signal; when the bias current is positive (negative), one optical path is strobed (closed), One light path is off (strobe).

By adjusting the magnitude of the bias magnetic field H to determine that H = H ₀ is met, light is output from port 4, and when H = -H ₀ , light is output from port 2. Thereby, the magnetic control is selected to be an optical path switch.

The magnetic control two-selection optical path switch is generally realized by combining the photonic band gap of the photonic crystal and the local characteristics of the photonic crystal with the gyromagnetic characteristics of the magneto-optical medium under the bias magnetic field, and using the Faraday rotation effect to make the light The angle required for rotation is output by either of the two ports, that is, port 1 is selected to be connected to port 2 and port 4. Therefore, the intensity of the light output from the port changes, and the function of the optical switch is realized.

Calculated by numerical scanning, d ₂ =0.3a, d ₃ =0.2817a, d ₅ =1.2997a, normalized light wave frequency f=0.4121, relative dielectric constant ε _r = 12.9, optical signal output maximum value from port 2 And output the minimum from port 4. When the direction of the biasing magnetic field changes, the signs of H ₀ and M _S change, so that the circular direction of the optical signal should change. Therefore, the optical signal outputs a maximum value from port 4 and a minimum output from port 2.

When the above defect is introduced in the silicon dielectric column array waveguide, the incident signal port is located at the position of the left port 1 shown in FIG. 1, and the port 1 is a TE optical signal. The optical signal propagates in the waveguide formed by the dielectric column array of the silicon dielectric column 5, after the TE optical signal reaches the defect position of the defective dielectric column 7, the TE optical signal will all pass, and finally the TE optical signal will be output at the output port 2 position; The TE optical signal has almost no output at the output ports 3 and 4. At the same time, the insertion loss in the waveguide is small. At this time, port 2 is in the on state, and ports 3 and 4 are in the off state. When the direction of the biasing magnetic field changes, the incident signal port is located at the position of the left port 1 shown in FIG. 1, which is a TE optical signal. The optical signal is in the column of the silicon dielectric column 5 After the waveguide formed by the array of pillars propagates, after the TE optical signal reaches the defect position of the defective dielectric column 7, the TE optical signal will all pass, and finally the TE optical signal will be output at the output port 4 position; the TE optical signal is at the output ports 2 and 3. There is almost no output in the location. At the same time, the insertion loss in the waveguide is small. At this time, port 4 is in the on state, and ports 2 and 3 are in the off state.

The selection of the lattice constant and the operating wavelength can be determined in the following manner. Through formula

And the normalized forbidden band frequency range of the square lattice silicon structure in the present invention

f _norm =0.3150～0.4548 (8)

Calculate the corresponding forbidden band wavelength range:

λ=2.1987a～3.1746a (9)

It can be seen that the λ value satisfying the wavelength range can be obtained by changing the value of the lattice constant a without changing the dispersion or the dispersion of the material. The operating wavelength can be adjusted by the lattice constant between the dielectric columns without regard to dispersion or negligible dispersion.

4, by controlling the voltage, to obtain the optical power output waveform, wherein 0 ~ t ₁ field period is -H, 2 from the output port; t> t ₁ is a period of the magnetic field H, 4 from the output port. The switch rise time T _r and the fall time T _f depend on the rate of change of the magnetic field.

Optical switch parameters:

(1) Switch rise time and fall time (the switch rise time and fall time of this structure are determined by the change speed of the magnetic field, so that a fast switching process can be obtained, generally only 1us switching time is required.) Referring to FIG.

(2) Switching contrast is defined as:

For port 2 conduction: 10log (output power of port 2 when turned on / output power of port 2 when disconnected) = 10log (P _open / P _off )

For port 4 conduction: 10 log (output power of port 4 at turn-on / output power of port 4 at _turn-off ) = 10 log (P _open / P _off ), refer to Figure 5 (a).

(3) Isolation is defined as:

Isolation = 10log (power input / output isolation port) = 10log (P _into / P _interval), with reference to FIG. 5 (b).

As can be seen from Fig. 5(a), when the normalized light wave frequency ωa/2πc = 0.4121, the switching contrast can reach 48 dB.

It can be seen from Fig. 5(b) that the isolation of ports 2 and 3 can reach 48dB and 46dB respectively, and its performance has obvious advantages compared with other optical switches.

Example 1

In this embodiment, the function of the magnetic control two-selection optical path switch of different wavelengths can be realized by a method of changing the lattice constant in equal proportion without considering the dispersion or the dispersion of the material dispersion is small. Let the parameter a=6.1772×10 ^-3 [m], d ₂ =0.3a, d ₃ =0.2817a, d ₅ =1.2997a, μ=9.6125, p=0.7792, normalized light wave frequency ωa/2πc=0.4121, The other parameters are unchanged, making it correspond to 20 GHz light waves. Referring to FIG. 5(a), the switch contrast in the forbidden band light wave frequency range is obtained by simulation; referring to FIG. 5(b), the switch isolation in the forbidden band light wave frequency range has high contrast and high isolation. The magnetic control selects an optical switch to realize the optical switch function.

Example 2

In this embodiment, the function of the magnetic control two-selection optical path switch of different wavelengths can be realized by a method of changing the lattice constant in equal proportion without considering the dispersion or the dispersion of the material dispersion is small. Let the parameter a=4.1181×10 ^-3 [m], d ₂ =0.3a, d ₃ =0.2817a, d ₅ =1.2997a, μ=9.6125, p=0.7792, normalized light wave frequency ωa/2πc=0.4121, The other parameters are unchanged, making it correspond to 30 GHz light waves. Referring to Fig. 6(a), the switching contrast in the forbidden band optical wave frequency range is obtained by simulation, and the switching isolation in the forbidden band optical wave frequency range is referred to Fig. 6(b). The structure has a high-contrast, high-isolation magnetically controlled two-selection optical path switch, thereby realizing the optical switching function.

Example 3

In this embodiment, the function of the magnetic control two-selection optical path switch of different wavelengths can be realized by a method of changing the lattice constant in equal proportion without considering the dispersion or the dispersion of the material dispersion is small. Let the parameter a=3.0886×10 ^-3 [m], d ₂ =0.3a, d ₃ =0.2817a, d ₅ =1.2997a, μ=9.6125, p=0.7792, normalized light wave frequency ωa/2πc=0.4121, The other parameters are unchanged, making it correspond to a 40 GHz light wave. Referring to Fig. 7(a), the switch contrast in the band gap frequency range is obtained by simulation. Referring to Fig. 7(b), the switch isolation in the band gap frequency range is shown in Fig. 7(a), 7(b). It can be seen that when the normalized light wave frequency ωa/2πc=0.4121, the light field simulation map is calculated by the finite element software COMSOL, as shown in FIG. It can be seen that the TE light is efficiently propagated to the port 2 and the port 4, respectively. The structure has a high contrast, high-interval, magnetically controlled two-choice optical path switch, thereby realizing the optical switching function.

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 magnetron selective optical path switch based on a photonic crystal cross waveguide, characterized in that it comprises a photonic crystal cross waveguide with a TE forbidden band; the optical path switch further comprises an input end (1) and three output ends ( 2, 3, 4), a background silicon dielectric column (5), an isosceles right triangle defect dielectric column (6) and a defective dielectric column (7), the optical path switch further comprising an electromagnet (8) for providing a bias magnetic field The left end of the photonic crystal cross waveguide is an input end (1), and the output ends (2, 3, 4) are respectively located at a lower end, a right end, and an upper end of the photonic crystal cross waveguide; the defective dielectric column (7) is located The cross-wave waveguide center intersection; the four isosceles right-angled triangular defect dielectric columns (6) are respectively located at four corners of the cross waveguide intersection; the photonic crystal waveguide is input with TE light from the port (1), and the output signal is from the port ( 2) Or port (4) output, ie input 1 is selectively connected to port 2 or port 4.
A photonic crystal cross waveguide based magnetically controlled two-select optical path switch according to claim 1, wherein said optical path switch further comprises a wire (9), a polarity controllable current source (10) and an electronic switch (11). One end of the electromagnet (8) is connected to one end of the polarity controllable current source (10); the other end of the electromagnet (8) is connected to the polarity controllable current source through the wire (9) (10) The other end of the circuit is connected; the polarity controllable current source (10) is connected to the electronic switch (11).
The photonic crystal cross waveguide-based magnetically controlled two-select optical path switch according to claim 1, wherein the photonic crystal is a two-dimensional square lattice photonic crystal.
A photonic crystal cross waveguide-based magnetron selective optical path switch according to claim 1, wherein said photonic crystal is composed of a high refractive index material and a low refractive index material; said high refractive index material being silicon or a medium having a refractive index greater than 2; the low refraction The rate medium is air or a medium having a refractive index of less than 1.4.
The photonic crystal cross waveguide-based magnetically controlled two-selection optical path switch according to claim 1, wherein the cross waveguide is a structure in which a middle one horizontal row and a middle vertical vertical dielectric column are removed from the photonic crystal.
The photonic crystal cross waveguide based magnetic control two-selection optical path switch according to claim 1, wherein the background dielectric column (5) at the cross corner of the cross waveguide deletes an angle to form an isosceles right triangle defect medium. The column, the isosceles right triangle defect dielectric column (6) is a triangular column type.
The photonic crystal cross waveguide based magnetron selective optical path switch according to claim 1, wherein the background silicon dielectric column (5) has a square shape.
A photonic crystal cross waveguide based magnetron selective optical path switch according to claim 7, wherein said square silicon dielectric column is rotated counterclockwise by 41 degrees in the z-axis direction of the dielectric column axis.
A photonic crystal cross waveguide based magnetically controlled two-selection optical path switch according to claim 1, wherein said defective dielectric column (7) is a ferrite square column having a square shape and said ferrite The magnetic permeability of the square column is anisotropic and controlled by the bias magnetic field, and the bias magnetic field direction is along the axis direction of the ferrite square column.
A photonic crystal cross waveguide based magnetically controlled two-select optical path switch according to claim 1, wherein said port (4) is a modulated output.