WO2017140144A1

WO2017140144A1 - Dual-way inverting optical clock signal generator on the basis of photonic crystal cross waveguide

Info

Publication number: WO2017140144A1
Application number: PCT/CN2016/106678
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: CN105572920A; CN105572920B

Abstract

A dual-way inverting clock signal generator on the basis of photonic crystal cross waveguide, comprising: a photonic crystal cross waveguide having a TE forbidden band; said generator further comprises: an input terminal (1), three output terminals (2, 3, 4), a background silicon dielectric rod (5), an isosceles right triangle defect dielectric rod (6), and a defect dielectric rod (7); said generator further comprises: an electromagnet (8) providing a bias magnetic field, and a square-wave electrical current source (10); the input terminal (1) is located at a left end of the photonic crystal cross waveguide, while the output terminals (2, 3, 4) are located at a lower end, a right end, and an upper end of the photonic crystal cross waveguide, respectively; the defect dielectric rod (7) is located at a central intersection of the cross waveguide; TE carrier light is inputted into the photonic crystal waveguide by means of the terminal (1), and then a dual-way phase-inverting optical clock signal is outputted by means of the terminal (2) and the terminal (4).

Description

Dual reversed-phase optical clock signal generator based on photonic crystal cross waveguide

Technical field

The present invention relates to a dual reverse phase optical clock signal generator, and more particularly to a photonic crystal cross waveguide dual reverse phase optical clock signal generator.

Background technique

The traditional two-way optical clock signal generator with adjustable duty cycle and mutual logic is applied by the principle of 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. Tiny devices can be fabricated based on photonic crystals, including dual inverted optical clock signal generators. The photonic crystal waveguide optical path of the dual inverting optical clock signal generator is typically constructed by introducing line defects into the photonic crystal. The optical clock is an important component of optical communication, optical logic devices, optical information processing systems, and optical computing. It has a wide range of applications. The compact optical clock generator is an important component of the integrated wide chip.

Summary of the invention

The object of the present invention is to overcome the deficiencies in the prior art and to provide a photonic crystal cross-waveguide dual-channel inverse optical clock signal generator with small structure, high efficiency and short range for easy integration.

The object of the invention is achieved by the following technical solution.

The invention is based on a photonic crystal cross waveguide dual-channel inverse optical clock signal generator, 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, a silicon dielectric column 5, an isosceles right triangle defect dielectric column 6 and a defect dielectric column 7, the generator further comprising an electromagnet (8) providing a bias magnetic field and a rectangular wave current source (10); The left end of the photonic crystal cross waveguide is an input end 1, and the output ends 2, 3, and 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 at a center intersection of the cross waveguide; Four isosceles right triangle defect dielectric columns 6 are respectively located at four corners of the cross waveguide intersection; the photonic crystal waveguide inputs TE light from port 1, and outputs two opposite phase optical clock signals from port 2 and port 4.

The generator further includes a wire 9; one end of the electromagnet 8 is connected to one end of a rectangular wave current source 10; the other end of the electromagnet 8 is connected to the other end of the rectangular wave current source 10 via a wire 9. The direction of the bias magnetic field provided by the electromagnet 8 changes periodically with time.

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 T-shaped 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 background dielectric column 5 at the corner of the T-shaped waveguide crosses an angle to form an isosceles right triangle shaped defect dielectric column.

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 isosceles right triangle defect media column 6 is a triangular column type.

The defect 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 square column.

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

(1) Small structure, fast time response, high light transmission efficiency, suitable for large-scale optical path integration;

(2) It is easy to integrate, and can realize the TE optical dual-channel reverse optical clock signal generator in a short-range and high-efficiency manner, Has great practical value;

(3) Applying the characteristics that the photonic crystal can be scaled proportionally, by differently changing the lattice constant, the generation of dual-inverted clock signals of 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 view showing the structure of a photonic crystal cross waveguide dual-channel inverse optical clock signal generator of 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 another schematic structural view of a photonic crystal cross-waveguide dual-channel inverse optical clock signal generator of the present invention.

In the figure: electromagnet 8 wire 9 rectangular wave current source 10

3 is a structural parameter distribution diagram of a photonic crystal cross waveguide dual-channel inverse optical clock signal generator of the present invention.

4 is a waveform diagram of an optical clock signal of a photonic crystal cross waveguide dual inverting optical clock signal generator of the present invention.

Figure 5 is a logical contrast diagram of the forbidden band frequency of the photonic crystal cross waveguide dual inverting optical clock signal generator of the first embodiment.

6 is a logical contrast diagram of the forbidden band frequency of the photonic crystal cross-waveguide dual-channel inverse optical clock signal generator in Embodiment 2.

7 is a band gap frequency of a photonic crystal cross waveguide dual-channel inverse optical clock signal generator in Embodiment 3. The logical contrast map of the rate.

Figure 8 is a schematic diagram showing the light field distribution of the photonic crystal cross waveguide dual-channel inverse optical clock signal generator of the present invention.

detailed description

As shown in FIG. 1, a schematic structural diagram of a photonic crystal cross waveguide dual-channel inverse optical clock signal generator (deleting a bias circuit and a bias coil) includes a photonic crystal cross waveguide having a TE forbidden band, and the generator Also included is an input terminal 1, three output terminals 2, 3, 4, a background silicon dielectric column 5, an isosceles right triangle shaped defect dielectric column 6 and a square defect dielectric column 7; the initial signal light of the device is incident from the left port 1, Port 2 outputs light waves, port 3 and port 4 isolate light waves; the left end of the photonic crystal cross waveguide is input terminal 1, ports 2, 3, and 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 port 1. TE light, and then output two optical clock signals with opposite phases from port 2 and port 4; the background silicon dielectric column 5 has a square shape, the optical axis direction is perpendicular to the paper, and the isosceles right triangle defect dielectric column 6 is a T-waveguide. The background medium column 5 at the corner of the intersection deletes an angle to form an isosceles right triangle defect medium column, and the isosceles right triangle defect medium column 6 is a triangular column type, and four isosceles right angle triangles The shaped defect dielectric columns 6 are respectively located at the four corners of the intersection of the cross waveguides, 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, and the defective dielectric column 7 is a ferrite square column, and its shape In the square shape, the optical axis direction 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; The magnetic permeability of the ferrite 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. 2 is a schematic structural view (including a bias circuit and a bias coil) of a dual-phase optical clock signal generator of a clear photonic crystal cross waveguide according to the present invention, the generator including an electromagnet 8 for providing a bias magnetic field. (electromagnet coil) and a rectangular wave current source (10); the generator further includes a wire 9 having one end connected to one end of a rectangular wave current source 10, The other end of the magnet 8 is connected to the other end of the rectangular wave current source 10 via a wire 9, which provides a periodic change in the direction of the bias magnetic field with time. The generator of the present invention adopts a Cartesian Cartesian coordinate system as shown in FIG. 1 and FIG. 2: the positive direction of the x-axis is horizontal to the right; the positive direction of the y-axis is vertically upward in the paper; the positive direction of the z-axis is perpendicular to the paper. Outward facing.

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

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. The waveguide 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 above cross-waveguides, 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 6) 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 magnetic anisotropy The material, the magnetic anisotropy of the ferrite is induced by the 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 applied microwave signal can be controlled, thereby realizing the photonic crystal cross waveguide dual reverse optical clock signal generator. Under the action of the bias magnetic field, the permeability tensor of ferrite exhibits asymmetry, in which the ferrite tensor permeability [μ] is:

The relevant parameters in the matrix element 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, parameters μ and k determine different ferrite materials, materials with this form of magnetic permeability tensor are called gyromagnetic, assuming that the direction of the bias is reversed, H ₀ and M _S will change the sign, So the direction of rotation will be reversed.

The bias magnetic field is generated by a bias electromagnet loaded with a bias current, which is a modulated signal, and the modulated signal is a time varying periodic signal.

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 a dual reverse phase optical clock signal generator is implemented.

The two-way reverse optical clock signal generator is generally realized by the following method: under the cyclically varying bias magnetic field, the angle required for the rotation of the light by the Faraday rotation effect is alternately output by two ports, that is, the output two channels are opposite in phase. Optical clock signal.

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 in the form 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 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 in the form 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. The TE optical signal has almost no output at the output ports 2 and 3. 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, the period T ₁ wherein the magnetic field is -H, 2 from the output port; T ₂ period of the magnetic field H, 4 from the output port. Optical clock signal duty ratio = time when signal is 1 / time when signal is 0 = T ₁ /T ₂ . Pulse rise time = time required for the edge of a rectangular pulse to rise from 0 to 90% of the maximum output power. The pulse rise time of this structure depends on the rate of change of the magnetic field.

By adjusting the ratio of the positive and negative values of the modulated signal, the duty cycle of the output clock signal can be adjusted, which is equal to the ratio of the time at which the modulated signal is positive to the time at which the modulated signal is negative.

Optical clock parameters:

(1) Pulse rise time = time required for the edge of the rectangular pulse to rise from 0 to 90% of the maximum output power, and the pulse rise time of the structure depends on the rate of change of the magnetic field.

(2) Clock frequency = frequency of change of magnetic field

(3) The logical 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: 10log (output power of port 4 when on / output power of port 4 when off) = 10log (P _open / P _off )

Isolation is defined as: the isolation = 10log (power input / output isolation port) = 10log (P _into / P _interval)

It can be seen from Fig. 6 that the logic contrast can reach 48 dB when the normalized light wave frequency ωa/2πc=0.4121.

Example 1

In this embodiment, the function of the dual-channel inverted optical clock signal generator at different wavelengths can be realized by a method of changing the lattice constant in a proportional manner without considering the dispersion or the variation of the material dispersion. 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, the logic contrast in the forbidden band optical wave frequency range is obtained by simulation, and the structure has a high logic contrast duty ratio adjustable and mutually logical two-way optical clock signal generator, thereby realizing two-way The function of the inverse optical clock signal generator.

Example 2

In this embodiment, the function of the dual-channel inverted optical clock signal generator at different wavelengths can be realized by a method of changing the lattice constant in a proportional manner without considering the dispersion or the variation of the material dispersion. 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, the logic contrast in the band frequency of the forbidden band is obtained by simulation, and the structure has a high logic contrast and a dual inverted optical clock signal generator function.

Example 3

In this embodiment, the function of the dual-channel inverted optical clock signal generator at different wavelengths can be realized by a method of changing the lattice constant in a proportional manner without considering the dispersion or the variation of the material dispersion. 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, the logic contrast in the forbidden band optical frequency range is obtained by simulation, which has the function of a high logic contrast, dual inverting optical clock signal generator.

As can be seen from Fig. 8, when the normalized light wave frequency ωa/2πc = 0.4121, it is calculated by the finite element software COMSOL to obtain a light field simulation map. It can be seen that the TE light is efficiently propagated to the port 2 and the port 4, respectively.

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 photonic crystal cross waveguide dual reverse optical clock signal generator, characterized in that it comprises a photonic crystal cross waveguide with TE forbidden band; the generator further comprises an input end (1) and three output ends (2, 3, 4), a background silicon dielectric column (5), an isosceles right triangle shaped defect dielectric column (6) and a defective dielectric column (7), the generator further comprising an electromagnet providing a bias magnetic field (8) And a rectangular wave current source (10); 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 at the intersection of the center of the cross waveguide; the four isosceles right triangle defect dielectric columns (6) are respectively located at four corners of the intersection of the cross waveguide; the photonic crystal waveguide is connected by the port (1) ) Input TE light, and then output two optical clock signals with opposite phases from port (2) and port (4).
The photonic crystal cross waveguide dual reverse optical clock signal generator according to claim 1, wherein said generator further comprises a wire (9); one end of said electromagnet (8) and a rectangular wave One end of the current source (10) is connected; the other end of the electromagnet (8) is connected to the other end of the rectangular wave current source (10) via a wire (9); the bias provided by the electromagnet (8) The direction of the magnetic field changes periodically with time.
The photonic crystal cross waveguide dual-channel inverse optical clock signal generator according to claim 1, wherein said photonic crystal is a two-dimensional square lattice photonic crystal.
The photonic crystal cross waveguide dual reverse phase optical clock signal generator 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 is silicon Or a medium having a refractive index greater than 2; The low refractive index medium is air or a medium having a refractive index of less than 1.4.
The two-way reversed-phase optical clock signal generator based on a photonic crystal cross waveguide according to claim 1, wherein said T-shaped waveguide is a photonic crystal in which a middle horizontal row and a middle vertical dielectric column are removed. structure.
The photonic crystal cross waveguide dual reverse optical clock signal generator according to claim 1, wherein the background dielectric column (5) at the corner of the T-shaped waveguide is removed to form an isosceles right triangle. Defective media column.
The photonic crystal cross waveguide dual inverting optical clock signal generator according to claim 1, wherein the background silicon dielectric column (5) has a square shape.
The photonic crystal cross waveguide dual inverting optical clock signal generator 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.
The photonic crystal cross waveguide dual-channel inverse optical clock signal generator according to claim 1, wherein the isosceles right-angled triangular defect dielectric column (6) is a triangular prism type.
The photonic crystal cross waveguide dual-channel inverse optical clock signal generator 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.