阅读说明：本技术 一种基于石墨烯和超表面结构的耦合装置及制备方法 (Coupling device based on graphene and super-surface structure and preparation method ) 是由 胡晓 肖希 张宇光 陈代高 李淼峰 王磊 冯朋 余少华 于 2019-08-12 设计创作，主要内容包括：本发明公开了一种耦合装置及方法,包括衬底、绝缘层、第一超表面结构、第二超表面结构和第三超表面结构、石墨烯层,第一超表面结构、第二超表面结构、第三超表面结构分别包括沿X方向周期性布置的第一单元、第二单元、第三单元；耦合装置的几何参数包括第一超表面结构、第二超表面结构、第三超表面结构各自的折射率、周期和厚度；几何参数被配置为入射光射向石墨烯层时,第三超表面结构和第一超表面结构分别将入射光透射和反射至第二超表面结构,使入射光在第二超表面结构内传播,入射光入射方向和入射光在第二超表面结构内的传播方向所在平面与XOY面垂直,入射方向与传播方向夹角为钝角。本发明具有大带宽、耦合效率高的优点。(The invention discloses a coupling device and a coupling method, which comprise a substrate, an insulating layer, a first super-surface structure, a second super-surface structure, a third super-surface structure and a graphene layer, wherein the first super-surface structure, the second super-surface structure and the third super-surface structure respectively comprise a first unit, a second unit and a third unit which are periodically arranged along the X direction; the geometrical parameters of the coupling device comprise the refractive index, the period and the thickness of the first super-surface structure, the second super-surface structure and the third super-surface structure respectively; the geometrical parameters are configured in such a way that when incident light irradiates the graphene layer, the third super-surface structure and the first super-surface structure respectively transmit and reflect the incident light to the second super-surface structure, so that the incident light is transmitted in the second super-surface structure, the incident light incident direction and the transmission direction of the incident light in the second super-surface structure are perpendicular to the XOY plane, and the included angle between the incident direction and the transmission direction is an obtuse angle. The invention has the advantages of large bandwidth and high coupling efficiency.)

1. A coupling device based on graphene and a super-surface structure, comprising:

a substrate (1) whose length, width and height directions are defined as X, Y, Z directions;

an insulating layer (2) formed on the substrate (1);

the insulation layer (2) is provided with a first super-surface structure (3), a second super-surface structure (4) and a third super-surface structure (5) which are arranged from bottom to top, the first super-surface structure (3) comprises first units (30) which are periodically arranged at intervals along the X direction, the second super-surface structure (4) comprises second units (40) which are periodically arranged at intervals along the X direction, and the third super-surface structure (5) comprises third units (50) which are periodically arranged at intervals along the X direction;

a graphene layer (6) formed on the upper surface of the insulating layer (2); at the same time, the user can select the desired position,

the geometrical parameters of the coupling device comprise the refractive index, the period and the thickness of the first super-surface structure (3), the refractive index, the period and the thickness of the second super-surface structure (4) and the refractive index, the period and the thickness of the third super-surface structure (5);

the geometric parameters are configured to: when incident light irradiates the graphene layer (6), the third super-surface structure (5) transmits the incident light to the second super-surface structure (4), the first super-surface structure (3) reflects the incident light to the second super-surface structure (4), the incident light is enabled to propagate in the second super-surface structure (4), the incident direction of the incident light and the propagation direction of the incident light in the second super-surface structure (4) are perpendicular to the XOY plane, and an included angle between the incident direction and the propagation direction is an obtuse angle.

2. The graphene and super-surface structure based coupling device of claim 1, wherein:

the geometrical parameters further comprise a spacing between the second super-surface structure (4) and the first super-surface structure (3) and a spacing between the second super-surface structure (4) and the third super-surface structure (5).

3. The graphene and super-surface structure based coupling device of claim 1, wherein:

the geometrical parameters further comprise a duty cycle of the first super-surface structure (3), a duty cycle of the second super-surface structure (4) and a duty cycle of the third super-surface structure (5).

4. The graphene and super-surface structure based coupling device of claim 1, wherein:

the refractive index of the third super-surface structure (5) is smaller than or equal to that of the second super-surface structure (4), and the refractive index of the third super-surface structure (5) is larger than that of the insulating layer (2).

5. The graphene and super-surface structure based coupling device according to claim 4, wherein: the refractive index of the third super-surface structure (5) is 1.8-4.2, the refractive index of the second super-surface structure (4) is 1.8-4.2, and the refractive index of the insulating layer (2) is 1.0-2.5.

6. The graphene and super-surface structure based coupling device of claim 1, wherein:

the thickness of the graphene layer (6) is 0.35-3.5 nm.

7. The graphene and super-surface structure based coupling device of claim 1, wherein:

the upper surface of the insulating layer (2) is recessed towards the third super-surface structure (5) and forms a thinning zone (7) for incident light.

8. The graphene and super-surface structure based coupling device of claim 1, wherein:

the insulating layer (2) comprises a lower insulating layer (21) and an upper insulating layer (20) formed on the lower insulating layer (21), the first super-surface structure (3) is positioned in the lower insulating layer (21), the second super-surface structure (4) and the third super-surface structure (5) are positioned in the upper insulating layer (20),

the lower insulating layer (21) is made of BCB glue, and the upper insulating layer (20) is made of insulating materials.

9. The graphene and super-surface structure based coupling device of claim 1, wherein:

the substrate (1) is made of metal material, and/or,

the first super-surface structure (3) is made of a metal material, and/or,

the second super-surface structure (4) is made of an insulating material, and/or,

the third super-surface structure (5) is made of an insulating material.

10. The method for preparing the coupling device based on the graphene and the super-surface structure according to claim 1, comprising the following steps:

-preparing a first super-surface structure (3) on the substrate (1);

-depositing a first layer on the first super-surface-structure (3);

-preparing a second super-surface structure (4) on said first layer;

-depositing a second layer on the second super-surface-structure (4);

-preparing a third super-surface structure (5) on the second layer;

depositing a third layer on the third super-surface structure (5), wherein the first layer, the second layer and the third layer jointly form the insulating layer (2);

forming a graphene layer (6) on the third layer, resulting in the coupling device.

Technical Field

The invention relates to the technical field of photonic integrated chips, in particular to a coupling device based on graphene and a super-surface structure and a preparation method thereof.

Background

In a photonic integrated chip, an optical coupling device is one of the most important integrated devices, which can couple external spatial light into the interior of the photonic chip. The optical coupler has two mainstream modes of horizontal coupling and vertical coupling, wherein the vertical coupling mode has the advantages of large alignment tolerance, convenience in test, simple preparation process and the like.

At present, a single-layer vertical coupling grating based on a diffraction principle can be designed according to different wavelengths of incident light, but the mode still has the problems of low coupling efficiency, sensitivity to the wavelength of the incident light and the like.

The multilayer grating structure can improve the coupling efficiency, but has a smaller working wavelength.

Therefore, it is necessary to provide a vertical coupler with a large bandwidth and high coupling efficiency.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a coupling device based on graphene and a super-surface structure, which has the advantages of large bandwidth and high coupling efficiency.

In order to achieve the above purposes, the technical scheme adopted by the invention is as follows: a graphene and super-surface structure based coupling device, comprising:

the length direction, the width direction and the height direction of the substrate are respectively defined as X, Y, Z directions;

an insulating layer formed on the substrate;

the first super-surface structure, the second super-surface structure and the third super-surface structure are positioned in the insulating layer and are arranged from bottom to top, the first super-surface structure comprises first units which are periodically arranged at intervals along the X direction, the second super-surface structure comprises second units which are periodically arranged at intervals along the X direction, and the third super-surface structure comprises third units which are periodically arranged at intervals along the X direction;

a graphene layer formed on an upper surface of the insulating layer; at the same time, the user can select the desired position,

the geometrical parameters of the coupling device comprise the refractive index, the period and the thickness of the first super-surface structure, the refractive index, the period and the thickness of the second super-surface structure and the refractive index, the period and the thickness of the third super-surface structure;

the geometric parameters are configured to: when incident light irradiates the graphene layer, the third super-surface structure transmits the incident light to the second super-surface structure, the first super-surface structure reflects the incident light to the second super-surface structure, the incident light is enabled to be transmitted in the second super-surface structure, the plane where the incident light incidence direction and the transmission direction of the incident light in the second super-surface structure are perpendicular to the XOY plane, and the included angle between the incident direction and the transmission direction is an obtuse angle.

Further, the geometrical parameters also include a spacing between the second super-surface structure and the first super-surface structure and a spacing between the second super-surface structure and the third super-surface structure.

Further, the geometric parameters further include a duty cycle of the first super-surface structure, a duty cycle of the second super-surface structure, and a duty cycle of the third super-surface structure.

Further, the refractive index of the third super-surface structure is smaller than or equal to that of the second super-surface structure, and the refractive index of the third super-surface structure is larger than that of the insulating layer.

Furthermore, the refractive index of the third super-surface structure is 1.8-4.2, the refractive index of the second super-surface structure is 1.8-4.2, and the refractive index of the insulating layer is 1.0-2.5.

Further, the thickness of the graphene layer is 0.35-3.5 nm.

Further, the upper surface of the insulating layer is recessed towards the third super-surface structure and forms a thinned region for incident light.

Further, the insulating layer comprises a lower insulating layer and an upper insulating layer formed on the lower insulating layer, the first super-surface structure is positioned in the lower insulating layer, the second super-surface structure and the third super-surface structure are positioned in the upper insulating layer,

the lower insulating layer is made of BCB glue, and the upper insulating layer is made of insulating materials.

Further, the substrate is made of metal materials, and/or,

the first super-surface structure is made of metal materials, and/or,

the second super-surface structure is made of an insulating material, and/or,

and the third super-surface structure is made of an insulating material.

The invention also provides a preparation method of the coupling device based on the graphene and the super-surface structure, which comprises the following steps:

preparing a first super-surface structure on the substrate;

depositing a first layer on the first super-surface structure;

preparing a second super-surface structure on the first layer;

depositing a second layer on the second super-surface structure;

preparing a third super-surface structure on the second layer;

depositing a third layer on the third super-surface structure, wherein the first layer, the second layer and the third layer form the insulating layer together;

and forming a graphene layer on the third layer to obtain the coupling device.

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

according to the invention, the refractive index, the period and the thickness of the second super-surface structure and the third super-surface structure are adjusted, the effective refractive index of a coupling region mode is reduced, the dispersion of the coupling region is reduced, and the graphene layer is laid on the surface, so that the coupling device is not sensitive to the wavelength of incident light by virtue of the ultra-wideband optical wavelength response (visible light to terahertz wave band), strong interaction with light, adjustable conductivity, ultra-fast carrier migration rate and other properties of the graphene layer, and meanwhile, the first super-surface structure has a reflection function and can improve the coupling efficiency of the incident light.

The graphene layer is arranged, so that the Fermi level of the graphene can be adjusted through an external pumping light source, the optical property of the graphene is changed, the mode effective refractive index of the coupling device can be adjusted, and the change can realize the adjustment of the coupling center wavelength.

Drawings

Fig. 1 is a schematic structural diagram of a coupling device based on graphene and a super-surface structure according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1;

FIG. 3 is a cross-sectional view taken along line B-B of FIG. 1;

fig. 4 is a cross-sectional view taken at C-C in fig. 1.

In the figure: 1. a substrate; 2. an insulating layer; 20. an upper insulating layer; 21. a lower insulating layer; 3. a first super-surface structure; 30. a first unit; 4. a second super-surface structure; 40. a second unit; 5. a third super-surface structure; 50. a third unit; 6. a graphene layer; 7. a thinned region.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples.

Referring to fig. 1 to 4, an embodiment of the present invention provides a coupling device based on graphene and a super-surface structure, where the coupling device includes a substrate 1, an insulating layer 2, a first super-surface structure 3, a second super-surface structure 4, a third super-surface structure 5, and a graphene layer 6;

defining the length direction, the width direction and the height direction of the substrate 1 as X, Y, Z directions respectively, and establishing a coordinate system;

an insulating layer 2 is formed on the substrate 1;

the first super-surface structure 3, the second super-surface structure 4 and the third super-surface structure 5 are positioned in the insulating layer 2 and are sequentially arranged from bottom to top, the first super-surface structure 3 comprises first units 30 periodically arranged at intervals along the X direction, the second super-surface structure 4 comprises second units 40 periodically arranged at intervals along the X direction, and the third super-surface structure 5 comprises third units 50 periodically arranged at intervals along the X direction;

the graphene layer 6 is formed on the upper surface of the insulating layer 2; at the same time, the user can select the desired position,

the geometrical parameters of the coupling means comprise the refractive index, the periodicity Λ of the first super-surface structure 3₁And a thickness h₁Refractive index, periodicity Λ of the second super-surface structure 4₂And a thickness h₂And the refractive index, the periodicity Λ of the third super-surface structure 5₃And a thickness h₃；

The geometric parameters are configured to: when incident light irradiates the graphene layer 6 by theta (the theta is an acute angle), the third super-surface structure 5 transmits the incident light to the second super-surface structure 4, the first super-surface structure 3 reflects the incident light to the second super-surface structure 4, the incident light is enabled to propagate in the second super-surface structure 4, the plane of the incident light and the propagation direction of the incident light in the second super-surface structure 4 is perpendicular to the XOY plane, and an included angle between the incident direction and the propagation direction is an obtuse angle.

The coupler 1dB bandwidth approximation equation is as follows:

since n is_eff(λ₀)-sinθ＞0，Using a lower mode effective index n_eff(lambda) and lower dispersion structureBandwidth delta lambda_1dBWill be added to make the coupler wavelength insensitive.

According to the invention, the refractive index, the period and the thickness of the second super-surface structure 4 and the third super-surface structure 5 are adjusted, the effective refractive index of a coupling region mode is reduced, the dispersion of the coupling region is reduced, the graphene layer 6 is laid on the surface, and the coupling device is insensitive to the wavelength of incident light by virtue of the ultra-wideband optical wavelength response (visible light to terahertz wave band), strong interaction with light, adjustable conductivity, ultra-fast carrier migration rate and other properties of the graphene layer 6, meanwhile, the first super-surface structure 3 has a reflection function, and the coupling efficiency of the incident light can be improved.

The graphene layer is arranged, so that the Fermi level of the graphene can be adjusted through an external pumping light source, the optical property of the graphene is changed, the mode effective refractive index of the coupling device can be adjusted, and the change can realize the adjustment of the coupling center wavelength.

The geometrical parameters of the coupling device also include the spacing between the second super-surface structure 4 and the first super-surface structure 3 in the Z-direction and the spacing between the second super-surface structure 4 and the third super-surface structure 5 in the Z-direction, in this embodiment, the spacing between the second super-surface structure 4 and the first super-surface structure 3 in the Z-direction is in the range of 100nm to 1.5 μm, and the spacing between the second super-surface structure 4 and the third super-surface structure 5 in the Z-direction is in the range of 200nm to 2 μm.

The geometrical parameters of the coupling device further comprise the duty cycle of the first super-surface structure 3, the duty cycle of the second super-surface structure 4 and the duty cycle of the third super-surface structure 5.

In the present embodiment, see fig. 2, the period Λ of the first super-surface structure 3₁In the range of 100nm ≦ Λ₁Less than or equal to 2 mu m and thickness h₁H is not more than 50nm (in Z direction)₁2 μm or less, the width of the first unit 30 is w₁(X-direction), the duty cycle of the first super-surface-structure 3 isAnd is

See fig. 3, the period Λ of the second super-surface-structure 4₂In the range of 200nm ≤ Λ₂Less than or equal to 5 mu m and thickness h₂H is within the range of 100nm or less (Z direction)₂Less than or equal to 1 μm, the width of the second unit 40 being w₂(X-direction), the duty cycle of the second super-surface structure 4 isAnd is

See fig. 4, the period Λ of the third super-surface-structure 5₃In the range of 200nm ≤ Λ₃Less than or equal to 4 mu m and thickness h₃H is within the range of 100nm or less (Z direction)₃Less than or equal to 600 mu m, the width of the third unit 50 is w₃(X-direction), the duty cycle of the third super-surface structure 5 isAnd is

Referring to fig. 3, in the present embodiment, the second unit 40 includes two segments with different widths, and the two segments are spaced apart from each other and filled with the insulating layer 2 therebetween. Referring to fig. 4, in the present embodiment, the third unit 50 includes two segments with different widths, and the two segments are spaced apart from each other and filled with the insulating layer 2 therebetween. The arrangement can also be carried out, and the three parameters of the width of two segments and the interval between the two segments are increased, so that the dimension of the design is increased, and the structural performance is improved.

In this embodiment, Λ₂Is greater than lambda₁And Λ₃。

Referring to FIG. 2, the refractive index of the third super-surface structure 5 is 1.8-4.2, the refractive index of the second super-surface structure 4 is 1.8-4.2, and the refractive index of the insulating layer 2 is 1.0-2.5. The refractive index of the third super-surface structure 5 is less than or equal to the refractive index of the second super-surface structure 4, and the refractive index of the third super-surface structure 5 is greater than the refractive index of the insulating layer 2.

As shown in FIG. 2, the thickness of the graphene layer 6 is 0.35-3.5 nm.

The upper surface of the insulating layer 2 is sunken towards the third super surface structure 5 and forms a thinning area 7 for incident light incidence, the distance range between the graphene layer 6 at the thinning area 7 and the third super surface structure 5 in the Z direction is 20 nm-3 mu m, and the setting of the thinning area 7 is beneficial to the graphene layer to be close to the third super surface structure 5, so that the graphene characteristic can be exerted more.

Referring to fig. 1, the insulating layer 2 includes a lower insulating layer 21 and an upper insulating layer 20 formed on the lower insulating layer 21, the first super-surface structure 3 is located in the lower insulating layer 21, the second super-surface structure 4 and the third super-surface structure 5 are located in the upper insulating layer 20, the lower insulating layer 21 is made of BCB glue, the upper insulating layer 20 is made of an insulating material, and refractive indexes of the lower insulating layer 21 and the upper insulating layer 20 are substantially equal.

The substrate 1 is made of a metal material, the first super-surface structure 3 is made of a metal material, the second super-surface structure 4 is made of an insulating material, and the third super-surface structure 5 is made of an insulating material. The metal material adopts at least one of gold, silver, aluminum and copper; the insulating material is at least one of silicon, silicon dioxide, silicon nitride, aluminum nitride, and gallium nitride.

The invention also provides a preparation method of the coupling device based on the graphene and the super-surface structure, which comprises the following steps:

s1: preparing a first super-surface structure 3 on a substrate 1;

s2: depositing a first layer on the first super-surface structure 3;

s3: preparing a second super-surface structure 4 on the first layer;

s4: depositing a second layer on the second super-surface structure 4;

s5: preparing a third super-surface structure 5 on the second layer;

s6: depositing a third layer on the third super-surface structure 5, wherein the first layer, the second layer and the third layer form an insulating layer 2 together;

s7: a graphene layer 6 is formed on the third layer, resulting in a coupling device.

The present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements are also considered to be within the scope of the present invention. Those not described in detail in this specification are within the skill of the art.