阅读说明：本技术 波导结构、光器件及波导结构的制作方法 (Waveguide structure, optical device and manufacturing method of waveguide structure ) 是由 胡晓 肖希 王磊 张宇光 陈代高 李淼峰 于 2019-08-09 设计创作，主要内容包括：本发明实施例公开了一种波导结构、光器件及波导结构的制作方法,所述波导结构包括：第一电介质层；芯层,堆叠在第一电介质层上,芯层的折射率大于第一电介质层的折射率；第二电介质层,堆叠在芯层上；其中,第二电介质层包括凹槽,凹槽的开口背离芯层,第二电介质层的折射率小于芯层的折射率；吸收层,覆盖在第二电介质层外表面,与凹槽的侧壁以及凹槽的底部接触；其中,吸收层具有非线性饱和吸收性。(The embodiment of the invention discloses a waveguide structure, an optical device and a manufacturing method of the waveguide structure, wherein the waveguide structure comprises the following components: a first dielectric layer; a core layer stacked on the first dielectric layer, the core layer having a refractive index greater than that of the first dielectric layer; a second dielectric layer stacked on the core layer; the second dielectric layer comprises a groove, an opening of the groove faces away from the core layer, and the refractive index of the second dielectric layer is smaller than that of the core layer; the absorption layer covers the outer surface of the second dielectric layer and is in contact with the side wall of the groove and the bottom of the groove; wherein the absorption layer has a nonlinear saturable absorption.)

1. A waveguide structure, comprising:

a first dielectric layer;

a core layer stacked on the first dielectric layer, the core layer having a refractive index greater than a refractive index of the first dielectric layer;

a second dielectric layer stacked on the core layer; wherein the second dielectric layer comprises a groove having an opening facing away from the core layer, the second dielectric layer having a refractive index less than the refractive index of the core layer;

the absorption layer covers the outer surface of the second dielectric layer and is in contact with the side wall of the groove and the bottom of the groove; wherein the absorbing layer has a nonlinear saturable absorption.

2. The waveguide structure of claim 1,

when a plurality of grooves are included in the second dielectric layer, the opening sizes of at least two grooves are the same;

and/or the presence of a gas in the gas,

when a plurality of the grooves are included in the second dielectric layer, the distance between the bottoms of at least two of the grooves and the core layer is the same.

3. The waveguide structure of claim 1 wherein the absorbing layer comprises:

a single-layer structure;

or the like, or, alternatively,

a multilayer structure including a plurality of sub-absorbent layers arranged in a stack; wherein the multilayer structure comprises at least two sub-absorption layers with the same nonlinear saturated absorption.

4. A waveguide structure according to claim 3,

the materials making up the absorbent layer include: a two-dimensional material.

5. The waveguide structure of claim 4 wherein the two-dimensional material comprises at least one of:

graphene;

molybdenum disulfide;

black phosphorus;

antimony selenide;

bismuth telluride.

6. The waveguide structure of claim 1,

the thickness of the absorption layer is 0.35nm to 30 nm.

7. A light device, comprising:

the waveguide structure of any one of claims 1 to 6;

a first transition structure having a first end coupled to an input optical fiber and a second end coupled to the first end of the waveguide structure;

a second transition structure, a first end of the second transition structure coupled with a second end of the waveguide structure, a second end of the second transition structure coupled with an output optical fiber.

8. A method of fabricating a waveguide structure, comprising:

forming a first dielectric layer;

forming a core layer stacked on the first dielectric layer; wherein the refractive index of the core layer is greater than the refractive index of the first dielectric layer;

forming a second dielectric layer stacked on the core layer, forming a groove in the second dielectric layer; wherein the opening of the groove faces away from the core layer, and the refractive index of the second dielectric layer is smaller than that of the core layer;

forming an absorption layer covering the outer surface of the second dielectric layer; wherein the absorption layer is in contact with the side walls of the groove and the bottom of the groove, the absorption layer having a non-linear saturable absorption.

9. The method of manufacturing according to claim 8,

when a plurality of the grooves are formed in the second dielectric layer, at least two of the grooves having the same opening size are formed;

and/or the presence of a gas in the gas,

when a plurality of the grooves are formed in the second dielectric layer, at least two of the grooves having the same distance between the bottom and the core layer are formed.

10. The method of claim 8, wherein said forming an absorber layer overlying an outer surface of said second dielectric layer comprises:

covering the absorption layer with a single-layer structure on the surface of the second dielectric layer;

or the like, or, alternatively,

covering the absorption layer of a multilayer structure on the surface of the second dielectric layer; wherein the absorption layer of the multilayer structure comprises a plurality of sub-absorption layers, and the multilayer structure comprises at least two sub-absorption layers with the same nonlinear saturable absorption.

Technical Field

The embodiment of the invention relates to the technical field of optical communication, in particular to a waveguide structure, an optical device and a manufacturing method of the waveguide structure.

Background

The femtosecond laser is one of core devices in the technical field of optical communication, and can generate a femtosecond pulse light source with wide application. The chip-level femtosecond laser prepared based on the nonlinear saturable absorber can form ultrashort pulses and has the advantages of high stability, small size and the like. In the related art, when the modulation depth of the femtosecond laser is changed, intrinsic loss is introduced, and the performance of the femtosecond laser is reduced.

Disclosure of Invention

In view of this, embodiments of the present invention provide a waveguide structure, an optical device, and a method for manufacturing the waveguide structure.

A first aspect of an embodiment of the present invention provides a waveguide structure, including:

a first dielectric layer;

a core layer stacked on the first dielectric layer, the core layer having a refractive index greater than a refractive index of the first dielectric layer;

a second dielectric layer stacked on the core layer; wherein the second dielectric layer comprises a groove having an opening facing away from the core layer, the second dielectric layer having a refractive index less than the refractive index of the core layer;

the absorption layer covers the outer surface of the second dielectric layer and is in contact with the side wall of the groove and the bottom of the groove; wherein the absorbing layer has a nonlinear saturable absorption.

Optionally, when a plurality of the grooves are included in the second dielectric layer, the opening sizes of at least two of the grooves are the same;

and/or the presence of a gas in the gas,

when a plurality of the grooves are included in the second dielectric layer, the distance between the bottoms of at least two of the grooves and the core layer is the same.

Optionally, the absorbing layer comprises:

a single-layer structure;

or the like, or, alternatively,

a multilayer structure including a plurality of sub-absorbent layers arranged in a stack; wherein the multilayer structure comprises at least two sub-absorption layers with the same nonlinear saturated absorption.

Optionally, the material constituting the absorption layer comprises: a two-dimensional material.

Optionally, the two-dimensional material comprises at least one of:

graphene;

molybdenum disulfide;

black phosphorus;

antimony selenide;

bismuth telluride.

Optionally, the thickness of the absorption layer is 0.35nm to 30 nm.

A second aspect of an embodiment of the present invention provides an optical device, including:

the waveguide structure provided in any one of the first aspect of the above embodiments of the invention;

a first transition structure having a first end coupled to an input optical fiber and a second end coupled to the first end of the waveguide structure;

a second transition structure, a first end of the second transition structure coupled with a second end of the waveguide structure, a second end of the second transition structure coupled with an output optical fiber.

A third aspect of the embodiments of the present invention provides a method for manufacturing a waveguide structure, including:

forming a first dielectric layer;

forming a core layer stacked on the first dielectric layer; wherein the refractive index of the core layer is greater than the refractive index of the first dielectric layer;

forming a second dielectric layer stacked on the core layer, forming a groove in the second dielectric layer; wherein the opening of the groove faces away from the core layer, and the refractive index of the second dielectric layer is smaller than that of the core layer;

forming an absorption layer covering the outer surface of the second dielectric layer; wherein the absorption layer is in contact with the side walls of the groove and the bottom of the groove, the absorption layer having a non-linear saturable absorption.

Optionally, when a plurality of the grooves are formed in the second dielectric layer, at least two of the grooves having the same opening size are formed;

and/or the presence of a gas in the gas,

when a plurality of the grooves are formed in the second dielectric layer, at least two of the grooves having the same distance between the bottom and the core layer are formed.

Optionally, the forming an absorption layer covering an outer surface of the second dielectric layer includes:

covering the absorption layer with a single-layer structure on the surface of the second dielectric layer;

or the like, or, alternatively,

covering the absorption layer of a multilayer structure on the surface of the second dielectric layer; wherein the absorption layer of the multilayer structure comprises a plurality of sub-absorption layers, and the multilayer structure comprises at least two sub-absorption layers with the same nonlinear saturable absorption.

According to the waveguide structure, the optical device and the manufacturing method of the waveguide structure, the second dielectric layer with the groove is arranged on the core layer, and the absorption layer covers the outer surface of the second dielectric layer, the side wall of the groove and the bottom of the groove. Namely, the grooves are arranged in the second dielectric layer, and the absorption layer is arranged on the basis of the appearance of the grooves and the upper surface of the second dielectric layer, so that the coupling action strengths between different regions of the absorption layer and the core layer are different, and the modulation depth is changed.

Compared with the method that the absorption layer is formed in a specific area by imaging the absorption layer material, and the modulation depth is further changed, the embodiment of the invention realizes the change of the modulation depth by changing the structural size of the groove and forming the absorption layer area with different distances from the core layer based on the groove shape, does not increase the complexity of the process, does not need to image the absorption layer material, reduces the damage to the absorption layer, reduces the introduced intrinsic loss, and improves the performance of the waveguide structure and the optical device.

Drawings

Fig. 1 is a first schematic structural diagram of a waveguide structure according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram ii of a waveguide structure according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of an optical device according to an embodiment of the present invention;

fig. 4 is a schematic flowchart of a method for manufacturing a waveguide structure according to an embodiment of the present invention.

Detailed Description

The technical solution of the present invention will be further elaborated with reference to the drawings and the embodiments. While exemplary implementations of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

The present invention is more particularly described in the following paragraphs with reference to the accompanying drawings by way of example. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.

In the embodiment of the present invention, the term "a is connected to B" includes A, B where a is connected to B in contact with each other, or A, B where a is connected to B in a non-contact manner with other components interposed therebetween.

In the embodiments of the present invention, the terms "first", "second", and the like are used for distinguishing similar objects, and are not necessarily used for describing a particular order or sequence.

The technical means described in the embodiments of the present invention may be arbitrarily combined without conflict.

Referring to fig. 1, an embodiment of the present invention provides a waveguide structure 100, including:

a first dielectric layer 110;

a core layer 120 stacked on the first dielectric layer 110, the core layer 120 having a refractive index greater than that of the first dielectric layer 110;

a second dielectric layer 130 stacked on the core layer 120; wherein the second dielectric layer 130 comprises a groove, an opening of the groove faces away from the core layer 120, and a refractive index of the second dielectric layer 130 is smaller than a refractive index of the core layer 120;

an absorption layer 140 covering the outer surface of the second dielectric layer 130 and contacting the sidewall of the groove and the bottom of the groove; wherein the absorption layer 140 has a nonlinear saturable absorption.

In the waveguide structure, the refractive index of the core layer is greater than that of the first dielectric layer, and the refractive index of the core layer is greater than that of the second dielectric layer, so that light can be totally reflected at the interface between the core layer and the first dielectric layer and the interface between the core layer and the second dielectric layer, and the light is transmitted along a designed route.

In the embodiment of the present invention, as shown in fig. 1, the first dielectric layer may be in contact with the second dielectric layer, and the first dielectric layer and the second dielectric layer surround the core layer for limiting the propagation direction of light in the core layer, and the core layer is used for constituting a path for light propagation. Illustratively, the waveguide structure 100 is an optical waveguide that supports single-mode transmission or multi-mode transmission.

Illustratively, the materials making up the first and second dielectric layers may be the same, e.g., both the first and second dielectric layers may be silicon dioxide. It should be noted that the dashed line in fig. 1 is only used to distinguish the first dielectric layer from the second dielectric layer.

Illustratively, the material constituting the core layer may include: silicon, silicon nitride, aluminum nitride, lithium niobate, and the like.

In the embodiment of the invention, the evanescent field of the transmission mode of the waveguide structure is coupled with the absorption layer, and the first coupling strength between the first region of the absorption layer at the bottom of the groove and the evanescent field is greater than the second coupling strength between the second region of the absorption layer on the upper surface of the second dielectric layer and the evanescent field, so that the control of the modulation depth is realized.

In the waveguide structure, the optical device, and the method for manufacturing the waveguide structure according to the embodiments of the present invention, the second dielectric layer having the groove is disposed on the core layer, and the absorption layer covers the outer surface of the second dielectric layer, the sidewall of the groove, and the bottom of the groove, and since a distance between the absorption layer covering the bottom of the groove and the core layer is smaller than a distance between the absorption layer covering the upper surface of the second dielectric layer and the core layer, a coupling strength between the absorption layer covering the bottom of the groove and the core layer is greater than a coupling strength between the absorption layer covering the upper surface of the second dielectric layer and the core layer, so that a saturation absorption strength and a modulation depth of the absorption layer covering the bottom of the groove are greater than a saturation absorption strength and a modulation depth of the absorption layer covering the upper surface of the second dielectric layer. Namely, the grooves are arranged in the second dielectric layer, and the absorption layer is arranged on the basis of the appearance of the grooves and the upper surface of the second dielectric layer, so that the coupling action strengths between different regions of the absorption layer and the core layer are different, and the modulation depth is changed.

Compared with the method that the absorption layer is formed in a specific area by imaging the absorption layer material, and the modulation depth is further changed, the embodiment of the invention realizes the change of the modulation depth by changing the structural size of the groove and forming the absorption layer area with different distances from the core layer based on the groove shape, does not increase the complexity of the process, does not need to image the absorption layer material, reduces the damage to the absorption layer, reduces the introduced intrinsic loss, and improves the performance of the waveguide structure and the optical device.

According to an embodiment, when the second dielectric layer comprises a plurality of recesses, the opening size of at least two recesses is the same.

As shown in fig. 2, the second dielectric layer 130 includes three recesses therein, and the openings of the three recesses have the same size. It should be noted that the dashed line in fig. 2 is only used to distinguish the first dielectric layer from the second dielectric layer.

In the embodiment of the invention, when the distance between the groove and the core layer is not changed and the opening size of the groove is increased, the area of the absorption layer covering the bottom of the groove is increased, the coupling action strength between the absorption layer covering the bottom of the groove and the core layer is increased, and the modulation depth is increased. That is, when the distance between the groove and the core layer is constant, the modulation depth is positively correlated with the opening size of the groove.

In an embodiment of the present invention, the opening size of the groove may include: 300nm to 40 μm. It will be appreciated that the size of the opening of the recess may be set according to the requirements of the actual application.

In the embodiment of the invention, the sizes of the openings of the grooves are set to be the same, so that the process difficulty is favorably reduced, the manufacturing efficiency is improved, and the cost is reduced.

According to an embodiment, when a plurality of grooves is included in the second dielectric layer, the distance between the bottom of at least two grooves and the core layer is the same.

As shown in fig. 2, the second dielectric layer 130 includes three grooves therein, the three grooves have the same depth, and the distances between the bottoms of the three grooves and the core layer 120 are the same.

In the embodiment of the invention, when the size of the opening of the groove is unchanged and the distance between the bottom of the groove and the core layer is reduced, the coupling effect strength between the absorption layer covering the bottom of the groove and the core layer is increased, and the modulation depth is increased. That is, when the size of the opening of the groove is not changed, the modulation depth and the distance between the bottom of the groove and the core layer are in negative correlation, and the modulation depth and the depth of the groove are in positive correlation.

In an embodiment of the present invention, the distance between the bottom of the groove and the core layer may include: 0 to 20 μm. It will be appreciated that the depth of the groove, the distance between the bottom of the groove and the core layer may be set according to the requirements of the actual application.

In the embodiment of the invention, the distance between the bottom of the groove in the second dielectric layer and the core layer is the same, so that the process difficulty is favorably reduced, the manufacturing efficiency is improved, and the cost is reduced.

According to one embodiment, the absorbent layer comprises:

a single-layer structure;

or the like, or, alternatively,

a multilayer structure including a plurality of sub-absorbent layers arranged in a stack; wherein, the multilayer structure comprises at least two sub-absorption layers with the same nonlinear saturated absorption.

Illustratively, when the multilayer structure includes a plurality of sub-absorbent layers, the plurality of sub-absorbent layers are sequentially stacked to form a sandwich-like multilayer structure. The band gap of the sub-absorption layer is regulated and controlled by utilizing the quantum size effect, so that the modulation depth of the absorption layer is changed.

According to the embodiment of the invention, the absorption layer with the single-layer structure is arranged, so that the process difficulty is favorably reduced, the manufacturing efficiency is improved, and the cost is reduced.

According to the embodiment of the invention, the absorption layer with the multilayer structure is arranged, so that the variation range of the protective absorption strength of the absorption layer can be enlarged, the adjustable range of the modulation depth is enlarged, and the application field of the waveguide structure is enlarged.

According to one embodiment, the material constituting the absorption layer comprises: a two-dimensional material.

According to an embodiment, the two-dimensional material comprises at least one of:

graphene;

molybdenum disulfide;

black phosphorus;

antimony selenide;

bismuth telluride.

According to one embodiment, the thickness of the absorption layer is 0.35nm to 30 nm.

In the embodiment of the present invention, when the absorption layer has a multi-layer structure, the thickness of each sub-absorption layer may be the same. For example, when the thickness of the absorption layer is 10nm and the absorption layer has 4 sub-absorption layers, the thickness of each absorption layer is set to 2.5 nm.

In the embodiment of the present invention, when the absorption layer is a multi-layer structure, the thickness of each sub-absorption layer in the absorption layer may be set according to the nonlinear saturated absorption of the sub-absorption layer. For example, when the nonlinear saturable absorbencies of the first sub-absorbent layer and the second sub-absorbent layer are the same, the first sub-absorbent layer may have the same thickness as the second sub-absorbent layer.

By arranging the sub-absorption layers with the same thickness, the process difficulty is not improved, the process parameters are favorably unified, the process flow is simplified, and the preparation efficiency is improved.

As shown in fig. 3, an embodiment of the present invention provides an optical device 200, including:

a waveguide structure 100;

a first transition structure 210, a first end of the first transition structure 210 being coupled to the input fiber 220, a second end of the first transition structure 210 being coupled to the first end of the waveguide structure 100;

a second transition structure 230, a first end of the second transition structure 230 being coupled to the second end of the waveguide structure 100, and a second end of the second transition structure 230 being coupled to an output optical fiber 240.

In the embodiment of the present invention, the coupling of the first transition structure and the waveguide structure and the coupling of the second transition structure and the waveguide structure may be achieved by a lateral coupling method.

Illustratively, the lateral coupling method may include an inverse tapered spot conversion method. Specifically, as shown in fig. 3, a first transition structure 210 with a gradually increasing width is disposed along the propagation direction of light in the waveguide structure, and light coupled into the first transition structure from the input optical fiber is coupled into the waveguide structure 100. A second transition structure 230 of gradually decreasing width is arranged along the propagation direction of the light in the waveguide structure such that the light coupled in the waveguide structure 100 is coupled to an output optical fiber 240. At this time, the first transition structure and the second transition structure are tapered optical waveguides.

An absorption layer covers the end face of the single-mode fiber, and a pumping light source, a gain medium, a polarization controller, a wavelength division multiplexer and other elements are combined to form an annular cavity, so that the mode of the passive mode-locked femtosecond laser is formed. Compared with the annular cavity built by the traditional separation device for realizing the passive mode-locking femtosecond laser, the optical device provided by the embodiment of the invention has the advantages of small size, high stability, low cost and capability of realizing chip-level integration, and the user experience is improved.

As shown in fig. 4, an embodiment of the present invention provides a method for manufacturing a waveguide structure, including:

step S10: forming a first dielectric layer;

step S20: forming a core layer stacked on the first dielectric layer; wherein the refractive index of the core layer is greater than the refractive index of the first dielectric layer;

step S30: forming a second dielectric layer stacked on the core layer, forming a groove in the second dielectric layer; wherein the opening of the groove faces away from the core layer, and the refractive index of the second dielectric layer is smaller than that of the core layer;

step S40: forming an absorption layer covering the outer surface of the second dielectric layer; wherein the absorption layer is in contact with the side wall of the groove and the bottom of the groove, and the absorption layer has nonlinear saturated absorption.

Illustratively, when the first dielectric layer is a silicon dioxide layer, the first dielectric layer may be formed by a chemical vapor deposition method in step S10. For example: by gaseous Silane (SiH)₄) Phosphine (PH)₃) And oxygen (O)₂) A chemical reaction occurs to form a first dielectric layer on the substrate.

For example, when the core layer is a silicon nitride layer, the step S20 may include the following steps:

coating photoresist on the first dielectric layer;

performing imaging processing on the photoresist to expose a first preset area of the first dielectric layer;

forming a silicon nitride layer in the first predetermined region by a chemical vapor deposition method;

and mechanically stripping the residual photoresist on the surface of the first dielectric layer and removing the redundant silicon nitride material.

Exemplarily, when the second dielectric layer is a silicon dioxide layer, the step S30 may include the steps of:

forming a silicon dioxide layer with a certain thickness by a chemical vapor deposition method;

coating photoresist on the silicon dioxide, and carrying out imaging treatment on the silicon dioxide to expose a second preset region of the core layer;

and etching the second preset region based on the photoresist after the imaging processing to form a groove.

In this example, the second predetermined region may be etched by a dry etching method or a wet etching method.

In this example, different time etch processes may be performed to form different depths of recesses in the second dielectric layer when etching the second predetermined region.

Illustratively, in step S40, an absorption layer covering the outer surface of the second medium layer may be formed by mechanical transfer, and the absorption layer contacts the sidewalls of the groove and the bottom of the groove. For example, the absorption layer covering the outer surface of the second dielectric layer may be formed by a wet transfer method, and the absorption layer may be in contact with the sidewalls of the groove and the bottom of the groove.

Illustratively, when the first dielectric layer and the second dielectric layer are silicon dioxide layers, the core layer is a silicon nitride layer, and the material constituting the absorption layer includes graphene, the wet transfer method includes the steps of:

cutting the copper foil deposited with the graphene into a preset shape (such as a rectangle, a circle and the like);

coating a layer of polymethyl methacrylate (PMMA) on the surface of the copper foil on which the graphene is deposited by using a spin coating method, and drying;

corroding the copper foil by using a ferric chloride solution with the concentration of 0.1-2 mol/L to obtain a graphene/PMMA film;

rinsing the obtained graphene/PMMA film by using deionized water to remove substances such as ferric chloride solution, ferrous chloride and the like remained on the graphene/PMMA film;

immersing a preset structure formed with a first dielectric layer, a core layer and a second dielectric layer which are stacked below the floating graphene/PMMA film, and enabling one side, with the groove, of the second dielectric layer to face the graphene/PMMA film; then slowly fishing out the preset structure, so that when the second dielectric layer with the groove is in contact with the graphene/PMMA film, the graphene/PMMA film is attached to the upper surface of the second dielectric layer and is in contact with the side wall of the groove and the bottom of the groove;

the PMMA is dissolved and the pre-set structure covered with graphene is dried.

In the above example, since the graphene/PMMA thin film has a large specific surface area, when it is in contact with the predetermined structure, it can be easily adsorbed on the upper surface of the second dielectric layer due to its strong adsorption force.

Compared with the method for forming the absorption layer by imaging the absorption layer material, the method for forming the waveguide structure by the laser device has the advantages that the modulation depth is changed by changing the structural size of the groove, the process is relatively simple, imaging processing is not needed to be carried out on the absorption layer material, damage to the absorption layer is reduced, the introduced intrinsic loss is reduced, and the performance of the waveguide structure and the laser device is improved.

According to one embodiment, when a plurality of recesses are formed in the second dielectric layer, at least two recesses having the same opening size are formed.

In the embodiment of the invention, the sizes of the openings of the grooves are set to be the same, so that the process difficulty is favorably reduced, the manufacturing efficiency is improved, and the cost is reduced.

According to one embodiment, when forming the plurality of grooves in the second dielectric layer, at least two grooves are formed with the same distance between the bottom and the core layer.

In the embodiment of the invention, the distance between the bottom of the groove in the second dielectric layer and the core layer is the same, so that the process difficulty is favorably reduced, the manufacturing efficiency is improved, and the cost is reduced.

According to one embodiment, step S40 includes:

covering the surface of the second dielectric layer with an absorption layer with a single-layer structure;

or the like, or, alternatively,

covering the surface of the second dielectric layer with an absorption layer of a multilayer structure; the absorption layer of the multilayer structure comprises a plurality of sub-absorption layers, and the multilayer structure comprises at least two sub-absorption layers with the same nonlinear saturated absorption.

According to the embodiment of the invention, the absorption layer with the single-layer structure is arranged, so that the process difficulty is favorably reduced, the manufacturing efficiency is improved, and the cost is reduced.

According to the embodiment of the invention, the absorption layer with the multilayer structure is arranged, so that the variation range of the protective absorption strength of the absorption layer can be enlarged, the adjustable range of the modulation depth is enlarged, and the application field of the waveguide structure is enlarged.

Those of ordinary skill in the art will understand that: all or part of the steps for implementing the method embodiments may be implemented by hardware related to program instructions, and the program may be stored in a computer readable storage medium, and when executed, the program performs the steps including the method embodiments; and the aforementioned storage medium includes: a mobile storage device, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

The methods disclosed in the several method embodiments provided in the present application may be combined arbitrarily without conflict to obtain new method embodiments.

Features disclosed in several of the product embodiments provided in the present application may be combined in any combination to yield new product embodiments without conflict.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.