Mode-insensitive optical switch based on organic polymer waveguide

Abstract

The application discloses a mode-insensitive optical switch based on an organic polymer waveguide and belongs to the technical field of mode-insensitive optical switches.The mode-insensitive optical switch is composed of a substrate, a polymer waveguide lower cladding layer, a rectangular polymer optical waveguide core layer, a polymer waveguide upper cladding layer, a first graphene capacitor and a second graphene capacitor.The polymer waveguide lower cladding layer is prepared on the substrate, the polymer waveguide upper cladding layer is prepared on the polymer waveguide lower cladding layer, and the rectangular polymer optical waveguide core layer is covered in the polymer waveguide lower cladding layer and the polymer waveguide upper cladding layer.The optical switch adopts a polymer material to design a waveguide structure, graphene is used as a modulation electrode and is buried in the waveguide, through designing a graphene capacitor electrode structure and optimizing a buried position, simultaneous modulation and switching of TE 11 , TE 21 , TE 12 and TE 22 modes can be realized, and the preparation process is compatible with a traditional CMOS process and is easy to integrate.

Description

Technical Field

[0001] This invention belongs to the field of mode-insensitive optical switch technology, specifically relating to a mode-insensitive optical switch based on an organic polymer waveguide, using silicon as a substrate, organic polymer as the waveguide core and cladding, and graphene as the modulation electrode. Background Technology

[0002] In recent years, with the rapid development of global broadband services, the demand for information transmission capacity and speed has been continuously increasing. Optical fiber communication speeds have increased from the Tbit / s to the Pbit / s level, causing the transmission capacity of single-mode fiber to gradually approach its nonlinear Shannon limit. To address the urgent need for rapidly increasing communication capacity, mode division multiplexing (MDM) technology has been proposed to further enhance the information capacity of optical fiber communication systems, leading to the increasing application of MDM waveguide devices. In MDM systems, the performance of mode optical switches is crucial for signal transmission and processing. However, current mode optical switches can only achieve conversion between the fundamental mode and higher-order modes, exhibiting sensitivity to different transmission modes, thus limiting their application in MDM systems.

[0003] Reducing the complexity of mode-sensitive optical switches, while maintaining transmission capacity, and minimizing the number of parallel channels, has significant application value. This can greatly reduce system cost, device size, and insertion loss, while improving system reliability and efficiency, representing the future direction of mode-sensitive optical switches. Polymer optical waveguides, with their simple and flexible fabrication processes, are widely used in planar optical waveguide device research. In particular, optical switches based on organic polymer materials have advantages such as low power consumption and low cost, attracting increasing attention. Graphene, as an emerging two-dimensional material, possesses advantages such as an ultra-wide spectral range, tunable optical absorption, and high electronic conductivity, and has been widely used in optoelectronic device research to control optical signals. The simple and flexible fabrication process of polymer waveguides allows graphene to be embedded within them, thereby enhancing its interaction with the optical field and fabricating optoelectronic devices with high integration, low power consumption, and easy tuning. This invention patent mainly utilizes the tunable optical absorption characteristics of graphene and leverages the advantages of polymer optical waveguide fabrication to realize a mode-insensitive optical switch device based on an organic polymer waveguide. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, the present invention aims to provide a mode-insensitive optical switch based on an organic polymer waveguide. This invention achieves mode-insensitive optical switching in a few-mode waveguide within the C-band by modulating the chemical potential of buried graphene. 11 TE 21 TE 12 and TE 22The simultaneous modulation and switching of four modes solves the problems of numerous parallel channels, non-compact structure, and inability to simultaneously control multiple modes in previous mode-division multiplexing systems. This invention can greatly expand the integration level and application scenarios of polymer-based integrated optoelectronic devices, significantly increasing the transmission capacity of signal channels.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A mode-insensitive optical switch structure based on an organic polymer waveguide uses a silicon wafer as a substrate, with an organic polymer material as the core and cladding material of the waveguide, and graphene as the modulation electrode embedded inside the waveguide core. This achieves mode-insensitive modulation and switching, fully utilizing the advantages of simple and flexible fabrication processes of organic polymer materials. Furthermore, the fabrication process used in this invention is compatible with semiconductor processes, easy to integrate, and suitable for large-scale production, thus possessing significant practical application value.

[0007] The solution of the present invention is attached. Figure 1 The diagram shows a cross-sectional structure of a mode-insensitive optical switch based on an organic polymer waveguide, perpendicular to the light propagation direction. Its function is to control the transmission direction of light (TE). 11 TE 21 TE 12 and TE 22The mode simultaneously performs modulation and switching, characterized by: comprising a substrate 1, a polymer waveguide lower cladding 2, a rectangular polymer waveguide core layer 3, a polymer waveguide upper cladding 5, a first graphene capacitor 4, and a second graphene capacitor 6; the polymer waveguide lower cladding 2 is fabricated on the substrate 1, the polymer waveguide upper cladding 5 is fabricated on the polymer waveguide lower cladding 2, and the rectangular polymer waveguide core layer 3 is encased within the polymer waveguide lower cladding 2 and the polymer waveguide upper cladding 5; a stepped structure is formed between the polymer waveguide upper cladding 5 and the polymer waveguide lower cladding 2, i.e., a step structure is formed between the polymer waveguide upper cladding 5 and the polymer waveguide lower cladding 2. The polymer waveguide lower cladding 2 is exposed on both the left and right sides of the upper cladding 5, with certain areas exposed. The first graphene capacitor 4 and the second graphene capacitor 6 are located inside the polymer waveguide core layer 3, both being double-layer graphene structures, positioned at the same horizontal level with a certain spacing. The first graphene capacitor 4 consists of a lower first monolayer graphene 43, a middle first dielectric insulating layer 45, an upper second monolayer graphene 44, a first metal contact electrode 41, and a second metal contact electrode 42. The second graphene capacitor 6 consists of a lower first monolayer graphene 43, a middle second dielectric insulating layer 45, a lower first dielectric insulating layer 45, a middle second dielectric insulating layer 45, a lower first dielectric insulating layer 46, a lower first ... The structure comprises an insulating layer 63, an upper third monolayer graphene 62, and a third metal contact electrode 61. A first graphene narrow strip, integrally formed with the first monolayer graphene 43, is disposed to the right of the first monolayer graphene 43. A polymer waveguide cladding 5 extends from the first graphene narrow strip to the right, and a first metal contact electrode 41 is fabricated on the surface of the first graphene narrow strip. Similarly, a second graphene narrow strip, integrally formed with the second monolayer graphene 44, is disposed to the right of the second monolayer graphene 44. A polymer waveguide cladding 5 extends from the second graphene narrow strip to the right, and a second metal contact electrode 61 is fabricated on the second graphene narrow strip. Contact electrode 42; the first graphene narrow strip and the second graphene narrow strip are separated by the polymer waveguide cladding 5; a third graphene narrow strip with an integral structure of the third monolayer graphene 62 is provided on the left side of the third monolayer graphene 62, the third graphene narrow strip extends to the left out of the polymer waveguide cladding 5, and a third metal contact electrode 61 is prepared on the surface of the third graphene narrow strip; the lengths of the first graphene narrow strip, the second graphene narrow strip, and the third graphene narrow strip are less than the lengths of the first monolayer graphene 43, the second monolayer graphene 44, and the third monolayer graphene 62 (the length direction is perpendicular to the cross-sectional direction).

[0008] The substrate material is one of silicon dioxide, silicon nitride, and silicon, with a width (x-axis direction) of 1~3mm and a thickness (y-axis direction) of 300~800μm;

[0009] The polymer waveguide lower cladding 2 and polymer waveguide upper cladding 5 are made of the same material, namely one of EpoCore, EpoClad, polymethyl methacrylate (PMMA), polyethylene (PE), polyester (PET), and polystyrene (PS); the polymer waveguide core layer 3 is made of one of SU-8 2002, SU-8 2005, polycarbonate (PC), and polyimide (PI). The refractive index of the polymer waveguide core layer is greater than that of the polymer cladding.

[0010] The width of the polymer waveguide lower cladding 2 is the same as the width of the substrate (x-axis direction) and is 1~3mm, and the thickness (y-axis direction) is 10~20μm; the width (x-axis direction) of the polymer waveguide upper cladding 5 is 100~1500μm, and the thickness (y-axis direction) is 15~20μm (including the thickness of the polymer waveguide upper cladding 5 between the first graphene narrow strip and the second graphene narrow strip), and the width of the polymer waveguide upper cladding 5 is smaller than the width of the polymer waveguide lower cladding 2; the width (x-axis direction) of the polymer optical waveguide core layer 3 is 5~15μm, and the thickness is 5~15μm.

[0011] Furthermore, the first monolayer graphene 43, the second monolayer graphene 44, and the third monolayer graphene 62 in the first graphene capacitor 4 and the second graphene capacitor 6 are parallel to the surface of the substrate 1 and have the same thickness of 0.35~0.7nm; the effective width of the first graphene capacitor 4 and the second graphene capacitor 6 is 5~15μm, and they are buried inside the polymer waveguide core layer 3; the first graphene capacitor 4 and the second graphene capacitor 6 share the first monolayer graphene 43, which is located on the upper surface of the polymer waveguide lower cladding 2, and the second monolayer graphene 44 and the third monolayer graphene 62 are located in the same plane; the spacing between the first graphene capacitor 4 and the second graphene capacitor 6 inside the polymer waveguide core layer 3 is 0.1~2μm.

[0012] Furthermore, the dielectric insulating layer in each graphene capacitor is made of one of aluminum oxide, hexagonal boron nitride, or silicon dioxide. The thickness of the dielectric insulating layer is the same, ranging from 5 to 20 nm. The dielectric insulating layer is buried between the two layers of graphene in each graphene capacitor, and its width is the same as the effective width of each graphene capacitor.

[0013] Furthermore, the materials of the first metal contact electrode 41, the second metal contact electrode 42, and the third metal contact electrode 61 are alloys composed of one or more metals selected from silver, gold, aluminum, and platinum. The distance between each electrode and the center of the polymer waveguide core layer 3 is 100~800μm (along the length direction, the first metal contact electrode 41 and the second metal contact electrode 42 are staggered by a certain distance and do not contact each other). Each electrode has the same width of 50~100μm, the same thickness of 100~300nm, and the same length of 50~100μm (the same length as the graphene strip).

[0014] This invention belongs to the field of mode-insensitive optical switch technology. The specific working principle is as follows: The device mainly utilizes the tunable light absorption characteristics of graphene, and its sensitivity to TE is controlled by applying a bias voltage to the graphene. 11 TE 21 TE 12 and TE 22 The light absorption intensity of the mode. Simultaneously, the burial position of the graphene capacitor was optimized to align with the TE... 11 TE 21 TE 12 and TE 22 The interaction strength of each mode is similar, thus achieving the function of a switch that is insensitive to these four modes.

[0015] Compared with existing device structures and fabrication techniques, the advantages of this invention are:

[0016] This invention relates to a mode-insensitive optical switch based on an organic polymer waveguide. The waveguide structure is designed using polymer materials, with graphene as the modulation electrode embedded within the waveguide. By designing the graphene capacitor electrode structure and optimizing the embedding location, mode-insensitive optical switches can be achieved when directly connected to a few-mode waveguide. 11 TE 21 TE 12 and TE 22 The mode can be simultaneously modulated and switched, making full use of the advantages of the variety of polymer materials and their ease of preparation and processing. Furthermore, the design of graphene capacitor structures is easier to realize in terms of preparation process, and the preparation process is compatible with traditional CMOS processes and easy to integrate.

[0017] This invention can greatly expand the integration level and application scenarios of polymer photonic integrated devices, significantly reduce the number of signal channels in the mode division multiplexing system, and effectively increase the communication capacity while improving the system integration level. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the cross-sectional structure of the mode-insensitive optical switch based on organic polymer waveguide described in this invention along the direction of light transmission.

[0019] Figure 2 This is a simulation diagram of the optical field distribution of the mode-insensitive optical switch based on organic polymer waveguides described in this invention.

[0020] Figure 3 The TE based on an organic polymer waveguide-based mode-insensitive optical switch described in this invention 11 TE 21 TE 12 and TE 22 A schematic diagram showing the change in mode power decay with the chemical potential energy of graphene.

[0021] Figure 4 The TE based on an organic polymer waveguide-based mode-insensitive optical switch described in this invention 11 TE 21 TE 12 and TE 22 Schematic diagram showing how mode power attenuation changes in the C-band.

[0022] As attached Figure 1 The diagram shows a cross-sectional view of the mode-insensitive optical switch based on an organic polymer waveguide described in this invention. Its function is to enable mode insensitive optical switches to control the TE signal in the waveguide. 11 TE 21 TE 12 and TE 22 The mode simultaneously performs modulation and switching. The components are named as follows: substrate 1, polymer waveguide lower cladding 2, polymer waveguide core layer 3, polymer waveguide upper cladding 5, first graphene capacitor 4 fabricated in the polymer waveguide core layer 3, lower first monolayer graphene 43, first dielectric insulating layer 45, upper second monolayer graphene 44, first metal contact electrode 41, and second metal contact electrode 42; second graphene capacitor 6 fabricated in the polymer waveguide core layer 3 structure, lower first monolayer graphene 43, second dielectric insulating layer 63, upper second monolayer graphene 62, and third metal contact electrode 61. The first graphene capacitor 4 and the second graphene capacitor 6 have a certain spacing between them and share the lower first monolayer graphene 43.

[0023] As attached Figure 2 As shown, the TE based on an organic polymer waveguide-based mode-insensitive optical switch of the present invention... 11 TE 21 TE 12 and TE 22 Simulated pattern of light field distribution. Figure 2 (a) is TE 11 Simulation diagram of light field distribution Figure 2 (b) is TE 21 Simulation diagram of light field distribution Figure 2 (c) is TE 12 Simulation diagram of light field distribution Figure 2 (d) is TE 22 Simulated light field distribution. From Figure 2 (a) shows that TE 11 The mode light field shape is good, with the strongest light field located at the center of the waveguide core layer. From Figure 2 (b) shows that TE 21 The mode light field shape is good, with the strongest light field located at the left and right positions of the waveguide core layer. From Figure 2 (c) shows that TE 12 The mode light field shape is good, with the strongest light fields located above and below the waveguide core layer. From Figure 2 (d) shows that TE 22 The mode light field shape is good, with the strongest light field located at the four apex corners of the waveguide core layer. (Combined with...) Figure 2 From (a)(b)(c)(d), we can see that TE 11 The mode optical field in the middle horizontal direction inside the waveguide is related to TE. 21 The mode light fields have overlapping regions, TE 11 The mode optical field is perpendicular to the TE in the middle of the waveguide. 12 The mode light fields have overlapping regions, TE 11 The mode optical field is above the TE inside the waveguide. 22 The mode light fields have overlapping regions, TE 12 Mode light field and TE 21 and TE 22 The mode optical field overlaps in the four vertices of the waveguide core layer.

[0024] As attached Figure 3 As shown, the TE based on an organic polymer waveguide-based mode-insensitive optical switch of the present invention... 11 TE 21 TE 12 and TE 22 A schematic diagram illustrating the change in mode power decay as a function of graphene chemical potential. From Figure 3 As can be seen from this, TE in the waveguide 11 TE 21 TE 12 and TE 22 The mode power decays show an almost identical trend, and the differences in mode power decay values ​​are small at the same chemical potential energy. This indicates that by regulating the first graphene capacitor 4 and the second graphene capacitor 6 (by applying a voltage to the metal electrode prepared on the graphene to achieve voltage regulation of the graphene capacitor, the chemical potential of the graphene changes with the applied voltage, as shown in the formula |μ| = ħv), the chemical potential of the graphene changes accordingly. F (πa0|Vg − V)Dirac |) describes this regulation process, where ħ is the simplified Planck constant, and v F For Fermi velocity, V Dirac The bias voltage caused by natural doping, a0 = ε0ε r / de is obtained from a simple parallel plate capacitor model (ε0 is the relative permittivity of air, ε r d and d represent the dielectric constant and thickness of the dielectric, respectively, and e is the unit charge. Then, TE can be used. 11 TE 21 TE 12 and TE 22 The four modes are simultaneously modulated and switched on, achieving a nearly identical modulation effect. When the chemical potential is 0.3 eV, the mode power attenuation of each mode reaches its maximum value, that is, the waveguide's absorption efficiency for the optical signal reaches its maximum, corresponding to the device's "OFF" operating state. When the chemical potential is greater than 0.5 eV, the power attenuation of each mode decreases rapidly and then remains stably at a very low level. At this point, the optical signal transmitted in the optical waveguide can pass through almost without loss, corresponding to the device's "ON" operating state.

[0025] As attached Figure 4 As shown, the TE based on an organic polymer waveguide-based mode-insensitive optical switch of the present invention... 11 TE 21 TE 12 and TE 22 A schematic diagram illustrating the variation of mode power decay in the C-band at μ = 0 eV (the chemical potential of graphene without applying a bias voltage). From... Figure 4 TE can be seen from 11 TE 21 TE 12 and TE 22 When the chemical potential is 0 eV, i.e. when the device is in a strong absorption state, the mode power attenuation in the C-band is not significant. This means that the light absorption capacity of the first graphene capacitor 4 and the second graphene capacitor 6 remains stable, indicating that the device can be used for wide-band operation and maintain stable modulation function. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1:

[0028] The solution of the present invention is attached. Figure 1 As shown, a mode-insensitive optical switch based on an organic polymer waveguide is presented, which functions to control the mode of TE. 11 TE 21 TE 12 and TE 22 The mode simultaneously performs modulation and switching, characterized by: comprising a substrate 1, a polymer waveguide lower cladding 2, a rectangular polymer waveguide core layer 3, a polymer waveguide upper cladding 5, a first graphene capacitor 4, and a second graphene capacitor 6; the polymer waveguide lower cladding 2 is fabricated on the substrate 1, the polymer waveguide upper cladding 5 is fabricated on the polymer waveguide lower cladding 2, and the rectangular polymer waveguide core layer 3 is encased within the polymer waveguide lower cladding 2 and the polymer waveguide upper cladding 5; a stepped structure is formed between the polymer waveguide upper cladding 5 and the polymer waveguide lower cladding 2, i.e., a step structure is formed between the polymer waveguide upper cladding 5 and the polymer waveguide lower cladding 2. The polymer waveguide lower cladding 2 is exposed on both the left and right sides of the upper cladding 5, with certain areas exposed. The first graphene capacitor 4 and the second graphene capacitor 6 are located inside the polymer waveguide core layer 3, both being double-layer graphene structures, positioned at the same horizontal level with a certain spacing. The first graphene capacitor 4 consists of a lower first monolayer graphene 43, a middle first dielectric insulating layer 45, an upper second monolayer graphene 44, a first metal contact electrode 41, and a second metal contact electrode 42. The second graphene capacitor 6 consists of a lower first monolayer graphene 43, a middle second dielectric insulating layer 45, a lower first dielectric insulating layer 45, a middle second dielectric insulating layer 45, a lower first dielectric insulating layer 46, a lower first ... The structure comprises an insulating layer 63, an upper third monolayer graphene 62, and a third metal contact electrode 61. A first graphene narrow strip, integrally formed with the first monolayer graphene 43, is disposed to the right of the first monolayer graphene 43. A polymer waveguide cladding 5 extends from the first graphene narrow strip to the right, and a first metal contact electrode 41 is fabricated on the surface of the first graphene narrow strip. Similarly, a second graphene narrow strip, integrally formed with the second monolayer graphene 44, is disposed to the right of the second monolayer graphene 44. A polymer waveguide cladding 5 extends from the second graphene narrow strip to the right, and a second metal contact electrode 61 is fabricated on the second graphene narrow strip. Contact electrode 42; the first graphene narrow strip and the second graphene narrow strip are separated by the polymer waveguide cladding 5; a third graphene narrow strip with an integral structure of the third monolayer graphene 62 is provided on the left side of the third monolayer graphene 62, the third graphene narrow strip extends to the left out of the polymer waveguide cladding 5, and a third metal contact electrode 61 is prepared on the surface of the third graphene narrow strip; the lengths of the first graphene narrow strip, the second graphene narrow strip, and the third graphene narrow strip are less than the lengths of the first monolayer graphene 43, the second monolayer graphene 44, and the third monolayer graphene 62 (the length direction is perpendicular to the cross-sectional direction).

[0029] In this embodiment, a silicon wafer is used as the substrate layer, with a thickness of 500 μm and a width of 1.9 mm.

[0030] In this embodiment, the polymer waveguide lower cladding 2 and polymer waveguide upper cladding 5 are made of a low folding ratio polymer material, specifically EpoClad.

[0031] In this embodiment, the thickness of the polymer waveguide cladding 2 is 12 μm, and its width is the same as that of the substrate layer, which is 1.9 mm.

[0032] In this embodiment, the cladding 5 on the polymer waveguide has a thickness of 15 μm and a width of 500 μm.

[0033] In this embodiment, the polymer waveguide core layer 3 is made of SU-8 2002 material.

[0034] In this embodiment, the polymer waveguide core layer 3 has a thickness of 10.5 μm and a width of 10 μm.

[0035] In this embodiment, the polymer waveguide core layer 3 is located at the upper-middle position in the x-direction of the polymer waveguide cladding layer 2.

[0036] In this embodiment, the graphene on both the top and bottom of the dielectric insulating layer in each graphene capacitor is a single layer of graphene.

[0037] In this embodiment, the dielectric insulating layer is made of aluminum oxide with a thickness of 20 nm, a width of 4.5 μm in the first graphene capacitor 4, and a width of 4.5 μm in the second graphene capacitor 6.

[0038] In this embodiment, the thickness of the upper and lower graphene layers in each graphene capacitor is 0.7 nm. The effective region length of the first graphene capacitor 4 is 4.5 μm, and it is placed 2.84 μm above the horizontal center position of the polymer waveguide core layer 3. The effective region length of the second graphene capacitor 4 is 4.5 μm, and it is located 2.84 μm above the horizontal center position of the polymer waveguide core layer 3. The distance between the first graphene capacitor 4 and the second graphene capacitor 6 is 1 μm.

[0039] In this embodiment, each graphene capacitor is placed inside the polymer waveguide core layer 3 to achieve TE. 11 TE 21 TE 12 and TE 22 It can simultaneously perform modulation and switching functions in four modes.

[0040] In this embodiment, the metal electrode is made of gold, with a width of 100 μm, a thickness of 200 nm, and a length of 80 μm.

[0041] From the equivalent circuit of the mode-insensitive optical switch electrode structure, it can be seen that the total resistance R total =2Rs ×(W G / L)+2R c / L, where R s =200Ω / □ is the resistance of the graphene layer, R c =100Ω-μm is the contact resistance between the metal electrode and the graphene, W G The effective area width of the graphene capacitor is W in graphene capacitors 4 and 6. G Both are 4.5 μm, and L is the length of a single layer of graphene, both taken as 800 μm; total capacitance C total =ε0ε r S / d, S=L×W is the effective area of ​​the bilayer graphene plate capacitance, ε0 is the relative permittivity of air, ε r Let f be the relative permittivity of the dielectric insulating layer. The 3-dB modulation bandwidth formula is f = 1 / (2πR). total C total The 3-dB bandwidth of both the first graphene capacitor 4 and the second graphene capacitor 6 was found to be 1.84 GHz. The device's calculated drive power consumption formula is E. bit =C total (△U) 2 / 4, where ΔU is the range of applied bias voltage corresponding to the graphene chemical potential of 0.3eV to 0.7eV, which is 2.35V. Therefore, the power consumption of graphene capacitors 4 and 6 is 25pJ / bit.

[0042] Example 2:

[0043] The specific fabrication process of the mode-insensitive optical switch based on organic polymer waveguide of the present invention includes the following steps:

[0044] 1. Cleaning of the substrate silicon wafer: First, place the dissociated silicon wafer in an acetone solution and sonicate it. Then, wipe the surface of the silicon wafer with cotton balls soaked in acetone and ethanol. After that, rinse the surface with deionized water and blow the deionized water off the surface with nitrogen. Finally, bake it at high temperature to remove the residual moisture on the surface.

[0045] 2. Fabrication of polymer waveguide cladding 2 by spin coating: The polymer waveguide cladding material EpoClad was spin-coated onto a clean substrate at a spin coating speed of 2500 rpm. After spin coating, the substrate was placed in an oven at 120°C for 2.5 hours to prepare a polymer waveguide cladding 2 with a thickness of 10 μm.

[0046] 3. Wet etching process for fabricating polymer waveguide core layer 3: Polymer SU-8 2002 is spin-coated onto the upper surface of the polymer waveguide lower cladding 2 using a spin-coating method at a speed of 2500 rpm, resulting in a film thickness of 10 μm. The film is then pre-baked at 65°C for 15 minutes and 90°C for 20 minutes; followed by intermediate baking at 65°C for 15 minutes and 95°C for 20 minutes. After cooling to room temperature, photolithography is performed using a photomask. The device is then placed on a heated plate and heated at 65°C for 10 minutes and 95°C for 20 minutes. Finally, it is immersed in a dedicated polymer SU-8 2002 developing solution for 40 seconds. The unexposed portions of SU-8... The 2002 layer was etched away; then it was placed in an isopropanol solution to remove residual developer, and then repeatedly rinsed with deionized water to remove residual liquid. After drying the surface liquid with a rubber bulb, it was placed at 120°C for 30 minutes for post-baking; the polymer waveguide core layer film thickness was etched to 7.16 μm using an inductively coupled plasma etching machine. Through the above process, the polymer waveguide core layer 3 was prepared on the polymer waveguide lower cladding 2;

[0047] 4. Using a spin-coating process, the polymer waveguide cladding material EpoClad is spin-coated onto the rectangular polymer waveguide core layer 3 and polymer waveguide cladding layer 2 to form a thin film. The spin-coating speed is 1500 rpm. Then, it is baked at 120℃ for 2.5 hours to obtain a thickness of 8 μm. The polymer waveguide cladding layer is then etched using an inductively coupled plasma etching machine to obtain a polymer planar layer with a height equal to that of the polymer waveguide core layer 3.

[0048] 5. Transferring the common first monolayer graphene 43 of the first graphene capacitor 4 and the second graphene capacitor 6 onto the polymer waveguide core layer 3: The preparation process is as follows: Commercially available monolayer graphene is transferred to the surface of the prepared polymer waveguide core layer 3 and polymer planar layer. The first monolayer graphene layer 43 is in contact with the polymer waveguide core layer 3. Polymer PMMA is spin-coated onto the surface of the monolayer graphene to obtain a polymer PMMA film. Then, electron beam lithography is used to define the preparation of the first monolayer graphene 43 along with narrow strips of graphene. In the region of the graphene structure, the photolithographically etched polymer PMMA film is partially removed, exposing the underlying monolayer graphene. Then, oxygen plasma dry etching is used to etch away the exposed graphene layer, thereby obtaining the first monolayer graphene 43 with a narrow stripe graphene structure covered by a PMMA film. Finally, the polymer PMMA film is removed in an acetone solution, the residual acetone solution is removed with deionized water, and then it is baked at 90°C to obtain the first monolayer graphene 43 with a narrow stripe graphene structure.

[0049] 6. Fabrication of the first metal electrode 41: In step 5, a polymer material PMMA is spin-coated onto the surface of the device to achieve complete coverage, resulting in a polymer PMMA film; then, electron beam lithography is used to define the area for evaporating the first metal electrode 41. The lithographic polymer PMMA film is developed away, exposing the narrow strip graphene structure underneath; finally, an electron beam evaporation deposition device is used to deposit a metal Au layer onto the surface of the device to achieve complete coverage, and then the polymer PMMA film and the metal Au layer on it are peeled off (metal lift-off process), thereby fabricating the first metal electrode 41 on the narrow strip graphene structure;

[0050] 7. Transfer of the second monolayer graphene 44 and the third monolayer graphene 62: Before transferring the second monolayer graphene 44 and the third monolayer graphene 62, dielectric insulating layers 63 and 45 need to be deposited on the first monolayer graphene layer 43 by vapor deposition. Then, the dielectric insulating layer is dry-etched vertically to obtain the gap in the middle. Then, the transfer and preparation of the second monolayer graphene 44 and the third monolayer graphene 62 are carried out. The process flow is the same as that of the transfer of the first monolayer graphene 43. The gap in the middle is prepared when defining the graphene pattern.

[0051] 8. Preparation of the second metal electrode 42 and the third metal electrode 61: The process flow is the same as that for preparing the first metal electrode 41; the first monolayer graphene 43, the second monolayer graphene 44, the dielectric insulating layer 45, the first metal electrode 41 and the second metal electrode 42 constitute the graphene capacitor 4; the first monolayer graphene 43, the third monolayer graphene 62, the dielectric insulating layer 63, the first metal electrode 41 and the third metal electrode 61 constitute the graphene capacitor 6.

[0052] 9. A polymer waveguide core layer with the same structural thickness as the polymer waveguide core layer 3 is prepared on the polymer waveguide core layer 3 using a spin coating process combined with an inductively coupled plasma etching machine; the polymer waveguide upper cladding material is spin-coated onto the polymer waveguide core layer 3 and the polymer waveguide lower cladding 2 using a spin coating process at a speed of 3500 rpm, and then placed at 140℃ for baking for 3 hours to prepare a polymer waveguide upper cladding 5 with a thickness of 18 μm; a certain area of ​​the polymer waveguide lower cladding 2 is exposed on both sides of the polymer waveguide upper cladding 5 to form a stepped structure, thereby preparing a mode-insensitive optical switch based on an organic polymer waveguide.

Claims

1. A mode-insensitive optical switch based on an organic polymer waveguide, characterized in that: From bottom to top, it consists of a substrate (1), a polymer waveguide lower cladding (2), a rectangular polymer waveguide core layer (3), a polymer waveguide upper cladding (5), a first graphene capacitor (4), and a second graphene capacitor (6); the polymer waveguide lower cladding (2) is fabricated on the substrate (1), the polymer waveguide upper cladding (5) is fabricated on the polymer waveguide lower cladding (2), and the rectangular polymer waveguide core layer (3) is encased within the polymer waveguide lower cladding (2) and the polymer waveguide upper cladding (5); the polymer waveguide upper cladding (5) and the polymer waveguide lower cladding (6) 2) A stepped structure is formed between them, and a certain area of ​​the polymer waveguide lower cladding (2) is exposed on the left and right sides of the polymer waveguide upper cladding (5); the first graphene capacitor (4) and the second graphene capacitor (6) are located inside the polymer optical waveguide core layer (3), both of which are double-layer graphene structures, and are at the same horizontal position with a certain distance; the first graphene capacitor (4) consists of the lower first single-layer graphene (43), the middle first dielectric insulating layer (45), the upper second single-layer graphene (44), the first metal contact electrode (41), and the second metal contact electrode. The first graphene capacitor (6) is composed of a lower layer of first monolayer graphene (43), a middle layer of second dielectric insulating layer (63), an upper layer of third monolayer graphene (62), and a third metal contact electrode (61). A first graphene narrow strip with an integral structure of the first monolayer graphene (43) is provided on the right side of the first monolayer graphene (43), and a polymer waveguide cladding (5) extends to the right of the first graphene narrow strip. A first metal contact electrode (41) is prepared on the surface of the first graphene narrow strip. A first metal contact electrode (41) with an integral structure of the first monolayer graphene (43) is provided on the right side of the second monolayer graphene (44). A second graphene narrow strip with an integral structure of two monolayer graphene (44) is formed. The second graphene narrow strip extends to the right out of the polymer waveguide cladding (5). A second metal contact electrode (42) is formed on the second graphene narrow strip. The first graphene narrow strip and the second graphene narrow strip are separated by the polymer waveguide cladding (5). A third graphene narrow strip with an integral structure of the third monolayer graphene (62) is provided on the left side of the third monolayer graphene (62). The third graphene narrow strip extends to the left out of the polymer waveguide cladding (5). A third metal contact electrode (61) is formed on the surface of the third graphene narrow strip.

2. The mode-insensitive optical switch based on an organic polymer waveguide as described in claim 1, characterized in that: The substrate (1) is made of silicon dioxide, silicon nitride, or silicon; the polymer waveguide lower cladding (2) and the polymer waveguide upper cladding (5) are made of the same material, namely EpoClad, polymethyl methacrylate, polyethylene, polyester, or polystyrene; the polymer optical waveguide core layer (3) is made of SU-8 2002, SU-8 2005, polycarbonate, or polyimide.

3. The mode-insensitive optical switch based on an organic polymer waveguide as described in claim 1, characterized in that: The substrate (1) has a width of 1~3 mm and a thickness of 300~800 μm; the lower cladding (2) of the polymer waveguide has the same width as the substrate, which is 1~3 mm, and a thickness of 10~20 μm; the upper cladding (5) of the polymer waveguide has a width of 100~1500 μm and a thickness of 15~20 μm, and the width of the upper cladding (5) of the polymer waveguide is smaller than the width of the lower cladding (2) of the polymer waveguide; the core layer (3) of the polymer optical waveguide has a width of 5~15 μm and a thickness of 5~15 μm.

4. The mode-insensitive optical switch based on an organic polymer waveguide as described in claim 1, characterized in that: The first monolayer graphene (43), the second monolayer graphene (44), and the third monolayer graphene (62) are parallel to the surface of the substrate (1) and have the same thickness of 0.35~0.7nm. The effective width of the first graphene capacitor (4) and the second graphene capacitor (6) is 5~15μm and they are buried inside the polymer waveguide core layer (3). The first graphene capacitor (4) and the second graphene capacitor (6) share the first monolayer graphene (43). The first monolayer graphene (43) is located on the upper surface of the polymer waveguide lower cladding (2). The second monolayer graphene (44) and the third monolayer graphene (62) are located in the same plane. The spacing between the first graphene capacitor (4) and the second graphene capacitor (6) inside the polymer waveguide core layer (3) is 0.1~2μm.

5. A mode-insensitive optical switch based on an organic polymer waveguide as described in claim 1, characterized in that: The dielectric insulating layer is made of one of aluminum oxide, hexagonal boron nitride, or silicon dioxide, with a thickness of 5-20 nm. The dielectric insulating layer is buried between the double-layer graphene of each graphene capacitor, and its width is the same as the effective width of each graphene capacitor.

6. The mode-insensitive optical switch based on an organic polymer waveguide as described in claim 1, characterized in that: The materials of the first metal contact electrode (41), the second metal contact electrode (42) and the third metal contact electrode (61) are alloys composed of one or more metals selected from silver, gold, aluminum and platinum. The distance between each electrode and the center of the polymer optical waveguide core layer (3) is 100~800μm. Along the length direction, the first metal contact electrode (41) and the second metal contact electrode (42) are staggered by a certain distance and do not contact each other. The electrodes have the same width of 50~100μm, the same thickness of 100~300nm and the same length of 50~100μm.

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