A variable optical attenuator array capable of suppressing optical crosstalk between adjacent channels

Abstract

An adjustable optical attenuator array capable of suppressing optical crosstalk between adjacent channels belongs to the technical field of integrated optical waveguide devices. It is composed of a silicon wafer substrate, a polymer lower cladding, a polymer optical waveguide core layer array, and a polymer upper cladding. The polymer optical waveguide core layer array is a four-channel structure. The structure is composed of an input straight waveguide, a first tapered waveguide, a Y-branch power coupler, a mutually parallel first and second modulation arm waveguides, a Y-branch power coupler, a fourth tapered waveguide, and an output straight waveguide in sequence along the signal light input direction. The curved waveguide of the Y-branch power coupler, the fourth tapered waveguide, and the output straight waveguide are separated by a graphene oxide layer. The present invention utilizes the strong light absorption properties of the graphene oxide layer to absorb the light emitted from the output Y-branch coupler between adjacent channels in the adjustable optical attenuator array, thereby suppressing optical crosstalk between adjacent channels in the array and improving light transmission efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated optical waveguide devices, and specifically relates to an adjustable optical attenuator array capable of suppressing optical crosstalk between adjacent channels, which uses a silicon wafer as a substrate, an organic polymer material with a high thermo-optical coefficient as a polymer optical waveguide core layer, an upper cladding layer, and a lower cladding layer, and graphene oxide as an isolation waveguide. Background Art

[0002] In recent years, with the widespread adoption of the Internet and the rapid development of information technology, backbone network traffic has increased significantly. Fiber-optic communications, known for their wide transmission bandwidth, low loss, strong confidentiality, long relay distances, and high reliability, have experienced rapid development and demonstrated their unparalleled superiority. This, in turn, places increasing demands on the bandwidth and capacity of communication networks. To expand the channel capacity of optical networks, dense wavelength division multiplexing (DWDM) technology has emerged and has become the primary means of achieving high-speed, high-capacity fiber-optic communications. To achieve long-distance, high-speed, error-free transmission in DWDM systems, the optical power of each channel must be consistent. This requires monitoring and equalizing the optical power of multiple channels to achieve gain flattening, dynamic gain balancing, and transmission power equalization. Numerous equalization schemes have been proposed, primarily including optical devices such as dynamic channel equalizers (DCEs), variable-power optical multiplexers (VMUXs), and optical add-drop multiplexers (OADMs). The core component of these devices is the variable optical attenuator array. Adjustable optical attenuator arrays play an important role in wavelength division multiplexing fiber optic networks. Flexible adjustment of the adjustable optical attenuator array can make the power of each channel at an ideal level. Therefore, the development of high-performance adjustable optical attenuator arrays has received great attention.

[0003] Variable optical attenuators based on planar waveguide structures offer advantages such as small size, ease of integration, and excellent stability. Organic polymer materials, in particular, offer significant advantages such as high thermo-optical coefficients, low thermal conductivity, low cost, and a wide variety of materials. These materials hold significant promise for application in array integration. If the waveguide structure is properly designed, crosstalk between optical transmission channels can be reduced to negligible levels. However, for variable optical attenuator arrays based on the thermo-optic effect, electrodes must be fabricated on the modulator arm waveguides. Heating these electrodes modulates the refractive index of the modulator arm waveguide material to achieve optical attenuation. This thermal tuning process can cause optical or thermal crosstalk between adjacent channels, compromising their attenuation performance. In particular, in variable optical attenuator arrays based on the Mach–Zehnder interferometer (MZI) structure, when power attenuation is achieved by thermally tuning one unit, the optical field at the output Y-branch coupler can be diffused into the cladding due to interference effects, affecting the optical power of adjacent channels and severely impacting the performance of the variable optical attenuator array. Summary of the Invention

[0004] In order to overcome the shortcomings of the traditional variable optical attenuator array and suppress the optical crosstalk between adjacent channels, the object of the present invention is to provide a variable optical attenuator array capable of suppressing the optical crosstalk between adjacent channels.

[0005] Graphene oxide (GO) has excellent optical properties, with a complex refractive index of 1.95 + 0.11i. The imaginary part of the complex refractive index of GO represents its good light absorption properties. Therefore, the present invention chooses to use a GO layer to suppress optical crosstalk between adjacent channels.

[0006] As attached Figure 1FIG. 1 is a schematic diagram of the structure of the variable optical attenuator unit device constituting the variable optical attenuator array of the present invention, which is composed of a silicon wafer substrate 23, a polymer lower cladding layer 24 prepared on the silicon wafer substrate 23, a polymer optical waveguide core layer prepared on the polymer lower cladding layer 24, and a polymer upper cladding layer 24′ prepared on the polymer lower cladding layer 24 and the polymer optical waveguide core layer. The polymer optical waveguide core layer is coated in the polymer upper cladding layer 24′; wherein the polymer optical waveguide core layer is an optical waveguide structure based on MZI, and is arranged along the signal light input direction. The input straight waveguide 1, the first tapered waveguide 2 with a width gradually narrowing, the first strip waveguide 3, the second tapered waveguide 4 with a width gradually widening, the second strip waveguide 5, the first curved waveguide 6, the second curved waveguide 7, the mutually parallel first modulation arm waveguide 8 and the second modulation arm waveguide 9, the mutually parallel first modulation electrode 10 and the second modulation electrode 10', the third curved waveguide 11, the fourth curved waveguide 12, the third strip waveguide 13, the third tapered waveguide 14 with a width gradually narrowing, the fourth strip waveguide 15, the width gradually widening The signal light passes through the second tapered waveguide 4 and the second strip waveguide 5 in sequence and is divided into two beams, one beam is transmitted in the first curved waveguide 6, and the other beam is transmitted in the second curved waveguide 7. The second tapered waveguide 4, the second strip waveguide 5, the first curved waveguide 6 and the second curved waveguide 7 constitute a Y-branch power splitter. The two beams of light transmitted in the third curved waveguide 11 and the fourth curved waveguide 12 are coupled into the third strip waveguide 13 and then input into the third tapered waveguide 14. The third curved waveguide 11. The fourth curved waveguide 12, the third strip waveguide 13, and the third tapered waveguide 14 constitute a Y-branch power coupler; light is input from the input straight waveguide 1, passes through the first tapered waveguide 2 and the first strip waveguide 3 in sequence, and then is split into two beams of equal power by the Y-branch power splitter, which enter the first modulation arm waveguide 8 and the second modulation arm waveguide 9 respectively. The two beams of light are then coupled by the Y-branch power coupler and input into the fourth strip waveguide 15. Finally, they are output from the output straight waveguide 17 through the fourth tapered waveguide 16.

[0007] The input straight waveguide 1 and the output straight waveguide 17 have the same length, L0 = 300-600 μm; the first tapered waveguide 2 and the fourth tapered waveguide 16 have the same length, L1 = 100-400 μm; the first strip waveguide 3 and the fourth strip waveguide 15 have the same length, L2 = 200-500 μm; the second tapered waveguide 4 and the third tapered waveguide 14 have the same length, L3 = 500-800 μm; the second strip waveguide 5 and the third strip waveguide 13 have the same length, L4 = 80-120 μm; the first curved waveguide 6, the second curved waveguide 7, the third curved waveguide 11, and the fourth curved waveguide 12 have the same length, L5 = 2500-3000 μm; and the first modulation arm waveguide 8, the second modulation arm waveguide 9, the first modulation electrode 10, and the second modulation electrode 10′ have the same length, L6 = 0.5 cm-1.5 cm.

[0008] The width of the input straight waveguide 1, the wide side width of the first tapered waveguide 2, the width of the first curved waveguide 6, the width of the second curved waveguide 7, the width of the first modulation arm waveguide 8, the width of the second modulation arm waveguide 9, the width of the third curved waveguide 11, the width of the fourth curved waveguide 12, the wide side width of the fourth tapered waveguide 16, and the width of the output straight waveguide 17 are all equal to W0 = 3 to 5 μm. The narrow side width of the first tapered waveguide 2, the narrow side width of the first strip waveguide 3, the narrow side width of the second tapered waveguide 4, the narrow side width of the third tapered waveguide 14, the narrow side width of the fourth strip waveguide 15 The width of the first modulation arm waveguide 8 and the narrow side width of the fourth tapered waveguide 16 are equal to W1 = 3~4 μm, the wide side width of the second tapered waveguide 4, the width of the second strip waveguide 5, the width of the third strip waveguide 13 and the wide side width of the third tapered waveguide 14 are equal to W2 = 8~12 μm, the width of the first modulation electrode 10 and the second modulation electrode 10' are equal to W3 = 10~15 μm, and the distance between the center lines of the first modulation arm waveguide 8 and the second modulation arm waveguide 9 and between the center lines of the first modulation electrode 10 and the second modulation electrode 10' is W4 = 50~60 μm.

[0009] An adjustable optical attenuator array capable of suppressing optical crosstalk between adjacent channels, as shown in the attached Figure 2 As shown, from bottom to top, it consists of a silicon wafer substrate 23, a polymer lower cladding layer 24 prepared on the silicon wafer substrate 23, a polymer optical waveguide core layer array prepared on the polymer lower cladding layer 24, and a polymer upper cladding layer 24' prepared on the polymer lower cladding layer 24 and the polymer optical waveguide core layer array, and the polymer optical waveguide core layer array is coated in the polymer upper cladding layer 24'; the characteristic is that the polymer optical waveguide core layer array is a four-channel structure, consisting of four first adjustable optical attenuator unit devices 18, second adjustable optical attenuator unit devices 19, third adjustable optical attenuator unit devices 20 and fourth adjustable optical attenuator unit devices 21 with the same structure, and the structure diagram of each adjustable optical attenuator unit device is as shown in the attached figure. Figure 1As shown; the distance between the center lines of the output straight waveguide 17 or the input straight waveguide 1 of each two adjustable optical attenuator unit devices is 127-135 μm, and the third tapered waveguide 14, the fourth strip waveguide 15, the fourth tapered waveguide 16 and the output straight waveguide 17 of each two adjustable optical attenuator unit devices are separated by graphene oxide layers 22, 22', 22", and the width of each graphene oxide layer 22, 22', 22" is equal to 30-40 μm;

[0010] As attached Figure 3 As shown, Figure 2 A cross-sectional view of the Y-branch coupler at the output end of the variable optical attenuator array at position AA' shows, from bottom to top, a silicon wafer substrate 23, a polymer lower cladding layer 24 formed on the silicon wafer substrate 23, a polymer optical waveguide core layer 25 formed on the polymer lower cladding layer 24 (the polymer optical waveguide core layer 25 here corresponds to the third tapered waveguide 14), and a polymer upper cladding layer 24' formed on the polymer lower cladding layer 24 and the polymer optical waveguide core layer 25. Each two adjacent unit devices are separated by a first graphene oxide layer 22, a second graphene oxide layer 22', and a third graphene oxide layer 22".

[0011] The thickness of the silicon wafer substrate 23 is 0.5 to 1 mm, the thickness of the polymer lower cladding layer 24 is 7 to 9 μm, the thickness of the polymer optical waveguide core layer 25 is 3 to 6 μm, the thickness of the polymer upper cladding layer 24' (the thickness above the polymer optical waveguide core layer 25) is 3 to 6 μm, and the thickness of the graphene oxide layers 22, 22', and 22" (equal to the sum of the thicknesses of the polymer lower cladding layer 24, the polymer optical waveguide core layer 25, and the polymer upper cladding layer 24') is equal to 13 to 21 μm.

[0012] As attached Figure 4 As shown, Figure 2 A cross-sectional view of the adjustable optical attenuator array at position BB' shows, from bottom to top, a silicon wafer substrate 23, a polymer lower cladding 24 formed on the silicon wafer substrate 23, a polymer optical waveguide core layer 25 formed on the polymer lower cladding 24 (the polymer optical waveguide core layer 25 here corresponds to the first modulation arm waveguide 8 and the second modulation arm waveguide 9), and a polymer upper cladding 24' formed on the polymer optical waveguide core layer 25 and the polymer lower cladding 24; a first modulation electrode 10 and a second modulation electrode 10' are formed on the polymer upper cladding 24' at positions corresponding to the first modulation arm waveguide 8 and the second modulation arm waveguide 9.

[0013] The thickness of the silicon wafer substrate 23 is 0.5 to 1 mm, the thickness of the polymer lower cladding 24 is 7 to 9 μm, the thickness of the polymer optical waveguide core layer 25 is 3 to 6 μm, the thickness of the polymer upper cladding 24' (the thickness above the polymer optical waveguide core layer 25) is 3 to 6 μm, and the thickness of the first modulation electrode 10 and the second modulation electrode 10' are equal to 20 to 25 nm.

[0014] As attached Figure 5 As shown, Figure 2 The cross-sectional view of the variable optical attenuator array at position C-C' shows, from bottom to top, a silicon wafer substrate 23, a polymer lower cladding layer 24 formed on the silicon wafer substrate 23, a polymer optical waveguide core layer 25 formed on the polymer lower cladding layer 24 (the polymer optical waveguide core layer 25 here corresponds to the second tapered waveguide 4), and a polymer upper cladding layer 24' formed on the polymer optical waveguide core layer 25 and the polymer lower cladding layer 24.

[0015] The thickness of the silicon wafer substrate 23 is 0.5-1 mm, the thickness of the polymer lower cladding layer 24 is 7-9 μm, the thickness of the polymer optical waveguide core layer 25 is 3-6 μm, and the thickness of the polymer upper cladding layer 24 ′ (the thickness above the polymer optical waveguide core layer 25 ) is 3-6 μm.

[0016] The process flow of the method for preparing the adjustable optical attenuator array of the present invention is shown in the attached Figure 6 , specifically described as follows:

[0017] A: Cleaning of silicon wafer substrates

[0018] Repeatedly wipe the silicon wafer substrate 23 with a cotton ball soaked in acetone, then repeatedly wipe the silicon wafer substrate 23 with a cotton ball soaked in ethanol, then rinse it with deionized water, blow it dry with nitrogen, place it in a clean culture dish and seal it;

[0019] B: Preparation of polymer lower cladding

[0020] A polymer lower cladding material (the polymer lower cladding material is a series of organic polymer materials with good transparency, including Epoclad, polymethyl methacrylate (PMMA), polycarbonate (PC), polyimide (PI), polyethylene (PE), polyester (PET), polystyrene (PS), etc.) is spin-coated on a cleaned silicon wafer substrate 23 using a spin coating process at a spin coating speed of 2000 to 5000 rpm, and then heated at 120 to 150° C. for 5 to 10 minutes. The entire substrate is then exposed to ultraviolet light with a wavelength of 360 to 400 nm and an exposure light power of 17 to 18 mW for 15 to 25 seconds, and then heated at 120 to 150° C. for 20 to 40 minutes. The resulting polymer lower cladding layer 24 has a thickness of 7 to 9 μm.

[0021] C: Preparation of polymer optical waveguide core layer

[0022] A polymer optical waveguide core layer material with a negative thermo-optical coefficient (the optical waveguide core layer is a series of wet-etchable UV negative photoresist materials including EpoCore, EpoClad, SU-82002, and SU-82005, and the refractive index of the optical waveguide core layer material is higher than the refractive index of the polymer upper cladding layer) is spin-coated on the polymer lower cladding layer 24 to form a polymer film. The rotation speed is 3000 to 5000 rpm, and the thickness of the polymer film is 3 to 6 μm. The spin-coated polymer film is then pre-baked, that is, heated at 50 to 70° C. for 2 to 5 minutes using a step-by-step heating method, and then heated at 90 to 120° C. for 1 to 4 minutes. After heating, the polymer film is photolithographically aligned under ultraviolet light with a wavelength of 360 to 400 nm. The waveguide mask is aligned with the polymer optical waveguide core layer of the variable optical attenuator array to be prepared (such as Figure 2 The structure is complementary, and the exposure time is 8 to 16 seconds, so that the polymer film material within the core structure of the polymer optical waveguide of the variable optical attenuator array to be prepared is exposed to ultraviolet light; after the photolithography is completed, it is removed from the photolithography machine for intermediate baking, that is, heating at 50 to 70 ° C for 2 to 5 minutes, and then heating at 85 to 95 ° C for 4 to 8 minutes, and then cooling at room temperature for 1 to 2 hours after the heating is completed; after the cooling is completed, it is developed, that is, first wet-etching in the developer corresponding to the polymer optical waveguide core material for 15 to 40 seconds, and the unexposed variable optical attenuator array polymer is removed. The polymer film outside the polymer optical waveguide core layer structure is removed, and then the polymer film and developer remaining on the surface of the polymer lower cladding layer 24 are washed away in an isopropyl alcohol solution. The polymer lower cladding layer 24 is then repeatedly rinsed with deionized water (rinsing should be done in the direction of the waveguide to prevent damage to the waveguide) to remove the isopropyl alcohol on the surface of the polymer lower cladding layer 24, and then dried with nitrogen. Finally, the film is post-baked, i.e., heated at 120° C. to 150° C. for 30 to 60 minutes, and then cooled to room temperature for 1 to 2 hours. In this way, the polymer optical waveguide core layer 25 is prepared on the polymer lower cladding layer 24.

[0023] D: Preparation of polymer upper cladding

[0024] A polymer upper cladding material (the polymer upper cladding material is a series of organic polymer materials with good transparency including Epoclad, polymethyl methacrylate (PMMA), polycarbonate (PC), polyimide (PI), polyethylene (PE), polyester (PET), polystyrene (PS), etc.) is spin-coated on the polymer lower cladding layer 24 and the polymer optical waveguide core layer 25 by a spin coating process at a spin coating speed of 2000 to 3000 rpm. The polymer upper cladding layer 24 and the polymer optical waveguide core layer 25 are then heated at 120 to 150° C. for 5 to 10 minutes, and then the entire layer is exposed to ultraviolet light with a wavelength of 360 to 400 nm and an exposure light power of 17 to 18 mW for 15 to 25 seconds. Finally, the polymer upper cladding layer 24′ is prepared on the polymer lower cladding layer 24 and the polymer optical waveguide core layer 25. The thickness of the polymer upper cladding layer 24′ on the polymer optical waveguide core layer 25 is 3 to 6 μm.

[0025] E: Evaporated aluminum film

[0026] A 50-150 nm thick Al film is deposited on the polymer upper cladding layer 24' by evaporation, and then a positive photoresist BP212 film is prepared on the Al film by spin coating at a rotation speed of 2000-3000 rpm; the spin-coated photoresist BP212 film is pre-baked, that is, heated at 80-100° C. for 20-30 minutes, and then cooled at room temperature for 1-2 hours to obtain a photoresist BP212 film with a thickness of 0.5-2.0 μm; the photoresist BP212 film is subjected to plate alignment photolithography under ultraviolet light with a wavelength of 360-400 nm, and the mask plate has the same structure as the graphene oxide layer to be prepared (such as Figure 2 As shown), the exposure time is 2 to 10 seconds, so that the photoresist BP212 film in the area outside the graphene oxide layer is exposed; the exposed silicon wafer substrate 23 is placed in a NaOH solution with a mass concentration of 3 to 5‰ for 8 to 30 seconds to remove the unexposed photoresist, then rinsed with deionized water and blown dry with nitrogen; the exposed photoresist BP212 film is hardened, that is, heated at 80 to 100°C for 10 to 20 minutes, and cooled at room temperature for 1 to 2 hours after heating; after cooling to room temperature, the Al film is developed, that is, the silicon wafer substrate after the vertical film is placed in a NaOH solution with a mass concentration of 3 to 5‰ for 1 to 20 minutes, the Al film portion without the photoresist mask in the area within the graphene oxide layer is removed, repeatedly rinsed with deionized water, blown dry with nitrogen, and finally the silicon wafer substrate is placed in ethanol for 5 to 10 seconds to remove the unexposed photoresist BP212 film on the Al film, rinsed with deionized water, and then blown dry with nitrogen;

[0027] F: ICP etching and doping with graphene oxide

[0028] A groove is etched in a position without an Al film by an ICP etching technique (the etching depth penetrates the polymer upper cladding layer and the polymer lower cladding layer and reaches the surface of the silicon wafer substrate), and the Al film is then etched away by chemical etching (i.e., placing it in a NaOH solution with a mass concentration of 3-5‰ for 1-20 minutes); a graphene oxide layer is then incorporated into the etched groove by a spin coating technique at a spin coating speed of 3000-5000 rpm, and then heated at 120-150° C. for 3-8 minutes, and the entire layer is exposed to ultraviolet light with a wavelength of 360-400 nm and an exposure light power of 17-18 mW for 15-25 seconds, and heated at 120-150° C. for 30-50 minutes, ultimately obtaining a graphene oxide layer with a thickness of 13-21 μm (the sum of the thicknesses of the polymer lower cladding layer, the polymer optical waveguide core layer, and the polymer upper cladding layer on the silicon wafer substrate);

[0029] H: Preparation of modulation electrode

[0030] A metal film (which may be an Al film) with a thickness of 20 to 25 nm is deposited on the polymer upper cladding layer 24' by an evaporation process, and then a positive photoresist BP212 film is prepared on the Al film by a spin coating process at a rotation speed of 2000 to 3000 rpm; the spin-coated photoresist BP212 film is pre-baked, that is, heated at a temperature of 80°C to 100°C for 20 to 30 minutes, and then cooled at room temperature for 1 to 2 hours to obtain a BP212 film with a thickness of 0.5 to 2.0 μm; the photoresist BP212 film is subjected to plate alignment photolithography under ultraviolet light with a wavelength of 360 to 400 nm, and the mask plate has the same structure as the modulation electrode to be prepared (such as Figure 2 As shown), the exposure time is 2 to 10 seconds, so that the photoresist BP212 film in the area other than the modulation arm electrode and its electrode pin is exposed; the exposed silicon wafer is placed in a NaOH solution with a mass concentration of 3 to 5‰ for 8 to 30 seconds to remove the unexposed photoresist, then rinsed with deionized water and blown dry with nitrogen; the exposed photoresist BP212 film is hardened, that is, heated at 80 to 100°C for 10 to 20 minutes, and cooled at room temperature for 1 to 2 hours after heating; after cooling to room temperature, the Al electrode is developed, that is, the hardened silicon wafer is placed in a NaOH solution with a mass concentration of 3 to 5‰ for 1 to 20 minutes, the Al film portion of the area other than the modulation arm electrode and its electrode pin is removed, repeatedly rinsed with deionized water, and blown dry with nitrogen; finally, the silicon wafer substrate is placed in ethanol for 5 to 10 seconds to remove the unexposed photoresist BP212 film on the Al electrode, then rinsed with deionized water, and blown dry with nitrogen, thereby obtaining the variable optical attenuator array of the present invention.

[0031] Compared with other adjustable optical attenuator arrays, the present invention has the following advantages:

[0032] The graphene oxide used in this invention exhibits excellent optical properties. Its strong light absorption properties absorb light emitted from adjacent channels in a variable optical attenuator array at the output Y-branch coupler, thereby suppressing optical crosstalk between adjacent channels in the array and improving light transmission efficiency. Furthermore, the use of polymer materials simplifies the device's fabrication process, requiring only conventional processes such as spin coating and photolithography, rather than more complex ones. Furthermore, the device boasts low production costs, high efficiency, and is amenable to large-scale mass production. Furthermore, it can be applied to practical variable optical attenuator arrays. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 : A schematic structural diagram of the variable optical attenuator unit device according to the present invention;

[0034] Figure 2 : A schematic structural diagram of a four-channel variable optical attenuator array using a graphene oxide layer as an isolation waveguide according to the present invention;

[0035] Figure 3 : Figure 2 Schematic diagram of the cross section at the A-A' position;

[0036] Figure 4 : Figure 2 Schematic diagram of the cross section at the B-B' position;

[0037] Figure 5 : Figure 2 Schematic diagram of the cross section at the C-C' position;

[0038] Figure 6 : Flowchart of the fabrication process of a variable optical attenuator array using a graphene oxide layer;

[0039] Figure 7 : Simulated cross-sectional thermal field distribution of the thermo-optical region of a variable optical attenuator array without a graphene oxide layer;

[0040] Figure 8 : A simulated diagram of the cross-sectional thermal field distribution in the thermo-optical region of a variable optical attenuator array using a graphene oxide layer;

[0041] Figure 9 : Schematic diagram of the crosstalk effect caused by changes in the electric power applied to the electrodes of any unit device in a variable optical attenuator array using a graphene oxide layer on the unit devices on its left and right sides;

[0042] like Figure 1As shown in the figure, the names of the various parts are: input straight waveguide 1, first tapered waveguide 2, first strip waveguide 3, second tapered waveguide 4, second strip waveguide 5, first curved waveguide 6, second curved waveguide 7, parallel first modulation arm waveguide 8 and second modulation arm waveguide 9, parallel first modulation electrode 10 and second modulation electrode 10', third curved waveguide 11, fourth curved waveguide 12, third strip waveguide 13, third tapered waveguide 14, fourth strip waveguide 15, fourth tapered waveguide 16, output straight waveguide 17; silicon wafer substrate 23, polymer cladding (composed of polymer lower cladding 24 and polymer upper cladding 24');

[0043] like Figure 2 As shown, the names of the components are: a first adjustable optical attenuator unit device 18, a second adjustable optical attenuator unit device 19, a third adjustable optical attenuator unit device 20, a fourth adjustable optical attenuator unit device 21, a first graphene oxide layer 22, a second graphene oxide layer 22', a third graphene oxide layer 22", a first modulation electrode 10, a second modulation electrode 10'; a silicon wafer substrate 23, and a polymer cladding (composed of a polymer lower cladding layer 24 and a polymer upper cladding layer 24');

[0044] like Figure 3 As shown, the names of the components are: silicon wafer substrate 23, polymer lower cladding layer 24, polymer optical waveguide core layer 25, polymer upper cladding layer 24', first graphene oxide layer 22, second graphene oxide layer 22', and third graphene oxide layer 22".

[0045] like Figure 4 As shown, the names of the various parts are: silicon wafer substrate 23, polymer lower cladding layer 24, polymer optical waveguide core layer 25, polymer upper cladding layer 24', first modulation electrode 10, second modulation electrode 10';

[0046] like Figure 5 As shown, the names of the various parts are: silicon wafer substrate 23, polymer lower cladding layer 24, polymer optical waveguide core layer 25, and polymer upper cladding layer 24'.

[0047] like Figure 6 As shown in the figure, 23 is a silicon wafer substrate, 24 is a polymer lower cladding layer prepared by spin coating technology, 25 is a polymer optical waveguide core layer prepared by spin coating, photolithography, and wet etching technology, 24' is a polymer upper cladding layer prepared by spin coating technology, 22 is a graphene oxide layer prepared by ICP etching and spin coating technology, 27 is the Al film described in step E, and 26 is a BP212 thin film;

[0048] like Figure 7 As shown, it can be seen that when the unit device on the left without the graphene oxide layer is modulated, a large amount of heat will be dissipated, thereby affecting the power consumption and output efficiency of the unit device on the right.

[0049] like Figure 8 As shown, it can be seen that the graphene oxide layer effectively absorbs the heat loss caused by the unit device on the left, thereby effectively reducing the crosstalk caused to the unit device on the right.

[0050] like Figure 9 As shown in FIG. 1 , when the second adjustable optical attenuator unit device 19 is modulated, as the electric power applied to the modulation electrode on its modulation arm increases, the crosstalk curve caused to the first adjustable optical attenuator unit device 18 on its left and the third adjustable optical attenuator unit device 20 on its right is significantly reduced after the graphene oxide layer is adopted. It can be seen that the crosstalk entering the adjacent channel is significantly reduced to below -60 dB. DETAILED DESCRIPTION

[0051] Example 1

[0052] The present invention will be further described below with reference to the accompanying drawings and examples.

[0053] The embodiment structure is as follows Figure 1 As shown, the length L0 of the input straight waveguide 1 and the output straight waveguide 17 is 500 μm, the length L1 of the first tapered waveguide 2 and the fourth tapered waveguide 16 is 300 μm, the length L2 of the first strip waveguide 3 and the fourth strip waveguide 15 is 400 μm, the length L3 of the second tapered waveguide 4 and the third tapered waveguide 14 is 700 μm, the length L4 of the second strip waveguide 5 and the third strip waveguide 13 is 100 μm, the length L5 of the first curved waveguide 6, the second curved waveguide 7, the third curved waveguide 11 and the fourth curved waveguide 12 is 2700 μm, and the length L6 of the first modulation arm waveguide 8, the second modulation arm waveguide 9, the first modulation electrode 10 and the second modulation electrode 10 ′ is 1 cm.

[0054] The width of the input straight waveguide 1, the wide side width of the first tapered waveguide 2, the width of the first curved waveguide 6, the width of the second curved waveguide 7, the width of the mutually parallel first modulation arm waveguide 8 and the width of the second modulation arm waveguide 9, the width of the third curved waveguide 11, the width of the fourth curved waveguide 12, the wide side width of the fourth tapered waveguide 16, and the width W0 of the output straight waveguide 17 are 4 μm, the narrow side width of the first tapered waveguide 2, the width of the first strip waveguide 3, the narrow side width of the second tapered waveguide 4, the width of the third curved waveguide 11, the width of the fourth curved waveguide 12, the wide side width of the fourth tapered waveguide 16, and the width W0 of the output straight waveguide 17 are 4 μm. The narrow side width W1 of the tapered waveguide 14, the width of the fourth strip waveguide 15, and the narrow side width W1 of the fourth tapered waveguide 16 are 3.5 μm, the wide side width W2 of the second tapered waveguide 4, the width of the second strip waveguide 5, the width of the third strip waveguide 13, and the wide side width W2 of the third tapered waveguide 14 are 10 μm, the width W3 of the parallel first modulation electrode 10 and the second modulation electrode 10 ′ is 12 μm, and the distance W4 between the center lines of the first modulation arm waveguide 8 and the second modulation arm waveguide 9 is 55 μm.

[0055] Light is input from the input straight waveguide 1, passes through the first tapered waveguide 2 and the first strip waveguide 3 in sequence, and then is split into two beams of light with equal power by the Y-branch power divider, which enter the first modulation arm waveguide 8 and the second modulation arm waveguide 9 respectively. The two beams of light are then coupled by the Y-branch power coupler and input into the fourth strip waveguide 15, and then output from the output straight waveguide 17 through the fourth tapered waveguide 16.

[0056] The embodiment structure is as follows Figure 2 As shown, the distance between the center lines of the output straight waveguide of the first adjustable optical attenuator unit device 18, the output straight waveguide of the second adjustable optical attenuator unit device 19, the output straight waveguide of the third adjustable optical attenuator unit device 20 and the output straight waveguide of the fourth adjustable optical attenuator unit device 21 is 127 μm.

[0057] The embodiment structure is as follows Figure 3 Shown (for Figure 2 ), from bottom to top are a silicon wafer substrate 23, a polymer lower cladding layer 24 prepared on the silicon wafer substrate 23, a polymer optical waveguide core layer 25 prepared on the polymer lower cladding layer 24, a polymer upper cladding layer 24' prepared on the polymer optical waveguide core layer 25, and a graphene oxide layer 22 prepared between every two adjacent unit devices.

[0058] The thickness of the silicon wafer substrate 23 is 1 mm, the thickness of the polymer lower cladding layer 24 is 7 μm, the thickness of the polymer optical waveguide core layer 25 is 4 μm, the thickness of the polymer upper cladding layer 24 ′ above the polymer optical waveguide core layer 25 is 4 μm, and the thickness of the filled graphene oxide layer 22 is 15 μm.

[0059] The structure of the embodiment is as shown in the attached Figure 4As shown, Figure 2 A cross-sectional view of the adjustable optical attenuator array at position BB' shows, from bottom to top, a silicon wafer substrate 23, a polymer lower cladding layer 24 prepared on the silicon wafer substrate 23, a polymer optical waveguide core layer 25 prepared on the polymer lower cladding layer 24, and a polymer upper cladding layer 24' prepared on the polymer optical waveguide core layer 25; an Al heating electrode 10 is prepared on the polymer upper cladding layer 24' at a position corresponding to the polymer optical waveguide core layer 25.

[0060] The thickness of the silicon wafer substrate 23 is 1 mm, the thickness of the polymer lower cladding layer 24 is 7 μm, the thickness of the polymer optical waveguide core layer 25 is 4 μm, the thickness of the polymer upper cladding layer 24 ′ above the polymer optical waveguide core layer 25 is 4 μm, and the thickness of the Al heating electrode is 23 nm.

[0061] As attached Figure 5 As shown, Figure 2 The cross-sectional view of the variable optical attenuator array at position C-C' shows, from bottom to top, a silicon wafer substrate 23, a polymer lower cladding layer 24 formed on the silicon wafer substrate 23, a polymer optical waveguide core layer 25 formed on the polymer lower cladding layer 24, and a polymer upper cladding layer 24' formed on the polymer optical waveguide core layer 25.

[0062] The thickness of the silicon wafer substrate 23 is 1 mm, the thickness of the polymer lower cladding layer 24 is 7 μm, the thickness of the polymer optical waveguide core layer 25 is 4 μm, and the thickness of the polymer upper cladding layer 24 ′ on the polymer optical waveguide core layer 25 is 4 μm.

[0063] Example 2

[0064] Cleaning of the silicon wafer substrate 23: repeatedly wipe the silicon wafer substrate 23 with a cotton ball soaked in acetone, then repeatedly wipe the silicon wafer substrate 23 with a cotton ball soaked in ethanol, then rinse it with deionized water, blow it dry with nitrogen, put it in a clean culture dish and seal it.

[0065] A polymer lower cladding layer 24 was prepared using a spin coating process: a polymer lower cladding layer (EpoClad) was spin-coated onto a clean silicon wafer substrate 23 at a speed of 2000 rpm, followed by heating at 120°C for 5 minutes. The entire substrate was then exposed for 9 seconds and heated again at 120°C for half an hour. The thickness of the polymer lower cladding layer 24 was 7 μm.

[0066] The polymer optical waveguide core layer 25 of the adjustable optical attenuator array including four adjustable optical attenuator unit devices 18, 19, 20, and 21 with the same structure is prepared by spin coating, photolithography, and wet etching processes: the polymer material EpoCore, which is sensitive to ultraviolet light and has good thermal and optical stability, is spin-coated on a clean polymer material (EpoClad) lower cladding layer by a spin coating process at a rotation speed of 3000 rpm. The silicon wafer substrate with the spin-coated polymer film is pre-baked by heating on a hot plate at 50°C for 2 minutes and then at 90°C for 4 minutes using a step-by-step heating method. After heating, a polymer optical waveguide core layer EpoCore polymer film with a thickness of 4 μm is obtained; the prepared polymer film is photolithographically etched and aligned with the plate in an ultraviolet photolithography machine with a wavelength of 365 nm. The waveguide mask is aligned with the polymer optical waveguide core layer of the adjustable optical attenuator array to be prepared (such as Figure 2 After the photolithography is completed, the film is dried on a hot plate, heated at 50°C for 2 minutes, then heated at 87°C for 4 minutes, and then cooled at room temperature for 1.5 hours; after cooling, the film is developed by wet etching in a developer corresponding to the EpoCore polymer photoresist for 20 seconds to remove the unexposed non-polymer optical waveguide core layer portion, and then placed in an isopropyl alcohol solution to wash away the developer and polymer optical waveguide core layer material remaining on the surface of the polymer lower cladding layer, and then repeatedly rinsed with deionized water (rinsing should be done along the waveguide direction to prevent the waveguide from being damaged), remove the isopropyl alcohol on the surface of the polymer lower cladding layer, and finally blown dry with nitrogen; after the development is completed, the film is post-baked and heated at 120°C for 30 minutes. After heating, the film is cooled at room temperature for 1.5 hours, and the length and width of the polymer optical waveguide core layer are the same as those of the polymer optical waveguide core layer. Figure 2 The same as in the above, thus the polymer optical waveguide core structure is prepared on the lower cladding layer.

[0067] The polymer upper cladding layer 24' was prepared using a spin coating process: the polymer material EpoClad was spin-coated onto the silicon wafer substrate, which had already been fabricated as the polymer optical waveguide core layer, at a spin coating speed of 2000 rpm. The substrate was then heated at 120°C for five minutes. The entire substrate was then exposed to light for 9 seconds and heated again at 120°C for 30 minutes, resulting in a polymer upper cladding layer with a thickness of 4 μm.

[0068] A 100 nm thick Al film was deposited on the polymer upper cladding layer 24' by evaporation, and then a positive photoresist BP212 film was prepared on the Al film by spin coating at a rotation speed of 2500 rpm; the spin-coated photoresist BP212 film was pre-baked, that is, heated at 87°C for 20 minutes, and then cooled at room temperature for 1.5 hours to obtain a 2.0 μm thick BP212 film; the photoresist BP212 film was subjected to plate alignment photolithography under ultraviolet light with a wavelength of 365 nm, and the mask had the same structure as the graphene oxide layer to be prepared (such as Figure 2 As shown, the graphene oxide layer 22 is at the output end between adjacent channels in the variable optical attenuator array), the exposure time is 2.2 seconds, so that the photoresist BP212 film in the area outside the graphene oxide layer 22 is exposed; the exposed silicon wafer substrate is placed in a NaOH solution with a mass concentration of 5‰ for 15 seconds to remove the unexposed photoresist, then rinsed with deionized water and blown dry with nitrogen; the exposed photoresist BP212 film is hardened, that is, heated at 95°C for 10 minutes, and then cooled at room temperature for 1.5 hours; after cooling to room temperature, the Al film is developed, that is, the silicon wafer substrate after the erection film is placed in a NaOH solution with a mass concentration of 5‰ for 10 minutes, the Al film portion of the area outside the graphene oxide layer 22 is removed, repeatedly rinsed with deionized water, blown dry with nitrogen, and finally placed in ethanol for 5 seconds to remove the unexposed photoresist BP212 film on the Al film, then rinsed with deionized water, and finally blown dry with nitrogen;

[0069] Using ICP etching, grooves were etched in the areas without the Al film (to be filled with the graphene oxide layer). The Al film was then removed using a lithography technique. The graphene oxide layer was then doped into the etched grooves using spin coating at 5000 rpm, followed by heating at 120°C for five minutes. The entire layer was then exposed for nine seconds and heated again at 120°C for 30 minutes. The resulting doped graphene oxide had a thickness of 15 μm.

[0070] An Al electrode 10 (10') is prepared by evaporation, photolithography, and wet etching processes: a 100 nm thick Al mask is evaporated on a silicon wafer on which a polymer lower cladding layer, an optical waveguide core layer, and a polymer upper cladding layer are prepared, and then a positive photoresist BP212 film is spin-coated on the Al mask by a spin coating process at a rotation speed of 2230 rpm and a thickness of 2 μm; the spin-coated photoresist BP212 film is pre-baked and then heated at 85° C. for 20 minutes, and then cooled at room temperature for 1.5 hours after heating; photolithography is performed on a photolithography machine, and alignment photolithography is performed under ultraviolet light with a wavelength of 365 nm, and the mask plate has the same structure as the modulation electrode to be prepared (such as Figure 2 shown), dimensions and Figure 2 The first modulation electrode 10 and the second modulation electrode 10' have the same structural dimensions, and the exposure time is 2.2 seconds, so that the area except the modulation arm electrode and its electrode pin is exposed; the photolithographic silicon wafer is removed from the photolithography machine, placed in a NaOH solution with a mass concentration of 5‰ for 15 seconds to remove the floating glue on the surface, rinsed with deionized water, and then blown dry with nitrogen; the photoresist BP212 film is hardened, heated at 95°C for 10 minutes, and then cooled at room temperature for 1.5 hours; after cooling, the Al electrode is developed, and the silicon wafer is placed in a NaOH solution with a mass concentration of 5‰ for 10 minutes to remove the exposed non-electrode part, and then repeatedly rinsed with deionized water and blown dry with nitrogen; placed in ethanol for 5 seconds to remove the photoresist BP212 on the Al electrode, and then rinsed with deionized water, and finally blown dry with nitrogen. The obtained first modulation electrode 10 and second modulation electrode 10' have a length of 1 cm and a width of 12 μm.

[0071] In this way, crosstalk between adjacent channels in a variable optical attenuator array is suppressed by using a graphene oxide layer. It should be noted that the specific embodiments are merely representative examples of the present invention. The technical solution of the present invention is clearly not limited to the above-described embodiments and can be modified in many ways, such as using air slots, quartz substrates, self-assembled microsphere diffraction layers, and increasing the number of attenuator arrays. Anything that is clearly disclosed in the present invention or that can be derived without objection from the written description in the document falls within the scope of protection of this patent.

Claims

1. A variable optical attenuator capable of suppressing optical crosstalk between adjacent channels, characterized in that: From bottom to top, it consists of a silicon wafer substrate, a polymer lower cladding layer prepared on the silicon wafer substrate, a polymer optical waveguide core layer prepared on the polymer lower cladding layer, and a polymer upper cladding layer prepared on the polymer lower cladding layer and the polymer optical waveguide core layer. The polymer optical waveguide core layer is coated in the polymer upper cladding layer, and the refractive index of the polymer optical waveguide core layer is higher than the refractive index of the polymer lower cladding layer and the polymer upper cladding layer. The polymer optical waveguide core layer has a four-channel structure and is composed of four adjustable optical attenuator unit devices with the same structure. The adjustable optical attenuator unit device is an optical waveguide based on MZI. The structure consists of an input straight waveguide, a first tapered waveguide with a width changing from wide to narrow, a first strip waveguide, a second tapered waveguide with a width changing from narrow to wide, a second strip waveguide, a first curved waveguide, a second curved waveguide, a first modulation arm waveguide and a second modulation arm waveguide that are parallel to each other, a third curved waveguide, a fourth curved waveguide, a third strip waveguide, a third tapered waveguide with a width changing from wide to narrow, a fourth strip waveguide, a fourth tapered waveguide with a width changing from narrow to wide, and an output straight waveguide, which is formed on the polymer upper cladding layer and adjacent to the first modulation arm waveguide and the second modulation arm waveguide. The first modulation electrode and the second modulation electrode are prepared at corresponding positions. The third tapered waveguide, the fourth strip waveguide, the fourth tapered waveguide and the output straight waveguide of each two adjustable optical attenuator unit devices are separated by a graphene oxide layer. The signal light passes through the second tapered waveguide and the second strip waveguide in sequence and is divided into two beams, one beam is transmitted in the first curved waveguide, and the other beam is transmitted in the second curved waveguide. The second tapered waveguide, the second strip waveguide, the first curved waveguide and the second curved waveguide constitute a Y-branch power divider. The two beams of light transmitted in the third curved waveguide and the fourth curved waveguide are The light is coupled into the third strip waveguide and then input into the third tapered waveguide. The third curved waveguide, the fourth curved waveguide, the third strip waveguide and the third tapered waveguide constitute a Y-branch power coupler. Light is input from the input straight waveguide, passes through the first tapered waveguide and the first strip waveguide in sequence, and then is split into two beams of light with equal power by the Y-branch power splitter. The two beams enter the first modulation arm waveguide and the second modulation arm waveguide respectively. The two beams are then coupled by the Y-branch power coupler and input into the fourth strip waveguide. Finally, they are output from the output straight waveguide through the fourth tapered waveguide.

2. The variable optical attenuator capable of suppressing optical crosstalk between adjacent channels according to claim 1, wherein: The lengths of the input straight waveguide and the output straight waveguide are equal, namely L0 = 300~600μm; the lengths of the first tapered waveguide and the fourth tapered waveguide are equal, namely L1 = 100~400μm; the lengths of the first strip waveguide and the fourth strip waveguide are equal, namely L2 = 200~500μm; the lengths of the second tapered waveguide and the third tapered waveguide are equal, namely L3 = 500~800μm; the lengths of the second strip waveguide and the third strip waveguide are equal, namely L4 = 80~120μm; the lengths of the first curved waveguide, the second curved waveguide, the third curved waveguide and the fourth curved waveguide are equal, namely L5 = 2500~3000μm; the lengths of the first modulation arm waveguide, the second modulation arm waveguide, the first modulation electrode and the second modulation electrode are equal, namely L6 = 0.5cm~1.5cm.

3. The variable optical attenuator capable of suppressing optical crosstalk between adjacent channels according to claim 1, wherein: The width of the input straight waveguide, the wide side width of the first tapered waveguide, the width of the first curved waveguide, the width of the second curved waveguide, the width of the first modulation arm waveguide and the width of the second modulation arm waveguide, the width of the third curved waveguide, the width of the fourth curved waveguide, the wide side width of the fourth tapered waveguide and the width of the output straight waveguide are equal to W0=3~5μm, the narrow side width of the first tapered waveguide, the narrow side width of the first strip waveguide, the narrow side width of the second tapered waveguide, the narrow side width of the third tapered waveguide, the narrow side width of the fourth strip waveguide The width is equal to the narrow side width of the fourth tapered waveguide, which is W1=3~4μm. The wide side width of the second tapered waveguide, the width of the second strip waveguide, the width of the third strip waveguide and the wide side width of the third tapered waveguide are equal to W2=8~12μm. The width of the first modulation electrode and the second modulation electrode are equal to W3=10~15μm. The distance between the center lines of the first modulation arm waveguide and the second modulation arm waveguide and between the center lines of the first modulation electrode and the second modulation electrode are equal to W4=50~60μm.

4. The variable optical attenuator capable of suppressing optical crosstalk between adjacent channels according to claim 1, wherein: The distance between the center lines of the output straight waveguides or input straight waveguides of each two adjustable optical attenuator unit devices is 127-135 μm, and the width of each graphene oxide layer is equal to 30-40 μm.

5. The variable optical attenuator capable of suppressing optical crosstalk between adjacent channels according to claim 1, wherein: The thickness of the silicon wafer substrate is 0.5~1mm, the thickness of the polymer lower cladding is 7~9μm, the thickness of the polymer optical waveguide core layer is 3~6μm, the thickness of the polymer upper cladding above the polymer optical waveguide core layer is 3~6μm, the thickness of the graphene oxide layer is equal to 13~21μm, and the thickness of the first modulation electrode and the second modulation electrode is equal to 20~25nm.

6. The variable optical attenuator capable of suppressing optical crosstalk between adjacent channels according to claim 1, wherein: The materials of the polymer lower cladding layer and the polymer upper cladding layer are Epoclad, polymethyl methacrylate, polycarbonate, polyimide, polyethylene, polyester or polystyrene, and the material of the polymer optical waveguide core layer is EpoCore, EpoClad, SU-82002 or SU-82005.

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