A method for exciting inter-graphene band plasmons and a prepared device

Abstract

The application provides a method for exciting interband plasmons of double-layer graphene and a prepared device, and belongs to the technical field of optical devices, and comprises the following steps: sequentially laminating a third insulating layer, double-layer graphene and a second insulating layer to form a vertical heterojunction, transferring the vertical heterojunction to a substrate on which a first insulating layer is grown, obtaining a clean initial device substrate through heating separation and solvent cleaning, then preparing a nanoscale metal grating layer on the vertical heterojunction surface of the initial device substrate to form a device intermediate body, and preparing electrodes on the left and right sides of the device intermediate body, so that the electrodes are electrically connected with the double-layer graphene, an electrical regulation channel of the Fermi surface of the double-layer graphene is constructed, and a complete device for exciting interband plasmons is obtained. The nanoscale metal grating array can effectively excite interband plasmons of double-layer graphene, significantly improve the light-plasmon coupling efficiency and realize energy regulation of interband plasmons.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical devices, in particular to a method for exciting interband plasmons of double-layer graphene and a prepared device. BACKGROUND

[0002] In recent years, two-dimensional materials have become the research frontier in the field of plasmonics due to their unique electrical and optical properties. Graphene has become the core candidate material for the development of plasmonic devices because of its wide spectral response from terahertz frequencies to visible light frequencies, subwavelength light field confinement, and strong controllability. Compared with single-layer graphene, double-layer graphene has a tunable band gap and a parabolic-like dispersion characteristic, which can support interband plasmon modes with higher energy, slower group velocity, and in the mid-infrared band. The excitation conditions of this type of interband plasmon can be flexibly adjusted by gate voltage, and it has great application potential in high-performance mid-infrared light modulators, high-sensitivity mid-infrared photodetectors, and other on-chip optoelectronic devices. It has become the main research trend in this field to focus on the efficient excitation and control technology of double-layer graphene interband plasmons.

[0003] Currently, the existing technology mainly relies on two schemes for the excitation of double-layer graphene interband plasmons. The first scheme is the graphene micro / nano structure excitation method, which etches graphene strips to realize plasmon coupling by using the geometric characteristics of micro / nano structures. The second scheme is the metal tip excitation method, which uses the metal tip of a scattering-type scanning near-field optical microscope to couple light energy into double-layer graphene in the near-field range to excite interband plasmons. At the same time, research has shown that there is a significant momentum mismatch between free-space light and double-layer graphene interband plasmons, and direct incident light cannot meet the excitation conditions of interband plasmons. The above two schemes are attempts to solve this problem of momentum mismatch.

[0004] However, the existing excitation schemes still have defects that are difficult to overcome. For the graphene micro / nano structure excitation method, it requires high-precision etching of graphene materials, which is extremely difficult to operate, and problems such as uneven size and rough edges of graphene strips often occur after etching. The organic residue introduced during etching can also seriously contaminate the graphene surface, resulting in a significant reduction in device quality. For the metal tip excitation method, it is highly dependent on the instrument state of the scattering-type scanning near-field optical microscope, which has poor measurement stability and is extremely sensitive to environmental vibrations. Moreover, the presence of the metal tip limits the range of gate voltage control for double-layer graphene, making it difficult to achieve dynamic and adjustable interband plasmon control.

[0005] Therefore, there is an urgent need for a method for exciting interband plasmons of double-layer graphene and a prepared device to solve the problems existing in the prior art and to realize low-cost, high-precision, high-stability, and flexibly adjustable interband plasmon excitation. SUMMARY

[0006] In order to overcome the deficiencies of the prior art, the purpose of the present application is to provide a method for exciting interband plasmons of double-layer graphene and a prepared device, which can effectively excite interband plasmons of double-layer graphene through a nano-scale metal grating array, significantly improve the light-plasmon coupling efficiency and realize the energy regulation of interband plasmons, avoid the micro-nano processing of graphene material itself to prevent the pollution of organic residual glue in the processing process, and do not rely on a scattering type scanning near-field optical microscope, and the whole cost is low, the precision is high, the tuning range is wide, the repeatability is high, which provides a new solution for high-frequency mid-infrared optoelectronic devices, and lays a technical foundation for the application of double-layer graphene in miniaturized and integrated on-chip optoelectronic devices.

[0007] In order to achieve the above-mentioned purpose, the present application provides the following scheme:

[0008] One of the purposes of the present application is to provide a method for exciting interband plasmons of double-layer graphene, comprising the following steps:

[0009] S1, preparing basic materials: preparing double-layer graphene, a second insulating layer, a third insulating layer and a substrate with a first insulating layer, respectively;

[0010] S2, constructing an initial device substrate: according to the pick-up transfer method, the third insulating layer, the double-layer graphene and the second insulating layer are sequentially stacked to form a vertical heterojunction, and then the vertical heterojunction is transferred to the substrate with the first insulating layer, and a clean initial device substrate is obtained through heating separation and solvent cleaning, wherein the initial device substrate comprises, from bottom to top, the substrate, the first insulating layer and the vertical heterojunction;

[0011] S3, preparing a device intermediate: a nano-scale metal grating layer is prepared on the surface of the vertical heterojunction of the initial device substrate to form a device intermediate, wherein the device intermediate comprises, from bottom to top, the substrate, the first insulating layer, the vertical heterojunction and the nano-scale metal grating layer, and the momentum matching between the free space light and the interband plasmons of double-layer graphene is realized through the periodic structure of the nano-scale metal grating layer;

[0012] S4, constructing a complete device: electrodes are prepared on the left and right sides of the device intermediate, so that the electrodes form an electrical connection with the double-layer graphene, an electrical regulation path of the Fermi surface of the double-layer graphene is constructed, and a complete device for exciting interband plasmons is obtained;

[0013] S5, plasmon excitation and regulation: current is passed to the double-layer graphene through the electrodes, and voltage is measured, the Fermi surface of the double-layer graphene is adjusted by applying a gate voltage to the substrate, and mid-infrared light is irradiated, so as to realize the excitation and energy regulation of interband plasmons of the double-layer graphene in the complete device.

[0014] Preferably, in S2, the specific process of the vertical heterostructure is: first, the third insulating layer is transferred and covered on one side surface of the double-layer graphene, and then the second insulating layer is transferred and covered on the other side surface of the double-layer graphene to form a vertical heterojunction; subsequently, the vertical heterojunction is transferred to the substrate on which the first insulating layer is grown, and the clean vertical heterojunction is obtained through heating separation and solvent cleaning.

[0015] Preferably, the double-layer graphene is obtained by a mechanical exfoliation method, and the number of layers is two through the characteristic confirmation of G peak and 2D peak in Raman spectrum testing, and the first insulating layer is a silicon dioxide layer.

[0016] Preferably, in S3, the preparation process of the nanoscale metal grating layer includes: forming a photoresist layer on the surface of the vertical heterojunction, obtaining a grating pattern through exposure, development and fixation, and then forming a nanoscale metal grating layer through plating and stripping process, and the material of the nanoscale metal grating layer is gold.

[0017] Preferably, the preparation of the electrode adopts exposure, development and fixation and plating process, and the material of the electrode includes chromium, palladium and gold.

[0018] The second object of the present application is to provide a device for realizing the above-mentioned method for exciting double-layer graphene interband plasmons, which comprises, from bottom to top, in sequence:

[0019] a substrate;

[0020] a first insulating layer arranged on the upper surface of the substrate;

[0021] a vertical heterojunction arranged on the upper surface of the first insulating layer, which comprises, from bottom to top, in sequence, a second insulating layer, double-layer graphene and a third insulating layer;

[0022] a nanoscale metal grating layer arranged on the upper surface of the third insulating layer and covering the double-layer graphene;

[0023] an electrode arranged on the left and right sides of the device and electrically connected with the double-layer graphene, for passing current into the double-layer graphene and measuring voltage.

[0024] Preferably, the first insulating layer is a silicon dioxide layer with a thickness of 285-300 nm.

[0025] Preferably, the thickness of the second insulating layer is 20 nm, the thickness of the third insulating layer is 6 nm, and the second insulating layer and the third insulating layer are both hexagonal boron nitride layers.

[0026] Preferably, the double-layer graphene is confirmed to have two layers through 532 nm laser Raman spectrum testing, and the wave number range of the Raman spectrum testing is 1300-2850 cm -1.

[0027] Preferably, the nanoscale metal grating layer is a gold two-dimensional array structure for providing the required wave vector to excite the interband plasmon of double-layer graphene, realizing the momentum matching of free space light and interband plasmon of double-layer graphene; the electrode includes a first electrode and a second electrode, and the two electrodes are sequentially composed of a 1nm chromium layer, a 7nm palladium layer and a 45nm gold layer from bottom to top.

[0028] According to the specific embodiments provided by the application, the following technical effects are disclosed:

[0029] (1) The application realizes the momentum matching of free space light and interband plasmon of double-layer graphene through a nanoscale metal grating array, without the need for micro-nano etching of the graphene material itself, thereby avoiding problems such as organic residue pollution, uneven graphene strip size and rough edges in the etching process from the root, and significantly improving the device quality; at the same time, the application does not depend on a scattering type scanning near-field optical microscope, thereby breaking away from the limitation of instrument state on experimental stability, reducing environmental vibration interference, and overcoming the technical problems existing in the existing excitation scheme.

[0030] (2) The application can improve the excitation efficiency and control flexibility, improve the light transmittance of the device, and the periodic structure of the nanoscale metal grating can accurately provide additional momentum, effectively excite the interband plasmon of double-layer graphene and significantly improve the light-plasmon coupling efficiency; at the same time, the Fermi surface of the double-layer graphene can be adjusted by applying a gate voltage to the substrate, the energy of the interband plasmon can be flexibly changed, and the tuning range can be further widened by combining the metal grating period adjustment, incident light polarization direction selection and other methods, thereby realizing multi-dimensional accurate control of the interband plasmon and meeting the performance requirements in different application scenarios.

[0031] (3) The application expands the application scenarios, provides a new technical scheme for high-performance tunable mid-infrared light modulators, high-sensitivity mid-infrared photodetectors and other high-frequency mid-infrared optoelectronic devices; at the same time, the preparation process is compatible with the development needs of small-sized and integrated on-chip optoelectronic devices, promotes the transformation of double-layer graphene from basic research to practical application, and lays a technical foundation for the large-scale application of two-dimensional materials in the field of integrated optics. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative labor.

[0033] Figure 1A flow chart of a method for exciting inter-band plasmons of double-layer graphene according to the present application;

[0034] Figure 2 A cross-sectional view of a device for realizing excitation of inter-band plasmons of double-layer graphene according to an embodiment of the present application;

[0035] Figure 3 A two-dimensional plan view of a nanoscale metal grating layer according to an embodiment of the present application;

[0036] Figure 4 A Raman test spectrum of double-layer graphene obtained by a mechanical exfoliation method according to an embodiment of the present application;

[0037] Figure 5 A diagram showing the change of optical absorption rate of the Fermi surface of double-layer graphene at 84 and -79 meV with the energy of infrared light according to an embodiment of the present application.

[0038] Explanation of reference numerals:

[0039] 1, substrate; 2, first insulating layer; 3, second insulating layer; 4, double-layer graphene; 5, third insulating layer; 6, nanoscale metal grating layer; 7, first electrode; 8, second electrode. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0041] In order to make the above objectives, characteristics and advantages of the present application more apparent, the present application will be described in further detail below with reference to the drawings and specific embodiments.

[0042] As shown in Figure 1 The present embodiment provides a method for exciting inter-band plasmons of double-layer graphene, which comprises the following steps:

[0043] S1, preparing basic materials: double-layer graphene, a second insulating layer, a third insulating layer and a substrate with a first insulating layer are prepared respectively.

[0044] Specifically, the substrate with the first insulating layer is prepared in the following manner: a silicon substrate with a silicon dioxide layer is cut into a square with a side length of 8 mm by using a silicon knife, wherein the silicon dioxide layer is the first insulating layer, and the thickness of the first insulating layer is 285-300 nm.

[0045] The double-layer graphene is prepared by the following method: graphene is obtained on a silicon substrate by a mechanical exfoliation method, and the graphene is subjected to Raman spectrum testing, wherein a 532nm laser is used, and the testing wave number range is 1300-2850cm -1 The absorption peak energy and absorption intensity ratio of the G peak and the 2D peak in the Raman spectrum are used to confirm that the graphene is double-layer graphene. As shown in FIG. 1, the G peak corresponds to the in-plane vibration mode of graphene, and the 2D peak is a second-order double-resonance Raman peak. For double-layer graphene, the 2D peak presents an asymmetric peak shape, and the G peak intensity is higher than the 2D peak, which is a typical characteristic of double-layer graphene in Raman spectrum, and thus the prepared graphene can be determined to be a double-layer structure. Figure 4

[0046] The second insulating layer and the third insulating layer are prepared by the following method: two kinds of insulating layers are obtained on a silicon substrate by a mechanical exfoliation method, and the materials of the two kinds of insulating layers are both hexagonal boron nitride. Atomic force scanning microscope testing is performed on the edges of the two kinds of insulating layers, and the height of the step in the testing image is used to confirm that one kind of insulating layer is the second insulating layer with a thickness of 20nm, and the other kind of insulating layer is the third insulating layer with a thickness of 6nm.

[0047] S2, constructing an initial device substrate: according to a pick-up transfer method, the third insulating layer, the double-layer graphene and the second insulating layer are sequentially stacked to form a vertical heterojunction, and then the vertical heterojunction is transferred to the substrate on which the first insulating layer is grown. After heating separation and solvent cleaning, a clean initial device substrate is obtained, and the initial device substrate is sequentially composed of the substrate, the first insulating layer and the vertical heterojunction from bottom to top.

[0048] ​Specifically, the process of constructing the vertical heterojunction by the pick-up transfer method is as follows: first, the silicon substrate on which the third insulating layer is located is heated to 90°C, and then the third insulating layer on the silicon substrate is lifted by PC / PDMS, at this time the third insulating layer is pasted on PC / PDMS; then the PC / PDMS with the third insulating layer is attached to the double-layer graphene layer, ensuring that the double-layer graphene layer is completely covered by the third insulating layer to avoid the stress in the graphene layer caused by the difference in contact materials, and the double-layer graphene is lifted from its original silicon substrate by the van der Waals force between the third insulating layer and the double-layer graphene layer, at this time the double-layer graphene layer and the third insulating layer are pasted on the PC / PDMS together; then the silicon substrate on which the second insulating layer is located is heated to 90°C, the PC / PDMS with the double-layer graphene layer and the third insulating layer is attached to the second insulating layer, ensuring that the double-layer graphene layer is completely within the range of the second insulating layer, and the second insulating layer is lifted from its original silicon substrate by the van der Waals force, at this time the vertical heterojunction structure of the second insulating layer / double-layer graphene / third insulating layer from bottom to top is formed on the PC / PDMS; then the entire PC / PDMS with the vertical heterojunction is placed on a clean silicon substrate on which the first insulating layer (i.e. the silicon dioxide layer) is grown, and heated to 200°C to make the PC melt and separate from the PDMS, at this time the vertical heterojunction of the second insulating layer / double-layer graphene / third insulating layer is left on the silicon substrate on which the first insulating layer is grown together with the PC; finally, the obtained sample is soaked in a chloroform solution for 1h to dissolve the PC on the surface of the vertical heterojunction, and then the sample is cleaned with ethanol to obtain a clean vertical heterojunction of the second insulating layer / double-layer graphene / third insulating layer.

[0049] S3, preparing a device intermediate: preparing a nanoscale metal grating layer on the vertical heterojunction surface of the initial device substrate to form a device intermediate, the device intermediate sequentially comprises, from bottom to top, a substrate, a first insulating layer, a vertical heterojunction, and a nanoscale metal grating layer, and the momentum matching between free space light and double-layer graphene plasmon is realized through the periodic structure of the nanoscale metal grating layer.

[0050] Specifically, the preparation process of the nanoscale metal grating layer includes the following steps:

[0051] First, draw the grating array pattern: draw the nanoscale metal grating array pattern using CAD software, the unit of the grating array is a rectangular pattern, the length of the rectangular unit is 5 um, the width is 250 nm; build a metal grating array with the rectangular unit as the basic unit, the spacing between adjacent rectangular units in the x direction (i.e. the grating array x direction period) is 500 nm, the spacing between adjacent rectangular units in the y direction (i.e. the grating array y direction period) is 5.25 um, the overall range of the metal grating array is 20 um x 20 um, and when drawing, adjust the overall range of the array according to the size of the double-layer graphene to ensure that the metal grating array completely covers the entire double-layer graphene;

[0052] Second, spin and process photoresist: uniformly spin a layer of PMMA A4 photoresist on top of the vertical heterojunction, the uniform coating process is divided into two steps, the first step sets the spin speed to 500 rpm and the time to 5 s, so that the photoresist covers the entire sample; the second step sets the spin speed to 3000 rpm and the time to 60 s, so that the photoresist thickness reaches 200 nm; then place the substrate with photoresist on the heating table to heat, set the heating temperature to 180℃ and the heating time to 3 minutes;

[0053] Next, electron beam exposure: use an electron beam exposure system to expose the drawn nanoscale metal grating array pattern, due to the small period unit and large overall area of the nanoscale metal grating array pattern, precise exposure parameters are required to obtain high-precision patterns, the specific exposure parameters are: exposure voltage is set to 30KV, exposure aperture is set to 10um, exposure dose is set to 400μc / cm 2 , set the exposure origin near the pattern, and the exposure magnification is not less than 1000 times;

[0054] Finally, development, fixing and film plating and stripping: after exposure, develop with a developing solution which is a mixture of methyl isobutyl ketone and isopropyl alcohol, and the volume fraction ratio of methyl isobutyl ketone to isopropyl alcohol is 1:3; after development, fix with isopropyl alcohol to obtain an accurate nanoscale metal grating array pattern; deposit a 40 nm thick gold film on the sample surface by electron beam evaporation plating technology, then immerse the entire sample in a beaker containing acetone solution for 1 hour, remove the gold film and photoresist in the unexposed area on the surface, and only the gold film remains in the exposed pattern to form a nanoscale metal grating layer.

[0055] S4, build a complete device: prepare electrodes on the left and right sides of the device intermediate to form an electrical connection between the electrodes and the double-layer graphene, build an electrical regulation path of the double-layer graphene Fermi surface, and obtain a complete device for exciting interband plasmons.

[0056] S5, plasmon excitation and regulation: the gate voltage is applied to the bilayer graphene through the electrode to pass in the current and measure the voltage, the Fermi surface of the bilayer graphene is adjusted by applying the gate voltage on the substrate, the mid-infrared light is irradiated, and the excitation and energy regulation of the bilayer graphene interband plasmon in the complete device are realized.

[0057] Specifically, the preparation process of the electrode is as follows: taking the device intermediate with a prepared nanoscale metal grating layer as a sample, spin coating photoresist on the surface of the sample, the spin coating photoresist step is consistent with the spin coating PMMA A4 photoresist step in S3; then the electrode pattern drawn in advance by CAD software is used to expose the left and right side regions of the sample by using an electron beam exposure system, and after exposure, development and fixing operations are performed in sequence to obtain the electrode pattern; then a metal layer is evaporated on the sample in sequence, first, a 1nm thick chromium layer is evaporated on the sample by using a thermal evaporation coating technology, then a 7nm thick palladium layer and a 45nm thick gold layer are evaporated on the sample by using an electron beam evaporation coating technology, forming an electrode electrically connected with the bilayer graphene, which is used for subsequent passing in the current and measuring the voltage of the bilayer graphene.

[0058] The device sample obtained by the above steps is placed in a room temperature environment for infrared spectrum test, and the obtained result is as shown in Figure 5 By applying the gate voltage on the silicon substrate, the Fermi surface of the bilayer graphene can be adjusted to 84meV, at this time the bilayer graphene is of electron type, and through the absorption spectrum line it can be seen that there is an obvious absorption peak near 400meV, the Fermi surface of the bilayer graphene is adjusted to-79meV, at this time the bilayer graphene is of hole type, and through the absorption spectrum line it can be seen that there is an obvious absorption peak near 380meV, effectively exciting the bilayer graphene interband plasmon, and the energy of the interband plasmon can be changed by adjusting the size of the gate voltage.

[0059] Further according to the above content, the embodiment also provides a device for realizing the excitation method of the bilayer graphene 4-band interband plasmon, as shown in Figure 2As shown, the device comprises, from bottom to top, in sequence: a substrate 1, a first insulating layer 2 disposed on the upper surface of the substrate 1, wherein the first insulating layer 2 is a silicon dioxide layer with a thickness of 285-300 nm; a vertical heterojunction disposed on the upper surface of the first insulating layer 2, and the vertical heterojunction comprises, from bottom to top, in sequence: a second insulating layer 3, a double-layer graphene 4, and a third insulating layer 5, wherein the thickness of the second insulating layer 3 is 20 nm, the thickness of the third insulating layer 5 is 6 nm, and the second insulating layer 3 and the third insulating layer 5 are both hexagonal boron nitride layers, and the double-layer graphene 4 is confirmed to have two layers by 532 nm laser Raman spectrum test; a nanoscale metal grating layer 6 disposed on the upper surface of the third insulating layer 5 and covering the double-layer graphene 4; electrodes disposed on the left and right sides of the device and electrically connected with the double-layer graphene 4, for passing current into the double-layer graphene 4 and measuring voltage; the electrodes comprise a first electrode 7 and a second electrode 8, and the two electrodes are composed of, from bottom to top, in sequence: a 1 nm chromium layer, a 7 nm palladium layer, and a 45 nm gold layer.

[0060] As shown in the formula (I), the nanoscale metal grating layer is a gold two-dimensional array structure, and the period thereof can realize momentum matching of free space light and double-layer graphene interband plasmons. Figure 3 As shown in the formula (I), the nanoscale metal grating layer is a gold two-dimensional array structure, and the period thereof can realize momentum matching of free space light and double-layer graphene interband plasmons.

[0061] Therefore, by using the above-mentioned double-layer graphene interband plasmon excitation method and the prepared device, the double-layer graphene interband plasmons can be effectively excited by the nanoscale metal grating array, the light-plasmon coupling efficiency can be significantly improved, and the interband plasmon energy can be regulated, which avoids micro-nano processing of the graphene material itself to prevent pollution of organic residues in the processing process, does not depend on a scattering type scanning near-field optical microscope, and has low overall cost, high precision, wide tuning range, and high repeatability, thereby providing a new solution for high-frequency mid-infrared optoelectronic devices and laying a technical foundation for application of double-layer graphene in miniaturized and integrated on-chip optoelectronic devices.

[0062] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation manners and application ranges can be changed according to the idea of the present application. In conclusion, the content of the present specification should not be understood as a limitation of the present application.

Claims

1. A method for exciting interband plasmons in bilayer graphene, characterized in that, Includes the following steps: S1. Prepare basic materials: Prepare bilayer graphene, second insulating layer, third insulating layer and substrate with first insulating layer grown on it respectively; S2. Constructing the initial device substrate: According to the pick-up transfer method, the third insulating layer, the bilayer graphene, and the second insulating layer are stacked sequentially to form a vertical heterojunction. The vertical heterojunction is then transferred to the substrate on which the first insulating layer has been grown. After heating separation and solvent cleaning, a clean initial device substrate is obtained. The initial device substrate consists of the substrate, the first insulating layer, and the vertical heterojunction from bottom to top. S3. Fabrication of device intermediate: A nanoscale metal grating layer is fabricated on the vertical heterojunction surface of the initial device substrate to form a device intermediate. The device intermediate consists of a substrate, a first insulating layer, a vertical heterojunction, and a nanoscale metal grating layer from bottom to top. The periodic structure of the nanoscale metal grating layer enables momentum matching between free space light and interband plasmons in the bilayer graphene. S4. Constructing a complete device: Electrodes are prepared on the left and right sides of the intermediate body of the device, and the electrodes are electrically connected to the bilayer graphene to construct the electrical control path of the bilayer graphene Fermi surface, thereby obtaining a complete device for exciting interband plasmons. S5. Plasmon excitation and regulation: Current is passed into the bilayer graphene through the electrode and the voltage is measured. By applying a gate voltage to the substrate to adjust the Fermi surface of the bilayer graphene and irradiating it with mid-infrared light, the excitation and energy regulation of interband plasmons in the bilayer graphene in the complete device are realized. The device for implementing the above excitation method includes, from bottom to top: Substrate; A first insulating layer is disposed on the upper surface of the substrate; A vertical heterojunction is disposed on the upper surface of the first insulating layer, and the vertical heterojunction consists of a second insulating layer, a bilayer graphene, and a third insulating layer from bottom to top. A nanoscale metal grating layer is disposed on the upper surface of the third insulating layer and covered with a double layer of graphene; Electrodes are disposed on the left and right sides of the device and electrically connected to the bilayer graphene, for passing current into the bilayer graphene and measuring voltage; The nanoscale metal grating layer is a two-dimensional gold array structure, which is used to provide the wave vector required to excite the interband plasmons of bilayer graphene, and realize the momentum matching between free space light and the interband plasmons of bilayer graphene; the electrode includes a first electrode and a second electrode, which are composed of a 1nm chromium layer, a 7nm palladium layer and a 45nm gold layer from bottom to top.

2. The method for exciting interband plasmons in bilayer graphene according to claim 1, characterized in that, In S2, the specific process of building the vertical heterostructure is as follows: first, the third insulating layer is transferred and covered on one side of the bilayer graphene, and then the second insulating layer is transferred and covered on the other side of the bilayer graphene to form a vertical heterojunction; then the vertical heterojunction is transferred to a substrate on which the first insulating layer has grown, and a clean vertical heterojunction is obtained by heating separation and solvent cleaning.

3. The method for exciting interband plasmons in bilayer graphene according to claim 2, characterized in that, The bilayer graphene was obtained by mechanical exfoliation. Raman spectroscopy confirmed that it has two layers by using the characteristics of the G peak and 2D peak, and the first insulating layer is a silicon dioxide layer.

4. The method for exciting interband plasmons in bilayer graphene according to claim 1, characterized in that, In S3, the fabrication process of the nanoscale metal grating layer includes: forming a photoresist layer on the surface of a vertical heterojunction, obtaining a grating pattern through exposure, development, and fixing, and then forming a nanoscale metal grating layer through a coating and lift-off process, wherein the material of the nanoscale metal grating layer is gold.

5. The method for exciting interband plasmons in bilayer graphene according to claim 1, characterized in that, The electrode is prepared using exposure, development, fixing, and coating processes, and the electrode material includes chromium, palladium, and gold.

6. The method for exciting interband plasmons in bilayer graphene according to claim 1, characterized in that, The first insulating layer is a silicon dioxide layer with a thickness of 285nm-300nm.

7. The method for exciting interband plasmons in bilayer graphene according to claim 1, characterized in that, The thickness of the second insulating layer is 20 nm, the thickness of the third insulating layer is 6 nm, and both the second and third insulating layers are hexagonal boron nitride layers.

8. The method for exciting interband plasmons in bilayer graphene according to claim 1, characterized in that, The bilayer graphene was confirmed to have two layers by 532nm laser Raman spectroscopy, with the wavenumber range of the Raman spectroscopy being 1300-2850 cm⁻¹. -1 .

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