Ultraviolet broadband light absorber based on graphene and multilayer periodic structure

Abstract

The invention relates to the technical field of optical materials and nano structures, in particular to an ultraviolet broadband light absorber based on graphene and a multi-layer periodic structure. The structure of the ultraviolet broadband light absorber sequentially comprises a graphene layer, a distributed Bragg reflection grating structure layer and a SiO2 substrate at the bottom from top to bottom. The preparation process of the ultraviolet broadband light absorber comprises the following steps: preparing the graphene layer; a SiO2 layer is deposited; depositing a TiO2 layer; carrying out multi-layer superposition; adding a graphene layer; and completing the device. The light absorption efficiency of graphene in the ultraviolet band is greatly improved, broadband efficient absorption within the wavelength range of 240-370 nm is achieved, the highest absorption rate can reach 99.75%, the absorber is not sensitive to polarization, the preparation process is simple, and technical support is provided for design of the efficient ultraviolet absorber.

Description

Technical Field

[0001] The invention relates to the technical field of optical materials and nanostructures, and in particular to an ultraviolet broadband light absorber based on graphene and a multi-layer periodic structure. Background Art

[0002] With the rapid development of nanophotonics technology, efficient and broadband light absorbers play an indispensable role in the fields of photoelectric detection, solar cells and biochemical sensing. The core goal of these devices is to achieve efficient capture and utilization of light, especially to have good light absorption performance in a wide band. However, to achieve this goal, careful optimization is required in material selection and structural design.

[0003] In recent years, graphene has become an important material for absorber design due to its wide spectrum absorption ability. As a two-dimensional carbon material, graphene exhibits unique optoelectronic properties throughout the visible and ultraviolet range. It not only has extremely high carrier mobility, but also has broadband optical response characteristics. However, the light absorption rate of single-layer graphene is only 2.3%. The low absorption rate is mainly due to the thickness of its single atomic layer, which leads to weak interaction intensity between light and materials, which limits the direct application of single-layer graphene in efficient light absorbers. In the infrared and visible light bands, a variety of graphene-based absorber designs have achieved high absorption rates. For example, perfect absorption close to 100% in the visible light range can be achieved through a composite structure based on graphene and one-dimensional photonic crystals. However, the absorption efficiency of graphene-based absorbers in the ultraviolet band is still generally low. For example, the utility model patent "A multilayer film structure based on Bragg grating / metal film" with publication number CN213843569U discloses a multilayer film structure that can improve the light absorption efficiency of graphene in the ultraviolet light region. This structure can effectively enhance the interaction between ultraviolet light and graphene, and increase the absorption peak of graphene at a wavelength of 275nm to 95.34%. However, the absorption rate is still low and it is difficult to meet the needs of specific application scenarios.

[0004] Based on the above problems, the present invention provides an ultraviolet broadband light absorber based on graphene and a multi-layer periodic structure, aiming to provide a light absorption structure with broadband high absorption in the ultraviolet band, providing technical support for the design of high-efficiency ultraviolet light absorbers. Summary of the invention

[0005] The object of the present invention is to provide an ultraviolet broadband light absorber based on graphene and a multi-layer periodic structure.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The structure of the ultraviolet broadband light absorber based on graphene and multi-layer periodic structure described in the present invention is a graphene layer, a distributed Bragg reflection grating structure layer and a SiO2 substrate from top to bottom; wherein the distributed Bragg reflection grating structure layer is composed of a periodic unit stack composed of any one of the dielectric materials of Na3AlF6, SiO2, KCl and TiO2.

[0008] Preferably, in the ultraviolet broadband light absorber based on graphene and a multi-layer periodic structure described in the present invention, the distributed Bragg reflection grating structure layer is composed of a stack of periodic units composed of SiO2 and TiO2, and the number of periodic unit layers is 2-8.

[0009] Further preferably, in the ultraviolet broadband light absorber based on graphene and a multi-layer periodic structure described in the present invention, the distributed Bragg reflection grating structure layer is composed of a stack of periodic units composed of SiO2 and TiO2, and the number of periodic unit layers is 4-8.

[0010] Still further preferably, in the ultraviolet broadband light absorber based on graphene and a multi-layer periodic structure described in the present invention, the distributed Bragg reflection grating structure layer is composed of a periodic unit stack composed of SiO2 and TiO2, and the number of periodic unit layers is 6.

[0011] Preferably, in the ultraviolet broadband light absorber based on graphene and multi-layer periodic structure described in the present invention, in the periodic unit of the distributed Bragg reflection grating structure layer: the thickness of the SiO2 layer is 48.26nm, and the refractive index is 1.45; the thickness of the TiO2 layer is 25.74nm, and the refractive index is 2.72.

[0012] Preferably, in the ultraviolet broadband light absorber based on graphene and a multi-layer periodic structure of the present invention, the thickness of the graphene layer is 0.34 nm.

[0013] Preferably, in the ultraviolet broadband light absorber based on graphene and multi-layer periodic structure of the present invention, the thickness of the SiO2 substrate is greater than 2 μm.

[0014] The method for preparing the ultraviolet broadband light absorber based on graphene and multilayer periodic structure of the present invention comprises the following steps:

[0015] S1. Preparation of graphene layer:

[0016] Graphene is grown on a copper substrate using chemical vapor deposition (CVD). The copper substrate is placed in a CVD reactor and methane is introduced to deposit graphene. After the growth is completed, a polymer film is used to transfer the graphene to a pre-prepared SiO2 substrate.

[0017] Deposition of S2 and SiO2 layers:

[0018] After the graphene layer was transferred to the SiO2 substrate, the SiO2 film was deposited using electron beam evaporation, and the deposition time and power were adjusted to ensure that the thickness of each SiO2 layer was 48.26nm;

[0019] S3. Deposition of TiO2 layer:

[0020] The TiO2 layer was deposited on the SiO2 layer by reactive magnetron sputtering, and the oxygen flow rate and power were controlled to ensure that the thickness of the TiO2 layer was 25.74 nm and the refractive index reached 2.72;

[0021] S4, multi-layer superposition:

[0022] Repeatedly depositing SiO2 layers and TiO2 layers alternately until the desired total number of layers is reached;

[0023] S5. Addition of graphene layer:

[0024] The graphene layer is accurately aligned and placed on the periodic unit interface composed of SiO2 layer and TiO2 layer;

[0025] S6, device completion:

[0026] The prepared multilayer structure is finely processed through photolithography and etching technology to form the required device shape, and the subsequent electrical contact and packaging processes are completed.

[0027] Beneficial effects of the present invention:

[0028] The present invention provides an ultraviolet broadband light absorber based on graphene and a multi-layer periodic structure. By optimizing grating structure parameters, the light absorption efficiency of graphene in the ultraviolet band is greatly improved, and broadband high-efficiency absorption in the wavelength range of 240 to 370 nm is achieved. The absorption rate is as high as 99.75%, and the full width at half maximum of the absorption curve is 115 nm. At the same time, the device has a simple preparation process, is insensitive to light polarization, and has wide-angle absorption characteristics. The present invention provides technical support for the design of high-efficiency ultraviolet light absorbers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the main structure of the ultraviolet broadband light absorber based on graphene and multi-layer periodic structure (in the figure: ① is the graphene layer; ② is the SiO2 layer; ③ is the TiO2 layer);

[0030] Figure 2 is the reflection spectrum formed by the distributed Bragg reflector in the ultraviolet range when the number of SiO2 / TiO2 periodic unit layers is 6;

[0031] Figure 3is the absorption spectrum of the ultraviolet absorber under different dielectric layer refractive index ratios;

[0032] Figure 4 is the absorption spectrum of the UV absorber under different polarization states of the incident light;

[0033] Figure 5 The absorption spectra of the UV absorber under normal incidence conditions with different SiO2 / TiO2 periodic unit layer numbers;

[0034] Figure 6 is the absorption spectrum of the UV absorber at different incident light angles. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is described in detail below in conjunction with specific embodiments. The following embodiments are only used for explanation and illustration, and do not constitute a limitation on the technical solution of the present invention.

[0036] Example 1

[0037] The ultraviolet broadband light absorber based on graphene and multi-layer periodic structure consists of a graphene layer, a distributed Bragg reflection grating structure composed of 6 periodic units composed of SiO2 and TiO2, and a SiO2 substrate from top to bottom. The thickness of the graphene layer is 0.34nm; the thickness of the SiO2 layer in the periodic unit of the distributed Bragg reflection grating structure is 48.26nm, with a refractive index of 1.45; the thickness of the TiO2 layer is 25.74nm, with a refractive index of 2.72; and the thickness of the SiO2 substrate is 3μm.

[0038] Example 2

[0039] The ultraviolet broadband light absorber based on graphene and multi-layer periodic structure consists of a graphene layer, a distributed Bragg reflection grating structure composed of two periodic units composed of SiO2 and TiO2, and a SiO2 substrate from top to bottom. The thickness of the graphene layer is 0.34nm; the thickness of the SiO2 layer in the periodic unit of the distributed Bragg reflection grating structure is 48.26nm, with a refractive index of 1.45; the thickness of the TiO2 layer is 25.74nm, with a refractive index of 2.72; and the thickness of the SiO2 substrate is 3μm.

[0040] Example 3

[0041] The ultraviolet broadband light absorber based on graphene and multi-layer periodic structure consists of a graphene layer, a distributed Bragg reflection grating structure composed of four periodic units composed of SiO2 and TiO2, and a SiO2 substrate from top to bottom. The thickness of the graphene layer is 0.34nm; the thickness of the SiO2 layer in the periodic unit of the distributed Bragg reflection grating structure is 48.26nm, with a refractive index of 1.45; the thickness of the TiO2 layer is 25.74nm, with a refractive index of 2.72; and the thickness of the SiO2 substrate is 3μm.

[0042] Example 4

[0043] The ultraviolet broadband light absorber based on graphene and multi-layer periodic structure consists of a graphene layer, a distributed Bragg reflection grating structure composed of 8 periodic units composed of SiO2 and TiO2, and a SiO2 substrate from top to bottom. The thickness of the graphene layer is 0.34nm; the thickness of the SiO2 layer in the periodic unit of the distributed Bragg reflection grating structure is 48.26nm, with a refractive index of 1.45; the thickness of the TiO2 layer is 25.74nm, with a refractive index of 2.72; the thickness of the SiO2 substrate is 3μm.

[0044] Example 5

[0045] The ultraviolet broadband light absorber based on graphene and multi-layer periodic structure consists of a graphene layer, a distributed Bragg reflection grating structure composed of 6 periodic units composed of Na3AlF6 and TiO2, and a SiO2 substrate from top to bottom. The thickness of the graphene layer is 0.34nm; the thickness of the Na3AlF6 layer in the periodic unit of the distributed Bragg reflection grating structure is 52.63nm, with a refractive index of 1.33; the thickness of the TiO2 layer is 25.74nm, with a refractive index of 2.72; and the thickness of the SiO2 substrate is 3μm.

[0046] Example 6

[0047] The ultraviolet broadband light absorber based on graphene and multi-layer periodic structure consists of a graphene layer, a distributed Bragg reflection grating structure composed of 6 periodic units composed of KCl and TiO2, and a SiO2 substrate from top to bottom. The thickness of the graphene layer is 0.34nm; the thickness of the KCl layer in the periodic unit of the distributed Bragg reflection grating structure is 46.98nm, with a refractive index of 1.49; the thickness of the TiO2 layer is 25.74nm, with a refractive index of 2.72; and the thickness of the SiO2 substrate is 3μm.

[0048] Example 7

[0049] Preparation process of ultraviolet broadband light absorber based on graphene and multilayer periodic structure:

[0050] (1) Preparation of graphene layer: A single layer of graphene is grown on a copper substrate using chemical vapor deposition (CVD). The copper substrate is placed in a CVD reactor and methane is introduced to deposit graphene. After the growth is completed, a polymer film is used to transfer the graphene to a pre-prepared SiO2 substrate.

[0051] (2) Deposition of SiO2 layer: After the graphene layer is transferred to the SiO2 substrate, the SiO2 film is deposited by electron beam evaporation. The deposition time and power are adjusted to control the thickness of the SiO2 to ensure that the thickness of each SiO2 layer is 48.26 nm.

[0052] (3) Deposition of TiO2 layer: The TiO2 layer was deposited on the SiO2 layer by reactive magnetron sputtering, and the oxygen flow rate and power were controlled to ensure that the thickness of each TiO2 layer was 25.74 nm and the refractive index reached 2.72.

[0053] (4) Multilayer stacking: SiO2 and TiO2 layers are deposited alternately and repeatedly to form the required 6-layer structure.

[0054] (5) Addition of graphene layer: The graphene layer is accurately aligned and placed on the periodic unit interface composed of SiO2 layer and TiO2 layer to ensure that light waves can be effectively refracted and reflected between the graphene layer and the dielectric layer.

[0055] (6) Device completion: The prepared multilayer structure can be finely processed through photolithography and etching techniques to form the desired device shape, and further complete the subsequent electrical contact and packaging processes, ultimately producing a UV absorber with high absorption efficiency.

[0056] In order to further verify the reliability of the present invention and screen out the best solution, the inventor conducted a series of experiments, as follows:

[0057] 1. Preparation of ultraviolet broadband light absorber structure

[0058] 1.1 Structural composition of ultraviolet broadband light absorber

[0059] The present invention proposes a UV broadband light absorber based on graphene and multi-layer periodic structure, and uses the principle of distributed Bragg reflector and the properties of graphene materials to study the absorption law of UV light waves by the structure. The device structure is from top to bottom: graphene layer, distributed Bragg reflector grating structure layer (i.e. SiO2 / TiO2 periodic layer), the bottom is SiO2 substrate, and the overall structure can be expressed as Gr / (SiO2 / TiO2) N / SiO2, where N is the number of periods. The distributed Bragg reflection grating structure is composed of multiple periodic units stacked together, and a single periodic unit is composed of a layer of SiO2 and a layer of TiO2. The main structure of the device is shown in the figure. Figure 1 As shown (in the figure: ① is the graphene layer; ② is the SiO2 layer; ③ is the TiO2 layer).

[0060] 1.2 Preparation process of ultraviolet broadband light absorber

[0061] Preparation process of ultraviolet broadband light absorber based on graphene and multilayer periodic structure:

[0062] (1) Preparation of graphene layer: A single layer of graphene is grown on a copper substrate using chemical vapor deposition (CVD). The copper substrate is placed in a CVD reactor and methane is introduced to deposit graphene. After the growth is completed, a polymer film is used to transfer the graphene to a pre-prepared SiO2 substrate.

[0063] (2) Deposition of SiO2 layer: After the graphene layer is transferred to the SiO2 substrate, the SiO2 film is deposited by electron beam evaporation. The deposition time and power are adjusted to control the thickness of the SiO2 to ensure that the thickness of each SiO2 layer is 48.26 nm.

[0064] (3) Deposition of TiO2 layer: The TiO2 layer was deposited on the SiO2 layer by reactive magnetron sputtering, and the oxygen flow rate and power were controlled to ensure that the thickness of each TiO2 layer was 25.74 nm and the refractive index reached 2.72.

[0065] (4) Multilayer stacking: SiO2 and TiO2 are deposited alternately and repeatedly until the required total number of layers is formed.

[0066] (5) Addition of graphene layer: The graphene layer is accurately aligned and placed on the periodic unit interface composed of SiO2 layer and TiO2 layer to ensure that light waves can be effectively refracted and reflected between the graphene layer and the dielectric layer.

[0067] (6) Device completion: The prepared multilayer structure can be finely processed through photolithography and etching techniques to form the desired device shape, and further complete the subsequent electrical contact and packaging processes, ultimately producing a UV absorber with high absorption efficiency.

[0068] 2. Parameter optimization of ultraviolet broadband light absorber

[0069] In the present invention, the dielectric constant of the graphene model is described by the Lorentz-Drude model. The Lorentz-Drude model includes two parts: the Lorentz model and the Drude model. The contributions of the two models are different in different bands. In the ultraviolet range, the contribution of the Lorentz model is dominant; in the infrared range, the contribution of the Drude model is dominant. The dielectric constant is expressed as:

[0070]

[0071] In the formula and ε Drude They represent the Lorentz model and the Drude model respectively, and their definitions are as follows:

[0072]

[0073] Where f is the oscillation intensity, Γ is the half-peak width, E0 is the central energy, ρ is the resistivity, and τ is the scattering time.

[0074] The relationship between graphene refractive index parameters and dielectric constant is as follows:

[0075]

[0076] Where ε1 and ε2 are the real and imaginary parts of the dielectric constant, respectively, and n and k represent the real and imaginary parts of the refractive index, respectively.

[0077] In order to achieve high absorption of the structure described in the present invention in the ultraviolet light band, the device structure was simulated and optimized based on the finite-difference time-domain algorithm. The specific settings are as follows: a three-dimensional model of the device was established in the FDTD Solution software, a plane wave of ultraviolet light vertically incident along the z-axis was used, periodic boundary conditions were adopted in the x and y directions, a perfect matching boundary condition was adopted in the z direction, and a non-uniform grid was set to meet good convergence results.

[0078] The electromagnetic wave of incident light propagating in a distributed Bragg reflector follows Maxwell's equations:

[0079]

[0080] In the formula, is the electric field vector of the electromagnetic wave, ω is the frequency of the electromagnetic wave, c is the speed of light in a vacuum, ε0 is the dielectric constant of a vacuum, and ε(x) is the relative dielectric constant and changes periodically with the spatial position. This equation has solutions only in certain frequencies ω, and no solutions in other frequency regions. That is, light waves of certain frequencies are prohibited from passing through this structure and will be completely reflected, forming a photonic band gap with a central wavelength of λ0. The medium refractive index n of the distributed Bragg reflector is H 、n Land the dielectric layer thickness d H ,d L satisfy:

[0081]

[0082] The corresponding bandgap width is:

[0083]

[0084] At the interface between two media of a distributed Bragg reflector, light will form reflected light and transmitted light due to interference superposition. M represents the relationship between the incident light and the outgoing light of a distributed Bragg reflector. Its essence is the product of the characteristic matrices of each layer of dielectric material. If M is used j Characterizing the characteristic matrix of the j-th layer of medium, with TE light as the incident light, we have:

[0085]

[0086] Where η j is the optical admittance of the j-th layer of dielectric material, which can be expressed as:

[0087]

[0088] δ j is the phase thickness, which can be expressed as:

[0089]

[0090] Then the transmission matrix M of the entire distributed Bragg reflector can be expressed as:

[0091]

[0092] The relationship between the electromagnetic fields on both sides of the distributed Bragg reflector is:

[0093]

[0094] The distributed Bragg reflector has a total of n layers of dielectric films. The light wave needs to pass through N+1 dielectric interfaces to pass through the entire distributed Bragg reflector. The first dielectric interface is the contact surface between air and dielectric film, and its electromagnetic field distribution is:

[0095]

[0096] The N+1th interface is the contact surface between the medium and the substrate, where the substrate can be air or other media, and its electromagnetic field distribution is:

[0097]

[0098] Where ηs is the optical admittance of the substrate medium, in Siemens. From this, the reflection coefficient of the distributed Bragg reflector can be obtained as:

[0099]

[0100] The transmission coefficient is:

[0101]

[0102] At the same time, the reflectivity R and transmittance T can be obtained:

[0103]

[0104] The calculation formula of the absorption rate A obtained from this is:

[0105] A=1-RT

[0106] The derivation process of the energy band characteristics of TM waves in distributed Bragg reflectors is similar to that of TE waves. It is only necessary to change the optical admittance of each dielectric film to:

[0107]

[0108] Through the above analysis, we use λ0=280nm as the incident wavelength, and use 6 layers of SiO2 (each layer is 48.26nm thick) and 6 layers of TiO2 (each layer is 25.74nm thick) to optimize the ultraviolet distributed Bragg reflector, forming a nearly perfect reflection band in the ultraviolet range. When the number of SiO2 / TiO2 periodic unit layers is 6, the reflection spectrum formed by the distributed Bragg reflector in the ultraviolet range is as follows: Figure 2 shown.

[0109] After optimizing the UV distributed Bragg reflector, a layer of graphene is placed on the surface. However, the factors that affect the absorption characteristics of graphene are: the refractive index ratio k (n H / n L ), dielectric thickness and dielectric layer period N. The present invention selected four different dielectric materials as research objects, namely TiO2, Na3AlF6 (the thickness of each layer of Na3AlF6 is 52.63nm), SiO2 and KCl (the thickness of each layer of KCl is 46.98nm), with refractive indices of 2.72, 1.33, 1.45 and 1.49 respectively. These four dielectric materials are combined to form three types of TiO2 / Na3AlF6, TiO2 / SiO2 and TiO2 / KCl, with refractive index ratios of k1=2.05, k2=1.88 and k3=1.83 respectively. The absorption spectra of the ultraviolet absorber under different dielectric layer refractive index ratios are shown as follows Figure 3 As shown. Figure 3It can be seen that when k gradually decreases from 2.05 to 1.83, the central wavelength λ0 of the absorption spectrum remains almost unchanged, while the bandwidth range gradually decreases, and the absorption bandwidth gradually decreases from 129nm to 105nm. It can be seen that when the refractive index of the material is different, the thickness will change accordingly, but the refractive index ratio of the two dielectric films will not affect the central wavelength of the absorption spectrum; the larger the refractive index ratio, the stronger the reflection of the distributed Bragg reflector, the larger the bandwidth of the absorption spectrum, the steeper the edge of the absorption spectrum band, and the better the cutoff. In actual production, even if there is a certain deviation between the thickness of the dielectric layer and λ0, a wide ultraviolet band with almost full absorption can be generated according to the formula. In this wide ultraviolet band, almost all light transmission is absorbed.

[0110] The composite structure designed by the present invention fully utilizes the unique characteristics of photonic crystals through the periodic superposition of graphene and multilayer dielectric materials. The present invention also conducts a detailed analysis of the sensitivity of the absorption spectrum of the structure to the polarization of the incident light. The absorption spectrum of the ultraviolet light absorber under different polarization states of the incident light is as follows: Figure 4 As shown. When the polarization state of the incident light changes from s-polarization to p-polarization, the absorption efficiency of light in the structure remains almost unchanged, showing a wide adaptability to light of different polarizations. This feature is mainly due to the symmetry and periodic arrangement of the structure, in which the alternating layout of the graphene layer and the dielectric layer makes the relationship between the absorption of light waves and the polarization direction no longer affect the absorption effect. In addition, the interface effect of the graphene layer further enhances the light absorption ability of the structure, so that the structure can maintain efficient light absorption characteristics under different polarization states. Therefore, this structure exhibits excellent performance that is insensitive to polarization and is suitable for efficient absorption of a variety of light sources and polarization states.

[0111] Considering the practical application, the present invention selects SiO2 as the raw material with high stability, low cost and convenient processing. After optimization, the optimal parameters of the structure are determined as follows: the thickness of graphene is 0.34nm; the refractive index of each SiO2 dielectric layer is 1.45 and the thickness is 48.26nm; the refractive index of each TiO2 dielectric layer is 2.72 and the thickness is 25.74nm.

[0112] In addition, the present invention determines the light absorption effect of the device under normal incidence θ = 0°, when the number of SiO2 / TiO2 periodic layers is 2, 4, 6, and 8 respectively. The absorption spectra of the ultraviolet light absorber under normal incidence conditions with different numbers of SiO2 / TiO2 periodic unit layers are as follows: Figure 5As shown in the figure, it can be found that when the number of periods is 2, the oscillation effect of the absorption spectrum in the ultraviolet band is obvious, and the absorption efficiency is below 90%. As the number of periods increases, the oscillation effect weakens. When the number of periods reaches 6, the absorption spectrum tends to be stable, with a high absorption efficiency in the wavelength range of 240-370nm, an absorption peak of up to 99.75%, and a full width at half maximum of the absorption spectrum of 115nm. This is because when the number of periods is small, the wavelength reflected by the distributed Bragg reflector is very volatile and the reflectivity is very low (35%-55%), and the interference effect formed by the incident wave graphene layer is weak and unstable, which manifests as a strong oscillation of the absorption spectrum. As the number of periods increases, in the ultraviolet range, the light waves in the multilayer structure will experience more reflections and superpositions, and the reflectivity of the distributed Bragg reflector gradually stabilizes and approaches 100%. When the incident light wave meets the distributed Bragg reflection condition, the interference effect is enhanced, so that the light field is confined to the graphene layer and the periodic structure, thereby enhancing the absorption of graphene and the absorption curve tends to be stable.

[0113] For light absorbers, the angle response of incident light is also important. Therefore, the research team simulated and analyzed the light absorption characteristics of the device under different incident angles. The absorption spectra of the UV light absorber under different incident light angles are as follows: Figure 6 As shown. From the results, it can be seen that with the increase of the incident angle, the absorption spectrum has an overall rightward shift trend (the absorption peak blue shifts), and the half-maximum full width of the absorption spectrum line decreases. When the incident angle is 30°, the absorption peak is still as high as 98.66%, but the half-maximum full width of the absorption spectrum line is reduced to 89nm. Therefore, the ultraviolet band absorber designed by the present invention has good angle response characteristics and can achieve efficient light absorption under a large range of incident angles.

[0114] The present invention uses numerical methods to study the absorption characteristics of graphene integrated distributed Bragg reflection grating structure in the ultraviolet band. The results show that the structure can achieve broadband, large-angle and high-efficiency light absorption in the ultraviolet band, solving the problems of low absorption rate, narrow bandwidth and sensitivity to polarized light of traditional single-layer graphene in the ultraviolet band. The present invention provides an important reference for the design of efficient ultraviolet light absorbers.

[0115] Although the present invention has been described in detail above by means of general description, specific implementation methods and tests, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A UV broadband light absorber based on graphene and multilayer periodic structure, characterized in that: The absorber structure comprises a graphene layer, a distributed Bragg reflection grating structure layer and a SiO2 substrate from top to bottom; wherein the distributed Bragg reflection grating structure layer is composed of a periodic unit stack composed of any one of the dielectric materials of Na3AlF6, SiO2, KCl and TiO2.

2. The ultraviolet broadband light absorber according to claim 1, characterized in that: The distributed Bragg reflection grating structure layer is composed of a stack of periodic units composed of SiO2 and TiO2, and the number of periodic unit layers is 2-8.

3. The ultraviolet broadband light absorber according to claim 2, characterized in that: The distributed Bragg reflection grating structure layer is composed of a stack of periodic units composed of SiO2 and TiO2, and the number of periodic unit layers is 4-8.

4. The ultraviolet broadband light absorber according to claim 3, characterized in that: The distributed Bragg reflection grating structure layer is composed of a stack of periodic units composed of SiO2 and TiO2, and the number of periodic unit layers is 6.

5. The ultraviolet broadband light absorber according to any one of claims 2 to 4, characterized in that: In the periodic unit of the distributed Bragg reflection grating structure layer: the thickness of the SiO2 layer is 48.26 nm, and the refractive index is 1.45; the thickness of the TiO2 layer is 25.74 nm, and the refractive index is 2.

72.

6. The ultraviolet broadband light absorber according to claim 1, characterized in that: The thickness of the graphene layer is 0.34 nm.

7. The ultraviolet broadband light absorber according to claim 1, characterized in that: The thickness of the SiO2 substrate is greater than 2 μm.

8. A method for preparing a UV broadband light absorber based on graphene and a multilayer periodic structure, characterized in that: The steps include: S1. Preparation of graphene layer: Graphene is grown on a copper substrate using chemical vapor deposition, the copper substrate is placed in a chemical vapor deposition reactor, and methane is introduced to deposit graphene; after the growth is completed, the graphene is transferred to a pre-prepared SiO2 substrate using a polymer film; Deposition of S2 and SiO2 layers: After the graphene layer was transferred to the SiO2 substrate, the SiO2 film was deposited using electron beam evaporation, and the deposition time and power were adjusted to ensure that the thickness of each SiO2 layer was 48.26nm; S3. Deposition of TiO2 layer: The TiO2 layer was deposited on the SiO2 layer by reactive magnetron sputtering, and the oxygen flow and power were controlled to ensure that the thickness of the TiO2 layer was 25.74 nm and the refractive index reached 2.72; S4, multi-layer superposition: Repeatedly depositing SiO2 layers and TiO2 layers alternately until the desired total number of layers is reached; S5. Addition of graphene layer: The graphene layer is accurately aligned and placed on the periodic unit interface composed of SiO2 layer and TiO2 layer; S6, device completion: The multi-layer structure is finely processed through photolithography and etching technology, and the subsequent electrical contact and packaging processes are completed.

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