Infrared modulator based on graphical two-dimensional material metasurface

Abstract

The invention relates to an infrared modulator based on a graphical two-dimensional material metasurface. The infrared modulator comprises a substrate silicon dioxide (SiO2), a polymer supporting material (the refractive index ranges from 1.6 to 1.8), a metal layer such as gold (Au) or silver (Ag) and an upper-layer two-dimensional material such as graphene and molybdenum disulfide (MoS2). According to the two-dimensional material metasurface based on patterning, the transmissivity of incident light with different wavelengths can be regulated and controlled through the surface plasmon polarization effect, a near-infrared to mid-infrared modulator sensitive to different polarized light is obtained through patterning, meanwhile, a polymer is printed through the 3D printing technology, and the technology becomes simple. The method can realize all-optical calculation, and is applied to image processing, convolutional neural network realization, edge detection and other scenes. The device has the advantages of being simple in structure, convenient to integrate, high in calculation speed, capable of working at the room temperature and the like, patterns can be simply and accurately adjusted on the micrometer scale, and therefore transmission frequency spectrums with different modulation effects are obtained. Wavebands involved in the invention include near-infrared and intermediate-infrared.

Description

Method Domain

[0001] This invention belongs to the field of optical communication technology, and specifically relates to an infrared modulator. Background Method

[0002] Near-infrared light (wavelength approximately 0.75–2.5 μm) and mid-infrared light (wavelength approximately 2.5–25 μm) are important regions in the electromagnetic spectrum that bridge the visible and far-infrared spectrums, possessing unique application value in image processing. For a long time, the potential of near-infrared light in fine image processing was limited due to insufficient detector sensitivity and immature imaging algorithms. Mid-infrared light, on the other hand, was constrained by poor light source stability and high system costs, resulting in relatively slow development and limited application in image processing. In recent years, with the rapid development of optoelectronic technology, the emergence of new sensitive materials, and continuous innovation in computer vision algorithms, the performance of near-infrared and mid-infrared imaging equipment has significantly improved, and costs have gradually decreased. They have shown great application potential in fields such as agricultural remote sensing (e.g., crop growth monitoring), medical imaging (e.g., early tumor screening), and industrial inspection (e.g., material defect identification). Consequently, research on near-infrared and mid-infrared light and image processing has received increasing attention and importance.

[0003] Two-dimensional materials are those in which electrons can move freely only in two dimensions at a non-nanoscale (1-100 nm) level. Graphene is a typical example of a two-dimensional material. Graphene is a single layer of carbon atoms arranged in a honeycomb structure. Its excellent properties in optics, electricity, heat, and mechanics have attracted widespread attention from researchers worldwide. Graphene is only 0.33 nm thick, yet it exhibits strong light interaction. Undoped graphene has a consistent response from near-infrared to mid-infrared, without a unique response in any particular wavelength band, and its absorption rate for perpendicularly incident light is approximately 2.3%. However, graphene's absolute light absorption rate is not high, and it lacks wavelength selectivity. Summary of the Invention

[0004] In view of this, the present invention proposes a wavelength-tunable metasurface infrared photodetector based on patterned two-dimensional materials, with polymer as the supporting material and two-dimensional materials and metal forming the main structure. It responds between the near-infrared and mid-infrared bands and has different modulation effects for different polarized light.

[0005] This invention provides an infrared detector based on metallic gold and two-dimensional materials, wherein an example of two-dimensional material is graphene, comprising:

[0006] Using silicon dioxide (SiO2) as the substrate and 3D-printed polymer (refractive index 1.6-1.8) as the support material, a layer of metallic gold (Au) is deposited on the surface.

[0007] Graphene was transferred onto a metal using a wet transfer method.

[0008] By placing a light source, i.e. a plane wave, and by placing a monitor, the transmittance, reflectance, and absorptivity of the metasurface are calculated.

[0009] By setting the polarization state of the plane wave, the response of the metasurface to light with different polarizations is calculated.

[0010] More specifically, for metallic materials, taking gold (Au) as an example, the relevant parameters used in the material are those reported by Palik et al.

[0011] More specifically, the printed pattern of the polymer support material directly determines the pattern of the gold layer, which in turn determines the pattern of the graphene, thus affecting the transmittance of the metasurface.

[0012] The main advantages and innovations of this invention are:

[0013] 1. This invention demonstrates that graphene and gold can exhibit responsive characteristics to certain wavelengths under specific patterning conditions.

[0014] 2. The device process of this invention uses 3D printing polymer to form subsequent patterns, which is less difficult to operate and simpler than traditional photolithography.

[0015] 3. The device of this invention is small in size and highly integrated. During use, it only involves optical calculations and does not involve photoelectric conversion, so the calculation speed is fast. Attached Figure Description

[0016] Figure 1 The simulation device's structural diagram and the shapes of the polymer, metallic gold, and graphene.

[0017] Figure 2 The transmissivity modulation effect of metasurfaces on infrared light scanning with different polarization states, in the case of polymers only with 3D printing.

[0018] Figure 3 To illustrate the transmittance modulation effect of metasurfaces on infrared light scanning with different polarization states when polymer and gold layers are superimposed.

[0019] Figure 4 The transmissivity modulation effect of this metasurface for infrared light scanning with different polarization states in the presence of polymer, gold layer, and graphene. Detailed Implementation

[0020] For ease of understanding, the present invention will be further described below with reference to the accompanying drawings. Obviously, the described examples are only a portion, not all, of the examples in this invention. All other examples obtained by those skilled in the art based on the examples in this invention without inventive effort are within the scope of protection of this invention.

[0021] Figure 1 This provides a structural diagram of the simulated device, as well as schematic diagrams of the shapes of the gold layer and graphene. Figure 1 The orientation shown, from top to bottom, represents graphene, gold (Au), polymer, and silicon dioxide (SiO2). In the FDTD simulation, the simulation region was set to 4µm in both length and width; the polymer and gold layers were set to 3µm in both length and width; the width of the central gap was set to 0.2µm; the central cavity was 2µm long and 1.5µm wide; the thickness of the polymer and gold layers was 20nm; and the graphene was 3µm in both length and width.

[0022] Figure 2 To obtain the transmittance of polymer patterns obtained solely through 3D printing in FDTD for different polarization states of light in the range of 5.4µm-10µm, it can be found that, even with patterning, the metasurface is insensitive to the polarization of light in this wavelength range due to its fixed refractive index, exhibiting the same response to light with different polarization states.

[0023] Figure 3 To deposit a gold layer on the polymer, FDTD simulations were used to obtain its transmittance spectra across different polarization states. (Comparison) Figure 2 It can be observed that after the gold layer is stacked, the metasurface becomes sensitive to the polarization state. Under the scanning condition of 0°-90° with a step size of 15°, the transmittance difference is obvious for different polarization states, and the modulation range is about 5%-80%.

[0024] Figure 4 The transmittance of the metasurface after adding the graphene layer, obtained by FDTD simulation under different polarization angles, shows that its transmission rate is significantly higher than that of the metasurface under different polarization angles. Figure 3 The presence of graphene and a resonant cavity results in transmission peaks, with the polarization transmittance spectrum modulation range ranging from approximately 0% to 90%. This metasurface modulation normalizes the transmitted light intensity, corresponding to the synaptic weights in a convolutional neural network, which can then be applied to matrix calculations. By mapping light intensity to pixel grayscale values, changing the polarization angle alters the metasurface's transmittance, thus changing the light intensity and achieving the effect of encoding based on pixel grayscale values. This allows for neural network computation.

[0025] As shown in the above images, the incident light can be modulated by surface plasmon polarization between graphene and gold layers. Under specific requirements, the application can be carried out by changing the patterns of the gold layer and graphene, and by calculating the transmittance in different wavelength ranges.

Claims

1. An infrared modulator based on a patterned two-dimensional metasurface, characterized in that: The system includes a substrate such as silicon dioxide (SiO2), a support material such as a polymer (refractive index 1.6–1.8), a metal layer such as gold (Au) or silver (Ag), and an upper two-dimensional material such as graphene or molybdenum disulfide (MoS2). The polymer is printed on the silicon dioxide (SiO2) substrate. The metal layer is placed above the polymer and below the two-dimensional material. The graphene is a large-area monolayer graphene, serving as an example of a two-dimensional material. The system aims to optimize the transmittance of infrared light at polarization angles. The all-optical computation problem is simplified to the problem of light transmission of this metasurface to different wavelengths and polarization angles.

2. An infrared modulator based on a patterned two-dimensional material metasurface according to claim 1, characterized in that: Using 3D printing technology to form specific polymer patterns with micron-level precision, as shown in Figure 1, gold is plated on top of the pattern, and then graphene is transferred onto the gold layer using a wet transfer process. This process is simpler and easier to operate than traditional processes.

3. An infrared modulator based on a patterned two-dimensional material metasurface according to claim 1, characterized in that: The structure employs a stacked structure of two-dimensional materials, metal, and polymer, along with a patterned structure containing cavities. The polymer material has a refractive index of 1.6–1.8 and a thickness of 20–40 nm. The metal layer has a thickness of approximately 20–40 nm. The polymer and gold layers have dimensions of (3–4) μm × (3–4) μm, the cavity dimensions are (1.5–2 μm) × (1.5–2 μm), and the gap dimensions are (0.2–0.5) μm.

4. An infrared modulator based on a patterned two-dimensional material metasurface as described in claim 1, characterized in that: The supporting material and the metal layer material are not limited to the materials described in the examples. The graphene is an example of a two-dimensional material, but is not limited to graphene. The variables in the problem include the plane wave incident polarization angle (0° to 90°), as well as the shape and cavity size of the metasurface.

5. An infrared modulator based on a patterned two-dimensional material metasurface according to claim 1, characterized in that: By utilizing the surface plasmon polarization effect between metals and two-dimensional materials, the all-optical computation problem is simplified to the metasurface having different transmittance for the polarization state of light in a specific wavelength range (3µm~20µm), and this is applied to optical matrix calculation.

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