Ultra-wideband anti-reflection metasurface structure device and preparation method thereof

Abstract

The invention relates to an ultra-wideband anti-reflection metasurface structure device and a preparation method thereof, and belongs to the technical field of optical elements. The ultra-wideband anti-reflection metasurface structure device comprises a substrate and a nanostructure array arranged on the surface of the substrate. The nano-structure array comprises a plurality of nano-structure units which are arranged periodically, and each nano-structure unit comprises a first silicon nitride layer, a second silicon nitride layer, a third silicon nitride layer and a silicon oxide layer which are sequentially stacked and have a specific refractive index and a specific thickness. The ultra-wide-band anti-reflection metasurface structure device has good ultra-wide-band anti-reflection performance and large-angle incidence stability, and has high transmissivity in the spectral range of 400-1500 nm and the incidence angle range of 0-45 degrees.

Description

Technical Field

[0001] This invention relates to the field of optical element technology, and in particular to an ultra-wideband anti-reflective metasurface structure device and its fabrication method. Background Technology

[0002] Interface reflection loss primarily originates from Fresnel reflection at the interface between media with different refractive indices. This reflection not only reduces luminous flux but can also cause glare, ghosting, or damage to optical components, affecting the stability of optoelectronic devices. Traditional methods to reduce interface reflection loss mainly involve using anti-reflection films. These films are created by depositing single or multiple dielectric films on the substrate surface, causing destructive interference between reflected light from different interfaces, thereby reducing reflection and increasing transmittance. However, this method suffers from narrow bandwidth, angular sensitivity, and poor thermal stability. Research has found that broadband anti-reflection can be achieved by constructing subwavelength conical or gradient refractive index microstructures on the substrate surface. However, this requires high precision in nanofabrication and uniformity of the curved substrate structure, making it difficult to guarantee mass production yield and hindering industrialization. Metamaterial-based anti-reflection technology, due to its material compatibility perfectly matching CMOS processes and the ability to tune optical responses through structural parameters, along with its subwavelength thickness suitable for miniaturized device integration, can better address these issues to some extent. However, it still suffers from narrow operating bandwidth and poor angular stability, making it difficult for metamaterial-based anti-reflection devices to meet the application requirements of different spectral scenarios and complex optical systems. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide an ultra-wideband anti-reflection metasurface structure device and its preparation method.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] In a first aspect, the present invention provides an ultra-wideband anti-reflection metasurface structure device, which includes a substrate and a nanostructure array disposed on the surface of the substrate;

[0006] The nanostructure array comprises a plurality of periodically arranged nanostructure units, each nanostructure unit comprising a first silicon nitride (Si3N4) layer, a second silicon nitride (Si3N4) layer, a third silicon nitride (Si3N4) layer, and a silicon oxide (SiO2) layer stacked sequentially; the first silicon nitride layer is in contact with the substrate;

[0007] The first silicon nitride layer has a refractive index of n1 and a thickness of d1;

[0008] The second silicon nitride layer has a refractive index of n2 and a thickness of d2;

[0009] The third silicon nitride layer has a refractive index of n3 and a thickness of d3.

[0010] The silicon oxide layer has a refractive index of n4 and a thickness of d4.

[0011] n1 < n2, n3 < n2;

[0012] 1.80≤n1≤1.90 (for example, n1 can be any or any two of 1.80, 1.81, 1.82, 1.83, 1.84, 1.85, 1.86, 1.87, 1.88, 1.89, 1.90);

[0013] 1.90≤n2≤2.00 (for example, n2 can be any one or any two of 1.90, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, 2.00);

[0014] 1.80≤n3≤1.90 (for example, n3 can be any one or any two of 1.80, 1.81, 1.82, 1.83, 1.84, 1.85, 1.86, 1.87, 1.88, 1.89, and 1.90).

[0015] 1.40≤n4≤1.50 (for example, n4 can be any one or any two of 1.40, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, and 1.50).

[0016] 30nm≤d1≤40nm (for example, d1 can be any one or any two of 30nm, 31nm, 32nm, 33nm, 34nm, 35nm, 36nm, 37nm, 38nm, 39nm, and 40nm).

[0017] 60nm≤d2≤70nm (for example, d2 can be any or any combination of 60nm, 61nm, 62nm, 63nm, 64nm, 65nm, 66nm, 67nm, 68nm, 69nm, and 70nm).

[0018] 20nm≤d3≤30nm (for example, d3 can be any or any combination of 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, and 30nm).

[0019] 120nm≤d4≤140nm (for example, d4 can be any one or any two of 120nm, 121nm, 122nm, 123nm, 124nm, 125nm, 126nm, 127nm, 128nm, 129nm, 130nm, 131nm, 132nm, 133nm, 133nm, 134nm, 135nm, 136nm, 137nm, 138nm, 139nm, 140nm).

[0020] This invention stacks silicon nitride and silicon oxide thin films with specific refractive indices in a gradient distribution on a substrate, and forms nanostructure units by adjusting the thickness of each silicon nitride and silicon oxide thin film layer. This modulates the electromagnetic field in the structure of the ultra-wideband anti-reflection metasurface device, thereby enabling it to have both good ultra-wideband anti-reflection performance and large-angle incident stability, and high transmittance in the spectral range of 400–1500 nm and the incident angle range of 0–45°.

[0021] The present invention does not impose any particular limitation on the substrate in the above-mentioned ultra-wideband anti-reflection metasurface structure device, as long as it can achieve the purpose of the present invention, for example, it can be K9 glass.

[0022] As a preferred embodiment of the ultra-wideband anti-reflection metasurface structure device of the present invention, 1.85≤n1≤1.89, 1.92≤n2≤1.96, 1.85≤n3≤1.89, 1.44≤n4≤1.48.

[0023] As a preferred embodiment of the ultra-wideband anti-reflection metasurface structure device of the present invention, 32nm≤d1≤38nm, 62nm≤d2≤68nm, 22nm≤d3≤28nm, and 125nm≤d4≤135nm.

[0024] As a preferred embodiment of the ultrawideband antireflective metasurface structure device of the present invention, the shape of the nanostructure unit is a cylinder (straight cylinder); the diameter of the cylinder is D, 110nm≤D≤130nm (for example, D can be any or any two of 110nm, 112nm, 114nm, 116nm, 118nm, 120nm, 122nm, 124nm, 126nm, 128nm, 130nm).

[0025] In a preferred embodiment of the ultra-wideband anti-reflection metasurface structure device of the present invention, the period of the cylinder is P, 150nm≤P≤170nm (for example, P can be any or any two of 150nm, 152nm, 154nm, 156nm, 158nm, 160nm, 162nm, 164nm, 166nm, 168nm, 170nm).

[0026] Secondly, the present invention provides a method for fabricating the above-mentioned ultra-wideband anti-reflection metasurface structure device, comprising the following steps:

[0027] S1. A first silicon nitride layer, a second silicon nitride layer, a third silicon nitride layer, and a silicon oxide layer are sequentially deposited on the surface of the substrate using chemical vapor deposition (preferably plasma chemical vapor deposition).

[0028] S2. Photoresist is coated on the surface of the silicon oxide layer, and the pattern transfer is completed by exposure. Then, development, fixing, chromium plating, stripping, and etching (preferably inductively coupled plasma etching) are performed to obtain an ultra-wideband anti-reflective metasurface structure device.

[0029] In a preferred embodiment of the fabrication method of the ultra-wideband anti-reflection metasurface structure device of the present invention, the chemical gases used in the chemical vapor deposition method include a mixture of SiH4 and Ar, and NH3; the volume percentage of SiH4 in the mixture of SiH4 and Ar is 3% to 7% (for example, it can be any one or any two of 3%, 4%, 5%, 6%, 7%), the flow rate of the mixture of SiH4 and Ar is 0 to 1000 sccm (for example, it can be any one or any two of 0, 100 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm, 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm); and the flow rate of NH3 is 0 to 50 sccm (for example, it can be any one or any two of 0, 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm).

[0030] In a preferred embodiment of the fabrication method of the ultra-wideband anti-reflection metasurface structure device of the present invention, the deposition temperature is 250°C to 350°C (for example, it can be any or any combination of 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, and 350°C).

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This invention involves stacking silicon nitride and silicon oxide films with specific refractive indices in a gradient distribution on a substrate, and forming nanostructure units by controlling the thickness of each silicon nitride and silicon oxide film layer. The nanostructure units are then arranged periodically to obtain an ultra-wideband anti-reflection metasurface structure device. This ultra-wideband anti-reflection metasurface structure device exhibits high transmittance in the spectral range of 400–1500 nm and the incident angle range of 0–45°, which can meet the application requirements of different spectral application scenarios and complex optical systems. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the ultra-wideband anti-reflection metasurface structure device of the present invention;

[0034] Figure 2 This is a schematic flowchart of the fabrication method of the ultra-wideband anti-reflection metasurface structure device of the present invention;

[0035] Figure 3 The image shows the reflection and transmission spectra of the ultrawideband antireflective metasurface structure device in Example 1 at an incident angle of 0°.

[0036] Figure 4 The image shows the reflection and transmission spectra of the ultrawideband antireflective metasurface structure device in Example 1 at an incident angle of 15°.

[0037] Figure 5 The image shows the reflection and transmission spectra of the ultrawideband antireflective metasurface structure device in Example 1 at an incident angle of 30°.

[0038] Figure 6 The image shows the reflection and transmission spectra of the ultrawideband antireflective metasurface structure device in Example 1 at an incident angle of 45°.

[0039] Figure 7 This is a schematic diagram of the experimental measurement optical path for the ultra-wideband anti-reflection metasurface structure device of the present invention;

[0040] Figure 8 The image shows the experimentally measured transmission and reflection spectra of the ultra-wideband anti-reflection metasurface structure device in Example 1. Detailed Implementation

[0041] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0042] Unless otherwise specified, all other materials and reagents used in the examples are commercially available.

[0043] Example 1

[0044] An ultrawideband anti-reflective metasurface structure device (such as...) Figure 1As shown, the device includes a substrate and a nanostructure array disposed on the surface of the substrate (K9 glass). The nanostructure array includes several periodically arranged nanostructure units, each nanostructure unit being cylindrical with a diameter of D nm and a period of P nm. Each nanostructure unit is composed of a first silicon nitride layer (refractive index n1 = 1.87, thickness d1 = 35 nm), a second silicon nitride layer (refractive index n2 = 1.94, thickness d2 = 65 nm), a third silicon nitride layer (refractive index n3 = 1.87, thickness d3 = 25 nm), and a silicon oxide layer (refractive index n4 = 1.46, thickness d4 = 130 nm) stacked sequentially.

[0045] The above-mentioned method for fabricating ultrawideband antireflective metasurface structure devices includes the following steps: (e.g.) Figure 2 As shown):

[0046] S1. A first silicon nitride layer (refractive index n1 = 1.87), a second silicon nitride layer (refractive index n2 = 1.94), a third silicon nitride layer (refractive index n3 = 1.87), and a silicon oxide layer (refractive index n4 = 1.46) are sequentially deposited on the surface of a substrate (K9 glass slide) using plasma chemical vapor deposition (PECVD).

[0047] The specific parameters for plasma chemical vapor deposition are as follows: base pressure is 800 mTorr, radio frequency power is 35 W, ambient temperature is 300℃, flow rate of 5% SiH4 / Ar (a mixture of SiH4 and Ar, with SiH4 accounting for 5% of the volume) is 0-1000 sccm, flow rate of NH3 is 0-50 sccm, and flow rate of N2 is 2000 sccm.

[0048] The refractive index of the silicon nitride layer is mainly adjusted by controlling the gas flow rate, as shown in Table 1. When the flow rate of 5% SiH4 / Ar is 150 sccm and the flow rate of NH3 is 14 sccm, the refractive index of the silicon nitride layer is 1.94; when the flow rate of 5% SiH4 / Ar is 100 sccm and the flow rate of NH3 is 14 sccm, the refractive index of the silicon nitride layer is 1.87.

[0049] Table 1

[0050]

[0051] S2. Spin-coat a PMMA photoresist with a thickness of approximately 100 nm onto the surface of the aforementioned silicon oxide layer, and then bake the sample on a heating stage at 180°C for 40 min. Transfer the pattern onto the photoresist using an electron beam lithography (EBL) machine. Develop the sample using a MIBK:IPA = 1:3 developer for 30 s, and fix it with an IPA solution for 10 s. Evaporate a chromium layer with a thickness of 22 nm onto the surface of the developed and fixed PMMA photoresist as a hard mask. Immerse the chromium-plated sample in a remover-PG solution for 12–24 h to remove the PMMA photoresist. Use inductively coupled plasma etching (ICP Etching) to obtain an ultrawideband anti-reflective metasurface structure device.

[0052] Examples 2 to 3

[0053] An ultrawideband antireflective metasurface structure device is identical to that of Example 1, except that d1, d2, d3, d4, D, and P are different from those of Example 1.

[0054] Table 2

[0055] serial number <![CDATA[d1 / nm]]> <![CDATA[d2 / nm]]> <![CDATA[d3 / nm]]> <![CDATA[d4 / nm]]> D / nm P / nm Example 1 35 65 25 130 120 160 Example 2 30 70 30 140 110 170 Example 3 40 60 20 120 130 150

[0056] The reflection and transmission spectra of the ultrawideband antireflective metasurface structure device in Example 1 at a 0° incident angle were obtained using FDTD simulation, as shown below. Figure 3 As shown, its average reflectivity is as low as 0.4%, and its average transmittance is as high as 99.6%. Simultaneously, the anti-reflection effect was examined at different incident angles. The reflection and transmission of the ultra-wideband anti-reflection metasurface structure device in Example 1 were investigated at incident angles of 15°, 30°, and 45°. Since the polarization state of linearly polarized light has a significant impact on reflection and transmission at different incident angles, the simulation mainly considered the case of s-polarized light, which has higher reflectivity and lower transmittance. The results show that at an incident angle of 15°, the average reflectivity of the ultra-wideband anti-reflection metasurface structure device is 0.46%, and the average transmittance is 99.54% (e.g., ...). Figure 4 As shown); at an incident angle of 30°, the average reflectivity of the ultra-wideband anti-reflective metasurface structure device is 0.71%, and the average transmittance is 99.29% (as shown). Figure 5 As shown); at an incident angle of 45°, the average reflectivity of the ultra-wideband anti-reflective metasurface structure device is 1.63%, and the average transmittance is 98.37% (as shown). Figure 6 (as shown); that is, the ultra-wideband anti-reflection metasurface structure device of the present invention has both good ultra-wideband anti-reflection performance and large-angle incident stability, and has high transmittance in the spectral range of 400-1500nm and the incident angle range of 0-45°.

[0057] In addition, according to such Figure 7The experimental measurement optical path diagram shown illustrates the experimental testing of the ultra-wideband anti-reflection metasurface structure device in Example 1. The measured reflection and transmission spectra are as follows: Figure 8 As shown, according to Figure 8 As can be seen from 'a' in the figure, the average transmittance of the ultra-wideband anti-reflective metasurface structure device is as high as 93.86% in the spectral range of 400–1000 nm; according to Figure 8 As shown in b, the average reflectivity of the ultra-wideband anti-reflective metasurface structure device is as low as 1.17% in the spectral range of 400–1000 nm.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A broadband anti-reflective metasurface structure device, characterized in that, It includes a substrate and an array of nanostructures disposed on the surface of the substrate; The nanostructure array includes a plurality of periodically arranged nanostructure units, each nanostructure unit comprising a first silicon nitride layer, a second silicon nitride layer, a third silicon nitride layer, and a silicon oxide layer stacked sequentially; the first silicon nitride layer is in contact with the substrate. The first silicon nitride layer has a refractive index of n1 and a thickness of d1; The second silicon nitride layer has a refractive index of n2 and a thickness of d2; The third silicon nitride layer has a refractive index of n3 and a thickness of d3. The silicon oxide layer has a refractive index of n4 and a thickness of d4. n1 < n2, n3 < n2; 1.80≤n1≤1.90, 1.90≤n2≤2.00, 1.80≤n3≤1.90, 1.40≤n4≤1.50; 30nm≤d1≤40nm, 60nm≤d2≤70nm, 20nm≤d3≤30nm, 120nm≤d4≤140nm.

2. The ultra-wideband anti-reflective metasurface structure device as described in claim 1, characterized in that, 1.85≤n1≤1.89, 1.92≤n2≤1.96, 1.85≤n3≤1.89, 1.44≤n4≤1.

48.

3. The ultra-wideband anti-reflective metasurface structure device as described in claim 1, characterized in that, 32nm≤d1≤38nm, 62nm≤d2≤68nm, 22nm≤d3≤28nm, 125nm≤d4≤135nm.

4. The ultra-wideband anti-reflective metasurface structure device as described in claim 1, characterized in that, The shape of the nanostructure unit is cylindrical; the diameter of the cylinder is D, 110nm≤D≤130nm.

5. The ultra-wideband anti-reflective metasurface structure device as described in claim 4, characterized in that, The period of the cylinder is P, where 150nm ≤ P ≤ 170nm.

6. The method for fabricating the ultra-wideband anti-reflective metasurface structure device according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. A first silicon nitride layer, a second silicon nitride layer, a third silicon nitride layer, and a silicon oxide layer are sequentially deposited on the surface of a substrate using chemical vapor deposition. S2. Photoresist is coated on the surface of the silicon oxide layer, and the pattern transfer is completed by exposure. Then, development, fixing, chromium plating, stripping and etching are performed to obtain an ultra-wideband anti-reflective metasurface structure device.

7. The preparation method according to claim 6, wherein the chemical gases used in the chemical vapor deposition method include a mixture of SiH4 and Ar and NH3; the volume percentage of SiH4 in the mixture of SiH4 and Ar is 3% to 7%, the flow rate of the mixture of SiH4 and Ar is 0 to 1000 sccm, and the flow rate of NH3 is 0 to 50 sccm.

8. The preparation method according to claim 6, wherein the deposition temperature is 250°C to 350°C.

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