CN110927840B - Three-grating cascade structure and ultra-wideband absorber based on three-grating cascade structure - Google Patents

Abstract

The invention relates to a triple grating cascade structure and an ultra-wideband absorber, belonging to the technical field of optical devices. A three-grating cascade structure is composed of three-grating cascade units, and the three-grating cascade units include metal tungsten blocks, silicon dioxide medium and strip-shaped metal tungsten sequentially from left to right. An ultra-wideband absorber based on a triple grating cascade structure, comprising: a base layer; a chromium film layer, which is formed on the surface of the base layer; and a silicon nitride layer, which is formed on the chromium film layer; and a graphene layer, which is formed on the silicon nitride layer; and a triple grating cascade structure layer formed on the graphene layer. The absorber of the invention can cover a wider spectral range, spanning part of ultraviolet light, all visible light and part of infrared light; the absorption rate is high, especially in the near-infrared band, the absorption rate is more than 90%.

Description

A triple-grating cascade structure and an ultra-broadband absorber based on the triple-grating cascade structure

technical field

The invention relates to a triple grating cascade structure and an ultra-wideband absorber, belonging to the technical field of optical devices.

Background technique

等利用三角槽金光栅设计结构获得500-1500横跨部分可见光和近红外光双频段光谱；(T.

Sergey I.Bozhevolnyi.Surface-plasmonpolariton resonances in triangular-groove metal gratings.PHYSICAL REVIEW B80,195407(2009))，该结构吸收频带窄且三角槽制作复杂，角度精确控制难度大。又如Ji等提出一种在银反射镜表面交替堆积金属颗粒和氧化硅薄膜的结构，实现了300–1100nm吸收(Ji Ting,Peng Lining,Zhu Yuntao,et al.Plasmonic Broadband absorber bystacking multiple mentallic nanoparticle layers,Appl.Phys.Lett.106,161107(2015))，此吸收器易于加工，但光谱带宽较窄。再如Dasol等利用底层铬膜和顶层铜光栅之间置二氧化硅的设计结构获得了500-1200nm的可见光到近红外波段的宽带吸收(DasolLee,Sung Yong Han,Yeonggyo Jeong，et al.Polarization-sensitive tunableabsorber in visible and near-infrared regimes.Scientific Reports(2018)8:12393)，该结构吸收带宽较窄，只有700nm。上述方法有的制备复杂、成本高，不利于批量生产；有的结构相对简单，但吸收带宽窄。Metamaterials are a class of artificial composite materials, which can achieve resonance frequency and impedance matching through structural design, so that the operating frequency and bandwidth can be arbitrarily adjusted according to requirements; at the same time, the depth of the structure itself is sub-wavelength scale, so that the thickness of the metamaterial electromagnetic structure is very small, which can be easily adjusted. It can reach several tenths of the wavelength, which is more beneficial to practical application than the traditional absorption structure. In 2008, Landy et al. adopted the method of matching with free space impedance to reduce reflection and maximize absorption, and developed the first broadband absorber. It has a very wide range of application prospects and has become a research hotspot; especially high-performance cross-band absorbers, which can play a major role in different new fields and are favored. as T.

et al used a triangular groove gold grating design structure to obtain a 500-1500 dual-band spectrum spanning part of the visible light and near-infrared light; (T.

Sergey I.Bozhevolnyi.Surface-plasmonpolariton resonances in triangular-groove metal gratings.PHYSICAL REVIEW B80,195407(2009)), the structure has narrow absorption band and complicated triangular groove fabrication, and it is difficult to precisely control the angle. Another example is Ji et al. proposed a structure in which metal particles and silicon oxide films are alternately stacked on the surface of a silver mirror to achieve 300–1100 nm absorption (Ji Ting, Peng Lining, Zhu Yuntao, et al.Plasmonic Broadband absorber by stacking multiple mentallic nanoparticle layers). , Appl.Phys.Lett.106, 161107(2015)), this absorber is easy to process, but the spectral bandwidth is narrow. Another example is Dasol et al. to obtain broadband absorption in the visible light to near-infrared wavelengths from 500-1200 nm by using the design structure of silicon dioxide between the bottom chromium film and the top copper grating (Dasol Lee, Sung Yong Han, Yeonggyo Jeong, et al.Polarization- Sensitive tunable absorber in visible and near-infrared regimes. Scientific Reports (2018) 8:12393), the absorption bandwidth of this structure is narrow, only 700nm. Some of the above methods have complex preparation and high cost, which are not conducive to mass production; some have relatively simple structures but narrow absorption bandwidths.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned deficiencies in the prior art, the present invention provides a triple-grating cascade structure and an ultra-wideband absorber based on the triple-grating cascade structure. The absorption coverage of the absorber is wider and the absorption rate is wider high.

In order to achieve the above purpose, the present invention adopts the following technical solutions: a triple-grating cascade structure, which is composed of three-grating cascade units, and the three-grating cascade units sequentially include metal tungsten blocks, silicon dioxide media and strips from left to right. Metal tungsten. Metal tungsten has good anti-reflection and strong transmission properties in the ultraviolet to infrared band. At the same time, it uses silicon dioxide with almost zero reflection in the ultraviolet to infrared band as the intermediate medium to form a horizontal cavity resonance mode after forming a triple grating cascade unit. The cavity resonance mode Coupling with the diffraction mode of light, resulting in equalized transmission of the incident light field.

In the above-mentioned triple grating cascade structure, the width ratio of the metal tungsten block, the silicon dioxide medium and the strip metal tungsten is 3:(1.8-2.5):(1.5-2.2). If the width ratio of the three gratings exceeds this size range, the spectral range of the transmission spectrum is narrowed or the transmittance is reduced.

In the above three-grating cascade structure, the height ratio of the metal tungsten block, the silicon dioxide medium and the strip metal tungsten is 3:(7-10):(5-8). If the height ratio of the three gratings exceeds this size range, the spectral range of the transmission spectrum is narrowed or the transmittance is reduced.

In the above three-grating cascade structure, the period of the three-grating cascade unit is the sum of the widths of the metal tungsten block, the silicon dioxide medium and the strip-shaped metal tungsten, and the sum is 900-1120 nanometers.

Preferably, the width of the metal tungsten block is 400-500 nanometers, and the height is 100-150 nanometers.

Preferably, the silicon dioxide medium has a width of 300-320 nanometers and a height of 400-450 nanometers.

Preferably, the strip-shaped metal tungsten has a width of 200-300 nanometers and a height of 300-350 nanometers.

The present invention also provides an ultra-wideband absorber based on the triple grating cascade structure, the absorber comprising:

basal layer,

a chromium film layer formed on the surface of the base layer to enhance the reflection of light and increase absorption; and

a silicon nitride layer formed on the chromium film layer for increasing the absorptivity of incident electromagnetic waves; and

a graphene layer formed on the silicon nitride layer for increasing the intensity of the plasmon resonance light field and increasing the absorptivity; and

The triple grating cascade structure layer, which is formed on the graphene layer, is used to reduce the reflection of incident electromagnetic waves, generate broadband resonance absorption, and increase the bandwidth and absorption rate of the absorber.

In the above-mentioned ultra-broadband absorber, the base layer is silicon or silicon dioxide, and the thickness of the base layer is 0.1-5 mm.

In the above-mentioned ultra-broadband absorber, the thickness of the chromium film layer is 100-120 nm.

In the above-mentioned ultra-broadband absorber, the thickness of the silicon nitride layer is 100-500 nm.

In the above-mentioned ultra-broadband absorber, the thickness of the graphene layer is 30-100 nm.

The invention studies the absorption rate and bandwidth of incident electromagnetic waves under the normal incidence of transverse magnetic (TM) polarized light waves, that is, when the light waves are vertically incident along the opposite direction of the Y axis. The ultra-broadband absorber of the present invention sequentially includes a base layer, a chromium film layer, a silicon nitride layer, a graphene layer and a triple grating cascade structure layer from bottom to top. The width of the metal tungsten block, the silicon dioxide medium and the strip metal tungsten are regularly arranged to form a structural unit and constitute a three-grating cascade structure layer. High absorption rate of incident electromagnetic waves. The thickness of the chromium film is preferably more than 100nm, which is greater than its adhesion depth in the ultraviolet to infrared band, so there is no transmitted light. At this time, the light wave absorption rate of the structure can be simplified as A=1-R, where R is the spectral reflectance designed by the structure.

Compared with the prior art, the present invention has the following advantages:

1. The material and physical size of the basic unit of the absorber can change the absorption characteristics of each absorber unit to the incident electromagnetic wave. Multiple basic units of the absorber are arranged according to certain rules, so that the absorber has a continuous macroscopic effect on the incident electromagnetic wave. . In the triple grating cascade structure of the present invention, metal tungsten blocks, silicon dioxide medium and strip metal tungsten with different thicknesses and widths are arranged regularly to form structural units, thereby realizing the overall superposition of the three absorption peaks.

2. Compared with the traditional absorber, the absorber of the present invention can cover a wider spectral range, spanning part of ultraviolet light, all visible light, and part of infrared light; the absorption rate is high, especially in the near-infrared band, the absorption rate is more than 90%.

3. Since each part of the absorber of the present invention adopts a strip structure, the preparation is convenient and the cost is low.

Description of drawings

FIG. 1 is a schematic structural diagram of a triple grating cascade structure according to the present invention.

FIG. 2 is a front view of the triple grating cascade structure of the present invention.

3 is a front view of the ultra-broadband absorber of the present invention.

FIG. 4 is the absorption spectrum of the absorber in Example 4. FIG.

5 is the absorption spectrum generated by the metal tungsten block 1, the silicon dioxide medium 2 and the strip-shaped metal tungsten 3 in the triple grating cascade structure according to Embodiment 1 of the present invention, respectively, as the top part of the absorber.

FIG. 6 is the absorption spectrum of the absorber in Example 5 of the present invention.

FIG. 7 is the absorption spectrum of the absorber in Example 6 of the present invention.

FIG. 8 is the absorption spectrum of the absorber in Comparative Example 1 of the present invention.

FIG. 9 is the absorption spectrum of the absorber in Comparative Example 2 of the present invention.

FIG. 10 is the absorption spectrum of the absorber in Comparative Example 3 of the present invention.

FIG. 11 is the absorption spectrum of the absorber in Comparative Example 4 of the present invention.

In the figure, 1, metal tungsten block; 2, silicon dioxide medium; 3, strip metal tungsten; 4, base layer; 5, chromium film layer; 6, silicon nitride layer; 7, graphene layer; 8, three Grating cascade structure layers.

Detailed ways

The following is a description of specific embodiments of the present invention in conjunction with the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

Example 1

A three-grating cascade structure as shown in Figure 1 and Figure 2 is composed of three-grating cascade units. The three-grating cascade units include metal tungsten block 1, silicon dioxide medium 2 and strip metal sequentially from left to right. Tungsten 3, metal tungsten block 1 has a width of 427.352 nm and a height of 133.34 nm; silicon dioxide medium 2 has a width of 309.137 nm and a height of 416.8 nm; strip-shaped metal tungsten 3 has a width of 235.431 nm and a height of 333.34 nm.

Example 2

A triple grating cascading structure is composed of three grating cascading units. The three grating cascading units sequentially include a metal tungsten block, a silicon dioxide medium and a strip-shaped metal tungsten from left to right. The width of the metal tungsten block is 453.272 nanometers. The height is 124.86 nm; the width of the silicon dioxide medium is 314.271 nm and the height is 415.82 nm; the width of the strip metal tungsten is 232.457 nm and the height is 326.91 nm.

Example 3

A triple grating cascading structure is composed of three grating cascading units. The three grating cascading units sequentially include a metal tungsten block, a silicon dioxide medium and a strip-shaped metal tungsten from left to right. The width of the metal tungsten block is 481.362 nanometers. The height is 138.74 nanometers; the width of the silicon dioxide medium is 318.176 nanometers and the height is 446.12 nanometers; the width of the strip metal tungsten is 284.65 nanometers and the height is 341.71 nanometers.

Example 4

An ultra-broadband absorber based on the three-grating cascade structure of Embodiment 1 as shown in FIG. 3, the absorber sequentially includes from bottom to top:

Base layer 4 with a thickness of 0.2 mm,

A chromium film layer 5 having a thickness of 110 nanometers formed on the surface of the base layer; and

a silicon nitride layer 6 having a thickness of 383.42 nanometers formed on the chromium film layer; and

a graphene layer 7 having a thickness of 34 nanometers formed on the silicon nitride layer; and

The triple grating cascade structure layer 8 in Example 1 is formed on the graphene layer.

The absorption spectrum of the absorber obtained in this example is shown in FIG. 4 . It can be seen from the figure that the absorption spectrum range of the absorber is 0.2-2.58 microns, including part of the ultraviolet light band, all the visible light band, all the near-infrared light band and part of the short-wave infrared band; the highest absorption rate can reach 97.4%.

5 is the absorption spectrum generated by the metal tungsten block 1, the silicon dioxide medium 2 and the strip-shaped metal tungsten 3 in the triple grating cascade structure of Example 1 as the top part of the absorber respectively.

Example 5

An ultra-broadband absorber based on the triple grating cascade structure in Example 2, the absorber sequentially includes from bottom to top: Figure 5

A base layer with a thickness of 0.2 mm,

a 105 nm thick layer of chromium formed on the surface of the base layer; and

a silicon nitride layer having a thickness of 365.35 nanometers formed on the chromium film layer; and

a graphene layer having a thickness of 51 nanometers formed on the silicon nitride layer; and

The triple grating cascade structure layer in Example 2 is formed on the graphene layer.

The absorption spectrum of the absorber obtained in this example is shown in FIG. 6 . It can be seen from Figure 6 that the absorption spectrum of the absorber ranges from 0.2 to 2.2 microns, including part of the ultraviolet light band, all the visible light band, all the near-infrared light band and part of the short-wave infrared band; the highest absorption rate can reach 91.5%.

Example 6

An ultra-broadband absorber based on the triple grating cascade structure in Embodiment 3, the absorber sequentially includes:

A base layer with a thickness of 0.2 mm,

a 115 nanometer thick layer of chromium formed on the surface of the base layer; and

a silicon nitride layer having a thickness of 365.35 nanometers formed on the chromium film layer; and

a graphene layer having a thickness of 85 nanometers formed on the silicon nitride layer; and

The triple grating cascade structure layer in Example 3 is formed on the graphene layer.

The absorption spectrum of the absorber obtained in this example is shown in FIG. 7 . It can be seen from Figure 7 that the absorption spectrum of the absorber ranges from 0.2 to 2.01 microns, including part of the ultraviolet light band, all the visible light band, all the near-infrared light band and part of the short-wave infrared band; the highest absorption rate can reach 98.8%.

Comparative Example 1

The difference between this comparative example and Example 4 is only that the width ratio of the metal tungsten block, silicon dioxide medium and strip metal tungsten in the triple grating cascade structure layer in the absorber of this comparative example is 3:1.5:1.

The absorption spectrum of the absorber obtained in this comparative example is shown in FIG. 8 . It can be seen from FIG. 8 that compared with Example 4, the absorption rate of the absorber is reduced, especially the absorption rate in the short-wave and near-infrared band is significantly reduced.

Comparative Example 2

The difference between this comparative example and Example 4 is only that the width ratio of the metal tungsten block, silicon dioxide medium and strip metal tungsten in the triple grating cascade structure layer in the absorber of this comparative example is 1:1:1.

The absorption spectrum of the absorber obtained in this comparative example is shown in FIG. 9 . As can be seen from FIG. 9 , compared with Example 4, the absorption spectral bandwidth of the absorber is only 1.2 μm, and the absorption rate in the infrared band decreases significantly.

Comparative Example 3

The difference between this comparative example and Example 4 is only that the height ratio of the metal tungsten block, silicon dioxide medium and strip metal tungsten in the triple grating cascade structure layer in the absorber of this comparative example is 3:5:3.

The absorption spectrum of the absorber obtained in this comparative example is shown in FIG. 10 . It can be seen from FIG. 10 that, compared with Example 4, the absorption spectrum of the absorber is in the range of 0.2-2.33 microns, but a low absorptivity range of 1.21-1.96 microns appears.

Comparative Example 4

The difference between this comparative example and Example 4 is only that the height ratio of the metal tungsten block, silicon dioxide medium and strip metal tungsten in the triple grating cascade structure layer in the absorber of this comparative example is 3:12:10.

The absorption spectrum of the absorber obtained in this comparative example is shown in FIG. 11 . It can be seen from Fig. 10 that, compared with Example 4, the absorption spectrum of the absorber is in the range of 0.2-2.39 microns, but a low absorption rate range of 1.47-2.09 microns appears.

To sum up, the present invention adopts the top-level cascaded three-grating structure in the same unit, through the composite coupling effect between multiple modes such as grating diffraction mode, cavity resonance mode formed between different materials, and surface plasmon resonance mode. To achieve the superposition broadening of the absorption spectral bandwidth and the improvement of the absorption rate.

Although the present invention has been described in detail and cited some specific embodiments, it will be apparent to those skilled in the art that various changes or modifications can be made without departing from the spirit and scope of the present invention.

Claims (6)

1. a three-grating cascade structure, is characterized in that, is made up of three-grating cascade unit, and three-grating cascade unit comprises metal tungsten block, silicon dioxide medium and strip-shaped metal tungsten sequentially from left to right; The width ratio of metal tungsten block, silicon dioxide medium and strip metal tungsten is 3:(1.8-2.5):(1.5-2.2); the height ratio of the metal tungsten block, silicon dioxide medium and strip metal tungsten for 3:(7-10):(5-8); The period of the triple grating cascade unit is the sum of the widths of the metal tungsten block, the silicon dioxide medium and the strip metal tungsten, and the sum is 900-1120 nanometers; The width of the metal tungsten block is 400-500 nanometers, and the height is 100-150 nanometers; the width of the silicon dioxide medium is 300-320 nanometers, and the height is 400-450 nanometers; the width of the strip-shaped metal tungsten is 200 nanometers. -300nm, 300-350nm in height. 2. An ultra-wideband absorber based on the triple grating cascade structure according to claim 1, wherein the absorber comprises: basal layer; a chromium film layer formed on the surface of the base layer; and a silicon nitride layer formed on the chromium film layer; and a graphene layer formed on the silicon nitride layer; and The triple grating cascade structure layer is formed on the graphene layer. 3 . The ultra-wideband absorber according to claim 2 , wherein the base layer is silicon or silicon dioxide, and the thickness of the base layer is 0.1-5 mm. 4 . 4. The ultra-wideband absorber according to claim 2, wherein the thickness of the chromium film layer is 100-120 nanometers. 5. The ultra-wideband absorber according to claim 2, wherein the thickness of the silicon nitride layer is 100-500 nanometers. 6. The ultra-wideband absorber according to claim 2, wherein the graphene layer has a thickness of 30-100 nanometers.

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