Wide-spectrum optical anti-reflection method based on phase gradient compensation and amplitude constraint

Abstract

The invention discloses a wide-spectrum optical anti-reflection method based on phase gradient compensation and amplitude constraint, and relates to the technical field of optical transparent electric conductor design. According to the invention, the amplitude of the reflection coefficient of each interface is controlled by selecting the dielectric material with the corresponding refractive index in different wavebands, so that the amplitude condition that reflection coefficient cancellation realizes ultra-thin metal optical anti-reflection is met. And the phase of the reflection coefficient is compensated by adjusting the thickness of the medium, so that the phase condition that reflection coefficient cancellation realizes ultra-thin metal optical anti-reflection is met. The corresponding refractive index range and thickness range can be found according to the given wave band needing to realize transparent conduction, and the corresponding dielectric material can be quickly found according to the refractive index range and the thickness range, so that the time cost required for screening the anti-reflection dielectric material with the composite structure is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the field of optical transparent conductor design, and more specifically, relates to a broadband optical antireflection method based on phase gradient compensation and amplitude constraint. Background Art

[0002] Transparent conductors can simultaneously achieve optical transparency and current conduction, and thus have a wide range of applications in optical information detection and energy conversion technologies, including photodetectors, display screens, light-emitting diodes, and solar cells. To meet the needs of people's daily production and life, transparent conductors not only need to have good electrical conductivity, but also need to achieve high transmittance in a wide wavelength band to ensure the full utilization of energy. However, the conductivity and transparency of transparent conductors are contradictory to each other, and it is often difficult to simultaneously achieve high conductivity and high transparency, which cannot meet the needs of production and life. Therefore, how to solve the contradiction between conductivity and transparency is an important problem that urgently needs to be faced to improve the performance of transparent conductors and achieve more extensive applications.

[0003] The traditional method to solve the contradiction between conductivity and transparency is achieved by using indium tin oxide. Indium tin oxide is prepared by doping a small amount of tin into indium oxide, and it can achieve a very high transmittance in the visible wavelength band and at the same time has strong electrical conductivity. However, indium tin oxide has a low transmittance in the infrared wavelength band and cannot achieve enhanced transmission in a wide wavelength band, so it is difficult to meet the full utilization of energy. In addition, the scarcity and high price of indium, and the fact that the preparation needs to be carried out under high-temperature conditions and cannot be prepared on low-melting-point substrates limit the widespread use of indium tin oxide.

[0004] Recently, with the rapid development of ultra-thin metal preparation technology, a major breakthrough has been made in the thickness of ultra-thin metals that can be prepared, and some ultra-thin metal thicknesses can even be as low as 2 nm. Ultra-thin metals themselves have good electrical conductivity. By reducing the thickness of ultra-thin metals, their absorption of incident light can be reduced, thereby achieving optical antireflection. In addition, by introducing dielectric layers on both sides of the ultra-thin metal as antireflection films, the reflection of incident light can be reduced, further improving optical transparency. Therefore, designing ultra-thin metal-dielectric composite structures to solve the contradiction between high conductivity and high transparency is one of the current hot topics.

[0005] 1. Patent 202011266720.4, "A broadband antireflection film and its preparation method", describes a preparation method of sequentially depositing a Cu film layer and a MgF 2 film layer on a substrate, which improves the transparency of the substrate in the range of 400 - 1000 nm and has a certain electrical conductivity. However, the deposition of the Cu film with a thickness between 2 - 3.5 nm is difficult to process, and the thinner metal layer will affect the conductivity.

[0006] 2. Patent 202311724281.0, "Preparation Method of Transparent Electromagnetic Shielding Film with Sandwich Structure Based on Ultra-Thin Silver Film", describes a preparation method of sequentially depositing an ultra-thin silver-transparent oxide-transparent oxide sandwich structure on a transparent substrate, which satisfies that the transparent substrate has good conductivity and realizes enhanced transparency in the visible band. However, the transmittance in the visible band is relatively low, less than or equal to 80%, and the enhanced transmittance in the broadband is not achieved.

[0007] 3. Cheng Zhang et al. from the University of Michigan reported a method for preparing ultra-thin metal based on doping with a small amount of aluminum. By adopting the metal co-doping deposition method, a small amount of doped metal aluminum was continuously incorporated at a certain rate during the deposition of metal silver, and ultra-thin metal silver with a smooth surface (RMS ≤ 1 nm) was prepared. The transmittance in the visible band can reach 80%, and the sheet resistance is lower than 15.3 Ω / sq. -1 It has good conductivity. However, the absorption of this ultra-thin doped metal in the infrared band is relatively high, and it cannot meet the enhanced transmittance in the broadband. (Cheng Zhang et al., "An Ultrathin, Smooth, and Low-Loss Al-Doped Ag Film and Its Application as a Transparent Electrode in Organic Photovoltaics". Advanced Materials, 2014, 26: 5696-5701)

[0008] 4. Rinu Abraham Maniyara et al. reported a method for achieving transparent conductivity based on dielectric-ultra-thin metal-dielectric (DMD). By depositing aluminum-doped zinc oxide and titanium dioxide on both sides of ultra-thin metal silver, a DMD composite structure was prepared, and the transmittance of 91.6% can be achieved in the visible band, and the sheet resistance is as low as 5.75 Ω / sq. -1 It has good conductivity. However, this DMD composite structure only realizes the enhanced transmittance in the visible band, and does not consider the enhanced transmittance in the broadband and cannot meet the full utilization of energy. (Rinu Abraham Maniyara et al., "An antireflection transparent conductor with ultra-low optical loss (<2%) and electrical resistance (<6 Ω / sq -1 )". Nature Communication, 2016, 7-13371)

[0009] In summary, the main problems of the existing technologies are as follows:

[0010] 1. It is difficult to achieve enhanced transmission in the near-infrared band: The free-carrier reflection edge of ultra-thin metals is usually within the visible band range. For near-infrared light with a wavelength greater than the free-carrier reflection edge, it will be largely reflected by the plasma, resulting in a decrease in the near-infrared transmittance. In addition, as the wavelength increases, the extinction coefficient of the ultra-thin metal also increases, causing an increase in the absorption of near-infrared light by the ultra-thin metal and a decrease in the near-infrared transmittance. Therefore, how to achieve enhanced transmission in the near-infrared band is one of the urgent problems to be solved.

[0011] 2. It is difficult to ensure conductivity when achieving broadband anti-reflection: Usually, it is impossible to increase the transmittance by reducing the reflection of near-infrared light by changing the free-carrier reflection edge of the ultra-thin metal. And using the method of reducing the thickness of the ultra-thin metal to reduce the absorption of near-infrared light to increase the near-infrared transmittance is not only difficult to prepare with a low improvement in near-infrared transmittance, but also will greatly affect the conductivity of the ultra-thin metal. Therefore, there is an urgent need to find a design method that can ensure conductivity while achieving broadband anti-reflection.

[0012] 3. Lack of specific design principles and methods for broadband transparent conductive composite structures: The existing methods for achieving transparent conductivity mainly focus on the preparation process, and the composite structures prepared according to the given relevant parameters of the dielectric layer can only achieve transparent conductivity in the visible band. In addition, the given composite structures only have relevant parameters and no specific design methods, and it is impossible to design corresponding composite structures to achieve anti-reflection according to any given broadband. Therefore, there is an urgent need to find a design method that can obtain the corresponding anti-reflection composite structure according to the given broadband.

[0013] In view of this, the present invention is specifically proposed. Summary of the Invention

[0014] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a broadband optical anti-reflection method based on phase gradient compensation and amplitude constraint, which solves the problems raised in the above background technology.

[0015] To solve the above technical problems, the basic concept of the technical solution adopted by the present invention is:

[0016] A broadband optical anti-reflection method based on phase gradient compensation and amplitude constraint, by selecting appropriate substrates, dielectric materials, and the thickness of the ultra-thin metal layer, optimizing the optical structure within the target band range to meet the amplitude constraint of achieving destructive reflection coefficient and the requirement of propagation phase compensation, thereby achieving broadband optical anti-reflection, which includes the following steps:

[0017] I. Select a dielectric material with a refractive index of m corresponding to the band to be anti-reflected;

[0018] II. Through Calculate the equivalent wavelength λ of the antireflection band, where λ 1 and λ 2 are the minimum and maximum wavelengths within the selected band, respectively;

[0019] III. Calculate the reflection coefficient r 12 and the reflection phase at the equivalent wavelength, where n metal and k metal are the real and imaginary parts of the refractive index of the ultrathin metal, respectively;

[0020] IV. Compensate the reflection phase of r 12 through the dielectric layer A to obtain the total phase of r 12 By reversing r and r 12 and r 01 to obtain the magnitude of the propagation phase φ2 in the dielectric layer A, and then obtain the thickness d 1 of the dielectric layer A;

[0021] V. According to the obtained propagation phase φ 2 in the dielectric layer A plus the propagation phase φ 3 in the dielectric layer B, the total phase of r 34 can be obtained as By aligning r 34 and r 01 on the same straight line, the magnitude of the propagation phase φ 3 in the dielectric layer B is obtained, and then the thickness d 2 of the dielectric layer B is obtained;

[0022] VI. According to the calculation and design results of steps I to V, determine the specific parameters of the dielectric layer A and the dielectric layer B, including the refractive index m and thickness d 1 and d 2 of the dielectric material, so as to obtain the composite structure of the dielectric layer A / ultrathin metal / dielectric layer B.

[0023] It should be noted that: select the dielectric material with the corresponding refractive index according to the antireflection band required to constrain the amplitude of the reflection coefficient at each interface, so as to meet the amplitude condition for the cancellation of the reflection coefficient to achieve optical antireflection of the ultrathin metal; calculate the corresponding equivalent wavelength according to the antireflection band required; calculate the reflection phase φ 12 of r 1 at the equivalent wavelength; compensate the total phase of r 2 by adjusting the propagation phase φ 12 of the dielectric layer A to obtain the thickness d 1 of the dielectric layer A; adjust the propagation phase φ 2 of the dielectric layer B according to the obtained propagation phase φ 3 of the dielectric layer A to achieve the compensation of the total phase of r 34The compensation of the total phase yields the thickness d of the dielectric layer B 2 , thus satisfying the phase condition for the cancellation of the reflection coefficient to achieve the ultra-thin metal optical antireflection; according to the obtained dielectric layer parameters, the composite structure for achieving broadband optical antireflection is dielectric layer A / ultra-thin metal / dielectric layer B. This broadband optical antireflection method can calculate the dielectric layer parameters according to the given wavelength band to obtain the corresponding composite structure to achieve enhanced transmission of the ultra-thin metal in a wide wavelength band. Further, by changing the thickness of the ultra-thin metal, composite structures with different conductivity and transparency can be obtained. When the thickness of the ultra-thin metal is less than 10 nm, the composite structure exhibits high transparency, and when the thickness of the ultra-thin metal is greater than 10 nm, the composite structure exhibits high conductivity.

[0024] Optionally, in step I, within the visible wavelength band, the selected dielectric material with a refractive index between 1.7 and 2.1 includes, but is not limited to, alumina and tantalum pentoxide; the visible wavelength band refers to the spectral range between 400 nm and 700 nm. This range includes the light visible to our human eyes.

[0025] Within the infrared wavelength band of 800 - 2000 nm, the selected dielectric material with a refractive index between 2.1 and 2.5 includes, but is not limited to, titanium dioxide and zinc sulfide;

[0026] Within the infrared wavelength band of 2000 - 3000 nm, the selected dielectric material with a refractive index between 2.6 and 3.5 includes, but is not limited to, α-Si.

[0027] Optionally, the substrate is an optically transparent material, including, but not limited to, one of quartz and calcium fluoride. The substrate is used to support the entire composite structure and provide optical transmission performance.

[0028] Optionally, the ultra-thin metal includes, but is not limited to, one of gold, silver, copper, and aluminum.

[0029] Optionally, when using TiO 2 as the dielectric material, a TiO 2 / Ag / TiO 2 composite structure is formed, where TiO 2 is the dielectric layer, Ag is the ultra-thin metal layer, the thickness of TiO 2 is 80 - 100 nm, the thickness of silver is 4 - 30 nm, and quartz is used as the substrate.

[0030] Optionally, when using α-Si as the dielectric material, an α-Si / Ag / α-Si composite structure is formed, where α-Si is the dielectric layer, Ag is the ultra-thin metal layer, the thickness of α-Si is 130 - 150 nm, the thickness of silver is 4 - 30 nm, and quartz is used as the substrate.

[0031] Optionally, in the visible wavelength band r 12The reflection phase φ 1 is 1.5π. By making the total phase of r 12 be 2π, the thickness d of the dielectric layer A is determined 1 , and then by making the total phase of the reflection coefficient r 34 be π, the thickness d of the dielectric layer B is determined 2 .

[0032] Optionally, in the infrared band, the reflection phase φ 12 of r 1 is π. By making the total phase of r 12 be 2π, the thickness d of the dielectric layer A is determined 1 , and then by making the total phase of the reflection coefficient r 34 be 2π, the thickness d of the dielectric layer B is determined 2 .

[0033] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art. Of course, any product implementing the present invention does not necessarily need to achieve all the advantages described below at the same time:

[0034] 1. The present invention proposes a method for selecting dielectric materials for broadband optical antireflection based on amplitude constraint. By selecting dielectric materials with corresponding refractive indices in different bands to control the amplitude of the reflection coefficient at each interface, the amplitude condition for realizing ultra-thin metal optical antireflection by reflection coefficient cancellation is satisfied. According to the given band for realizing transparent conductivity, the corresponding refractive index range can be found, and the corresponding dielectric materials can be quickly found according to the refractive index range, greatly reducing the time cost required for screening antireflection dielectric materials for composite structures.

[0035] 2. The present invention proposes a method for calculating the thickness of dielectric layers for broadband optical antireflection based on phase gradient change. By controlling the thicknesses of the dielectric layers A and B, the propagation phases φ 2 and φ 3 compensate the total phases of the reflection coefficients r 12 and r 34 in the range of 0.5π - π, so that in the reflection coefficient distribution diagram, r 12 is in the same direction as r 01 , and r 34 and r 01 are located on the same straight line, satisfying the phase condition for realizing ultra-thin metal optical antireflection by reflection coefficient cancellation. According to the given band for realizing transparent conductivity, the thicknesses of the corresponding dielectric layers can be quickly calculated, greatly narrowing the thickness range required for optimizing the dielectric layers and improving the optimization efficiency of the composite structure.

[0036] 3. The present invention proposes a method for achieving broadband transparent conductivity based on a composite structure of dielectric layer A / ultrathin metal / dielectric layer B. According to the wavelength band for which transparent conductivity needs to be achieved, the corresponding composite structure of dielectric layer A / ultrathin metal / dielectric layer B can be obtained, and by adjusting the thickness of the ultrathin metal within the range of 4 - 30 nm, the optical transparency and conductivity of the composite structure can be changed. When the thickness of the ultrathin metal is less than 10 nm, the absorption of incident light is small, and it has good optical transparency in a broadband; when the thickness of the ultrathin metal is greater than 10 nm, the sheet resistance of the composite structure is small, and it has good conductivity. By adjusting the thickness of the ultrathin metal, the requirements for optical transparency and conductivity in different situations can be met, and this method is convenient, fast, and easy to implement.

[0037] The following further describes in detail the specific implementation manners of the present invention with reference to the accompanying drawings. Description of the Drawings

[0038] The drawings in the following description are only some embodiments. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. In the drawings:

[0039] Figure 1 is a schematic diagram of the composite structure of dielectric layer A / ultrathin metal / dielectric layer B of the present invention.

[0040] Figure 2 is a schematic diagram of compensating the r 12 reflection phase by dielectric layer A of the present invention.

[0041] Figure 3 is a schematic diagram of compensating the r 34 propagation phase by dielectric layer B of the present invention.

[0042] Figure 4 is a schematic diagram of compensating the r 34 propagation phase by dielectric layer B of the present invention.

[0043] Figure 5 is a schematic diagram of the antireflection composite structure designed within the wavelength band of 400 - 1750 nm of the present invention.

[0044] Figure 6 is a schematic diagram of the antireflection composite structure designed within the wavelength band of 1750 - 3000 nm of the present invention.

[0045] Figure 7 is a schematic diagram of the transmittance of the antireflection composite structure designed within the wavelength band of 400 - 1750 nm of the present invention.

[0046] Figure 8It is a transmittance schematic diagram of the antireflection composite structure designed within the wavelength range of 1750 - 3000 nm according to the present invention.

[0047] It should be noted that these drawings and textual descriptions are not intended to limit the scope of the concept of the present invention in any way, but to illustrate the concept of the present invention to those skilled in the art by referring to specific embodiments. Detailed Description of the Specific Embodiment

[0048] The present invention will now be further described in detail with reference to the accompanying drawings.

[0049] Please refer to Figure 1-8 As shown, in this embodiment, an optical antireflection method with a wide spectral band based on phase gradient compensation and amplitude constraint is provided. By selecting appropriate substrates 4, dielectric materials, and the thickness of the ultrathin metal layer, the optical structure is optimized within the target wavelength range to meet the amplitude constraint for canceling the reflection coefficient and the requirement for compensating the propagation phase, thereby achieving optical antireflection with a wide spectral band. The method includes the following steps:

[0050] I. Select a dielectric material with a refractive index of m corresponding to the wavelength band that needs antireflection;

[0051] II. Calculate the equivalent wavelength λ of the wavelength band that needs antireflection through where λ 1 and λ 2 are respectively the minimum and maximum wavelengths within the selected wavelength band; To ensure wide - band antireflection, according to the obtained equivalent wavelength, it can ensure that the phase changes generated when changing from the equivalent wavelength to the minimum wavelength λ 1 and the maximum wavelength λ 2 are the same

[0052] III. Calculate the reflection phase 12 of the reflection coefficient r at the equivalent wavelength, where n metal and k metal are respectively the real part and the imaginary part of the refractive index of the ultrathin metal 2;

[0053] IV. Compensate the reflection phase of r 12 through the dielectric layer A1 to obtain the total phase of r 12 as By making r 12 opposite to r 01 , the magnitude of the propagation phase φ 2 in the dielectric layer A1 is obtained, and thus the thickness d 1 of the dielectric layer A1 is obtained;

[0054] V. According to the obtained propagation phase φ 2 in the dielectric layer A1 plus the propagation phase φ in the dielectric layer B33 , the total phase of r 34 is By making r 34 and r 01 lie on the same straight line, the propagation phase φ 3 in the dielectric layer B3 is obtained, so as to obtain the thickness d 2 of the dielectric layer B3;

[0055] VI. According to the calculation and design results of steps I to V, determine the specific parameters of the dielectric layer A1 and the dielectric layer B3, including the refractive index m and thickness d 1 of the dielectric material, 2 so as to obtain the composite structure of the dielectric layer A1 / ultra-thin metal 2 / dielectric layer B3.

[0056] It should be noted that: according to the waveband to be antireflected, the dielectric material with a refractive index of m is selected to constrain the amplitude of the reflection coefficient at each interface within this waveband, so as to meet the amplitude condition for realizing the optical antireflection of the ultra-thin metal by the cancellation of the reflection coefficients. By changing the thickness of the dielectric layer, the propagation phase is used to compensate the total phase of the reflection coefficient within the range of 0.5π - π, so that each reflection coefficient lies on the same straight line in the vector distribution diagram, meeting the phase condition for realizing the optical antireflection of the ultra-thin metal by the cancellation of the reflection coefficients.

[0057] In this embodiment, in the visible waveband, the selected dielectric material with a refractive index between 1.7 and 2.1 includes, but is not limited to, alumina and tantalum pentoxide; the visible waveband refers to the spectral range between 400 nm and 700 nm. This range includes the light visible to our human eyes.

[0058] In the infrared waveband of 800 - 2000 nanometers, the selected dielectric material with a refractive index between 2.1 and 2.5 includes, but is not limited to, titanium dioxide and zinc sulfide;

[0059] In the infrared waveband of 2000 - 3000 nanometers, the selected dielectric material with a refractive index between 2.6 and 3.5 includes, but is not limited to, α-Si.

[0060] In this embodiment, the substrate 4 is an optically transparent material, which includes, but is not limited to, one of quartz and calcium fluoride. The substrate 4 is used to support the entire composite structure and provide optical transmission performance.

[0061] In this embodiment, the ultra-thin metal 2 includes, but is not limited to, one of gold, silver, copper and aluminum.

[0062] In this embodiment, when TiO 2 is used as the dielectric material, the TiO 2 / Ag / TiO 2 composite structure is formed, where TiO2 is the dielectric layer, Ag is the ultra-thin metal layer, TiO 2 has a thickness of 80 - 100 nm, the thickness of silver is 4 - 30 nm, and quartz is used as the substrate 4.

[0063] In this embodiment, when α-Si is used as the dielectric material, an α-Si / Ag / α-Si composite structure is formed. Among them, α-Si is the dielectric layer, Ag is the ultra-thin metal layer, the thickness of α-Si is 130 - 150 nm, the thickness of silver is 4 - 30 nm, and quartz is used as the substrate 4.

[0064] In this embodiment, in the visible band r 12 's reflection phase φ 1 is 1.5π. By making the total phase of r 12 be 2π, the thickness d of the dielectric layer A1 is determined 1 , and then by making the total phase of the reflection coefficient r 34 be π, the thickness d of the dielectric layer B3 is determined 2 .

[0065] In this embodiment, in the infrared band r 12 's reflection phase φ 1 is π. By making the total phase of r 12 be 2π, the thickness d of the dielectric layer A1 is determined 1 , and then by making the total phase of the reflection coefficient r 34 be 2π, the thickness d of the dielectric layer B3 is determined 2 .

[0066] As shown by Figure 1 in the dielectric layer A1 / ultra-thin metal 2 / dielectric layer B3 composite structure of the present invention. Among them, 1 is the dielectric layer A; 2 is the ultra-thin metal; 3 is the dielectric layer B; 4 is the substrate. r 01 , r 12 , r 23 and r 34 are the reflection coefficients of the corresponding interfaces respectively.

[0067] As shown by Figure 2 in Example 1: By compensating the reflection phase of r 12 The reflection phase

[0068] The reflection coefficient r 12 itself has a reflection phase φ 1 , by adjusting the thickness d of the dielectric layer A1 1 to change the propagation phase φ 2 , making r 12 and r 01 in opposite directions, so as to achieve the purpose of antireflection and enhanced transmission.

[0069] As shown by Figure 3As shown in the figure, Example 2: Compensate r through dielectric layer B3 34 Propagation phase

[0070] Reflection coefficient r after passing through dielectric layer A1 34 Has a propagation phase φ 2 , By adjusting the thickness d of dielectric layer B3 2 Change the propagation phase φ 3 , So that r 34 And r 01 Have the same direction, so as to act together with r 01 To achieve the cancellation and antireflection of r 12 .

[0071] From Figure 4 As shown in the figure, Example 3: Compensate r through dielectric layer B3 34 Propagation phase

[0072] Reflection coefficient r after passing through dielectric layer A1 34 Has a propagation phase φ 2 , By adjusting the thickness d of dielectric layer B3 2 Change the propagation phase φ 3 , So that r 34 And r 01 Have opposite directions, so as to act together with r 12 To achieve the cancellation and antireflection of r 01 .

[0073] From Figure 5 As shown in the figure, Example 4: An antireflection composite structure designed in the wavelength range of 400 - 1750 nm.

[0074] Through the above design method, a composite structure that realizes antireflection in the wavelength range of 400 - 1750 nm can be obtained as TiO 2 / Ag / TiO 2 . Among them, 5 is dielectric layer A1 with the material of TiO 2 , and the thickness is between 80 - 100 nm; 6 is ultra-thin metal silver, and the thickness is between 4 - 30 nm; 7 is dielectric layer B3 with the material of TiO 2 , and the thickness is between 80 - 100 nm; 8 is the substrate made of quartz.

[0075] From Figure 6 As shown in the figure, Example 4: An antireflection composite structure designed in the wavelength range of 1750 - 3000 nm, and its structure is α-Si / Ag / α-Si. Among them, 9 is dielectric layer A made of α-Si, and the thickness is between 130 - 150 nm; 6 is ultra-thin metal silver, and the thickness is between 4 - 30 nm; 10 is dielectric layer B made of α-Si, and the thickness is between 130 - 150 nm; 8 is the substrate made of quartz.

[0076] As shown by Figure 7 the figure, it is the transmittance simulation result of the antireflection composite structure designed within the wavelength range of 400 - 1750 nm according to the present invention. From the simulation result, within the wavelength range of 400 - 1750 nm, the average transmittance of the composite structure is increased to 83%, and wide-band optical antireflection can be achieved

[0077] As shown by Figure 8 the figure, it is the transmittance simulation result of the antireflection composite structure designed within the wavelength range of 1750 - 3000 nm according to the present invention. From the simulation result, within the wavelength range of 1750 - 3000 nm, the average transmittance of the composite structure is increased to 80%, and wide-band optical antireflection can be achieved.

[0078] The present invention is not limited to the above embodiments. Any person should know that structural changes made under the inspiration of the present invention, as long as they have the same or similar technical solutions as the present invention, shall fall within the protection scope of the present invention. The technologies, shapes, and structures not described in detail in the present invention are all well-known technologies.

Claims

1. A wide-band optical anti-reflection method based on phase gradient compensation and amplitude constraint, characterized in that: By selecting an appropriate substrate (4), dielectric material and the thickness of the ultra-thin metal layer, the optical structure is optimized within the target wavelength range to meet the amplitude constraint and propagation phase compensation requirements for achieving reflection coefficient cancellation, thereby achieving wide-band optical anti-reflection, which includes the following steps: I. Select the dielectric material with the corresponding refractive index m according to the wavelength band to be enhanced; II. Pass Calculate the equivalent wavelength λ of the band that needs to be enhanced, where λ1 and λ2 are the minimum and maximum wavelengths in the selected band respectively; III. Calculate the reflection coefficient r at the equivalent wavelength 12 The reflection phase Among them, n metal and k metal are the real and imaginary parts of the refractive index of the ultrathin metal (2), respectively; IV. Through the dielectric layer A(1) 12 The reflection phase is compensated to obtain r 12 The total phase is By making 12 With r 01 Conversely, the magnitude of the propagation phase φ2 in the dielectric layer A(1) is obtained, thereby obtaining the thickness d1 of the dielectric layer A(1); V. Based on the propagation phase φ2 in dielectric layer A (1) plus the propagation phase φ3 in dielectric layer B (3), we can get r 34 The total phase is By making 34 With r 01 Located on the same straight line, the magnitude of the propagation phase φ3 in the dielectric layer B(3) is obtained, thereby obtaining the thickness d2 of the dielectric layer B(3); VI. Based on the calculation and design results of steps I to V, the specific parameters of dielectric layer A (1) and dielectric layer B (3) are determined, including the refractive index m and thicknesses d1 and d2 of the dielectric material, thereby obtaining a composite structure of dielectric layer A (1) / ultra-thin metal (2) / dielectric layer B (3).

2. The method for wide-band optical anti-reflection based on phase gradient compensation and amplitude constraint according to claim 1, characterized in that: In step I, in the visible wavelength band, the dielectric material selected has a refractive index between 1.7 and 2.1, including but not limited to aluminum oxide and tantalum pentoxide; In the infrared band of 800-2000 nanometers, the dielectric material with a refractive index between 2.1 and 2.5 includes but is not limited to titanium dioxide and zinc sulfide; In the infrared band of 2000-3000 nanometers, the dielectric material with a refractive index of 2.6 to 3.5 is selected, including but not limited to α-Si.

3. The method for wide-band optical anti-reflection based on phase gradient compensation and amplitude constraint according to claim 1, characterized in that: The substrate (4) is an optically transparent material, including but not limited to quartz and calcium fluoride. The substrate (4) is used to support the entire composite structure and provide optical transmission performance.

4. The method for wide-band optical anti-reflection based on phase gradient compensation and amplitude constraint according to claim 1, characterized in that: The ultra-thin metal (2) includes but is not limited to one of gold, silver, copper and aluminum.

5. The method for wide-band optical anti-reflection based on phase gradient compensation and amplitude constraint according to claim 1, characterized in that: When TiO2 is used as the dielectric material, a TiO2 / Ag / TiO2 composite structure is formed, wherein TiO2 is the dielectric layer, Ag is the ultra-thin metal layer, the thickness of TiO2 is 80-100nm, the thickness of silver is 4-30nm, and quartz is used as the substrate (4).

6. The method for wide-band optical anti-reflection based on phase gradient compensation and amplitude constraint according to claim 1, characterized in that: When α-Si is used as the dielectric material, an α-Si / Ag / α-Si composite structure is formed, wherein α-Si is the dielectric layer, Ag is the ultra-thin metal layer, the thickness of α-Si is 130-150nm, the thickness of silver is 4-30nm, and quartz is used as the substrate (4).

7. The method for wide-band optical anti-reflection based on phase gradient compensation and amplitude constraint according to claim 1, characterized in that: In the visible band 12 The reflection phase φ1 is 1.5π, by making r 12 The total phase is 2π to determine the thickness d1 of the dielectric layer A(1), and then the reflection coefficient r 34 The total phase is π, which determines the thickness d2 of the dielectric layer B (3).

8. The method for wide-band optical anti-reflection based on phase gradient compensation and amplitude constraint according to claim 1, characterized in that: In the infrared band 12 The reflection phase φ1 is π, by making r 12 The total phase is 2π, which determines the thickness d1 of the dielectric layer A(1), and then the reflection coefficient r 34 The total phase is 2π, which determines the thickness d2 of the dielectric layer B (3).

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