Intermediate infrared broadband antireflection film and preparation method and application thereof

Abstract

The invention relates to the technical field of optical thin film design and preparation, in particular to a mid-infrared broadband antireflection film and a preparation method and application thereof.The structure of the broadband antireflection film is AIR (aLbH) cSUB (bHaL) cAIR, SUB represents a substrate, AIR represents an incident medium and an emergent medium, H represents a high-refractive-index film layer with a high refractive index value of 2-3.5, L represents a low-refractive-index film layer with a low refractive index value of 1-1.8, and bHaL represents a high-refractive-index film layer with a high refractive index value of 2-3.5. B and a respectively represent the lambda / 4 optical thickness of the high and low refractive index film layers, and c is the periodicity and is greater than or equal to 1 and less than or equal to 3. According to the intermediate infrared broadband antireflection film with the structure, the high-refractive-index film layer material and the low-refractive-index film layer material are matched with each other, the intermediate infrared broadband antireflection film which is simple in film system structure and high in transmittance can be obtained through design, and the intermediate infrared broadband antireflection film has important significance in improving the performance of an infrared optical device and widening the application range of the infrared optical device.

Description

Technical Field

[0001] The present invention relates to the technical field of optical film design and preparation, and in particular to a mid-infrared broadband anti-reflection film and a preparation method and application thereof. Background Art

[0002] In the field of optical technology, infrared optical devices have attracted much attention due to their wide applications in infrared detection, remote sensing, communications, medical diagnosis and other fields. In particular, in the mid-infrared band of 2.0~5.0μm, due to its unique absorption, reflection and transmission characteristics, infrared light in this band plays a vital role in many application scenarios. However, traditional optical window substrate materials often have insufficient transmittance in this band, which seriously restricts the performance improvement and application expansion of infrared optical devices.

[0003] In order to improve the transmittance of infrared optical devices in the mid-infrared band, researchers have been exploring and developing various anti-reflection film technologies. Anti-reflection film is an optical film that achieves interference cancellation by precisely controlling the film thickness and refractive index to reduce the reflection of light at the interface and increase the transmission. However, most of the existing anti-reflection film technologies are optimized for specific wavelengths or narrower bands, and it is difficult to meet the high transmittance requirements within the wide spectral range of the mid-infrared band. The larger the spectral bandwidth, the more complex the combination of film materials required, and the more film layers and the more types of film materials, which not only increases the process cost, but also is not conducive to the realization of the process, and the stability and repeatability of the film are deteriorated.

[0004] Most of the existing anti-reflection film technologies are optimized for specific wavelengths or narrow bands, which makes it difficult to meet the high transmittance requirements in the wide spectral range of the mid-infrared band. Moreover, the designed film system structure is often complex, which is not conducive to implementation, and the actual prepared samples are usually much lower than the designed values. Summary of the invention

[0005] The purpose of the present invention is to provide a mid-infrared broadband anti-reflection film and a preparation method and application thereof. By matching high-refractive index film layer materials and low-refractive index film layer materials, a mid-infrared broadband anti-reflection film with a simple film structure and high transmittance can be designed.

[0006] To achieve the above object, the present invention provides a mid-infrared broadband anti-reflection film, the structure of the broadband anti-reflection film is AIR|( a L b H) c |SUB|( b H a L) c |AIR, Among them, SUB represents the substrate, AIR represents the incident medium and the output medium, H represents the high refractive index film layer, the high refractive index value is 2~3.5 (@550nm), L represents the low refractive index film layer, the low refractive index value is 1~1.8 (@550nm), b and a Respectively represent the λ / 4 optical thickness of the high and low refractive index film layers, c is the number of cycles, 1≤ c ≤3.

[0007] Preferably, the substrate material includes, but is not limited to, one or more of double-polished single crystal silicon, sapphire and zinc sulfide crystal.

[0008] Preferably, the thickness of the substrate material is 0.2-40 mm.

[0009] Preferably, the high refractive index film layer material includes ZnS, TiO 2 , HfO 2 、ZrO 2 , Nb 2 O 5 and one or more of ZnSe.

[0010] Preferably, the low refractive index film layer material includes SiO 2 、Al 2 O 3 MgF 2 , BaF 2 , YF 3 and ThF 4 One or more of .

[0011] The above-mentioned method for preparing a mid-infrared broadband antireflection film comprises the following steps: S1, using a strong oxidizing inorganic solvent and an organic solvent to clean the substrate material in sequence, and drying the cleaned substrate material; S2, depositing a high refractive index film layer material and a low refractive index film layer material in sequence on one side of the substrate material dried in S1 to obtain a first end surface film layer; S3, depositing a high refractive index film layer material and a low refractive index film layer material in sequence on the other side of the substrate material dried in S1 to obtain a broadband anti-reflection film.

[0012] Preferably, in S1, the drying is carried out in an oven or a hot plate, the drying temperature is 100-200° C., and the drying time is 30-60 min.

[0013] Preferably, in S1, the inorganic solvent includes one or more of ammonia water, concentrated sulfuric acid and hydrogen peroxide, and the organic solvent includes alcohol.

[0014] Preferably, in S2 and S3, the deposition includes one of electron beam evaporation, magnetron sputtering and ion beam sputtering.

[0015] Preferably, in S2 and S3, the deposition temperature is 20-400° C., the deposition rate is 0.5-10 nm / min, and the deposition thickness is 10-600 nm.

[0016] The application of the above-mentioned mid-infrared broadband anti-reflection film is to improve the sensitivity of the infrared detection system and the emission efficiency of the optical parametric oscillator laser.

[0017] Therefore, the present invention adopts a mid-infrared broadband anti-reflection film of the above structure, and can design a mid-infrared broadband anti-reflection film with a simple film structure and high transmittance by matching high refractive index film layer materials and low refractive index film layer materials. The theoretical value of the transmittance in the 2.0~5.0μm band is 97.7%, and the actual value is greater than 92%, which is of great significance for improving the performance of infrared optical devices and broadening their application range.

[0018] The present invention realizes high transmittance performance of a mid-infrared window substrate in a wide spectral range through innovative design and preparation methods.

[0019] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flow chart of a method for preparing a mid-infrared broadband antireflection film according to the present invention; Figure 2 Schematic diagram of the structure of the broadband antireflection film in the present invention when c=1; Figure 3 It is a curve diagram of the transmittance simulation results of the broadband antireflection film and the blank substrate material before antireflection in Example 1 of the present invention; Figure 4 Graph showing the transmittance simulation results of the broadband anti-reflection film and the blank substrate material before anti-reflection in Example 2 of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and embodiments. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the usual meanings understood by people with ordinary skills in the field to which the present invention belongs. The above-mentioned features mentioned in the present invention or the features mentioned in the specific examples can be combined arbitrarily, and these specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of this application.

[0022] Example 1 The film system structure is designed based on conventional optical simulation software: the structure of the broadband antireflection film is AIR|1.44L1.32H|SUB|(1.32H1.44L)|AIR, where: a =1.44, b =1.32, c =1, the theoretical transmittance of the designed broadband antireflection film in the 2.0~5.0μm band is 97.7%. Figure 3 shown.

[0023] Among them, SUB represents the substrate material, AIR represents the incident medium and the output medium, H represents the high refractive index film layer, the high refractive index value is 2~3.5 (@550nm), L represents the low refractive index film layer, the low refractive index value is 1~1.8 (@550nm), b and a Respectively represent the λ / 4 optical thickness of the high and low refractive index film layers, c is the number of cycles.

[0024] The substrate material is double-polished single crystal silicon with a thickness of 0.5~40mm, and the high refractive index film material is TiO 2 , the low refractive index film material is MgF 2 .

[0025] The above-mentioned method for preparing the mid-infrared broadband antireflection film comprises the following steps: Figure 1 As shown, S1. Use a strong oxidizing inorganic solvent and an organic solvent alcohol to clean the substrate material in turn, and dry the cleaned substrate material in an oven at a drying temperature of 120° C. for 60 minutes.

[0026] S2, depositing high refractive index film material TiO on one side of the substrate material dried in S1 by electron beam evaporation. 2 And low refractive index film material MgF 2 The deposition temperature is 150°C, and the high refractive index film material is TiO 2 The deposition rate is 5.3 nm / min, TiO 2 The deposition thickness is 278nm, and the low refractive index film material is MgF 2 The deposition rate is 8.1 nm / min, MgF 2 The deposition thickness is 519 nm and the background vacuum is 5.0×10 -4 Pa, and obtain the first end surface film layer.

[0027] S3, depositing high refractive index film material TiO on the other side of the substrate material dried in S1 by electron beam evaporation. 2 And low refractive index film material MgF 2 , the deposition temperature is 150℃, the high refractive index film material is TiO2 The deposition rate is 5.3 nm / min, TiO 2 The deposition thickness is 286nm, and the low refractive index film material is MgF 2 The deposition rate is 8.1 nm / min, MgF 2 The deposition thickness is 529nm and the background vacuum is 5.0×10 -4 Pa, and a broadband antireflection film is obtained.

[0028] The high refractive index film material TiO deposited in S3 2 And low refractive index film material MgF 2 The total thickness error with the first end surface film layer is 2.2%.

[0029] The actual average transmittance of the broadband anti-reflection film and the blank substrate material before anti-reflection in the 2.0~5.0μm band is measured by a spectrophotometer or a wide-spectrum laser, and the actual values ​​are 93% and 53% respectively.

[0030] Example 2 The film system structure is designed based on conventional optical simulation software: the structure of the broadband antireflection film is AIR|1.45L1.38H|SUB|(1.38H1.45L)|AIR, where: a =1.45, b =1.38, c =1, the theoretical transmittance of the designed broadband antireflection film in the 2.0~5.0μm band is 97.1%. Figure 4 shown.

[0031] Among them, SUB represents the substrate material, AIR represents the incident medium and the output medium, H represents the high refractive index film layer, the high refractive index value is 2~3.5 (@550nm), L represents the low refractive index film layer, the low refractive index value is 1~1.8 (@550nm), b and a Respectively represent the λ / 4 optical thickness of the high and low refractive index film layers, c is the number of cycles.

[0032] The substrate material is double-polished single crystal silicon with a thickness of 0.2~20mm, and the high refractive index film material is Nb 2 O 5 , the low refractive index film material is YF 3 .

[0033] The above-mentioned method for preparing the mid-infrared broadband antireflection film comprises the following steps: S1. Use a strong oxidizing inorganic solvent and an organic solvent alcohol to clean the substrate material in turn, and dry the cleaned substrate material in an oven at a drying temperature of 120° C. for 60 minutes.

[0034] S2, magnetron sputtering is performed to deposit high refractive index film material Nb on one side of the substrate material dried in S1 2 O 5 And low refractive index film material YF 3 The deposition temperature is 120°C, and the high refractive index film material is Nb 2 O 5 The deposition rate is 2.0 nm / min, Nb 2 O 5 The deposition thickness is 307nm, and the low refractive index film material is YF 3 The deposition rate is 3.2nm / min, YF 3 The deposition thickness is 528nm and the background vacuum is 6.0×10 -4 Pa, and obtain the first end surface film layer.

[0035] S3, depositing high refractive index film material Nb on the other side of the substrate material dried in S1 by electron beam evaporation 2 O 5 And low refractive index film material YF 3 The deposition temperature is 120°C, and the high refractive index film material is Nb 2 O 5 The deposition rate is 2.0 nm / min, Nb 2 O 5 The deposition thickness is 318nm, and the low refractive index film material is YF 3 The deposition rate is 3.2nm / min, YF 3 The deposition thickness is 535nm and the background vacuum is 6.0×10 -4 Pa, and a broadband antireflection film is obtained.

[0036] The high refractive index film material Nb deposited in S3 2 O 5 And low refractive index film material YF 3 The total thickness error of the first end surface film layer is 2.1%.

[0037] The actual average transmittance of the broadband anti-reflection film and the blank substrate material before anti-reflection in the 2.0~5.0μm band is measured by a spectrophotometer or a wide-spectrum laser, and the actual values ​​are 92% and 53% respectively.

[0038] Therefore, the present invention adopts a mid-infrared broadband anti-reflection film of the above structure and its preparation method and application. Only by matching the high refractive index film layer material and the low refractive index film layer material, a mid-infrared broadband anti-reflection film with a simple film structure and high transmittance can be designed. The theoretical value of the transmittance in the 2.0~5.0μm band is 97.7%, and the actual value is greater than 92%.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A mid-infrared broadband antireflection film, characterized in that: The structure of broadband antireflection film is AIR|( a L b H) c |SUB|( b H a L) c |AIR, Among them, SUB represents the substrate, AIR represents the incident medium and the output medium, H represents the high refractive index film layer, the high refractive index value is 2~3.5, L represents the low refractive index film layer, the low refractive index value is 1~1.8, b and a Respectively represent the λ / 4 optical thickness of the high and low refractive index film layers, c is the number of cycles, 1≤ c ≤3.

2. A mid-infrared broadband antireflection film according to claim 1, characterized in that: The substrate material includes, but is not limited to, one or more of double polished single crystal silicon, sapphire, and zinc sulfide crystal.

3. A mid-infrared broadband antireflection film according to claim 1, characterized in that: The high refractive index film layer material includes one or more of ZnS, TiO2, HfO2, ZrO2, Nb2O5 and ZnSe.

4. The mid-infrared broadband antireflection film according to claim 1, characterized in that: The low refractive index film layer material includes one or more of SiO2, Al2O3, MgF2, BaF2, YF3 and ThF4.

5. A method for preparing a mid-infrared broadband antireflection film according to any one of claims 1 to 4, characterized in that: The following steps are included: S1, using a strong oxidizing inorganic solvent and an organic solvent to clean the substrate material in sequence, and drying the cleaned substrate material; S2, depositing a high refractive index film layer material and a low refractive index film layer material in sequence on one side of the substrate material dried in S1 to obtain a first end surface film layer; S3, depositing a high refractive index film layer material and a low refractive index film layer material in sequence on the other side of the substrate material dried in S1 to obtain a broadband anti-reflection film.

6. The method for preparing a mid-infrared broadband antireflection film according to claim 5, characterized in that: In S1, drying is performed in an oven or a hot plate, the drying temperature is 100-200°C, and the drying time is 30-60 minutes.

7. The method for preparing a mid-infrared broadband antireflection film according to claim 5, characterized in that: In S1, the inorganic solvent includes one or more of ammonia water, concentrated sulfuric acid and hydrogen peroxide, and the organic solvent includes alcohol.

8. The method for preparing a mid-infrared broadband antireflection film according to claim 5, characterized in that: In S2 and S3, the deposition includes one of electron beam evaporation, magnetron sputtering and ion beam sputtering.

9. The method for preparing a mid-infrared broadband antireflection film according to claim 5, characterized in that: In S2 and S3, the deposition temperature is 20~400°C, the deposition rate is 0.5~10nm / min, and the deposition thickness is 10~600nm.

10. Use of a mid-infrared broadband antireflection film according to any one of claims 1 to 4, characterized in that: Used to improve the sensitivity of infrared detection systems and the emission efficiency of optical parametric oscillator lasers.

Images