A method for preparing a high-performance middle-wave infrared optical thin film element

Abstract

The application discloses a high-performance middle-wave infrared optical thin film element preparation method and relates to the technical field of optical thin films. The method comprises the following steps: selecting an ion beam sputtering Si thin film as a high-refractive-index thin film material and selecting an ion beam sputtering SiO2 thin film as a low-refractive-index thin film material; obtaining optical constants of the ion beam sputtering Si thin film and the ion beam sputtering SiO2 thin film and a basic film system structure of a middle-wave infrared antireflection thin film; according to technical index requirements, optimizing the basic film system structure of the middle-wave infrared antireflection thin film to obtain the middle-wave infrared antireflection thin film; selecting Si material as a base material; coating the middle-wave infrared antireflection thin film on both sides of the base material to obtain a middle-wave infrared optical thin film element with super-low residual reflection and super-low surface shape error. The method realizes the manufacture of a middle-wave infrared optical thin film element with a large aperture, super-low residual reflection, super-low surface shape error and good environmental adaptability.

Description

Technical Field

[0001] This invention generally relates to the field of optical thin film technology, and specifically to a method for preparing a high-performance mid-wave infrared optical thin film element. Background Technology

[0002] Infrared photoelectric detection and imaging technology, a passive photoelectric detection and imaging system technology based on target infrared radiation, has become an important technology in modern basic and applied sciences. Due to its unique advantages such as good adaptability, stealth, resistance to interference, and strong operational capabilities at night or in harsh weather conditions, infrared detection technology is now widely used in the aerospace field. With the development of modern warfare towards informatization, networking, and aerospace applications, the operating environment of infrared photoelectric detection and imaging devices for high-speed aircraft such as fighter jets and missiles is becoming increasingly harsh, placing high demands on the transmittance and environmental adaptability of optical systems. Therefore, it is necessary to invent new materials and processes to achieve the fabrication of high-performance mid-wave infrared optical thin-film elements, and to solve the problems of ultra-low residual reflection, ultra-low surface error, and environmental adaptability of mid-wave infrared optical thin-film elements.

[0003] Currently, the commonly used thin film materials for mid-wave infrared antireflection thin film elements are mainly Ge, ZnS, Al2O3, MgF2, and YF3. Common preparation methods include electron beam evaporation, electron beam evaporation combined with ion beam assisted deposition, chemical vapor deposition, and magnetron sputtering. Pan Yongqiang et al. designed film systems using Ge, ZnSe, and YF3 as materials with high, medium, and low refractive indices, and used ion beam assisted deposition to prepare antireflection films, ultimately obtaining infrared antireflection films compatible with both 3–5 μm and 8–12 μm wavelengths. Transmittance tests showed a maximum transmittance of 98%, with an average transmittance exceeding 94%. Wang Tongtong et al. used ZnS as a substrate and TiO2 and Al2O3 as coating materials, preparing oxide-based infrared antireflection films using ion-assisted evaporation. After double-sided deposition of films in the 3.7–4.8 μm wavelength band, the average transmittance reached over 96%.

[0004] In summary, the performance of mid-wave infrared antireflection films prepared based on conventional infrared thin-film materials is not yet optimal. Therefore, we propose a method for fabricating high-performance mid-wave infrared optical thin-film elements to address these issues. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a method for fabricating high-performance mid-wave infrared optical thin film elements with large aperture, ultra-low residual reflection, and ultra-low surface error that can be applied to complex operating environments.

[0006] This invention provides a method for fabricating a high-performance mid-wave infrared optical thin-film element, comprising the following steps:

[0007] Ion beam sputtered Si thin film was selected as a high refractive index thin film material, and ion beam sputtered SiO2 thin film was selected as a low refractive index thin film material.

[0008] The optical constants of the ion-beam sputtered Si thin film and the ion-beam sputtered SiO2 thin film, as well as the basic film structure of the mid-wave infrared antireflection thin film, are obtained.

[0009] According to the technical specifications, the basic film structure of the mid-wave infrared anti-reflection film is optimized to obtain the mid-wave infrared anti-reflection film.

[0010] Si material was chosen as the substrate material;

[0011] Mid-wave infrared anti-reflection films are deposited on both sides of the substrate material to obtain a mid-wave infrared optical thin film element with ultra-low residual reflection and ultra-low surface shape error.

[0012] According to the technical solution provided by the present invention, after obtaining a mid-wave infrared optical thin-film element with ultra-low residual reflection and ultra-low surface shape error, the method further includes the following steps:

[0013] The performance of the mid-wave infrared optical thin-film element is tested in a test environment, including but not limited to: high / low temperature environment, humid heat environment, mold environment, and salt spray environment.

[0014] According to the technical solution provided by the present invention, the basic film structure of the mid-wave infrared antireflection film is optimized according to the technical specifications to obtain the mid-wave infrared antireflection film, specifically including the following steps:

[0015] The optical constants are input into the thin film design software, and the coefficients of the basic film system structure of the mid-wave infrared antireflection film are optimized based on the numerical optimization algorithm to obtain the mid-wave infrared antireflection film.

[0016] According to the technical solution provided by the present invention, the mid-wave infrared antireflection thin film is deposited on both sides of the substrate material to obtain a mid-wave infrared optical thin film element with ultra-low residual reflection and ultra-low surface shape error, specifically including the following steps:

[0017] By employing dual-ion-beam sputtering deposition technology, mid-wave infrared antireflection films are deposited on both sides of the substrate material to obtain a mid-wave infrared optical thin-film element with ultra-low residual reflection and ultra-low surface shape error.

[0018] According to the technical solution provided by the present invention, the ion beam sputtered Si thin film and the ion beam sputtered SiO2 thin film are obtained by the following method:

[0019] When the oxygen flow rate is at a first preset value, the ion beam sputtered Si thin film is prepared using dual ion beam sputtering deposition technology;

[0020] When the oxygen flow rate is at the second preset value, ion beam sputtering SiO2 thin film is prepared by dual ion beam sputtering deposition technology;

[0021] Wherein, the first preset value is less than the second preset value.

[0022] According to the technical solution provided by the present invention, the average residual reflectance of the mid-wave infrared antireflection film deposited on both sides of the substrate material is 0.08%.

[0023] According to the technical solution provided by the present invention, the ultra-low surface shape errors on both sides of the mid-wave infrared optical thin film element are 0.014λ and 0.011λ, respectively.

[0024] Wherein, λ = 632.8 nm.

[0025] According to the technical solution provided by the present invention, the aperture range of the mid-wave infrared optical thin film element is Φ50mm-Φ300mm.

[0026] In summary, this invention provides a specific process for fabricating a high-performance mid-wave infrared optical thin-film element. This invention selects ion-beam sputtered Si thin film as a high-refractive-index thin-film material and ion-beam sputtered SiO2 thin film as a low-refractive-index thin-film material; obtains the optical constants of the ion-beam sputtered Si thin film and the ion-beam sputtered SiO2 thin film, as well as the basic film structure of the mid-wave infrared anti-reflection thin film; optimizes the basic film structure of the mid-wave infrared anti-reflection thin film according to technical requirements to obtain the mid-wave infrared anti-reflection thin film; selects Si material as the substrate material; and deposits mid-wave infrared anti-reflection thin films on both sides of the substrate material to obtain a mid-wave infrared optical thin-film element with ultra-low residual reflection and ultra-low surface shape error.

[0027] This invention enables the fabrication of large-aperture, ultra-low residual reflection, and ultra-low surface error mid-wave infrared optical thin-film elements that can be applied under complex operating environments by depositing mid-wave infrared anti-reflection thin films on both sides of a substrate material in a single process. Attached Figure Description

[0028] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0029] Figure 1 This is a schematic diagram of a process for fabricating a high-performance mid-wave infrared optical thin-film element.

[0030] Figure 2 This is a schematic diagram of the operation of dual-ion beam sputtering deposition of thin films.

[0031] Figure 3The curves show the refractive index and extinction coefficient of Si thin films sputtered by ion beam.

[0032] Figure 4 The curves show the refractive index and extinction coefficient of SiO2 thin films sputtered by ion beam.

[0033] Figure 5 This is a schematic diagram of a mid-wave infrared optical thin-film element with ultra-low residual reflection.

[0034] Figure 6 Design double-sided transmittance and single-sided reflectance curves for mid-wave infrared optical thin-film elements.

[0035] Figure 7 Double-sided transmittance and reflectance curves for mid-wave infrared optical thin film elements prepared by ion beam sputtering. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] Please refer to Figure 1 The diagram shown illustrates a detailed process for fabricating a high-performance mid-wave infrared optical thin-film element according to the present invention, including the following steps:

[0039] S10. Ion beam sputtered Si thin film is selected as a high refractive index thin film material, and ion beam sputtered SiO2 thin film is selected as a low refractive index thin film material.

[0040] The following methods were used to obtain ion-beam sputtered Si thin films and ion-beam sputtered SiO2 thin films:

[0041] When the oxygen flow rate is at the first preset value, ion beam sputtering Si thin films are prepared using dual ion beam sputtering deposition technology;

[0042] When the oxygen flow rate is at the second preset value, ion beam sputtering SiO2 thin film is prepared by dual ion beam sputtering deposition technology;

[0043] The first preset value is less than the second preset value. Here, the first preset value is, for example, 0 sccm, and the second preset value is, for example, 60 sccm.

[0044] S20. Obtain the optical constants of the ion beam sputtered Si thin film and the ion beam sputtered SiO2 thin film, as well as the basic film system structure of the mid-wave infrared antireflection thin film.

[0045] The basic film structure of the mid-wave infrared antireflection film is Sub / LHL / Air, and its reference wavelength range is 2000nm~5000nm.

[0046] S30. Optimize the basic film structure of the mid-wave infrared antireflection film according to the technical specifications to obtain the mid-wave infrared antireflection film.

[0047] Specifically, based on the technical specifications, the basic film structure of the mid-wave infrared antireflection film is optimized to obtain the mid-wave infrared antireflection film, which includes the following steps:

[0048] Optical constants are input into thin film design software, and the coefficients of the basic film system structure of the mid-wave infrared antireflection film are optimized based on numerical optimization algorithms to obtain the mid-wave infrared antireflection film.

[0049] The optimized mid-wave infrared antireflection film structure is Sub / aL bH cL / Air, where H is a high-refractive-index thin film material, i.e., ion-sputtered Si thin film; L is a low-refractive-index thin film material, i.e., ion-sputtered SiO2 thin film; and a, b, and c are film layer matching coefficients, where 0 < a < b < c. <a、b、c<4。

[0050] S40. Select Si material as the substrate material;

[0051] The substrate material was selected based on the requirement for high-performance mid-wave infrared optical thin films.

[0052] Using ion-beam sputtered Si thin films as high-refractive-index thin film materials and ion-beam sputtered SiO2 thin films as low-refractive-index thin film materials can significantly increase the bonding force between film layers and between film layers and substrates in mid-wave infrared antireflection films, and greatly reduce the impact of the interface layer characteristics of Si and SiO2 films on the performance of the mid-wave infrared antireflection films themselves. Furthermore, by employing dual-ion-beam sputtering deposition technology, mid-wave antireflection films (SiO2-Si-SiO2) can be fabricated in a single step by changing only the oxygen flow rate parameter. This improves the interfacial properties of multilayer films, enhances the performance of multilayer films, and enables the fabrication of thin film elements with any aperture range of Φ50mm-Φ300mm.

[0053] S50. The mid-wave infrared anti-reflection film is deposited on both sides of the substrate material to obtain a mid-wave infrared optical thin film element with ultra-low residual reflection and ultra-low surface shape error.

[0054] The process involves depositing mid-wave infrared antireflection films on both sides of a substrate material to obtain a mid-wave infrared optical thin-film element with ultra-low residual reflection and ultra-low surface shape error. This process specifically includes the following steps:

[0055] Mid-wave infrared antireflection films were deposited on both sides of the substrate material using dual-ion beam sputtering deposition technology, resulting in mid-wave infrared optical thin film elements with ultra-low residual reflection and ultra-low surface shape error.

[0056] This invention utilizes ion beam sputtering deposition technology to design and deposit mid-wave infrared antireflection films on both sides of a substrate material, achieving the fabrication of mid-wave infrared optical thin-film elements with ultra-low residual reflection, high transmittance, and suitability for complex operating conditions. This method significantly improves the performance of mid-wave infrared optical thin-film elements and is of great importance for their application under complex operating conditions. Furthermore, this method is universally applicable to the fabrication of ultra-low residual reflection and ultra-low surface error optical thin-film elements with different operating wavelengths, apertures, and substrates.

[0057] Furthermore, after obtaining a mid-wave infrared optical thin-film element with ultra-low residual reflection and ultra-low surface shape error, the following steps are also included:

[0058] The performance of mid-wave infrared optical thin-film components was tested in various environments, including but not limited to high / low temperature environments, humid and hot environments, moldy environments, and salt spray environments. The tests demonstrated that the mid-wave infrared optical thin-film components are suitable for a wide range of environments and possess high versatility.

[0059] Furthermore, the average residual reflectance of the mid-wave infrared antireflection films deposited on both sides of the substrate material is 0.08%.

[0060] Furthermore, the ultra-low surface shape errors on both sides of the mid-wave infrared optical thin film element are 0.014λ and 0.011λ, respectively; where λ = 632.8 nm. Here, a laser interferometer can be used to test the surface shape of the prepared mid-wave infrared antireflection thin film element to obtain the surface shape errors rms = 0.014λ and 0.011λ (λ = 632.8 nm) on both sides within a Φ100 mm aperture.

[0061] Furthermore, the aperture range of the mid-wave infrared optical thin film element is Φ50mm-Φ300mm.

[0062] Taking the fabrication of a large-aperture, ultra-low residual reflection, and ultra-low surface shape error mid-wave infrared (3700nm-4800nm) optical thin-film element as an example, the specific steps are as follows:

[0063] First, Si material was selected as the substrate material, with dimensions of Φ200mm × 8mm. Based on the high density and good environmental adaptability of thin films prepared by dual-ion beam sputtering technology, silicon-based thin films were chosen as the material for mid-wave antireflection multilayer films. This effectively improves the interface characteristics of high and low refractive index films. A schematic diagram of dual-ion beam sputtering deposition is shown below. Figure 2 As shown.

[0064] Secondly, ion-beam sputtered Si thin films were selected as the high-refractive-index thin film material, and ion-beam sputtered SiO2 thin films as the low-refractive-index thin film material. The refractive index and extinction coefficient curves of ion-beam sputtered Si thin films and ion-beam sputtered SiO2 thin films in the near-infrared to mid-infrared band are shown below. Figure 3 and Figure 4 As shown, the refractive indices at a wavelength of 4000 nm are 3.712 and 1.4129, respectively, and the extinction coefficients are 0.0009 and 0.001, respectively.

[0065] Then, mid-wave infrared anti-reflection films are designed on both sides of the Si substrate, as shown in the schematic diagram below. Figure 5 As shown, the spacer layers between the Si thin film and the Si O2 thin film, and between the Si substrate and the Si O2 thin film, are extremely thin SiO2 layers. x Thin film (this layer can be ignored in the film system design). The basic film system structure of the mid-wave infrared antireflection film, Sub / LHL / Air, is given. The reference wavelength is 4000nm. Based on the numerical optimization algorithm, the film system structure coefficients are optimized to obtain the optimal ultra-low residual reflection mid-wave infrared optical film system structure as Sub / 0.22L 0.38H 1.16L / Air.

[0066] The transmittance and reflectance curves of the designed mid-wave infrared antireflection film are as follows: Figure 6 As shown, the average transmittance on both sides in the 3700-4800nm ​​band is 99.22% and the average reflectance on one side is 0.02%.

[0067] Then, using dual-ion beam sputtering deposition technology, the oxygen flow rate was 60 sccm when preparing SiO2 thin films and 0 sccm when preparing Si thin films. By changing only this one parameter, the deposition of SiO2-Si-SiO2 multilayer films on Si substrates can be achieved.

[0068] Finally, mid-wave infrared antireflection films are deposited on both sides of the Si substrate to obtain a mid-wave infrared optical thin-film element with ultra-low residual reflection and ultra-low surface shape error. The double-sided transmittance and double-sided reflectance curves of the prepared mid-wave infrared optical thin-film element can be tested using an infrared Fourier spectrometer, and the double-sided transmittance and reflectance curves are shown below. Figure 7As shown, the average transmittance on both sides in the 3700-4800nm ​​band is 99.26% and the average reflectance on both sides is 0.08%, which is the best level to date.

[0069] Furthermore, the aforementioned mid-wave infrared optical thin-film element can pass environmental tests such as high and low temperatures, humidity and heat, mold, and salt spray.

[0070] The above description is merely a preferred embodiment of the present invention and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention is not limited to the specific combination of the above-described technical features, but also includes other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this invention.

Claims

1. A method for fabricating a high-performance mid-wave infrared optical thin-film element, characterized in that, Includes the following steps: Ion beam sputtered Si thin film was selected as a high refractive index thin film material, and ion beam sputtered SiO2 thin film was selected as a low refractive index thin film material. The optical constants of the ion-beam sputtered Si thin film and the ion-beam sputtered SiO2 thin film, as well as the basic film structure of the mid-wave infrared antireflection thin film, are obtained. The basic film structure of the mid-wave infrared antireflection film is Sub / aLbHcL / Air; The values ​​are a=0.22, b=0.38, and c=1.

16. According to the technical specifications, the basic film structure of the mid-wave infrared anti-reflection film is optimized to obtain the mid-wave infrared anti-reflection film. Si material was chosen as the substrate material; The mid-wave infrared antireflection film is deposited on both sides of the substrate material to obtain a mid-wave infrared optical thin film element with large aperture, ultra-low residual reflection, and ultra-low surface shape error. The aperture range of the mid-wave infrared optical thin film element is Φ50mm-Φ300mm.

2. The method for fabricating a high-performance mid-wave infrared optical thin-film element according to claim 1, characterized in that, According to the technical specifications, the basic film structure of the mid-wave infrared antireflection film is optimized to obtain the mid-wave infrared antireflection film, specifically including the following steps: The optical constants are input into the thin film design software, and the coefficients of the basic film system structure of the mid-wave infrared antireflection film are optimized based on the numerical optimization algorithm to obtain the mid-wave infrared antireflection film.

3. The method for fabricating a high-performance mid-wave infrared optical thin-film element according to claim 1, characterized in that, The mid-wave infrared antireflection film is deposited on both sides of the substrate material to obtain a mid-wave infrared optical thin film element with ultra-low residual reflection and ultra-low surface shape error. The specific steps include: By employing dual-ion-beam sputtering deposition technology, mid-wave infrared antireflection films are deposited on both sides of the substrate material to obtain a mid-wave infrared optical thin-film element with ultra-low residual reflection and ultra-low surface shape error.

4. The method for fabricating a high-performance mid-wave infrared optical thin-film element according to claim 1, characterized in that, The ion-beam sputtered Si thin film and the ion-beam sputtered SiO2 thin film were obtained according to the following methods: When the oxygen flow rate is at a first preset value, the ion beam sputtered Si thin film is prepared using dual ion beam sputtering deposition technology; When the oxygen flow rate is at the second preset value, ion beam sputtering SiO2 thin film is prepared by dual ion beam sputtering deposition technology; Wherein, the first preset value is less than the second preset value.

5. The method for fabricating a high-performance mid-wave infrared optical thin-film element according to claim 1, characterized in that, The average residual reflectance of the mid-wave infrared antireflection films deposited on both sides of the substrate material is 0.08%.

6. The method for fabricating a high-performance mid-wave infrared optical thin-film element according to claim 1, characterized in that, The ultra-low surface shape errors on both sides of the mid-wave infrared optical thin film element are 0.014λ and 0.011λ, respectively. Wherein, λ = 632.8 nm.

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