Mid-infrared light amplitude limiting film

Abstract

The invention discloses a mid-infrared light amplitude limiting film which comprises a substrate, at least one combination layer is generated on the substrate, a protection layer is plated on the combination layer on the uppermost layer, and each combination layer comprises a low-refractive-index layer and a phase-change high-refractive-index layer. The mid-infrared light amplitude limiting film can realize high transmittance of an OPEN state and high barrier rate of a CLOSED state within the broadband of 3-5 [mu] m and 8-10 [mu] m, and the light amplitude limiting ratio is high; meanwhile, the low-refractive-index layer and the phase-change high-refractive-index layer are combined, and the protective layer is arranged, so that the phase-change high-refractive-index layer can be effectively protected, deterioration of the phase-change high-refractive-index layer is delayed, and high application value is achieved.

Description

Technical Field

[0001] The present invention relates to optical thin films, and particularly to a mid-infrared optical limiting thin film. Background Art

[0002] With the increasing threat of high-power laser weapons to high-value targets in modern battlefields, especially the rising risk of laser strikes on key window materials, the development of effective protection technologies has become particularly urgent. Mid-infrared lasers have characteristics such as high energy, high focusing, and good penetration. Mid-infrared lasers in the 3-5μm and 8-10μm wavelength bands can pose a great threat to key targets such as electronic devices, optical systems, and communication facilities. Due to the concentration of their energy in specific wavelength bands, mid-infrared lasers can cause severe thermal effects on targets in a short time, resulting in damage or paralysis. The protection technology against mid-infrared laser blinding weapons has become an important direction in military technology research. To address this challenge, the selection and design of materials play a crucial role in the protection system.

[0003] In 1959, Bell Labs first discovered the metal-insulator transition (MIT) phenomenon in vanadium oxides, which laid the foundation for the research of many modern optoelectronic functional materials. Vanadium dioxide (VO2), as a typical MIT material, can reversibly change its optical properties through temperature changes near room temperature. Specifically, VO2 maintains a high transmittance at low temperatures and transforms into a high-blocking state at high temperatures. This type of material with metal-insulator transition characteristics has become a powerful candidate material for combating laser radiation, especially mid-infrared lasers.

[0004] Although there have been certain advancements in the application of related substances in the prior art, there are still some insurmountable defects. For example, the mid-infrared broadband protection materials in the prior art fail to provide stable high transmittance in the open state and high optical limiting ratios, which limits their effectiveness in practical applications. In addition, most substances with metal-insulator transition characteristics have poor stability and durability, and are particularly prone to damage in high-temperature environments, limiting the reliability of their long-term use. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a mid-infrared optical limiting thin film with stable high transmittance in the open state and high optical limiting in the closed state across all wavelength bands.

[0006] Technical Solution: The mid-infrared optical limiting thin film described in the present invention includes a substrate, and at least one composite layer is formed on the substrate, and a protective layer is deposited on the uppermost composite layer, wherein each group of composite layers includes a low-refractive-index layer and a phase-change high-refractive-index layer.

[0007] Preferably, the material of the substrate is any one of CaF2, SiO2, CdTe, Al2O3, ZnSe, HfO2, ZnS, Ge, and the thickness is not less than 1 mm.

[0008] Preferably, the material of the low refractive index layer is any one of HfO2, MgF2, SiO2, CaF2, Al2O3, ZnS, ZnSe, and the thickness is 10 - 2000 nm.

[0009] Preferably, the material of the phase change high refractive index layer is any one of VO2, Ge - Sb - Te, Bi, and the thickness is 10 - 2000 nm.

[0010] Preferably, the combined layer is two groups or more.

[0011] Preferably, the material of the protective layer is any one of HfO2, MgF2, SiO2, CaF2, Al2O3, ZnS, ZnSe, and the thickness is 100 - 1000 nm.

[0012] Advantageous effects: Compared with the prior art, the present invention has the following remarkable advantages: 1. The mid - infrared optical limiting thin film can achieve a transmittance > 80% in the OPEN state, a transmittance < 10% in the CLOSED state, an extinction ratio > 10 dB, and a high optical limiting ratio in the wide wavelength range of 3 - 5 μm and 8 - 10 μm; 2. By combining the low refractive index layer and the phase change high refractive index layer and setting a protective layer, the phase change high refractive index layer can be effectively protected. Description of the Drawings

[0013] Figure 1 It is a schematic structural diagram of a mid - infrared optical limiting thin film, where 1 is the substrate, 2 is the combined layer, 3 is the protective layer, 4 is the phase change high refractive index layer, and 5 is the low refractive index layer;

[0014] Figure 2 It is a simulation result diagram of a single - combined - layer HfO2 - VO2 - HfO2 - CaF2 mid - infrared optical limiting thin film;

[0015] Figure 3 It is a simulation result diagram of a double - combined - layer HfO2 - VO2 - HfO2 - VO2 - HfO2 - CaF2 mid - infrared optical limiting thin film;

[0016] Figure 4 It is a simulation result diagram of a triple - combined - layer HfO2 - VO2 - HfO2 - VO2 - HfO2 - VO2 - HfO2 - CaF2 mid - infrared optical limiting thin film;

[0017] Figure 5 It is a simulation result diagram of an HfO2 - VO2 - CaF2 thin film;

[0018] Figure 6 It is the simulation result diagram of the HfO2-VO2-SiO2 thin film;

[0019] Figure 7 It is the parameter curve diagram of the refractive index n and extinction ratio k of VO2 at 300K;

[0020] Figure 8 It is the parameter curve diagram of the refractive index n and extinction ratio k of VO2 at 355K;

[0021] Figure 9 It is the parameter curve diagram of the refractive index n and extinction ratio k of HfO2;

[0022] Figure 10 It is the parameter curve diagram of the refractive index n and extinction ratio k of CaF2;

[0023] Figure 11 It is the parameter curve diagram of the refractive index n and extinction ratio k of SiO2. Specific implementation manners

[0024] The technical solution of the present invention will be further described below.

[0025] Example 1: Design and simulation of a mid-infrared optical limiting thin film of a single composite layer of HfO2-VO2-HfO2-CaF2

[0026] 1. Design a single composite layer mid-infrared optical limiting thin film: The substrate material is CaF2 with a thickness of 8mm; in the composite layer, the low refractive index layer material is HfO2 with a thickness of 1500nm, the phase change high refractive index layer material is VO2 with a thickness of 60nm; the protective layer material is HfO2 with a thickness of 660nm;

[0027] 2. Establish an FDTD simulation model, and the refractive index n and extinction ratio k parameter curves of VO2, HfO2, and CaF2 are as Figures 7-10 shown, and perform the simulation.

[0028] The simulation results are as Figure 2 shown. The OPEN state transmittance of the single composite layer mid-infrared optical limiting thin film is 78%-97% in the wide wavelength bands of 3-5μm and 8-10μm. Generally speaking, due to the small number of composite layers, it cannot meet the requirement of high transmittance in the wide wavelength band, and the transmittance still does not meet the standard; at the same time, to ensure the high transmittance in the OPEN state, the phase change high refractive index layer in the composite layer is relatively thin, and the CLOSED state transmittance is greater than 9%.

[0029] Example 2: Design and simulation of a mid-infrared optical limiting thin film of a double composite layer of HfO2-VO2-HfO2-VO2-HfO2-CaF2

[0030] 1. Design a dual-composite-layer mid-infrared optical limiting thin film: The substrate material is CaF2 with a thickness of 8 mm. In the first composite layer from the substrate upwards, the low refractive index layer material is HfO2 with a thickness of 560 nm, and the phase-change high refractive index layer material is VO2 with a thickness of 90 nm. In the second composite layer, the low refractive index layer material is HfO2 with a thickness of 1150 nm, and the phase-change high refractive index layer material is VO2 with a thickness of 90 nm. The protective layer material is HfO2 with a thickness of 560 nm. The structure is as Figure 1 shown

[0031] 2. Establish an FDTD simulation model. The refractive index n and extinction ratio k parameter curves of VO2, HfO2, and CaF2 are as Figures 7-10 shown, and perform the simulation.

[0032] The simulation results are as Figure 3 shown. In the 3 - 5 μm and 8 - 10 μm wide wavelength bands, the transmittance in the OPEN state is > 80%, the transmittance in the CLOSED state is < 10%, and the extinction ratio is > 10 dB.

[0033] Example 3: Design and Simulation of a Triple-Composite-Layer HfO2-VO2-HfO2-VO2-HfO2-VO2-HfO2-CaF2 Mid-Infrared Optical Limiting Thin Film

[0034] 1. Design a triple-composite-layer mid-infrared optical limiting thin film: The substrate material is CaF2 with a thickness of 8 mm. In the first composite layer from the substrate upwards, the low refractive index layer material is HfO2 with a thickness of 490 nm, and the phase-change high refractive index layer material is VO2 with a thickness of 60 nm. In the second composite layer, the low refractive index layer material is HfO2 with a thickness of 80 nm, and the phase-change high refractive index layer material is VO2 with a thickness of 60 nm. In the third composite layer, the low refractive index layer material is HfO2 with a thickness of 1100 nm, and the phase-change high refractive index layer material is VO2 with a thickness of 60 nm. The protective layer material is HfO2 with a thickness of 550 nm;

[0035] 2. Establish an FDTD simulation model. The refractive index n and extinction ratio k parameter curves of VO2, HfO2, and CaF2 are as Figures 7-10 shown, and perform the simulation.

[0036] The simulation results are as Figure 4 shown. In the 3 - 5 μm and 8 - 10 μm wide wavelength bands, the transmittance in the OPEN state is > 80%, the transmittance in the CLOSED state is < 10%, and the extinction ratio is > 10 dB. Due to the increase in the number of composite layers, the adaptability to the wide wavelength band is enhanced, and the total thickness of the phase-change high refractive index layer increases, resulting in a further decrease in the transmittance in the CLOSED state. However, due to design and material limitations, the overall performance improvement is limited.

[0037] Comparative Example 1: Design and Simulation of HfO2-VO2-CaF2 Thin Film

[0038] 1. Design of HfO2-VO2-CaF2 thin film: The substrate material is CaF2 with a thickness of 8 mm; on the substrate is a phase-change high refractive index layer made of VO2 with a thickness of 60 nm; on the phase-change high refractive index layer is a protective layer made of HfO2 with a thickness of 710 nm;

[0039] 2. Establish an FDTD simulation model. The refractive index n and extinction ratio k parameter curves of VO2, HfO2, and CaF2 are as Figures 7-10 shown, and perform the simulation.

[0040] The simulation results are as Figure 5 shown. The protective layer also serves as a low refractive index layer, and the anti-reflection effect is limited. As a result, the transmittance in the OPEN state - is 75%-88% in the wide wavelength bands of 3-5 μm and 8-10 μm, which cannot meet the requirement of high transmittance in the overall wide wavelength band; at the same time, to ensure high transmittance in the OPEN state, the phase-change high refractive index layer is relatively thin, and the transmittance in the CLOSED state - is greater than 15%.

[0041] Comparative Example 2: Design and Simulation of HfO2-VO2-SiO2 Thin Film

[0042] 1. Design of HfO2-VO2-SiO2 thin film: The substrate material is SiO2 with a thickness of 8 mm; on the substrate is a phase-change high refractive index layer made of VO2 with a thickness of 80 nm; on the phase-change high refractive index layer is a protective layer made of HfO2 with a thickness of 100 nm;

[0043] 2. Establish an FDTD simulation model. The refractive index n and extinction ratio k parameter curves of VO2, HfO2, and SiO2 are as Figures 7-9 shown in Figure 11, and perform the simulation.

[0044] The simulation results are as Figure 6 shown. Due to the small number of combined layers and the high infrared absorption rate of SiO2, the lowest transmittance in the OPEN state of the infrared light limiting thin film in a single combined layer is 65%, and the transmittance does not meet the standard; at the same time, to ensure high transmittance in the OPEN state, the phase-change high refractive index layer in the combined layer is relatively thin, and the transmittance in the CLOSED state is greater than 9%.

[0045] Combined with the results of Examples 1-3, increasing the number of high-low refractive index combination layers can improve the overall transmittance of the OPEN state in a wide wavelength band, while reducing the transmittance of the CLOSED state. However, there is an upper limit to the benefit. In the 3-5μm and 8-10μm wide wavelength bands, the double-combination layer HfO2-VO2-HfO2-VO2-HfO2-CaF2 can achieve a transmittance of >80% in the OPEN state, a transmittance of <10% in the CLOSED state, and an extinction ratio of >10dB; the performance improvement of the triple-combination layer HfO2-VO2-HfO2-VO2-HfO2-VO2-HfO2-CaF2 compared to the double-combination layer is not obvious, and it increases the manufacturing difficulty. Therefore, considering comprehensively, the double-combination layer HfO2-VO2-HfO2-VO2-HfO2-CaF2 is selected.

[0046] From the analysis of Comparative Example 1, the anti-reflection performance of the single-layer HfO2 is limited, and the transmittance in the OPEN state is lower than that of the multi-layer film; from the analysis of Comparative Example 2, since the infrared absorption of SiO2 is higher than that of CaF2, the transmittance of the HfO2-VO2-SiO2 film in the OPEN state is lower than that of the HfO2-VO2-CaF2 film. Therefore, CaF2 is preferably used as the substrate material.

Claims

1. A mid-infrared light limiting film, characterized in that: The invention comprises a substrate, on which at least one combination layer is generated, and a protective layer is plated on the uppermost combination layer, wherein each group of combination layers comprises a low refractive index layer and a phase-change high refractive index layer.

2. The mid-infrared light limiting film according to claim 1, characterized in that: The material of the substrate is any one of CaF2, SiO2, CdTe, Al2O3, ZnSe, HfO2, ZnS, and Ge.

3. The mid-infrared light limiting film according to claim 1, characterized in that: The thickness of the substrate is not less than 1 mm.

4. The mid-infrared light limiting film according to claim 1, characterized in that: The material of the low refractive index layer is any one of HfO2, MgF2, SiO2, CaF2, Al2O3, ZnS, and ZnSe.

5. The mid-infrared light limiting film according to claim 1, characterized in that: The thickness of the low refractive index layer is 10-2000nm.

6. The mid-infrared light limiting film according to claim 1, characterized in that: The material of the phase-change high-refractive-index layer is any one of VO2, Ge-Sb-Te and Bi.

7. The mid-infrared light limiting film according to claim 1, characterized in that: The thickness of the phase-change high-refractive-index layer is 10-2000 nm.

8. The mid-infrared light limiting film according to claim 1, characterized in that: The combination layers are two or more groups.

9. The mid-infrared light limiting film according to claim 1, characterized in that: The material of the protective layer is any one of HfO2, MgF2, SiO2, CaF2, Al2O3, ZnS, and ZnSe.

10. The mid-infrared light limiting film according to claim 1, characterized in that: The thickness of the protective layer is 100-1000 nm.

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