Three-band middle-long wave infrared filter and preparation method thereof

Abstract

The present application relates to a kind of three-waveband middle-long wave infrared filter and preparation method, including front film system, substrate and back film system, the substrate is located between the front film system and back film system;The front film system is composed of germanium layer and zinc selenide film layer alternately superimposed;The back film system is composed of germanium layer and zinc selenide film layer alternately superimposed.The present application realizes the light energy promotion of 3780-4000nm, 4500-4900nm, 7850-9500nm middle-long wave three wavebands, and very good inhibits the light flux of other wavebands, solves the technical problem of infrared filter window in some special infrared spectrum detection system, provides new scheme for the application of infrared spectrum detection system.

Description

Technical Field

[0001] This invention belongs to the field of optical filter technology, and specifically relates to a three-band mid-to-long-wave infrared filter and its preparation method. Background Technology

[0002] A three-band mid-to-long-wave infrared filter is a filter that selectively transmits highly in three specific wavelength bands while highly blocking other wavelength bands outside of its high-transmittance bands. It is mainly used in infrared spectroscopy detection systems and has very important applications in the defense and military industries. With the development of military infrared technology, the requirements for the optical performance of infrared filters are becoming increasingly stringent, demanding higher capabilities in effectively filtering out background stray signals and improving the signal-to-noise ratio of the detection system. In addition to the high requirements for the optical properties of the filter, the reliability of the infrared filter film is also extremely important. Currently, there are very few types of infrared filters available, therefore, there is a need to develop a new three-band mid-to-long-wave infrared filter. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a three-band mid-to-long-wave infrared filter and its preparation method, which solves the technical problem of infrared filter window in special infrared spectral detection system and provides a new solution for the application of infrared spectral detection system.

[0004] The present invention provides a three-band mid-to-long-wave infrared filter, comprising a front film system, a substrate, and a back film system, wherein the substrate is located between the front film system and the back film system; the front film system is composed of alternating layers of germanium and zinc selenide; the back film system is composed of alternating layers of germanium and zinc selenide.

[0005] Preferably, the front film system has 1-50 layers; the back film system has 1-70 layers.

[0006] Preferably, the substrate is a germanium substrate with a diameter of 10-20 mm and a thickness of 0.1-0.5 mm.

[0007] The advantage of this invention is that it achieves high-efficiency anti-reflection in specific infrared bands of 3780-4000nm, 4500-4900nm, and 7850-9500nm, while highly cutting off other bands outside the high-reflection bands.

[0008] This invention also provides a method for preparing a three-band mid-to-long-wave infrared filter, comprising the following steps:

[0009] (1) Perform ultrasonic cleaning on the substrate;

[0010] (2) Baking and heating the substrate under vacuum conditions;

[0011] (3) The front side of the substrate is treated with a high-energy ion beam, and then the main peak film structure is deposited on the front side of the substrate. Then, the substrate is annealed and cooled to a specified temperature before being spot-released and then air is introduced.

[0012] (4) Repeat steps (1) to (3) to deposit a sub-peak film structure on the back of the substrate to obtain a three-band mid-to-long-wave infrared filter.

[0013] Preferably, the baking temperature in step (2) is 150-200℃ and the baking time is 120-180min.

[0014] Preferably, the high-energy ion beam process parameters in step (3) are: bombardment time 10-20 min, bombardment parameters are: anode voltage 150-200 V, anode current 2-5 A, cathode current 20-25 A, and cathode voltage 20-23 V.

[0015] Preferably, the process parameters for depositing the main peak film system in step (3) are as follows: the germanium layer is deposited by electron beam evaporation, the zinc selenide film layer is deposited by molybdenum boat thermal evaporation, the evaporation rate of the germanium layer is 6-8 A / S, and the evaporation rate of the zinc selenide film layer is 11-13 A / S.

[0016] Preferably, the annealing temperature in step (3) is 150-200℃, the holding time is 1-2h, and the cooling rate is 0.8-1℃ / min.

[0017] Preferably, the specified temperature in step (3) is 80-90℃.

[0018] Preferably, the process parameters for depositing the sub-peak film system in step (4) are as follows: the germanium layer is deposited by electron beam evaporation, the zinc selenide film layer is deposited by molybdenum boat thermal evaporation, the evaporation rate of the germanium layer is 6-8 A / S, and the evaporation rate of the zinc selenide film layer is 11-13 A / S.

[0019] The filter of the present invention can create a more coordinated interference effect by using ZnSe / Ge on both sides. The front film system controls the main transmission peak, while the back film system uses the transmission characteristics of ZnSe in the long-wavelength region to form a secondary peak. At the same time, its refractive index gradient matches the front film system, jointly shaping the high-pass characteristics of three bands.

[0020] Beneficial effects

[0021] This invention achieves an increase in light energy in three mid-to-long wavelength bands: 3780-4000nm, 4500-4900nm, and 7850-9500nm, while effectively suppressing light flux in other bands. It also solves the technical problem of infrared filter windows in special infrared spectral detection systems, providing a new solution for the application of infrared spectral detection systems. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the three-band mid-long-wave infrared filter of the present invention; wherein, 1-front film system; 2-substrate; 3-back film system.

[0023] Figure 2 The main peak (front) transmittance curve of the three-band mid-to-long-wave infrared filter prepared in Example 1 is shown.

[0024] Figure 3 The transmittance curve of the secondary peak (back side) film system of the three-band mid-to-long-wave infrared filter prepared in Example 1 is shown.

[0025] Figure 4 The transmittance curve of the three-band mid-to-long-wave infrared filter prepared in Example 1 is shown.

[0026] Figure 5 This is a schematic diagram of the process for preparing the three-band mid-to-long-wave infrared filter of the present invention. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0028] Example 1

[0029] In this embodiment, an electron beam deposition system with a 6-cavity crucible and a 4-position resistive evaporation coating machine are used to prepare the optical film. The germanium layer is deposited by electron beam evaporation, and the zinc selenide film layer is deposited by molybdenum boat thermal evaporation. The evaporation rate of the germanium layer is 6-8 A / s, and the evaporation rate of the zinc selenide film layer is 11-13 A / s. The evaporation source power is adjusted in real time via feedback from a quartz crystal oscillator (PID control) to maintain the set evaporation rate, and evaporation automatically stops after the target thickness is reached.

[0030] like Figure 1 As shown, this embodiment provides a three-band mid-to-long-wave infrared filter, including a front film system, a substrate, and a back film system, with the substrate located between the front and back film systems. The front film system is composed of alternating germanium layers and zinc selenide layers; the back film system is also composed of alternating germanium layers and zinc selenide layers. Preferably, in this embodiment, the front film system has 48 layers, and the back film system has 60 layers. The substrate is a germanium substrate with a diameter of 18 mm and a thickness of 0.3 mm.

[0031] like Figure 5As shown, this embodiment also provides a method for preparing a three-band mid-to-long-wave infrared filter, including the following steps:

[0032] (1) The germanium substrate is cleaned by fully automatic ultrasonic cleaning. After cleaning, the substrate is dehydrated by IPA.

[0033] (2) Place the substrate on the umbrella plate in the vacuum chamber of the coating machine, and perform vacuuming and baking heating. The baking temperature is set to 160°C and the baking time is 150 min.

[0034] (3) The vacuum reaches 1.0 x 10 -3 After Pa, the front side of the substrate was bombarded with high-energy argon ions for 15 minutes. The bombardment parameters were: anode voltage 180V, anode current 4A, and cathode current 21A.

[0035] (4) A main peak film system structure is deposited on the front side of the substrate, the main peak film system structure comprising: Sub / 124.55H135.37L 110.80H 51.58L 472.06H 184.80L 528.06H 190.07L 48.60H ​​313.73L 409.11H296.56L 515.26H 276.95L 1060.41H 47.51L 122.81H 309.76L 364.78H 287.12L528.13H 298.72L 1204.78H 391.43L 214.87H 456.15L 535.25H 281.50L 268.50H 404.79L 54.06H 446.71L 266.91H 411.65L 259.33H 834.96L 234.96H 313.96L 597.17H 408.91L 431.09H 407.98L 319.49H 753.42L 425.70H 256.86L 76.14H 681.60L / Air Where Sub represents the substrate, Air represents air, H represents the physical thickness of the Ge layer, L represents the physical thickness of the ZnSe film layer, and the numbers in the film structure formula represent the physical thickness of the film layer. The design wavelength is 4500nm. The transmittance curve of the main peak (front) film system is shown in the figure. Figure 2 As shown.

[0036] (5) After the main peak film structure is deposited, the infrared filter is annealed at a temperature of 180°C for 1 hour and a cooling rate of 0.8~1°C / min.

[0037] (6) When the temperature drops to 80°C, manually release the air 6 times and then continue to introduce air into the vacuum chamber. The release should be 2 seconds and then 8 seconds.

[0038] (7) Clean the coated product with fully automatic ultrasonic cleaning. After cleaning, use IPA to dehydrate the substrate.

[0039] (8) Place the substrate on the umbrella plate in the vacuum chamber of the coating machine, and perform vacuuming and baking heating. The baking temperature is set to 160°C and the baking time is 150 min.

[0040] (9) Wait until the vacuum reaches 1.0 x 10 -3 After Pa, a back-side sub-peak film structure is deposited on the other side of the substrate, comprising: Sub / 112.00H 118.74L 64.26H 723.46L 48.56H 939.89L 425.08H 820.11L 129.93H 948.90L 313.62H 76.80L 55.22H 699.50L 307.98H 166.71L 74.67H 447.64L 393.79H 648.33L 388.50H 743.22L 347.82H 92.23L 95.22H 262.01L 390.24H 103.42L 102.56H497.45L 62.05H 209.54L 147.92H 189.57L 118.31H 259.38L 151.01H 248.93L129.44H 195.35L 259.45H 248.83L 138.46H 319.97L 233.16H 245.02L 124.37H275.71L 359.39H 226.31L 105.57H 505.05L 48.12H 349.79L 157.12H 91.12L 333.90H144.28L 157.62H 574.59L / Air, where Sub represents the substrate, Air represents air, H represents the physical thickness of the Ge layer, L represents the physical thickness of the ZnSe film layer, and the numbers in the film structure formula represent the physical thickness of the film layer. The design wavelength is 6250nm. The transmittance curve of the secondary peak (back side) film system is shown in the figure. Figure 3 As shown.

[0041] (10) After the main peak film structure is deposited, the infrared filter is annealed at a temperature of 180°C for 1 hour and a cooling rate of 0.8~1°C / min.

[0042] (11) When the temperature drops to 80°C, manually release the air 6 times and then continue to introduce air into the vacuum chamber. The release should be 2 seconds and then 8 seconds.

[0043] The transmittance curves of the three-band mid-to-long-wave infrared filter obtained in this embodiment are shown in the figure below. Figure 4 As shown, it meets the technical requirements of 3780-4000nm, 4500-4900nm, 7850-9500nm, T≥88%, Tavg≥90%; and visible light -3650nm, 4200-4300nm, 5100-7300nm, T≤1%.

[0044] The reliability of the membrane layer was verified by constant temperature and humidity test at 85℃ and 85% relative humidity (referring to JESD22-A101 or related standards), and no membrane layer peeling was found.

[0045] Three tensile tests were conducted on the sample using 3M 600 tape conforming to ASTM D3359 standard. No film peeling was found, indicating that the filter film has reliable adhesion.

[0046] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A three-band mid-to-long-wave infrared filter, characterized in that: The device includes a front-side film system, a substrate, and a back-side film system, with the substrate located between the front-side and back-side film systems. The front-side film system is composed of alternating layers of germanium and zinc selenide. The back-side film system is composed of alternating layers of germanium and zinc selenide. The front-side film system has 48-50 layers, and the back-side film system has 60-70 layers. The substrate is a germanium substrate with a diameter of 10-20 mm and a thickness of 0.1-0.5 mm.

2. A method for preparing a three-band mid-to-long-wave infrared filter as described in claim 1, comprising the following steps: (1) Perform ultrasonic cleaning on the substrate; (2) Baking and heating the substrate under vacuum conditions; (3) The front side of the substrate is treated with a high-energy ion beam, and then the main peak film structure is deposited on the front side of the substrate. Then, the substrate is annealed and cooled to a specified temperature before being spot-released and then air is introduced. (4) Repeat steps (1) to (3) to deposit a sub-peak film structure on the back of the substrate to obtain a three-band mid-to-long-wave infrared filter.

3. The preparation method according to claim 2, characterized in that: The baking temperature in step (2) is 150-200℃ and the baking time is 120-180min.

4. The preparation method according to claim 2, characterized in that: The high-energy ion beam process parameters in step (3) are: bombardment time 10-20 min, bombardment parameters are: anode voltage 150-200 V, anode current 2-5 A, cathode current 20-25 A, and cathode voltage 20-23 V.

5. The preparation method according to claim 2, characterized in that: The process parameters for depositing the main peak film system in step (3) are as follows: the germanium layer is deposited by electron beam evaporation, the zinc selenide film layer is deposited by molybdenum boat thermal evaporation, the evaporation rate of the germanium layer is 6-8 A / S, and the evaporation rate of the zinc selenide film layer is 11-13 A / S.

6. The preparation method according to claim 2, characterized in that: The annealing temperature in step (3) is 150-200℃, the holding time is 1-2h, and the cooling rate is 0.8-1℃ / min.

7. The preparation method according to claim 2, characterized in that: The specified temperature in step (3) is 80-90℃.

8. The preparation method according to claim 2, characterized in that: The process parameters for depositing the sub-peak film system in step (4) are as follows: the germanium layer is deposited by electron beam evaporation, the zinc selenide film layer is deposited by molybdenum boat thermal evaporation, the evaporation rate of the germanium layer is 6-8 A / S, and the evaporation rate of the zinc selenide film layer is 11-13 A / S.

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