Design method and preparation method of film system of germanium-based high-transmittance wide-cut-off narrow-band optical filter

Abstract

The invention provides a design method and a preparation method of a film system of a germanium-based high-transmittance wide-cut-off narrow-band optical filter. The design method of the film system of the germanium-substrate high-transmittance wide-cut-off narrow-band optical filter comprises the following steps: designing an Sa and S1 surface narrow-band main film system, which comprises the following sub-steps: respectively taking four wavelengths of 4257nm, 4513nm, 7994nm and 10600nm as central wavelengths of optical film design, and using an F-P cavity film stack formula: Sub / (LH) 32L (HL) 4 / AIR, Sub being a germanium substrate, AIR representing air, L representing ZnS and H representing Ge; generating a film layer structure in which ZnS is used as a base, ZnS is positioned on the outermost layer and ZnS and Ge are alternated in the middle; the optimal film layer thickness is obtained through optimization; the invention relates to a Sb, S2 surface interference dielectric film system design, which comprises the following sub-steps: using 550nm as the center wavelength of optical film design, using a film stack formula: Sub / 3.7 (H2LK) 76.1 (K2LH) 8 / AIR, Sub as a germanium substrate, AIR representing air, L representing ZnS, H representing Ge, and K representing PbTe; generating a film layer structure in which ZnS is used as a base, the ZnS is located on the outermost layer, ZnS and Ge are alternated at the two ends, and ZnS and PbTe are alternated in the middle; and the optimal film layer thickness is obtained through optimization.

Description

Technical Field

[0001] The present disclosure relates to the field of infrared optical thin film technology, and more specifically to a design method and a preparation method of a film system of a germanium-based high-transmittance, wide-cutoff, narrow-band filter. Background Art

[0002] Narrowband filters are often used in infrared measurement, temperature control, security systems, spectrometers, spectral imaging, thermal radiation and other fields. With the accelerated development of industrialization, the emission of industrial waste gas has caused significant damage to the environment, especially the emission of greenhouse gases such as CO2, N2O, NF3, CH4, SF6 and other gases, which are also the main cause of global warming. At this stage, the detection device is based on the characteristics of greenhouse gases that absorb very large amounts of infrared spectra with their respective characteristic wavelengths as the center wavelength, and combines the corresponding algorithms to perform concentration inverse calculations, as shown in Table 1. The filters are designed with their respective characteristic wavelengths as the center wavelengths. The four prepared narrowband filters are assembled in the photoacoustic spectroscopy detection system, which can simultaneously monitor four greenhouse gases, CO2, N2O, CH4 and SF6. Figure 1 shown.

[0003] Table 1 Greenhouse gas characteristic spectrum

[0004] Gas composition Relative molecular weight Characteristic wave number / cm-1 Characteristic wavelength / μm <![CDATA[CO2]]> 44 2349 4.257 <![CDATA[NO2]]> 44 2216 4.513 <![CDATA[CH4]]> 16 1251 7.994 <![CDATA[SF6]]> 146 948 10.6

[0005] Current narrowband filters need to be further improved in design and preparation. Summary of the invention

[0006] In view of the problems existing in the background technology, an object of the present invention is to provide a design method and a preparation method of a film system of a germanium-based high-transmittance wide-cutoff narrow-band filter, which can ensure that the transmittance of the passband regions of the respective wavelengths designed and prepared for CO2 (characteristic wavelength 4257nm), N2O (characteristic wavelength 4513nm), CH4 (characteristic wavelength 7994nm), and SF6 (characteristic wavelength 10600nm) meets the requirements and the transmittance in the cutoff bandwidth outside the passband region meets the requirements.

[0007] Another object of the present disclosure is to provide a method for designing and preparing a film system for a germanium-based high-transmittance, wide-cutoff, narrow-band filter, which can enable the germanium substrates and the film systems on both sides designed and prepared for CO2 (characteristic wavelength 4257nm), N2O (characteristic wavelength 4513nm), CH4 (characteristic wavelength 7994nm), and SF6 (characteristic wavelength 10600nm) to meet the requirements of different application scenarios.

[0008] Another object of the present disclosure is to provide a design method and a preparation method for a film system of a germanium-based high-transmittance wide-cutoff narrow-band filter, which can simplify the production of CO2 (characteristic wavelength 4257nm), N2O (characteristic wavelength 4513nm), CH4 (characteristic wavelength 7994nm), and SF6 (characteristic wavelength 10600nm), and is conducive to reducing costs, improving production efficiency, and especially large-scale production.

[0009] Thus, a method for designing a film system of a germanium substrate high-transmittance wide-cutoff narrow-band filter includes the steps of: Sa, S1 surface narrow-band main film system design, including sub-steps: Sa1, using 4257nm, 4513nm, 7994nm, and 10600nm as the central wavelengths of the optical film design, using the FP cavity film stack formula: Sub / (LH)^3 2L(HL)^4 / AIR, where Sub is a germanium substrate and AIR represents air. In the film stack formula, L represents a low-refractive-index material ZnS (zinc sulfide) with a thickness of 1 / 4 wavelength; H represents a high-refractive-index material Ge (germanium) with a thickness of 1 / 4 wavelength; Sa2, through the input film stack formula, a film layer structure with Sub / ZnS / Ge / ZnS / Ge…Ge / ZnS / Air is generated, with ZnS as the base, ZnS in the outermost layer, and ZnS and Ge alternating in the middle; Sa3, the film layer thickness is optimized through thin film design software to obtain the optimal film layer thickness of the S1 surface, and the transmittance of the passband region of each of the four wavelengths of the optimized film layer structure of the S1 surface meets the requirements; Sa4, the optimal film layer thickness of the S1 surface after optimization is input into the control circuit of the coating machine brain; Sb, S2 surface interference dielectric film system design, including sub-steps: Sb1, taking 550nm as the central wavelength of the optical film design, using the film stack formula: Sub / 3.7(H2LK)^76.1(K2LH)^8 / AIR, where Sub is the germanium substrate and AIR represents air. In the film stack formula: L represents the low refractive index material ZnS (zinc sulfide) with a thickness of 1 / 4 wavelength; H represents the high refractive index material Ge (germanium) with a thickness of 1 / 4 wavelength; K represents the high refractive index material PbTe (lead telluride) with a thickness of 1 / 4 wavelength; Sb2, through the input film stack formula, generate Sub / ZnS / Ge / ZnS / Ge / ZnS / Ge / ZnS / PbTe…ZnS / PbTe / ZnS / Ge / ZnS / Ge / ZnS / Ge / Zn The film structure of S / Air is ZnS as the base, ZnS in the outermost layer, ZnS and Ge alternating at both ends, and ZnS and PbTe alternating in the middle; Sb3, the film thickness is optimized by thin film design software to obtain the best film thickness of the S2 surface, and the transmittance of the passband area of ​​each of the four wavelengths of the optimized film structure of the S2 surface meets the requirements, and the transmittance in the cutoff bandwidth outside the passband area meets the requirements; Sa4, the best film thickness of the optimized S2 surface is input into the control computer of the coating machine.

[0010] A method for preparing a film system of a germanium-based high-transmittance wide-cutoff narrow-band filter comprises the following steps: step 1, cleaning a germanium-based product as a lens and a co-plating sheet before plating, and preparing three kinds of film materials: ZnS, Ge, and PbTe; step 2, configuring the coating process conditions and process files, wherein the coating process conditions and process files include coating temperature, background vacuum before plating, film thickness, film material evaporation mode, film material deposition rate, use and parameters of ion source assisted deposition, wherein the optimal film thickness is based on the S stored in the control computer of the coating machine in the design method of the film system of the germanium-based high-transmittance wide-cutoff narrow-band filter. The optimal film thickness of the corresponding surface of surface S1 and surface S2; step 3, put the cleaned lens into the fixture, hang the fixture with the lens in place into the chamber of the coating machine, close the door and evacuate and heat; step 4, pre-melting of the film material; step 5, ion source cleaning of the lens; step 6, film coating and monitoring, according to the coating process conditions of step 2 and the configuration of the process file, one of the S1 and S2 surfaces of the lens is used as the first surface for film coating; step 7, keep the constant temperature after coating; step 8, cool down and take out the piece; step 9, repeat steps 1 to 8, and the other surface of the S1 and S2 surfaces of the lens is used as the second surface for film coating.

[0011] The beneficial effects of the present disclosure are as follows.

[0012] In the film system design method of the germanium substrate high-transmittance wide-cutoff narrow-band filter according to the present disclosure, the film system design and optimization of the film layer structure with ZnS as the base on the S1 surface, ZnS in the outermost layer, ZnS and Ge alternating in the middle, and the film layer structure with ZnS as the base on the S2 surface, ZnS in the outermost layer, ZnS and Ge alternating at both ends, and ZnS and PbTe alternating in the middle can not only make the transmittance of the passband region of each of the four wavelengths of the film layer structure on the S1 surface meet the requirements, the transmittance of the passband region of each of the four wavelengths of the film layer structure on the S2 surface meet the requirements, and the transmittance in the cutoff bandwidth outside the passband region meets the requirements Moreover, taking into account the tests of the preparation process of the two-sided film system described later, such as the bubble test, salt spray test, adhesion test, constant temperature and humidity test, low temperature test and high temperature test described later, to meet the requirements of different application scenarios, the designed germanium substrate together with the film system on both sides can be suitable for the detection of components and concentrations of four greenhouse gases, CO2 (characteristic wavelength 4257nm), N2O (characteristic wavelength 4513nm), CH4 (characteristic wavelength 7994nm), and SF6 (characteristic wavelength 10600nm) in the photoacoustic spectroscopy detection system device, so as to provide an important basis for evaluating the greenhouse effect and formulating corresponding energy-saving and emission reduction measures.

[0013] In addition, in the film design method of the germanium substrate high-transmittance wide-cutoff narrow-band filter disclosed in the present invention, for the four wavelengths of 4257nm, 4513nm, 7994nm, and 10600nm, when the type of film material remains unchanged, the film layer structure with the same layout can be generated in step Sa2 and step Sb2, thereby greatly simplifying the preparation method (i.e., the production process) for the four wavelengths described later, which is beneficial to reducing the cost of the filter and improving the production efficiency of the filter, especially large-scale production.

[0014] In the method for preparing the film system of the germanium substrate high transmittance wide cut-off narrow band filter according to the present disclosure, based on the optimal film thickness of the corresponding surfaces of the S1 surface and the S2 surface stored in the control computer of the coating machine in the design method of the film system of the germanium substrate high transmittance wide cut-off narrow band filter described in steps 1 to 9, as verified by subsequent tests, not only can the transmittance of the prepared germanium substrate accompanying coating sheet together with the film system on both sides meet the requirements for the passband region of each wavelength in the four wavelengths at each wavelength and the transmittance in the cutoff bandwidth outside the passband region meet the requirements, but also can make the prepared germanium substrate The bottom accompanying coating sheet together with the film systems on both sides meet the requirements of blister test, salt spray test, adhesion test, constant temperature and humidity test, low temperature test and high temperature test to meet the requirements of different application scenarios, so that the prepared germanium-based product together with the film systems on both sides can be suitable for the detection of components and concentrations of four greenhouse gases, CO2 (characteristic wavelength 4257nm), N2O (characteristic wavelength 4513nm), CH4 (characteristic wavelength 7994nm), and SF6 (characteristic wavelength 10600nm) in the photoacoustic spectroscopy detection system, so as to provide an important basis for evaluating the greenhouse effect and formulating corresponding energy-saving and emission reduction measures.

[0015] Similarly, in the method for preparing a film system for a germanium-based high-transmittance wide-cutoff narrow-band filter according to the present invention, for the four wavelengths of 4257nm, 4513nm, 7994nm, and 10600nm, when the type of film material remains unchanged, the optimal film thickness of the corresponding surfaces of the S1 surface and the S2 surface stored in the control computer of the coating machine in the design method of the film system for a germanium-based high-transmittance wide-cutoff narrow-band filter described above (and the film layer structure with the same layout) greatly simplifies the preparation method (i.e., the production process) for the four wavelengths described later, which is beneficial to reducing the cost of the filter and improving the production efficiency of the filter, especially for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure in which four narrow-band filters are assembled in a photoacoustic spectroscopy detection system to simultaneously monitor four greenhouse gases: CO2, CH4, N2O, and SF6.

[0017] Figure 2 These are spectrum diagrams for the central wavelength of 4257nm, where (a) is the main film system spectrum diagram of the S1 surface of the designed method, (b) is the cutoff film system spectrum diagram of the S2 surface of the designed method, and (c) is the measured spectrum diagram of the accompanying coating film of the preparation method together with the film systems on both sides.

[0018] Figure 3 These are spectrum diagrams for the central wavelength of 4513nm, where (a) is the main film system spectrum diagram of the S1 surface of the designed method, (b) is the cutoff film system spectrum diagram of the S2 surface of the designed method, and (c) is the measured spectrum diagram of the accompanying coating film of the preparation method together with the film systems on both sides.

[0019] Figure 4 These are spectrum diagrams for the central wavelength of 7994nm, where (a) is the main film system spectrum diagram of the S1 surface of the designed method, (b) is the cutoff film system spectrum diagram of the S2 surface of the designed method, and (c) is the measured spectrum diagram of the accompanying coating film of the preparation method together with the film systems on both sides.

[0020] Figure 5 These are spectrum diagrams for the central wavelength of 10600nm, where (a) is the main film system spectrum diagram of the S1 surface of the designed method, (b) is the cutoff film system spectrum diagram of the S2 surface of the designed method, and (c) is the measured spectrum diagram of the accompanying coating film of the preparation method together with the film system on both sides. DETAILED DESCRIPTION

[0021] It is understood that the disclosed embodiments are merely examples of the present disclosure, which may be implemented in various forms, and therefore, the specific details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to variously implement the present disclosure.

[0022] [Design method of film system for germanium-based high-transmittance, wide-cutoff, narrow-band filter]

[0023] The method for designing a film system of a germanium-based high-transmittance wide-cutoff narrow-band filter disclosed in the present invention comprises the following steps:

[0024] Sa, S1 surface narrow band main film design, including sub-steps:

[0025] Sa1, with 4257nm, 4513nm, 7994nm, and 10600nm as the central wavelengths of the optical film design, using the FP cavity film stack formula: Sub / (LH)^3 2L

[0026] (HL)^4 / AIR, where Sub is the germanium substrate and AIR represents air. In the membrane stack formula:

[0027] L represents the low refractive index material ZnS (zinc sulfide) with a thickness of 1 / 4 wavelength;

[0028] H represents the high refractive index material Ge (germanium) with a thickness of 1 / 4 wavelength;

[0029] Sa2, through the input film stack formula, generates a film layer structure with ZnS as the bottom, ZnS as the outermost layer, and ZnS and Ge alternating in the middle;

[0030] Sa3, optimizing the film thickness by thin film design software to obtain the best film thickness of the S1 surface, and the transmittance of the passband region of each of the four wavelengths of the optimized film structure of the S1 surface meets the requirements;

[0031] Sa4, input the optimal film thickness of the optimized S1 surface into the control computer of the coating machine;

[0032] The design of Sb and S2 surface interference dielectric film system includes the following sub-steps:

[0033] Sb1, with 550nm as the central wavelength of the optical film design, uses the film stack formula: Sub /

[0034] 3.7(H2LK)^7 6.1(K2LH)^8 / AIR, where Sub is the germanium substrate and AIR represents air. In the membrane stack formula:

[0035] L represents the low refractive index material ZnS (zinc sulfide) with a thickness of 1 / 4 wavelength;

[0036] H represents the high refractive index material Ge (germanium) with a thickness of 1 / 4 wavelength;

[0037] K represents the high refractive index material PbTe (lead telluride) with a thickness of 1 / 4 wavelength;

[0038] Sb2, through the input film stack formula, generates Sub / ZnS / Ge / ZnS / Ge / ZnS / Ge / ZnS / PbTe…ZnS / PbTe / ZnS / Ge / ZnS / Ge / ZnS

[0039] / Ge / ZnS / Air has a film structure with ZnS as the base, ZnS as the outermost layer, ZnS and Ge alternating at both ends, and ZnS and PbTe alternating in the middle;

[0040] Sb3, the film thickness is optimized by thin film design software to obtain the best film thickness of the S2 surface, and the transmittance of the passband region of each wavelength of the optimized S2 surface film structure in the four wavelengths meets the requirements and the transmittance in the cutoff bandwidth outside the passband region meets the requirements;

[0041] Sa4, input the optimal film thickness of the optimized S2 surface into the control computer of the coating machine.

[0042] In the film system design method of the germanium substrate high-transmittance wide-cutoff narrow-band filter according to the present disclosure, the film system design and optimization of the film layer structure with ZnS as the base on the S1 surface, ZnS in the outermost layer, ZnS and Ge alternating in the middle, and the film layer structure with ZnS as the base on the S2 surface, ZnS in the outermost layer, ZnS and Ge alternating at both ends, and ZnS and PbTe alternating in the middle can not only make the transmittance of the passband region of each of the four wavelengths of the film layer structure on the S1 surface meet the requirements, the transmittance of the passband region of each of the four wavelengths of the film layer structure on the S2 surface meet the requirements, and the transmittance in the cutoff bandwidth outside the passband region meets the requirements Moreover, taking into account the tests of the preparation process of the two-sided film system described later, such as the bubble test, salt spray test, adhesion test, constant temperature and humidity test, low temperature test and high temperature test described later, to meet the requirements of different application scenarios, the designed germanium substrate together with the film system on both sides can be suitable for the detection of components and concentrations of four greenhouse gases, CO2 (characteristic wavelength 4257nm), N2O (characteristic wavelength 4513nm), CH4 (characteristic wavelength 7994nm), and SF6 (characteristic wavelength 10600nm) in the photoacoustic spectroscopy detection system device, so as to provide an important basis for evaluating the greenhouse effect and formulating corresponding energy-saving and emission reduction measures.

[0043] In addition, in the film design method of the germanium substrate high-transmittance wide-cutoff narrow-band filter disclosed in the present invention, for the four wavelengths of 4257nm, 4513nm, 7994nm, and 10600nm, when the type of film material remains unchanged, the film layer structure with the same layout can be generated in step Sa2 and step Sb2, thereby greatly simplifying the preparation method (i.e., the production process) for the four wavelengths described later, which is beneficial to reducing the cost of the filter and improving the production efficiency of the filter, especially large-scale production.

[0044] In one example, in sub-step Sa3, the optimal film thickness is:

[0045]

[0046] In sub-step Sb3, the optimal film thickness is:

[0047]

[0048]

[0049] In one example, in sub-step Sa3,

[0050]

[0051] In sub-step Sb3,

[0052]

[0053] In one example, in step Sa and step Sb, the design software is TFCalc or Essential Macleod.

[0054] [Method for preparing a film system of a germanium-based high-transmittance, wide-cutoff, narrow-band filter]

[0055] The method for preparing the film system of the germanium substrate high-transmittance wide-cutoff narrow-band filter disclosed in the present invention comprises the steps of:

[0056] Step 1: Before plating, the germanium substrate product and the accompanying plating sheet used as the lens are cleaned and the three film materials of ZnS, Ge and PbTe are prepared;

[0057] Step 2, configuration of coating process conditions and process files, including coating temperature, background vacuum before coating, film thickness, film material evaporation mode, film material deposition rate, use and parameters of ion source assisted deposition, wherein the optimal film thickness is based on the optimal film thickness of the corresponding surfaces of the S1 surface and the S2 surface stored in the control computer of the coating machine in the design method of the film system of the germanium substrate high transmittance wide cutoff narrow band filter described above;

[0058] Step 3: Put the cleaned lens into the fixture, hang the fixture with the lens into the cavity of the coating machine, close the door, and vacuum and heat;

[0059] Step 4: pre-melting of film material;

[0060] Step 5, ion source cleaning lens;

[0061] Step 6, coating and monitoring of the film layer, coating the film layer on one of the S1 surface and the S2 surface of the lens as the first surface according to the coating process conditions and configuration of the process file of step 2;

[0062] Step 7: After coating, keep the temperature constant;

[0063] Step 8, cooling down and picking up the items;

[0064] Step nine, repeat steps one to eight, and coat the other of the S1 and S2 surfaces of the lens as the second surface.

[0065] In the method for preparing the film system of the germanium substrate high transmittance wide cut-off narrow band filter according to the present disclosure, based on the optimal film thickness of the corresponding surfaces of the S1 surface and the S2 surface stored in the control computer of the coating machine in the design method of the film system of the germanium substrate high transmittance wide cut-off narrow band filter described in steps 1 to 9, as verified by subsequent tests, not only can the transmittance of the prepared germanium substrate accompanying coating sheet together with the film system on both sides meet the requirements for the passband region of each wavelength in the four wavelengths at each wavelength and the transmittance in the cutoff bandwidth outside the passband region meet the requirements, but also can make the prepared germanium substrate The bottom accompanying coating sheet together with the film systems on both sides meet the requirements of blister test, salt spray test, adhesion test, constant temperature and humidity test, low temperature test and high temperature test to meet the requirements of different application scenarios, so that the prepared germanium-based product together with the film systems on both sides can be suitable for the detection of components and concentrations of four greenhouse gases, CO2 (characteristic wavelength 4257nm), N2O (characteristic wavelength 4513nm), CH4 (characteristic wavelength 7994nm), and SF6 (characteristic wavelength 10600nm) in the photoacoustic spectroscopy detection system, so as to provide an important basis for evaluating the greenhouse effect and formulating corresponding energy-saving and emission reduction measures.

[0066] Similarly, in the method for preparing a film system for a germanium-based high-transmittance wide-cutoff narrow-band filter according to the present invention, for the four wavelengths of 4257nm, 4513nm, 7994nm, and 10600nm, when the type of film material remains unchanged, the optimal film thickness of the corresponding surfaces of the S1 surface and the S2 surface stored in the control computer of the coating machine in the design method of the film system for a germanium-based high-transmittance wide-cutoff narrow-band filter described above (and the film layer structure with the same layout) greatly simplifies the preparation method (i.e., the production process) for the four wavelengths described later, which is beneficial to reducing the cost of the filter and improving the production efficiency of the filter, especially for large-scale production.

[0067] In one example, in step one, the product is a (25.4±0.1) mm×(1±0.05) mm wafer, and the accompanying plating wafer is a (25±0.1) mm×(1±0.1) mm wafer.

[0068] The cleaning in step 1 makes the surface of the lens clean, which is conducive to the adhesion and bonding of the film layer. In one example, the lens is polished with aluminum oxide polishing liquid and then cleaned with ultrasonic pure water. Specifically, the aluminum oxide polishing liquid uses a 0.1 μm polycrystalline diamond liquid produced by Nanjing Henry Precision Optics Co., Ltd.

[0069] In one example, in step 2, the coating temperature is 150±2°C; the background vacuum before coating is (1.0±0.1)×10 -3Pa; the thickness of the film layer in the configuration of the coating process conditions and process files is based on the optimal film thickness of the corresponding surface stored in the control computer of the coating machine in the design method of the film system of the germanium substrate high transmittance wide cut-off narrow band filter mentioned above; the evaporation mode of the film material is: ZnS and PbTe are evaporated by resistance heating, and Ge is evaporated by electron beam heating; the deposition rate of the film material is: the deposition rate of the ZnS film layer is The deposition rate of the Ge film is The deposition rate of the PbTe film is The use of ion source assisted deposition is: all film layers are coated without turning on the ion source.

[0070] In one example, in step 2, the coating machine is Leybold ARES1350.

[0071] In one example, in step 3, the vacuum is first evacuated to 5×10 -2 Pa, and then the chamber of the coating machine starts heating, thereby preventing the germanium substrate from oxidizing under hot and humid conditions.

[0072] In step 4, the film material is pre-melted to release air and remove impurities to ensure the purity of the film material. In step 4, when the vacuum reaches (4.0-5.0)×10 -3 Pa, the film material is pre-melted. After the pre-melting of the film material is completed, the temperature of the cavity of the coating machine reaches 150°C and is kept constant for 10 minutes. Specifically, for example, in step 4, the pre-melting treatment adopts electron beam heating and resistance heating. For ZnS film material, the current of resistance heating is 720-760mA; for Ge film material, the current of electron beam heating is 260-290mA; for PbTe film material, the current of resistance heating is 420-460mA.

[0073] The ion source cleaning in step 5 removes the surface oxide layer and attached particles of the germanium substrate, making the surface of the germanium substrate cleaner and increasing the adhesion of the film layer. In one example, in step 5, the vacuum degree of the chamber reaches (1.0±0.1)×10 -3 Pa, start the ion source to perform ion cleaning on the lens, the ion source is a Hall source, the ion source parameters are, neutralization current 0.6±0.01A, neutralization gas flow 8±0.1sccm, anode voltage 130±2V, anode current 1±0.01A, no oxygen is filled in the whole process, the argon ratio is 100%, and the cleaning time is 300±2s.

[0074] In one example, in step six, when coating each film layer, no protective gas is introduced from the outside of the coating machine, but the inner cavity of the coating machine is maintained to be evacuated, and the coating temperature is maintained at 150°C; each film layer is coated at a cavity temperature of 150°C in the coating machine; the crystal oscillator method is used to monitor the film thickness using the corresponding crystal oscillator of the multiple crystal oscillators of the crystal controller, and after the ion source is cleaned, the crystal controller controls the corresponding operation of the new crystal oscillator among the multiple crystal oscillators, and the crystal oscillator frequency is not less than 5850Hz.

[0075] In one example, in step seven, the chamber is kept at 150±2° C. for 30 minutes after plating is completed.

[0076] In one example, in step eight, after step seven is completed, the temperature is first lowered to 130±2°C at 1°C / min and held for 5 minutes, then lowered to 110±2°C at 1°C / min and held for 5 minutes, and finally lowered to below 80±2°C at 1°C / min, and the door is opened to take out the items.

[0077] [test]

[0078] Example 1

[0079] Part 1: Design method of film system for germanium substrate high transmittance wide cutoff narrow band filter

[0080] The design method of the film system of the germanium substrate high transmittance wide cut-off narrow band filter adopts the following steps:

[0081] The design of the narrow band main film system on Sa and S1 surfaces adopts the following sub-steps:

[0082] Sa1, with 4257nm, 4513nm, 7994nm, and 10600nm as the central wavelengths of the optical thin film design, uses the FP cavity film stack formula in TFCalc:

[0083] Sub / (LH)^3 2L(HL)^4 / AIR, where Sub is the germanium substrate and AIR represents air. In the membrane stack formula:

[0084] L represents the low refractive index material ZnS (zinc sulfide) with a thickness of 1 / 4 wavelength;

[0085] H represents the high refractive index material Ge (germanium) with a thickness of 1 / 4 wavelength;

[0086] Sa2, through the input film stack formula, generates a film layer structure with ZnS as the bottom, ZnS as the outermost layer, and ZnS and Ge alternating in the middle;

[0087] Sa3, the film thickness is optimized by thin film design software TFCalc to obtain the best film thickness of S1 surface. The transmittance of the passband region of each of the four wavelengths of the optimized film structure of S1 surface meets the requirements.

[0088] In sub-step Sa3, the optimal film thickness is:

[0089]

[0090] In sub-step Sa3,

[0091]

[0092] Sa4, input the optimized film thickness of the S1 surface into the control computer of the coating machine, the coating machine is Leybold ARES1350;

[0093] The design of Sb and S2 surface interference dielectric film system adopts the following sub-steps:

[0094] Sb1, with 550nm as the central wavelength of the optical film design, in TFCalc, use the film stack formula: Sub / 3.7(H2LK)^7 6.1(K2LH)^8 / AIR, where Sub is the germanium substrate and AIR represents air. In the film stack formula:

[0095] L represents the low refractive index material ZnS (zinc sulfide) with a thickness of 1 / 4 wavelength;

[0096] H represents the high refractive index material Ge (germanium) with a thickness of 1 / 4 wavelength;

[0097] K represents the high refractive index material PbTe (lead telluride) with a thickness of 1 / 4 wavelength;

[0098] Sb2, through the input film stack formula, generates a film layer structure with Sub / ZnS / Ge / ZnS / Ge / ZnS / Ge / ZnS / PbTe…ZnS / PbTe / ZnS / Ge / ZnS / Ge / ZnS / Ge / ZnS / Air, with ZnS as the bottom layer, ZnS at the outermost layer, ZnS and Ge alternating at both ends, and ZnS and PbTe alternating in the middle;

[0099] Sb3, the film thickness is optimized by thin film design software TFCalc to obtain the best film thickness of S2 surface, the transmittance of the passband region of each wavelength of the optimized S2 surface film structure in the four wavelengths meets the requirements and the transmittance in the cutoff bandwidth outside the passband region meets the requirements,

[0100] In sub-step Sb3, the optimal film thickness is:

[0101]

[0102]

[0103] In sub-step Sb3,

[0104]

[0105] Sa4, input the optimal film thickness of the optimized S2 surface into the control computer of the coating machine, and the coating machine is the Leybold ARES1350.

[0106] Part II: Preparation method of film system of germanium substrate high transmittance wide cut-off narrow band filter

[0107] The preparation method of the film system of the germanium substrate high transmittance wide cut-off narrow band filter adopts the following steps:

[0108] Step 1: Before plating, the germanium substrate product and the accompanying plating sheet used as the lens are cleaned and the three film materials of ZnS, Ge and PbTe are prepared. The product is a 25.4mm×1mm round wafer, and the accompanying plating sheet is a 25mm×1mm round wafer. The lens is polished with alumina polishing liquid and then cleaned with ultrasonic pure water. The alumina polishing liquid uses a 0.1μm polycrystalline diamond liquid produced by Nanjing Henry Precision Optics Co., Ltd.;

[0109] Step 2, configuration of coating process conditions and process files, including coating temperature, background vacuum before coating, film thickness, film material evaporation mode, film material deposition rate, use and parameters of ion source assisted deposition, wherein the optimal film thickness is based on the optimal film thickness of the corresponding surfaces of the S1 surface and the S2 surface stored in the control computer of the coating machine in the design method of the film system of the germanium substrate high transmittance wide cut-off narrow band filter in the first part, and the selected characteristic wavelength is 10600nm,

[0110] In step 2,

[0111] The coating temperature is 150°C;

[0112] The background vacuum before plating is 1.0×10 -3 Pa;

[0113] The thickness of the film layer in the configuration of the coating process conditions and process files is based on the optimal film layer thickness of the corresponding surface stored in the control computer of the coating machine in the design method of the film system of the germanium substrate high transmittance wide cut-off narrow band filter in the first part, and the selected characteristic wavelength is 10600nm;

[0114] The evaporation mode of the film materials is: ZnS and PbTe are evaporated by resistance heating, and Ge is evaporated by electron beam heating;

[0115] The deposition rate of the film material is: The deposition rate of the ZnS film layer is The deposition rate of the Ge film is The deposition rate of the PbTe film is

[0116] The use of ion source assisted deposition is: all film layers are coated without turning on the ion source;

[0117] Step 3: Put the cleaned lens into the fixture, hang the fixture with the lens into the chamber of the coating machine, close the door, and vacuum it to 5×10 -2 Pa, after which the coating machine cavity starts heating;

[0118] Step 4: Pre-melting of film material. When the vacuum reaches 4.5×10 -3 The film material is pre-melted at Pa. After the pre-melting of the film material is completed, the temperature of the cavity of the coating machine reaches 150°C and is kept constant for 10 minutes.

[0119] In step 4, the pre-melting process uses electron beam heating and resistance heating.

[0120] For ZnS film material, the current of resistance heating is 740mA;

[0121] For Ge film material, the current of electron beam heating is 265mA;

[0122] For PbTe film material, the current of resistance heating is 440mA;

[0123] Step 5: The ion source cleans the lens and the vacuum degree of the chamber reaches 1.0×10 -3 Pa, start the ion source to clean the lens with ions. The ion source is a Hall source. The ion source parameters are: neutralization current 0.6A, neutralization gas flow 8sccm, anode voltage 130V, anode current 1A, no oxygen filling during the whole process, argon ratio 100%, and cleaning time 300s;

[0124] Step 6: Coating and monitoring of the film layer. According to the coating process conditions and process file configuration of step 2, the film layer is coated on one of the S1 and S2 surfaces of the lens as the first surface.

[0125] In step six,

[0126] When coating each film layer, no protective gas is introduced from the outside of the coating machine, but the inner cavity of the coating machine is kept evacuated and the coating temperature is kept at 150°C;

[0127] Each film layer is coated at a chamber temperature of 150°C in the coating machine;

[0128] The crystal oscillator method is used to monitor the film thickness using the corresponding crystal oscillator of the multiple crystal oscillators of the crystal controller. After the ion source is cleaned, the crystal controller controls the corresponding operation of the new crystal oscillator of the multiple crystal oscillators, and the crystal oscillator frequency is 5990Hz.

[0129] Step 7: After plating, keep the cavity at 150°C for 30 minutes;

[0130] Step 8: After step 7 is completed, first cool down to 130°C at 1°C / min and hold for 5 minutes, then cool down to 110°C at 1°C / min and hold for 5 minutes, and finally cool down to 80°C at 1°C / min, and open the door to take out the items;

[0131] Step nine, repeat steps one to eight, and coat the other of the S1 and S2 surfaces of the lens as the second surface.

[0132] Comparative Example 1

[0133] Except that the ion source is turned on when depositing the ZnS and Ge film layers in step 2, the ion source is a Hall source, and the ion source parameters are: neutralization current 0.6A, neutralization gas flow rate 8sccm, anode voltage 130V, anode current 1A, no oxygen is added throughout the process, and the argon ratio is 100%, the rest is the same as Example 1.

[0134] Comparative Example 2

[0135] Except that the film material ZnSe (zinc selenide) replaces the film material ZnS (zinc sulfide) in step 1, step 2 and step 4 (that is, only the film material is replaced), the rest is the same as in Example 1.

[0136] Comparative Example 3

[0137] Except that the film material PbTe (lead telluride) is used to replace the film material Ge (germanium) in step 1, step 2 and step 4 (that is, only the film material is replaced), the rest is the same as in Example 1.

[0138] Comparative Example 4

[0139] Except that the coating temperature in step 2 is 180°C, the temperature of the cavity of the coating machine in step 4 reaches 180°C, the coating temperature is maintained at 180°C in step 6, and each film layer is plated at a cavity temperature of 180°C in the coating machine, the rest is the same as Example 1.

[0140] Comparative Example 5

[0141] Except for the background vacuum of 3×10 -3 Pa, the vacuum degree of the chamber in step 5 reaches 3×10 -3 Except for Pa, the rest is the same as in Example 1.

[0142] Comparative Example 6

[0143] Except that the deposition rate of the PbTe film in step 2 is Other than that, the same as in Example 1.

[0144] Example 2

[0145] Except that the characteristic wavelength selected in step 2 is 7994 nm, the rest is the same as in Example 1.

[0146] Example 3

[0147] Except for the characteristic wavelength of 4513 nm selected in step 2, the rest is the same as in Example 1.

[0148] Example 4

[0149] Except for the characteristic wavelength of 4257 nm selected in step 2, the rest is the same as in Example 1.

[0150] Figure 2 It is a spectrum diagram for the central wavelength of 4257nm, among which (a) is the main film system spectrum diagram of the S1 surface of the designed method, (b) is the cutoff film system spectrum diagram of the S2 surface of the designed method, and (c) is the measured spectrum diagram of the accompanying coating sheet of the preparation method (corresponding to Example 4) together with the film system on both sides.

[0151] Figure 3 It is a spectrum diagram for the central wavelength of 4513nm, among which (a) is the main film system spectrum diagram of the S1 surface of the designed method, (b) is the cutoff film system spectrum diagram of the S2 surface of the designed method, and (c) is the measured spectrum diagram of the accompanying coating sheet of the preparation method (corresponding to Example 3) together with the film system on both sides.

[0152] Figure 4 It is a spectrum diagram for the central wavelength of 7994nm, among which (a) is the main film system spectrum diagram of the S1 surface of the designed method, (b) is the cutoff film system spectrum diagram of the S2 surface of the designed method, and (c) is the measured spectrum diagram of the accompanying coating sheet of the preparation method (corresponding to Example 2) together with the film system on both sides.

[0153] Figure 5 It is a spectrum diagram for the central wavelength of 10600nm, among which (a) is the main film system spectrum diagram of the S1 surface of the designed method, (b) is the cutoff film system spectrum diagram of the S2 surface of the designed method, and (c) is the measured spectrum diagram of the accompanying coating sheet of the preparation method (corresponding to Example 1) together with the film system on both sides.

[0154] The accompanying plating sheets of Example 1, Comparative Examples 1-6 and Examples 2-4, together with the film systems on both sides, were subjected to the following overall performance test.

[0155] Water bubble test: Take tap water to conduct a water bubble test for 2 hours to observe whether the film layer on each surface falls off or cracks.

[0156] Salt spray test: neutral salt spray test for 24 hours, observe whether the film layer on each surface falls off or cracks.

[0157] Adhesion test: Use your hands to stick 3M tape on each side and pull the tape in the direction opposite to the sticking end to see if the film layer is pulled up.

[0158] Constant temperature and humidity test: In a constant temperature and humidity chamber, at 50°C and 95% relative humidity for 24 hours, observe whether the film layers on each surface fall off or crack.

[0159] Low temperature test: In a low temperature box, at -40℃ for 24 hours, observe whether the film layers on each surface fall off or crack.

[0160] High temperature test: In a high temperature box, 85℃ for 24h, observe whether the film layers on each surface fall off or crack.

[0161] Table 1 shows the peak transmittance, half-peak bandwidth, cutoff depth (transmittance T of the cutoff bandwidth) of the accompanying coating sheets of Example 1, Comparative Examples 1-6 and Examples 2-4, together with the corresponding characteristic wavelengths on both sides, and the results of their respective tests.

[0162] Table 1 Peak transmittance, half-peak bandwidth, cut-off depth (transmittance T of cut-off bandwidth) of the accompanying coating sheets of Example 1, Comparative Examples 1-6 and Examples 2-4 together with the corresponding characteristic wavelengths on both sides and the results of their respective tests

[0163]

[0164]

[0165] The above detailed description is used to describe multiple exemplary embodiments, but this document is not intended to be limited to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined together to form multiple additional combinations that are not shown for the sake of simplicity.

Claims

1. A method for designing a film system of a germanium-based high-transmittance, wide-cutoff, narrow-band filter, characterized in that: Includes steps: Sa, S1 surface narrow band main film design, including sub-steps: Sa1, with 4257nm, 4513nm, 7994nm, and 10600nm as the central wavelengths of the optical film design, uses the FP cavity film stack formula: Sub / (LH)^3 2L(HL)^4 / AIR, where Sub is the germanium substrate and AIR represents air. In the film stack formula: L represents the low refractive index material ZnS (zinc sulfide) with a thickness of 1 / 4 wavelength; H represents the high refractive index material Ge (germanium) with a thickness of 1 / 4 wavelength; Sa2, through the input membrane stack formula, generates Sub / ZnS / Ge / ZnS / Ge…Ge / ZnS / Air has a film structure with ZnS as the base, ZnS as the outermost layer, and ZnS and Ge alternating in the middle; Sa3, optimizing the film thickness by thin film design software to obtain the best film thickness of the S1 surface, and the transmittance of the passband region of each of the four wavelengths of the optimized film structure of the S1 surface meets the requirements; Sa4, inputting the optimal film thickness of the optimized S1 surface into the control computer of the coating machine; The design of Sb and S2 surface interference dielectric film system includes the following sub-steps: Sb1, with 550nm as the central wavelength of the optical film design, uses the film stack formula: Sub / 3.7(H2LK)^7 6.1(K2LH)^8 / AIR, where Sub is the germanium substrate and AIR represents air. In the membrane stack formula: L represents the low refractive index material ZnS (zinc sulfide) with a thickness of 1 / 4 wavelength; H represents the high refractive index material Ge (germanium) with a thickness of 1 / 4 wavelength; K represents the high refractive index material PbTe (lead telluride) with a thickness of 1 / 4 wavelength; Sb2, through the input membrane stack formula, generates The film structure of Sub / ZnS / Ge / ZnS / Ge / ZnS / Ge / ZnS / PbTe…ZnS / PbTe / ZnS / Ge / ZnS / Ge / ZnS / Ge / ZnS / Air is ZnS as the base, ZnS is at the outermost layer, ZnS and Ge alternate at both ends, and ZnS and PbTe alternate in the middle; Sb3, the film thickness is optimized by thin film design software to obtain the best film thickness of the S2 surface, and the transmittance of the passband region of each wavelength of the optimized S2 surface film structure in the four wavelengths meets the requirements and the transmittance in the cutoff bandwidth outside the passband region meets the requirements; Sa4, input the optimal film thickness of the optimized S2 surface into the control computer of the coating machine.

2. The method for designing a film system of a germanium-based high-transmittance wide-cutoff narrow-band filter according to claim 1, characterized in that: In sub-step Sa3, the optimal film thickness is: In sub-step Sb3, the optimal film thickness is: In sub-step Sa3, In sub-step Sb3, 3. A method for preparing a film system of a germanium-based high-transmittance, wide-cutoff, narrow-band filter, characterized in that: Includes steps: Step 1: Before plating, the germanium substrate product and the accompanying plating sheet used as the lens are cleaned and the three film materials of ZnS, Ge and PbTe are prepared; Step 2, configuration of coating process conditions and process files, including coating temperature, background vacuum before coating, film thickness, evaporation mode of film material, deposition rate of film material, use and parameters of ion source assisted deposition, wherein the optimal film thickness is based on the optimal film thickness of the corresponding surface of the S1 surface and the S2 surface stored in the control computer of the coating machine according to any one of claims 1-2; Step 3: Put the cleaned lens into the fixture, hang the fixture with the lens into the cavity of the coating machine, close the door, and vacuum and heat; Step 4: pre-melting of film material; Step 5, cleaning the lens with the ion source; Step 6, coating and monitoring of the film layer, coating the film layer on one of the S1 surface and the S2 surface of the lens as the first surface according to the coating process conditions and configuration of the process file of step 2; Step 7: After coating, keep the temperature constant; Step 8, cooling down and picking up the items; Step nine, repeat steps one to eight, and coat the other of the S1 and S2 surfaces of the lens as the second surface.

4. The method for preparing the film system of the germanium-based high-transmittance wide-cutoff narrow-band filter according to claim 3, characterized in that: In step one, The product is a (25.4±0.1)mm×(1±0.05)mm round disc, and the accompanying plating sheet is a (25±0.1)mm×(1±0.1)mm round disc; The lenses are polished with aluminum oxide polishing liquid and then cleaned with ultrasonic pure water; The alumina polishing liquid adopts the 0.1μm polycrystalline diamond liquid produced by Nanjing Henry Precision Optics Co., Ltd.

5. The method for preparing the film system of the germanium-based high-transmittance wide-cutoff narrow-band filter according to claim 3, characterized in that: In step 2, The coating temperature is 150±2℃; The background vacuum before plating is (1.0±0.1)×10 -3 Pa; Coating process conditions and film thickness in the configuration of process files Based on the optimal film thickness of the corresponding surface stored in the control computer of the coating machine according to claim 2; The evaporation mode of the film materials is: ZnS and PbTe are evaporated by resistance heating, and Ge is evaporated by electron beam heating; The deposition rate of the film material is: The deposition rate of the ZnS film layer is The deposition rate of the Ge film is The deposition rate of the PbTe film is The use of ion source assisted deposition is: all film layers are coated without turning on the ion source; The coating machine is Leybold ARES1350.

6. The method for preparing a film system of a germanium-based high-transmittance wide-cutoff narrow-band filter according to claim 3, characterized in that: In step 3, first vacuum the air to 5×10 -2 Pa, after which the coating machine's cavity starts heating.

7. The method for preparing a film system of a germanium-based high-transmittance wide-cutoff narrow-band filter according to claim 3, characterized in that: In step 4, when the vacuum reaches (4.0-5.0)×10 -3 The film material is pre-melted at Pa. After the pre-melting of the film material is completed, the temperature of the cavity of the coating machine reaches 150°C and is kept constant for 10 minutes. In step 4, the pre-melting process uses electron beam heating and resistance heating. For ZnS film material, the current of resistance heating is 720-760mA; For Ge film material, the current of electron beam heating is 260-290mA; For PbTe film material, the current of resistance heating is 420-460mA.

8. The method for preparing a film system of a germanium-based high-transmittance wide-cutoff narrow-band filter according to claim 3, characterized in that: In step five, The vacuum degree of the cavity reaches (1.0±0.1)×10 -3 Pa, start the ion source to perform ion cleaning on the lens, the ion source is a Hall source, the ion source parameters are, neutralization current 0.6±0.01A, neutralization gas flow 8±0.1sccm, anode voltage 130±2V, anode current 1±0.01A, no oxygen is filled in the whole process, the argon ratio is 100%, and the cleaning time is 300±2s.

9. The method for preparing a film system of a germanium-based high-transmittance wide-cutoff narrow-band filter according to claim 3, characterized in that: In step six, When coating each film layer, no protective gas is introduced from the outside of the coating machine, but the inner cavity of the coating machine is kept evacuated and the coating temperature is kept at 150°C; Each film layer is coated at a chamber temperature of 150°C in the coating machine; The crystal oscillator method is used to monitor the film thickness using the corresponding crystal oscillator pieces of the multiple crystal oscillator pieces of the crystal controller. After the ion source is cleaned, the crystal controller controls the corresponding operation of the new crystal oscillator pieces among the multiple crystal oscillator pieces, and the crystal oscillator frequency is not less than 5850Hz.

10. The method for preparing a film system of a germanium-based high-transmittance wide-cutoff narrow-band filter according to claim 3, characterized in that: In step seven, after plating is completed, the cavity is kept at 150±2°C for 30 minutes; In step eight, after step seven is completed, first cool down to 130±2°C at 1°C / min and hold for 5 min, then cool down to 110±2°C at 1°C / min and hold for 5 min, and finally cool down to below 80±2°C at 1°C / min, and open the door to take out the items.

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