Low phase difference metal mirror suitable for space environment and preparation method and application thereof

Abstract

This invention relates to the field of optical thin film technology, specifically to a low-phase-difference metal mirror suitable for space environments, its fabrication method, and its applications. It includes an optical substrate and, sequentially deposited on the optical substrate, an adhesive layer, a metal layer, a first protective layer, a first low-refractive-index layer, a high-refractive-index layer, a second low-refractive-index layer, and a second protective layer. The optical substrate is silicon; the adhesive layer is made of nickel-chromium; the metal layer is made of silver; both the first and second protective layers are made of aluminum oxide; the first and second low-refractive-index layers are made of silicon dioxide; and the high-refractive-index layer is made of niobium pentoxide. This invention achieves high reflectivity over a wide wavelength range through the metal layer, utilizes the asymmetric equivalent layer theory in optical thin film design for phase difference control design to achieve phase difference control in the communication band, and utilizes the outermost protective layer to improve the adaptability and stability of the optical element under space environment conditions.

Description

Technical Field

[0001] This invention relates to the field of optical thin film technology, specifically to a low-phase-contrast metal mirror suitable for space environments, its preparation method, and its application. Background Technology

[0002] When light is incident at an angle, the effective refractive indices of the P-ray and S-ray in the optical thin film are inconsistent, causing energy separation, which increases with the angle. This not only leads to energy loss but also generates phase difference due to polarization separation in the optical thin film, causing changes in the polarization state of the light. In quantum communication, photons are manipulated to transmit and decode in specific polarization directions. Large phase differences in optical components directly increase the bit error rate in the quantum communication system. Therefore, phase modulation of the optical thin film components involved in the optical system is necessary. Previous studies have mostly used 750-900nm wavelength light sources for encoding and transmission, and to reduce interference, transmission was mostly conducted at night. Currently, to achieve all-day operation in medium and high orbits, and to suppress solar background noise and optimize atmospheric transmission efficiency, the telecommunications C-band (approximately 1530-1565nm) is required as the communication signal band. Therefore, the optical components in the optical system need to maintain high reflectivity and low phase difference within the above wavelength range, while also possessing good adaptability to the space environment. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a low-phase-aberration metallic reflector suitable for space environments. The reflector's coating exhibits high reflectivity and low phase aberration optical properties, while also being adaptable to space environments at medium to high orbital altitudes.

[0004] The further technical problem to be solved by the present invention is to provide a method for preparing and applying the above-mentioned low-phase-contrast metal mirror suitable for space environments.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A low-position phase difference metal reflector suitable for space environment includes an optical substrate and an adhesive layer, a metal layer, a first protective layer, a first low refractive index layer, a high refractive index layer, a second low refractive index layer and a second protective layer sequentially deposited on the optical substrate.

[0007] The optical substrate is silicon; the adhesive layer is nickel-chromium; the metal layer is silver; the first and second protective layers are both made of aluminum oxide; the first low-refractive-index layer is made of silicon dioxide; the second low-refractive-index layer is made of silicon dioxide; and the high-refractive-index layer is made of niobium pentoxide.

[0008] The thickness of the adhesive layer is 5-10 nm; the thickness of the metal layer is 130-150 nm.

[0009] The thickness of the first protective layer is 35 nm, the thickness of the second protective layer is 4-6 nm, the thickness of the first low refractive index layer is 115 nm, the thickness of the second low refractive index layer is 125 nm, and the thickness of the high refractive index layer is 160 nm.

[0010] The adhesive layer is made of 80Ni20Cr.

[0011] The low-phase metal reflector suitable for space environments has a working angle of 45 degrees, a reflectivity of greater than 98% in the range of 750~1600nm, and a phase difference of less than 2 degrees in signal wavelengths of 780±2nm, 842±2nm, 854±2nm, and 1540±2nm.

[0012] The above-mentioned method for fabricating a low-position phase-contrast metallic mirror suitable for space environments includes the following steps:

[0013] The optical substrate is placed in a vacuum coating machine, a vacuum is drawn, and after the vacuum level reaches the set value, ion pre-bombardment treatment is performed.

[0014] Then, vacuum coating is performed, first depositing the adhesive layer, the metal layer, and the first protective layer in sequence;

[0015] Then, the ion source is turned on, and while maintaining ion source bombardment, the first low refractive index layer, the high refractive index layer, the second low refractive index layer, and the second protective layer are deposited sequentially.

[0016] Finally, turn off the ion source and maintain a vacuum state for at least one and a half hours. Then, remove the optical substrate to obtain a low-phase-contrast metal mirror suitable for the space environment.

[0017] The deposition rate of the adhesive layer is 0.3~0.5 nm / s; the deposition rate of the metal layer is 0.8~1.2 nm / s; the deposition rate of the first protective layer and the second protective layer is 0.6~0.8 nm / s; the deposition rate of the high refractive index layer is 0.11~0.13 nm / s; and the deposition rate of the first low refractive index layer and the second low refractive index layer is 0.6~0.8 nm / s.

[0018] The adhesive layer and the metal layer are deposited using a thermal evaporation deposition method; the first protective layer is deposited using an electron beam evaporation deposition method; and the second protective layer, the high refractive index layer, the first low refractive index layer, and the second low refractive index layer are deposited using a radio frequency ion beam assisted electron beam evaporation deposition method.

[0019] The vacuum degree of the deposition is 1.0~1.5×10⁻⁶. -3 Pa.

[0020] The above-mentioned low-phase-contrast metal mirrors suitable for space environments are used in space laser communication and quantum communication systems.

[0021] The deposition equipment used in this invention is a box-type vacuum coating equipment with thermal evaporation and electron gun evaporation functions; the deposition method is thermal evaporation and electron beam evaporation; the auxiliary deposition is radio frequency ion beam assisted deposition, with a beam voltage of 1000V and a beam current of 400mA.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) The low phase difference metal mirror of the present invention, which is suitable for space environment, achieves high reflectivity in a wide band range through metal layer, uses the asymmetric equivalent layer theory in optical thin film design method to perform phase difference control design, realizes phase difference control in communication band, and uses the outermost protective layer to improve the adaptability and stability of optical components under space environment conditions.

[0024] (2) The low-position phase difference metal reflector of the present invention, which is suitable for the space environment, can be applied to all-day, medium-high orbit space laser communication and quantum communication systems, and has good space environment adaptability;

[0025] (3) The low-position phase difference metal reflector of the present invention has a thin total film thickness, which ensures the optical surface shape index requirements of the element and has high surface shape accuracy. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the low-position phase difference metal reflector of the present invention, suitable for space environments.

[0027] Figure 2 The reflectivity curve of the low-position phase difference metal mirror of the present invention, suitable for space environment.

[0028] Figure 3 The phase difference curve of the low phase difference metal mirror of the present invention, suitable for space environment.

[0029] The reference numerals in the attached drawings are: 1-optical substrate, 2-adhesive layer, 3-metal layer, 4-first protective layer, 5-first low refractive index layer, 6-high refractive index layer, 7-second low refractive index layer, and 8-second protective layer. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] See Figure 1 The present invention provides a low-position phase difference metal reflector suitable for space environment, which includes an optical substrate 1 and an adhesive layer 2, a metal layer 3, a first protective layer 4, a first low refractive index layer 5, a high refractive index layer 6, a second low refractive index layer 7 and a second protective layer 8 sequentially deposited on the optical substrate 1.

[0032] This invention provides a low phase difference metal mirror suitable for space environments. It achieves high reflectivity over a wide wavelength range through a metal layer 3, uses the asymmetric equivalent layer theory in optical thin film design to perform phase difference control design, realizes phase difference control in the communication band, and uses the outermost protective layer to improve the adaptability and stability of optical components under space environment conditions.

[0033] The low-phase metal reflector of the present invention, suitable for space environment, uses a first protective layer 4 to enhance the stability of metal layer 3 and a second protective layer 8 to improve the reliability of the reflector for use in space environment.

[0034] Example 1:

[0035] In this embodiment 1, silicon with a diameter of φ50×5mm is used as the optical substrate 1, nickel-chromium is selected as the adhesive layer 2, silver is selected as the metal layer 3, aluminum oxide is selected as the first protective layer 4 and the second protective layer 8, silicon dioxide is selected as the first low refractive index layer 5 and the second low refractive index layer 7, and niobium pentoxide is selected as the high refractive index layer 6.

[0036] Specifically, the adhesive layer 2 is nickel-chromium with a thickness of 5 nm; the metal layer 3 is silver with a thickness of 150 nm; the first protective layer 4 is aluminum oxide with a thickness of 35 nm; the first low refractive index layer 5 is silicon dioxide with a thickness of 115 nm; the high refractive index layer 6 is niobium pentoxide with a thickness of 160 nm; the second low refractive index layer 7 is silicon dioxide with a thickness of 125 nm; and the second protective layer 8 is aluminum oxide with a thickness of 5 nm.

[0037] The above-mentioned method for fabricating low-phase-contrast metallic mirrors suitable for space environments employs a box-type vacuum coating equipment with both thermal evaporation and electron gun evaporation functions for coating. The specific process of the mirror fabrication is as follows:

[0038] 1) Clean the optical substrate 1 (i.e., the silicon substrate) with a mixture of alcohol and ether, then place it on the workpiece holder in the vacuum chamber, and evacuate the vacuum chamber to 1.5 × 10⁻⁶. -3 Pa;

[0039] 2) Turn on the ion source and fill the vacuum chamber with O2 and Ar gases to make the vacuum chamber pressure 4~5×10 -2 Within the Pa range, the ion source beam voltage is 1000V and the beam current is 400mA. The substrate is pre-bombarded for 5 minutes, and then the ion source is turned off.

[0040] 3) A nickel-chromium film was first deposited using resistance thermal evaporation at a deposition rate of 0.3 nm / s, followed by a silver film at a deposition rate of 0.8 nm / s;

[0041] 4) The first protective layer, alumina 4, was deposited using electron beam evaporation at a deposition rate of 0.8 nm / s;

[0042] 5) Then turn on the ion source and fill the vacuum chamber with O2 and Ar gases to make the vacuum chamber pressure 4~5×10 - 2 Pa range, ion source beam voltage 1000V, beam current 400mA;

[0043] 6) The first low-refractive-index layer 5, silicon dioxide, was deposited by electron beam evaporation at a deposition rate of 0.8 nm / s, followed by the deposition of the high-refractive-index layer 6, niobium pentoxide, at a deposition rate of 0.11 nm / s. Then, the second low-refractive-index layer 7, silicon dioxide, and the second protective layer 8, aluminum oxide, were deposited sequentially using the same process, and then the ion source was turned off.

[0044] 7) After completing the preparation of each film layer, maintain the vacuum for 120 minutes, then open the vacuum chamber and remove the mirror to complete the preparation of the mirror.

[0045] Figure 2 This is the reflectivity curve of the low-position phase-contrast metallic mirror of the present invention, suitable for space environments. From... Figure 2 It can be seen that the working angle of the mirror prepared in Example 1 is 45 degrees, and the reflectivity is greater than 98% in the range of 750~1600nm.

[0046] Figure 3 This is the phase difference curve of the low-phase-contrast metallic mirror of the present invention, suitable for space environments. From Figure 3It can be seen that the signal channels of the reflector prepared in Example 1 are 780±2nm, 842±2nm, 854±2nm, and 1540±2nm, and the phase difference of the signal channels is less than 2 degrees.

[0047] The preparation method of the present invention improves the adhesion between the optical substrate 1 and the film by first pre-bombarding the optical substrate 1. Then, the process conditions of each step are strictly controlled to carry out layer-by-layer coating. After the first protective layer 4 is coated, the ion source is turned on and the first low refractive index layer 5, the high refractive index layer 6, the second low refractive index layer 7 and the second protective layer 8 are coated while the ion source is bombarded. This can increase the adhesion and stability between the film layers. The final film has high strength and good stability, and can pass the reliability test of optical thin films for space applications. It has good adaptability to the space environment.

[0048] The reliability and robustness of the reflector were tested. The test items are as follows:

[0049] (1) Adhesion test: The standard polyester tape was tightly attached to the surface of the sample film and pulled vertically along the surface of the film to observe whether the film peeled off. Test result: No peeling off.

[0050] (2) Immersion test: Immerse in water at 45±1℃ for 8 hours and observe whether the film layer peels off. Test result: No peeling.

[0051] (3) Temperature alternation experiment: The film was kept at 50±1℃ for 1 hour, and then at −25±1℃ for 1 hour. This cycle was repeated three times, and the film was observed to see if it peeled off. Test result: No peeling.

[0052] (4) Damp heat test: Keep in an atmosphere with a relative humidity of 95% and a temperature of 45±2℃ for 24 hours and observe whether the film layer peels off. Test result: No peeling.

[0053] The mirror was fabricated using a specific deposition process, which can achieve a reflectivity of more than 98% in the 750~1600nm band, while keeping the phase difference of signal wavelengths of 780±2nm, 842±2nm, 854±2nm, and 1540±2nm within 2 degrees, and also has good adaptability to the space environment.

[0054] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A low-position phase-contrast metallic reflector suitable for space environments, characterized in that, It includes an optical substrate and an adhesive layer, a metal layer, a first protective layer, a first low refractive index layer, a high refractive index layer, a second low refractive index layer, and a second protective layer sequentially deposited on the optical substrate; The optical substrate is silicon; the adhesive layer is nickel-chromium; the metal layer is silver; both the first and second protective layers are made of aluminum oxide; the first low-refractive-index layer is made of silicon dioxide; the second low-refractive-index layer is made of silicon dioxide; and the high-refractive-index layer is made of niobium pentoxide. The thickness of the adhesive layer is 5-10 nm; the thickness of the metal layer is 130-150 nm; the thickness of the first protective layer is 35 nm; the thickness of the second protective layer is 4-6 nm; the thickness of the first low refractive index layer is 115 nm; the thickness of the second low refractive index layer is 125 nm; and the thickness of the high refractive index layer is 160 nm. The working angle of the low-phase metal reflector suitable for space environment is 45 degrees, and the phase difference of the low-phase metal reflector suitable for space environment at signal wavelengths of 780±2nm, 842±2nm, 854±2nm, and 1540±2nm is within 2 degrees.

2. The low-position phase-contrast metal reflector suitable for space environments according to claim 1, characterized in that, The adhesive layer is made of 80Ni20Cr.

3. The low-position phase-contrast metal reflector suitable for space environments according to claim 1, characterized in that, The reflectivity of the low-position phase-contrast metal mirror suitable for space environments in the 750~1600nm range is greater than 98%.

4. A method for manufacturing a low-position phase-contrast metallic mirror suitable for space environments as described in any one of claims 1 to 3, characterized in that, Includes the following steps: The optical substrate is placed in a vacuum coating machine, a vacuum is drawn, and after the vacuum level reaches the set value, ion pre-bombardment treatment is performed. Then, vacuum coating is performed, first depositing the adhesive layer, the metal layer, and the first protective layer in sequence; Then, the ion source is turned on, and while maintaining ion source bombardment, the first low refractive index layer, the high refractive index layer, the second low refractive index layer, and the second protective layer are deposited sequentially. Finally, turn off the ion source and maintain a vacuum state for at least one and a half hours. Then, remove the optical substrate to obtain a low-phase-contrast metal mirror suitable for the space environment.

5. The method for fabricating a low-position phase-contrast metallic mirror suitable for space environments according to claim 4, characterized in that, The deposition rate of the adhesive layer is 0.3~0.5 nm / s; the deposition rate of the metal layer is 0.8~1.2 nm / s; the deposition rate of the first protective layer and the second protective layer is 0.6~0.8 nm / s; the deposition rate of the high refractive index layer is 0.11~0.13 nm / s; and the deposition rate of the first low refractive index layer and the second low refractive index layer is 0.6~0.8 nm / s.

6. The method for fabricating a low-position phase-contrast metallic mirror suitable for space environments according to claim 5, characterized in that, The adhesive layer and the metal layer are deposited using a thermal evaporation deposition method; the first protective layer is deposited using an electron beam evaporation deposition method; the second protective layer, the high refractive index layer, the first low refractive index layer, and the second low refractive index layer are deposited using a radio frequency ion beam assisted electron beam evaporation deposition method.

7. The method for fabricating a low-position phase-contrast metallic mirror suitable for space environments according to claim 6, characterized in that, The vacuum degree of the deposition is 1.0~1.5×10⁻⁶. -3 Pa.

8. The application of the low-phase-contrast metal mirror suitable for space environment as described in any one of claims 1 to 3 in the fields of space laser communication and quantum communication systems.

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