A kind of deviating polarized light splitting prism coating film system, coating method and application thereof

Abstract

The application relates to the technical field of optical coating, and particularly discloses a kind of depolarization spectrometer prism coating film system, coating film method and application thereof, the film system includes 28 layers of dielectric film layers, and the order from inside to outside is MHML MHMLMHMLMHMHMLMHMLMHMHML, wherein the M layer is Al2O3, the H layer is TiO2, and the L layer is SiO2.The application solves the polarization error caused by the current conventional depolarization spectrometer prism and the problem of uneven energy distribution in the multi-stage light path.In addition, the coating film method realizes high consistency between the actual coating process and the theoretical design by fine control of key process parameters, and ensures that the film system performance is stable and up to standard.

Description

Technical Field

[0001] This invention relates to the field of optical coating technology, and specifically discloses a polarization-depolarizing beam splitter coating system, coating method, and its application. Background Technology

[0002] In precision optical systems, depolarization-free beam splitters are core components for achieving polarization-free beam separation and energy distribution, and are widely used in high-end fields such as laser interferometry, multichannel spectral analysis, and quantum communication. These systems have extremely stringent requirements for polarization state consistency and energy distribution uniformity; however, the film system design of existing depolarization-free beam splitters still faces two major technical bottlenecks.

[0003] On the one hand, conventional depolarization beam splitters' film systems cannot completely eliminate polarization differences, leading to polarization errors. Even if some film systems claim to achieve "depolarization," the transmittance and reflectance differences between P-light and S-light may still exceed 3% over a wide incident angle (e.g., 40°–50°) or a wide wavelength range. In high-precision measurement scenarios, this polarization deviation can be converted into phase errors or signal noise, potentially causing nanometer-level measurement errors in laser interferometers, severely affecting system accuracy.

[0004] On the other hand, the problem of uneven energy distribution is particularly prominent in multi-stage beam splitting optical paths (such as multi-channel spectrometers and parallel optical processing systems). Due to the inconsistent absorption characteristics and interface reflection losses of each layer of traditional film systems, the energy attenuation difference of each branch beam can reach 5% to 10% after multiple beam splits. This leads to unbalanced loads on subsequent optical components, with some channels saturated while others have weak signals, reducing the dynamic range and stability of the system.

[0005] In addition, the commonly used materials in existing film systems, such as ZnS and Ag, have poor chemical stability and are prone to oxidation and deterioration with long-term use, which further aggravates polarization error and energy distribution imbalance. At the same time, the coating process parameters are poorly controlled and the film uniformity is insufficient, resulting in large performance dispersion of prisms in the same batch, making it difficult to meet the needs of mass production. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of polarization error caused by conventional depolarization beam splitters in the prior art and uneven energy distribution in multi-stage beam splitting optical paths.

[0007] In a first aspect, the present invention provides a polarization-depolarizing beam splitter coating system comprising 28 dielectric layers, arranged in the order MHMLMHMLMHMLMHMLMHMLMHMLMHML from the inside out, wherein the M layer is Al2O3, the H layer is TiO2, and the L layer is SiO2.

[0008] In this system, TiO2 is used as a high-refractive-index material (H layer), Al2O3 is used as an intermediate layer (M layer), and SiO is used as a low-refractive-index material (L layer). These materials are stacked alternately to form a basic interference film structure, which utilizes the principle of light interference to control light in different polarization states.

[0009] The specific arrangement of the 28 dielectric film layers (MHMLMHMLMHMLMHMLMHMLMHMLMHML) enables light of different polarization states to undergo multiple reflections and interferences within the film system, thereby minimizing the difference between polarization transmittance and reflectance and achieving the effect of polarization elimination.

[0010] In some embodiments of the present invention, the normalized optical thickness of each layer is: 0.9803M 1.761H 1.024M 1.5237L 0.978M 0.7637H 1.0533M 1.282L 1.0348M 0.8512H 1.005M 1.3118L 0.9761M 0.8859H 1.0467M 0.8034H 0.3396M 2.2789L 0.8679M 0.868H 1.0088M 1.3677L 1.123M 0.454H 2.0534M 1.2518H 1.0585M 3.077L.

[0011] Precise design of normalized optical thickness is key to ensuring the depolarization performance of the film system. By rationally setting the thickness of each layer, light with different polarization states can form constructive or destructive interference in the film system, thereby making their transmittance and reflectance tend to be consistent.

[0012] In some embodiments of the present invention, the center wavelength of the film system is 620–640 nm.

[0013] This center wavelength range is suitable for a variety of common optical applications and can meet the needs of effective beam splitting and depolarization within this band.

[0014] Secondly, the present invention provides an application of the above-mentioned depolarizing beam splitter coating system, wherein the depolarizing beam splitter prepared by the coating system has a polarization transmittance difference of <2%, a polarization reflectance difference of <1%, an incident angle of the beam splitter surface of 43-47°, and a wavelength of 622.8-642.8 nm.

[0015] The polarization transmittance difference, |Tp-Ts| ≤ 2%, and the polarization reflectance difference, |Rp-Rs| ≤ 1%, are characteristics that enable this depolarization beam splitter to maintain good depolarization effect over a wide range of incident angles. It is suitable for optical systems with high requirements for polarization characteristics, such as laser interferometers and spectrometers.

[0016] Thirdly, the present invention also provides a coating method for the above-mentioned depolarizing beam splitter coating system, which ensures that the actual coating process closely matches the theoretical design by precisely controlling the process parameters step by step, specifically including the following steps:

[0017] S1. After ultrasonic cleaning and drying of the depolarizing beam splitter, it is loaded into the workpiece rack of the coating machine.

[0018] Ultrasonic cleaning removes nanoscale oil and impurities from the prism surface, preventing substrate defects from causing localized deviations in film thickness and providing clean substrate conditions that meet theoretical design for subsequent uniform film deposition.

[0019] S2. Close the vacuum chamber of the coating machine, start the mechanical pump to draw a vacuum, and then turn on the molecular pump.

[0020] In S2, the vacuum level is strictly controlled at 0.9e. -4 ~1.1e -4 Pa eliminates the scattering interference of residual gas molecules on evaporating particles through a high vacuum environment, ensuring that the deposition path of the film material is consistent with the theoretical simulation and avoiding film looseness or thickness deviation caused by gas collision.

[0021] S3. Raise the temperature to 295-305℃ and maintain it for 30 minutes, then open the oxygen valve.

[0022] In S3, the oxygen flow rate is precisely controlled at 68–72 sccm. The thermal expansion coefficient of the substrate is stabilized by a constant temperature environment. The quantitative oxygen atmosphere ensures that the stoichiometry of oxide films such as TiO2 and Al2O3 is consistent with the theoretical design, avoiding refractive index deviations caused by insufficient or excessive oxidation.

[0023] S4. Adjust the vacuum chamber valve, adjust the anode current to 9.5-10.5A, set the workpiece rack speed to 28-32r / min, start the rotation and perform coating in the order from the inside out. After all film layers have been deposited, stop the coating, cool and remove the workpiece to complete the coating.

[0024] In S4, the vacuum level is controlled at 1.9e. -2 ~2.1e -2 Pa, a stable vacuum environment ensures the stability of the evaporation rate; the matching control of the anolyte current and rotation speed ensures uniform energy output from the evaporation source, resulting in a film deposition rate (TiO2 is Al2O3 is SiO2 is The optical thickness growth rate is strictly matched to the theoretically designed value; the workpiece holder rotation ensures radial uniformity of the film thickness, avoiding thickness deviations caused by excessively rapid local deposition. The coordinated control of these parameters ultimately achieves an actual optical thickness for each film that deviates from the theoretical design value by ≤0.5%.

[0025] This coating method achieves a high degree of consistency between the actual coating process and the theoretical design through precise control of key process parameters, ensuring that the film system performance is stable and meets the standards.

[0026] This coating method is stable and easy to operate, which helps to improve production efficiency and product consistency.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. The anti-polarization beam splitter coating system of the present invention significantly reduces polarization dependence through a specific 28-layer dielectric film structure design and material combination, making the polarization transmittance difference (|Tp-Ts|) ≤ 2% and the polarization reflectance difference (|Rp-Rs|) ≤ 1%. It has excellent anti-polarization effect, effectively solves the polarization error problem, and improves the beam splitter's beam splitting accuracy and stability.

[0029] 2. AlO, TiO and SiO are used as film materials. These materials have good chemical stability, are resistant to oxidation and deliquescence, and have low optical absorption. They also have uniform energy loss in the multi-stage spectral separation process, which solves the problem of uneven energy distribution and improves the service life and environmental adaptability of the film system.

[0030] 3. The coating method provided by this invention achieves high consistency between actual coating parameters and theoretical design values ​​(deviation ≤ 0.5%) through precise control of key parameters such as vacuum degree, temperature, gas flow rate, and deposition rate. This ensures the consistency of core indicators such as film thickness and refractive index, significantly reduces the performance dispersion of products in the same batch, and provides reliable process assurance for large-scale production.

[0031] 4. This depolarizing beam splitter maintains good performance within an incident angle range of 43–47° and an operating wavelength range of 622.8–642.8 nm, making it widely applicable and able to meet the application requirements of various optical systems. Attached Figure Description

[0032] Figure 1 This is a graph showing the results of multiple repeatability tests of TiO2 in Experimental Example 2 of this invention;

[0033] Figure 2 This is a graph showing the results of multiple repeatability tests of SiO2 in Experimental Example 2 of this invention;

[0034] Figure 3 This is a graph showing the results of multiple repeatability tests of Al2O3 in Experimental Example 2 of this invention;

[0035] Figure 4 The figure shows the simulation results of the transmittance characteristics of the depolarization beam splitter in Experiment Example 3 of the present invention.

[0036] Figure 5The figure shows the simulation results of the transmittance characteristics of the depolarization beam splitter in multiple sets of experiments in Experiment Example 4 of this invention.

[0037] Figure 6 The measured transmittance curve of the depolarization beam splitter in Experimental Example 5 of this invention is shown. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0039] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0040] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0041] In the description of the embodiments of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "horizontal," "inner," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product of the invention is in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0042] Furthermore, the use of terms such as "horizontal" does not imply that the component must be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to vertical, and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0043] In the description of the embodiments of the present invention, "multiple" means at least two.

[0044] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0045] Example 1

[0046] This embodiment provides a depolarizing beam splitter coating system, which has 28 dielectric layers arranged in the following order from the inside out: MHMLMHMLMHMLMHMLMHMLMHMLMHML, where layer M is Al2O3, layer H is TiO2, and layer L is SiO2. The normalized optical thickness of each layer is: 0.9803M1.761H1.024M1.5237L0.978M0.7637H1.0533M1. 282L1.0348M0.8512H1.005M1.3118L0.9761M0.8859H1.0467M0.8034H0.3396M2.2789L0.8679M0.868H1.0088M1.3677L1.123M0.454H2.0534M1.2518H1.0585M3.077L, with a center wavelength of 620–640 nm.

[0047] This embodiment also provides a coating method for the above-mentioned depolarizing beam splitter coating system, including the following steps:

[0048] S1. After ultrasonic cleaning and drying of the depolarizing beam splitter, it is loaded into the workpiece rack of the coating machine.

[0049] S2. Close the vacuum chamber of the coating machine, start the mechanical pump to evacuate the vacuum, and then start the molecular pump to achieve a vacuum level of 1.0 e. -4 Pa;

[0050] S3. Raise the temperature to 300℃ and maintain it for 30 minutes, then open the oxygen valve and control the oxygen flow rate to 70 sccm.

[0051] S4. Adjust the vacuum chamber valve to achieve a vacuum level of 2.0 e. -2 Pa, adjust the anode current to 10A, set the workpiece holder speed to 30r / min, start the rotation and perform coating in an inside-out sequence. The coating rate of TiO2 during coating is The coating rate of Al2O3 is The SiO2 coating rate is After all film layers have been deposited, the coating process is stopped, and the film is removed after cooling to complete the coating process.

[0052] Experimental Example 1

[0053] Repeatability tests were performed on TiO2, SiO2, and Al2O3, with all three materials undergoing single-layer coating. The coating thicknesses were: TiO2: 276.1 nm, SiO2: 436.4 nm, and Al2O3: 263.3 nm, respectively. The coating process used was the same as in Example 1, with the coating rate for TiO2 being [missing information]. The coating rate of Al2O3 is The SiO2 coating rate is Calculate tool factors and repeatability errors, such as Figure 1-3 As shown.

[0054] in Figure 1 The results of repeatability tests of TiO2 using the same coating process and coating thickness are presented. The horizontal axis of the figure represents wavelength, and the vertical axis represents transmittance percentage. The multiple curves in the figure represent the reflectance of multiple repeatability tests. The results show that the curves of multiple tests highly overlap within the target wavelength range (620nm~640nm), indicating that the film performance of TiO2 in this wavelength range is relatively repeatable. The optical constants of the material are less sensitive to process fluctuations in this wavelength range, and the film layers of multiple coatings are more likely to remain consistent.

[0055] Figure 2 The results of repeatability tests of SiO2 using the same coating process and coating thickness are presented. The horizontal axis of the figure represents wavelength, and the vertical axis represents transmittance percentage. The multiple curves in the figure represent the reflectance of multiple repeatability tests. The results show that the curves of multiple tests highly overlap within the target wavelength range (620nm~640nm), indicating that the SiO2 film performance has good repeatability within this wavelength range. The optical constants of the material are less sensitive to process fluctuations within this wavelength range, and the film layers of multiple coatings are more likely to remain consistent.

[0056] Figure 3 The results of repeatability tests of Al2O3 using the same coating process and coating thickness are presented. The horizontal axis of the figure represents wavelength, and the vertical axis represents transmittance percentage. The multiple curves in the figure represent the reflectance of multiple repeatability tests. The results show that the curves of multiple tests highly overlap within the target wavelength range (620nm~640nm), indicating that the film performance of Al2O3 in this wavelength range is good repeatability. The optical constants of the material are less sensitive to process fluctuations in this wavelength range, and the film layers of multiple coatings are more likely to remain consistent.

[0057] Experimental Example 2

[0058] The optical simulation software TFCalc was used for simulation analysis. Following the design of the film system in Example 1, key input parameters such as "film system structure, material, thickness, and incident conditions" were used to plot the simulation results of the transmittance characteristics of the depolarizing beam splitter. Figure 4 As shown.

[0059] In the diagram: Illuminant: WHITE: Indicates that white light is used as the light source. Angle: 45.0 (deg): Indicates an incident angle of 45°. Substrate: JGS1, Exit: JGS1: Indicates that both the substrate material and the material through which the emitted light passes are JGS1. Polarization: Ave (black curve), P (blue curve), S (red curve): Ave represents the average transmittance (Tave%) curve, which is the average result calculated after considering the transmittance of S-light and P-light, used to measure the overall light transmittance of the depolarizing beam splitter. P represents the transmittance curve of P-light (parallel polarized light, light whose vibration direction is parallel to the incident plane). S represents the transmittance curve of S-light (perpendicular polarized light, light whose vibration direction is perpendicular to the incident plane). FirstSurface: Front: Indicates that the simulation analysis is of the optical properties of the front surface of the film.

[0060] The horizontal axis (X-axis) represents the wavelength of light, ranging from 600nm to 660nm. The vertical axis (Y-axis) represents the transmittance percentage, ranging from 0% to 70%, reflecting the ratio of the emitted light intensity to the incident light intensity after light of different wavelengths passes through the depolarizing beam splitter.

[0061] from Figure 4 As can be seen, using the film system of this application, the P and S curves almost overlap within the center wavelength range of 620-640nm. This indicates that within this key wavelength range, the transmittance difference between S and P light by the depolarizing beam splitter is minimal, demonstrating excellent depolarization performance. This shows that the film system design can effectively eliminate the transmittance difference of polarized light, allowing light of different polarization states to pass through the film layer with similar efficiency.

[0062] The average transmittance curve lies between the S-ray and P-ray curves, and is relatively stable in the central wavelength range of 620-640nm, with the transmittance remaining approximately stable at around 50%. This indicates that within the target wavelength range, the depolarizing beam splitter can maintain a relatively stable average transmittance, meeting the requirements for transmittance stability and providing support for ensuring stable optical signal transmission in practical applications.

[0063] Experimental Example 3

[0064] The optical simulation software TFCalc was used for simulation analysis. Using the film system designed in Example 1 as input parameters, a simulated curve of the transmittance of the depolarized beam splitter as a function of wavelength was plotted to demonstrate the performance of the film transmittance in different wavelength ranges (600-660 nm) under different polarization states (S-ray and P-ray). The results are as follows: Figure 5 As shown.

[0065] In the figure: Horizontal axis (X-axis): Wavelength (nm), representing wavelength, ranging from 600nm to 660nm. Vertical axis (Y-axis): Transmittance (%), representing transmittance percentage, ranging from 0% to 70%, reflecting the proportion of light intensity remaining after light passes through the film layer.

[0066] Angle: 45.0 (deg): indicates an incident angle of 45°. S (red curve) and P (blue curve): represent the transmittance curves of S-ray (vertically polarized light, vibration direction perpendicular to the incident plane) and P-ray (parallel polarized light, vibration direction parallel to the incident plane), respectively.

[0067] From the appendix Figure 5 It can be seen that the transmittance curves of S-rays and P-rays almost completely overlap within the 620-640nm range, with the transmittance remaining stable at around 50%. This indicates that the transmittance difference between S-rays and P-rays is extremely small within this wavelength range, demonstrating the "depolarization" effect of the film system. Furthermore, within the target operating wavelength range, the transmittance of the film system for S-rays and P-rays exhibits excellent consistency, achieving the core functions of uniform beam splitting and depolarization.

[0068] Figure 5 Multiple simulation results show that the transmittance curves of S-light and P-light almost completely overlap in the range of 620-640nm, and the transmittance is stable at around 50%. This indicates that the theoretical consistency of the film system design in this application is strong, and the depolarization and spectral splitting performance is stable under different simulation scenarios. At the same time, the yield rate is high during mass production, the performance fluctuation of each batch of film is small, and most products can meet the qualified standard of "|Tp-Ts|≤2% and stable transmittance".

[0069] Experiment Example 4

[0070] A coating experiment was conducted according to the film system design and coating method described in Example 1, and the transmittance of the coated prism was tested using an ellipsometer. During the test, the wavelength range of the incident light was set to 610nm-650nm, and measurements were taken for different polarization states (S-ray and P-ray). The transmittance data corresponding to different wavelengths were recorded, and the results are as follows: Figure 6 As shown.

[0071] In the figure: Horizontal axis (X-axis): Wavelength (nm), representing wavelength, ranging from 610nm to 650nm. Vertical axis (Y-axis): Transmittance (%), representing transmittance percentage, ranging from 0% to 70%, reflecting the proportion of light intensity remaining after light passes through the film layer.

[0072] from Figure 6 It can be concluded that within the center wavelength range of 620-640nm, the transmittance of the depolarization beam splitter for light of different polarization states is relatively small, demonstrating good depolarization performance. At the same time, the transmittance curve is smooth and the value is relatively stable. This indicates that the depolarization beam splitter can maintain stable transmittance within the target operating wavelength range, meeting the requirements for light transmittance stability in practical applications and providing stable optical signal transmission guarantee for subsequent optical systems (such as laser interferometry, spectral analysis, etc.).

[0073] Experimental Example 5

[0074] Following the film system design and coating method of Example 1, multiple coating operations were performed. After each prism was produced, its key performance indicators were tested: Ts%: the percentage of transmittance of S-beams (polarized light perpendicular to the incident plane), i.e., the proportion of residual light intensity to incident light intensity after S-beams pass through the prism; Tp%: the percentage of transmittance of P-beams (polarized light parallel to the incident plane), i.e., the proportion of residual light intensity to incident light intensity after P-beams pass through the prism; and Tave%: the average of Ts% and Tp% was calculated, i.e., Tave% = (Ts% + Tp%) / 2, to measure the overall light transmittance of the depolarizing beam splitter prism; the polarization transmittance difference |Tp-Ts| was calculated to measure the depolarization effect of the prism. The results are shown in Table 1:

[0075] Table 1. Prism data for multiple coatings according to the film system design and coating method of Example 1.

[0076] 620 49.8187 49.5238 50.1136 0.5898 621 49.7139 49.424 50.0038 0.5798 622 49.619 49.3306 49.9074 0.5768 623 49.5332 49.2437 49.8228 0.5791 624 49.4561 49.1632 49.7489 0.5857 625 49.3869 49.0891 49.6848 0.5957 626 49.3254 49.0213 49.6295 0.6082 627 49.2712 48.9598 49.5825 0.6227 628 49.2239 48.9045 49.5434 0.6389 629 49.1834 48.855 49.5118 0.6568 630 49.1496 48.8114 49.4879 0.6765 63l 49.1224 48.7733 49.4716 0.6983 632 49.102 48.7406 49.4633 0.7227 633 49.0884 48.7131 49.4636 0.7505 634 49.0818 48.6905 49.4732 0.7827 635 49.0827 48.6727 49.4927 0.82 636 49.0914 48.6594 49.5234 O.864 637 49.1084 48.6507 49.5662 0.9155 638 49.1343 48.6462 49.6224 0.9762 639 49.1698 48.6461 49.6934 1.0473 640 49.2155 48.6503 49.7807 1.1304 641 49.2723 48.6588 49.8858 1.227 642 49.3411 48.6718 50.0103 1.3385 643 49.4227 48.6894 50.156 1.4666 644 49.5183 48.712 50.3246 1.6126 645 49.6289 48.7398 50.5179 1.7781

[0077] The data in Table 1 shows that the polarization transmittance difference |Tp-Ts| in multiple experiments was ≤2%, indicating that according to the film system design and coating method of this application, the transmittance of P-light and S-light is almost the same when passing through the prism within the target wavelength range. The two polarization states of light will not produce polarization bias due to the transmittance difference, thus achieving the purpose of eliminating polarization difference in the prism. This can avoid introducing nanoscale measurement errors or signal noise in scenarios such as laser interferometry and quantum communication. At the same time, the Tave% in multiple experiments remained basically stable between 48% and 50%, indicating that the film system design can ensure high and stable light transmission efficiency while eliminating polarization, meeting the requirements of sufficient light intensity in scenarios such as laser interferometry and spectral analysis.

[0078] In summary, the embodiments of the present invention have the following beneficial effects: they effectively solve the polarization error and uneven energy distribution problems in multi-stage beam splitting paths of conventional depolarizing beam splitters; and through precise control of the coating process, the actual parameters closely match the theoretical design, improving the stability and consistency of the film system, making it suitable for mass production. This depolarizing beam splitter has broad application prospects in various high-precision optical systems and can meet the stringent requirements of high-end optical systems for beam splitting and depolarization.

[0079] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A depolarization beam splitter coating system, characterized in that, It consists of 28 dielectric film layers, arranged from the inside out as MHMLMHMLMHMLMHMLMHMLMHMLMHML, where the M layer is Al2O3, the H layer is TiO2, and the L layer is SiO2. The normalized optical thickness of each layer is: 0.9803M 1.761H 1.024M 1.5237L 0.978M 0.7637H 1.0533M 1.282L 1.0348M 0.8512H 1.005M 1.3118L 0.9761M 0.8859H 1.0467M 0.8034H 0.3396M 2.2789L 0.8679M 0.868H 1.0088M 1.3677L 1.123M 0.454H 2.0534M 1.2518H 1.0585M 3.077L.

2. The depolarization beam splitter coating system according to claim 1, characterized in that, Its central wavelength is 632.8±15nm.

3. An application of the depolarizing beam splitter coating system as described in any one of claims 1 to 2, characterized in that, The polarization-splitting prism prepared from the aforementioned polarization-splitting prism coating system has a polarization transmittance difference |Tp-Ts| ≤ 2%, a polarization reflectance difference |Rp-Rs| ≤ 1%, a beam splitting surface incident angle of 43~47°, and a wavelength of 632.8±15nm.

4. A coating method for a depolarizing beam splitter coating system as described in any one of claims 1 to 2, characterized in that, Includes the following steps: S1. After ultrasonic cleaning and drying of the depolarizing beam splitter, it is loaded into the workpiece rack of the coating machine. S2. Close the vacuum chamber of the coating machine, start the mechanical pump to draw a vacuum, and then turn on the molecular pump to draw a high vacuum. S3. Raise the temperature to 295~305℃ and maintain it for 30 minutes; S4. Open the oxygen valve to adjust the vacuum, adjust the anode current to 9.5~10.5A, set the workpiece rack speed to 28~32r / min, start the rotation and perform coating according to the film system sequence. After all film layers have been deposited, stop the coating, cool and remove the workpiece to complete the coating.

5. The coating method according to claim 4, characterized in that, In S2, the vacuum level is 0.9e. -4 ~1.1e - 4 Pa.

6. The coating method according to claim 4, characterized in that, In S3, the oxygen flow rate is 68~72 sccm.

7. The coating method according to claim 4, characterized in that, In S4, the vacuum level is 1.9e. -2 ~2.1e - 2 Pa.

8. The coating method according to claim 4, characterized in that, In step S4, the deposition rate of TiO2 is 1.4~1.6 Å / s, the deposition rate of Al2O3 is 1.9~2.1 Å / s, and the deposition rate of SiO2 is 3.9~4.1 Å / s.

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