Depolarization film of beam splitter prism, preparation method of depolarization film, beam splitter prism and preparation method of beam splitter prism

Abstract

The invention belongs to the technical field of optical beam splitting elements, and particularly relates to a beam splitter prism depolarization film, a preparation method thereof, a beam splitter prism and a preparation method thereof. The beam splitter prism depolarization film provided by the invention comprises a first SiO2 film layer, a first Ta2O5 film layer, a first Al2O3 film layer, a metal silver layer, a second Al2O3 film layer, a second Ta2O5 film layer and a second SiO2 film layer which are sequentially laminated, wherein the first SiO2 film layer is in contact with the surface of a substrate. According to the beam splitter prism depolarization film provided by the invention, the number of film layers is obviously reduced, the total film thickness is obviously reduced, the film layer thickness is greatly optimized, the film material consumption cost and the equipment energy consumption are reduced, and the processing efficiency is greatly improved; meanwhile, the risks of film layer breakage and electroplated layer falling are reduced; the film layer contains less thin layers, the equipment monitoring is more accurate, the actual effect is closer to the design, the achievable specification is more strict, and the practical value is excellent.

Description

Technical Field

[0001] This invention belongs to the field of optical beam splitting element technology, specifically relating to the depolarization thin film of a beam splitting prism and its preparation method, and the beam splitting prism and its preparation method. Background Technology

[0002] A nonpolarized beam splitter (NPBS) is an optical beam splitter used to maintain the polarization state of incident light, widely used in interferometric analysis instruments, life science instruments, and laser systems. Prism materials typically include BK7, K9, or B270, and right-angle prisms are available in sizes with side lengths of approximately 5mm, 10mm, 12.7mm, and 25.4mm. Nonpolarized beam splitters with beveled surfaces often employ alternating layers of three dielectric materials: high-refractive-index titanium pentoxide (Ti3O5), low-refractive-index silicon dioxide (SiO2), and medium-refractive-index aluminum oxide (Al2O3). This film system has the following drawbacks: 1. The film has a high number of layers, typically around 30 or more, with a total film thickness of approximately 2-3 μm. This thickness directly leads to wasted coating material and excessively long deposition time, resulting in wasted electricity. 2. Thicker films are more prone to cracking and other reliability issues. 3. The more layers there are, the higher the probability of thin layers (generally defined as those less than 10 nm thick). Controlling thin layers is more difficult; the more thin layers there are, the greater the accumulated control error, making overall control more challenging and potentially leading to significant discrepancies between design and actual results. Summary of the Invention

[0003] The purpose of this invention is to provide a depolarization film for a beam splitter prism and its preparation method, as well as a beam splitter prism and its preparation method. The depolarization film for a beam splitter prism provided by this invention significantly reduces the number of film layers and the total film thickness, greatly optimizing the film thickness, saving on film material costs and equipment energy consumption, and significantly improving processing efficiency; at the same time, it reduces the risk of film layer cracking and electroplating layer peeling; the film contains relatively fewer thin layers, making equipment monitoring more precise, and the actual effect is closer to the design, that is, it can achieve more stringent specifications and has excellent practical value.

[0004] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a beam splitter depolarization film, comprising a first SiO2 film layer, a first Ta2O5 film layer, a first Al2O3 film layer, a silver layer, a second Al2O3 film layer, a second Ta2O5 film layer, and a second SiO2 film layer stacked sequentially, wherein the first SiO2 film layer is in contact with the surface of a substrate; the thickness of the beam splitter depolarization film is 190-300 nm under 400-700 nm wavelength conditions; and the thickness of the beam splitter depolarization film is 300-400 nm under 700-1100 nm wavelength conditions.

[0005] Preferably, under the 400~700nm wavelength range: the thickness of the first SiO2 film is 70~90nm, the thickness of the first Ta2O5 film is 15~25nm, the thickness of the first Al2O3 film is 40~60nm, the thickness of the metallic silver layer is 6.2~8.8nm, the thickness of the second Al2O3 film is 10~20nm, the thickness of the second Ta2O5 film is 10~25nm, and the thickness of the second SiO2 film is 45~60nm.

[0006] Preferably, under the 700~1100nm wavelength range: the thickness of the first SiO2 film is 30~37nm, the thickness of the first Ta2O5 film is 65~79nm, the thickness of the first Al2O3 film is 30~36nm, the thickness of the silver layer is 5~8nm, the thickness of the second Al2O3 film is 31~38nm, the thickness of the second Ta2O5 film is 35~44nm, and the thickness of the second SiO2 film is 130~139nm.

[0007] This invention provides a method for preparing the polarization-depolarizing thin film of the beam-splitting prism described above, comprising the following steps: Based on the film material, optical band, and optical properties of the depolarization film of the beam splitter, film system design software is used to design the film system and obtain the film system design results of the depolarization film of the beam splitter. A first SiO2 film layer, a first Ta2O5 film layer, a first Al2O3 film layer, a silver film layer, a second Al2O3 film layer, a second Ta2O5 film layer, and a second SiO2 film layer are sequentially deposited on the surface of the substrate according to the film system design results to obtain the polarization-depolarizing thin film of the beam-splitting prism. A first waiting time is set after depositing the first Al2O3 film layer and before depositing the silver film layer, and a second waiting time is set after depositing the silver film layer and before depositing the second Al2O3 film layer. The first waiting time is ≥600s, and the second waiting time is ≥600s.

[0008] Preferably, the coating is performed using a vacuum evaporation coating method; The deposition conditions include: initial vacuum degree ≤ 1.0E-3Pa; substrate temperature 0~40℃; film formation rates of the first SiO2 film layer and the second SiO2 film layer independently 0.3~0.7nm / s, film formation rates of the first Ta2O5 film layer and the second Ta2O5 film layer independently 0.2~0.3nm / s, film formation rates of the first Al2O3 film layer and the second Al2O3 film layer independently 0.2~0.4nm / s, and film formation rate of the silver layer 0.1~0.2nm / s.

[0009] Preferably, before the plating, the substrate is further subjected to ion source cleaning, wherein the vacuum degree of the ion source cleaning is ≤1.0E-3Pa, the time is 2~5min, and the temperature of the substrate during the ion source cleaning is 0~40℃.

[0010] Preferably, the substrate is made of BK7, K9 or B270.

[0011] The present invention provides a beam splitter prism, wherein an anti-polarization film is disposed inside the beam splitter prism, and the anti-polarization film is the beam splitter anti-polarization film described in the above technical solution or the beam splitter anti-polarization film prepared by the preparation method described in the above technical solution.

[0012] Preferably, the outer wall of the beam splitter is further provided with an anti-reflection film, which includes alternating layers of Ti3O5 monolayer film and SiO2 monolayer film, and the Ti3O5 monolayer film is in contact with the outer wall of the beam splitter.

[0013] This invention provides a method for preparing the beam-splitting prism described above, comprising the following steps: An antireflective coating is deposited on a first part substrate and a second part substrate; then, an antipolarization film is deposited on the first part substrate according to the preparation method described above; finally, the first part substrate and the second part substrate are bonded together to obtain the beam splitter prism.

[0014] This invention provides a beam splitter depolarization film, comprising a first SiO2 film, a first Ta2O5 film, a first Al2O3 film, a silver layer, a second Al2O3 film, a second Ta2O5 film, and a second SiO2 film, stacked sequentially. The first SiO2 film is in contact with the surface of a substrate. The thickness of the beam splitter depolarization film is 190-300 nm under 400-700 nm wavelength conditions and 300-400 nm under 700-1100 nm wavelength conditions. This invention introduces a silver layer into the depolarization film structure, achieving a significant reduction in the number and thickness of the beam splitter depolarization film through silver doping of the dielectric film. Compared with the prior art, the present invention has the following beneficial effects: (1) The number of film layers is significantly reduced (<10 layers), the total film thickness is significantly reduced, and it can be achieved within about 400nm, which greatly optimizes the film thickness, saves the cost of film material and equipment energy consumption, and greatly improves the processing efficiency. (2) The film layer is significantly thinner, which reduces the risk of film layer cracking and electroplating layer peeling off. (3) With the reduction of the number of layers and thickness, the film layer contains relatively fewer thin layers, the equipment monitoring is more accurate, the actual effect is closer to the design, that is, the specifications that can be achieved are more stringent. Conventional depolarization films can achieve an average transmittance (Tabs) of 90±5%, an absolute average reflectance (Rabs) of 10±5%, an absolute difference (|Ts-Tp|) between s-polarized light transmittance (Ts) and p-polarized light transmittance (Tp) of <10%, and an absolute difference (|Rs-Rp|) between s-polarized light reflectance (Rs) and p-polarized light reflectance (Rp) of <10%. The depolarization film provided by this invention meets the specifications: Tabs=90±5%, Rabs=10±5%, |Ts-Tp|<3%, |Rs-Rp|<3%. The optical performance of the depolarization film provided by this invention is significantly better than that of conventional depolarization films. Attached Figure Description

[0015] Figure 1 The isosceles right-angle prisms A and A1 used in this invention; Figure 2 This is the design curve of the 400~700nm antireflection film in Comparative Example 1 of the present invention; Figure 3 The actual deposition curve of the antireflection film at 400~700nm in Comparative Example 1 of this invention; Figure 4 The polarization-depolarization design curve of the dielectric film in Comparative Example 1 of this invention; Figure 5 This is a graph showing the actual depolarization deposition curve of the dielectric film in Comparative Example 1 of the present invention; Figure 6 This is a graph showing the polarization deviation of the dielectric film in Comparative Example 1 of the present invention. Figure 7This is a polarization depolarization design curve of the silver-doped dielectric film in Embodiment 1 of the present invention; Figure 8 This is a polarization-free deposition curve of the silver-doped dielectric film in Embodiment 1 of the present invention. Figure 9 This is a graph showing the polarization deviation of the silver-doped dielectric film in Embodiment 1 of the present invention. Figure 10 This is a polarization depolarization design curve of the 700~1100nm silver-doped dielectric film in Embodiment 2 of the present invention; Figure 11 This is the actual depolarization deposition curve of the 700~1100nm silver-doped dielectric film in Example 2 of the present invention; Figure 12 This is the depolarization deviation curve of the 700~1100nm silver-doped dielectric film in Embodiment 2 of the present invention. Detailed Implementation

[0016] This invention provides a beam splitter depolarization film, comprising a first SiO2 film layer, a first Ta2O5 film layer, a first Al2O3 film layer, a silver layer, a second Al2O3 film layer, a second Ta2O5 film layer, and a second SiO2 film layer stacked sequentially, wherein the first SiO2 film layer is in contact with the surface of a substrate; the thickness of the beam splitter depolarization film is 190-300 nm under 400-700 nm wavelength conditions; and the thickness of the beam splitter depolarization film is 300-400 nm under 700-1100 nm wavelength conditions.

[0017] The beam splitter depolarization film provided by this invention significantly reduces the number of film layers (<10 layers) and the total film thickness. Therefore, the beam splitter depolarization film provided by this invention is also a method for reducing the thickness of beam splitter depolarization films. This invention uses a film structure in which a first SiO2 layer, a first Ta2O5 film layer, a first Al2O3 layer, a silver layer, a second Al2O3 film layer, a second Ta2O5 film layer, and a second SiO2 film layer are sequentially stacked, with the first SiO2 layer in contact with the substrate. This significantly reduces the number of film layers (<10 layers) and the total film thickness of the beam splitter depolarization film.

[0018] In this invention, under the 400-700nm wavelength range: the thickness of the first SiO2 film is preferably 70-90nm, and in the embodiment it can be 81.15±5nm. The thickness of the first Ta2O5 film is preferably 15-25nm, and in the embodiment it can be 19.01±2nm. The thickness of the first Al2O3 film is preferably 40-60nm, and in the embodiment it can be 53.37±3nm. The thickness of the metallic silver layer is preferably 6.2-8.8nm, and in the embodiment it can be 7.65±1nm. The thickness of the second Al2O3 film is preferably 10-20nm, and in the embodiment it can be 16.19±2nm. The thickness of the second Ta2O5 film is preferably 10-25nm, and in the embodiment it can be 19.26±2nm. The thickness of the second SiO2 film is preferably 45-60nm, more preferably 45-55nm, and in the embodiment it can be 48.74±3nm.

[0019] In this invention, under the 700~1100nm wavelength range: the thickness of the first SiO2 film is preferably 30~39nm, and in the embodiment it can be 35.27±3nm. The thickness of the first Ta2O5 film is preferably 63~79nm, and in the embodiment it can be 68.7±5nm. The thickness of the first Al2O3 film is preferably 28~36nm, and in the embodiment it can be 31.98±3nm. The thickness of the metallic silver layer is preferably 5~8nm, and in the embodiment it can be 6.95±1nm. The thickness of the second Al2O3 film is preferably 31~40nm, and in the embodiment it can be 36.18±3nm. The thickness of the second Ta2O5 film is preferably 35~45nm, and in the embodiment it can be 41.79±3nm. The thickness of the second SiO2 film is preferably 126~139nm, and in the embodiment it can be 131.45±5nm.

[0020] This invention provides a method for preparing the polarization-depolarizing thin film of the beam-splitting prism described above, comprising the following steps: Based on the film material, optical band, and optical properties of the depolarization film of the beam splitter, film system design software is used to design the film system and obtain the film system design results of the depolarization film of the beam splitter. A first SiO2 film layer, a first Ta2O5 film layer, a first Al2O3 film layer, a silver film layer, a second Al2O3 film layer, a second Ta2O5 film layer, and a second SiO2 film layer are sequentially deposited on the surface of the substrate according to the film system design results to obtain the polarization-depolarizing thin film of the beam-splitting prism. A first waiting time is set after depositing the first Al2O3 film layer and before depositing the silver film layer, and a second waiting time is set after depositing the silver film layer and before depositing the second Al2O3 film layer. The first waiting time is ≥600s, and the second waiting time is ≥600s.

[0021] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0022] This invention, based on the film material, optical band, and optical properties of the beam-splitting prism depolarization film, employs film system design software to design the film system, obtaining the design results of the beam-splitting prism depolarization film. In this invention, the optical band can be either 400~700nm or 700~1100nm. The optical properties include Tabs, Rabs, the ratio of transmitted light intensity to reflected light intensity (transmission-to-reflection ratio T:R), |Ts-Tp|, and |Rs-Rp|. The film system design software includes TFCalc optical thin film design software or Essential Macleod optical thin film design software. The design results of the beam-splitting prism depolarization film include the thickness of each layer and the total thickness.

[0023] After obtaining the film system design results of the beam splitter depolarization film, the present invention sequentially deposits a first SiO2 film layer, a first Ta2O5 film layer, a first Al2O3 film layer, a silver film layer, a second Al2O3 film layer, a second Ta2O5 film layer, and a second SiO2 film layer on the surface of the substrate according to the film system design results to obtain the beam splitter depolarization film. A first waiting time is set after depositing the first Al2O3 film layer and before depositing the silver film layer, and a second waiting time is set after depositing the silver film layer and before depositing the second Al2O3 film layer. The first waiting time is ≥600s, and the second waiting time is ≥600s.

[0024] In this invention, the substrate material preferably includes BK7, K9 or B270.

[0025] In this invention, prior to the plating process, the invention preferably includes ion source cleaning of the substrate. Preferably, the substrate is placed in a collar, and the collar containing the substrate is placed on a perforated umbrella-shaped fixture on the machine; then ion source cleaning is performed. This invention preferably improves the adhesion of the antipolarizing film of the beam splitter prism on the substrate surface through ion source cleaning. The vacuum degree of the ion source cleaning is preferably ≤1.0E-3Pa, the time is preferably 2~5 min, more preferably 3 min; the temperature of the substrate during ion source cleaning is preferably 0~40℃. In this invention, the voltage of the ion source cleaning is preferably 700~800V; the current is preferably 700~800mA. The gas used for ion source cleaning is preferably oxygen and argon, and the flow rate ratio of oxygen to argon is preferably 40~60:5~8. The flow rate of the oxygen is preferably 40~60 sccm. The argon includes a first argon and a second argon, the flow rate of the first argon (ion source argon) is preferably 0 sccm, and the flow rate of the second argon (neutralizer argon) is preferably 5~8 sccm.

[0026] In this invention, the plating is performed after the ion source cleaning is completed.

[0027] In this invention, the deposition is preferably performed using a vacuum evaporation deposition method. The polarization-reducing thin film of the beam-splitting prism is deposited using a vacuum evaporation deposition machine.

[0028] In this invention, during the plating process, the substrate is preferably placed within a collar, and the collar containing the substrate is placed on a perforated umbrella-shaped fixture on the machine. The plating conditions preferably include: an initial vacuum degree preferably ≤1.0E-3 Pa; a substrate temperature preferably 0~40℃; a film formation rate of 0.3~0.7 nm / s for the first and second SiO2 films, which can be 0.4 nm / s in the embodiment; a film formation rate of 0.2~0.3 nm / s for the first and second Ta2O5 films, which can be 0.2 nm / s in the embodiment; a film formation rate of 0.2~0.4 nm / s for the first and second Al2O3 films, which can be 0.3 nm / s in the embodiment; and a film formation rate of 0.1~0.2 nm / s for the silver layer, which can be 0.15 nm / s in the embodiment.

[0029] In this invention, the ion source for depositing the first SiO2 film layer and the second SiO2 film layer is preferably SiO2; the voltage is preferably 800~850V; the current is preferably 800~850mA; the gas used is preferably oxygen and argon, and the flow rate ratio of the oxygen and argon is preferably 40:8. The flow rate of the oxygen is preferably 40 sccm, and the argon includes a first argon and a second argon, the flow rate of the first argon (ion source argon) is preferably 0 sccm, and the flow rate of the second argon (neutralizer argon) is preferably 8 sccm.

[0030] In this invention, the ion source for the first Ta2O5 film layer and the second Ta2O5 film layer is preferably Ti3O5; the voltage is preferably 800~850V; the current is preferably 800~850mA; the gas used is preferably oxygen and argon, and the flow rate ratio of oxygen to argon is preferably 60:16; the flow rate of oxygen is preferably 60sccm, and the argon includes a first argon and a second argon, the flow rate of the first argon (ion source argon) is preferably 8sccm, and the flow rate of the second argon (neutralizer argon) is preferably 8sccm.

[0031] In this invention, the ion source for depositing the first Al2O3 film and the second Al2O3 film is preferably Al2O3; the ion source is not turned on when depositing the first Al2O3 film and the second Al2O3 film (i.e., the corresponding parameters are: voltage 0, current 0); the gas used is preferably oxygen and argon, and the flow rate ratio of the oxygen and argon is preferably 40:8. The flow rate of the oxygen is preferably 40 sccm, and the argon includes a first argon and a second argon, the flow rate of the first argon (ion source argon) is preferably 0 sccm, and the flow rate of the second argon (neutralizer argon) is preferably 8 sccm.

[0032] In this invention, a first waiting time is set after the first Al2O3 film layer is deposited and before the silver metal layer is deposited. The first waiting time is ≥600s, preferably 600~900s (in order to prevent impurity gases from interfering with the deposition of the metal layer).

[0033] In this invention, the ion source for depositing the silver layer is preferably elemental Ag. The ion source is not turned on during the silver layer deposition (i.e., the corresponding parameters are: voltage 0, current 0); the gas used is preferably argon, which includes a first argon gas and a second argon gas. The flow rate of the first argon gas (ion source argon gas) is preferably 60 sccm, and the flow rate of the second argon gas (neutralizer argon gas) is preferably 8 sccm.

[0034] The present invention does not turn on the ion source when depositing the first Al2O3 film, the second Al2O3 film, and the metallic silver layer, which can effectively prevent interference with the metallic silver layer and avoid inaccurate monitoring during the film deposition process.

[0035] In this invention, a second waiting time is set after the silver metal layer is deposited and before the second Al2O3 film layer is deposited. The second waiting time is ≥600s, preferably 600~900s (in order to prevent impurity gases from interfering with the depositing of the metal layer).

[0036] This invention sets a first waiting time and a second waiting time to prevent the Ag layer from being oxidized. From an efficiency and effectiveness perspective, a waiting time of 600-900 seconds is optimal, preventing oxidation while maintaining efficiency. When the waiting time is less than 600 seconds, there is a risk of impurities affecting the process. When the waiting time is greater than 900 seconds, although impurities can be well controlled, efficiency is affected, which is detrimental to industrial production and wastes energy.

[0037] The present invention provides a beam splitter prism, wherein an anti-polarization film is disposed inside the beam splitter prism, and the anti-polarization film is the beam splitter anti-polarization film described in the above technical solution or the beam splitter anti-polarization film prepared by the preparation method described in the above technical solution.

[0038] In this invention, an antireflection coating is further provided on the outer wall of the beam splitter. The antireflection coating comprises alternating layers of Ti3O5 monolayer and SiO2 monolayer, with the Ti3O5 monolayer in contact with the outer wall of the beam splitter. In this invention, the function of the antireflection coating is to reduce the reflectivity of the corresponding surface and increase the transmittance. The antireflection coating has an average reflectivity (Rave) of <0.5% within the specified wavelength range. The antireflection coating can be achieved by alternating stacking 5-7 layers of high-refractive-index titanium pentoxide (Ti3O5) and low-refractive-index silicon dioxide (SiO2).

[0039] This invention provides a method for preparing the beam-splitting prism described above, comprising the following steps: An antireflective coating is deposited on a first part substrate and a second part substrate; then, an antipolarization film is deposited on the first part substrate according to the preparation method described above; finally, the first part substrate and the second part substrate are bonded together to obtain the beam splitter prism.

[0040] In this invention, the first part of the base (denoted as A) and the second part of the base (denoted as A1) are the same isosceles right-angle prism (e.g., Figure 1 (As shown). In this invention, the right-angled side A=A1 of the isosceles right-angled prism can be 5mm, 10mm, 12.7mm, 20mm, or 25.4mm. The isosceles right-angled prism needs to maintain a good surface finish before plating.

[0041] like Figure 1As shown, the present invention deposits an antireflection film on surfaces S1 and S2 of the first part of the substrate. The present invention deposits an antireflection film on surfaces S3 and S4 of the second part of the substrate. In the present invention, prior to the deposition of the antireflection film, it is preferable to further perform ion source cleaning on the substrate. The present invention preferably places the substrate in a collar, and places the collar with the substrate on a perforated umbrella-shaped fixture on the machine; then performs ion source cleaning. The vacuum degree of the ion source cleaning is preferably ≤3.0E-3Pa, the time is preferably 2~5min, and the temperature of the substrate during ion source cleaning is preferably 180~300℃, which can be 200℃ in the embodiment. By controlling the temperature of the substrate to 180~300℃ during ion source cleaning, the present invention can reduce ion absorption of the substrate during the ion source cleaning process. In the present invention, the voltage of the ion source cleaning is preferably 800~850V; the current is preferably 800~850mA. The gas used for ion source cleaning is preferably oxygen and argon, and the flow ratio of oxygen to argon is preferably 60:8. The oxygen flow rate is preferably 60 sccm, and the argon gas includes a first argon gas and a second argon gas. The flow rate of the first argon gas (ion source argon gas) is preferably 0 sccm, and the flow rate of the second argon gas (neutralizer argon gas) is preferably 8 sccm.

[0042] In this invention, the antireflection film is deposited after the ion source cleaning is completed. During the deposition process, the substrate is preferably placed in a collar, and the collar with the substrate is placed on a perforated fixture on the machine. The deposition conditions preferably include: an initial vacuum degree preferably ≤3.0E-3Pa; a substrate temperature preferably 150~200℃, which can be 200℃ in the embodiment. The SiO2 monolayer film formation rate is preferably 0.3~0.7nm / s, which can be 0.4nm / s in the embodiment. The Ti3O5 monolayer film formation rate is preferably 0.2~0.3nm / s, which can be 0.2nm / s in the embodiment. In this invention, the ion source for the Ti3O5 monolayer film deposition is preferably Ti3O5; the voltage is preferably 800-850V; the current is preferably 800-850mA; the gas used is preferably oxygen and argon, and the flow rate ratio of oxygen to argon is preferably 75:16; the flow rate of oxygen is preferably 75 sccm, and the argon includes a first argon and a second argon, the flow rate of the first argon (ion source argon) is preferably 8 sccm, and the flow rate of the second argon (neutralizer argon) is preferably 8 sccm. In this invention, the ion source for the SiO2 monolayer film deposition is preferably SiO2; the voltage is preferably 800-850V; the current is preferably 800-850mA; the gas used is preferably oxygen and argon, and the flow rate ratio of oxygen to argon is preferably 60:8. The flow rate of oxygen is preferably 60 sccm, and the argon includes a first argon and a second argon, the flow rate of the first argon (ion source argon) is preferably 0 sccm, and the flow rate of the second argon (neutralizer argon) is preferably 8 sccm.

[0043] In this invention, the antireflection coating deposition preferably includes: sequentially depositing a Ti3O5 layer, a SiO2 layer, a Ti3O5 layer, a SiO2 layer, ..., a Ti3O5 layer and a SiO2 layer on the surface of the substrate.

[0044] In this invention, an anti-polarization film is deposited on the S5 surface (i.e., the inclined surface of the isosceles right-angle prism) of the first part of the substrate. No film is deposited on the S6 surface (i.e., the inclined surface of the isosceles right-angle prism) of the second part of the substrate.

[0045] In this invention, the bonding is to bond the S5 surface of the first part of the substrate (i.e., the inclined surface of the isosceles right-angle prism) and the S6 surface of the second part of the substrate (i.e., the inclined surface of the isosceles right-angle prism).

[0046] In this invention, the bonding is achieved using a light adhesive based on intermolecular interaction forces. In the embodiments, NOA61 UV-curing adhesive or other adhesives with equivalent properties are used for bonding and curing.

[0047] This invention tests the optical properties of the glued beam splitter (also known as a beam splitter cube) to confirm whether it meets the specifications.

[0048] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0049] Comparative Example 1 Specifications for this comparative example: Depolarizing beam splitter, visible light band, 400~700nm, average reflectivity (Rave) of S1, S2, S3, and S4 < 0.5%; Sloping surface S5 requires a transmittance-to-reflection ratio T:R = 90:10, specifically Tabs = 90±5%, Rabs = 10±5%, |Ts-Tp| < 3%, |Rs-Rp| < 3%.

[0050] (1) Analysis of antireflection film requirements: These are conventional requirements, which can be achieved by alternating stacking of high-refractive-index material titanium pentoxide (Ti3O5) and low-refractive-index material silicon dioxide (SiO2). A simple TFC design yielded the film structure shown in Table 1. The total thickness is 6L, approximately 238nm. The layers in contact with the substrate are: first layer: titanium pentoxide; second layer: silicon dioxide; third layer: titanium pentoxide; fourth layer: silicon dioxide; fifth layer: titanium pentoxide; and finally, sixth layer: silicon dioxide. The design curve is shown in Table 1. Figure 2 , Figure 2 In the center: the angle is 0.0 degrees, and the reference wavelength is 550.0 nm. Observation. Figure 2 The design curve for 400~700nm was calculated to have Rave=0.178%, which satisfies Rave<0.5%.

[0051] Table 1 Antireflective membrane stack Figure 2 The design curves for the 400-700nm antireflection film in Comparative Example 1 are shown. This comparative example uses a vacuum evaporation coating machine manufactured by a domestic vacuum equipment factory to deposit the antireflection film system. The scheme uses crystal oscillator monitoring to monitor the film layer velocity and thickness. Parameters are shown in Table 2.

[0052] Table 2 Ion source cleaning and coating parameters Antireflective coatings were applied to isosceles right-angle prisms A and A1, using B270 material. The S1, S2, S3, and S4 faces, with side lengths A=A1=25.4mm, were coated. The reflectivity of the coatings was tested using an MSP-B testing instrument, and the actual curve Rave = 0.222% < 0.5%, meeting the requirements. Figure 3As shown in the figure. An adhesion test was performed on the coated surface using 3M tape. The film was stuck and pulled 10 times consecutively. The film layer did not peel off, indicating that the adhesion was OK. Figure 3 The actual deposition curves for antireflection coatings in the 400~700nm range are shown.

[0053] (2) Analysis of the requirements for depolarization-free thin films: The transmittance-to-reflectance ratio (T:R) is 90:10, and the stringent requirements of |Ts-Tp| < 3% and |Rs-Rp| < 3% are very stringent. Similar depolarizing films require the design of three materials: high-refractive-index titanium pentoxide (Ti3O5), low-refractive-index silicon dioxide (SiO2), and medium-refractive-index aluminum oxide (Al2O3). Using these three materials, the design curve obtained through TFC design is shown below. Figure 4 . Figure 4 Design curves for polarization elimination of dielectric films. Figure 4 The mid-angle is 45.0 degrees, and the reference wavelength is 560.0 nm. (Based on the design curve...) Figure 4 It can be seen that the transmittance-to-reflectance ratio T:R and the deviations |Ts-Tp|<3% and |Rs-Rp|<3% both meet the requirements. The depolarization design film system consists of a total of 36 layers with a total thickness of 2178 nm, approximately 2.2 μm. There are four thin layers (generally, layers with a thickness less than 10 nm are considered thin layers), located at layers 4, 6, 15, and 34. The film stack structure is shown in Table 3.

[0054] Table 3 Data Table of Dielectric Depolarization Film System The depolarization-deposition film system was designed for deposition, and the ion source cleaning was performed under the same conditions as the antireflection film. The deposition conditions for each material were modified as follows: initial vacuum: ≤1.0E-3Pa; Al2O3 was treated the same as SiO2 except for the velocity setting of 0.3nm / s. The depolarization film was deposited on the inclined surface S5 of prism A. No film was deposited on the inclined surface S6 of prism A1 (antireflection films were only deposited on surfaces S3 and S4 of prism A1). Then, prism A and prism A1, with the depolarization films deposited, were bonded together, and optical data were tested using a Hitachi UH-4150 spectrophotometer. The actual deposition curves are shown below. Figure 5 . Figure 5 and Figure 6 The actual deposition curve and deviation curve of the dielectric film in Comparative Example 1 are shown. The actual deposition curve (...) Figure 5 ) and deviation curve ( Figure 6 It was found that the transmission-to-reflection ratio was close to 90:10, but the ± tolerance was very tight, close to ±5%, which was not enough to be safe. In addition, the deviations |Ts-Tp| and |Rs-Rp| were both greater than 3%, which was within about 6%, and did not meet the requirements.

[0055] Therefore, as shown in Comparative Example 1, the specifications cannot be met using the three conventional dielectric materials. This invention considers introducing silver (Ag), a metallic material with good depolarization properties, to attempt a solution. Introducing silver can significantly reduce the design film thickness and the number of film layers. However, the difficulty in manufacturing silver films lies in process control: strict control is required to prevent oxidation.

[0056] Example 1 (Optimization of Comparative Example 1) This embodiment is an optimization of Comparative Example 1. In this embodiment, the depolarizing beam splitter is used in the visible light band, 400~700nm. Isosceles right-angle prisms A and A1 are used, made of B270 material, with side lengths A=A1=25.4mm. The method for depositing antireflective coatings on the S1, S2, S3, and S4 surfaces of isosceles right-angle prisms A and A1 is the same as in Comparative Example 1. The design of the depolarizing thin film in this embodiment is as follows: (1) Introducing metallic silver using a silver-doped dielectric film. The dielectric layer materials also include three types: low-refractive-index silicon dioxide (SiO2), medium-refractive-index aluminum oxide (Al2O3), and high-refractive-index tantalum pentoxide (Ta2O5). Through TFC simulation, a 7-layer film system was designed. The first layer, in contact with the substrate, is silicon dioxide (SiO2) with a thickness of 81.15±5 nm; the second layer is tantalum pentoxide (Ta2O5) with a thickness of 19.01±2 nm; the third layer is aluminum oxide (Al2O3) with a thickness of 53.37±3 nm; and the fourth layer is metallic silver (Ag) with a thickness of 7.65±1 nm. The fifth layer is aluminum oxide (Al₂O₃), with a thickness of 16.19±2 nm; the sixth layer is tantalum pentoxide (Ta₂O₅), with a thickness of 19.26±2 nm; and the final layer is silicon dioxide (SiO₂), with a thickness of 48.74±3 nm. The design curves are as follows... Figure 7 . Figure 7 Design a depolarization curve for metallic silver. Figure 7 The mid-angle is 45.0 degrees, and the reference wavelength is 560.0 nm. Looking at the design curves, the silver-doped dielectric film design is smoother than the pure dielectric layer design curve in Comparative Example 1, meets stricter specifications, and has transmittance and reflection tolerances within 3%, better than the required ±5%; furthermore, deviations |Ts-Tp| and |Rs-Rp| are far less than 3%. The silver-doped dielectric film has only 7 layers in total, far fewer than the 36 layers of the pure dielectric layer, and the maximum total thickness is less than 300 nm, far less than the 2100 nm of the pure dielectric layer. Therefore, from a design perspective, the silver-doped dielectric layer is superior to the pure dielectric layer design.

[0057] (2) The antireflective coating system was deposited using a vacuum evaporation coating machine manufactured by a domestic vacuum equipment manufacturer. The method used crystal oscillator monitoring to monitor the coating rate and thickness. The parameters are shown in Table 4.

[0058] Table 4 Ion source cleaning and coating parameters The ion source is not used in layers 3-5 to prevent interference with the formation of metallic silver, which could lead to inaccurate monitoring. The spacer layer is added to prevent oxidation of the Ag layer. From an efficiency and effectiveness perspective, a spacer time of 600-900 seconds is optimal, balancing oxidation prevention with efficiency. A waiting time less than 600 seconds carries the risk of interference from stray gases. While a waiting time greater than 900 seconds effectively controls stray gases, it reduces efficiency, hindering industrial production and wasting energy.

[0059] In this embodiment, an antipolarization film is deposited on the inclined surface S5 of prism A. No film is deposited on the inclined surface S6 of prism A1 (antireflection films are only deposited on surfaces S3 and S4 of prism A1). Then, isosceles right-angle prism A, with its inclined surface coated with a silver-doped dielectric film, is bonded to prism A1 and its optical data are tested. A Hitachi UH-4150 spectrophotometer is used to measure the relevant data, obtaining the actual deposition curve and the antipolarization deviation, as shown below. Figure 8 and Figure 9 As shown. Figure 8 Depolarized actual deposition curve of silver-doped dielectric film ( Figure 8 (T:R=90:10) Figure 9 Depolarization deviation diagram of silver-doped dielectric film ( Figure 9 (T:R=90:10). Figure 8 and Figure 9 It can be seen that the actual plating curve satisfies the transmittance / reflectance ratio T:R=90:10, Tave=90±5%, Rave=10±5%, and the deviations |Ts-Tp| and |Rs-Rp| < 2%, meeting the requirement of <3%. Therefore, the method of using a silver-doped dielectric film is superior to the pure dielectric film process and meets the specifications.

[0060] Example 2: The membrane structure and sequence in this embodiment are consistent with those in Embodiment 1. Figure 10 This is a polarization design curve of the 700~1100nm undoped dielectric film of metallic silver in Embodiment 2 of the present invention. Figure 10The median angle is 45.5 degrees, and the reference wavelength is 560.0 nm. The layers in contact with the substrate are: the first layer, silicon dioxide (SiO2), with a thickness of 35.27 ± 3 nm; the second layer, tantalum pentoxide (Ta2O5), with a thickness of 68.7 ± 5 nm; the third layer, aluminum oxide (Al2O3), with a thickness of 31.98 ± 3 nm; the fourth layer, metallic silver (Ag), with a thickness of 6.95 ± 1 nm; the fifth layer, aluminum oxide (Al2O3), with a thickness of 36.18 ± 3 nm; the sixth layer, tantalum pentoxide (Ta2O5), with a thickness of 41.79 ± 3 nm; and the final layer, silicon dioxide (SiO2), with a thickness of 131.45 ± 5 nm.

[0061] Using the method described in Example 1 above, in the wavelength range of 700~1100nm, the depolarizing film of the beam-splitting prism also satisfies the following transmittance / reflectance ratios: Tabs=90±5%, Rabs=10±5%, |Ts-Tp|<3%, and |Rs-Rp|<3%. The actual deposition curve in this example is shown below. Figure 11 As shown in the figure, the polarization deviation reduction curve is as follows: Figure 12 As shown. Figure 11 Depolarization deposition curves of silver-doped dielectric films in the 700~1100nm range ( Figure 11 (T:R=90:10) Figure 12 Depolarization deviation curves of silver-doped dielectric films in the 700~1100nm range ( Figure 11 (T:R=90:10). The membrane structure and sequence are consistent with those in Example 1.

[0062] As can be seen from the above embodiments, this preparation method also meets the specifications for the 700~1100nm wavelength range. The fabrication process of the depolarization film for the beam-splitting prism described in this solution is applicable to the wavelength range of 400~1100nm. The total thickness is less than 400nm.

[0063] As can be seen from the above embodiments, the depolarization-reducing thin film for beam-splitting prisms provided by the present invention has the following advantages: the number of film layers is significantly reduced (<10 layers), the total film thickness is significantly reduced, and it can be achieved within 400nm, greatly optimizing the film thickness, saving the cost of film material and equipment energy consumption, and greatly improving processing efficiency; the significantly thinner film reduces the risk of film cracking and electroplating peeling; the reduced number of layers and thickness means fewer thin layers in the film, making equipment monitoring more precise, and the actual effect is closer to the design, that is, the achievable specifications are more stringent. Conventional dielectric films can achieve Tabs=90±5%, Rabs=10±5%, |Ts-Tp|<10%, |Rs-Rp|<10%, while the depolarization-reducing thin film preparation process can meet the specifications: Tabs=90±5%, Rabs=10±5%, |Ts-Tp|<3%, |Rs-Rp|<3%, and is suitable for any bandwidth range not greater than 400nm within the visible and near-infrared bands of 400~1100nm.

[0064] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A beam-splitting prism depolarization thin film, characterized in that, The beam splitter comprises a first SiO2 film, a first Ta2O5 film, a first Al2O3 film, a silver layer, a second Al2O3 film, a second Ta2O5 film, and a second SiO2 film, which are stacked sequentially. The first SiO2 film is in contact with the surface of the substrate. The thickness of the depolarizing film of the beam splitter is 190-300 nm under 400-700 nm wavelength conditions and 300-400 nm under 700-1100 nm wavelength conditions.

2. The beam-splitting prism depolarization film according to claim 1, characterized in that, Under the 400~700nm wavelength range: the thickness of the first SiO2 film is 70~90nm, the thickness of the first Ta2O5 film is 15~25nm, the thickness of the first Al2O3 film is 40~60nm, the thickness of the metallic silver layer is 6.2~8.8nm, the thickness of the second Al2O3 film is 10~20nm, the thickness of the second Ta2O5 film is 10~25nm, and the thickness of the second SiO2 film is 45~60nm.

3. The beam-splitting prism depolarization film according to claim 1, characterized in that, Under the 700~1100nm wavelength range: the thickness of the first SiO2 film is 30~39nm, the thickness of the first Ta2O5 film is 63~79nm, the thickness of the first Al2O3 film is 28~36nm, the thickness of the metallic silver layer is 5~8nm, the thickness of the second Al2O3 film is 31~40nm, the thickness of the second Ta2O5 film is 35~45nm, and the thickness of the second SiO2 film is 126~139nm.

4. The method for preparing the depolarization-reducing thin film of the beam-splitting prism according to any one of claims 1 to 3, characterized in that, Includes the following steps: Based on the film material, optical band, and optical properties of the depolarization film of the beam splitter, film system design software is used to design the film system and obtain the film system design results of the depolarization film of the beam splitter. A first SiO2 film layer, a first Ta2O5 film layer, a first Al2O3 film layer, a silver film layer, a second Al2O3 film layer, a second Ta2O5 film layer, and a second SiO2 film layer are sequentially deposited on the surface of the substrate according to the film system design results to obtain the polarization-depolarizing thin film of the beam-splitting prism. A first waiting time is set after depositing the first Al2O3 film layer and before depositing the silver film layer, and a second waiting time is set after depositing the silver film layer and before depositing the second Al2O3 film layer. The first waiting time is ≥600s, and the second waiting time is ≥600s.

5. The preparation method according to claim 4, characterized in that, The plating process employs a vacuum evaporation coating method. The deposition conditions include: initial vacuum degree ≤ 1.0E-3Pa; substrate temperature 0~40℃; film formation rates of the first SiO2 film layer and the second SiO2 film layer independently 0.3~0.7nm / s, film formation rates of the first Ta2O5 film layer and the second Ta2O5 film layer independently 0.2~0.3nm / s, film formation rates of the first Al2O3 film layer and the second Al2O3 film layer independently 0.2~0.4nm / s, and film formation rate of the silver layer 0.1~0.2nm / s.

6. The preparation method according to claim 4, characterized in that, Before the plating process, the substrate is cleaned with an ion source. The vacuum degree of the ion source cleaning is ≤1.0E-3Pa, the time is 2~5min, and the temperature of the substrate during the ion source cleaning is 0~40℃.

7. The preparation method according to claim 4, characterized in that, The substrate material includes BK7, K9, or B270.

8. A beam splitter prism, characterized in that, The beam splitter is provided with an anti-polarization film inside, which is the beam splitter anti-polarization film according to any one of claims 1 to 3 or the beam splitter anti-polarization film prepared by the preparation method according to any one of claims 4 to 7.

9. The beam splitter according to claim 8, characterized in that, The outer wall of the beam splitter is also provided with an anti-reflection film, which includes alternating layers of Ti3O5 monolayer film and SiO2 monolayer film, and the Ti3O5 monolayer film is in contact with the outer wall of the beam splitter.

10. The method for preparing the beam-splitting prism according to claim 9, characterized in that, Includes the following steps: An antireflective film is deposited on a first part substrate and a second part substrate; then, a beam splitter depolarization film is deposited on the first part substrate according to the preparation method described in any one of claims 4 to 7; finally, the first part substrate and the second part substrate are bonded together to obtain the beam splitter.

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