Polarization-eliminating film for spectroscopic prism, method for manufacturing the same, spectroscopic prism, and method for manufacturing the same

Abstract

The present application belongs to the technical field of optical light splitting elements, and particularly relates to a light splitting prism depolarization film and a preparation method thereof, and a light splitting prism and a preparation method thereof. The light splitting prism depolarization film provided by the present application 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 stacked, and the first SiO2 film layer is in contact with the surface of the substrate. The light splitting prism depolarization film provided by the present application has a significantly reduced number of film layers, a significantly thinned total film thickness, greatly optimized film layer thickness, saved film material usage cost and equipment energy consumption, and greatly improved processing efficiency; at the same time, the risk of film layer rupture and electroplating layer falling is reduced; 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, and the light splitting prism depolarization film has excellent practical value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical beam splitting elements, and particularly relates to a depolarization film for a beam splitting prism, a preparation method thereof, a beam splitting prism and a preparation method thereof. BACKGROUND

[0002] A depolarization beam splitting prism (NPBS) is an optical beam splitting element for maintaining the polarization state of incident light, and is widely used in the fields of interference analysis instruments, life science instruments and laser systems. The prism material is generally selected from BK7, K9 or B270, and the size of a right-angle prism is about 5mm, 10mm, 12.7mm or 25.4mm in length. The depolarization beam splitting film coated on the inclined surface is mostly made of three dielectric materials, i.e., high refractive index material Ti3O5, low refractive index material SiO2 and medium refractive index material Al2O3, which are alternately stacked. The film system has the following disadvantages:

[0003] 1. The number of layers is large, generally about 30 or more, and the total film thickness is large, about 2-3um. The thick film layer directly causes waste of coating material and long film forming time, and waste of power consumption. 2. The thick film layer is prone to film cracking and other reliability problems. 3. The more the total number of layers, the higher the probability of containing thin layers (generally, a layer with a thickness of less than 10nm is defined as a thin layer), and the more difficult it is to control the thin layer. The more the thin layers, the greater the cumulative error, the more difficult it is to control the whole, and the greater the difference between the design and the actual situation. SUMMARY

[0004] The purpose of the present application is to provide a depolarization film for a beam splitting prism, a preparation method thereof, a beam splitting prism and a preparation method thereof. The number of layers of the depolarization film for the beam splitting prism provided by the present application is significantly reduced, the total film thickness is significantly thinned, the film layer thickness is greatly optimized, the film material usage cost and equipment energy consumption are saved, and the processing efficiency is greatly improved. At the same time, the risk of film layer cracking and falling off the plating layer is reduced. The thin layers contained in the film layer are relatively less, the equipment monitoring is more accurate, the actual effect is closer to the design, the specifications can be realized more strictly, and the depolarization film for the beam splitting prism has excellent practical value.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] The present application provides a depolarization film for a beam splitting prism, which comprises first SiO2 film layers, first Ta2O5 film layers, first Al2O3 film layers, a metal silver layer, second Al2O3 film layers, second Ta2O5 film layers and second SiO2 film layers which are sequentially stacked, and the first SiO2 film layers are in contact with the surface of the substrate. The thickness of the depolarization film for the beam splitting prism under the condition of a 400-700nm wave band is 190-300nm, and the thickness of the depolarization film for the beam splitting prism under the condition of a 700-1100nm wave band is 300-400nm.

[0007] Preferably, under the condition of 400-700nm waveband: the thickness of the first SiO2 film layer is 70-90nm, the thickness of the first Ta2O5 film layer is 15-25nm, the thickness of the first Al2O3 film layer is 40-60nm, the thickness of the metal silver layer is 6.2-8.8nm, the thickness of the second Al2O3 film layer is 10-20nm, the thickness of the second Ta2O5 film layer is 10-25nm, and the thickness of the second SiO2 film layer is 45-60nm.

[0008] Preferably, under the condition of 700-1100nm waveband: the thickness of the first SiO2 film layer is 30-37nm, the thickness of the first Ta2O5 film layer is 65-79nm, the thickness of the first Al2O3 film layer is 30-36nm, the thickness of the metal silver layer is 5-8nm, the thickness of the second Al2O3 film layer is 31-38nm, the thickness of the second Ta2O5 film layer is 35-44nm, and the thickness of the second SiO2 film layer is 130-139nm.

[0009] The application provides a preparation method of the above-mentioned technical solution, comprising the following steps:

[0010] According to the film layer material, optical waveband and optical performance of the light-splitting prism depolarization film, a film system design software is used to design a film system, so as to obtain a film system design result of the light-splitting prism depolarization film.

[0011] 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 are sequentially plated on the surface of the substrate according to the film system design result, so as to obtain the light-splitting prism depolarization film, a first waiting time is set after plating the first Al2O3 film layer and before plating the metal silver layer, a second waiting time is set after plating the metal silver layer and before plating the second Al2O3 film layer, the first waiting time is greater than or equal to 600s, and the second waiting time is greater than or equal to 600s.

[0012] Preferably, the plating adopts a vacuum evaporation plating method.

[0013] The plating conditions include: initial vacuum degree ≤ 1.0E-3 Pa; the temperature of the substrate is 0-40℃; the film formation rate of the first SiO2 film layer and the second SiO2 film layer is independently 0.3-0.7 nm / s, the film formation rate of the first Ta2O5 film layer and the second Ta2O5 film layer is independently 0.2-0.3 nm / s, the film formation rate of the first Al2O3 film layer and the second Al2O3 film layer is independently 0.2-0.4 nm / s, and the film formation rate of the metal silver layer is 0.1-0.2 nm / s.

[0014] Preferably, before the plating, the substrate is subjected to ion source cleaning, the vacuum degree of the ion source cleaning is ≤ 1.0E-3 Pa, the time is 2-5 min, and the temperature of the substrate during the ion source cleaning is 0-40℃.

[0015] Preferably, the material of the substrate includes BK7, K9 or B270.

[0016] The application provides a light splitting prism, which is internally provided with a depolarization film.

[0017] Preferably, the outer side wall of the light splitting prism is further provided with an anti-reflection film, the anti-reflection film includes Ti3O5 monolayer films and SiO2 monolayer films which are alternately and laminatedly arranged, and the Ti3O5 monolayer film is in contact with the outer side wall of the light splitting prism.

[0018] The application provides a preparation method of the light splitting prism.

[0019] The anti-reflection film is plated on the first part of the substrate and the second part of the substrate; then the depolarization film is plated on the first part of the substrate according to the preparation method of the above technical solution; finally, the first part of the substrate and the second part of the substrate are glued to obtain the light splitting prism.

[0020] The application provides a spectrometer prism depolarization film, which 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 arranged, and the first SiO2 film layer is in contact with the surface of a substrate; the thickness of the spectrometer prism depolarization film under the condition of a 400-700 nm wave band is 190-300 nm; and the thickness of the spectrometer prism depolarization film under the condition of a 700-1100 nm wave band is 300-400 nm. The metal silver layer is introduced into the film layer structure of the depolarization film, and the number of film layers and the thickness of the spectrometer prism depolarization film are significantly reduced by means of metal silver doping dielectric film. Compared with the prior art, the application has the following beneficial effects: (1) the number of film layers is significantly reduced (<10 layers), the total film thickness is significantly reduced, and the film thickness can be realized within about 400 nm, the film layer thickness is greatly optimized, the film material usage cost and equipment energy consumption are saved, and the processing efficiency is greatly improved; (2) the film layer is significantly thinned, and the risk of film layer rupture and plating layer falling is reduced; (3) the number of layers and the thickness are reduced, the film layer contains relatively fewer thin layers, the equipment monitoring is more accurate, and the actual effect is closer to the design, that is, the specification can be realized more strictly. The conventional depolarization film can realize average transmittance (Tabs)=90±5%, absolute average reflectance (Rabs)=10±5%, absolute difference (|Ts-Tp|) between s-polarized light transmittance (Ts) and p-polarized light transmittance (Tp)<10%, absolute difference (|Rs-Rp|) between s-polarized light reflectance (Rs) and p-polarized light reflectance (Rp)<10%, the depolarization film provided by the application can meet the specifications: Tabs=90±5%, Rabs=10±5%, |Ts-Tp|<3%, |Rs-Rp|<3%, and the optical performance of the depolarization film provided by the application is obviously better than that of the conventional depolarization film. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Isosceles right-angle prism A and A1 used in the application;

[0022] Figure 2 Design curve of 400-700 nm anti-reflection film in Comparative Example 1 of the application;

[0023] Figure 3 Actual plating curve of 400-700 nm anti-reflection film in Comparative Example 1 of the application;

[0024] Figure 4 Design curve of dielectric film depolarization in Comparative Example 1 of the application;

[0025] Figure 5 Actual plating curve of dielectric film depolarization in Comparative Example 1 of the application;

[0026] Figure 6 The design curve of the depolarization deviation of the medium film in the present application comparative example 1;

[0027] Figure 7 The design curve of the depolarization of the metal silver doped medium film in the present application example 1;

[0028] Figure 8 The actual plating curve of the depolarization of the metal silver doped medium film in the present application example 1;

[0029] Figure 9 The design curve of the depolarization deviation of the metal silver doped medium film in the present application example 1;

[0030] Figure 10 The design curve of the depolarization of the 700~1100nm metal silver doped medium film in the present application example 2;

[0031] Figure 11 The actual plating curve of the depolarization of the 700~1100nm metal silver doped medium film in the present application example 2;

[0032] Figure 12 The design curve of the depolarization deviation of the 700~1100nm metal silver doped medium film in the present application example 2. DETAILED DESCRIPTION

[0033] The present application provides a spectroscopic prism depolarization film, comprising 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 stacked, the first SiO2 film layer is in contact with the surface of the substrate; the thickness of the spectroscopic prism depolarization film under the condition of 400~700nm wave band is 190~300nm; the thickness of the spectroscopic prism depolarization film under the condition of 700~1100nm wave band is 300~400nm.

[0034] The film layer number of the spectroscopic prism depolarization film provided by the present application is obviously reduced (<10 layers), and the total film thickness is obviously thinned. Therefore, the spectroscopic prism depolarization film provided by the present application is also a method for reducing the thickness of the spectroscopic prism depolarization film. The film structure of the spectroscopic prism depolarization film is sequentially stacked with a first SiO2 layer, a first Ta2O5 film layer, a first Al2O3 layer, a metal silver layer, a second Al2O3 film layer, a second Ta2O5 film layer and a second SiO2 film layer, and the first SiO2 layer is in contact with the substrate. The film layer number of the spectroscopic prism depolarization film is obviously reduced (<10 layers), and the total film thickness is obviously thinned.

[0035] In the present application, under the condition of 400-700 nm waveband: the thickness of the first SiO2 film layer is preferably 70-90 nm, and in the embodiment can be 81.15±5 nm. The thickness of the first Ta2O5 film layer is preferably 15-25 nm, and in the embodiment can be 19.01±2 nm. The thickness of the first Al2O3 film layer is preferably 40-60 nm, and in the embodiment can be 53.37±3 nm. The thickness of the metal silver layer is preferably 6.2-8.8 nm, and in the embodiment can be 7.65±1 nm. The thickness of the second Al2O3 film layer is preferably 10-20 nm, and in the embodiment can be 16.19±2 nm. The thickness of the second Ta2O5 film layer is preferably 10-25 nm, and in the embodiment can be 19.26±2 nm. The thickness of the second SiO2 film layer is preferably 45-60 nm, more preferably 45-55 nm, and in the embodiment can be 48.74±3 nm.

[0036] In the present application, under the condition of 700-1100 nm waveband: the thickness of the first SiO2 film layer is preferably 30-39 nm, and in the embodiment can be 35.27±3 nm. The thickness of the first Ta2O5 film layer is preferably 63-79 nm, and in the embodiment can be 68.7±5 nm. The thickness of the first Al2O3 film layer is preferably 28-36 nm, and in the embodiment can be 31.98±3 nm. The thickness of the metal silver layer is preferably 5-8 nm, and in the embodiment can be 6.95±1 nm. The thickness of the second Al2O3 film layer is preferably 31-40 nm, and in the embodiment can be 36.18±3 nm. The thickness of the second Ta2O5 film layer is preferably 35-45 nm, and in the embodiment can be 41.79±3 nm. The thickness of the second SiO2 film layer is preferably 126-139 nm, and in the embodiment can be 131.45±5 nm.

[0037] The present application provides a preparation method of the above-mentioned technical solution, comprising the following steps:

[0038] According to the film layer material, optical waveband and optical performance of the light-splitting prism depolarization film, a film system design software is used for film system design to obtain the film system design result of the light-splitting prism depolarization film.

[0039] The first SiO2 film layer, the first Ta2O5 film layer, the first Al2O3 film layer, the metal silver layer, the second Al2O3 film layer, the second Ta2O5 film layer and the second SiO2 film layer are sequentially plated on the surface of the substrate according to the film system design result of the spectrometer prism depolarization film, the first waiting time is set after plating the first Al2O3 film layer and before plating the metal silver layer, the second waiting time is set after plating the metal silver layer and before plating the second Al2O3 film layer, the first waiting time is greater than or equal to 600 seconds, and the second waiting time is greater than or equal to 600 seconds.

[0040] In the present application, all the preparation raw materials / components are commercially available products well known to those skilled in the art, unless otherwise specified.

[0041] In the present application, the optical waveband can be 400-700 nm or 700-1100 nm. The optical performance includes Tabs, Rabs, the ratio of transmitted light intensity to reflected light intensity (transmission-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 film system design result of the spectrometer prism depolarization film includes the thickness of each layer and the total thickness.

[0042] After obtaining the film system design result of the spectrometer prism depolarization film, the first SiO2 film layer, the first Ta2O5 film layer, the first Al2O3 film layer, the metal silver layer, the second Al2O3 film layer, the second Ta2O5 film layer and the second SiO2 film layer are sequentially plated on the surface of the substrate according to the film system design result, the first waiting time is set after plating the first Al2O3 film layer and before plating the metal silver layer, the second waiting time is set after plating the metal silver layer and before plating the second Al2O3 film layer, the first waiting time is greater than or equal to 600 seconds, and the second waiting time is greater than or equal to 600 seconds.

[0043] In the present application, the material of the substrate preferably includes BK7, K9 or B270.

[0044] In the present application, before the plating, the present application preferably further comprises ion source cleaning of the substrate. The present application preferably places the substrate in a sleeve, places the sleeve provided with the substrate on the machine hollow umbrella, and then performs ion source cleaning. The present application preferably improves the adhesion of the spectroscopic prism depolarization film on the surface of the substrate by the ion source cleaning. The vacuum degree of the ion source cleaning is preferably ≤1.0E-3Pa, the time is preferably 2-5min, more preferably 3min; the temperature of the substrate during the ion source cleaning is preferably 0-40℃. In the present application, the voltage of the ion source cleaning is preferably 700-800V; the current is preferably 700-800mA. The gas used in the ion source cleaning is preferably oxygen and argon, and the flow ratio of the oxygen and argon is preferably 40-60:5-8. The flow of the oxygen is preferably 40-60sccm. The argon includes first argon and second argon, the flow of the first argon (ion source argon) is preferably 0sccm, and the flow of the second argon (neutralizer argon) is preferably 5-8sccm.

[0045] In the present application, the plating is performed after the ion source cleaning.

[0046] In the present application, the plating preferably adopts the method of vacuum evaporation plating. The spectroscopic prism depolarization film is plated by a vacuum evaporation plating machine.

[0047] In the present application, during the plating, the present application preferably places the substrate in a sleeve, and places the sleeve provided with the substrate on the machine hollow umbrella. The conditions of the plating preferably include: the initial vacuum degree is preferably ≤1.0E-3Pa. The temperature of the substrate is preferably 0-40℃. The film formation rate of the first SiO2 film layer and the second SiO2 film layer is preferably 0.3-0.7nm / s, which can be 0.4nm / s in the examples. The film formation rate of the first Ta2O5 film layer and the second Ta2O5 film layer is preferably 0.2-0.3nm / s, which can be 0.2nm / s in the examples. The film formation rate of the first Al2O3 film layer and the second Al2O3 film layer is preferably 0.2-0.4nm / s, which can be 0.3nm / s in the examples. The film formation rate of the metal silver layer is preferably 0.1-0.2nm / s, which can be 0.15nm / s in the examples.

[0048] In the application, the ion source for plating the first and second SiO2 film layers is preferably SiO2; the voltage is preferably 800-850 V; the current is preferably 800-850 mA; the gas used is preferably oxygen and argon, and the flow ratio of the oxygen and argon is preferably 40:8. The flow of the oxygen is preferably 40 sccm, and the argon includes first argon and second argon, the flow of the first argon (ion source argon) is preferably 0 sccm, and the flow of the second argon (neutralizer argon) is preferably 8 sccm.

[0049] In the application, the ion source for plating the first and second Ta2O5 film layers is preferably Ti3O5; the voltage is preferably 800-850 V; the current is preferably 800-850 mA; the gas used is preferably oxygen and argon, and the flow ratio of the oxygen and argon is preferably 60:16; the flow of the oxygen is preferably 60 sccm, and the argon includes first argon and second argon, the flow of the first argon (ion source argon) is preferably 8 sccm, and the flow of the second argon (neutralizer argon) is preferably 8 sccm.

[0050] In the application, the ion source for plating the first and second Al2O3 film layers is preferably Al2O3; the ion source is not turned on when plating the first and second Al2O3 film layers (i.e. the corresponding parameters: the voltage is 0, and the current is 0); the gas used is preferably oxygen and argon, and the flow ratio of the oxygen and argon is preferably 40:8. The flow of the oxygen is preferably 40 sccm, and the argon includes first argon and second argon, the flow of the first argon (ion source argon) is preferably 0 sccm, and the flow of the second argon (neutralizer argon) is preferably 8 sccm.

[0051] In the application, a first waiting time is arranged after plating the first Al2O3 film layer and before plating the metal silver layer, and the first waiting time is ≥600 s, and is preferably 600-900 s (in order to prevent impurity gas from interfering with the plating of the metal layer).

[0052] In the application, the ion source for plating the metal silver layer is preferably Ag element. The ion source is not turned on when plating the metal silver layer (i.e. the corresponding parameters: the voltage is 0, and the current is 0); the gas used is preferably argon, and the argon includes first argon and second argon, the flow of the first argon (ion source argon) is preferably 60 sccm, and the flow of the second argon (neutralizer argon) is preferably 8 sccm.

[0053] In the application, the ion source is not turned on when plating the first Al2O3 film layer, the second Al2O3 film layer and the metal silver layer, which can effectively interfere with the metal silver layer and avoid inaccurate monitoring during the plating of the film layers.

[0054] In the present application, a second waiting time is set after plating the silver metal layer and before plating the second Al2O3 film layer, the second waiting time is ≥600s, preferably 600-900s (to prevent impurity gases from interfering with the plating of the metal layer).

[0055] The present application sets a first waiting time and a second waiting time, which can prevent the Ag layer from being oxidized. From the efficiency and effect, the interval layer is set to 600-900s, which can prevent oxidation and also take into account efficiency. When the waiting time is less than 600s, there is a risk of impurity gas affecting. When it is greater than 900s, although the impurity gas can be well controlled, the efficiency is affected, which is not conducive to industrial production and wastes energy consumption.

[0056] The present application provides a light splitting prism, which is internally provided with a depolarization film, the depolarization film being the light splitting prism depolarization film according to the technical solution or the light splitting prism depolarization film prepared by the preparation method.

[0057] In the present application, the outer side wall of the light splitting prism is further provided with an anti-reflection film, the anti-reflection film comprising Ti3O5 monolayer films and SiO2 monolayer films which are alternately stacked, and the Ti3O5 monolayer film is in contact with the outer side wall of the light splitting prism. In the present application, the anti-reflection film reduces the reflectivity of the corresponding surface and improves the transmittance. The average reflectivity (Rave) of the anti-reflection film in the waveband range is <0.5%. The anti-reflection film can be realized by alternately stacking 5-7 layers of high refractive index material titanium pentoxide (Ti3O5) and low refractive index material silicon dioxide (SiO2).

[0058] The present application provides a preparation method of the light splitting prism according to the technical solution, comprising the following steps:

[0059] The anti-reflection film is plated on the first part of the substrate and the second part of the substrate, then the depolarization film is plated on the first part of the substrate according to the preparation method of the technical solution, and finally the first part of the substrate and the second part of the substrate are glued to obtain the light splitting prism.

[0060] In the present application, the first part of the substrate (denoted as A) and the second part of the substrate (denoted as A1) are the same isosceles right-angle prism (as shown in Figure 1 In the present application, the right-angle side of the isosceles right-angle prism A=A1 can be 5mm, 10mm, 12.7mm, 20mm or 25.4mm. The isosceles right-angle prism needs to be kept in good condition before plating.

[0061] As shown in Figure 1As shown, the application coats an anti-reflection film on the S1 and S2 surfaces of the first part of the substrate. The application coats an anti-reflection film on the S3 and S4 surfaces of the second part of the substrate. Before the coating of the anti-reflection film, the application preferably further comprises ion source cleaning of the substrate. The application preferably places the substrate in a sleeve, places the sleeve provided with the substrate on a machine hollow umbrella tool, and then performs ion source cleaning. The vacuum degree of the ion source cleaning is preferably ≤3.0E-3Pa, the time is preferably 2-5 min, and the temperature of the substrate during the ion source cleaning is preferably 180-300°C, which can be 200°C in the examples. By controlling the temperature of the substrate during the ion source cleaning to be 180-300°C, the application can reduce the ion absorption of the substrate during the ion source cleaning. In the application, the voltage of the ion source cleaning is preferably 800-850V, and the current is preferably 800-850mA. The gas used in the ion source cleaning is preferably oxygen and argon, and the flow ratio of the oxygen and argon is preferably 60:8. The flow of the oxygen is preferably 60sccm, and the argon includes first argon and second argon, the flow of the first argon (ion source argon) is preferably 0sccm, and the flow of the second argon (neutralizer argon) is preferably 8sccm.

[0062] In the present application, the ion source is cleaned before the antireflection film is deposited. In the present application, the substrate is placed in a sleeve during the deposition. The sleeve with the substrate is placed on the hollow umbrella of the machine. The deposition conditions include: the initial vacuum is preferably ≤3.0E-3 Pa; the temperature of the substrate is preferably 150-200°C, and in the embodiments, it can be 200°C. The deposition rate of the SiO2 monolayer film is preferably 0.3-0.7 nm / s, and in the embodiments, it can be 0.4 nm / s. The deposition rate of the Ti3O5 monolayer film is preferably 0.2-0.3 nm / s, and in the embodiments, it can be 0.2 nm / s. In the present application, the ion source for the deposition of the Ti3O5 monolayer film is preferably Ti3O5; the voltage is preferably 800-850 V; the current is preferably 800-850 mA; the gas used is preferably oxygen and argon, and the flow ratio of the oxygen and argon is preferably 75:16; the flow of the oxygen is preferably 75 sccm, and the argon includes first argon and second argon, the flow of the first argon (ion source argon) is preferably 8 sccm, and the flow of the second argon (neutralizer argon) is preferably 8 sccm. In the present application, the ion source for the deposition of the SiO2 monolayer film is preferably SiO2; the voltage is preferably 800-850 V; the current is preferably 800-850 mA; the gas used is preferably oxygen and argon, and the flow ratio of the oxygen and argon is preferably 60:8. The flow of the oxygen is preferably 60 sccm, and the argon includes first argon and second argon, the flow of the first argon (ion source argon) is preferably 0 sccm, and the flow of the second argon (neutralizer argon) is preferably 8 sccm.

[0063] In the present application, the deposition of the antireflection film preferably includes: the Ti3O5 layer, the SiO2 layer, the Ti3O5 layer, the SiO2 layer, …, the Ti3O5 layer, and the SiO2 layer are sequentially deposited on the surface of the substrate.

[0064] In the present application, the first part of the substrate is glued to the second part of the substrate on the S5 surface (i.e. the inclined surface of the isosceles right-angled prism) and the S6 surface (i.e. the inclined surface of the isosceles right-angled prism).

[0065] In the present application, the first part of the substrate is glued to the second part of the substrate on the S5 surface (i.e. the inclined surface of the isosceles right-angled prism) and the S6 surface (i.e. the inclined surface of the isosceles right-angled prism).

[0066] In the present application, the glue is a light glue with intermolecular forces, and in the embodiments, NOA61 ultraviolet curing glue or other glue with similar performance is used for bonding and curing.

[0067] The present application performs optical index testing on a cemented beam splitter prism (also known as a beam splitting cube) to confirm whether it meets the specifications.

[0068] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present application.

[0069] Comparative Example 1

[0070] The specification requirements in this comparative example: depolarization beam splitter prism, visible light band, 400~700nm, the average reflectivity (Rave) of S1, S2, S3, S4 <0.5%; the requirements for the inclined surface S5 are that the transmittance to reflectance ratio T:R=90:10, and the specific requirements are Tabs=90±5%, Rabs=10±5%, |Ts-Tp|<3%, |Rs-Rp|<3%.

[0071] (1) Analyze the requirement for the anti-reflection film: it belongs to the conventional requirement, and a high refractive index material titanium pentoxide (Ti3O5) and a low refractive index material silicon dioxide (SiO2) are alternately stacked to achieve it. After a simple design of TFC, the film layer structure is obtained as shown in Table 1. There are a total of 6L, and the total thickness is about 238nm. The first layer in contact with the substrate is titanium pentoxide, followed by the second layer of silicon dioxide, then the third layer of titanium pentoxide, followed by the fourth layer of silicon dioxide, then the fifth layer of titanium pentoxide, and finally the sixth layer of silicon dioxide. The design curve is as follows Figure 2 , Figure 2 The angle is 0.0deg, and the reference wavelength is 550.0nm. The design curve of Figure 2 400~700nm is calculated to obtain Rave=0.178%, which meets the requirement of Rave<0.5%.

[0072] Table 1 Anti-reflection film stack

[0073]

[0074] Figure 2 The design curve of the anti-reflection film in 400~700nm in Comparative Example 1. In this comparative example, a vacuum evaporation coating machine manufactured by a certain domestic vacuum equipment factory is used to coat the anti-reflection film system. This scheme uses a crystal oscillator monitoring method to monitor the film layer rate and thickness. The parameters are shown in Table 2.

[0075] Table 2 Ion source cleaning and film coating parameter table

[0076]

[0077] For the isosceles right-angle prism A and the isosceles right-angle prism A1, the material B270 is selected, the S1, S2, S3 and S4 surfaces with a side length of A=A1=25.4 mm are coated with an anti-reflection film, the reflectivity of the film layer is tested by the tester MSP-B, the actual curve Rave=0.222%<0.5% is obtained, which meets the requirements, as shown in Figure 3 The adhesion test is performed on the coated surface, the 3M adhesive tape is used, the film layer does not fall off after being pulled for 10 times in succession, which indicates that the adhesion is OK. Figure 3 The actual coating curve of the anti-reflection film for 400-700 nm is shown in

[0078] (2) Analysis of the demand for the depolarization film:

[0079] The transmittance to reflectance ratio T:R is 90:10, and |Ts-Tp|<3%, |Rs-Rp|<3% is very strict. Similar depolarization spectrometric film needs to be designed by using three kinds of materials, which are high refractive index material titanium pentoxide (Ti3O5), low refractive index material silicon dioxide (SiO2) and medium refractive index material aluminum oxide (Al2O3). By using the above three kinds of materials, the design curve obtained by TFC design is as shown in Figure 4 . Figure 4 The design curve of the medium film depolarization is shown in Figure 4 The medium angle is 45.0 deg, and the reference wavelength is 560.0 nm. According to the design curve Figure 4 , the transmittance to reflectance ratio T:R and the deviation |Ts-Tp|<3%, |Rs-Rp|<3% both meet the requirements. The total number of the depolarization design film system is 36 layers, and the total thickness is 2178 nm, about 2.2 μm. There are four thin layers (generally less than 10 nm in thickness is regarded as a thin layer) at the 4th, 6th, 15th and 34th layers. The film system stacking structure is shown in Table 3.

[0080] Table 3 Data table of the medium depolarization film system

[0081]

[0082] The film is coated according to the depolarization design film system, and the ion source cleaning is performed under the same conditions as the anti-reflection film. The film forming conditions of each material are modified as follows: initial vacuum: ≤1.0E-3 Pa, Al2O3 is set to 0.3 nm / s except for the rate, and the other conditions are the same as those of SiO2. The depolarization film is coated on the inclined surface S5 of the prism A. The inclined surface S6 of the prism A1 is not coated with a film (the prism A1 is only coated with an anti-reflection film on the surfaces S3 and S4). Then, the prism A coated with the depolarization film is glued to the prism A1, and the optical data is tested by using the Hitachi UH-4150 spectrophotometer, and the actual coating curve is as shown in Figure 5 . Figure 5 and Figure 6 The actual coating curve and the deviation curve of the medium film depolarization in Comparative Example 1 are shown in Figure 5) and deviation curve (Fig. 6) Figure 6 It is found that the trans-reflection ratio is close to 90:10, but the tolerance is very limited, close to ±5%, the balance is not safe enough, and the deviations |Ts-Tp| and |Rs-Rp| are both greater than 3%, about within 6%, which does not meet the requirements.

[0083] Therefore, from Comparative Example 1, it can be seen that the conventional three kinds of medium materials cannot meet the specification requirements. The present application considers introducing the metal material silver (Ag) to try to introduce metal silver, which can greatly reduce the design film thickness and the number of film layers. However, the metal silver film system is difficult to control in process: it needs to be strictly controlled not to be oxidized.

[0084] Example 1 (optimization of Comparative Example 1)

[0085] This example is an optimization of Comparative Example 1. In this example, the depolarizing prism is in the visible light band, 400-700 nm. In this example, isosceles right-angle prisms A and A1 are used, and the material B270 is selected, with the side length A=A1=25.4 mm. The S1, S2, S3, and S4 surfaces of the isosceles right-angle prisms A and A1 are coated with antireflection films in the same way as in Comparative Example 1. The design of the depolarizing film in this example is as follows:

[0086] (1) Metal silver is introduced, and a metal silver-doped dielectric film is used. The dielectric layer materials include three kinds, namely, low refractive index material silicon dioxide (SiO2), medium refractive index material aluminum oxide (Al2O3), and high refractive index material tantalum pentoxide (Ta2O5). Through TFC simulation, a 7-layer film system is obtained. 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; the fourth layer is metal 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 last layer is silicon dioxide (SiO2) with a thickness of 48.74±3 nm. The design curve is as follows: Figure 7 . Figure 7 The design curve of the metal silver depolarization is as follows. Figure 7The 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.

[0087] (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.

[0088] Table 4 Ion source cleaning and coating parameters

[0089]

[0090] 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.

[0091] 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.

[0092] Example 2:

[0093] The film system structure and order of this embodiment are consistent with those of Example 1, Figure 10 The figure is a design curve of the 700-1100 nm metal silver doped dielectric film polarizer in Example 2 of the present application. Figure 10 The medium angle is 45.5 deg, and the reference wavelength is 560.0 nm. The first layer in contact with the substrate is silicon dioxide (SiO2) with a thickness of 35.27±3 nm; the second layer is tantalum pentoxide (Ta2O5) with a thickness of 68.7±5 nm; the third layer is aluminum oxide (Al2O3) with a thickness of 31.98±3 nm; the fourth layer is metal silver (Ag) with a thickness of 6.95±1 nm. The fifth layer is aluminum oxide (Al2O3) with a thickness of 36.18±3 nm, the sixth layer is tantalum pentoxide (Ta2O5) with a thickness of 41.79±3 nm; and the last layer is silicon dioxide (SiO2) with a thickness of 131.45±5 nm.

[0094] By the method of Example 1 above, the spectrophotometric prism depolarization film also meets the requirements of transmittance to reflectance Tabs=90±5%, Rabs=10±5%, |Ts-Tp|<3%, |Rs-Rp|<3% in the 700-1100 nm waveband. The actual plating curve in this embodiment is shown in Figure 11 , and the depolarization deviation curve is shown in Figure 12 . Figure 11 The actual plating curve of the 700-1100 nm metal silver doped dielectric film depolarization is shown in Figure 11 , in which T:R=90:10. Figure 12 The depolarization deviation curve of the 700-1100 nm metal silver doped dielectric film is shown in Figure 11 , in which T:R=90:10. The film system structure and order are consistent with those of Example 1.

[0095] As can be seen from the above examples, the preparation method also meets the specification requirements in the 700-1100 nm waveband. The preparation process of the spectrophotometric prism depolarization film described in this scheme is suitable for a waveband range of 400-1100 nm. The total thickness is less than 400 nm.

[0096] From the above embodiments, the spectral prism depolarization film provided by the present application has the following advantages: the number of film layers is significantly reduced (<10 layers), the total film thickness is significantly reduced, which can be achieved within 400 nm, the film layer thickness is greatly optimized, the film material usage cost and equipment energy consumption are saved, and the processing efficiency is greatly improved; the film layer is significantly thinned, reducing the risk of film layer rupture and plating layer falling off; the number of layers and thickness is reduced, the thin layer contained in the film layer is relatively less, the equipment monitoring is more accurate, and the actual effect is closer to the design, that is, the specification can be implemented more strictly. The conventional dielectric film can achieve Tabs=90±5%, Rabs=10±5%, |Ts-Tp|<10%, |Rs-Rp|<10%, the preparation process of the depolarization film can meet the specification: Tabs=90±5%, Rabs=10±5%, |Ts-Tp|<3%, |Rs-Rp|<3%, and is suitable for any bandwidth range not greater than 400 nm within the visible and near-infrared waveband 400~1100nm.

[0097] Although the above embodiments have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained under the premise of not being creative according to the present embodiments, which belong to the protection scope of the present application.

Claims

1. A polarization-depolarizing thin film for a beam-splitting prism, characterized in that, The beam splitter depolarizing film comprises, in sequence, a first SiO2 film, a first Ta2O5 film, a first Al2O3 film, a silver film, a second Al2O3 film, a second Ta2O5 film, and a second SiO2 film, wherein the first SiO2 film is in contact with the surface of the substrate. The thickness of the depolarizing film in the 400-700 nm wavelength range is 190-300 nm. Specifically, in the 400-700 nm wavelength range: the thickness of the first SiO2 film is 70-90 nm, the thickness of the first Ta2O5 film is 15-25 nm, the thickness of the first Al2O3 film is 40-60 nm, the thickness of the silver film is 6.2-8.8 nm, and the thickness of the second Al2O3 film is 10-20 nm. The thickness of the second Ta2O5 film is 10~25nm, and the thickness of the second SiO2 film is 45~60nm; the thickness of the depolarizing film of the beam-splitting prism under the 700~1100nm wavelength band is 300~400nm. Under the 700~1100nm wavelength band: 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.

2. The method for preparing the depolarization-reducing thin film of the beam-splitting prism according to claim 1, 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.

3. The preparation method according to claim 2, 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.

4. The preparation method according to claim 2, 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℃.

5. The preparation method according to claim 2, characterized in that, The substrate material includes BK7, K9, or B270.

6. A beam-splitting prism, characterized in that, The beam splitter is provided with an anti-polarization film inside, which is the beam splitter anti-polarization film of claim 1 or the beam splitter anti-polarization film prepared by the preparation method of any one of claims 2 to 5.

7. The beam splitter according to claim 6, 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.

8. The method for preparing the beam-splitting prism according to claim 7, characterized in that, Includes the following steps: An antireflective coating 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 2 to 5; finally, the first part substrate and the second part substrate are bonded together to obtain the beam splitter.

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