CN114296248B - Spectroscopic film, selective spectroscope, optical device and spectroscopic method - Google Patents

Abstract

The invention relates to a light splitting film, a selective spectroscope, an optical device and a light splitting method. The above light splitting film is useful for spatially separating light of 850nm and light of 1550nm by providing silicon dioxide film layers and silicon nitride film layers alternately stacked, so that it has high reflectivity for light of 850nm and high transmittance for light of 1550nm, and has high selectivity for light of 850nm and light of 1550 nm. The selective spectroscope comprises a lens matrix and a light splitting film, wherein the light splitting film is arranged on the lens matrix. When the optical communication system adopts two kinds of light with the wavelength of 850nm and 1550nm to transmit in the same optical path, the selective spectroscope can spatially separate the two kinds of light in a receiving section, which is beneficial for a back-end receiver to respectively identify signals loaded on light beams with different wave bands.

Description

Spectroscopic film, selective spectroscope, optical device and spectroscopic method

technical field

The invention relates to the technical field of beam separation, in particular to a beam splitting film, a selective beam splitter, optical equipment and a beam splitting method.

Background technique

Lasers with different wavelengths have different attenuation when they are transmitted in optical fibers. Through physical experiments, it is found that the optical cable has less loss and less dispersion when the light is in the three wavelength ranges. The three wavelengths are about 850nm, about 1310nm and about 1550nm respectively. Therefore, the wavelengths near these three wavelengths are generally used as the wavelengths used for communication, and the area with low fiber attenuation is generally called the optical communication window.

Optical wavelength division multiplexing (WDM) is to combine a series of optical carriers carrying information in the optical frequency domain at a wavelength interval of 1 to several hundred nanometers, and transmit them along a single optical fiber; at the receiving end, a certain method is used to , A communication method that separates optical carriers of different wavelengths. Optical wavelength division multiplexing technology generally uses a wavelength division multiplexer (also called a multiplexer) and a demultiplexer (also called a demultiplexer) to be placed at both ends of the optical fiber to realize the coupling and separation of different light waves. This communication system is called an optical communication wavelength division multiplexing system.

Optical thin films are a class of optical dielectric materials that are composed of thin layered media and transmit light beams through the interface. Optical thin-film devices mainly include reflective films, anti-reflective films, polarizing films, interference filters, and beam splitters. The simplest optical thin film model is a smooth, isotropic homogeneous dielectric thin layer. In this case, the optical properties of optical thin films can be studied using the interference theory of light. When a monochromatic plane wave is incident on an optical film, multiple reflections and refractions occur on its two surfaces, the directions of the reflected light and refracted light are given by the laws of reflection and refraction, and the amplitudes of the reflected light and refracted light is determined by the Fresnel formula.

The dispersion of light refers to the phenomenon that polychromatic light is decomposed into monochromatic light; the phenomenon that polychromatic light is decomposed into monochromatic light through a prism; the phenomenon of light pulse broadening caused by different group velocities of different frequencies in the spectral components of the light source in optical fibers. Dispersion is also a description of the relationship between a propagation parameter and frequency of an optical fiber. In 1666, Newton first observed the dispersion of light with a prism, decomposing white light into colored light bands (spectrum). The dispersion phenomenon shows that the speed v of light in the medium (v=c/n, n represents the refractive index of the medium) changes with the frequency f of the light. Dispersion of light can be achieved with prisms, diffraction gratings and interferometers.

A commonly used optical wavelength division multiplexing technology solution is to use a diffraction grating (such as a reflection grating, a transmission grating) to separate light of different wavelengths in space. There are parallel cracks or grooves arranged at equal intervals on the diffraction grating, and the spacing is similar to the wavelength of light. After the light is incident, the angle of leaving the diffraction grating is related to the wavelength and fanned out, so as to realize the spatial separation of light of different wavelengths. However, for light with relatively close wavelengths, the distance or angle that the diffraction grating separates them in space is small.

Contents of the invention

Based on this, it is necessary to provide a spectroscopic film, a selective spectroscopic mirror, an optical device and a spectroscopic method to solve the problem that it is difficult to spatially separate light of different wavelength bands at a large angle.

One of the objectives of the present invention is to provide a spectroscopic film for the splitting of light with a wavelength of 850nm and light with a wavelength of 1550nm. The scheme is as follows:

A light-splitting film, the light-splitting film comprises a first silicon dioxide layer, a first silicon nitride layer, a second silicon dioxide layer, a second silicon nitride layer, a third silicon dioxide layer, a first a silicon trinitride layer, a fourth silicon dioxide layer, a fourth silicon nitride layer, a fifth silicon dioxide layer and a fifth silicon nitride layer.

Compared with existing schemes, the above-mentioned spectroscopic film has the following beneficial effects:

The above-mentioned spectroscopic film has high reflectivity for 850nm light and high transmittance for 1550nm light by setting alternately stacked silicon dioxide film layers and silicon nitride film layers, and has high transmittance for light with wavelengths of 850nm and 1550nm The light is highly selective and can be used to spatially separate the two wavelengths of light. When the optical communication system uses two kinds of light with wavelengths of 850nm and 1550nm to transmit in the same optical path at the same time, the above-mentioned spectroscopic film can separate the two kinds of light of 850nm and 1550nm in the receiving section, which is beneficial to the back-end receiver. Separately identify signals loaded on beams of different wavelength bands.

In one embodiment, the thickness of the first silicon dioxide layer is 318nm-323nm, the thickness of the first silicon nitride layer is 343nm-349nm, and the thickness of the second silicon dioxide layer is 158nm-323nm. 163nm, the thickness of the second silicon nitride layer is 107nm-112nm, the thickness of the third silicon dioxide layer is 172nm-177nm, the thickness of the third silicon nitride layer is 114nm-119nm, and the thickness of the third silicon nitride layer is 114nm-119nm. The thickness of the fourth silicon dioxide layer is 162nm-167nm, the thickness of the fourth silicon nitride layer is 104nm-109nm, the thickness of the fifth silicon dioxide layer is 167nm-172nm, the fifth silicon nitride layer The thickness is 116nm ~ 121nm.

In one embodiment, the thickness of the first silicon dioxide layer is 320nm-321nm, the thickness of the first silicon nitride layer is 345nm-346nm, and the thickness of the second silicon dioxide layer is 160nm-321nm. 161nm, the thickness of the second silicon nitride layer is 109nm-110nm, the thickness of the third silicon dioxide layer is 174nm-175nm, the thickness of the third silicon nitride layer is 116nm-117nm, and the thickness of the third silicon nitride layer is 116nm-117nm. The thickness of the fourth silicon dioxide layer is 164nm-165nm, the thickness of the fourth silicon nitride layer is 106nm-107nm, the thickness of the fifth silicon dioxide layer is 169nm-170nm, the fifth silicon nitride layer The thickness is 118nm ~ 119nm.

In one of the embodiments, the silicon dioxide film layers and silicon nitride film layers in the light splitting film are prepared by ion-enhanced chemical vapor deposition (PECVD)

Another object of the present invention is to provide a selective spectroscope for the light splitting of the light of 850nm and the light of 1550nm with a wavelength of 850nm, and the scheme is as follows:

A selective dichroic mirror, comprising a lens base and the dichroic film described in any one of the above embodiments, the dichroic film is arranged on the lens base, the first silicon dioxide layer is located on the first silicon nitride The side of the layer close to the lens base.

The above-mentioned selective spectroscopic mirror can be applied to optical communication systems, and it has high reflectivity for 850nm light and high transmittance for 1550nm light by setting alternately stacked silicon dioxide film layers and silicon nitride film layers High selectivity between 850nm and 1550nm wavelengths can be used to spatially separate the two wavelengths of light. When the optical communication system uses two kinds of light with wavelengths of 850nm and 1550nm to transmit in the same optical path at the same time, the above-mentioned selective beam splitter can spatially separate the two kinds of light of 850nm and 1550nm in the receiving section, which is beneficial to the back-end The receivers separately identify the signals loaded on the beams of different wavelength bands.

In one of the embodiments, the selective dichroic mirror further includes an anti-reflection film, the anti-reflection film is arranged on the side of the lens base away from the dichroic film, and the anti-reflection film includes a layered first A silicon hexanitride layer and a sixth silicon dioxide layer.

In one embodiment, the thickness of the sixth silicon nitride layer is 119nm-124nm, and the thickness of the sixth silicon dioxide layer is 342nm-347nm.

In one embodiment, the sixth silicon nitride layer has a thickness of 121 nm to 122 nm, and the sixth silicon dioxide layer has a thickness of 344 nm to 345 nm.

In one embodiment, the silicon dioxide film layer and the silicon nitride film layer in the anti-reflection film are prepared by ion-enhanced chemical vapor deposition (PECVD).

In one of the embodiments, the lens substrate is glass, such as ZF glass or the like.

Yet another object of the present invention is to provide an optical device for the light splitting of light with a wavelength of 850nm and light with a wavelength of 1550nm, the scheme is as follows:

An optical device has the selective beam splitter described in any one of the above embodiments.

The above-mentioned optical device has the above-mentioned selective beam splitter, so corresponding technical effects can be obtained.

In one of the embodiments, the optical device is a demultiplexer or an optical splitter.

Yet another object of the present invention is to provide a spectroscopic method for the spectroscopic separation of light with a wavelength of 850nm and light with a wavelength of 1550nm, the scheme is as follows:

A kind of wavelength is the spectroscopic method of the light of 850nm and 1550nm, comprises the following steps:

The composite beam is split by the selective beam splitter described in any of the above embodiments, and the composite beam is incident on the selective beam splitter from the beam splitting film, and the composite beam contains light with wavelengths of 850nm and 1550nm.

In one of the embodiments, the incident angle of the composite light beam is 44°-46°. In one of the embodiments, the incident angle of the composite light beam is 45°.

Description of drawings

FIG. 1 is a schematic structural view of a light splitting film according to an embodiment of the present invention;

Fig. 2 is the structural representation of the selective spectroscope containing spectroscopic film shown in Fig. 1;

Fig. 3 is the structural representation of anti-reflection coating in the selective beam splitter shown in Fig. 2;

Fig. 4 is a schematic diagram of splitting light with a wavelength of 850nm and light with a wavelength of 1550nm by using the selective beam splitter shown in Fig. 2 .

Explanation of reference signs:

100. Light splitting film; 101. First silicon dioxide layer; 102. First silicon nitride layer; 103. Second silicon dioxide layer; 104. Second silicon nitride layer; 105. Third silicon dioxide layer; 106. The third silicon nitride layer; 107. The fourth silicon dioxide layer; 108. The fourth silicon nitride layer; 109. The fifth silicon dioxide layer; 110. The fifth silicon nitride layer; 10. Selective light splitting mirror; 200, lens substrate; 300, antireflection film; 301, sixth silicon nitride layer; 302, sixth silicon dioxide layer.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the associated drawings. Preferred embodiments of the invention are shown in the accompanying drawings. However, the present invention can be embodied in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

In the description of the present invention, it should be understood that the terms "first", "second" and so on are only used for descriptive purposes, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features . Thus, a feature defined with "first", "second", etc. may expressly or implicitly include at least one of that feature.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Please refer to FIG. 1 , a light splitting film 100 according to an embodiment of the present invention includes silicon dioxide (SiO ₂ ) film layers and silicon nitride (Si ₃ N ₄ ) film layers stacked alternately.

More specifically, the light splitting film 100 includes a first silicon dioxide layer 101, a first silicon nitride layer 102, a second silicon dioxide layer 103, a second silicon nitride layer 104, and a third silicon dioxide layer, which are stacked in sequence. 105 , the third silicon nitride layer 106 , the fourth silicon dioxide layer 107 , the fourth silicon nitride layer 108 , the fifth silicon dioxide layer 109 and the fifth silicon nitride layer 110 .

The above-mentioned spectroscopic film 100 has high reflectance to 850nm light and high transmittance to 1550nm light by setting alternately stacked silicon dioxide film layers and silicon nitride film layers, and has high transmittance to light of 850nm wavelength and Light at 1550 nm is highly selective and can be used to spatially separate the two wavelengths of light. When the optical communication system uses two kinds of light with wavelengths of 850nm and 1550nm to transmit in the same optical path at the same time, the above-mentioned spectroscopic film 100 can spatially separate the two kinds of light of 850nm and 1550nm in the receiving section, which is beneficial to the back-end reception The detectors separately identify the signals loaded on the beams of different wavelength bands.

In one example, the thickness of the first silicon dioxide layer 101 is 318nm-323nm, the thickness of the first silicon nitride layer 102 is 343nm-349nm, the thickness of the second silicon dioxide layer 103 is 158nm-163nm, the second The thickness of silicon nitride is 107nm～112nm, the thickness of the third silicon dioxide layer 105 is 172nm～177nm, the thickness of the third silicon nitride layer 106 is 114nm～119nm, the thickness of the fourth silicon dioxide layer 107 is 162nm～ The thickness of the fourth silicon nitride layer 108 is 104nm-109nm, the thickness of the fifth silicon dioxide layer 109 is 167nm-172nm, and the thickness of the fifth silicon nitride layer 110 is 116nm-121nm.

The selective beam splitter 10 in the above example further optimizes the thickness range of each film layer, so that the angle between the two beams of light after separation can reach more than 85°, thereby improving the light splitting effect.

In one example, the thickness of the first silicon dioxide layer 101 is 320nm-322nm, the thickness of the first silicon nitride layer 102 is 345nm-347nm, the thickness of the second silicon dioxide layer 103 is 160nm-162nm, the second The thickness of silicon nitride is 108nm～110nm, the thickness of the third silicon dioxide layer 105 is 173nm～175nm, the thickness of the third silicon nitride layer 106 is 116nm～118nm, the thickness of the fourth silicon dioxide layer 107 is 163nm～ The thickness of the fourth silicon nitride layer 108 is 105nm-107nm, the thickness of the fifth silicon dioxide layer 109 is 169nm-171nm, and the thickness of the fifth silicon nitride layer 110 is 118nm-120nm.

The selective beam splitter 10 in the above example further optimizes the thickness range of each film layer, so that the angle between the two beams of light after separation reaches 90°, thereby improving the light splitting effect.

Each silicon dioxide film layer and silicon nitride film layer in the above-mentioned spectroscopic film 100 can be fabricated by coating, vapor deposition, and other methods. In one example, the silicon dioxide film layers and the silicon nitride film layers in the spectroscopic film 100 are prepared by ion-enhanced chemical vapor deposition (PECVD).

Further, as shown in FIG. 2 , the present invention also provides a selective dichroic mirror 10, which includes a lens base 200 and a dichroic film 100 of any of the above examples. The dichroic film 100 is arranged on the lens base 200, and the first dioxide The silicon layer 101 is located on a side of the first silicon nitride layer 102 close to the lens base 200 .

The above-mentioned selective beam splitter 10 can be applied in an optical communication system. By setting alternately stacked silicon dioxide film layers and silicon nitride film layers, it has a high reflectivity for 850nm light and a high reflectivity for 1550nm light. Transmittance, with high selectivity for light at wavelengths of 850nm and 1550nm, can be used to spatially separate the two wavelengths of light. When the optical communication system uses two kinds of light with wavelengths of 850nm and 1550nm to transmit in the same optical path, the above-mentioned selective beam splitter 10 can spatially separate the two kinds of light of 850nm and 1550nm in the receiving section, which is beneficial to the future The end receivers respectively identify the signals loaded on the beams of different wavelength bands.

As shown in FIG. 3 , in one example, the selective beam splitter 10 further includes an antireflection film 300 . The anti-reflection film 300 is disposed on the side of the lens base 200 away from the dichroic film 100 . The anti-reflection film 300 is used to increase the transmittance of 1550nm light.

Optionally, the lens base 200 may be, but not limited to, glass, such as ZF glass.

In one example, the antireflection film 300 includes a sixth silicon nitride layer 301 and a sixth silicon dioxide layer 302 stacked, and the sixth silicon nitride layer 301 is disposed on the sixth silicon dioxide layer 302 close to the lens substrate. 200 on one side.

In one example, the sixth silicon nitride layer 301 has a thickness of 119nm-124nm, and the sixth silicon dioxide layer 302 has a thickness of 342nm-347nm.

The above-mentioned selective beam splitter 10 optimizes the thickness ranges of the sixth silicon nitride layer 301 and the sixth silicon dioxide layer 302 in the anti-reflection film 300 , so that the anti-reflection film 300 has a higher transmittance for light of 1550 nm.

Further, in one example, the thickness of the sixth silicon nitride layer 301 is 121 nm˜122 nm, and the thickness of the sixth silicon dioxide layer 302 is 344 nm˜345 nm.

The above-mentioned selective beam splitter 10 optimizes the thickness ranges of the sixth silicon nitride layer 301 and the sixth silicon dioxide layer 302 in the anti-reflection film 300 , so that the anti-reflection film 300 has a higher transmittance for light of 1550 nm.

Each silicon dioxide film layer and silicon nitride film layer in the above-mentioned anti-reflection film 300 can be formed by coating, vapor deposition, and other methods. In one example, the silicon dioxide film layers and the silicon nitride film layers in the anti-reflection film 300 are prepared by ion-enhanced chemical vapor deposition (PECVD).

The preparation method of the selective beam splitter 10 of an example comprises the following steps:

In step 1, the lens base 200 is obtained. The lens base 200 is a sheet structure, which has a first side and a second side opposite to each other.

Step 2, using the ion-enhanced chemical vapor deposition method, sequentially deposit the first silicon dioxide layer 101, the first silicon nitride layer 102, the second silicon dioxide layer 103, and the second nitrogen oxide layer on the first side surface of the lens substrate 200. Silicon oxide layer 104, third silicon dioxide layer 105, third silicon nitride layer 106, fourth silicon dioxide layer 107, fourth silicon nitride layer 108, fifth silicon dioxide layer 109 and fifth silicon nitride layer Layer 110.

In step 3, a sixth silicon nitride layer 301 and a sixth silicon dioxide layer 302 are sequentially deposited on the second side surface of the lens substrate 200 by using an ion-enhanced chemical vapor deposition method.

Further, the present invention also provides an optical device, which has the selective beam splitter 10 of any one of the above examples.

The above-mentioned optical device has the above-mentioned selective beam splitter 10, so corresponding technical effects can be obtained.

Optical devices may be, but are not limited to, demultiplexers, optical splitters, and the like.

The present invention also provides a spectroscopic method for light with a wavelength of 850nm and 1550nm, comprising the following steps:

The composite beam is split by the selective beam splitter 10 of any example above, and the composite beam is incident on the selective beam splitter 10 from the beam splitting film 100, and the composite beam contains light with wavelengths of 850nm and 1550nm.

In one example, the incident angle of the composite light beam is 44°-46°.

Further, in one example, the incident angle of the composite light beam is 45°.

Specific examples are provided below to further illustrate the present invention. But the present invention is not limited to the following embodiments, it should be understood that the scope of the present invention is summarized by the appended claims. Certain changes will be covered by the spirit and scope of the claims of the present invention.

Example 1

The selective dichroic mirror in this embodiment includes a lens base, a dichroic film and an anti-reflection film.

Wherein, the lens substrate is a ZF glass sheet. The light splitting film includes a first silicon dioxide layer, a first silicon nitride, a second silicon dioxide layer, a second silicon nitride, a third silicon dioxide layer, a third silicon nitride, and a fourth silicon dioxide layer stacked in sequence. a silicon layer, a fourth silicon nitride, a fifth silicon dioxide layer and a fifth silicon nitride. The first silicon dioxide layer is located on the side of the first silicon nitride close to the lens base. The structural parameters of the spectroscopic film are shown in Table 1. The anti-reflection film is arranged on the side of the lens base away from the beam splitting film, the anti-reflection film includes a sixth silicon nitride layer and a sixth silicon dioxide layer stacked, and the sixth silicon nitride layer is arranged on the sixth silicon dioxide layer The side close to the lens base. The structural parameters of the AR coating are shown in Table 2.

Table 1 Structural parameters of selective spectroscopic film

film layer Material Thickness parameter Film thickness (nm) first silicon dioxide layer SiO ₂ d ₁ 321 first silicon nitride layer Si ₃ N ₄ d ₂ 346 second silicon dioxide layer SiO ₂ d ₃ 161 second silicon nitride layer Si ₃ N ₄ d ₄ 109 third silicon dioxide layer SiO ₂ d ₅ 174 third silicon nitride layer Si ₃ N ₄ d ₆ 117 fourth silicon dioxide layer SiO ₂ d ₇ 164 fourth silicon nitride layer Si ₃ N ₄ d ₈ 106 fifth silicon dioxide layer SiO ₂ d ₉ 170 fifth silicon nitride layer Si ₃ N ₄ d ₁₀ 119

Table 2 Structural parameters of AR coating

When the incident light is incident at an angle of 45°, the selective beamsplitter has 73.6% of the TM wave (transverse magnetic wave, also called p-polarized wave) and TE wave (transverse electric wave, also called s-polarized wave) of 850nm light, respectively. and 94.6% reflectivity; 99.0% and 99.6% transmittance for TM wave and TE wave of 1550nm light, respectively. If the incident light is circularly polarized light (laser light used in optical communication can be regarded as circularly polarized light), then the reflectance of the selective beamsplitter provided by embodiment 2 to 850nm light can be 84.1%, and the reflectance of 1550nm light can be obtained by calculation. The transmittance is 99.3%, and it has strong selectivity to 850nm and 1550nm light.

Example 2

The selective dichroic mirror in this embodiment includes a lens base, a dichroic film and an anti-reflection film.

Wherein, the lens substrate is a ZF glass sheet. The light splitting film includes a first silicon dioxide layer, a first silicon nitride, a second silicon dioxide layer, a second silicon nitride, a third silicon dioxide layer, a third silicon nitride, and a fourth silicon dioxide layer stacked in sequence. a silicon layer, a fourth silicon nitride, a fifth silicon dioxide layer and a fifth silicon nitride. The first silicon dioxide layer is located on the side of the first silicon nitride close to the lens base. The structural parameters of the spectroscopic film are shown in Table 3. The anti-reflection film is arranged on the side of the lens base away from the beam splitting film, the anti-reflection film includes a sixth silicon nitride layer and a sixth silicon dioxide layer stacked, and the sixth silicon nitride layer is arranged on the sixth silicon dioxide layer The side close to the lens base. The structural parameters of the AR coating are shown in Table 4.

Table 3 Structural parameters of selective spectroscopic film

Table 4 Structural parameters of AR coating

film layer Material Thickness parameter Film thickness (nm) Sixth silicon nitride layer Si ₃ N ₄ d ₁₁ 120 sixth silicon dioxide layer SiO ₂ d ₁₂ 343

When the incident light is incident at an angle of 45°, the selective beamsplitter has 73.5% of the TM wave (transverse magnetic wave, also called p-polarized wave) and TE wave (transverse electric wave, also called s-polarized wave) of 850nm light, respectively. and 94.6% reflectivity; 99.6% and 99.8% transmittance for TM wave and TE wave of 1550nm light, respectively.

If the incident light is circularly polarized light (laser light used in optical communication can be regarded as circularly polarized light), then the reflectance of the selective beamsplitter provided by embodiment 2 to 850nm light can be 84.1%, and the reflectance of 1550nm light can be obtained by calculation. The transmittance is 99.7%, and it has strong selectivity to 850nm and 1550nm light.

When the incident light is incident at an angle of 44°, the selective beamsplitter has 74.5% of the TM wave (transverse magnetic wave, also called p-polarized wave) and TE wave (transverse electric wave, also called s-polarized wave) of 850nm light, respectively. and 94.4% reflectivity; 99.6% and 99.8% transmittance for TM wave and TE wave of 1550nm light, respectively. If the incident light is circularly polarized light (laser light used in optical communication can be regarded as circularly polarized light), then the reflectance of the selective beamsplitter provided by embodiment 2 to 850nm light can be 84.4%, and the reflectivity of 1550nm light can be obtained by calculation. The transmittance is 99.7%, and it has strong selectivity to 850nm and 1550nm light. The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the patent scope of the invention. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (10)

1. The light splitting film is characterized by comprising a first silicon dioxide layer, a first silicon nitride layer, a second silicon dioxide layer, a second silicon nitride layer, a third silicon dioxide layer, a third silicon nitride layer, a fourth silicon dioxide layer, a fourth silicon nitride layer, a fifth silicon dioxide layer and a fifth silicon nitride layer which are sequentially stacked, wherein the thickness of the first silicon dioxide layer is 318 nm-323 nm, the thickness of the first silicon nitride layer is 343 nm-349 nm, the thickness of the second silicon dioxide layer is 158 nm-163 nm, the thickness of the second silicon nitride layer is 107 nm-112 nm, the thickness of the third silicon dioxide layer is 172 nm-177 nm, the thickness of the third silicon nitride layer is 114 nm-119 nm, the thickness of the fourth silicon dioxide layer is 162 nm-167 nm, the thickness of the fourth silicon nitride layer is 104 nm-109 nm, the thickness of the fifth silicon dioxide layer is 167 nm-172 nm, and the thickness of the fifth silicon nitride layer is 116 nm-121 nm.

2. The spectroscopic film of claim 1, wherein the first silicon dioxide layer has a thickness of 320nm to 321nm, the first silicon nitride layer has a thickness of 345nm to 346nm, the second silicon dioxide layer has a thickness of 160nm to 161nm, the second silicon nitride layer has a thickness of 109nm to 110nm, the third silicon dioxide layer has a thickness of 174nm to 175nm, the third silicon nitride layer has a thickness of 116nm to 117nm, the fourth silicon dioxide layer has a thickness of 164nm to 165nm, the fourth silicon nitride layer has a thickness of 106nm to 107nm, the fifth silicon dioxide layer has a thickness of 169nm to 170nm, and the fifth silicon nitride layer has a thickness of 118nm to 119nm.

3. A selective beam splitter comprising a lens substrate and a beam splitting film according to claim 1 or 2, wherein the beam splitting film is disposed on the lens substrate, and the first silicon dioxide layer is located on a side of the first silicon nitride layer adjacent to the lens substrate.

4. A selective beam splitter as recited in claim 3, further comprising an anti-reflection film disposed on a side of the lens substrate remote from the beam splitting film, the anti-reflection film comprising a sixth silicon nitride layer and a sixth silicon dioxide layer disposed in a stack, the sixth silicon nitride layer disposed on a side of the sixth silicon dioxide layer proximate to the lens substrate.

5. A selective beam splitter according to claim 4 wherein the thickness of said sixth silicon nitride layer is 119nm to 124nm and the thickness of said sixth silicon dioxide layer is 342nm to 347nm.

6. A selective beam splitter according to claim 5 wherein the thickness of said sixth silicon nitride layer is 121nm to 122nm and the thickness of said sixth silicon dioxide layer is 344nm to 345nm.

7. A selective beam splitter according to claim 3 wherein said lens substrate is glass.

8. An optical device having a selective beam splitter as claimed in any one of claims 4 to 7.

9. The optical device of claim 8, wherein the optical device is a demultiplexer or a beam splitter.

10. A method of splitting light having wavelengths of 850nm and 1550nm, comprising the steps of:

splitting a composite beam of light using a selective beam splitter as claimed in any one of claims 4 to 7, the composite beam of light being incident on the selective beam splitter from the splitting film, the composite beam of light containing light having wavelengths of 850nm and 1550 nm.

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