JPS59216110A - Polarized beam splitter - Google Patents

Abstract

PURPOSE:To obtain a polarized beam splitter which prevents variation in the transmittivity of a P wave by providing an intermediate layer which has an intermediate refractive index between the 1st and the 2nd dielectric multilayered films formed by laminating a material with a high refractive index and a material with a low refractive index alternately. CONSTITUTION:The intermediate layer 6 made of a dielectric material having the intermediate refractive index is formed on the reflecting surface of a prism between the 1st dielectric multilayered film 7 and the 2nd dielectric multilayered film 8 which are formed by laminating the layer (H layer) 4 made of the high refractive index material and the layer (L layer) 5 made of the low refractive index material alternately, and the other prism is joined with an adhesive. Thus, the polarized beam splitter which decreases the reflection factor of the P wave and prevents its variation is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polarizing beam splitter, and particularly to a multilayer film made of a substantially translucent dielectric material (hereinafter referred to as a "dielectric multilayer film"). ).

Generally, a cubic polarizing beam splitter with an optical thin film has a structure as shown in FIG. That is, 1 and 2 are triangular prism glass substrates, and 3 is a dielectric multilayer film sandwiched between the triangular prism glass substrates 1 and 2. As shown in FIG. 2, this polarizing beam splitter has a dielectric multilayer film 3 that transmits P waves and reflects S waves.
Separate waves and S waves.

Conventionally, this type of polarizing beam splitter has had a dielectric multilayer film as shown in FIG. That is, 4 is zinc sulfide (
A layer (hereinafter referred to as "H layer") of a high refractive index material such as a material having a refractive index of 2.29. ), 5 is cryolite (refractive index is 1
．． A layer of a low refractive index material (hereinafter referred to as “L layer”) such as
That's what it means. ), and the 11 layers 4 and the above layers 5 are alternately laminated to form 23 layers (only 7 layers are shown in FIG. 1).
The layers at both ends of the dielectric multilayer film were the H layer 4.

The dielectric multilayer film is formed by first depositing 8 layers 4 on the hypotenuse surface of the triangular prism glass substrate 1 or 2 (hereinafter referred to as the "slope") by vacuum evaporation, and then depositing 8 layers 4 on the triangular prism glass substrate 1 or 2.
The 1-1 layers 4 were alternately laminated by vacuum evaporation or the like, and the final H layer 5 was laminated, and then adhered to the slope of the glass of the other triangular prism using an optical bond to create a polarizing prism.

In conventional polarizing beam splitters, in order to separate the incident light into P waves and S waves with high efficiency, the film structure of the dielectric multilayer film has the lowest reflectance for the P wave of human QJ light and the lowest reflectance for the S wave. The wavelength was appropriately selected so that the wavelength of the incident light was included in the wavelength range with high reflectance.

Nevertheless, the P-wave reflectance of the conventional polarized beam splinter shown at A in FIG. 6 for the @e-Ne laser does not necessarily have a minimum value near the desired wavelength of 633 nm. It may not be shown. That is,
In a conventional polarized beam splinter, Δλ=620-65
In the wavelength range of 0 nm, it is desirable that the reflectance is almost zero regardless of the wavelength, but within the wavelength range Δλ, there is a maximum of 4% reflection of P waves, and the reflectance of the P waves is There was a drawback that it fluctuated by about 3%.

As a result, the manufacturing yield of a polarizing beam splitter for a desired wavelength deteriorates, and the P-wave reflection characteristics change even if the angle of incidence of the incident light deviates slightly. The dielectric multilayer film 3 includes a first dielectric multilayer film and a second dielectric multilayer film in which H layers and L layers are alternately laminated; An intermediate layer of dielectric material is provided between the first dielectric multilayer film and the second dielectric multilayer film to reduce the reflectance of P waves in a wavelength range including the wavelength of the incident light, and The object of the present invention is to provide a polarizing beam splitter that significantly prevents fluctuations in wave reflectance.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

(Example 1) This will be explained based on FIG. 4. 4 is the H layer (
For example, a layer of zinc sulfide. ), 5 is an L layer (for example, Cryolite 1~), and 6 is a dielectric material layer having an intermediate refractive index between the above-mentioned 1-1 layer 4 and the above-mentioned layer 5 (for example, "Refractive index 1");
．． 46 layers of silicon dioxide. Hereinafter, it will be referred to as the M layer. ), 7
is the first dielectric multilayer film, and the 1-1 layer 4 (II number is 6
layer) and the above-mentioned layer 5 (the number of layers is 5 layers) are laminated alternately to form 11 layers, both ends of which are the above-mentioned H layer 4, and the above-mentioned 1'' layer 4 at one of both ends is the above-mentioned M layer 6. The other 1-11 m 4, which is in contact with one surface and at both ends thereof, is attached to the slope of a triangular prism glass as shown in 1 in FIG. 8 is
The second dielectric multilayer film has substantially the same structure as the first dielectric multilayer film 7, and the 1'' layer 4 at one of its ends is different from the first dielectric multilayer film 7. In contact with the surface opposite to one surface of the M layer 6 in contact with the other 8 at both ends thereof.
The layer 4 is bonded to the slope of the triangular prism glass as shown in 2 in FIG. 1 with an optical bond (for example, 3021, manufactured by Sumitomo 3M Ltd., trade name). The above layer 5,
The H layer 4 and the M layer 6 were laminated by vacuum evaporation. Further, the thickness of each layer is as follows: the thickness of the above layer 5 and the above M layer 6 is optical II! The thickness is λ/4 (λ: wavelength of incident light,
In this example, the incident light is a 633 nm laser beam.

Same below. ). In the 1-1 layer 4, the I'' layer 4 adhering to the optical bond and the 14 layer 4 adhering to the slope of the glass of the triangular prism are λ/8, and the other +'' layer 4 is λ/8.
It is 4. The reflectance of the P wave according to this example is a curve as shown in FIG.
The maximum reflectance was 1%, and the variation in reflectance was also about 1%.

(Example 2) This will be explained based on FIG. 5. 4°6 is
The same material and the same layer as in Example 1 are used.

5 is L layer (for example, thiolite, refractive index is 1.33)
, 7 is a first dielectric multilayer film, in which the 1-1 layer 4 (the number of layers is 5) and the above-mentioned layer 5 (the number of layers is 5) are laminated alternately.
One layer of the 14 layers is in contact with one surface of the M layer 6. Reference numeral 8 denotes a second dielectric multilayer film, which has the same structure as the first dielectric multilayer film, and one layer of the H layer is a second dielectric multilayer film.
It is in contact with the other surface of layer 6. The H layer 4, the M layer 6, and the above layer 5 are each laminated by a vacuum evaporation method to form the first dielectric multilayer It! 7 or the M layer 6 of the second dielectric multilayer film 8. One layer 5 at the side is attached to the slope of the glass of the triangular prism shown in FIG.
1. Sumitomo 3M Ltd. 1 company, product name. ) to adhere to the slope of the glass of the triangular prism shown in 1 or 2 of FIG. The H layer 4 and the M layer 6 have an optical thickness of λ/4,
Among the layers 5, one layer 5 attached or bonded to the triangular prism glass 1 or 2 has an optical thickness of λ/10, and the other layer 5 has an optical thickness of λ/4.

As described above, in Examples 1 and 2, the first dielectric layer, which is attached to a substrate such as glass, and the second dielectric layer, which is attached to an optical bond, are made of a substance having the same refractive index. However, this was done so that the light could be incident from any one of the substrates 1 and 2, such as triangular prism glass in Fig. 1, and there is no need to limit the incidence to materials having the same refractive index. do not have. Preferably, the two layers have the same refractive index.

Next, in Examples 1 and 2, zinc sulfide was used for the H layer 4, cryolite (or thiolite) was used for the H layer 4, and silicon dioxide was used for the MIS, but the H layer 4 was not limited thereto. Titanium, tantalum pentoxide, zirconium dioxide, etc., 11!15 may be selected from magnesium fluoride, etc., and M layer 6 may be selected from cerium fluoride, alumina, etc. and combined.

That is, the refractive index is relatively high refractive index, low refractive index, and
A material having a refractive index intermediate between these refractive indexes and having substantially light-transmitting dielectric properties may be used in combination. Next, in Examples 1 and 2, the H layers 4, 1 and 5 were formed of the same material, but the same effect is obtained even if materials having substantially the same refractive index are used. There is. Next, in Examples 1 and 2, the first dielectric multilayer film and the second dielectric multilayer film have the same number of layers, but they may be different.

Desirably, the first dielectric multilayer film and the second dielectric multilayer film have the same number of layers or a difference in the number of layers of 1 to 3 layers. Furthermore, the optical thickness of one layer or M layers to be adhered or adhered to a triangular prism-shaped substrate such as glass is preferably from λ/6 to λ/12.

As described above, according to the present invention, it is possible to further reduce the reflectance of P waves in the wavelength range that includes the desired incident light, and also to reduce the fluctuations in the reflectance. A polarizing beam splitter that is effective in preventing this was obtained.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a general polarizing beam splitter, and Figure 2 is a perspective view of a general polarizing beam splitter.
The figure is a schematic diagram showing the relationship between the plan view of FIG. 1 and the incident light, P waves, and S waves, FIG. 3 is a cross-sectional view of a conventional dielectric multilayer film, and FIG. 4 is a diagram showing the relationship between the incident light, P waves, and S waves. A cross-sectional view showing one embodiment of the dielectric multilayer film, FIG. 5 is a cross-sectional view showing another example of the dielectric multilayer film used in the present invention, and FIG. 6 shows the relationship between wavelength and P-wave reflectance. Diagram showing. 1.2... Base of polarizing beam splitter, 3... Dielectric multilayer film, 4... H layer, 5... L layer, 6... M
Layer, 7...First dielectric multilayer film, 8...Second dielectric multilayer film Figure 3 Figure 4 Figure 5 Figure 6 Procedure Correction (Spontaneous) 1. Display of the case: 1981 Special Edition Application No. 9167192, Title of the invention: Person who corrects polarizing beam splitter 3° Relationship to the case: 11 Applicant Address: 1-13-12 Nishi-Shinjuku, Shinjuku-ku, Tokyo 160
Address: 03 (348) 1221 Hoya Glass Name Hoya Glass Co., Ltd. Correct the text to read "Last 1-1 layer 4." (2) In the 8th line of page 9 of the specification M, amend "or M layer" to "1 or 1 layer". νHuman-

Claims (1)

[Scope of Claims] (1) In a polarizing beam splitter comprising a first substrate, a dielectric multilayer film, and a second substrate, the dielectric multilayer film includes a first dielectric multilayer film, an intermediate layer, a second dielectric multilayer film, and a second substrate. dielectric multilayer films are sequentially laminated, and the first dielectric multilayer film and the second dielectric multilayer film are made of alternately a high refractive index material and a low refractive index material each having substantially light-transmitting properties. The intermediate layer is a substantially translucent material having a refractive index intermediate between the high refractive index material and the low refractive index material, and the layers in contact with both the front and back surfaces of the intermediate layer are high refractive index materials. A polarizing beam splitter characterized by being made of a refractive index material. (2. J3 in Claim 1, except for each dielectric layer of the first dielectric multilayer film and the second dielectric multilayer film that is farthest from the intermediate layer) a dielectric layer constituting a dielectric multilayer film and the second dielectric multilayer film;
The intermediate layer has an optical film thickness of substantially '! /4(λ
: Wavelength of incident light. ) A polarizing beam splitter characterized by: (3) In claim 1 or 2, each dielectric layer of the first dielectric multilayer film and the second dielectric multilayer film that is farthest from the intermediate layer is made of the same material. A polarizing beam splitter characterized by: