JPH06308326A - Polarizer and its production - Google Patents

Abstract

PURPOSE:To provide the polarizer having excellent mass productivity and good characteristics and the process for production of this polarizer. CONSTITUTION:This polarizer 6 consists of an optical element 3, double refractive materials 1 which is joined onto the surface of this element via an adhesive 2 interposed therebetween, has refractive indices nB1, nB2 and a thickness dB and satisfies (nB1-nB2)dB=(M+1/2)lambda (M is an arbitrary integer, lambda is the wavelength of light), grooves of specified intervals formed on the double refractive materials 1 at the depth arriving at the optical element and a packing material 5 packed into these grooves. The refractive indices of the optical element 3, the adhesive 2 and one of the double refractive materials and the refractive index of the packing material are set nearly constant. As a result, the precise polishing of only the thickness of the double refractive materials 1 suffices and the permissible accuracy of the other working is low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizer excellent in mass production, which is an alternative to conventional polarizers, and has excellent characteristics, and a method for manufacturing the same. The present invention also relates to various optical elements such as an optical isolator to which the polarizer of the present invention is attached.

[0002]

2. Description of the Related Art Conventionally, the following various types of polarizers have been known as a polarizer. (1) Dichroic polarizer called so-called poloid plate: It has been difficult to use it for precise optical parts such as optical isolators because of its low extinction ratio and large loss. (2) Birefringent polarizer: a material such as quartz, calcite, magnesium fluoride, or other birefringent material, which must be cut out at a predetermined angle with respect to the crystal axis to be processed into a prism or the like. It was expensive and not easy to manufacture. Further, when forming an optical isolator, an optical circulator, an optical modulator, and an optical switch using such a polarizer, the polarizer and other components, for example, a Faraday rotator and the like must be manufactured separately. However, there is a problem that it is difficult to miniaturize the final product because they are used in combination. For example, in the conventionally used optical isolator, it is necessary to arrange the Faraday element with a pair of polarizers whose transmission axes are inclined by 45 °, and an expensive element such as a polarizing prism is used as the polarizer. I was using it. (3) Polarizing glass: It has excellent characteristics and can be made thin, but it is difficult to manufacture and expensive. (4) Diffraction grating type polarizer: A diffraction grating type polarizer manufactured by proton exchange with LiNbO ₃ is known as a polarizer utilizing a diffraction phenomenon (Japanese Patent Laid-Open No. 63-55501). This polarizer is thin and has mass productivity. However, it is necessary to use an expensive single crystal substrate of LiNbO _{3, and} a polarizer must be manufactured separately from other optical elements as in the conventional case, and it is not possible to downsize the entire optical device. However, it is necessary to control the phase difference of orthogonally polarized light with high accuracy, and it is difficult to stably manufacture with good reproducibility. (5) Birefringent diffraction grating type polarizer (Japanese Patent Application No. 4-1489)
51): Diffraction grating in which first sections formed by laminating film materials of one or more layers and second sections formed by laminating film materials of one or more layers are alternately provided on the same surface. Have a structure,
A polarizer in which at least one layer film material of at least one section has birefringence and the birefringent film is formed by an oblique vapor deposition method. However, it is necessary to control the phase difference of orthogonally polarized light with high precision, and it is difficult to stably manufacture with good reproducibility. (6) Birefringent crystal plate: having a function of selecting one polarization by shifting the beam of one polarization,
To use in a parallel beam system, it is necessary to increase the thickness. (7) Birefringent diffraction grating type polarizer (JP-A-2-1562)
No. 05): A dielectric layer is provided on the bottom of a periodic groove provided on the main surface of a crystal plate having optical anisotropy, but the depth of the groove and the thickness of the dielectric layer Precise control is difficult. The present invention relates to improvements in this type of polarizer.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The birefringent diffraction grating type polarizer described in No. 5 requires precise control because the bottom of the periodic grooves provided on the main surface of the crystal plate must be filled with a dielectric layer with a precise thickness. Is difficult,
Inferior in mass productivity. The present invention is to provide an excellent birefringent diffraction grating type polarizer that solves these problems, and a method for producing the same.

[0004]

Means for Solving the Problems That is, the present invention provides (1) an optical element and refractive indices n _B1 , n _B2, and thicknesses for two unique linearly polarized lights that are bonded to the surface of the optical element with an adhesive. and has a _{d B (n B1 -n B2)} d B = (M + 1 /
2) a birefringent material satisfying λ (where M is an arbitrary integer, λ is a wavelength of light), grooves provided at constant depths in the birefringent material to reach the optical element plate, and the grooves. And a filling agent, further comprising the optical element, an adhesive,
Provided is a polarizing element in which the refractive index of one of the birefringent materials and the refractive index of the filler are set to be substantially the same.

According to this structure, since one unique linearly polarized light has the same refractive index n in all regions, it travels straight without loss without diffraction, and the other unique linearly polarized light is birefringent material and filler. When passing through, the half-wave phase shifts, so all diffract and do not go straight.

(2) Such a polarizer has a refractive index n _B1 , n _B2 for two unique linearly polarized lights and a thickness d _B on the surface of the optical element through an adhesive and (n _B1 −
n _B2 ) d _B = (M + 1/2) λ (where M is an arbitrary integer, λ is the wavelength of light), and a birefringent material is bonded to the birefringent material to reach the optical element plate. And forming a groove at a constant interval by filling the groove with a filler, further, the optical element, the adhesive and the filler, the refractive index is substantially the same as one of the refractive index of the birefringent material. Is manufactured by the manufacturing method. The thickness d _B of the birefringent material is prepared by polishing the birefringent material in advance to prepare a half-wave plate that satisfies the above equation, or by polishing the birefringent material after bonding it to an optical element. It can be adjusted by either satisfying a similar relationship.

(3) The polarizer of the present invention can be used as a constituent element of various optical devices, and can be used, for example, in an optical isolator in combination with other optical elements such as a Faraday rotator. In addition, Japanese Patent Application No. 3-35810
Various uses such as use as a polarizer in an optical isolator having no polarization dependence as described in No. 7 are possible. In this case, if the filling material of the groove is made of an adhesive, and the adhesive is applied even to the entire surface of the polarizer and another optical element is bonded thereon, the device becomes compact.

[0008]

In the above-mentioned method of Japanese Patent Laid-Open No. 2-156205, a plurality of periodic grooves are formed on a birefringent crystal plate and a dielectric layer is provided on the groove bottom. Precise control of the depth and the thickness of the dielectric layer is difficult. In the present invention, only the entire thickness of the birefringent material needs to be precisely manufactured, and the groove processing of the birefringent material is sufficient as long as the through groove can be formed. Therefore, it is not necessary to precisely control the groove depth as in the above publication. Further, since the refractive index is set to be the same for one of the peculiar linearly polarized lights, even if the surface of the groove is roughened, the straight traveling light is not scattered.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an example of the structure of the polarizer of the present invention and an example of the manufacturing method thereof will be described in detail with reference to the drawings. Step 1 First, as shown in FIG. 1, a birefringent material 1 having refractive indices n _B1 and n _B2 for two unique linearly polarized lights is prepared. next,
By polishing this birefringent material, (n _B1 −n _B2 ) d _B = (M
+1/2) λ (where M is an arbitrary integer and λ is the wavelength of light)
To a constant thickness d _B that satisfies the above condition. Alternatively, this polishing step may be performed in the next step 2.

Step 2 Next, as shown in FIG. 2, the birefringent material 1 is bonded to the surface of the optical element 3 having a refractive index n _E1 by an adhesive 2 having a refractive index n _A1 . As described above, the polishing of the birefringent material 1 to a predetermined thickness may be performed in the step 1, or may be performed after the bonding.

Step 3 Next, as shown in FIG. 3, a large number of grooves 4 having a constant groove width w ₁ and a constant width w ₂ are formed in the birefringent material 1 by a cutting tool.
Preferably w ₁ = w ₂ . When the depth of the groove 4 is determined so as to penetrate the birefringent material 1 and reach the optical element 3, the thickness of the material removed from the birefringent material 1 is always constant.
On the other hand, the groove depth in the portion of the optical element 3 may be arbitrary as will be described later, and therefore the processing accuracy of the groove depth may be low.

Step 4 Finally, as shown in FIG. 4, the groove 5 is filled with a filler 5 having a refractive index n _E2.
To complete the polarizer 6. The filling may be performed only in the groove 4 or may cover the entire surface of the birefringent material 1 as shown in the drawing. When the second optical element 7 is further joined to form an integrated optical device, the filler 5 may be the same adhesive as the adhesive 2, for example. The second optical element 7 depends on the type of the optical device. For example, in the case of an optical isolator, the second optical element 7 is a Faraday rotator. In the case of the optical isolator having no polarization dependence described in Japanese Patent Application No. 3-358107,
The second optical element is a Faraday rotator, and the polarizer of the present invention is attached to both surfaces of the Faraday rotator. in this case,
It is necessary to adjust the positions so that the grooves of the polarizers on both sides are parallel to each other and the polarization dependence is eliminated.

In order for the polarizer of FIG. 4 to have a predetermined polarization effect, n _A1 = n _B1 = n _E1 = n _E2 ≠
The material of each part is selected so that the relationship of n _B2 is established.
By doing so, it is clear that the following relationship holds. (1) Linearly polarized light for n _{B1 The} birefringent material 1, the adhesives 1 and 5, and the optical element 3 all have the same refractive index, and light does not diffract and goes straight without loss. (2) Since linearly polarized light for n _{B2 is} (n _A2 −n _B2 ) d _B = (M + ½) λ (where M is an arbitrary integer and λ is the wavelength of light), all the light is diffracted.

Here, as the birefringent material, any transparent birefringent material can be used. Typical materials include quartz, calcite, sapphire, ADP, KDP, rutile and the like. For example, if an x-cut crystal plate is used, a half-length plate with a thickness of 76 μm and a wavelength of 1.31 μm is obtained.
As the optical element, any transparent isotropic material can be used, but glass that can control the refractive index with high precision is particularly suitable.

[0015]

According to the present invention, only the entire thickness of the birefringent material needs to be manufactured with high accuracy, and the groove processing of the birefringent material is sufficient if the through groove can be formed. Therefore, it is necessary to precisely control the groove depth. Absent. Further, since it is sufficient to set the refractive index to be the same for straight light, straight light does not scatter even if the surface is roughened during groove processing.

[Brief description of drawings]

FIG. 1 is a front view showing step 1 of a production example of a polarizer of the present invention.

FIG. 2 is a front view showing step 2 of the production example of the polarizer of the present invention.

FIG. 3 is a front view showing step 3 of the production example of the polarizer of the present invention.

FIG. 4 is a front view showing step 4 of the production example of the polarizer of the present invention.

[Explanation of symbols]

 1 Birefringent Material 2 Adhesive 3 Optical Element 4 Groove 5 Filler 6 Polarizer 7 Second Optical Element

Claims (5)

[Claims] 1. An optical element and a refractive index n _B1 for two unique linearly polarized lights which are bonded to the surface of the optical element with an adhesive interposed therebetween,
n _B2 and and has a thickness _{d B (n B1 -n B2)} d B = (M
+1/2) λ (where M is an arbitrary integer and λ is the wavelength of light)
A birefringent material satisfying the above, a groove at a constant interval provided in the birefringent material at a depth reaching the optical element, and a filler filled in the groove, further the optical element, an adhesive, A polarizer in which one refractive index of the birefringent material and the refractive index of the filler are set to be substantially the same. 2. A surface of an optical element with an adhesive interposed between the optical element and the optical element.
One unique and has a refractive index n _B1, n _B2, and the thickness d _B against linearly polarized light _{(n B1 -n B2) d B} = (M + 1/2) λ
(Where M is an arbitrary integer, λ is the wavelength of light), a birefringent material is joined, grooves are formed in the birefringent material at regular intervals at a depth reaching the optical element, and the grooves are filled. A method for manufacturing a polarizer, which comprises filling an agent, wherein the optical element, the adhesive and the filler have a refractive index substantially the same as that of one of the birefringent materials. 3. The first optical element, which has refractive indices n _B1 , n _B2 and a thickness d _B for two unique linearly polarized lights bonded to the surface of the first optical element with an adhesive interposed therebetween, and has (n _B1 − n _B2 ) d _B
= (M + 1/2) λ (where M is an arbitrary integer, λ is the wavelength of light), and a constant interval provided in the birefringent material at a depth reaching the first optical element. Groove of
The groove is filled with an adhesive filler and a second optical element bonded on the groove, and the refractive index of the first optical element, the adhesive and the adhesive filler is An optical device including an optical element with a polarizer, which has substantially the same refractive index as that of one of the birefringent materials. 4. The optical device is an optical isolator, the optical device comprising:
The optical device according to claim 3, wherein the optical element is a Faraday rotator. 5. The optical device according to claim 3, wherein the optical device is an optical isolator having no polarization dependence.