JPS6172202A - Production of curved surface diffraction grating - Google Patents

Abstract

PURPOSE:To obtain a curved surface diffraction grating having the specified blaze angle within the curved surface and high diffraction efficiency by deforming a resilient material formed with a plane diffraction grating to the prescribed curved surface and bringing the curved resilient material into contact with a curved surface diffraction grating material and curing the same. CONSTITUTION:A resilient material 1 is adhered to the curved surface of a base part 2 curved to a prescribed radius of curvature and is deformed. The deformed diffraction grating surface of the material 1 is brought into contact with the curved diffraction grating material 3 in a liquid state and is cured, by which the curved diffraction grating 4 is produced. A metallic alcoholate soln. or plastic such as epoxy resin and ceramics, etc. are usable for such material 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a curved diffraction grating, and more particularly to a method for easily manufacturing a curved grating for an optical component having good performance.

[Background of the invention]

Conventionally, concave diffraction gratings have been mainly used in ultraviolet light spectrometers, etc., but in recent years, with the development of optical multiplex transmission systems in optical communications, the need for optical demultiplexers and multiplexers has increased. Increasing ELECTRONIC5 LETTER
S 17 (1981) 934. Applied 0
ptics 19 (1980) 3588), an economical method of manufacturing diffraction gratings, particularly high performance concave diffraction gratings, is desired.

Conventionally, the method used was to mechanically cut grooves on a precision-machined concave surface using a high-precision ruling machine, and then use this as a mold to create a replica.

This method not only requires expensive equipment to mechanically create grooves with high density, but also requires an expensive device (see Fig. 1).
As shown in al, the angle formed by the main diffraction surface of the diffraction grating with respect to the concave surface (hereinafter abbreviated as blaze angle) differs depending on the position within the concave surface, so it was not possible to increase the diffraction efficiency. Diffraction grating (750 l ine/
m1), radius of curvature 3.8 cm, blaze angle at center 1
Table 1 below shows changes in the blaze angle depending on the position of the curved surface (8.6°).

On the other hand, if the blaze angle can be made constant within the plane as shown in FIG. 1, the blaze condition can be satisfied over the entire curved surface, and the diffraction efficiency can be improved.

Ion beam etching is considered as a method to make the blaze angle constant within the concave surface (Koshiki et al., IEICE theory (C1,
J 64-C, 10, PP652 (Sho 56-6)”
).

However, it has the drawback of requiring expensive equipment and being inferior in economy and productivity.

A method has also been reported in which a diffraction grating is fabricated on a silicon wafer with a thickness of several tens of micrometers, and a concave diffraction grating with a constant blaze angle within the concave surface is fabricated by bending the wafer along a curved surface (Fujii, Electr. .

n1cs 1etters 17 (1981) 9
34). However, this method also has the disadvantage of poor mass productivity.

[Summary of the invention]

The present invention has been made in view of the above points, and it is an object of the present invention to provide a method for manufacturing a concave diffraction grating having a constant blaze angle within the concave surface with good mass productivity and economically.

Therefore, the method for manufacturing a curved diffraction grating according to the present invention is as follows:
The method is characterized in that a flexible material on which a planar diffraction grating of a predetermined shape is formed is deformed into a predetermined curved surface, and the curved flexible material is brought into contact with the curved diffraction grating material and hardened.

According to the method for manufacturing a curved diffraction grating according to the present invention, a curved diffraction grating with high diffraction efficiency and a constant blaze angle within the curved surface can be economically manufactured using a flat diffraction grating that can be easily manufactured using conventional techniques. There is.

[Detailed description of the invention]

FIG. 2 is a diagram schematically showing the method for manufacturing a curved diffraction grating according to the present invention, in which 1 is a flexible material forming a plane diffraction grating, 2 is a base, 3 is a curved diffraction grating material, and 4 is a curved diffraction grating material. A curved diffraction grating is shown.

According to the method for manufacturing a curved diffraction grating according to the present invention, first,
Forming a planar diffraction grating in a flexible material (Fig. 1(a)
)). The method of forming this diffraction grating is not limited in the present invention, and can be produced by a conventional method.

The flexible material 1 forming such a plane diffraction grating is not fundamentally limited in the present invention as long as it has flexibility to be curved into a curved shape.

For example, a plastic or metal film can be used. In particular, it is preferable to use a material that is elastic and resistant to the curved diffraction grating material 3. Silicone resin is particularly excellent as such a flexible material.

Next, the material 1 on which such a plane diffraction grating is formed is deformed into a curved shape, but the method of deformation is not fundamentally limited. For example, as shown in FIG. 2, the curved surface of the base 2 curved to a predetermined radius of curvature can be deformed by attaching a flexible material 1 to the curved surface. In this case, it is pasted so that the surface on which the diffraction grating is formed is on the outside (FIG. 2(b)).

Next, the diffraction grating surface of the flexible material 1 thus deformed is brought into contact with the liquid curved diffraction grating material 3 (Fig. 1(C)).
, and harden (FIG. 1(d)). By taking this out of the container, a curved diffraction grating 4 can be manufactured (see Fig. 1 (
e)).

Such curved grating material 3 may be any material as long as it can be formed by a diffraction grating of flexible material 1 deformed into a curved surface. For example, plastics such as metal alcoholate solutions or epoxy resins described in the method for producing fine patterns using the sol-gel method (Japanese Patent Application No. 129523/1982), which obtains glass molded products from low-viscosity solutions, and Ceramic or the like can be used. That is, as this curved lattice material 3, a normal molding material can be effectively used, and is not fundamentally limited in the present invention.

In particular, the method using the metal alkoxide described above can provide a glass diffraction grating that is highly reliable against changes in temperature and humidity.

When using such a metal alcoholate, a metal alcoholate solution (curved diffraction grating material 3) is prepared, and a flexible material 1 on which a diffraction grating is formed is added to the metal alcoholate solution 3.
and leave it in contact for a certain period of time to gel. After gelling in this way, the flexible material 1 is removed (see Figure 1 (
d)), and then taken out from the container and dried and heated to form a glass diffraction grating 4 (FIG. 1(e)).

The above-mentioned metal alcoholate solution is a solution containing at least one metal alcoholate, water and, if necessary, an alcoholic solvent such as methanol, ethanol, propatool, etc., an acid, a base, and the like.

Examples of such metal alcoholates include tetramethoxysilane and tetraethoxysilane, but the present invention is not limited thereto.

Next, examples of the present invention will be described.

Example 1 A replica diffraction grating of 3001 in/mm was formed on the surface of a silicone resin having a thickness of 2 mm using a commercially available flat diffraction grating as a mask. This was attached to a convex base with a radius of curvature of 9.5 cm and brought into contact with a mixed solution of tetramethoxysilane: methyl alcohol: water (molar ratio 1:4:4), so that the metal alcoholate solution gelled. After that, it was released from the mold. After sufficiently drying, it was heated and sintered to 950'C to obtain a quartz concave diffraction grating as shown in FIG.

The obtained diffraction grating was 0.45 times smaller than the silicone resin diffraction grating used as a mold, and the number of grooves was 7.
The radius of curvature was 3.8 cm.

When the change in position of the blaze angle within the concave surface was investigated, the results shown in Table 2 were obtained. It is shown below along with the above-mentioned Table 1.

As shown in Tables 1 and 2, the blaze angle was approximately constant within the concave surface, and was found to be significantly superior to the conventional one.

(Hereinafter, blank space) Table 1 Table 2 Example 2 3001 ine on a silicone resin surface with a thickness of 30 μm
/1) An echelette diffraction grating with a pitch of H1) was formed by ion beam engraving. This has a radius of curvature of 20cm
Tetramethquine silane: ethyl alcohol: water; hydrochloric acid (molar ratio t:to:t).

:0.02), and after the metal alcoholate solution gelled, the mold was released. After thoroughly drying,
Heat and sinter to 50'c, then cut into thin pieces,
The number of grooves on the end face of the glass thin piece is 9681 inches as shown in Figure 4.
A convex diffraction grating surface 5 with a radius of curvature of 6.2 cm and a radius of curvature of 6.2 cm was fabricated.

Example 3 5001ine on a silicone resin surface with a thickness of 2 mm
/ mm was prepared, and it was attached to a convex base with a half-f curvature of 4 cm, and then brought into contact with uncured epoxy resin, and after the resin was cured, the mold was released, and as shown in Figure 3. A plastic concave diffraction grating of 5001 in/mm was fabricated.

This diffraction grating allows the light guided within the Evokin resin layer to be separated into spectra. It becomes possible to easily install a thin film type optical demultiplexer.

〔Effect of the invention〕

As explained above, according to the method for manufacturing a curved diffraction grating according to the present invention, a convex diffraction grating with high diffraction efficiency and a constant blaze angle within the convex surface is manufactured using a flat diffraction grating that can be easily manufactured using conventional technology. The advantage is that it can be done.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining the state of the blaze angle in a concave diffraction grating, FIG. 2 is an explanatory diagram for explaining the manufacturing method according to the present invention, and FIG. 3 is an explanatory diagram for explaining the manufacturing method according to the present invention.
FIG. 4 is a perspective view of the diffraction grating manufactured in Example 2. ■...Flexible material, 2...Base, 3...Curved diffraction grating material, 4...Concave diffraction grating, 5...Convex diffraction grating.

Claims (2)

[Claims] (1) A curved surface characterized by deforming a flexible material on which a planar diffraction grating of a predetermined shape is formed into a predetermined curved surface, bringing the curved flexible material into contact with the curved grating material, and hardening the curved grating material. A method of manufacturing a diffraction grating. (2) The method for manufacturing a curved diffraction grating according to claim 1, wherein the curved grating material is a metal alcoholate solution.