JPS6057561B2 - Manufacturing method of dielectric diffraction grating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a dielectric diffraction grating, which allows dielectric diffraction gratings to be manufactured in large quantities at low cost.

Volume-shaped dielectric diffraction gratings with wavelength selectivity are promising optical circuit elements as wavelength demultiplexing elements for wavelength multiplexed optical communications.

Conventionally, such volume dielectric diffraction gratings have been used in holographic applications by recording three-dimensional interference fringes created by two beams of light onto photographic plates, dichromate gelatin films, photosensitive crystals, etc. has been created. However, the conventional method described above requires a losser light source with good coherence and a highly accurate and stable optical exposure device.
It has been difficult to mass-produce homogeneous diffraction gratings.
Furthermore, since a photosensitive substance is used as the material, there is a drawback that the characteristics tend to change over time when used under light irradiation. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a dielectric diffraction grating that can eliminate the above-mentioned drawbacks.

According to the present invention, at least two types of glass plates having different refractive indexes are alternately laminated and fused, then heated and stretched to reduce the cross section, and then cut in the longitudinal direction to form a thin plate-like dielectric diffraction grating. A method for manufacturing a dielectric diffraction grating is obtained.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a dielectric diffraction grating obtained by the present invention. It is a figure showing the cross section of the thickness direction regarding an example. In the figure, 11 represents a high refractive index glass, and 12 represents a low refractive index glass. The dielectric diffraction grating 1 has a laminated structure in which high refractive index glass 11 and low refractive index glass 12 are alternately repeated. Normally, as is well known, for light incident at an incident angle θ to a normal crystal parallel to the lattice plane, its wavelength λ and lattice spacing d
Regarding λ■2mdsin0 (however, m=1, 2, 3, .
Only the light that substantially satisfies the integer of . As is well known, the extent to which the above conditions must be satisfied is determined by the amount proportional to the thickness of the dielectric diffraction grating 1 (for example, 0 300, λ = j 900 nm).
d: 900nm, designed under the usage conditions of ■0.5
The dielectric diffraction grating exhibits almost no diffraction effect except for light in the range of 897 to 903n7n. Second
3 and 3 are diagrams illustrating an embodiment of the present invention.

In the figure, 21 is a glass plate with a high refractive index, and 22 is a glass plate with a low refractive index. 2 represents a dielectric diffraction grating base material obtained by laminating and fusing the high refractive index glass plates 21 and low refractive index glass plates 22 alternately.

3 is a heating furnace for heating the dielectric grating base material 2 to a hardened state; 4 is a stretching roller for stretching the dielectric grating base material 2; and 5 is a stretching roller for stretching the dielectric grating base material 2. This is a feeding device for feeding to the heating furnace 3 according to the speed.

In this embodiment, first, two types of glass thin plates 21 having different refractive indexes are used.
, 22 are alternately stacked, and then heated to around the softening temperature of the glass while applying pressure in the stacking direction. Through this step, the dielectric grating base material 2 shown in FIG. 2 is obtained. Thickness 0
．． 1? , 50 each of 2 types of thin glass plates with a width of 10d and a length of 2cm.
By alternately laminating and fusing the copies, a dielectric diffraction grating base material having a cross section of about 1 cm x 10 d and a length of about d can be obtained. If external precision is required, subsequent to this step, the external shape of the dielectric grating base material may be modified and polished. Next, this dielectric diffraction grating base material 2 is heated and stretched using a heating and stretching apparatus shown in FIG. For example, the dielectric grating base material is fed at a speed of 51
If the dielectric grating base material 2 is stretched at a stretching speed of m1min1 of 607rL1min, the cross-sectional structure of the dielectric grating base material 2 will be stretched and reduced to a similar shape in the softened part in the heating furnace 3, and the cross-sectional size will be about 0.9? ×
0.9WI. , grid spacing 900r17n1 length approximately 2ゐ-
An elongated dielectric grating matrix is obtained. If this dielectric diffraction grating base material is cut out to a thickness of 0.5]11 in the length direction, the aforementioned dielectric diffraction grating (1) with a thickness of 0.5 m, a designated wavelength of 900 nW, and a designated incident angle of 30 can be obtained. In this example, the distraction/reduction ratio of the dielectric grating base material can be set extremely accurately by controlling the distraction speed and feed rate, and if a large amount of distraction means is provided, a large distraction/reduction ratio can be easily achieved. Something to do. Therefore, it is possible to create with high precision a short grating interval, which is difficult to achieve using the conventional two-beam interference exposure method. Furthermore, as is clear from the above description, the dielectric diffraction grating with a minute aperture, which is normally required for optical fiber communication, is one of the examples of this embodiment! It can be obtained in extremely large amounts from the working process. In addition, in the above-mentioned example, an example was shown in which the dielectric diffraction grating surface and the grating plane are perpendicular to each other, but of course the present invention is not limited to this.
A dielectric grating having an inclined grating plane can also be manufactured by cutting out the elongated dielectric grating base material obliquely to the longitudinal axis. In addition, it is not necessary to limit the direction of the cut base material to the thickness direction of the dielectric diffraction grating. It can also be used to manufacture a dielectric diffraction grating that reflects only light of a specific wavelength or a multilayer interference filter. In the above embodiments, the dielectric grating base material has a square cross-sectional shape, but the present invention is not limited to manufacturing such a cross-sectional shape. It will be clear that the present invention can be applied not only to the production of gratings having not only two-step rectangular wave changes but also sinusoidal or triangular wave changes in refractive index using many types of refractive index glasses. Finally, to enumerate the features of the present invention, dielectric diffraction gratings with accurate grating spacing can be mass-produced at low cost, dielectric gratings with arbitrary refractive index distribution shapes can be obtained, and thick dielectric diffraction gratings can be obtained. can be easily created.

[Brief explanation of the drawing]

FIG. 1 shows a cross section of an example of a dielectric diffraction grating obtained from an embodiment of the present invention, and FIGS. 2 and 3 are diagrams for explaining an embodiment of the present invention.

Claims (1)

[Claims] 1. At least two types of glass plates with different refractive indexes are alternately laminated and fused, then heated and stretched to reduce the cross section, and then cut in the longitudinal direction to form a thin plate-like dielectric diffraction grating. A method for manufacturing a dielectric diffraction grating.