JPS6091302A - Exposure mask and method for producing different-period diffraction grating pattern - Google Patents

Abstract

PURPOSE:To form diffraction grating patterns with different periods on the same substrate in single-time exposure by using a transparent plate having a taper plate variation part at >=1 places as a mask for exposure. CONSTITUTION:The exposure mask 201 has the 1st - the 3rd tapered thickness variation parts 202, 204 and 205 partially. The mask 200 is made of glass by using a ceramic mold having the tapered thickness variation parts. The mask 201 is used to form an interference pattern on an interference-exposed surface 101. The mask 201 and an exposure system are placed in air. Pieces 102 and 102' of luminous flux passes through the mask 201 without changing in traveling direction when passing through the variation parts 202 in a section A-A'.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exposure mask and an exposure method for forming diffraction grating patterns with different periods on one substrate.

In recent years, with improvements in semiconductor laser and optical circuit manufacturing technology, optical integrated circuits that integrate semiconductor lasers with different oscillation wavelengths on a single substrate, or multiplexing and demultiplexing light with different wavelengths have become popular. Multiple demultiplexing circuits on one board
) YZ integrated circuits are attracting attention. 2 In a circuit, for example, when attempting to integrate semiconductor lasers with different oscillation wavelengths on one substrate using a distributed feedback laser, it is necessary to integrate diffraction gratings with different periods corresponding to different oscillation wavelengths on one substrate. It is necessary to form the Conventionally,
In the case of forming a double grating, a three-beam interferometry method as shown in FIG. 1 was used.

Here, 101 is an interference exposed surface, 102 and 102' are light beams forming a diffraction grating pattern on the interference exposed surface 101,
103, 103' are reflecting mirrors, 104 is a half mirror 51
05 is a beam diameter conversion lens, and 106 is a laser light source. However, in this two-beam interference method, the interference exposed surface 10
Since the diffraction grating pattern formed on the same substrate has only one period, there is a drawback that diffraction grating patterns with different periods cannot be formed on the same substrate by one exposure.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure mask and an exposure method for creating diffraction grating patterns with different periods, which can eliminate the above-mentioned drawbacks and form diffraction grating patterns with different periods on the same substrate with one exposure. be.

The h-light mask of the present invention is constituted by a transparent plate (transparent at least to exposure light) having a tapered thickness changing portion of - or more. Further, the non-light method of the present invention is a Z-beam interference exposure system that forms a diffraction grating-like interference pattern by intersecting two mutually coherent light beams on the surface to be exposed. This method involves installing a mask and performing interference exposure.

Hereinafter, the present invention will be described in detail with reference to all the drawings.

FIG. 2 is a perspective view of an embodiment of an exposure mask for creating a different-period diffraction grating pattern according to the present invention, FIG. 3 is a sectional view taken along the breaking line AA' of the perspective view shown in FIG. 2, and FIG. 1 is an interference exposure system showing an embodiment of a method for creating a single grating pattern by rotating at different periods according to the present invention.

In FIG. 2, 201 is an exposure mask, a part of which has a first mask. Second. Third tapered thickness change portion 202.204
．． 205. This exposure mask 201 is made of glass using a ceramic mold in which a tapered thickness change portion is molded. Using this exposure mask 201, an interference pattern is created on the interference exposure direction 101 using an exposure system as shown in FIG. Here, the exposure mask 201 in FIG. 2 is installed so that its cross section AA' falls within the plane of the paper in FIG. 4, and the path light mask 201 and the exposure system are installed in the air. . At this time, the luminous flux 1 in Fig. 4
02, 102' is the cross section A of the exposure mask 201 in FIG.
-A', as shown in FIG. 3, when passing through the tapered thickness changing part 202, its traveling direction is bent, and when passing through the flat part 203, it passes through the exposure mask 201 without being bent. do.

Next, it will be explained that four types of diffraction grating patterns with different periods can be created by one exposure.

First, using the cross section A-A', a relationship generally holds between the incident angle and the outgoing angle with respect to the mask for two light beams incident on the tapered thickness change part having the taper angle δ and the flat part. Explain. Now, the tapered thickness changing portion 202
, the two light beams 102 and 102' are on the flat surface 203
When the incident angles are θ and θ', respectively, with respect to the perpendicular 301 to the plane at stand.

α= 5in-' [n5ln [-δ0gin"(s
in(δ10))]) 11) Furthermore, the above emission angle α,
The light transmitted through the exposure mask 201 at β is the interference exposed surface 10
1, a diffraction grating-like interference pattern with a period A expressed by the following equation is produced. That is to say. Here, λ is the wavelength of the light source. Now, in this embodiment, the incident angles θ and θ of the two light beams 102 and 102' are
' are both 45°, refractive index of glass n = 1.5°, wavelength of light source λ = 325OA, 1st. Second. The third tapered thickness changing portions 202, 204, and 2050 have taper angles δ of 10°, 5°, and 15°, respectively, and the taper angle δ of the flat portion 203 is 0°, so equations (1) to (3) using the first
, 2nd. Third tapered thickness changing portion 202 , 204
.

205 and the two light beams 102°1 that passed through the flat part 203
The grating periods of the interference patterns formed by 02' are 2331A, 2306A, and 2374A, respectively.

It becomes 2298A.

Therefore, if the exposure mask according to this embodiment is used, four types of diffraction grating patterns with different periods can be produced in one exposure.
Can be created.

Note that a non-reflection coating is applied to the surface of the main exposure mask 2010 to prevent unnecessary interference patterns from occurring.

An embodiment of the exposure mask for creating a different periodic diffraction grating pattern and the method for creating a different periodic diffraction grating pattern according to the present invention has been described above. In the embodiment of the exposure mask for creating a different periodic diffraction grating pattern shown in FIG. 2, there are three tapered thickness changing portions, but there may be one or more tapered thickness changing portions. Also, the first, m2. The taper angle δ of the third tapered thickness changing portions 202, 204, and 205 is each 10°.

Although the angles are set to 5° and 15°, it is clear that the angles are not limited to these values. Further, the tapered thickness changing portion may be in the shape of a protrusion or a dip. In addition, although the fog light mask 201 was formed using a ceramic mold in which a tapered thickness change part was modeled, it could also be formed by pasting a tapered glass plate formed by polishing onto a flat glass. good. In addition, although the exposure mask 201 was made of glass, plastic
It may also be made of other transparent materials such as resin, in which case it may be made by injection molding.

In addition, in the embodiment of the different periodic diffraction grating pattern creation method shown in Figure @4, the exposure mask 201 and the interference exposed surface 1
01, but it may be used by filling it with matching oil or by bringing it into close contact. In that case, the refractive index of the matching oil or the interference exposed surface is n. The expression +1) and (21 are α-5in-'C" respectively)
slnllg-δ+S stone-1(sin(δ+U) l
3 J (1)'n.

However, other than this, the interference pattern can be formed in the same way.

Finally, the features of the exposure mask for creating a diffraction grating pattern with different periods and the method of creating a diffraction grating pattern with different periods according to the present invention are as follows: Diffraction grating patterns with different periods can be formed by one non-irradiation process, which is almost the same as the conventional one. It can be applied to interference-based optical fibers.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the entire conventional # half pattern forming method, Fig. 2 is a perspective view of a lightless mask for forming a different periodic diffraction grating pattern according to the present invention, and Fig. 3 is a cutaway view of the perspective view shown in Fig. 2. Line A-
The cross-sectional view at A' in FIG. 4 shows a three-beam interference exposure system using an embodiment of the present invention. In the figure, 101... interference exposed surface, 102, 102'...
Luminous flux, 103.103'...Reflector, 104...
Half mirror 5105...Lens, 106...Laser light source, 201...Exposure mask, 202.204.205.Taber-shaped thickness change part, 203
. . . Plane portion, 301 . . . Perpendicular line. Representative Patent Attorney Uchihara

Claims (2)

[Claims] (1) An exposure mask for creating a different periodic diffraction grating pattern, which is a transparent plate (transparent at least to exposure light) having a tapered thickness change part of -'d or more. (2) Installing a transparent plate (transparent at least to the exposure light) having two beams that generates a diffraction grating interference pattern by intersecting two mutually coherent beams on the exposed surface,
A method for creating a different periodic diffraction grating pattern, which is characterized by generating and eliminating an interference pattern through this transparent plate.