JPS58211114A - Uneven interval plane diffraction grating - Google Patents

Abstract

PURPOSE:To perform diffraction and convergence simultaneously by forming uneven-interval gradings on plural single-crystal flat plates which are different in surface crystal direction, bit by bit, by anisotropic etching and obtaining different-angle reflective diffraction surfaces. CONSTITUTION:Si single-crystal flat plates 3-5 which differ in surface cyrstal direction, bit by bit, are arranged fixedly on an Si substrate 1 with an adhesive 2, and the surfaces are polished. The surfaces are coated with photoresist 6 and the anisotropic etching is carried out after exposure and development; and the remaining photoresist is removed and then a reflective film 7 is formed over the surface to manufacture the uneven-interval plane gratings 10. The size of single crystal plates 3-5 are determined corresponding to a prescribed blaze angle. The diffraction gratings 10, an optical transmission line 9, and input and output optical fibers 11 and 12 are arranged on a substrate 8. Light 13 incident from the input fiber 11 to the diffraction grating 10 is diffracted and the polarized light of every wavelength is converged to the output fiber 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the diffraction efficiency of a planar diffraction grating that has a light focusing function.

Diffraction gratings include concave diffraction gratings and planar diffraction gratings, and the former can perform diffraction and focusing at the same time, while the latter requires a suitable focusing means because it only performs diffraction. Therefore, attempts have been made to use electron beam exposure or laser light interference to form a grating with uneven spacing to collect light, but this method has the drawback of low diffraction efficiency due to the incomplete shape of the reflection. . It is also possible to make uniformly spaced mosaic diffraction gratings with good diffraction efficiency by making full use of anisotropic etching of single crystals to keep the angles of the reflection diffraction surfaces constant. The method is considered to be a method of making a single crystal substrate thinner (III) and bending it into a cylindrical shape to give it a light-concentrating effect. By combining the two and forming a grating with unequal spacing on a single-crystal flat substrate by electron beam exposure or laser light interference, a flat diffraction grating that can perform diffraction and focusing simultaneously can be obtained.
Since the angle of the reflection diffraction surface is constant, there is a problem that the diffraction efficiency decreases at a position away from the center due to deviation from the blaze angle. Therefore, the purpose of this invention is to improve the diffraction efficiency of such a planar diffraction grating that has a light focusing effect, and as a means for that purpose, it uses a plurality of single-crystal planar substrates whose surfaces have slightly different crystal orientation angles. This forms a planar diffraction grating with non-uniform spacing. According to this method, it is possible to substantially match the blaze angle with respect to the center wavelength at each position and the reflection diffraction surface, and by increasing the number of single crystal substrates, a diffraction grating of any size can be manufactured.

The present invention will be explained below with reference to the drawings.

Figures 1, 2, and 3 show the manufacturing process of one embodiment of this invention. , single crystallites with slightly different angles on the surface of the crystal &3. Next, the surface is polished so that it is uniform, thoroughly cleaned, and photoresist 6 is applied, and then exposed and developed using electric beam exposure or laser beam interference, as shown in Figure 2. Then, a grid of equal intervals is formed using the photoresist 6. When this is etched, the parts of the surfaces of the single-crystal plates 4 and 5 where there is no photoresist 6 are anisotropically etched, so the remaining photoresist 6 is removed and washed, and a reflective film is coated on the entire surface. 7, the unevenly spaced plane diffraction grating is completed as shown in FIG. In this embodiment, a case of three divisions is shown, but the number of divisions C1 is arbitrary, and the fine culm diffraction efficiency increases, but manufacturing becomes complicated. Also, considering the problem of expansion due to temperature, the single crystal flat plate 3
・It is better to use the same quality as 4.b. Single crystal flat plate 3
・7 recon wafer is suitable as the material for 4 and 5 from the point of view of price and processability. In Fig. 3, a single crystal plate',
The reflection diffraction surface of S is the largest, the single crystal flat plate 4 is the next largest, and the single crystal flat plate 5 is the smallest, each matching the blaze angle at the center. These angles are determined in advance by taking into account the entire spread of the incident light and calculating from the wavelength dispersion and focal length. With such a structure, the diffraction direction of the incident light and the reflection direction almost match, which improves the diffraction efficiency. After manufacturing, accurately position and assemble.

FIG. 4 shows an application example of the optical element of the present invention, and shows the optical element installed in an integrated optical demultiplexer for optical communication. In this system, an optical transmission line 9 is placed on a substrate 8, and an unevenly spaced plane diffraction grating 10, an input optical fiber J1, and an output optical fiber 12 are all attached and fixed to the surrounding wall. [Light from] 3 is folded into the non-uniformly spaced plane diffraction grating J, OT 1, and separated into wavelengths by 7,000 yen to the output optical eye T2. The non-uniformly spaced flat diffraction grating 10 can perform a light condensing action while remaining flat, and therefore has the advantage of being easy to manufacture because the area around the optical transmission path 9 only needs to be processed into a flat surface. Since the position of each element must be set accurately, it is easier to form the entire groove in the substrate in advance and bury it. In such an integrated optical demultiplexer, since the center wavelength is determined, it is easy to set the blaze angle, and the combination of angles that provides the best diffraction efficiency can be made. , FIG. 5 shows another embodiment "'C," and FIG.
"Unequally spaced flat circuit made using the process steps shown in Figures 2 and 3"
This is made by pasting Jr. flo onto a cylindrical substrate J4 in a lattice direction. The non-uniformly spaced planar diffraction grating 10 has a full-angle condensing effect in the direction perpendicular to the depression E, but is powerless in the grating direction.
The light is focused by 4 and is a spear.

Therefore, it has a function of 17[deg.] which is completely equivalent to that of a conventional concave diffraction grating. The size of the concave diffraction grating was limited by the manufacturing equipment 1, but this invention is better. 1ri (Koyorare,
For example, a 1m square object is useful for spectroscopic astronomy because it has IIJ capability.

As described above, according to the present invention, an F-plane diffraction grating of any size can be manufactured, and furthermore, since diffraction and focusing can be performed at the same time, there is no need for a separate focusing system. The materials and manufacturing method are similar to LSI, and the equipment can be reused, so special equipment such as a ruling engine is not required.

In terms of production time, it takes much less time than the conventional marking method, making it suitable for mass production and eliminating the need for replicas. The unevenly spaced plane diffraction grating thus obtained can be applied to optical demultiplexers for optical communication, optical wavelength meters, various spectroscopic analysis devices, colorimeters, and the like.

[Brief explanation of the drawing]

1, 2, and 3 are side sectional views of each step of an embodiment of the present invention, FIG. 4 is a plan view of one application, and FIG. 5 is a perspective view of another application. 7, 1--substrate, 2--adhesive, 3, 4, 5- single crystal/top plate, 6--first resist, 7- reflective film, 8- base handling, 9 -IY: Transmission i1.1o---Unequally spaced "F-plane diffraction I8f. ]] - Optical fiber for single force, 12 - For output"
Noiba, ] ] 3 --- Light 14 -- Cylindrical surface substrate Patent applicant Ren Mi Ritsu Male prisoner surface 45 // Fig. 2/7 Fig. 3 Fig. 4 1 o No. 5 WJ

Claims (1)

[Claims] A lattice with uneven spacing is formed by anisotropic -1-notching on a flat substrate of a single crystal of multiple H's with slightly different crystal orientation angles on the surface to form reflective diffraction surfaces with different angles, and diffraction and focusing are achieved. An optical element characterized by simultaneous diffraction and improved diffraction efficiency.