JPS6287905A - Production of waveguide lens - Google Patents

Abstract

PURPOSE:To permit working with good accuracy by providing a stage for forming a concave curved face part having a geodesic lens shape by machining to a substrate consisting of crystallized glass and stage for forming an optical waveguide to the substrate surface. CONSTITUTION:The concave curved face 3 constituting the geodesic lens is worked by using a grinding tool 2 consisting of a high speed steel, etc., on the surface of the free-cutting crystallized glass substrate 1 consisting of the crystallized glass internally contg. the fine-grain crystal of mica. The top end face 2A of the grinding tool 2 is preliminarily formed to the curved face of the geodesic lens and an aq. soln. of, for example, cerium oxide is coated on the face 2A of the grinding tool 2 and said face is pressed to the surface 1A of the substrate 1 at about 300rpm to machine the surface and to form the geodesically curved face 3. The waveguide layer 4 consisting of three layers formed and laminated with transparent dielectric materials is formed on the substrate surface. The crystallized glass internally contg. the fine-grain crystal of mica has the extremely good machinability. The concave curved face part constituting the geodesic lens is thereby easily machined with the high shape accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a waveguide lens used in an optical waveguide device.

[Description of prior art]

A waveguide lens is incorporated into a waveguide and has the function of converting a diffused light beam propagating within the waveguide into a parallel light beam within a plane parallel to the waveguide, or converging a parallel light beam within the above plane. It is widely used in guided waveguide devices such as integrated spectrum analyzers and optical wavelength fractionating/demultiplexing circuits. This waveguide lens has various configurations, but one that is effective for multimode light is a geodesic lens in which a part of the waveguide layer has a concave curved surface of a specific shape. Known methods for manufacturing geodesic lenses include ultra-precision cutting using a diamond cutting tool for LiNbO3 substrates, and intraocular pressure or pressurization processing for glass substrates under high temperature conditions.

The former is a method of cutting by rotating the LiNbO3 substrate and precisely numerically controlling the position of the diamond bite, while the latter is a method of raising the temperature to near the deformation temperature of glass and pressing it against a mold of graphite or the like with an inert gas or using a vacuum. This is a method of forming a concave curved surface portion of a geodesic lens on a thin glass substrate by applying suction.

When forming an optical waveguide layer on a substrate provided with a concave curved surface as described above, in the case of a LiNbO3 substrate, Ti is diffused, and in the case of a glass substrate, ions that increase the refractive index of the glass are introduced into the glass. An optical waveguide layer with a high refractive index is formed by diffusing the light into a high refractive index.

[Problem that the invention seeks to solve]

Among the conventional manufacturing methods, those using LiNbO3 substrates have the disadvantage that cutting takes time and costs are high due to the high hardness of the substrate.
It is not practical unless the unique piezoelectric effect or acousto-optic effect is specifically used.

Furthermore, although the method using thermal deformation of a glass substrate is simple, it has the disadvantage that it is difficult to accurately process the shape of the desired geodesic lens curved surface.

[Means to solve problems]

The present invention, which solves the above problems, uses crystallized glass containing microcrystals of mica inside as a substrate, forms four parts of a predetermined shape on a part of the substrate surface of this crystallized glass by machining, After that, a high refractive index waveguide layer is laminated on the substrate surface including these four parts by plasma chemical vapor deposition (plasma CVD) or the like.

[Operation and Effect] Crystallized glass containing microcrystals of mica inside has extremely good machinability, and the concave curved portion constituting the geodesic lens can be easily machined onto the substrate surface with high shape accuracy.

Furthermore, the above-mentioned crystallized glass has better machinability than brass or aluminum, and therefore, ultra-precision cutting using a diamond cutting tool, which is difficult to apply to ordinary glass, can be applied.

Further, the above-mentioned crystallized glass can sufficiently withstand the rise in substrate temperature (approximately 300''C) when the waveguide layer is formed by plasma CVD.

As described above, according to the method of the present invention, a guiding waveguide including a geodesic lens with good shape accuracy can be manufactured at low cost and through a simple process, and is highly practical.

〔Example〕

EMBODIMENT OF THE INVENTION Below, one embodiment of the present invention shown in the drawings will be described in detail. In FIG. 1, 1 is a free-cutting crystallized glass substrate made of crystallized glass containing mica microcrystals therein.

An example is L, T 5i02. Al2O3, MgO, Ni2
0. A crystallized glass containing F and B2O3 in which synthetic mica microcrystals are randomly grown by heat treatment (commercially available product, trade name "Macol", manufactured by Corning Glass Works, USA) is used.

A concave curved surface 3 constituting a geodesic lens is formed on the surface of the above-mentioned free-cutting crystallized glass substrate 1 using a grinding tool 2 made of high-speed steel or the like.

The tip surface uA of the grinding tool is formed in advance into the curved surface of the geodesic lens, and the tip surface 2A of the grinding tool is coated with, for example, an aqueous solution of cerium oxide, and is heated to approximately JOOrpm.
A geodesic curved surface 3 is created by pressing the surface /A of the substrate 1 at a rotational speed of .

Free-cutting crystallized glass is a milky white opaque material, and since this glass alone cannot constitute a waveguide layer, the next step is to create a transparent dielectric material on the substrate surface including the geodesic curved surface 3 region by plasma CVD method. A waveguide layer l consisting of three layers is formed by laminating them.

The first waveguide layer II/ is, for example, 8102 with a thickness of 10 μm.
It is made of a thin film and is formed by placing a substrate in a plasma generation region and reacting 5iC14 introduced by carrier O2 gas.

The second waveguide layer 12 is, for example, a 5i0 layer with a thickness of 30 μm.
2 + Si3N4 thin film, which reacts with 5iCJ4 and NH3 introduced by the carrier 02 gas with the crystallized glass substrate/ placed in the plasma generation region following the fabrication of the first waveguide layer 4Z/. Then, a generated layer is formed on the first waveguide layer IIl.

As an example, the third waveguide layer 13 has a thickness of 81 μm.
02 film, and following the fabrication of the second waveguide layer II2,
With the substrate / placed in the plasma generation area, 5i (J4) introduced by the carrier 02 gas is reacted, and the second
The waveguide layer 2 is produced and laminated on top of the waveguide layer 2. The refractive index of the intermediate first waveguide layer 12 is the highest, for example, 85-, and the upper and lower first and second waveguide layers 111.1
1.3 is lower than this, for example, 8IIr, and the second waveguide layer II2 functions as a multimode optical waveguide having cladding layers on both sides.

In the waveguide lens having the above configuration, the second waveguide layer/I2
The light coupled to the ends of the
Third waveguide layer 111. 'lj and propagates in the direction of the surface of the substrate. The second waveguide layer II2 along the four geodesic curved surfaces 3 of the substrate acts as a geodesic lens, and the light passing through this region is subjected to a lens action within the plane, for example, diffused light is converted into parallel light within the plane. After that, the waveguide layer propagates as it is through the planar waveguide section following the lens j.
Although Si and 5i02+Si3N4 were used as the material of the film, there is no particular restriction on the material as long as it is transparent to light of the used wavelength and can provide a predetermined difference in refractive index.

In addition to stacking multiple layers with different refractive indexes to give a step-like refractive index distribution in the depth direction within the cross section, the waveguide layer can be constructed by continuously changing the composition of the layered film. , it is also possible to construct a substantially single-layer waveguide having a refractive index distribution that is paraporic in the depth direction.

However, since the substrate I is opaque, the first waveguide layer I
It is necessary to determine the thickness of l/.

In addition, in order to efficiently couple light from optical fibers, etc., each waveguide layer 'l/, l12. It is desirable to optimize each of the '13 parameters. In addition, as a processing method for the substrate, various machining methods such as an ultra-precision cutting method using a diamond cutting tool can be used instead of grinding using an ultra-high speed scraping tool.

Furthermore, the waveguide layer can be formed using various well-known film forming methods other than the plasma CVD method, but the plasma CVD method is suitable for forming a thick transparent dielectric film and is less likely to cause cracks. In the method of the present invention, it is preferable to form the waveguide layer by the plasma CVD method because quality deterioration such as the above can be easily prevented.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, FIG. 7 is a sectional view showing the process of forming a geodesic concave curved surface part by machining on a crystallized glass substrate, and FIG. 1 is a diagram showing a waveguide lens obtained by the method of the present invention. FIG. /... Crystallized glass substrate 2... Grinding tool 3... Geodesic curved surface Gu... Waveguide layer! ...Geodesic lens Figure 1 Figure 2

Claims (1)

[Claims] The method comprises the steps of: forming a concave curved surface portion in the shape of a geodesic lens by machining on a substrate of crystallized glass containing mica microcrystals therein; and forming an optical waveguide layer on the substrate surface including the concave curved surface section. A method of manufacturing a waveguide lens.