JPS63115113A - Connection structure between light guide and optical fiber - Google Patents

Abstract

PURPOSE:To connect a light guide and an optical fiber to each other efficiently by installing an end surface of the optical fiber in a guide groove so that the end surface abuts on an end surface of the light guide. CONSTITUTION:The guide groove where the end part of the optical fiber F to be connected to the light guide L formed on a substrate 1 is formed opposite the light guide L on the substrate 1. Then, a groove 3 which is deeper than the groove 2 is formed at the joint part between the optical fiber 1 in the bottom surface part of the groove 2 and the end part of the fiber 1 so as to cross the groove 2. Then, the end part of the fiber F is arranged in the groove 2 so that the end surface abuts on the end surface of the light guide L. Consequently, the end surface of the light guide L and the end surface of the core C of the fiber come into contact and the light guide L and fiber F are connected to each other efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a connection structure between an optical waveguide formed on a substrate and an optical fiber.

(Prior Art) In recent years, optoelectronics has advanced and various devices using optical fibers have been put into practical use. In this type of equipment, the devices constituting the optical circuit are individual components, so as the number of devices incorporated into the optical circuit increases, optical axis adjustment and its stability always become a problem. As a solution to these problems, an optical integrated circuit in which a plurality of devices are integrated on one substrate is being considered. In order to put optical integrated circuits into practical use, it is necessary to efficiently connect optical fibers and optical waveguides formed on optical material substrates such as lithium diobate L i N b 07, that is, to connect optical fiber cores. It is important to closely contact the end face of the leading waveguide with good precision.

Optical waveguides include two-dimensional optical waveguides (slab waveguides) and three-dimensional optical waveguides (channel waveguides). Normally, in the case of single mode propagation, the thickness of a three-dimensional optical waveguide is about 1 μm and the width is about 4 μm. It is. -1 Optical fiber has a diameter of approximately 120 μm
Since the core diameter is 5 to 10 μm, in order to connect the optical fiber so that the core is in close contact with the end face of the optical waveguide, a guide is required to place the end of the optical fiber at a position facing the optical waveguide on the substrate. It is necessary to form a groove.

Examples of methods for forming the guide groove include a photolithography method and a method of directly forming the groove on the substrate using a dicer.

(Problems to be Solved by the Invention) However, when using a photolithographic method, that is, forming a resist film on a substrate and forming guide grooves by chemical etching, the depth of the guide grooves is 60 μm.
Due to the extent and depth of the undercut U as shown in Figure 3.
progresses. And 1 resist! The groove width may be wider than the width of the window W formed in IIH, or the corner portions of the groove may be curved. Therefore, it becomes difficult to align the core C of the optical fiber F and the optical waveguide, and it also becomes difficult to bring the end face of the optical fiber F into close contact with the optical waveguide as shown in FIG. Furthermore, if dry etching such as ion milling is used instead of chemical etching, undercutting will not occur and the processing accuracy will be improved, but there is the disadvantage that the processing time will be extended to several hours.

On the other hand, when the guide groove is directly made with a dicer,
As shown in FIG. 5, the optical waveguide side end of the bottom surface of the guide groove 2 formed on the substrate 1 has a curved surface with a large radius of curvature corresponding to the radius of the rotary tool T of the dicer. Therefore, in order to efficiently connect the core C of the optical fiber F and the optical waveguide, the end of the optical fiber F must also be processed to match the curvature of the bottom surface. . Moreover, substrate materials such as L i N b 03 are brittle and easily chipped, so if the guide grooves 2 are directly formed with a dicer, chipping will occur at the edges of the guide grooves 2, making it difficult to connect efficiently. There is also the problem of not having one.

Structure of the Invention (Means for Solving the Problems) In order to solve the above-mentioned problems, in the present invention, a guide groove for installing an end of an optical fiber to be connected to an optical waveguide formed on a substrate is formed on the substrate. A groove is formed at a position facing the upper optical waveguide, and further has a groove having a depth equal to or greater than the depth of the guide groove at a joint portion between the optical fiber end and the optical waveguide in the bottom portion of the guide groove. The optical fiber was formed to intersect with the guide groove, and the end of the optical fiber was placed in the guide groove so that the end surface of the optical fiber came into contact with the end surface of the guide waveguide.

(Function) In this invention, when the guide groove is formed by a groove that intersects with the guide groove formed at the joint portion of the leading waveguide and the guide groove and has a depth greater than the depth of the guide groove, Since the curved surface portion formed at the joint portion is removed, the core of the optical fiber is tightly connected to the end face of the guiding waveguide when the end portion of the optical fiber is installed in the guide groove.

(Example) An example embodying the present invention will be described below with reference to the drawings. In FIG. 1, L i where an optical waveguide is formed
At a position facing the optical waveguide on the N b Os substrate 1, a guide groove 2 for installing the end of the optical fiber to be connected to the optical waveguide is cut into a width of 1 using a dicer as in the conventional method.
After forming the guide groove 2 to have a diameter of 20 μm and a depth of 60 μm, the curved surface portion 2a of the guide groove 2 is removed by laser processing. Groove 3 with a depth of
(EMM)
It was formed by micro-wrapping using the fishing method.

A low-vibration spindle equipped with a silicon carbide (SiC) tool was used for the micro-lapping process, and the surface roughness of the 0-rotation tool was Rmax x 1 μm, which was performed at a tool circumferential speed of 1300 m/win. The processing liquid used was one in which S i 02 with a particle size of 0.24 μm was dispersed in water. As a result, the side surface of the groove 3, that is, the joint surface S between the optical waveguide and the optical fiber F, has a surface roughness R.
A mirror surface with a max of 39 Å or less was formed, and there was no chipping at the edges.

If the end of the optical fiber F is placed in the guide groove 2 formed as described above so that its end surface is in contact with the side surface of the groove 3, the end surface of the optical waveguide and the light will be connected to each other as shown in FIG. The end face of the core C of the fiber F is brought into close contact with the end face of the core C, and the optical waveguide and the optical fiber F are efficiently connected.

Note that the present invention is not limited to the above-mentioned embodiments; for example, the guide groove 2 may be formed only by laser processing,
The groove 3 may not be formed over the entire width of the substrate 1, but may be formed to have the same length as the width of the guide groove 2, and Si3 may be used instead of SIC as the material of the rotating tool for micro-lapping processing.
When using N+ or as abrasive grains used in machining fluid, particle size 0
．． AI20s particles etc. of about 3 μm may be used.
Furthermore, m3 may be formed not to be orthogonal to the guide groove 2. In this case, the optical fiber F is processed so that the angle between its end face and the axis line is the same as the angle between the guide groove 2 and the groove 3. However, since it is not a curved surface processing, processing is easy.

Effects of the Invention As detailed above, according to the present invention, it is possible to efficiently connect an optical waveguide formed on an optical material substrate and an optical fiber, although the processing time is short. It has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment embodying this invention;
FIG. 2 is a cross-sectional view of a cut plane passing through the guide groove and the optical waveguide and perpendicular to the substrate, and FIG. 3 is a cross-sectional view showing the progress of undercut in conventional chemical etching.
FIG. 4 is a cross-sectional view showing the state of connection between the optical waveguide and the optical fiber when the guide grooves are formed by conventional chemical etching, and FIG. 5 is a perspective view showing the process of forming the guide grooves using a dicer. In the figure, 1 is a substrate, 2 is a guide groove, 3 is a groove, F is an optical fiber, C is a core, and L is a leading waveguide.

Claims (1)

[Claims] 1. A guide groove (2) for installing an end of an optical fiber (F) to be connected to an optical waveguide (L) formed on the substrate (1) is formed on the optical waveguide (L) formed on the substrate (1). The guide groove (2) is formed at a position facing the waveguide (L), and furthermore, the guide groove (2) is formed at a joint between the optical fiber end and the optical waveguide (L) in the bottom of the guide groove (2).
) with a groove (3) having a depth greater than or equal to the depth of the guide groove (
2) Formed to cross the optical fiber (F)
A connection structure between an optical waveguide and an optical fiber, characterized in that an end portion of the optical waveguide (L) is installed in the guide groove (2) so that its end surface abuts the end surface of the optical waveguide (L). 2. The connection structure between an optical waveguide and an optical fiber according to claim 1, wherein the groove (3) is formed to be perpendicular to the guide groove (2). 3. The groove (3) is made by elastic emission machining (Elastic Emission Machining).
A connection structure between an optical waveguide and an optical fiber according to claim 1 or 2, which is formed by micro-wrapping using a hin-ing (EEM) method.