JPS6330804A - Optical coupler - Google Patents

Abstract

PURPOSE:To obtain an optical coupler which can be easily manufactured and has a high efficiency, by providing a collimating lens on a thin film waveguide, and providing a convex lens on an incident/emitting end face, so that a diffraction grating shape consists of a linear group for easily manufacturing a photomask. CONSTITUTION:A collimating lens 8 and a diffraction grating 3 consisting of a linear group are provided on the surface of an optical waveguide layer, the diffracted light by the diffraction grating 3 is inputted and outputted to and from the surface being different from the surface for contacting a thin film waveguide layer 2 of a substrate 1, and a diffracted light input/output surface is an end face of the substrate 1, and has a convex lens on its surface. The light beams which have been collimated by the lens 8 are diffracted to the substrate side by a diffraction grating 7 consisting of a linear group. The light beams which have been diffracted to the substrate side reach an incident/ emitting end face 11, and form an image in a focus 6 by a lens 9 which has been provided on the incident/emitting end face 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical waveguide type optical coupler having an m-diffraction grating.

[Conventional technology]

2. Description of the Related Art In recent years, information communication and information recording/reproduction using light have been attracting attention, and various optical couplers of thin film optical waveguides having diffraction gratings have been proposed as optical information input/output devices.

The Mononoke illustrated in FIG. 3 shows a schematic configuration of a conventional eIlla optical coupler in which a diffraction grating is provided in a flat plate optical waveguide. That is, this optical coupler has a structure in which a thin film optical waveguide layer 2 is formed on the surface of a substrate 10, and a diffraction grating 3 consisting of a group of unevenly spaced curves is formed at the interface of this optical waveguide layer 2. The guided light 4 propagating through the optical waveguide 2 is diffracted by the diffraction grating 3, and is extracted directly from the surface of the waveguide layer 20 as external light 5 and converged on an extraction focal point 6. However, in an optical coupler having such a structure, when the guided light 4 is diffracted by the diffraction grating and output into the air, it is also diffracted toward the substrate 1 side.

For this reason, the diffraction efficiency and coupling efficiency of light are approximately %. The grating spacing of Mano's diffraction grating is, for example, the wavelength used CL79μ.
If m-effective refractive index is 1.52, it is necessary to vary the minimum grating spacing of the diffraction grating 3 by about 0.5 μm. In order to investigate such a diffraction grating 3, the line @ 0.2μ
m, and it is difficult to form the constant diffraction grating 3 as described above using a manufacturing method using 7 otomasks. If a semiconductor laser is used as the light source of the optical coupler, an ideal diffraction grating cannot be obtained using holographic technology since the wavelengths used are different. In electron beam lithography,
Although it is technically possible, it has the drawbacks of poor mass productivity and expensive equipment. In order to compensate for the above-mentioned drawbacks, an optical coupler ht as shown in FIG. 4 has been proposed (Japanese Patent Laid-Open No. 169107/1983). Diffraction grating 3 of this optical coupler
This is a simple and highly practical optical coupler that allows the minimum grating spacing to be set more closely than the diffraction grating 3 of FIG. However, the grating spacing of the diffraction grating 3 in FIG. 1 is only about twice the radius compared to that in FIG. 5, and the line width is CL
It is 5 μm and 8 degrees.

[Problem that the invention seeks to solve]

When trying to fabricate the diffraction grating 3 consisting of a group of unevenly spaced curves with a line width of about 0.5 μm using optical photolithography technology, it is difficult to pattern the curves on a photomask with an electron beam. In order to ideally approximate a curved shape with a spot, a line of several microns is required, and with a line width of about 0.5 μm, it is difficult to obtain an ideal diffraction grating using optical photoI + lithography technology. Nakomi.

The present invention was developed taking these circumstances into consideration, and its purpose is to provide a collimating lens on a thin inertial waveguide and a convex lens at the input/output end ff1lc, so that the shape of the diffraction grating can be easily fabricated into a photomask. The object is to provide an optical coupler that is easy to manufacture and is highly efficient, with good mass productivity.

[Means for solving problems]

The means to solve the problem will be explained with reference to Figure 1.2. In order to make the diffraction grating 7 into a linear group, the source propagating through the waveguide layer 2 must be parallel light. Therefore, a collimating lens 8 is provided on the waveguide layer 2 to convert the light emitted from the light source 10 into parallel light. The secondary light collimated by the lens 8 is diffracted toward the substrate by the diffraction grating 7 consisting of a group of straight lines. The light diffracted by the substrate reaches the input/output end face 11 and is imaged at a focal point 6 by a lens 9 provided on the input/output side 11. At this time, the focal position fl16 can be arbitrarily changed depending on the shape of the nine lenses 9 provided at the entrance and exit end faces.

〔Example〕

As shown in FIG. 1, a single substrate having an entrance/exit end face in the shape of a convex lens 9 is obtained by press-molding a glass (for example, borosilicate crown glass). A material having a higher refractive index than the substrate (for example, Corning 70
59 glass) is sputtered to form the waveguide layer 2. A collimating lens formed on the waveguide can be used as a grating lens. The grating lens shape and the linear group diffraction grating shape are patterned, a mask is made, a resist is applied on the waveguide layer, and the grating lens shape and the linear group diffraction grating shape are placed on the waveguide layer using optical photolithography. Enjoy the 3D pattern of the resist. Thereafter, Corning 7059 is sputtered again and the resist is removed to obtain an optical coupler having a grating lens and a linear group diffraction grating on the waveguide layer.

The end face of the waveguide layer in contact with the light source section is polished, and the semiconductor laser 10 is bonded to the end face with an optical adhesive.

The next light emitted from the semiconductor laser 10 is collimated by the grating lens 8 and collimated by the linear group diffraction grating 7.
When the light is diffracted toward the substrate 1 side and reaches the input/output end face 11, it is imaged at the focal point 6 by the convex lens 9.

〔Effect of the invention〕

As described above, according to the present invention, in an optical coupler including a thin film optical waveguide layer, by providing an optical coupler configuration in which the diffraction grating is made into a group of straight lines, a five-diffraction grating can be realized using optical photolithography technology. It can be manufactured by This means that it is possible to easily produce an optical coupler having a diffraction grating with good mass production. An optical coupler with such a configuration can be applied, for example, to a book-shaped light-weight optical memory disk with a direct product of about 5'wm x I Qu+ and a thickness of about I, and is very effective in one-element utilization technology. It is very useful.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a schematic configuration showing an embodiment of the present invention. FIG. 2 is a diagram showing an example of a conventional device. FIG. 3 is a diagram showing an example of a conventional device. FIG. 4 is a diagram of a device improved from the conventional device. 1... Substrate 2... Waveguide layer 3.
--- Unequally spaced curve group diffraction grating 4 --- Guided light 5 --- Diffracted light 6 --- Focal point
7... Linear group diffraction grating 8... Collimating lens (grating lens) 9...
Convex lens 10... Light source (semiconductor laser) 11.
...Input/output end face and above Applicant: Seiko Epson Corporation Figure 1 Figure 2

Claims (1)

[Claims] An optical coupler including a thin film optical waveguide layer formed on the surface of a substrate, which includes a collimating lens and a diffraction grating consisting of a group of straight lines on the surface of the optical waveguide layer, and transmits diffracted light by the diffraction grating to the thin film waveguide layer of the substrate. The diffracted light input/output surface is an end surface of the substrate, and the diffracted light input/output surface is an end surface of the substrate,
An optical coupler characterized by having a convex lens on its surface.