JPS59159105A - optical waveguide - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is directed to optical integration 1! used in the fields of optical communication and optical information processing. ? ] The present invention relates to optical waveguides necessary for optical waveguides and methods for producing the same. In particular, the present invention relates to an optical waveguide made of single crystal with low optical transmission loss, and a method for manufacturing the same.

[Prior art]

2. Description of the Related Art In recent years, the practical application of optical communications has progressed rapidly, and research and development is actively being carried out to make optical components smaller and more reliable. Optical waveguides, which are the main components of optical integrated circuits, have traditionally been
A method of injecting a substance that increases the refractive index into the optical material serving as the substrate by ion implantation or diffusion, or as shown in Fig. 1, a material with a higher refractive index than that of the substrate 1 by using vapor phase growth or liquid phase growth method. The optical waveguide 4 is manufactured by epitaxially growing the single crystal thin film 2 to a desired thickness, and then etching away the portion other than the portion that will become the optical waveguide. However, in the former method, it is difficult to control the cross-sectional shape of the optical waveguide.

There are two methods for using the latter type of etching: wet etching and dry etching, but wet etching is difficult to form fine patterns because etching is performed at the same speed in both the depth direction and the lateral force direction. However, since the etching rate differs depending on the orientation of the crystal, it has the disadvantage that it is difficult to control the shape of the optical waveguide. Dry etching also has advantages over wet etching in controlling the shape of optical waveguides, such as less lateral etching and not depending on the anisotropy of the crystal. There is a drawback that it is difficult to combine the single crystal film 2 and the material for the mask 3. For example, since the dry etching speed of YIG (yttrium iron garnet) based magnetic film is very slow, no suitable dry etching mask material can be found.

[Purpose of the invention]

The purpose of the present invention was to solve these problems, and is to provide a low-loss single-crystal optical waveguide necessary for optical integrated circuits, or a method for forming the same easily and with high precision. It's about doing.

[Summary of the invention]

In other words, the optical waveguide of the present invention is produced by forming a film of an optical material with a refractive index equal to or lower than this on a single crystal substrate, such as Si3N, 3iQ, etc., and then forming a single film by reactive sputtering or the like. Depth 2 for mode transmission to pJ function
width? The optical waveguide is characterized in that a groove is formed therein, and a material having a refractive index of 100% higher than that of the substrate is formed in the groove by epitaxial growth, thereby forming the entire optical waveguide. 1
``In other words, whereas the conventional method for forming an optical waveguide by etching involves forming a thin film single crystal that will become the waveguide and then etching it to form the waveguide, the present invention
The method is characterized in that a groove is formed by etching an optical material such as O2 or 813N4 that will become the cladding, and then a thin film single crystal that will become the waveguide is formed.

S+C) = Alternatively, optical materials such as Si and N4 can be easily formed into fine patterns by reactive sputter etching, and optical waveguides with excellent precision can be formed regardless of the type of single crystal material. It is possible.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 Monosilane and ammonia gas were flowed onto a QaAs substrate 11 (carrier concentration I x 10"tyn-") having a (100) plane, and a thickness of 1 μm was formed by plasma CVD.
A Si, N4 film 12 having a thickness of 100 m was formed as shown in FIG. Grooves 14 having a width of 4 μm and a length of two gates are formed on the Si and N4 films by reactive sputter etching using Freon gas. The groove 14 will later become the outline of the optical waveguide.

Then, high resistance ()aAsA with a carrier concentration of 2×10'f3 is formed in the groove 14 by vapor phase growth (NOCVD method).
1B12 was grown pitaxially to form an optical waveguide 13 as shown in FIG. 2(C). Both end faces of the optical waveguide were cleaved, and a linearly polarized light wave with a wavelength of 1.3 μm was introduced into the optical waveguide having a length of 1.8 μm. The vibration direction of the linearly polarized light is the X-axis direction in FIG. From the near-field batten at the output end face, we confirmed that the optical waveguide with and is a single mode transmission line. The accuracy of the cross-sectional shape of this optical waveguide was ±5% or less, according to the results of measurement using a scanning electron microscope. Further, the optical waveguide Q transmission loss was 1.5 dB/Cm or less.

Example 2 0 on Gd3GasO+z substrate in the same manner as [Example]
, 8 am Si, N4 film is formed, and this Si, N,
A groove with a width of 0.8 μm and a length of 1−1 was formed in the film by reactive sputter etching. Heat this substrate to about 600C, and add YIG (yttrium, iron, garnet) mkQ on top of it.
The YIGk layer 9 formed by frequency sputtering and deposited on the SI3N4 film was removed to make the optical waveguide 13 and the Si, N, and film surfaces almost the same.

Both end surfaces of the optical waveguide were polished, and a linearly polarized light wave with a wavelength of 13 μιη was input into the optical waveguide having a length of 800 μm.

The vibration direction of the linearly polarized light is the X-axis direction as in the first embodiment. Single mode transmission from near field pattern observation 1
- It was confirmed that this was done.

The optical transmission loss was less than 1 dB/m. The accuracy of the waveguide cross-sectional shape was also comparable to that of Example 1.

〔Effect of the invention〕

As shown in the above embodiments, according to the present invention, a crystalline optical waveguide can be fabricated with high precision on a single crystal substrate, and
Even if the substrate material is different, a low-loss optical waveguide can be formed using the same method.

[Brief explanation of the drawing]

No. z1gl(a) to (C) are schematic cross-sectional views showing the optical waveguide manufacturing process by conventional etching, and FIGS. 2(a) to (C)
) is a schematic cross-sectional view showing the manufacturing process of a waveguide according to the present invention. 1]...Substrate crystal, 12...Clad layer, 13...
・Light guiding helmet 1 mouth) 12 (2)

Claims (1)

[Claims] 1. Crystal substrate), K, forms an optical material with a refractive index comparable to or lower than that of the substrate, and has a depth of 2 widths that enables single mode transmission in one axis of this optical material. 1. An optical waveguide characterized in that the optical waveguide is constructed by forming one or more grooves, and forming a substance having a higher refractive index than a substrate in the grooves by epitaxial growth.