JPS5971005A - Forming method of optical waveguide - Google Patents

Abstract

PURPOSE:To diffuse an ion in a substrate and to form an optical waveguide by applying heat to a solid material contg. a seed ion to be diffused on a substrate. CONSTITUTION:Mg(NO3)26H2O, C6H5COOH, etc. are placed on a substrate 1 of a ferrodielectric crystal having an excellent piezoelectric property such as LiNbO3 or glass such as BK7, and a uniform luminous flux 2 is irradiated onto the same from a laser light source 3, a beam splitter 6 and a lens 4. The surface on the substrate 1 is locally heated by the flux 12, and an ion exchange progresses thereon, then the refractive index near the surface increases and a waveguide is formed. The rate of generating harmful gas is suppressed low as compared with the case of heating the entire part. When the refractive index on the surface changes, the reflectivity and transmittance on the substrate surface of the flux 12 change and therefore if the fluctuation in the light intensity is observed with a detector, the state of the waveguide at the point of that time is monitored.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a waveguide for an optical circuit having functions such as elemental synthesis, multi-element demultiplexing, and optical deflection.

Conventionally, as a waveguide substrate with excellent piezoelectricity, a strong Ti film is formed using a method such as an electron gun or sputtering, and then treated in a thermal furnace at around 1000° C. for several hours to form a thick waveguide. However, in the production of the above-mentioned waveguide, a high-temperature treatment process at around 1000°C is involved, and the input source strength to the above-mentioned waveguide is 1 to 1.
If it exceeds 2 mW (at wavelength 0.6328 μm), optical damage will occur in the waveguide (R, L, Ho1rnan,
Appl.

Pbys, Letl, 32, 280 (1978)).

On the other hand) as a method to reduce the optical damage of the above waveguide,
There are methods in which the substrate is immersed in a strong acid, hydroxide, or molten salt heated to about 200°C to 400°C. (J
, Jackel, Appl, Pbys, 14. tJ
, 37.

739, (1980)) For example, as the molten salt, TlNOx, AgN0++
However, since it is necessary to completely immerse the substrate in the molten salt, there is a problem in that a large amount of harmful gases such as NOz are generated due to heating.

An object of the present invention is to provide a new optical waveguide manufacturing method that eliminates the drawbacks associated with the conventional optical waveguide manufacturing methods described above.

In the optical waveguide manufacturing method according to the present invention, a solid material containing ion species to be diffused is provided on a substrate on which a waveguide is to be formed, and the ions are diffused into the substrate by applying heat to the solid material to guide the optical waveguide. It forms a wave path.

The simplest means for applying the heat is, for example, light irradiation such as a laser beam. Furthermore, before applying heat to melt the solid material, it is better to preheat the entire substrate to a certain temperature, of course to a temperature at which the ion species do not dissolve (the optical waveguide can be created). can.

In the optical waveguide fabrication method of the present invention, it is possible to form a photoconductive waveguide with few fabrication techniques. The present invention will be explained in detail below.

In FIG. 1, 1 is a substrate on which an optical waveguide is formed, 2 is a solid material that forms ion species, and the substrate 1
is installed on top of the The substrate 1 is LiNb0g, which is a ferroelectric crystal with excellent piezoelectricity.

LiTa0a crystal or glass such as BK7 may also be used. 2
and L till: Mg(NOs) +B5HzO,
CaHsCOOI4, TlNOs, AgNOs
.

Examples include IGNOs, NaN0a, etc.

FIG. 2 is a diagram showing an embodiment of the method according to the present invention, in which 6 is a laser light source, 4 and 5 are lenses, 6 is a beam splitter, 17 and 8 are photodetectors, 9 is a heating furnace, and 10 is a furnace. It is a window for light opened at 9. The light source is preferably a laser with a wavelength that is highly absorbent to the substrate material, such as ArgHe-Ne, YAG, C02v.
- Ther etc. can be mentioned.

A beam 11 emitted from a laser light source 6 passes through a beam sinter 6 and is expanded into a beam 12 having uniform intensity by a lens 4. The light beam 12 is irradiated onto the surface of the substrate 10 on which the solid 2 containing the diffused species is stacked, and when the solid 2 melts, a part of the light beam 12 is reflected and a part is transmitted. The reflected light returns to lens 4 and beam splitter 6
is guided to the detector 7. On the other hand, the light beam transmitted through the substrate is squeezed by the lens 5 and enters the detector 8.

The surface of the substrate 10 is locally heated by the light beam 12), ion exchange progresses, the refractive index near the surface increases, and a waveguide is formed. The rate of generation of harmful gases is lower than that in the case of heating the entire substrate.Also, as a thermal bias, it is okay to heat the furnace 9 appropriately in advance. According to the principle, when the refractive index of the surface changes, the reflectance and transmittance on the second surface of the light beam 120 substrate change, so if the fluctuation of the light intensity is observed with the detector 7 or 8, the state of the waveguide at that point can be determined. can be monitored.

By the above method, a Granar type waveguide having a predetermined waveguide thickness can be manufactured.

Next, the present invention will be explained in detail with reference to embodiments, but the present invention is not limited to these embodiments.

Example 1 Referring to FIG. 2, both sides of the y-2 plane of an X-cut LiNb0i single crystal were polished so that the surface accuracy was within a few Neutlings. The dimensions of the board are 1 in each of the y and z directions.
inch, 1/2 inch, and the thickness was 1 mm. After polishing, the substrate was ultrasonically cleaned, thoroughly dried in ethanol vapor, and about 2 g of TlN0a powder was evenly deposited on the top surface of the substrate using a doctor blade. The stacked substrates were placed in a low-temperature heating furnace, heated to approximately 100°C, and a Cow laser source (output 2 Qwatts) was applied to the silicon through the furnace window.
After adjusting the lens so that the light hits the entire surface of the board, the TA was piled up on the board within a few minutes! NOs was melted, and a COs laser beam was irradiated for about 60 minutes in this state to form a TEo mode waveguide on the υ substrate due to internal diffusion of e ions.

When we measured the propagation loss of the waveguide created by the prism coupling method, we found that: 1. Values in Odb/cm were obtained. Furthermore, an improvement of 50 degrees was observed in terms of the threshold value for optical damage, indicating that the waveguide fabrication method according to the present invention is superior to the conventional method.

As explained above, the method for fabricating an optical waveguide according to the present invention! This not only makes it possible to create an optical waveguide with less optical damage and lower optical propagation loss (compared to the conventional method of fabricating a substrate by immersing it in a melt heated to a high temperature),
Low-temperature processing is possible, and the generation rate of harmful gases can also be suppressed.

In addition, since the state of the waveguide can be monitored during waveguide fabrication, it is possible to control the number of excited modes and improve elasticity! (It is also possible to control the waveguide thickness so that the interaction with the 1 m wave is strong.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams illustrating an embodiment of a method for producing an optical waveguide according to the present invention. 1...Substrate, 2...Solid containing diffused ionic species 16...Light source, 4.5...e-fist lens, 6Φ
...Φ Beam Gritter 17,8@...Photodetector, 9...Member/Heating Furnace, 10...Window, 11,1
2... Luminous flux. Applicant Canon Co., Ltd. shell r','-; 84 Fee No. 2ρ 19-

Claims (2)

[Claims] (1) Creation of an optical waveguide characterized in that an optical waveguide is formed by providing a solid that forms ionic species to be diffused on a substrate and applying enough heat to diffuse the ionic species into the substrate. Method. (2) The method for producing an optical waveguide according to claim 1, wherein the ion species are irradiated with light to diffuse the ion species into the substrate.