JPS63309904A - Production of light guide - Google Patents

Abstract

PURPOSE:To improve the confinement of light and to produce uniform light guides by forming a 1st thin film having the refractive index lower than the refractive index of an LiNbxTa(1-x)O3 (O<=x<=1) substrate on said substrate and forming a 2nd thin film having a higher refractive index and a light transmission region in a visible light part into the grooves formed by etching in the substrate. CONSTITUTION:The 1st thin film 10 having the refractive index lower than the refractive index of the LiNbxTa(1-x)O3 (O<=x<=1) recording medium 1 is formed on the surface of the substrate and part of the thin film 10 is selectively removed by using selective etching to selectively form the grooves 30 in the substrate 30. The 2nd thin film 40 which has the refractive index higher than the refractive index of the substrate 1 and having the transmission region in the visible light region is further formed in the grooves 30. Namely, the formation of the uniform light guides by using the method of the dry etching and the thin film formation which are extremely high in dimensional controllability is enabled. The light guides of a flush type having an extremely large difference in the refractive index are thereby formed and the formation of the guides with the good reproducibility of the width thereof is possible as well.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing an optical waveguide used in the fields of optical communication and optical applied measurement.

2. Description of the Related Art Conventionally, optical waveguides have been formed on the surface layer of a LiNbO3 substrate, which is a ferroelectric substrate, using photoprocessing or etching techniques, and used for optical switches and optical modulators. For example, C1, Ljack
el, C, E, Rics, and Tj, Veselk
a “Proton exchange for high
h-index wave guides in LiNbO
3, “Apply Physics Letter (Appl,
Phys, Lett) vol 41, No.
7, pp, 607-eos, (1sa2)).

Hereinafter, an optical waveguide will be taken as an example of an optical element, and a manufacturing method thereof will be described. FIG. 2 shows a specific configuration diagram of a method for manufacturing an optical waveguide using a conventional proton exchange method. 1 is a ferroelectric substrate L z N b Os substrate, 2 is an Ad
A protective mask made of gold metal; 4 is a slit formed on the protective mask 2 by photo process and etching;
6 is an optical waveguide made of a proton exchange layer formed in benzoic acid 6 at 230°C. e is 230' (: benzoic acid, 7 is a heater, and 8 is a quartz beaker.

Problems to be Solved by the Invention However, in the method for manufacturing an optical waveguide as described above, L
The refractive index difference between the iN b Os substrate 1 and the proton exchange layer 6 is as small as +0.12, and the optical propagation loss of the proton exchange layer is extremely large as 2 to 3 dB/an.

Therefore, light confinement is weak (conventional methods use curved waveguides, for example, nonlinear optical elements that output second harmonic light of input light, that is, SHG (SecondaryHarm
There have been problems in that it is difficult to fabricate an on ic gonera tion) element, and furthermore, it is not easy to form a uniform waveguide.

In view of the above problems, the present invention provides LiNb, Ta(1-x)
03 This is what we provide.

Means for Solving the Problems In order to solve the above problems, the method for manufacturing an optical waveguide of the present invention includes LiNbxTa(1,)03(Ox<;:1)
A first thin film having a refractive index lower than that of the substrate is formed on a substrate, a groove is formed by etching on the substrate, and a first thin film having a refractive index higher than that of the substrate and whose visible light portion is a light transmitting region is formed in the groove. The second method is to form a thin film.

Operation According to the present invention, an optical waveguide which is a buried type and has a large refractive index difference with the substrate is formed by the method described above. moreover,
For proton exchange, the optical waveguide width.

The depth etc. change depending on various conditions such as diffusion time and temperature, and it is difficult to control these conditions uniformly, so it is not easy to form a uniform optical waveguide. The present invention makes it possible to form a uniform optical waveguide using dry etching and thin film formation, which are methods with extremely high dimensional controllability.

EXAMPLE Hereinafter, a method for manufacturing an optical waveguide according to an example of the present invention will be explained with reference to the drawings.

FIG. 1 shows a process cross-sectional view of the method for manufacturing an optical waveguide of the present invention. In FIG. 1, the process of (al is +Z
Plate (+Z-axis vertical M'x plane) ノ L I N bOs
A Si02 film 1o is deposited on the substrate 1 by sputtering to a thickness of 0.3 μm. That is, using an RF discharge sputtering device, 4ooW, Ax gas 20sccm, total pressure 5X10-'
This is a process in which the sputtering rate is 150 persons/min and 20 ml under the target condition of Torr 5 to 2. The process (b) is performed using Microposit 3140.
In this step, a resist pattern 3 of 0.4 .mu.m is formed by patterning using a photolithographic process according to steps 0-17. In step fc), the pattern of the resist 3 is transferred onto the LIN b Os substrate 1 using molecular beams, and etched by 0.5 μm.

That is, 5iO 310 and the substrate 1 are etched using the resist pattern 3 as a mask to form a groove pattern on the substrate 1. In the step (d), after the step (C), T z 02
In the process of vapor depositing by sputtering, an RF discharge sputtering device was used with 40 oW, Ar gas x 2 osccm, and a total pressure of 1
．． 5 X 1O-5 Torr, 5O at a sputtering rate of 100 people/min under the conditions of TlO2 target.
This is a process that is performed for min. In this process, T z0 is applied to the groove 30.
Two optical waveguides 40B are formed. MoTl on 510210
o24oA is formed. 1 is a +Z plate LiN [3 substrate, 1o is an 8102 film with a thickness of 0.3 μm and a refractive index of 1.46 lower than substrate 1, and 3 is a microposit S
1400-17 (Six Play Company) with a thickness of 0.4 μm. The groove 3o is a groove with a width of 1 μm formed by molecular beam etching using the resist pattern 3 formed in the step (b) as a mask, and the groove 40B is a groove of (C
) T z O2 having a refractive index of 2.40, which is higher than that of the substrate 1, and having a thickness of O, S μm.
It is a membrane waveguide. 40A is 40B on top of Sio2 film 1o
Simultaneously deposited with a thickness of 0.5 pm and a refractive index of 2.4.
o TlO2.

The method for manufacturing the optical waveguide as described above will be further explained. All processes of the present invention are performed in a dry process, and the grooves can be formed uniformly with good reproducibility.The slit width of the resist pattern formed by the photo process is equal to the waveguide width, and the reproducibility is also very good. be. Furthermore, it can be manufactured through a relatively simple process, and a refractive index difference greater than that achieved by the proton exchange method can be obtained, resulting in better light confinement.

In this example, a 0.3 pm SiO2 film 10
was formed by sputtering, a 0.4 μm resist 3 pattern was formed on it, and a 0.4 μm resist pattern was formed by molecular beam etching.
．． A 6 μm groove 3o is formed on the LiNbO3 substrate 1, and a 0.5 μm T102 film is formed on it by sputtering. Various thicknesses and forming methods can be used. The thickness of the resist 3 can be arbitrarily selected, and various etching methods and depths can be used for forming the grooves 30, and the forming method and thickness of the T102 film can also be arbitrarily selected. In addition, as the substrate 1, not only LiNbO3 but also Lii'Jb
xTa(1−x)03(0<;:x<;:1) is applicable.

Effects of the Invention As described above, the present invention includes the steps of forming a thin film with a refractive index lower than that of the substrate, forming grooves on the substrate by etching, and forming a thin film having a higher refractive index than the substrate thereon. By using this process, an embedded type optical waveguide with a large refractive index difference can be formed, and the waveguide width can be formed with good reproducibility.
This will greatly contribute to the industrial production of optical waveguides.

[Brief explanation of drawings]

FIG. 1 is a process sectional view showing a method for manufacturing an optical waveguide in an embodiment of the present invention, and FIG. 2 is an explanatory diagram for explaining a method for manufacturing an optical waveguide using a conventional proton exchange method. 1...LzNbOs substrate, 3...
...Resist, 1°...Sio2.3o...
... Groove, 40B... Optical waveguide. Name of agent: Patent attorney Toshio Nakao and one other person; Suga Ward 8-? Q-

Claims (2)

[Claims] (1) LiNb_xTa_(_1_-_x_)O_3(
0≦x≦1) Forming a first thin film having a lower refractive index than the substrate on the surface of the substrate, selectively removing a part of the thin film using selective etching, and forming grooves in the substrate. A method for manufacturing an optical waveguide comprising the steps of selectively forming a second thin film having a higher refractive index than the substrate and having a transparent region in the visible light region in the groove. (2) LiNb_xTa_(_1_-_x_)O_3(
0≦x≦1) Claim 1 in which the substrate is a +Z board
1. Method for manufacturing an optical waveguide as described in .