JPH01116502A - Optical waveguide element and its manufacture - Google Patents

Abstract

PURPOSE:To generate no crack nor roundness in the end face of an optical waveguide element and to decrease a loss of light by burying the end part of a first optical material into a second optical material, and also, forming a curved surface-like projecting part, in the optical waveguide element in which the periphery of a first linear optical material has been covered with the second optical material whose refractive index is lower than that of the first optical material. CONSTITUTION:In an optical waveguide element 5 consisting of the first linear optical material and the second optical material 7 whose refractive index is lower than that of the first optical material 6, an end part 8 of the second optical material 7 forms a plane, and an end part 9 of said first optical material 6 of the same side as the end part 8 of the second optical material 7 is buried into the second optical material 7, and also, forms a curved surface-like projecting part. In such a way, a crack and roundness are not generated in an edge part of an optical waveguide consisting of the first optical material for forming an optical waveguide element, therefore, a light beam which has been introduced does not cause scattering and refraction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical waveguide element used, for example, in an optical integrated circuit, and a method for manufacturing the optical waveguide element.

[Prior Art] Conventionally, an optical waveguide device has a light path in which Li is ion-exchanged (proton-exchanged) with H in a crystal of lithium niobate (Nb03), which is an optical material 1, as shown in FIG. 9, for example. The optical waveguide 2 is manufactured by adding titanium oxide (Ti 02 ) to the lithium niobate (Li Nb 03 ) of the optical material 1, which increases the refractive index of the optical material.
It is known that the optical waveguide 2 is manufactured by diffusing the light. The method for manufacturing an optical waveguide element using proton exchange and the optical waveguide element are manufactured by NIKKEN ELECT-RONIC.
31986, 7, 14, P, 90, lines 3 to 10.

Further, for example, magnesium oxide (Mac) which reduces the refractive index of this optical material is further diffused into the optical material 3 of the optical waveguide device manufactured above as shown in FIG. 9, and as a result, as shown in FIG. A method of manufacturing an optical waveguide 4 having a higher refractive index than its surroundings in the above-mentioned optical material is known.

[Problems to be Solved by the Invention] In order to introduce, for example, laser light into the optical waveguide device manufactured by the above technique, it is necessary to bond a glass fiber to the end face of the optical waveguide device or to introduce it through an optical lens. Introduce light. Therefore, the end face of the optical waveguide element must be a mirror surface. Particularly, if there is a chip or roundness at the edge of the end face of the optical waveguide element, there is a problem in that light scattering or refraction occurs, resulting in light loss between the glass fiber and the optical waveguide element. Furthermore, it is extremely difficult to process the end face of an optical waveguide element without causing chipping or rounding.

[Means for Solving the Problems] In order to solve these problems, the configuration of the optical waveguide element of the first invention of the present application is as illustrated in FIG. and a second optical material 7 existing around the second optical material 7 and having a lower refractive index than the first optical material 6, the end portion 8 of the second optical material 7
forms a plane, and the end 9 of the first optical material 6 on the same side as the end 8 of the second optical material 7 forms a second optical material 7.
The optical waveguide element 5 is characterized in that it is buried inside and forms a curved convex portion.

On the other hand, the configuration of the method for manufacturing an optical waveguide element of the second invention is such that light is diffused into the optical material on the side surface of the optical material, which has a planar end surface through which light is input/output, and a side surface parallel to the direction in which the light travels. A first refractive index adjusting agent that increases the refractive index of the optical material is attached and diffused in a band shape in the direction of light propagation, and then diffused into the optical material to decrease the refractive index of the optical material. Manufacture of an optical waveguide element in which an optical waveguide having a higher refractive index than the surroundings is provided in the optical material by depositing a second refractive index adjusting agent over the adhering portion of the first refractive index adjusting agent and diffusing it. In the method, the tips of the parts to which the first refractive index adjusting agent and the second refractive index adjusting agent are attached do not reach the end surface, and the tips bulge out in a curved shape, and the tips further extend from the center of the tips. This is a method of manufacturing an optical waveguide element, characterized in that the amount of adhesion decreases as it approaches the bulge edge.

[Function] When introducing a laser beam from, for example, a glass fiber into the optical waveguide element 5 of the first invention, first, the glass fiber is attached to the end face of the second optical material 7 of the optical waveguide element 5 of the first invention. Glue. Thereby, the laser beam from the glass fiber enters from the end surface 8 of the second optical material 7 and propagates through the second optical material 7. The laser beam propagated through the second optical material 7 reaches the curved convex portion 9 at the end 9 of the first optical material 6, and passes through the first optical material 6 having a higher refractive index.
Due to the curved convex portion of the light, the light is not scattered around, but is converged and guided into the first optical material 6. Thereby, the laser beam propagates from the second optical material 7 into the first optical material 6.

On the other hand, the method for manufacturing an optical waveguide element according to the second invention is as follows. A first refractive index adjusting agent is attached to the side surface of the optical material in the form of a band in the direction in which light travels. In particular, the tip of the band-shaped attached portion does not reach the end surface of the optical material, the tip of the attached portion bulges out in a curved manner, and the amount of adhesion increases as the tip approaches the bulged edge from the center of the tip. However, it adheres to decrease. Note that the first refractive index adjusting agent diffuses into the optical material and increases the refractive index of the optical material in accordance with the concentration of the refractive index adjusting agent. After attaching the first refractive index adjusting agent to the optical material, the optical material is heated.
Spread. As a result, the first refractive index adjusting agent is diffused into the optical material and forms a portion with an optically high refractive index depending on the concentration. In particular, the tip portion of the first refractive index adjusting agent that is diffused in the direction of propagation of light exhibits a refractive index distribution, for example, as shown by the curve formed by ■ and ■' in FIG.

Next, a second refractive index adjusting agent is attached to the position of the optical material where the first refractive index adjusting agent is attached in the same proportion as the first refractive index adjusting agent.

Note that the second refractive index adjusting agent diffuses into the optical material and reduces the refractive index of the optical material in accordance with the concentration of the adjusting agent. After the second refractive index adjusting agent is attached to the optical material, thermal diffusion is performed. Thereby, the second refractive index adjusting agent attached to the side surface of the optical material is diffused into the optical material along with the first refractive index adjusting agent that has been previously diffused into the optical material.

As a result, in the portion where the first refractive index adjusting agent and the second refractive index adjusting agent are mixed in the optical material, the second refractive index adjusting agent has a refractive index that is lower than that of the first refractive index adjusting agent. It acts to lower it. In particular, the tip portions consisting of the diffused first refractive index adjusting agent and second refractive index adjusting agent are
The refractive index distribution shown by the curve consisting of is shown. Finally, an optical waveguide is formed in the optical material, as shown in FIG. 5, where the center portion has a high refractive index and the refractive index distribution at one tip portion forms a convex surface. .

As a result, the end face 8 of the optical waveguide element 5 is not adversely affected by rounding or chipping of the edge portion, which tends to occur when processing the end face 8 into a rough surface. The position of the high refractive index portion in the optical material can be adjusted by the position attached to the side surface of the optical material, the amount of each refractive index adjusting agent, and the temperature and time of diffusion.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a partial perspective view of the vicinity of an end of an embodiment of an optical waveguide element according to the present invention. The optical waveguide element 5 of this example is:
A linear first optical material 6 having a high optical refractive index (for example,
an optical material containing one or more selected from titanium oxide (TiO2), zinc oxide (ZnO), nickel oxide (NiO), etc., and a lower refractive index than the first optical material 6 around it. A second optical material 7 (for example, one selected from lithium niobate (Li Nb 03 ), lithium tantalate (Li 'ra 03 ), etc.) of The end 8 of the second optical material 7 is flat, and the end 9 of the first optical material 6 on the same side as the end 8 of the second optical material 7 is flat.
It is buried in the optical material 7 and forms a curved hexagon.

The method for manufacturing the optical waveguide device of this embodiment having the above-described structure uses lithium niobate (Li Nb 03
) on the surface of titanium (Ti) by photolithography.
> is patterned and subjected to thermal diffusion treatment, and then magnesium oxide (MgO) is similarly patterned and thermal diffusion treatment is performed.

The processing process will be described in detail below based on FIGS. 2, 3(A), and 3(B).

FIG. 2 shows photolithographic processing of optical materials. First, optical material 7, lithium niobate (Li Nb 03
) A thin film of photosensitive photoresist 11 is deposited on the surface 10 (FIG. 2(a)). Next, titanium (Ti), which is the first refractive index adjusting agent, is added to lithium niobate (L), which is the optical material 7.
i Nb 03 ), for example, a mask 12 is placed on the surface 11 on which the thin film of photoresist 11 shown in FIG. 2(b) is attached except for the pattern EDBGF shown in FIG. 3(A). do. When exposed through the mask (FIG. 2(b)), only the exposed portions of the photoresist 11 react and become soluble in the developer.

When this exposed material is treated with a developer, a portion where the photoresist 11 remains and a portion 13 where the photoresist 11 is melted and the optical material 7 appears are formed. (Figure 2 (C))
The portion 13 where the optical material 7 appears corresponds to the figure EDBGF shown in FIG. 3 (A>. Titanium (Ti> (Fig. 2(d)). The method for depositing a thin film of the first refractive index adjusting agent on the optical material may be a vacuum evaporation method. Fig. 4 is a partially broken perspective view of an optical material sputtered with titanium (T1).The distribution amount of the sputtered titanium (T1) is as shown in Fig. 4. is the titanium (Ti) of the quadrilateral EDGF part.
> thickness is 700A. In addition, the thickness of titanium (Ti) in the semi-inner portion DBG0 part is such that the thickness of titanium (Ti) decreases in a 700 line shape at point O, centering on the center O of the semicircle. The distribution amount (thickness) of the DBGO radius OB force direction thin film deposited is shown in Figures 8 (A) to (E), for example.
) may be similar to the diagram of the distribution amount shown in . In order to deposit a thin film with such a distributed amount, the refractive index adjusting agent is deposited in a thin film using a slit as shown in FIG. 7(A).

This slit is used to obtain the desired distribution amount of the refractive index adjusting agent by adjusting the number of holes of the slit having the same diameter in the direction of the circular arc DBG from the center O of the semicircle. Also, Figure 7 (B)
A slit as shown in can also be used. This slit is designed to obtain a desired distribution amount of the refractive index adjusting agent by adjusting the area of one hole of the slit and the number of slits in the direction of the circular arc DBG from the center O of the semicircle. Thereafter, the photoresist 11 is dissolved in acetone and subjected to ultrasonic cleaning to obtain a material in which titanium (Ti) is sputtered on the surface 10 of the optical material lithium niobate (Li Nb 03 ) (FIG. 2(e)).

Next, the material sputtered with titanium (Ti) was
Heat diffusion is carried out for 8 hours at a temperature of 1 ooo'c, thereby:
Titanium (Ti) is an optical material lithium niobate (Li
Nb 03 ).

Next, the above-mentioned titanium (Ti>) is added to the surface 1 of the optical material 7.
In the same way as 0 is patterned by photolithography and thermal diffusion treatment is performed, magnesium oxide is patterned by photolithography on the same surface 10 of the optical material 6 in which titanium (Ti) is diffused, and thermal diffusion treatment is performed. That is, as shown in FIG. 2(f), the titanium (T
A thin film of photoresist 11 is deposited on the surface 17 of the optical material 16 patterned with i>. Next, a mask 12 that exposes the photoresist in the same area as the area where the first refractive index adjusting agent, titanium (Ti), has been deposited in a thin film is applied to the surface on which the thin film of photoresist has been deposited (FIG. 2 (g)). . After exposure through the mask 12, it is processed with a developer.

As a result, a portion where the photoresist 11 remains and a portion 18 where the photoresist 11 is melted and the optical material 16 is exposed are formed (FIG. 2(h)). The portion 18 where the optical material 16 appears corresponds to the figure EDBGF shown in FIG. 3 (A>).

Magnesium oxide (Ma 2 O), which is the second refractive index adjusting agent 15, is sputtered onto the portion 18 where the optical material 16 appears (second (i)). Magnesium (Mg) and magnesium oxide (Mc+O) are scattered onto the optical material 18 and photoresist 11 by the sputtering. Incidentally, the method for depositing a thin film of the second refractive index adjusting agent on the optical material may be a vacuum evaporation method. The 9 distribution of magnesium (M(]) by sputtering of the magnesium oxide (M(lO)) shown in FIG. 3(B) is
The concentration distribution is as shown in the figure. In the embodiment of the present application, the thickness of magnesium (Mq) in the quadrilateral EDGF portion is 250A. In addition, the thickness of magnesium (Mg) in the DBGO part of the hand is centered around the center O of the semicircle.
At point O, the thickness of magnesium (Mg) is 25 OA, and the thickness decreases parabolically in the radial direction. The applied distribution amount in the radial direction of the semicircular portion DBG0 and the method of applying the thin film on the distribution amount are as follows.
> is similar to the case where a thin film is attached. Thereafter, the photoresist 16 is dissolved in acetone and subjected to ultrasonic cleaning to produce optical material lithium niobate (L! Nb 03).
) is obtained by sputtering magnesium (Mg) onto the surface 17 (Fig. 2 (j)).

Next, the magnesium (Mg) sputtered material is subjected to thermal diffusion at a temperature of 950'C for 3 hours. As a result, the titanium (-r; > that was previously diffused into the optical material) and the sputtered magnesium (Mg) and magnesium oxide (Mob) are diffused into the optical material. As a result, titanium is removed from the substrate surface of the optical material. (Ti) diffuses to a depth of 7 to 8 μm, and magnesium (Ma) diffuses to a depth of 1 μm. The distribution of the optical refractive index in the optical material 16 produced in this way is shown in FIG. ＞ is shown by equirefractive index lines n1 to n as shown in FIG. 5 (however, nl <
n2 <r13 <r14 <r15 <n) a
As shown in FIG. 6, titanium (
The refractive index distribution due to the second refractive index adjusting agent φmagnesium (
The refractive index distribution due to Mg ) is expressed by a curve made up of ■. As titanium (Ti) as the first refractive index adjusting agent and magnesium (M(1) as the second refractive index adjusting agent) are diffused, the above-mentioned double convex lines are combined, and the refractive index of both figures is adjusted. The refractive index distribution due to the titanium (Ti) and magnesium (MO) agents becomes A wave path is formed, and the end portion thereof exhibits a spherical refractive index distribution.

As explained above, by diffusing the predetermined first refractive index adjusting agent and second refractive index adjusting agent into the optical material, an optical waveguide having a high refractive index is formed in the optical material as shown in FIG. is provided, and its tip portion forms a curved convex portion. As a result, since the tip of the optical waveguide is in the optical material, it will not be chipped or rounded. In addition, since the tip of the optical waveguide forms a curved convex portion, the light introduced into the optical material is converged without being scattered when it propagates through the optical material and reaches the tip of the optical waveguide. This has the effect of being guided into an optical waveguide in an optical material.

In addition, as shown in FIG. 3(A), the first part of the semicircular DBGO part
and 15 minutes by sputtering of the second refractive index modifier.
The mother may have a square distribution or an exponential distribution in the radial direction from the center point O of the DG. That is, the distribution of titanium (-r; > and magnesium (Mg) may be such that the end of the optical waveguide is convex in terms of refractive index and has a lens effect in the optical material.

[Effects of the Invention] As detailed above, the optical waveguide element of the first invention includes a second optical material having a lower refractive index than the linear first optical material around the linear first optical material. The end of the first optical material that is embedded in the second optical material forms a convex portion on the curved surface. As a result, there is no possibility that the optical waveguide made of the first optical material forming the optical waveguide element of the present invention will be chipped or rounded, especially at the edges. When light is introduced into the optical waveguide element of the present invention, the end of the optical waveguide through which the light passes is not chipped or rounded, so there is an effect that no scattering or refraction of light occurs.

Next, according to the method for manufacturing an optical waveguide element of the second invention, the first refractive index adjusting agent applied in a predetermined shape is diffused, and the second refractive index adjusting agent is further applied to the first refractive index adjusting agent. The agent is applied to the same area and thermally diffused.

As a result, a portion in which the first refractive index adjusting agent and the second refractive index adjusting agent are mixed and a portion consisting of the first refractive index adjusting agent are formed in the optical material, and a portion consisting of the first refractive index adjusting agent is formed. In the portion where the index adjusting agent and the second refractive index adjusting agent are mixed, the refractive index of the first refractive index adjusting agent is lowered by the second refractive index adjusting agent. Further, since the attached shape has a predetermined shape and thickness distribution, an optical waveguide with a high refractive index having a convex portion having a curved refractive index at the tip is provided in the optical material. When light is introduced into an optical waveguide element equipped with this optical waveguide, the light propagates through the optical material of the optical waveguide element and reaches the end of the optical waveguide, where it is converged and guided to the optical waveguide.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view of the vicinity of the end of an embodiment of an optical waveguide device according to the present invention, FIG. 2 is an explanatory diagram of the photolithography process of the embodiment, and FIG. FIG. 3(B) is a perspective view of the end of the optical material of the example, and FIG.
The figure is a characteristic diagram showing the concentration of each refractive index adjusting agent attached to the optical material of the same example. Figures 5 and 6 are distribution diagrams of the refractive index from the substrate surface of the optical waveguide element of the same example. , Fig. 7 (A
), (B) are illustrations of slits to which the refractive index adjusting agent of the same example is attached, FIG. 8 is an illustration of the amount of deposited refractive index adjusting agent of the same example, FIGS. 9 and 7...・Second optical material 8
...End portion 9 of second optical material...End portion 14 of first optical material...First refractive index adjusting agent 15...Second refractive index adjusting agent

Claims (1)

[Scope of Claims] 1. An optical waveguide element comprising a linear first optical material and a second optical material surrounding it and having a lower refractive index than the first optical material, The end of the optical material forms a plane, and the end of the first optical material on the same side as the end of the second optical material is buried in the second optical material and forms a curved convex part. An optical waveguide element characterized in that: 2. A first refractor that diffuses into the optical material and increases the refractive index of the optical material, on the side surface of an optical material that has a planar end surface through which light enters and outputs and a side surface that is parallel to the direction in which the light travels. A second refractive index adjusting agent is applied to the first refractive index adjusting agent, which is attached and diffused in a band shape in the direction of light propagation, and then diffused into the optical material to reduce the refractive index of the optical material. In the method for manufacturing an optical waveguide element, the first refractive index adjusting agent and the second refractive index agent are superimposed on the attached portion of the agent and diffused to form an optical waveguide having a higher refractive index than the surroundings in the optical material. The tip of the rate adjusting agent-attached portion does not reach the end surface, the tip bulges out in a curved shape, and the amount of adhesion decreases as the tip approaches the bulge edge from the center of the tip. A method for manufacturing an optical waveguide element.