JPH11337759A - Production of optical waveguide element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To substantially obviate the occurrence of difficulty in workability in putting into packages even in the case a substrate is obliquely connected by producing optical waveguide elements by cutting the substrate in such a manner that optical waveguide ends have an finite angle from perpendicularity to their end face and that the direction of the phase shift optical waveguides is not aligned to the ridge line direction of the flanks of the substrate. SOLUTION: The substrate is cut in such a manner that the optical axis at the ends of the optical waveguides 14 and the normal of the cut surfaces (element coupling end faces 4) attain an angle of α=5.4 to obtain the plural optical waveguide elements 1 of a parallelogram. On the other hand, the fiber coupling end face 23 of the optical fiber 20 to be optically coupled to the element coupling end face 4 of each of these optical waveguides 14 is formed by polishing in such a manner that the normal thereof attains the angle of β=8.0 deg.. A UV curing type adhesive is used for optical coupling of the element coupling end face 4 and the fiber coupling end face 23. The state that the entire part is crooked by the flexing as a result of connection of the optical fiber 20 and the optical waveguide element 1 is drastically reduced is such a manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical waveguide device such as an optical modulator and an optical electric field sensor using an optical waveguide formed on a substrate exhibiting an electro-optic effect.

[0002]

2. Description of the Related Art Many optical waveguide elements used for devices such as optical modulators and optical electric field sensors are manufactured using a substrate exhibiting an electro-optical effect such as lithium niobate as a substrate. The optical waveguide element is manufactured by forming a modulation electrode in the vicinity of a phase shift optical waveguide of an optical waveguide type branch interferometer formed by thermal diffusion of Ti on a crystal substrate of lithium niobate.

Usually, a plurality of such patterns of the optical waveguide device are formed by periodically arranging a plurality of patterns on a single crystal substrate and cutting them into a square to obtain many devices at once. . Optical waveguide device fabrication techniques include vapor deposition or sputtering techniques, photolithography techniques,
Semiconductor technology such as microfabrication technology is used.

[0004]

Conventionally, an optical waveguide element has been processed into a rectangular shape, and its end face is perpendicular to the optical axis of the incident optical waveguide, also for reasons of demand for ease of manufacture. . On the other hand, the optical fiber optically coupled to the optical waveguide element is often formed such that its end face is perpendicular to the optical axis. For this reason, at the coupling portion between the end face of the incident optical waveguide and the optical fiber, the incident light is partially reflected at the exit end face of the optical fiber or at the incident end face of the optical waveguide. This reflected light propagates as return light in the same optical fiber in which the incident light has propagated, and returns to the light source. This causes unstable operation of the light source.

Measures have been taken to prevent reflected light from the end face from returning to the light source through the optical fiber. FIG. 5 is a diagram showing a conventional reflection type optical waveguide device. FIG. 5A is a diagram in which an optical fiber is connected to a rectangular waveguide element. FIG. 5B is an enlarged explanatory view of a coupling portion between the optical waveguide element and the optical fiber. FIG.
In (b), each normal line of each end face and each auxiliary line indicating the optical axis direction of the optical fiber are added.

In FIG. 5A, the outer shape of the optical waveguide element 3 is rectangular, but the end of the optical waveguide 16 does not cross the end face of the optical waveguide element 3 at right angles. FIG.
In (b), the end face of the ferrule (not shown) connected to the optical waveguide element is naturally formed not at a right angle to the length direction but at a certain angle.

[0007] As shown in FIG.
The optical fiber 22 has an element coupling end face 4 and a fiber coupling end face 23 for optically coupling with each other. Assuming that the angle between the optical waveguide 16 and the normal a of the element coupling end face 4 is α and the angle between the optical axis b of the optical fiber 22 and the normal a of the fiber coupling end face 23 is β, Satisfies the Snell's law shown in the following equation (1).

Sin α / sin β = n ₂ / n ₁ (1) where n ₁ and n ₂ are the refractive indexes of the optical waveguide 16 and the optical fiber 22, respectively.

In the following, the optical waveguide device is formed on a lithium niobate substrate, and n ₁ = 2.22;
It is assumed that each value of n ₂ = 1.50 is used.

Conventionally, in many cases, the angle formed by the optical waveguide with respect to the normal of its end face is 5.4 degrees, and the angle formed by the optical fiber with the normal of its end face is adjusted to 8.0 degrees. Was connected.

However, an optical waveguide element having a rectangular outer shape
When an optical fiber is connected with a ferrule, it bends,
The overall shape is "K". Implementation in the package,
As a whole, it is in the state of a "ku" shape, handling is difficult, and workability is reduced.

Accordingly, the present invention provides a method for manufacturing an optical waveguide element which does not substantially cause difficulty in workability in mounting on a package even when the optical waveguide element and the optical fiber are so-called diagonally connected. Present.

[0013]

According to the present invention, there is provided an optical waveguide device in which an optical waveguide and a phase-shifted optical waveguide branched from the optical waveguide are formed on a substrate. It is characterized in that the substrate is cut and manufactured so that a finite angle is formed from the perpendicular to the end face and the direction of the phase shift optical waveguide does not coincide with the ridge direction of the side surface of the substrate.

In the case of the reflection type optical waveguide device, further, the phase shift optical waveguide is arranged so as to intersect perpendicularly with its end face.
The substrate is manufactured by cutting.

Further, in the present invention, the optical waveguide device has a Z-plate of lithium niobate crystal as a substrate, and the direction of the phase shift optical waveguide formed on the substrate is in the X direction or the Y direction of the crystal axis. And manufactured by cutting the substrate.

Alternatively, in the present invention, the optical waveguide element is formed such that the X-plate of lithium niobate crystal is used as a substrate, and the direction of the phase shift optical waveguide formed on the substrate is the Y direction of the crystal axis. Then, it is manufactured by cutting the substrate.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing a method of manufacturing a transmission type optical waveguide device according to the present invention. FIG. 1A is a plan view, and FIG. 1B is an enlarged explanatory view of a coupling portion between an optical waveguide element and an optical fiber in FIG. 1A. FIG.
FIG. 3B shows a normal line of each end face and an auxiliary line indicating the optical axis direction of the optical fiber. The optical waveguide element 1 has a substrate 11 made of a lithium niobate crystal exhibiting an electro-optical effect,
A plane cut out perpendicular to the Z axis, that is, a Z plate is used, and the phase shift optical waveguide is in the X direction of the crystal axis.

FIG. 2 is a sectional view of a branching interference type transmission type optical waveguide device formed on a substrate made of a Z plate, which is cut off based on a plurality of patterns. The phase shift optical waveguide 13 is formed in the X direction. A pattern of seven branch interference optical waveguides was formed on a lithium niobate crystal substrate 12 having a diameter of 3 inches, and a modulation electrode 18 was formed of gold (Au) near 13 of the phase shift optical waveguide. This method uses Ti thin film formation, photolithography technology,
It is based on a known technique such as thermal diffusion, sputtering or vapor deposition technique, and a detailed description thereof is omitted.

Here, the shape of the optical waveguide element 1 to be obtained is a parallelogram, and the sides along the phase shift optical waveguide are not parallel. The angle between them can be set according to the pattern of the optical waveguide and the modulation electrode.

Then, as shown in FIG. 2, the substrate 12 having a diameter of 3 inches is parallelly arranged along the longitudinal direction of each branch interference type optical waveguide so that each section includes one branch interference type optical waveguide. Cut into pieces. Further, two parallel sides that are adjacent and opposed to each side formed by the cutting are defined by the optical axis at the end of the optical waveguide 14 and the normal line of the cut surface (element coupling end surface) being 5 °. By cutting at an angle of 0.4 °, a plurality of parallelogram optical waveguide devices 1 were obtained as shown in FIG.

On the other hand, as shown in FIG.
Optical fiber 20 optically coupled to the element coupling end face 4
The fiber coupling end face 23 is formed by polishing such that the normal line forms an angle of 8.0 °. An ultraviolet curing adhesive is used for optical coupling between the element coupling end face 4 and the fiber end face 23.

An optical waveguide element in which a phase shift optical waveguide in the Y direction of the crystal axis is formed on the substrate 11 of the Z plate is manufactured in the same procedure as described above.

FIG. 3 is an explanatory view for manufacturing a reflection type optical waveguide device. That is, the phase shift optical waveguide 1
Cutting the crystal substrate 12 so that it intersects perpendicularly with the end face of 3 is added to the method described above.

FIG. 4 shows a lithium niobate crystal X plate, that is, a substrate 11 having a plane cut out perpendicular to the X axis.
FIG. 2 is a diagram illustrating a configuration of a reflection type optical waveguide element 3 on which a phase shift optical waveguide 13 is formed. The modulation electrodes 18 are formed on both sides of the phase shift optical waveguide 13 on the substrate 11 so that an electric field is applied in parallel with the surface of the substrate 11.

The shape of the optical waveguide element is a parallelogram, and the side along the phase-shifted optical waveguide is cut out so as not to be parallel to the phase-shifted optical waveguide, and is bent by connecting the optical fiber and the optical waveguide element. The state of the "ku" shape was significantly reduced. This greatly improved the workability of mounting on a package. Further, the method for manufacturing an optical waveguide device according to the present invention is mass-producible and industrially useful, as is clear from the contents already described.

[0027]

As described above, according to the present invention, even if the optical waveguide device is connected obliquely to reduce return light due to reflection at the optical coupling portion between the optical waveguide device and the optical fiber, the optical waveguide device can be used. And a method of manufacturing an optical waveguide device in which the optical fiber and the optical fiber are coupled in a substantially linear state without causing any difficulty in mounting on a package.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for manufacturing an optical waveguide device according to the present invention. FIG. 1A is a plan view. FIG. 1B is an explanatory diagram in which a coupling portion between an optical waveguide element and an optical fiber in FIG. 1A is enlarged.

FIG. 2 is a diagram of a section that is cut based on a plurality of patterns of a branching interference type optical waveguide element formed on a substrate.

FIG. 3 is an explanatory view for manufacturing a reflection type optical waveguide element.

FIG. 4 is a diagram showing a configuration of a reflection type optical waveguide element for forming a phase shift optical waveguide on an X-plate substrate.

FIG. 5 is a diagram showing a conventional optical waveguide device. FIG. 5 (a)
FIG. 4 is a diagram in which an optical fiber is connected to a rectangular waveguide element. FIG.
(B) is an explanatory view in which a coupling portion between an optical waveguide element and an optical fiber is enlarged.

[Explanation of symbols]

 1, 2 optical waveguide element 3 reflection type optical waveguide element 4 element coupling end face 11 substrate 12 crystal substrate 13 phase shift optical waveguide 14, 16 optical waveguide 17 reflecting section 18 modulation electrode 20, 21, 22 optical fiber 23 fiber end face

Claims (4)

[Claims] 1. A method of manufacturing an optical waveguide device comprising: an optical waveguide and a phase shift optical waveguide branched from the optical waveguide formed on a substrate to form a branch interference optical waveguide. Forming a finite angle with the normal of the end face of the optical waveguide, and cutting the substrate so that the direction of the phase-shifted optical waveguide does not coincide with the ridge direction of the side surface of the substrate. Manufacturing method. 2. The method according to claim 1, further comprising a step of cutting the substrate so that the phase-shifted optical waveguide intersects perpendicularly with an end face of the phase-shifted optical waveguide. . 3. The substrate according to claim 1, wherein a normal line of the substrate has a crystal axis Z.
2. The method according to claim 1, further comprising a step of cutting the substrate, the direction of the phase shift optical waveguide being made of a lithium niobate crystal that is a direction, the direction being the X direction or the Y direction of the crystal axis. 3. A method for manufacturing an optical waveguide device according to claim 2. 4. The substrate according to claim 1, wherein a normal line of the substrate has a crystal axis X.
A step of cutting the substrate such that a direction of the phase shift optical waveguide formed on the substrate in the direction of the lithium niobate crystal is a Y direction of a crystal axis. 3. A method for manufacturing an optical waveguide device according to claim 1.