JPH05264853A - Waveguide type optical device - Google Patents

Abstract

PURPOSE:To easily provide the optical waveguide type device which can make extremely low-loss optical connection with good reproducibility. CONSTITUTION:A groove 1a constituted of a main path and branch path is formed on a dielectric substrate 1 and an optical waveguide 2 is formed in the groove 1a of the confluent part of the prescribed length of the main path and the branch path as well as the branch path part. An optical fiber 4 has a clad of a prescribed thickness and is imposed by being pressed at two points to the optical waveguide 2 within the groove 1a of the main path part and is fixed by a resin 5. Electrodes 3 for phase modulation are formed on both sides of the optical waveguide 2 in the branch path part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide type optical device used in an optical fiber network or the like, and more particularly to a waveguide type optical device characterized by a connection structure with an optical fiber.

[0002]

2. Description of the Related Art Conventionally, for optical connection between an optical waveguide and an optical fiber, a connection structure by so-called butt coupling in which the waveguide direction of the optical waveguide formed on a substrate and the core line direction of the optical fiber are abutted is generally used. Has been adopted. This type of butt joint is disclosed, for example, in Japanese Patent Laid-Open No. 63-12720.
No. 7 publication.

Further, in order to reduce the optical loss at the connecting portion between the optical waveguide and the optical fiber, a device for making the electromagnetic field field distribution of the optical waveguide close to that of the optical fiber has been made. As such a technique, for example, Japanese Patent Laid-Open No. Sho 61-61
There is one disclosed in Japanese Patent Publication No. 134731. In this publication, the input and output ends of the optical waveguide at the end of the substrate are circularized so as to approximate the shape of the optical fiber, so that the field distribution is made uniform, and the optical loss at the connection is reduced. ing.

[0004]

However, in the conventional butt-coupling described above, if the alignment for aligning the waveguide direction of the optical waveguide and the core line direction of the optical fiber is deviated, the optical loss caused at the connection portion is lost. Will increase. In addition, since the field distribution of the optical waveguide does not match that of the optical fiber, optical mode mismatch occurs and the connection loss increases.

On the other hand, in the above-mentioned conventional coupling in which the field distribution is made closer, the manufacturing process for realizing the connection structure is complicated. Moreover, the controllability of the process is not good, and the reproducibility of the same structure is poor.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and a substrate having a groove formed of a main passage and a branch passage, and a predetermined shape of the main passage and the branch passage. An optical fiber having an optical waveguide formed in the groove of the merging portion of the length and the branch passage portion and a clad of a predetermined thickness placed in contact with the optical waveguide in the groove of the main passage portion. And a waveguide type optical device is formed.

[0007]

The optical waveguide and the optical fiber formed in the main path portion form a directional coupler, and light is transmitted and received between the optical waveguide and the optical fiber. Further, by setting the length of the merging portion of the optical waveguide to an odd multiple of the complete coupling length of the directional coupler, all the light guided in the optical waveguide or the optical fiber is transferred to the optical fiber or the optical waveguide.

The coupling characteristic of this directional coupler is determined by the thickness of the cladding of the optical fiber which is in contact with the merging portion.

[0009]

1 shows the structure of a waveguide type optical device according to an embodiment of the present invention. FIG. 1A is a perspective view and FIG.
Is a sectional view. This optical device is manufactured as follows.

First, patterning for forming a groove having a width of 15 μm is performed on a LiNbO ₃ dielectric substrate 1 having a length of 5 cm. Next, by reactive ion etching (RIE),
A groove 1a having a depth of 15 μm is formed. The groove 1a is composed of a straight main road and a branch road that branches from the main road and returns to the main road again. Next, patterning is performed to form an optical waveguide, and the thickness is 100 nm.
Ti metal is deposited. Then, the unnecessary Ti metal on the pattern is removed by the lift-off method, and the metal other than the optical waveguide region, that is, the portion other than the confluence portion of the main path and the branch path and the branch path portion is removed. After that, 1000 ℃
The heat treatment is performed for 5 hours. By this heat treatment,
The Ti metal in the grooves of the confluence portion and the branch path portion is thermally diffused in the dielectric substrate 1 to form the optical waveguide 2. The optical waveguide 2 is formed at two locations in the main path portion, and these are formed with the lengths A and B from the end portion of the substrate, respectively. Next, patterning for forming the optical function portion is performed again, and Cr / Au metal is formed on this pattern. After that, unnecessary metal is removed by the lift-off method, and the phase modulation electrode 3 is formed. The phase modulation electrode 3 is formed so as to sandwich the optical waveguide 2 formed in the branch path portion.

On the other hand, the optical fiber 4 has a part (about 6c).
m) was soaked in hydrofluoric acid for 33 hours, and the clad thickness was 10
It is melted until it becomes μm. As a result, the diameter of the optical fiber 4 is about 2 to 3 times the core diameter. The melted and thinned fiber portion is placed in the main path of the groove 1a and abutted on two optical waveguides 2 formed in the main path portion. Then, in order to maintain this contact state, the resin 5 is poured into the groove 1a of the main road portion as shown in FIG.
The optical fiber 4 is fixed. A plan view of the device in this state is shown in FIG. It is also possible to partially remove the cladding portion of the optical fiber 4 by mechanical polishing.

In such a waveguide type optical device according to the present embodiment, the evanescent wave is coupled between the optical waveguide 2 and the optical fiber 4 formed at two points of the main path portion, and the directional coupler is formed. Is formed. Therefore, light is transmitted and received between the optical waveguide 2 and the optical fiber 4. The coupling characteristic of this directional coupler is the thickness of the cladding of the optical fiber 4 in contact with the optical waveguide 2, that is, the optical waveguide 2
And the distance between the cores. Since the thickness of the clad is determined with extremely good controllability, the optical connection structure according to the present embodiment has good reproducibility, and devices having the same optical coupling characteristics can be manufactured.

The lengths A and B of the merging portions of the optical waveguide 2
Is set to an odd multiple of the full coupling length of the directional coupler, the light guided in each optical line shifts as follows. That is, as shown in FIG. 3, all of the light guided through the optical fiber 4 from the left side of the drawing moves to the optical waveguide 2,
Furthermore, all the light that has moved to the optical waveguide 2 is converted into the optical fiber 4.
Move to. At this time, the light guided through the optical waveguide 2 is phase-modulated by the electrodes 3 formed with the branched optical waveguide 2 interposed therebetween. Therefore, the light incident on the optical fiber 4 undergoes function modulation while being guided through the optical waveguide 2, and is returned to the optical fiber 4 again.

In the above-described embodiment, the optical fiber 4 and the optical waveguide 2 constitute a directional coupler, and the evanescent wave is coupled to shift the light, resulting in the field distribution mismatch as in the conventional case. No optical coupling loss occurs. Further, the optical fiber 4 and the optical waveguide 2 can be connected without causing reflection loss due to the difference in refractive index. In addition, no alignment is required for connection, and no optical loss due to axis deviation occurs. Therefore, a waveguide type optical device capable of very low loss optical connection can be easily provided with good reproducibility.

Although the optical waveguide 2 is formed by diffusing Ti into the LiNbO ₃ dielectric substrate 1 in the above description of the embodiment, a semiconductor substrate or a glass substrate has a larger refractive index than these substrates. You may make it form the optical waveguide by diffusing the material which it has. Further, in the above-mentioned embodiment, the electrodes 3 sandwiching the optical waveguide 2 are formed so that the optical function section has a phase modulation function, but not limited to the phase modulation, it is possible to have any function according to the type of the optical waveguide. It is possible. For example, by loading a metal on the optical waveguide, the optical function section may have a polarizer function. In each of these cases, the same effect as that of the above-described embodiment can be obtained.

[0016]

As described above, according to the present invention, the optical waveguide and the optical fiber formed in the main path portion form a directional coupler, and light is transmitted and received between the optical waveguide and the optical fiber. Be seen. Further, by setting the length of the merging portion of the optical waveguide to an odd multiple of the complete coupling length of the directional coupler, all the light guided in the optical waveguide or the optical fiber is transferred to the optical fiber or the optical waveguide. Further, the coupling characteristic of this directional coupler is determined by the thickness of the cladding of the optical fiber which is in contact with the merging portion.

Therefore, by setting the clad diameter of the optical fiber and the length of the optical waveguide at the confluent portion to a predetermined value, optical connection with desired optical coupling characteristics can be performed with good reproducibility. Therefore, an optical waveguide type device capable of optical connection with very low loss can be easily provided with good reproducibility without causing the problems of the conventional optical connection structure by butt coupling and the optical connection structure for matching the field distribution. It

[Brief description of drawings]

FIG. 1 is a perspective view and a sectional view for explaining a structure of an optical waveguide device according to an embodiment of the present invention.

FIG. 2 is a plan view showing an optical waveguide device according to an embodiment of the present invention.

FIG. 3 is a diagram showing the principle of light migration in an optical waveguide device according to an embodiment of the present invention.

[Explanation of symbols]

1 ... LiNbO ₃ dielectric substrate, 2 ... Ti diffusion optical waveguide,
3 ... Electrode for phase modulation, 4 ... Optical fiber, 5 ... Resin.

Claims (2)

[Claims] 1. A substrate in which a groove formed of a main path and a branch path is formed, and an optical waveguide formed in the groove of the junction part and a branch path part of a predetermined length of the main path and the branch path. A waveguide type optical device formed by including an optical fiber having a clad having a predetermined thickness, which is placed so as to partially contact the optical waveguide in the groove of the main path portion. 2. The branch path forming the groove branches from the main path and joins the main path again, and an optical function portion is formed in the optical waveguide formed in the branch path portion, and the optical fiber is connected to the main path portion. The waveguide type optical device according to claim 1, wherein the waveguide type optical device is placed in contact with two places of the optical waveguide formed in the groove.