JPS61166504A - Optical circuit device - Google Patents

Abstract

PURPOSE:To obtain an optical circuit device whose efficiency is high and optical coupling efficiency is less varied with time and assembling is easy, by forming a core in one end of an optical transmission line into a small-angled taper shape and approximating the section of the core terminal surface in this taper core part to the terminal surface of an optical waveguide and providing a supporting plate which holds the taper core part. CONSTITUTION:The device consists of, at least, one optical waveguide 12 provided on a substrate 1 and one optical transmission line 14 having a core 13 which transmits optical waves coupled optically to the optical waveguide 12. A taper core part 13a where the core 13 in one end of the optical transmission line 14 is tapered is provided, and the section of a core terminal surface 13b of the taper core part 13a is approximated to a terminal surface 12a of the optical waveguide, and a supporting plate 15 is provided which has a common surface 15a with the core terminal surface 13b and holds the taper core part 13a. Optical axes of the waveguide 12 and the optical transmission line 14 coincide with each other, and they are constituted on the same plane approximately, and therefore, assembling is made easy, and the optical coupling loss is good 3dB.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical circuit device related to optical communication and optical control. In particular, it relates to thin film optical waveguide type optical circuit devices.

Conventional technology This kind of thin-film optical waveguide type optical circuit denomination (chair)
As shown in FIG. 3, an optical waveguide 32 provided on a substrate 31 and an optical transmission line 34 including a core 33 for transmitting light waves were optically coupled. The optical coupling method is usually the optical waveguide 31 and core 33 shown in FIG. 3 from the viewpoint of reliability and miniaturization.
An end-face bonding method is used in which the mirror-finished end faces of
．． 5゜15), Coronasha, P, 250).

In this type of configuration, the cross-sectional areas of the optical waveguide 32 and the core 33 are usually different from, for example, 18 m×10 μmW to 10 μmφ, so that good coupling efficiency cannot be obtained. From the perspective of improvement, the configuration of optical coupling between semiconductor devices and single-mode optical transmission lines (Haruo Sakaro, Norio Seki, Shu Yamamoto, IEICE Photonics and Quantum Electronics Study Group Material 0QE80
-123 (1980) P, 57) may be applied to thin film optical waveguides. The configuration is shown in FIG. In the figure, 31.32, 33.34 are the same as in FIG. 3.

The structure is such that the optical end of the optical fiber is polished into a taper (wedge) shape of about 900, and then the tip of the core 33 is heated and melted by arc discharge and processed into a tapered semi-cylindrical lens 41 to increase the coupling efficiency. There is. For example, 0.6μm x2~3
μmw semiconductor laser, 10 μmψ step type single-
Coupling losses of 2.9 to 3.3 dB have been reported for mode optical transmission lines.

Problems to be Solved by the Invention However, in this type of configuration, it is difficult to align the optical axes of the optical waveguide 32, the tapered semi-cylindrical lens 41, and the core 33, so there is a problem that the optical coupling efficiency changes over time. there were. Therefore, when an optical circuit is constructed using the optical waveguide 32, there is a problem in that the characteristics of the optical circuit change over time. This is due to the following reasons.

In order to process the core 33 into a tapered shape, it is necessary to align the center axis of the core 33 with the line of intersection of the two taper surfaces 42, and to make the angles formed by the two taper surfaces 42 equal to 2. The goal is to match the branch line with the central axis of the core. In addition, the tapered semi-cylindrical lens at the tip of the core is manufactured using electrical discharge melting with high precision. result,
The optical axis that coincides with the central axis of the core 33 and the optical axis of the tapered cylindrical lens coincide, and the beam diameter is narrowed down to match the cross section of the optical waveguide at the focal plane, and the optical coupling efficiency between the core 33 and the optical waveguide 32 is logically determined. It is possible to approach the value.

Machining of this tapered cylindrical lens requires a processing technique with submicron precision, and there are many technologically unestablished aspects of electric discharge melting machining (for example, machining of a lens with a lens radius of 4 to T μm x 8 to 10 μmW).

Therefore, it is difficult to match the optical axes of the core 33 and the tapered semi-cylindrical lens and match the cross sections of light waves at the focal plane, so the optical coupling efficiency due to slight relative positional deviation (due to temperature, etc.) of the optical coupling surface This results in the occurrence of instability. In addition, due to the mismatch of the optical axes, the optical waveguide 32 and the core 33 cannot be optically coupled near the same plane, and the optical coupling efficiency becomes maximum at a predetermined angle, making assembly difficult. Furthermore, in multimode optical waveguides, the maximum excitation efficiency of the fundamental mode and the maximum optical coupling efficiency do not match, making it impossible to realize an efficient device configuration. This was difficult due to the relative positional deviation of the surfaces.

Therefore, the present invention provides a structure that allows the optical axes of the optical waveguide and the optical transmission line to coincide with each other to provide high efficiency, less secular variation in optical coupling efficiency, and easy assembly.

Means for solving the problems and the technical means of the present invention for solving the problems described above include a tapered core portion in which the core thickness at one end of the optical transmission line is tapered at a small angle; A support plate is provided which has a cross section of the core end face approximated to the optical waveguide end face, has a common surface with the core end face, and holds the tapered core portion.

For production The effect of this technical means is as follows.

In other words, the thickness of the core at one end of the optical transmission line is tapered to a small angle, and by holding it with a support plate, the surface of the tapered core is protected and stabilized, so that the transmitted light in the optical transmission line remains in its fundamental mode. By aligning the optical transmission line and the optical waveguide, the electromagnetic field distribution of the transmitted light can be made to substantially match the electromagnetic field distribution of the fundamental mode guided light of the optical waveguide. The optical coupling obtained as a result is different from the lens action shown in FIG. 4 and uses the butt end face coupling method shown in FIG. 3, so that optical coupling with high efficiency and less fluctuation over time can be obtained.

Since the use of the support plate has the effect of eliminating the natural vibration of the taper core, stable coupling efficiency can also be obtained.

In the case of a multimode optical waveguide, the fundamental mode is transmitted to the core terminal surface of the optical transmission line, and since optical coupling is achieved by matching the optical axes, it is basically difficult for anything other than the fundamental mode to be excited, and therefore the optical guide The mode dispersion state of the wave path is stable and high optical coupling efficiency can be obtained.

As a result of the above, high efficiency, little change over time, and easy assembly are achieved.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

In FIG. 1, b indicates the main part structure, and a shows the main part structure of the AA/cross section of b.

In the same figure, it consists of at least one optical waveguide 12 provided on a substrate 11 and at least one optical transmission line 14 having a core 13 for transmitting a light wave that is optically coupled to the optical waveguide 12, and one end of the optical transmission line 14. The tapered core part 13a has a tapered core part 13a having a tapered thickness.
The cross section of the core termination surface 13b of 3a is the optical waveguide termination surface 12a.
A support plate 16 is provided which has a common surface 15a with the core end surface 13b and holds the tapered core portion 13a.

Next, the operation of the configuration of this embodiment will be specifically explained. A 0.8 μm thick PLZT thin film (refractive index 26) was formed on a sapphire substrate 11 (refractive index 1.77) by sputter deposition. Next, an optical waveguide 12 was formed to a width of 10 .mu.m by evaporation and ion beam etching, and then the end surface was polished to produce a mirror end surface 12a. On the other hand, the optical transmission line 14 has an outer diameter of 126 μmφ and a core diameter of 10 μm.
Using a quartz single mode fiber with a diameter of ψ, polish the Taber surface with the angle of 100 to obtain a thickness of lff.
An 11m long quartz substrate was glued with epoxy resin adhesive (refractive index 1.6).
) to hold the tapered core portion 13a. Next, the end of the core was mirror-polished to produce a core end surface 13b of 1 μmD×10 μmW. It was confirmed that the far-field image of the transmitted light was a single mode. The refractive index of epoxy resin is 1.
6 and the refractive index of the quartz fiber is 1.47, but the film thickness of the epoxy resin is 0.2 μm (SEM observation), which is thinner than the thickness at the core end surface 13b, and the thickness of the core 13 is set at an angle of 10 Since it has a tapered configuration of .degree., it is considered that the fundamental mode is transmitted to the core end face 13b.

The fabricated optical waveguide termination surface 12 & was brought into contact with the core termination surface 13b to perform optical coupling, thereby producing an optical circuit device.

In the manufactured optical circuit device, since the transmission light in the optical transmission line 14 is transmitted in the fundamental mode, the optical transmission line 14
By matching the optical waveguide 12 with the optical waveguide 12, the electromagnetic field distribution of the transmitted light and the base of the optical waveguide are considered to almost match the electromagnetic field distribution of this mode. The optical coupling loss was good at 3 dB. Optical waveguide 12 and optical transmission line 1
No. 4 had the same optical axis and was constructed almost on the same plane, making it easy to assemble.

In particular, the optical axes of the optical waveguide 12 and the optical transmission line 14 are aligned, and the natural vibration of the tapered core part is eliminated by using a support plate, so the optical coupling loss is extremely low at 3 dB even after one week of aging. There was little variation. Multimode P
Even when a Y branch is configured with an LZT thin film optical waveguide (4 modes), it has been confirmed that the branch ratio is stable 1:1, and therefore, the fundamental mode is mainly excited and the mode dispersion state is stable. Conceivable.

In FIG. 1, 11 is a substrate, 12 is an optical waveguide, and 13 is a substrate.
14 is a core, 14 is an optical transmission line, and 16 is a support plate.

Next, other embodiments of the present invention will be described.

FIG. 2 shows another embodiment, and in this embodiment, the main part configuration diagram on the optical transmission line side is shown. In the same figure, 13,
14.15 are the same as in FIG.

In the figure, four optical transmission lines are arranged in parallel. For example, the optical transmission line 14 has an outer diameter of 125 μmφ.

A quartz single mode fiber with a core diameter of 10 μmφ was used, optical transmission lines 14 were arranged in parallel at intervals of 126 μm, and the processing shown in the first example was performed. The optical waveguide 12 has a width of 10
Ti-diffused LiNbO3 optical waveguides with a film thickness of 1 μm were fabricated at intervals of 126 μm, and the end faces were polished. The two were brought together and optically coupled to fabricate an optical circuit device.

The optical coupling loss of the fabricated optical circuit device was 3.6±o,t
It was well within the s dB range. Also, no change over time was observed. On the other hand, in the configuration shown in the second conventional example, the optical axes do not match at each optical coupling point during processing, and it is difficult to suppress variations in coupling loss. Therefore, the configuration of the present invention is effective for optical coupling between a plurality of optical transmission lines and optical waveguides.

Although an epoxy resin adhesive was used in this example, low-melting glass such as Corning 8363 (softening point 380
Adhesion of the support plate and the taper core part is included in the means of the present invention, such as depositing a thin film (e.g., 0.2 μm) with a refractive index of 1.9 on the support plate and bonding the tapered core part with vacuum heat. It is not limited to epoxy resin adhesives.

Next, other embodiments of the present invention will be described.

FIG. 6 shows the main part configuration of another embodiment, with 11°12.1
3, 14, and 15 are the same as in FIG.

In this embodiment, the thickness of the end of the tapered core portion 13b is set to 0.
4 μm, and a metal thin film 51 such as Aq O,
After evaporating 2 μm, a support plate was bonded with epoxy resin. The refractive index of the gradient is 0.2 (wavelength: 1.3 μm), and the transmitted light is well confined and transmitted, so the wavelength is 0.4 μm.
I was able to narrow it down to.

A circuit device was fabricated by optically coupling with a 0.4 μm×10 μmW PLZT thin film optical waveguide.

The coupling loss of the manufactured optical circuit device was 4 dB, and the characteristics were comparable to those with a film thickness of 1 μm. This example has been shown to be effective in cases where the first and second examples cannot be applied due to the thin film thickness. That is, 1st. In the second embodiment, since the refractive index of the adhesive layer is higher than that of the core, when the tapered core portion is made thinner, a radiation mode occurs, increasing coupling loss. Of course, the stability of the optical coupling efficiency and the stability of the mode dispersion state are the first. The same effects as in the second example were obtained.

Effects of the Invention The present invention has a tapered core portion in which the thickness of the core at one end of the optical transmission line is tapered at a small angle, and the cross section of the core termination surface of the tapered core portion is approximated to the optical waveguide termination surface. Since it is provided with a support plate that has a common surface with the end surface and holds the tapered core part, it has high efficiency, little change in optical coupling efficiency over time, and is easy to assemble.Moreover, it also has the following effects. .

That is, since the present invention uses optical coupling by butting, it has the effect that optical coupling between multiple optical transmission lines and optical waveguides can be manufactured with high efficiency and less variation.
It is also possible to achieve miniaturization and integration of optical circuit devices.

[Brief explanation of the drawing]

FIG. 1(a), Φ) is a sectional view and a configuration diagram of a main part of an optical circuit device according to an embodiment of the present invention, and FIG. 2 is a configuration diagram of a main part of the same device according to another embodiment of the present invention. , FIG. 3 is a diagram showing the main part of the same device according to the conventional example, FIG. 4 is a diagram showing the main part of another conventional example, and FIG. 5 is a diagram showing the main part of the same device according to the third embodiment of the present invention. It is. 11... Substrate, 12... Optical waveguide, 1
3...Core, 14...Optical transmission line, 16
... Support plate, 61 ... Metal thin film. Name of agent: Patent attorney Toshio Nakao and 1 other person13
・-・Core g、・・光い亚线 15...Friend poem treatment': pIz diagram f3 Figure 3 34 Figure 4

Claims (1)

[Claims] It consists of at least one optical waveguide provided on a substrate and at least one optical transmission line having a core for transmitting a light wave optically coupled to the optical waveguide, and the thickness of the core at one end of the optical transmission line is tapered. a support plate for holding the tapered core portion, the cross section of the core end surface of the tapered core portion being approximated to the optical waveguide end surface, and having a common surface with the core end surface; An optical circuit device featuring: