JPH0194305A - Optical circuit device - Google Patents

Abstract

PURPOSE:To realize efficient optical coupling by providing a hole, which piercing a substrate, between an optical waveguide and a groove. CONSTITUTION:A hole 6 piercing a substrate 1 is provided between an optical waveguide 2 and an optical fiber supporting groove 3 by a simple and high- precision fine working method. Si having crystal face azimuth (100) is used as the substrate 1 and the optical waveguide 2 is a quartz single mode optical waveguide. The material of the core of the optical waveguide 2 is SiO2+TiO2, and the material of the clad around the core is SiO2+P2O5+B2O3, and a quartz single mode optical fiber is used as an optical fiber 4. Since a V groove 3 is formed by crystal face (111), the angle of the V groove 3 is crystal-graphically determined; and the width of the V groove 3 is so designated that the optical waveguide 2 and the optical axis of the optical fiber 4 coincide with each other at the time of arranging the optical fiber 4 in the V groove 3, and the crystal face azimuth of the side face of a hole 5 is (110) and the width of its sectional shape is made equal to that of the V groove 3. Thus, efficient optical coupling is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to an optical circuit device suitable for highly efficient optical coupling between an optical waveguide and an optical element.

[Conventional technology]

Conventionally, the following techniques have been known for optical coupling between a guide waveguide and an optical fiber. A method of preparing an optical fiber and supporting the optical fiber with this groove (Japanese Patent Application Laid-Open No. 60-95410, etc.).

(2) A method of using a Si substrate as a support, forming a recess and a V-groove by anisotropic chemical etching, and mounting a guiding waveguide substrate in the recess and an optical fiber in the groove. 119314 etc.).

(3) A method in which a groove with a U-shaped cross section is formed by reactive dry etching on an optical waveguide substrate, and an optical fiber is disposed in this groove (Japanese Patent Laid-Open No. 146107/1984, etc.).

[Problem that the invention seeks to solve]

The prior art (1) above requires complicated optical axis adjustment in order to optically couple the optical waveguide and the optical fiber. Also, Si
(2) As the optical axis shifts due to aging of the adhesive that fixes the groove, there was a problem with the stability of optical coupling efficiency.

Similarly to (1), the conventional technology (2) also uses an optical waveguide substrate and a V
Since the groove is not integrated with the groove, complicated optical axis adjustment is required. In particular, since the position of the guide waveguide substrate changes depending on the thickness of the adhesive that fixes the recess and the optical waveguide substrate, a difficult technique is required to control the thickness of the adhesive.

In the prior art (3), since the groove is formed on the optical waveguide substrate, there is no need to particularly adjust the optical axis, and optical coupling can be achieved simply by disposing the optical fiber in the groove. However, since the cross-sectional shape of the groove is U-shaped, an error occurs between the width of the groove and the outer diameter of the optical fiber, and this difference appears as a variation in optical coupling efficiency. Furthermore, dry etching requires expensive vacuum equipment, which is a heavy economic burden.

Since the processing speed is several nanometers/second, it takes several tens of hours to process a groove of about 100 μm, and during this time, processing conditions such as gas pressure, gas flow rate, and electrode voltage must be controlled, making it difficult to mass-produce. There is a problem with this.

As described above, each of the conventional techniques has its own problems. In order to solve this problem, it is essential to (1) form the optical waveguide and the optical fiber support groove on the same substrate, and (2) perform highly accurate groove processing using inexpensive equipment.

If the above two conditions (■) and (2) are met by i2, the third
A configuration like the one shown in the figure is possible.

In FIG. 4, an optical waveguide 20 is placed on a substrate 201 made of Si.
2 and a V-groove 203 that supports the optical fiber 204 is formed. ■Anisotropic chemical etching, which allows easy, high-precision micromachining, is used to process the grooves. The crystal plane orientation of the substrate 201 is (100), and the groove 203 is formed by the (111) plane. At this time, in anisotropic chemical etching, V groove 2
The terminal of 03 also consists of crystal plane (111), and 205 (I
Since an angle 0 = 54.7°) is formed, this 205 becomes an obstacle and the leading waveguide 202 and the optical fiber 20
I can't get 4 close. When a commercially available optical fiber 204 with an outer diameter of 125 μm is used, the distance Q between the leading waveguide 202 and the optical fiber 204 is as large as 44 μm.

In this case, the coupling efficiency between the optical waveguide 202 and the optical fiber 204 due to end face direct coupling becomes extremely low. Therefore, even though the configuration shown in FIG. 3 satisfies the conditions (1) and (2), there is a problem in terms of coupling efficiency.

An object of the present invention is to provide an optical circuit device that enables highly efficient optical coupling by direct coupling between an optical waveguide and an optical fiber at their end faces.

[Means for solving problems]

The above object is achieved by providing a hole penetrating the substrate between the guide waveguide and the optical fiber support groove using a simple and highly accurate microfabrication method.

[Effect]

Because the above-mentioned hole removes the slope formed at the end of the groove, it is possible to bring the optical waveguide and optical fiber into close contact with each other.
Highly efficient optical coupling is achieved through direct end-face coupling.

〔Example〕

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

FIGS. 1 and 2 show a first embodiment of the present invention, and are diagrams for explaining the basic configuration. V-grooves 3 and 66 for supporting the optical waveguide 2 and the optical fiber 4 are formed in the substrate 1.

Substrate 1 is S with a crystal plane orientation (100) and a thickness of about 200 μm.
i was used. The optical waveguide 2 is a silica-based single mode leading waveguide. CV D (Chemical Vapor De
A quartz glass film was deposited on the substrate 1 by a positioning method or a flame direct deposition method, and patterned by photolithography and reactive ion etching to obtain a line-shaped three-dimensional optical waveguide. The core of the optical waveguide 2 has a cross-sectional shape of 8 μm x 8 μm and a material of 5 iOz+'
It's l'i0z. The thickness of the cladding around the core is 5μm
, the material is 5iOz1P20B+BzOa. The propagation loss of the optical waveguide 2 was 0.1 dB/co+ or less. The optical fiber 4 has an outer diameter of 125 μm and a core 5 diameter of 9.
A μm quartz-based jli-mode optical fiber was used.

(2) Groove 3 is formed by the crystal plane (111), so the angle of V-groove 3 is crystallographically determined to be 70.5'. v i4
The width of a was designed so that when the optical fiber 4 was placed in the groove 3, the optical axes of the leading waveguide 2 and the optical fiber 4 were aligned. From the dimensions of the optical waveguide 2 and the optical fiber 4 and the angle of the V-groove 3, the width of the groove 3 is calculated to be 140.4 by simple algebraic calculation.
Find it as μm.By the way, the depth of V groove 3 is 99.3
It is μm.

The crystal plane orientation of the side surface of the hole 5 is (110).

The cross-sectional shape of the hole 5 is the same as the width of the V-groove 3 (140.4 μm x
It was set to 140.4 um.

(2) The process of forming the grooves 3 and holes 5 will be explained with reference to FIG. The figure schematically shows how the V-groove 3 and the hole 5 are formed. The left side of the figure is a sectional view, and the right side is a plan view. Since the optical waveguide 2 can be created independently of the main formation process, the leading waveguide 2 is not drawn in the figure.

As shown in FIG. 3(a), first, 5iOz films 11 and 12 are formed on the substrate 1 by thermal oxidation of Si or CVD. 5iOz film 11 on the top surface of the substrate 1 and 5iOz film 11 on the bottom surface
Patterning of the Z film 12 was performed by photolithography using a double-sided mask aligner. Film thickness is 2μm
It is.

Using these SiOx films 11 and 12 as an etching mask,
Anisotropic chemical etching is performed in a 40 wt % KOH aqueous solution at 40° C. (FIG. 3(b)). Since the etching rate of the crystal plane (111) is /42 of the (100) plane,
(100) (surfaces 14° and 16) are mainly etched,
(111) face (13.15.17) remains.

As etching progresses from both sides of the substrate 1, holes 1
8 penetrates (Fig. 3(C)). When further etching is performed, etching of the (110) plane (plane 19) perpendicular to the substrate 1 starts at the same time as the etching of the (100) plane (FIG. 3(d)). The etching rate of the (110) plane is (1
11) It is about 180 times faster than the surface and is extremely fast.

Finally, the V-groove 3 and the hole 5 are formed as shown in FIG. 3(8), and the optical circuit device shown in the first embodiment is completed. If the etching is done a little too much (Figure 3 (f))
However, there is no problem in achieving the purpose of the present invention.

According to the first embodiment, simply by disposing the optical fiber 4 in the groove 3 and bringing the end surfaces of the optical waveguide 2 and the optical fiber 4 into close contact with each other, the cores of the optical waveguide 2 and the optical fiber 4 can be connected to each other without adjustment. This has the effect of making it possible to perform direct optical coupling at the end face with high efficiency. The optical coupling efficiency showed a high value of 91%, almost matching the theoretically predicted value. Furthermore, the leading waveguide 2 and the optical fiber 4
When the leading waveguide 2 and the optical fiber 4 are glass fused and spliced by applying glass fine particles to the close contact area and irradiating with a carbon dioxide laser, a coupling efficiency of 98% is obtained. To confirm the stability of the binding efficiency, a temperature cycle test (-45° to +80°C, 1 cycle 30 minutes, 1000
2 times), but no observable deterioration was observed and it showed very high stability.

Furthermore, since the first embodiment utilizes anisotropic chemical etching, (1) the grooves 3 and the holes 5 can be processed at the same time, which has the effect of improving productivity. It is impossible to perform V-shaped diagonal processing and vertical processing at the same time using general dry etching processing.

The equipment used for anisotropic chemical etching only needs to be a constant temperature bath containing a KOH aqueous solution, and since it is inexpensive, it does not impose an economic burden.

Incidentally, the requirement of the present invention is that the holes are formed in the optical waveguide substrate, and the types and materials of the optical waveguide, optical fiber, and substrate described in the first embodiment, the process for forming grooves and holes, etc. It is not limited.

For example, if the material of the optical waveguide or substrate is LiNbO3゜ZnO
, '5isNa, etc., GaAs, InP
Of course, it does not matter if it is a semiconductor such as. The dimensions of the optical waveguide can be changed in design. The effects of the present invention can be exerted even when the optical fiber is a multimode fiber or a plastic fiber. The shape of the groove may be U-shaped or trapezoidal. The size and shape of the hole may also be changed according to convenience. Regarding the process of forming grooves and holes, steps may be omitted or modified in relation to the optical waveguide substrate, and other anisotropic etching methods may be used, such as etching with a bromine-methanol mixture of InP or a hydrochloric acid-phosphoric acid mixture. is also possible. Furthermore, it goes without saying that the present invention can be practiced even when optical waveguides and optical fibers are arranged in an array.

In addition to optical fibers, optical devices that perform end-face direct coupling to optical waveguides include laser diodes, photodiodes,
Optical waveguides and the like can be considered, but the present invention is also applicable to these optical elements.

The present invention is applicable not only to waveguide-type passive optical devices such as optical branching/combining, wavelength demultiplexing/combining, etc., but also to optical switches, pre-emption processing, etc. using a substrate made of heteroepitaxial growth of GaAs on Si. It can also be used for waveguide-type functional optical devices. In addition, an electronic circuit is created on the board and 0RIC (
Opto Electronic Integrated
C1rcuits).

〔Effect of the invention〕

According to the present invention, stable and highly efficient optical coupling can be achieved without any adjustment simply by arranging the optical fiber in the support groove, which has the effect of improving the mass productivity and reliability of the optical coupling device.

[Brief explanation of the drawing]

Fig. 1 is a perspective view illustrating a previous circuit device according to an embodiment of the present invention, Fig. 2 is a side view of Fig. 1, and Fig. 3 is a formation of grooves and holes in the optical circuit device of Fig. 1. An explanatory diagram showing the process, FIG. 4 is a side view showing a conventional optical circuit device. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Guide waveguide, 3...Groove, 4...
・Optical fiber￥3 Figure

Claims (1)

[Claims] 1. In an optical circuit device in which an optical waveguide and a groove for guiding an optical fiber are formed on the same substrate, a hole passing through the substrate is provided between the optical waveguide and the groove. An optical circuit device featuring: 2. The optical circuit device according to claim 1, wherein the substrate is made of silicon. 3. The optical circuit device according to claim 1, wherein the grooves and holes are processed by anisotropic etching.