JP3210376B2 - Optical waveguide module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide module for modulating or switching a light wave.

2. Description of the Related Art A conventional method for fixing an optical waveguide element has been performed as shown in FIGS. In this figure, Ti is thermally diffused into a LiNbO ₃ Z plate as a substrate,
An optical waveguide 2 is formed. Further, on the optical waveguide 2,
A buffer layer (SiO ₂ ) is formed, on which an earth electrode and a microwave transmission electrode are formed. In each of the drawings, the optical waveguide has a configuration of a Mach-Zehnder type modulator which is branched once and multiplexed again.

For example, in an optical waveguide device using a Z-cut LiNbO ₃ substrate, a ground electrode and a microwave transmission electrode are respectively provided immediately above the bifurcated optical waveguide, and an electric field applied thereto A phase difference is generated between the respective optical waveguides, and the optical waveguides are multiplexed again, whereby light intensity modulation is performed. Such fixing base electrically connected to the optical waveguide element and the fixing base or element of the grounding electrode is conventionally 1
As shown in FIG. 2, a metal block is fixed to the element by crimping or soldering or silver paste, or as shown in FIG.
The ground electrode of the element and the fixing base were directly fixed using solder, silver paste, or conductive epoxy resin, and electrical connection was made.

When such a method is employed, mechanical stress is reduced when the metal block is fixed to the element or when the element is fixed to the fixing base using solder or silver paste (see FIG. 2). It is inevitable that it will fall on the element. In the Mach-Zehnder type optical modulator in such a state, the stress does not completely affect the two-branched optical waveguide, and the stress is different, so that the original operating point is shifted (see FIG. 7). In addition, there is a drawback that the shift amount varies depending on the stress at the time of fixing the optical waveguide element.

Further, in the conventional element fixing method, expansion, contraction, warping, twisting, and the like of the metal block and the fixing base due to a temperature change are caused.
Work becomes external stress in the optical waveguide device, depending on the temperature change, there is a problem that the operating point will move. In accordance with such behavior optical waveguide device is reduced in diameter, the effect is increased, which is also the result that conflicts with mass production of the optical waveguide device. Thus, according to a fixed method of the conventional optical waveguide device, in particular, in fixation of reduced diameter optical waveguides element not only operating point that by the temperature changes varies the size and initial the fluctuation However, there is a problem that the shift amount varies.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention is directed to the above-mentioned conventional optical waveguide module, which is caused by the temperature change of the optical waveguide module, the stress when the element is fixed, the fixing base,
Relaxes external stresses such as heat expansion and contraction, warpage, and torsion of
Suppress the operating point variation of the optical Namijimoto child, and aims to provide an optical waveguide module which eliminates the initial shift amount variation.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned technical problems, the present invention provides an optical waveguide device having an optical path for guiding a light wave and an electrode for controlling the light wave. An optical waveguide module which is connected with a gap to a fixed base provided with an optical waveguide element housing groove having a dimension larger than an outer dimension, wherein external mechanical and thermal stress applied to the optical waveguide element is reduced. And a stress relief means for connecting the ground electrode of the optical waveguide element and the fixed base via a metal foil, or the entire optical waveguide element is made of a metal foil. The cover is fixed to the fixed base via a conductive material such as conductive epoxy resin or solder, or the ground electrode of the optical waveguide element is connected to the fixed base via wire bonding. To provide an optical waveguide module, characterized in that.

[0008] The stress relieving means is provided by using a metal
Cover with foil, conductive epoxy resin or conductive such as solder
What is fixed to the fixed base via a material is preferable.
is there. Further, it is preferable that the stress relieving means connects the ground electrode of the optical waveguide element to the fixing base through a wire bonding. And the stress relief hand
The step spots the ground electrode of the optical waveguide element and the fixing base with a conductive epoxy resin or a conductive material of solder.
The performing structure is preferable.

[0009]

The LiNbO ₃ optical waveguide device module according to the present invention has a function of relieving the stress when the device is fixed and the external stress such as thermal expansion and contraction, warpage and torsion of the fixing base and the case. Stable characteristics could be given. That is, it is different from the conventional technique in that the optical waveguide element is not completely fixed to the fixing base.

As means for relaxing the stress when the element is fixed and the external stress such as thermal expansion and contraction, warping and torsion of the fixing base and the case, connecting the ground electrode and the fixing base with a metal foil; Alternatively, the waveguide element is covered with a metal foil, and the space between the covered metal foil and the fixing base is filled with a conductive material such as conductive epoxy resin or solder, or between the electrode and the fixing base. Are bonded by wire-bonding to serve as both an elastic inclusion and a conductive material, or a conductive material such as a conductive epoxy resin or solder is provided between the electrode and the fixing base . Dot locally on material
The attached structure can be used. That is, the above-mentioned means open a gap between the fixed base and the waveguide element,
In the meantime, a material with both conductive and elastic properties,
This is done by joining.

Next, the present invention will be described specifically with reference to examples, but the present invention is not limited thereto.

[0012]

Embodiment 1 FIG. 3 is a perspective view of an optical waveguide showing an optical waveguide module according to the present invention. That is, FIG. 3A is a perspective view showing a Mach-Zehnder type optical modulator, and FIG. 3B is an enlarged sectional view showing a section along the line AA ′. As shown in the schematic perspective view of FIG. 3A, this optical waveguide is provided with a metal Ti on a Z-cut LiNbO ₃ substrate 1.
Is formed with a thickness of 800 ° and a width of 7 μm.
The optical waveguide 2 is formed by thermal diffusion.
On top of this, a film of SiO _{2 is formed} to a thickness of 1 μm as a buffer layer 15. Furthermore, as a light control electrode,
The earth electrode 3 and the microwave transmission electrode 4 are formed. Here, the actual size of the element is 0.5 × 0.8 × 50 m
Although m is used, in the figure, the size relationship is shown for convenience of illustration and is different from the actual one.

Here, the optical waveguide element is electrically connected to the fixing base 7 via the metal foil 11 and the element is fixed. Gold foil 11 having a thickness of 20 μm was used as the metal foil. With such a structure, when the optical waveguide element is fixed to the fixing base 7, no mechanical stress is required, and even if the fixing base 7 expands, contracts, and twists due to a temperature change, they are Absorption and relaxation are performed by the gold foil 11, so that external stress does not directly affect the optical waveguide element.

That is, titanium is diffused in the Z-cut lithium niobate substrate 1 to form an optical waveguide 2, and a buffer layer 15 of an SiO ₂ film is further formed thereon as shown in FIG. This is used as a waveguide element, and it is fixed with a gap between it and the fixed base 7. Then, as described above, the electrode of the waveguide element and the external electrode are joined and are configured to be elastically fixed. FIG. 7 is a graph showing a modulation curve when a stress is applied to the optical waveguide element (dotted line) and a modulation curve when a stress is not applied (solid line). That is, when a stress is applied, the original modulation curve (solid line) becomes
It shifts and shifts, so that the original characteristics are not obtained.

FIG. 8 is a graph showing the measured operating point shift amount (shift voltage change: V) of the Mach-Zender type optical modulator module of FIG. It is a thing. It can be seen that the module having the stress relaxation function according to the present invention is more stable than the conventional module structure.
In addition, the mark “曲線” is a curve showing the shift voltage with respect to the temperature change by the module having the structure of the present invention, and the mark “x” is a curve showing the shift voltage with respect to the temperature change by the module having the conventional structure.

[0016]

Embodiment 2 FIGS. 4a and 4b are a perspective view and a sectional view showing the structure of an optical waveguide module according to another embodiment of the present invention. Part b is an enlarged sectional view showing a section taken along line AA ′ of part a. The same optical waveguide element as in the previous embodiment was replaced with a metal foil (thickness 2).
A 0 μm gold foil) 12 was wrapped, and the surrounding area was fixed using a conductive epoxy resin, and at the same time, an electrical connection was formed. In such a structure, the stress at the time of fixing the optical waveguide element and the thermal expansion and contraction of the fixing base, the warp, and the stress due to the twist are caused by the conductive epoxy resin 13 and the gold foil 12.
Because it is absorbed and relaxed, it is similarly stable against temperature changes.

[0017]

Third Embodiment FIGS. 5A and 5B are a perspective view and a sectional view showing the structure of an optical waveguide module according to a further embodiment of the present invention.
Part b is an enlarged sectional view showing a section taken along line AA ′ of part a. This is because the ground electrode 3 of the optical waveguide and the fixed base 7
Are fixedly connected at a plurality of locations by wire bonding 14, as shown in the figure. Thereby, the electrical connection and the fixing of the element were performed. Wire 14 is 2
A gold wire having a diameter of 0 μmΦ was used. With such a structure, the stress when the optical waveguide element is fixed and the thermal expansion and contraction of the fixing base, the warp, and the stress due to the torsion are absorbed and relaxed by the gold wire bonding 14, so that the same applies to the temperature change. It is clear that the characteristics are stable.

[0018]

Fourth Embodiment FIGS. 6A and 6B are a perspective view and a plan view showing the structure of an optical waveguide module according to a further embodiment of the present invention .
This is the ground electrode 3 and the fixing base 7 of the optical waveguide device, using a conductive epoxy resin 16, as shown, local
The element was fixed and the electrical connection was made by performing the appropriate spotting. In this example, only the center of the optical waveguide element (1
In 6), since the element is connected to the fixed base, a structure can be provided in which the thermal expansion / contraction, warpage, and twist of the fixed base do not affect the optical waveguide 2.

FIG. 9 is a graph showing an operating point shift (shift voltage: V) with respect to a temperature change of the optical waveguide module of FIG. It has been clarified that the module having the structure of the present invention can obtain stabilized characteristics. In addition, ○
The mark is a curve showing the shift voltage with respect to the temperature change by the module having the structure of the present invention, and the cross is a curve showing the shift voltage with respect to the temperature change by the module having the conventional structure.

Although the above embodiment has been described using a Mach-Zehnder type optical modulator, it is apparent that the present invention can be similarly applied to an optical switch, a waveguide type polarization compensator and the like. . The substrate material is LiNb
In addition to the O ₃ crystal, it can be used for all materials that can form an optical waveguide, such as PLZT and LiTaO ₃ .

[0021]

As described above, the following remarkable technical effects are obtained by the structure of the optical waveguide module of the present invention. First, by providing a function of alleviating external stress when fixing the optical waveguide element of the present invention to a fixing table, the operating point fluctuation with respect to temperature change is suppressed, and the initial operating point shift amount is reduced. There is an advantage that there is no variation and an original modulation curve can be obtained.

Second, the influence of the stress is larger as the element size is smaller and the diameter is smaller, but according to the present invention,
Regardless of the shape of the optical waveguide element, a module stable against thermal fluctuations could be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure of an example of a conventional optical waveguide module.

FIG. 2 is a perspective view showing the structure of another example of the conventional optical waveguide module.

FIG. 3 is a perspective view and a sectional view showing one embodiment of the optical waveguide module of the present invention.

FIG. 4 is a perspective view and a sectional view showing another embodiment of the optical waveguide module of the present invention.

FIG. 5 is a perspective view and a sectional view showing a further embodiment of the optical waveguide module of the present invention.

FIG. 6 is a perspective view and a plan view showing still another embodiment of the optical waveguide module of the present invention.

FIG. 7 is a graph showing a modulation curve when a stress is applied to the optical waveguide element and a modulation curve when no stress is applied to the optical waveguide element.

8 is a graph showing an operating point shift amount with respect to a temperature change of the optical waveguide module of FIG. 3 of the present invention.

9 is a graph showing an operation point shift amount with respect to a temperature change of the optical waveguide module of FIG. 6 of the present invention.

[Explanation of symbols]

1 LiNbO ₃ substrate 2 waveguide 3 Ground electrodes 4 microwave transmission electrode 5 metal block 6 modulates micro signal feed line 7 fixed base 8 microwave power supply connector 9 silver paste 10 adhesive 11, 12 metal foil 13 electrically conductive epoxy resin 14 Wire bonding 15 Buffer layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-40446 (JP, A) JP-A-62-170913 (JP, A) WO 91/17470 (WO, A1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/035 G02B 6/12

Claims (3)

(57) [Claims] An optical waveguide device having an optical path for guiding an optical wave and an electrode for controlling the optical wave is provided with a gap in a fixed base provided with an optical waveguide element housing groove having a dimension larger than an outer dimension of the optical waveguide element. And an optical waveguide module, wherein the optical waveguide module comprises stress relaxation means for relaxing external mechanical and thermal stress applied to the optical waveguide element, and the stress relaxation means comprises: An optical waveguide module, wherein the connection between the ground electrode and the fixed base is made via a metal foil. 2. An optical waveguide device having an optical path for guiding an optical wave and an electrode for controlling the optical wave is provided with a gap in a fixed base provided with an optical waveguide element housing groove having a dimension larger than an outer dimension of the optical waveguide element. And an optical waveguide module, wherein the optical waveguide module comprises stress relaxation means for relaxing external mechanical and thermal stress applied to the optical waveguide element, and the stress relaxation means comprises: An optical waveguide module, wherein the whole is covered with a metal foil and fixed to the fixing table via a conductive material such as a conductive epoxy resin or solder. 3. An optical waveguide device having an optical path for guiding an optical wave and an electrode for controlling the optical wave is provided with a gap in a fixing table provided with an optical waveguide element housing groove having a dimension larger than an outer dimension of the optical waveguide element. And an optical waveguide module, wherein the optical waveguide module comprises stress relaxation means for relaxing external mechanical and thermal stress applied to the optical waveguide element, and the stress relaxation means comprises: An optical waveguide module, wherein the connection between the ground electrode and the fixed base is performed via wire bonding.