JPH10123472A - Packaging construction of waveguide type optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the new technique in which the generated frequency of a loss dip is shifted to a higher frequency side in a waveguide type optical device. SOLUTION: The packaging construction is provided having a waveguide type optical device 1 and a casing 9 which stores the device 1. The device 1 is provided with a substrate 2 on which an optical waveguide 3 is formed, a signal electrode 5 which is formed on the main surface of the substrate 2 and a pair of ground electrodes 4 and 6 which are formed to sandwich the electrode 5. The microwave signal voltage applied to the electrode 5 and the optical waves propagated in the waveguide 3 are mutually operated on. A high frequency connector 40 of the casing 9 side and the electrode 5 are connected. Moreover, an opposing surface 9a which is opposing to the substrate 2 of the casing 9 and the electrodes 4 and 6 are connected by electrically conductive member layers 20 and 21 which are positioned between the surface 9a and an end face 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide on a substrate made of a material having an electro-optical effect such as lithium niobate.
The present invention relates to a mounting structure of a waveguide type optical device on which a ground electrode and a signal electrode are formed, and more particularly to a mounting structure of a waveguide type optical device suitable for high-speed long distance.

[0002]

2. Description of the Related Art A modulator for forming a ground electrode, a signal electrode and an optical waveguide on a substrate made of a material having an electro-optical effect, applying a microwave signal voltage to the signal electrode, and modulating a light wave propagating through the optical waveguide. It has been known. FIG. 14 is a plan view showing an example of such a modulator. The waveguide type optical device 16 is a so-called Mach-Zehnder type modulator. The substrate 2 is made of an electro-optic single crystal such as lithium niobate. On the main surface of the substrate 2, for example, a titanium diffused optical waveguide 3 is formed. The optical waveguide 3 extends between the input-side end face 2c and the output-side end face 2d, and branches off near the center of the substrate 2 into optical waveguides 3a and 3b. A ground electrode 4 having a specific shape is provided on the main surface of the substrate 2.
A, 6A and a signal electrode 5A are provided. 7, 8
Is an insulating region that insulates each of the ground electrodes 4A and 6A from the ground electrode 5A. In this modulator, a ground electrode and a signal electrode having a so-called coplanar wave guide (CPW) form are used for the purpose of further improving the operation speed.

[0003] Such a waveguide type optical device needs to be mechanically fixed to an appropriate housing and electrically connected. As described above, several methods for mounting the waveguide type optical device on the housing are known (see Japanese Patent Application Laid-Open Nos. 5-142505 and 7-64030). However, for example, the mounting structure shown in FIG. 15 is general. Reference numeral 9 denotes a wall of the housing, and one end surface 2 of the substrate 2 is provided on the facing surface 9a of the housing 9.
a are opposed to each other at a predetermined interval. 2b is the other end face. The distance between the facing surface 9a and the end surface 2a is usually 0.05 mm to 0.1 mm. The surface of the wall of the housing 9 on the side of the facing surface 9a is preferably plated with gold, and is configured to function as a ground. The end surface 2a side of the outer ground electrode 4A is opposed to the opposing surface 9 by the metal foil 17.
a and the inner ground electrode 6
The end on the side of the end face 2a of A is opposed to the opposite face 9a by the metal foil 19.
Are electrically connected to

FIG. 16 is an enlarged view of a conventionally known connection structure of a high-frequency connector. In the mounting structure shown in FIGS. 15 and 16, the center conductor 40 of the high-frequency connector is held by a cylindrical holding portion 30, and the holding portion 30 is almost buried inside the housing 9. Holder 30
Is provided with an external ground, which is a shield conductor, on the outer peripheral surface thereof. A flat-plate-shaped substrate connecting conductor 11 is fixed to the distal end portion of the center conductor 40 by a holder 18, and the substrate connecting conductor 11 is connected to the end of the signal electrode 5A on the end surface 2a side.

When the modulator 16 is operated, a microwave signal voltage from a signal generator (not shown) is applied to the signal electrode 5A via the high-frequency connector 40 and terminated by a terminating resistor (not shown). Specifically, a signal from the signal generator is taken out by a coaxial cable and applied to the signal electrode 5A via the board connecting conductor 11. This microwave signal voltage allows the signal electrode 5A and the ground electrode 4
An electric field is generated between A and 6A. Since the substrate 2 has an electro-optic effect, a difference in refractive index occurs between the optical waveguides 3a and 3b due to the electric field between the signal electrode and the ground electrode. As a result, the optical waveguides 3a and 3b And a phase shift occurs in the phases of the light waves propagating through. This phase difference is 2mπ
When it becomes radian (m is an integer), the waveguide mode is excited at the multiplexing portion of the optical waveguide 3, and the optical output is turned on. On the other hand, when the phase difference between the light waves propagating through the optical waveguides 3a and 3b becomes (2mπ-1) radians, a higher-order mode is excited at the multiplexing portion of the optical waveguide 3, and the optical output is turned off. "State.

In such a waveguide type optical device,
The coplanar wave guide type signal electrode 5A and the ground electrodes 4A and 6A are configured as modulation electrodes for supplying a microwave signal voltage for modulation. Therefore, assuming that there is no speed difference between the microwave signal voltage for modulation propagating through these conductors 4A, 5A, and 6A and the light propagating in the optical waveguide 3, the optical modulation band is limited. There should not be. However, in reality, there is a propagation loss inside each electrode, and there is a speed difference between the microwave signal voltage and the light, so that the modulation band is limited.

[0007]

In such a waveguide type optical device, at a specific frequency, there is a problem that a transmission characteristic called "loss dip" is deteriorated. For example, as described later, an impedance of 5
0 Ω, the substrate 2 is formed of lithium niobate, the thickness of the substrate is 0.5 mm, and the length of the substrate is 60 mm.
mm and a width of 0.8 mm (S
_{2 1)} are shown in Figure 17. In this case, the frequency is about 27 GH
It can be seen that a large loss dip occurs in the transmission characteristics near z. The usable frequency band of such a modulator is limited to the frequency at which this loss dip occurs.

In such a conventional waveguide type optical device, in order to further expand the modulation band to a higher frequency side, it is necessary to make the substrate thinner, increase the resonance frequency, and increase the frequency at which dip occurs. For example, JP-A-6-30
As described in 8437 JP, a thickness of 0.5mm of the substrate, the transmission characteristic (S _{2 1)} is about 20GH
In the case of z, if the thickness of the substrate is 0.15 mm,
Transmission characteristic (S _{2 1)} is about 60GHz or more. However, the size of the optical modulator is 40 to 60 in the light propagation direction.
Since the length is required to be about mm, for example, when the thickness of the substrate is reduced to 0.15 mm, the substrate is very easily broken, and handling becomes difficult.

Further, according to Japanese Patent Application Laid-Open No. 7-98442, since the impedance of the high-frequency connector is different from the impedance of the signal electrode, the modulation band is deteriorated due to impedance mismatch. For this reason, it has been proposed that an impedance matching circuit for matching the impedance of the high-frequency connector and the impedance of the signal electrode be arranged between them. However, even with this method, the modulation band cannot always be sufficiently expanded to the high frequency side, and extra circuit components are required.

An object of the present invention is to provide a substrate on which an optical waveguide is formed, a signal electrode formed on the main surface of the substrate, and a pair of ground electrodes formed so as to sandwich the signal electrode. In the waveguide type optical device configured so that the microwave signal voltage applied to the signal electrode and the light wave propagating in the optical waveguide can interact with each other, the generation frequency of the loss dip is set to the high frequency side. It is to provide a new technology to make the transition to.

[0011]

According to the present invention, there is provided a mounting structure comprising a waveguide type optical device and a housing for accommodating the waveguide type optical device, wherein the waveguide type optical device has an optical waveguide. A signal electrode formed on a main surface of the substrate; and a pair of ground electrodes formed to sandwich the signal electrode. Wave signal voltage and a light wave propagating in the optical waveguide are configured to be able to interact,
The high-frequency connector on the housing side and the signal electrode are connected, and the opposing surface opposing the substrate of the housing and each ground electrode are connected by a conductive material layer interposed between the opposing surface and the end surface of the substrate. The present invention relates to a mounting structure of a waveguide type optical device, which is connected to each other.

The present invention is also the above mounting structure, wherein the high-frequency connector on the housing side and the signal electrode are connected, and the opposing surface of the housing facing the substrate and each of the ground electrodes are electrically conductive. At the connection portion between each ground electrode and each conductor, that the edge of each ground electrode on the signal electrode side and the edge of each conductor are substantially continuous without any level difference. The present invention relates to a mounting structure of a waveguide type optical device.

The present invention is also the above mounting structure, wherein the high-frequency connector on the housing side and the signal electrode are connected, and the opposing surface of the housing facing the substrate and each of the ground electrodes are electrically connected. Wherein the width of the signal electrode at the connection portion between the signal electrode and the high-frequency connector is equal to or less than the width of the connection portion of the high-frequency connector with the signal electrode. This is related to the mounting structure.

Hereinafter, the contents and operational effects of the present invention will be sequentially described with reference to the drawings. FIG. 1 is a plan view showing a mounting structure according to an embodiment of the present invention, and FIG.
FIG. 3 is a perspective view of the mounting structure of FIG. 1, and FIGS. 3A and 3B are diagrams schematically illustrating a cross-sectional structure of a waveguide optical device. FIG. 4 is a plan view showing a main part of a mounting structure of a conventional waveguide type optical device, and FIG. 5 is a partially enlarged portion of FIG. However, in FIGS. 4 and 5, the same components as those shown in FIG. 14 are denoted by the same reference numerals, and the description of those components will be omitted.

The present inventor has been studying the form of the substrate and the like in increasing the frequency of the loss dip of the waveguide type optical device, but has hardly studied the improvement of the mounting structure. Focusing on the fact that it has not been developed, we examined the relationship between the mounting structure and the transmission characteristics.

For example, in FIGS. 4 and 5, it is usually necessary to match the impedance to 50Ω.
The distance between the end surface 9a and the substrate end surface 2a is 0.05 to 0.1.
mm. The difference t between the width m of the connection portion of the outer ground electrode 4A and the width n of the conductor 17 is 1 to 10 mm.
Therefore, a step B having a dimension t occurs between the edge of the ground electrode 4A and the edge of the conductor 17. In addition, the width s of the conductor 19 is usually considerably smaller than the width r at the connection portion of the inner ground electrode 6A, so that the ground electrode 6A
Between the edge of the conductor 19 and the edge of the conductor 19. The dimension w of the step C is usually 0.5 to 5 mm.

Similarly, the width q of the substrate connection conductor 11 is usually considerably smaller than the width p at the connection portion of the signal electrode 5A, so that the edge of the signal electrode 5A is connected to the substrate connection. A step A is formed between the conductor 11 and the edge.
The dimension u of the step A is usually 0.05 to 0.1 mm, and v
Is usually 0.05 to 0.1 mm.

The present inventor has focused on such a mounting structure, and as a result, has found for the first time that the present invention is deeply related to the loss dip frequency. This will be described with reference to a virtual equivalent circuit in FIG. If 13 is a signal generator, the signal electrode 5A acts as a resistance line. This resistance is R, and the inductance is L. Specifically, first, the ground electrodes 4A, 6A and the opposing surface 9a of the housing 9 are electrically connected by metal foils (a kind of conductor) 17, 19, respectively. It is considered that the capacitor Ce having the gap between the end of the substrate and the facing surface 9a as an insulator is generated. That is, when the equivalent circuit shown in FIG.
, The resistor R, the inductance L, and the capacitor Ce are connected in parallel. When the frequency of the microwave signal voltage rises to a specific region, the capacitor Ce, the resistance, and the inductance generate a resonance circuit, and power energy leaks into the resonance circuit. As a result, it is considered that a large loss dip occurred at the specific frequency.

For this reason, the present inventor interposes the opposing surface 9a of the housing 9 opposing the substrate and the ground electrodes 4A and 6A between the opposing surface 9a and the end surface 2a of the substrate 2. It has been conceived that each of them is directly connected by the conductive material layer.
As a result, there is no space between the opposing surface 9a and the end surface 2a of the substrate 2, and the distance between the two becomes the thickness of the conductive material layer (that is, 50 to 100 μm), so that the parasitic capacitance of the capacitor almost disappears. This minimized leakage of power energy.

Further, as a result of further study, the present inventors have found out the generation of a parasitic capacitance and a resonance circuit by a mechanism similar to the above, which has not been paid attention in the past. That is, in FIG. 5, the steps B and C between the ground electrode and the conductor and the step A between the signal electrode and the substrate connecting conductor 11 have caused such parasitic capacitance. The signal electrode 5A extends substantially parallel to the ground electrodes 4A and 6A. At this time, each part of the signal electrode 5A and the ground electrodes 4A and 6A
A minute condenser is generated between each part. When this minute condenser is integrated and displayed in a simplified manner, Cd shown in FIG. 6 is obtained.

However, in addition to this, the conductors 17, 19
Parasitic capacitance also occurs in steps B and C between the edge portions of the ground electrodes 4A and 6A. This parasitic capacitance is also obtained by integrating a minute capacitor having a complicated spatial arrangement, but is simplified as Cb and Cc in FIG. The capacitors Cb and Cc are connected to the signal electrode 5A.
Are connected in parallel. In addition, the board connection conductor 11
A parasitic capacitance is also generated at a step A between the first electrode and the both edges of the signal electrode 5A. This parasitic capacitance is simplified and shown as Ca in FIG. The capacitor Ca is connected in parallel to the signal electrode 5A.

When the frequency of the microwave signal voltage rises to a specific region, these capacitors Ca, Cb, Cc
, The resistor R, and the inductance L form a resonance circuit, and power energy leaks into the resonance circuit. As a result, it is considered that a large loss dip occurred at the specific frequency.

The present inventor has arrived at each of the above-mentioned inventions based on this finding. Specifically, as shown in FIGS. 1 and 2, a pair of ground electrodes 4 and 6 and a signal electrode 5 were formed on a substrate 2, and an end surface 2 a of the substrate was opposed to an opposing surface 9 a of a housing 9. . The housing 9 and the ground electrodes 4 and 6 were connected by conductors 10 and 12 such as metal foils, respectively.

In the present invention, at the connection portions between the ground electrodes 4 and 6 and the conductors 10 and 12, the edges of the ground electrodes 4 and 6 on the signal electrode 5 side and the edges of the conductors 10 and 12 are connected. The part was made to continue substantially without a step. In other words, there is no difference between the width m at the connection portion of the outer ground electrode 4 and the width n of the conductor 10, and the difference between the width r at the connection portion of the inner ground electrode 6 and the width s of the conductor 12 is eliminated. Was eliminated, and the steps were eliminated.

Thus, the parasitic capacitances Cb and Cc in parallel with the resistance R and the inductance L shown in FIG.
Leakage of power energy due to resonance between these parasitic capacitance, resistance and inductance can be prevented.

In the present invention, when connecting the high-frequency connector 40 on the housing 9 and the signal electrode 5,
At the connection portion between the signal electrode 5 and the high-frequency connector 40, the width p of the signal electrode 5 is set to be equal to or less than the width q of the connection portion 11 of the high-frequency connector 40 with the signal electrode 5. Thus, the parasitic capacitance Ca in parallel with the resistor R and the inductance L shown in FIG. 6 is eliminated, and leakage of power energy due to resonance between the parasitic capacitance, the resistor, and the inductance can be prevented.

However, the actual positional accuracy when forming the electrodes,
In addition, since there is a limit in the accuracy of alignment between the ground electrodes 4 and 6 and the conductors 10 and 12, an error of 25 μm or less is allowed.

Next, specific embodiments of the present invention will be described in more detail. In the optical modulator, a signal generator 13 is preferably connected to one of the signal electrodes 5, and a resistor 14 and a ground 15 are connected to the other.

As the material of the substrate, lithium niobate,
Electro-optical crystals such as lithium tantalate and lithium niobate-lithium tantalate solid solution are particularly preferred. Also,
The crystal orientation of the electro-optic crystal constituting the substrate is preferably z-cut or x-cut. For example, in the waveguide type optical device 1 shown in FIG.
The titanium diffused optical waveguides 3a and 3b are formed therein, and a buffer layer 36 is formed thereon as necessary, and the ground electrodes 4, 6 and the signal electrode 5 are formed on the buffer layer 36. Each of the optical waveguides 3a and 3b is connected to each of the electrodes 4,
It is directly below 5.

The waveguide type optical device 1A shown in FIG.
In the above, titanium diffused optical waveguides 3a and 3b are formed in the substrate 2 which has been cut x, and a buffer layer 36 is formed on the titanium diffused optical waveguide 3 if necessary, and the ground electrodes 4 and 6 are formed on the buffer layer 36. The signal electrode 5 is formed. Each optical waveguide 3
a, 3b are respectively between the electrodes 4 and 5, electrodes 5 and 6
Between.

As a method for forming the optical waveguide, an internal diffusion method such as a titanium diffusion method or a proton exchange method can be used. Also,
The waveguide type optical device of the present invention can be suitably used as an optical phase modulator, a polarization scrambler, an optical switching element, an optical logic element for an optical computer, and the like, in addition to the optical modulator described above.

When the opposing surface of the housing and each ground electrode are connected by a conductive material layer interposed between the opposing surface of the housing and the end surface of the substrate, various materials are used as the conductive material layers. Although it is possible, it is particularly preferable to use a cured product of the conductive paste layer because the substrate can be mechanically fixed to the housing.

As such a conductive paste, a noble metal paste such as a gold paste, a silver paste, and a platinum paste is particularly preferable. However, solder can also be used.

In the connection portion between each ground electrode and each conductive material layer, it is particularly preferable that the edge of each ground electrode on the signal electrode side and the edge of each conductive material layer be substantially continuous without any step. Thereby, the above-described effects can be obtained. In this case, furthermore, at the connection portion between each ground electrode and each conductive material layer, the edges at both ends of each ground electrode and the edges at both ends of each conductive material layer should be substantially continuous without any step. Is preferred.

FIG. 7 is a plan view showing a mounting structure according to a preferred embodiment of the present invention, FIG. 8 is a perspective view of the mounting structure of FIG. 7, and FIG. 9 is a housing and a waveguide type optical device 1. FIG. 4 is a plan view showing a state before bonding is performed. As a preferred manufacturing procedure, as shown in FIG. 9, the casing 9 and the board 2 are brought as close as possible, the board connecting conductor 11 of the high-frequency connector 40 is positioned with respect to the end of the signal electrode 5, and the board and the casing are connected to each other. Temporarily. Next, the board connection conductor 11 of the high-frequency connector is connected to the end of the signal electrode 5. Next, conductive paste layers 20A and 21A are formed on the facing surface 9a of the housing 9 at positions corresponding to the ground electrodes 4 and 6, and the conductive paste layers are brought into contact with the ground electrodes 4 and 6, respectively. In this state, the conductive paste is heat-treated to form cured layers 20, 21 of the conductive paste as shown in FIGS.

In this embodiment, each of the ground electrodes 4 and 6
In the connection portion between the conductive material layers 20 and 21, the edges at both ends of the ground electrodes 4 and 6 and the edges at both ends of the conductive material layers 20 and 21 are respectively continuous substantially without a step. I have.

The length of the waveguide type optical device 1 is 40-60.
mm, and warpage may occur on the end surface 2a of the substrate 2 with the accuracy of the current machine tool. The dimension of the space between the end face 2a of the substrate and the facing surface 9a of the housing due to the warpage is usually 50 to 100 μm. Due to the unavoidable void remaining, the above-mentioned parasitic capacitance may be generated particularly in a high frequency region of 20 GHz or more. But,
In the present embodiment, since the gap can be substantially filled with the conductive material layer, unavoidable parasitic capacitance caused by the limit of accuracy of the machine tool can be suppressed to a minimum.

In general, in an optical modulator of the type described above, it is necessary to consider impedance matching at, for example, 50Ω. The matching of the impedance, reduces the microwave radiation upon the application of a microwave signal voltage to the signal electrode, the transmission characteristics (S _{2 1)} can be further improved. However, when an electro-optic crystal having a high dielectric constant such as lithium niobate is used, the width of the signal electrode tends to be narrow. In this case, the width of the signal electrode at the connection portion between the signal electrode and the high-frequency connector is made smaller than the width of the connection portion between the signal electrode and the high-frequency connector to cope with the decrease in the width of the signal electrode. it can.

FIG. 10 is a plan view showing a mounting structure of the waveguide type optical device 1B and the housing 9 according to this embodiment. However, the same reference numerals are given to the components shown in FIG. 7, and the description thereof will be omitted. The board connection conductor 11 of the high-frequency connector 40 is connected to the signal electrode 5B.
The width p of the signal electrode 5B at this connection portion is smaller than the width q of the substrate connection conductor 11. By thus reducing the width of the signal electrode 5B, the resistance value in the signal electrode can be increased, and impedance matching can be realized.

In order to realize impedance matching of 50Ω in the lithium niobate substrate, it is preferable that the width p of the signal electrode 5B is 100 to 200 μm. On the other hand, the width q of the substrate connection conductor 11 is preferably 100 to 150 μm in order to efficiently perform the operation of connecting the conductor 11 and the signal electrode 5B to each other under a microscope.

In this embodiment, the width of the signal electrode is
It is preferable that the width be equal to or less than twice the width of the connection portion of the high-frequency connector with the signal electrode. However, if the width of the signal electrode is too small than the width of the connection portion with the signal electrode of the high-frequency connector, parasitic capacitance may be generated at this connection portion. It is preferable that the width is 0.5 times or more of the width of the connection portion with.

In each of the above-described embodiments, the width of the conductive material layer and the width of the ground electrode are made equal. This is particularly preferable because the entire region of the ground electrode on the substrate end surface 2a side can be electrically connected to the ground of the housing and grounded. On the other hand, in another preferred embodiment,
A metal plating layer continuous with each ground electrode is formed on the end surface of the substrate, and the metal plating layer and the opposing surface of the housing can be connected by a conductive material layer. Also in this case, the entire region of the ground electrode on the substrate end surface 2a side can be electrically connected to the ground of the housing and grounded.

FIG. 12 is a plan view showing a mounting structure according to this embodiment, and FIG. 11 shows an assembly before the mounting structure of FIG. 12 is created. In the present waveguide type optical device 1C, metal plating layers 25 and 26 are formed in the area of the ground electrodes 4 and 6 on the end surface 2a of the substrate 2, and each metal plating layer 25 and 26 is 4, 6 are electrically connected. End face 2a of substrate 2
And the opposing surface 9 a of the housing 9.

Next, as shown in FIG. 12, a conductive material layer 27 is formed between the metal plating layer 25 and the facing surface 9a, and two conductive material layers are formed between the metal plating layer 26 and the facing surface 9a. 28 are formed. At this time, the signal electrode 5 of each conductive material layer 27 is
The edge on the B side and the edge of the ground electrode 4 on the signal electrode side are made to be substantially continuous without any step. In addition, each conductive material layer 28
Of the signal electrode 5B and the edge of the ground electrode 6 on the signal electrode side are substantially continuous without any step.

In order to form this conductive material layer, it is preferable to drop the conductive paste at a position corresponding to each of the conductive material layers 27 and 28 and to cure the conductive paste. By substituting the ground of the ground electrodes 4 and 6 on the side of the substrate end surface 2a by the metal plating layer, the mounting process of the substrate is further facilitated.

[0046]

【Example】

Example (Manufacture of Waveguide Optical Device 1) The mounting structure shown in FIGS. 7 to 9 was manufactured, and the frequency dependence of its transmission characteristics was tested. First, a Z-cut lithium niobate wafer was prepared. Patterning by photolithography method, 800 angstrom thickness, 7 μm width on main surface of wafer
m m-Zehnder-shaped metal titanium film was formed.
The film was diffused to a substrate by a thermal diffusion method to form a titanium diffused optical waveguide 3. On top of this, S of 1-2 μm thick
An iO ₂ buffer layer was formed, modulation electrodes 4, 5, and 6 were formed on the buffer layer, and a 15 μm-thick plating was performed on each electrode. Cut this wafer, thickness 0.5m
The waveguide type optical device 1 having a length of 0.8 mm, a width of 0.8 mm and a length of 60 mm was manufactured. The end faces 2c and 2d were optically polished.

(Mounting) The end face 2 a of the board 2 is brought as close as possible to the facing face 9 a of the housing,
The substrate connection conductor 11 was positioned with respect to the signal electrode 5 with an accuracy of 50 μm or less, and the substrate 2 and the housing 9 were temporarily fixed. Next, the board connection conductor 11 of the high-frequency connector 40
Was connected to the signal electrode 5 by gold crimping. Next, as shown in FIG. 9, a silver paste was filled as a conductive paste between the housing and the substrate. This was heated at 120 ° C. for 30 minutes or more and cured to form conductive material layers 20 and 21. Next, predetermined electrical wiring was provided, and an optical waveguide and an optical fiber were connected (not shown) using an ultraviolet curable resin to obtain a device for measurement.

(Measurement of High-Frequency Electrode Characteristics) The device of the example and the measuring instrument were connected by a high-frequency cable. From the measuring instrument, frequency outputs gradually changes sweep signal was measured transmission characteristic (S _{2 1)} at each frequency. FIG. 13 shows the measurement results. As can be seen from this result, 35
The loss dip was successfully removed within the range of GHz or less.

Comparative Example A mounting structure shown in FIGS. 14 to 16 was manufactured. The waveguide type optical device 16 was manufactured as described in the section of Examples. However, the shape of each ground electrode and signal electrode is different from the electrode shape of the embodiment.

The conductor 11 for connection to the board of the high-frequency connector 40
Was positioned with respect to the signal electrode 5 with an accuracy of 50 μm or less, and the substrate 2 and the housing 9 were temporarily fixed. Next, the substrate connection conductor 11 of the high-frequency connector was connected to the signal electrode 5 by gold crimping. In addition, each ground electrode was connected to the housing 9 by each gold foil 17 and 19. Next, predetermined electrical wiring was provided, and an optical waveguide and an optical fiber were connected (not shown) using an ultraviolet curable resin to obtain a device for measurement.

The transmission characteristics of this device were measured in the same manner as in the example. FIG. 17 shows the measurement results.
As can be seen from this result, a loss dip occurs at about 27 GHz.

[0052]

According to the present invention, a substrate on which an optical waveguide is formed, a signal electrode formed on the main surface of the substrate, and a pair of grounds formed so as to sandwich the signal electrode. And a microwave signal voltage applied to the signal electrode and a lightwave propagating in the optical waveguide are configured to interact with each other. It can be shifted to the high frequency side.

[Brief description of the drawings]

FIG. 1 is a plan view of a mounting structure according to an embodiment of the present invention.

FIG. 2 is a perspective view of the mounting structure of FIG.

FIG. 3A is a configuration example of a waveguide-type optical device when a z-cut electro-optic crystal is used, and FIG.
Is a configuration example of a waveguide type optical device when an x-cut electro-optic crystal is used.

FIG. 4 is a plan view of a mounting structure of a conventional waveguide type optical device 16.

FIG. 5 is a partially enlarged view of FIG. 6;

FIG. 6 is an equivalent circuit diagram of the mounting structure of FIG. 5;

FIG. 7 is a plan view of a mounting structure according to another embodiment of the present invention.

FIG. 8 is a perspective view of the mounting structure of FIG. 7;

FIG. 9 is a plan view showing a state before creating the mounting structure of FIGS. 7 and 8;

FIG. 10 is a plan view showing a mounting structure according to still another embodiment of the present invention.

FIG. 11 is a plan view showing a state before manufacturing the mounting structure of FIG. 12;

FIG. 12 is a plan view showing a mounting structure according to still another embodiment of the present invention.

FIG. 13 is a graph showing frequency dependence of transmission characteristics of the mounting structure according to the embodiment of the present invention.

FIG. 14 is a plan view showing a waveguide type optical device 16;

FIG. 15 is a perspective view showing an example of a conventional mounting structure.

FIG. 16 is a partially enlarged view of FIG.

FIG. 17 is a graph showing frequency dependence of transmission characteristics of a mounting structure according to a comparative example.

[Explanation of symbols]

1, 1A, 1B, 1C Waveguide type optical device 2 Substrate 2a End face of substrate 2 3, 3a, 3b Optical waveguide 4, 4A, 6, 6A Ground electrode 5, 5A, 5B Signal electrode 9 Casing 9a End face of casing 9 10 , 12, 17, 19 Conductor 11 Conductor for substrate connection (connection portion of high-frequency connector) 20A, 21A Conductive paste layer 20, 21 Hardened layer of conductive paste (conductive material layer) 25, 26 Metal plating layer 40 High-frequency connector (Center conductor) A Step at connection between signal electrode and high frequency connector B, C Step at connection between ground electrode and conductor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideto Wakihama 585 Tomimachi, Funabashi-shi, Chiba Sumitomo Osaka Cement Co., Ltd. Optoelectronics Division

Claims (8)

[Claims] 1. A mounting structure comprising a waveguide type optical device and a housing for accommodating the waveguide type optical device, wherein the waveguide type optical device comprises: a substrate on which an optical waveguide is formed; A signal electrode formed on the main surface of the substrate; and a pair of ground electrodes formed so as to sandwich the signal electrode. The microwave signal voltage applied to the signal electrode and the light guide The light wave propagating in the wave path is configured to be able to interact, the high-frequency connector on the housing side and the signal electrode are connected, and the opposing surface of the housing opposing the substrate and the Wherein each of the ground electrodes is connected by a conductive material layer interposed between the facing surface and an end surface of the substrate. 2. The mounting structure of a waveguide type optical device according to claim 1, wherein said conductive material layer is made of a cured product of a conductive paste layer. 3. A connection portion between each of the ground electrodes and each of the conductive material layers, an edge of each of the ground electrodes on the signal electrode side and an edge of each of the conductive material layers are substantially formed. 3. The mounting structure for a waveguide-type optical device according to claim 1, wherein the mounting structure is continuous without any step. 4. In a connection portion between each of said ground electrodes and each of said conductive material layers, edges at both ends of each of said ground electrodes and edges at both ends of each of said conductive material layers are substantially respectively formed. 4. The mounting structure for a waveguide type optical device according to claim 3, wherein the structure is continuous without any step. 5. A metal plating layer is formed on the end surface of the substrate, the metal plating layer being continuous with each of the ground electrodes, and the metal plating layer and the facing surface of the housing are connected by the conductive material layer. The mounting structure of a waveguide-type optical device according to any one of claims 1 to 4, characterized in that: 6. A connection part between the signal electrode and the high-frequency connector, wherein a width of the signal electrode is equal to or smaller than a width of a connection part of the high-frequency connector with the signal electrode. A mounting structure of the waveguide-type optical device according to claim 5. 7. A mounting structure comprising a waveguide type optical device and a housing for accommodating the waveguide type optical device, wherein the waveguide type optical device comprises: a substrate on which an optical waveguide is formed; A signal electrode formed on the main surface of the substrate; and a pair of ground electrodes formed so as to sandwich the signal electrode. The microwave signal voltage applied to the signal electrode and the light guide The light wave propagating in the wave path is configured to be able to interact, the high-frequency connector on the housing side and the signal electrode are connected, and the opposing surface of the housing opposing the substrate and the Are connected to each other by a conductor, and at a connection portion between each of the ground electrodes and each of the conductors, an edge of the ground electrode on the side of the signal electrode and each of the conductors are connected. Substantial body edges Characterized in that it continuously without any step, the waveguide type optical device mounting structure. 8. A mounting structure comprising a waveguide type optical device and a housing for accommodating the waveguide type optical device, wherein the waveguide type optical device comprises: a substrate on which an optical waveguide is formed; A signal electrode formed on the main surface of the substrate; and a pair of ground electrodes formed so as to sandwich the signal electrode. The microwave signal voltage applied to the signal electrode and the light guide The light wave propagating in the wave path is configured to be able to interact, the high-frequency connector on the housing side and the signal electrode are connected, and the opposing surface of the housing opposing the substrate and the Are electrically connected to each other, and at the connection portion between the signal electrode and the high-frequency connector, the width of the signal electrode is equal to or less than the width of the connection portion of the high-frequency connector with the signal electrode. Ah Wherein the waveguide type optical device mounting structure.