JP5494704B2 - Optical waveguide device module - Google Patents

Description

  The present invention relates to an optical waveguide element module, and more particularly to an optical waveguide element module in which an optical waveguide element and a connection substrate are accommodated in a housing.

  In the optical measurement technical field and the optical communication technical field, an optical waveguide element in which an optical waveguide is formed on a substrate having an electrooptic effect such as an optical modulator or an optical switch is often used. These optical waveguide elements are usually housed in a hermetically sealed casing (case) to constitute an optical waveguide element module.

  As shown in Patent Literature 1, a relay substrate for electrically connecting an external input line to a control electrode of an optical waveguide element and an output of the control electrode of the optical waveguide element are provided in the housing of the optical waveguide element module. A termination board is accommodated which is electrically connected to the side and absorbs the output signal or leads it out of the module.

  Usually, in order to reduce the discontinuity at the connection portion and improve the frequency characteristics, as shown in FIG. 1, the electrode dimensions of the modulation substrate and the relay substrate constituting the optical waveguide element and the distance between the ground electrode (GND) Are designed to be equal. The same applies to the connection between the termination substrate and the modulation substrate. Thus, when the dimensions and intervals of the electrodes of the modulation substrate and the connection substrate are matched, it is necessary to prepare connection substrates for the types of optical waveguide elements, which causes an increase in manufacturing cost.

  Further, as the frequency of optical waveguide elements is increased (widened), a material having a low dielectric constant is used for the relay substrate shown in FIG. 2 as compared with a substrate (modulation substrate) such as alumina that constitutes the optical waveguide element. It has become. In such a case, since the dielectric constants of the relay substrate and the optical waveguide element are different, discontinuity occurs in the connection portion, which causes the electrical characteristics to deteriorate. In addition, if the width of the signal line and the distance between the ground (GND) lines are suddenly changed between the input side and the output side of the relay board, impedance mismatch between the external input line and the relay board and the optical waveguide element Is likely to occur, and the deterioration of electrical characteristics becomes more remarkable.

JP 2003-233043 A

  The problem to be solved by the present invention is to solve the above-described problems, match the impedance of the external input line, the relay substrate and the optical waveguide element, and further connect the optical waveguide element and the connection substrate (relay substrate or termination substrate). And an optical waveguide element module in which the electrical discontinuity is reduced and deterioration of electrical characteristics is prevented. In addition, it is possible to provide an optical waveguide element module that enables a common connection substrate to be used for different types of optical waveguide elements, and that reduces manufacturing costs.

  In order to solve the above problems, an invention according to claim 1 includes a substrate having an electro-optic effect, an optical waveguide formed on the substrate, and a control electrode for controlling a light wave propagating through the optical waveguide. An optical waveguide element, a connection substrate provided outside the optical waveguide element and having a wiring electrically connected to the control electrode, and an optical waveguide element that accommodates the optical waveguide element and the connection substrate in a housing In the module, the control electrode includes a signal electrode and a ground electrode disposed so as to sandwich the signal electrode, and the connection substrate includes a signal line and a ground line disposed so as to sandwich the signal line. The dielectric constant of the connection substrate is lower than the dielectric constant of the substrate constituting the optical waveguide element, and the width S1 of the signal electrode at the input end or output end of the control electrode is determined by the optical waveguide element. Width of the signal line on the side 2 or less, and the interval W1 between the ground electrodes at the input end or the output end is larger than the interval W2 between the ground lines on the optical waveguide element side of the connection substrate, and the control electrode A portion remote from the input end portion or the output end portion, and having a portion where the interval between the ground electrodes is smaller than the interval W2, and having a grounding wiring for connecting the optical waveguide element and the connection substrate. Features.

  According to a second aspect of the present invention, in the optical waveguide element module according to the first aspect, the ground electrode and the ground line are connected by a plurality of ground wirings.

  The invention according to claim 3 is the optical waveguide element module according to claim 1 or 2, wherein the ground wiring interval W is smaller than the interval W1.

  According to a fourth aspect of the present invention, in the optical waveguide element module according to any one of the first to third aspects, the connection position of the end portion on the optical waveguide element side of the grounding wiring is smaller than the interval W2. It has the wiring connected to the part.

  According to a fifth aspect of the present invention, in the optical waveguide device module according to any one of the first to fourth aspects, the grounding wiring that connects the optical waveguide device and the connection substrate is sandwiched, and a wiring interval is set. Another wiring is larger than the interval W1.

  The invention according to claim 6 is the optical waveguide element module according to any one of claims 1 to 5, wherein the wiring connecting the optical waveguide element and the connection substrate is wire bonding.

  According to the invention of claim 1, the dielectric constant of the connection substrate is lower than the dielectric constant of the substrate constituting the optical waveguide element, and the width S1 of the signal electrode at the input end or output end of the control electrode is The width W2 of the signal line on the optical waveguide element side is equal to or smaller than the width S2, and the distance W1 between the ground electrodes at the input end or the output end is equal to the distance W2 between the ground lines on the optical waveguide element side of the connection substrate. The control electrode has a portion where the distance between the ground electrodes is smaller than the distance W2 at a portion away from the input end portion or the output end portion, and the optical waveguide element and the connection substrate Therefore, it is possible to match the input lines from the outside with the impedance of the relay substrate and the optical waveguide element. In addition, when impedance is matched in this way, an electrical discontinuity usually occurs due to the connecting portion. However, according to the present invention, the electrical strength discontinuity can be suppressed and deterioration of electrical characteristics can be prevented. In addition, it is possible to cope with optical waveguide elements having different electrode dimensions and intervals with a common connection substrate, thereby realizing a reduction in manufacturing cost.

  According to the invention according to claim 2, since the ground electrode and the ground line are connected by a plurality of grounding wires, the electrical connectivity between the connection substrate and the optical waveguide element is discontinuous. It is possible to suppress and prevent deterioration of electrical characteristics.

  According to the invention of claim 3, since the ground wiring interval W is smaller than the interval W1, the electric field strength in the signal portion and the ground portion is different between the connection substrate and the optical waveguide element. It is possible to suppress the electrical discontinuous portion at the connecting portion between the two and prevent the electrical characteristics such as the high frequency characteristics from deteriorating.

  According to the invention of claim 4, since the connection position of the end portion of the grounding wiring on the side of the optical waveguide element is connected to a portion smaller than the interval W2, the electric field strength from the connection substrate side to the optical waveguide element side Can be changed more continuously, and it is possible to suppress deterioration of electrical characteristics.

  According to the fifth aspect of the present invention, since the wiring for grounding that connects the optical waveguide element and the connection substrate is sandwiched between the wirings, and the wiring spacing is larger than the interval W1, the grounding portion is more electrically connected. It is possible to perform reliably.

  According to the invention of claim 6, since the wiring connecting the optical waveguide element and the connection substrate is wire bonding, the wiring interval W for grounding can be easily set so as to be smaller than the interval W1. It becomes.

It is a figure explaining the conventional optical waveguide element module. It is a figure explaining the electrode structure of this invention etc. which used the material whose dielectric constant is lower than the board | substrate of an optical waveguide element for a relay board | substrate. It is a figure explaining the wiring condition of the optical waveguide element utilized for the optical waveguide element module of this invention, and a connection board | substrate. It is a graph which shows the result of each optical frequency response at the time of using the optical waveguide element module of this invention shown in FIG.2 and FIG.3. It is a figure which shows the example of wiring when the space | interval of the ground electrode of the optical waveguide element in the optical waveguide element module of this invention changes suddenly. It is a figure which shows the example of wiring when the width | variety of the signal electrode of the optical waveguide element in the optical waveguide element module of this invention and the width | variety of the signal line | wire of a connection board | substrate are equal.

Hereinafter, the optical waveguide device module of the present invention will be described in detail using preferred examples. FIG. 2 is a diagram for explaining the electrode structure and the like of the present invention, and a material having a lower dielectric constant than the substrate constituting the optical waveguide element is used for the relay substrate of FIG.
And as shown in FIG.2 (b) (it is an enlarged view of the code | symbol X part of Fig.2 (a)), this invention is a board | substrate which has an electrooptic effect, The optical waveguide formed in this board | substrate, An optical waveguide element having a control electrode for controlling a light wave propagating through the optical waveguide; a connection substrate provided outside the optical waveguide element and having a wiring electrically connected to the control electrode; and In the optical waveguide device module that houses the optical waveguide device and the connection substrate in a housing, the control electrode is composed of a signal electrode and a ground electrode arranged so as to sandwich the signal electrode. A signal line and a ground line arranged so as to sandwich the signal line, and a dielectric constant of the connection substrate is lower than a dielectric constant of the substrate constituting the optical waveguide element, and an input end of the control electrode Alternatively, the width S1 of the signal electrode at the output end The width W2 of the signal line on the optical waveguide element side is equal to or smaller than the width S2 of the ground line on the optical waveguide element side of the connection substrate. The control electrode has a portion where the distance between the ground electrodes is smaller than the interval W2 at a portion away from the input end portion or the output end portion, and the control electrode is connected to the optical waveguide element and the connection. It has the wiring 2 for grounding which connects a board | substrate, It is characterized by the above-mentioned. Reference numerals 1 and 2 are wirings for electrically connecting the optical waveguide element and the relay substrate.

As a substrate having an electro-optic effect, any single crystal of LiNbO ₃ , LiTaO ₅ or PLZT (lead lanthanum zirconate titanate) can be suitably used. In particular, LiNbO ₃ and LiTaO ₅ frequently used in optical modulators are preferable. The optical waveguide formed on the substrate is formed, for example, by thermally diffusing a high refractive index material such as titanium (Ti) on a LiNbO ₃ substrate (LN substrate). It is also possible to form a ridge-type waveguide by forming a groove on the side surface of the optical waveguide or by forming the optical waveguide portion thicker than other substrate portions.

The control electrode is composed of a signal electrode and a ground electrode, and can be formed by forming a Ti / Au electrode pattern on the surface of the substrate and using a gold plating method or the like. Furthermore, a buffer layer such as a dielectric SiO ₂ can be provided on the substrate surface after the formation of the optical waveguide, if necessary.

  The “connection board” in the present invention is connected to a relay board for connecting an input terminal for inputting an electric signal from the outside and a signal input portion of the optical waveguide element, or to an output end portion of a signal electrode of the optical waveguide element. It means a terminator that absorbs an electric signal with a resistor or the like in order to suppress reflection of the electric signal, or a termination substrate that connects the output end of the signal electrode of the optical waveguide element and the output terminal. As the substrate material of the connection substrate, a material having a dielectric constant lower than that of the substrate material of the optical waveguide element, for example, alumina or a semiconductor material is used. This is to contribute to the broadening of the optical waveguide device.

  For the wiring connecting the optical waveguide element and the connection substrate, a gold wire or a wide gold ribbon can be used. In particular, the method of wire bonding the gold wire is preferable as the wiring method of both. Also, the number of wirings is not limited to one, and the vicinity of the same place can be connected by a plurality of gold wires, or the ground electrode and the ground line can be connected by a plurality of grounding wires as shown in FIG. Is possible.

  As shown in FIG. 3, the distance W1 between the ground electrodes of the optical waveguide element is different from the distance W2 between the ground lines of the connection substrate. In particular, when the distance W1 is larger than the distance W2, the connection substrate, the optical waveguide element, The interval W between the wirings 3 to be connected is made smaller than the interval W1. As a result, the difference between the electric field strength between the signal electrode and the ground electrode of the optical waveguide element and the electric field strength between the signal line and the ground line of the connection substrate is reduced, and the optical frequency response is improved.

  Further, the connection position of the end portion on the optical waveguide element side of the grounding wiring 3 can be connected to a portion smaller than the interval W2. In such a case, the change in the electric field strength from the connection substrate side to the optical waveguide element side can be changed more continuously, so that it is possible to further suppress the deterioration of the electrical characteristics.

  As shown in FIG. 3, it is also possible to provide another wiring 2 that is arranged so as to sandwich a grounding wiring that connects the optical waveguide element and the connection substrate, and whose wiring interval is larger than the interval W1. Such a wiring 2 is the same as the wiring 2 shown in FIG. By connecting the ground electrode with the wirings 2 and 3, the ground portion can be more reliably electrically connected.

  In FIG. 3, since the width of the signal electrode at the input end or the output end of the control electrode is different from the width of the signal line on the optical waveguide element side, the electrical discontinuity due to the connecting portion is usually used. However, as in the present invention, by setting the grounding wiring interval W connecting the optical waveguide element and the connection substrate to be smaller than the interval W1, the electrical strength discontinuity is suppressed and the electrical characteristics are reduced. It is possible to prevent the deterioration of the material.

  The width of the signal line of the connection substrate is in the range of 0.1 mm to 1 mm, more preferably 0.2 mm to 0.5 mm. Further, the thickness of the connection substrate is 0.1 mm to 1 mm, and more preferably 0.2 mm to 0.5 mm.

  The width of the end portion of the signal electrode constituting the optical waveguide element is 0.03 mm to 0.5 mm, more preferably 0.05 mm to 0.25 mm.

  As shown in FIG. 5, even when the width of the ground electrode changes abruptly, by providing the wiring 3 as in the present invention, it is possible to alleviate the abrupt change in electric field strength.

  Further, as shown in FIG. 6, the width of the signal line of the connection substrate and the width of the signal electrode of the optical waveguide element are configured to be approximately the same, and a plurality of gold wires or wide gold ribbons are used for connection. As a result, the high-frequency characteristics can be improved. In such a case, there is a high possibility that the distance between the ground lines is different from the distance between the ground electrodes due to impedance matching, and therefore the wiring connection method as in the present invention is more effectively applied. Is possible.

  Optical frequency response results of the optical waveguide device module (present invention 1) of the first embodiment of the present invention shown in FIG. 2 and the optical waveguide device module (present invention 2) of the second embodiment of the present invention shown in FIG. Is shown in FIG. It can be easily understood from the graph of FIG. 4 that the characteristics of the optical waveguide device module of the present invention are improved over the entire frequency band.

  As described above, according to the present invention, the impedance of the input line from the outside and the impedance of the relay substrate and the optical waveguide element are matched, and further, the discontinuity of the electrical connection between the optical waveguide element and the connection substrate is reduced, It becomes possible to provide an optical waveguide device module in which deterioration of electrical characteristics is prevented. In addition, a common connection substrate can be used for different types of optical waveguide elements, and an optical waveguide element module with reduced manufacturing costs can be provided.

Claims (6)

A substrate having an electro-optic effect, an optical waveguide formed on the substrate, an optical waveguide element having a control electrode for controlling a light wave propagating through the optical waveguide, and provided outside the optical waveguide element, In a connection substrate having a wiring electrically connected to the control electrode, and an optical waveguide device module housing the optical waveguide device and the connection substrate in a housing,
The control electrode is composed of a signal electrode and a ground electrode arranged so as to sandwich the signal electrode,
The connection board is provided with a signal line and a ground line arranged so as to sandwich the signal line,
The dielectric constant of the connection substrate is lower than the dielectric constant of the substrate constituting the optical waveguide element,
The width S1 of the signal electrode at the input end or output end of the control electrode is equal to or smaller than the width S2 of the signal line on the optical waveguide element side,
The interval W1 between the ground electrodes at the input end or the output end is larger than the interval W2 between the ground lines on the optical waveguide element side of the connection substrate,
The control electrode has a portion where the distance between the ground electrodes is smaller than the distance W2 at a portion away from the input end or the output end.
An optical waveguide device module comprising a grounding wiring connecting the optical waveguide device and the connection substrate.   2. The optical waveguide element module according to claim 1, wherein the ground electrode and the ground line are connected by a plurality of ground wirings.   3. The optical waveguide element module according to claim 1, wherein the ground wiring interval W is smaller than the interval W <b> 1. 4.   4. The optical waveguide element module according to claim 1, wherein a connection position of an end portion of the grounding wiring on the optical waveguide element side is connected to a portion smaller than the interval W <b> 2. An optical waveguide device module comprising:   5. The optical waveguide element module according to claim 1, wherein the grounding wiring that connects the optical waveguide element and the connection substrate is sandwiched therebetween, and the wiring interval is larger than the interval W <b> 1. An optical waveguide device module comprising wiring.   6. The optical waveguide element module according to claim 1, wherein the wiring connecting the optical waveguide element and the connection substrate is wire bonding.

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