JP2019179165A - Optical waveguide element - Google Patents

Abstract

An optical waveguide device capable of effectively suppressing thermal crosstalk from a bias point adjustment region to a high-frequency modulation region. A substrate having an electro-optic effect, an optical waveguide formed on the substrate, a control electrode for modulating a light wave propagating through the optical waveguide, and adjusting a bias point. In the optical waveguide device (10) having the heater electrode (41), the control electrode is a signal electrode (21) formed on one surface of the substrate and the opposite side of the substrate from the one surface. And a back surface ground electrode (31) formed on the surface of the substrate, wherein the heater electrode is formed on the one surface of the substrate, and the heater electrode is provided below the heater electrode on the opposite surface of the substrate. Characterized by having a heat radiating means (51) for radiating the heat generated by the above. [Selection diagram] FIG.

Description

  The present invention relates to an optical waveguide device using an organic polymer exhibiting an electro-optic effect for an optical waveguide.

  In recent years, in the fields of optical communication and optical measurement, an optical waveguide element in which an optical waveguide is formed using a material exhibiting an electro-optic effect is often used. In general, an optical waveguide element includes a control electrode for controlling a light wave propagating in the optical waveguide together with the optical waveguide.

  As such an optical waveguide element, a Mach-Zehnder type optical modulation element in which a Mach-Zehnder interferometer is formed of an optical waveguide using a material exhibiting an electro-optic effect is widely used. The Mach-Zehnder light modulation element includes an incident waveguide for introducing light from the outside, a branching unit for propagating the light introduced by the incident waveguide in two paths, and a subsequent stage of the branching unit. The two parallel waveguides for propagating the light beams branched into two and the output waveguide for combining the light propagated through the two parallel waveguides and outputting them to the outside. Also, the Mach-Zehnder type light modulation element adjusts the bias point as a control electrode for controlling the light wave, and a high-frequency modulation electrode for applying a high-frequency modulation signal to the light wave propagating through one or both of the parallel waveguides. A bias point adjusting electrode is provided.

  As one type of light modulation element, a light modulation element using an organic electro-optic polymer material in which an organic nonlinear optical compound is dispersed in a polymer material has been developed as a material exhibiting an electro-optic effect. In the case of this light modulation element, a progressive high-frequency electrode is used as the high-frequency modulation electrode in the same manner as the light modulation element using an electro-optic substrate such as a lithium niobate (LN) material. On the other hand, the bias point adjusting electrode is often configured to adjust the bias point by the thermo-optic effect using a heater electrode due to the problem of DC drift.

  Here, a region where a high frequency modulation signal is applied to a light wave propagating through one or both of the parallel waveguides is a high frequency modulation region, and a region where the bias point is adjusted by applying heat from the heater is a bias point adjustment region. In this case, in order to stably operate the light modulation element, it is necessary to suppress thermal crosstalk from the bias point adjustment region to the high frequency modulation region. When thermal crosstalk occurs, optical modulation by high frequency becomes unstable, leading to signal quality degradation.

In order to avoid the occurrence of such a problem, Patent Document 1 proposes an optical modulator made of an organic electro-optic polymer material in which a high-frequency modulation region and a bias point adjustment region are produced by combining elements made of substrates of different materials. Has been.
A technique for suppressing thermal crosstalk has also been proposed for a thermo-optic optical waveguide element having an optical waveguide and a heater electrode. For example, Patent Document 2 discloses an element in which a heat insulating groove is provided between optical waveguides and a heat dissipating material is disposed below the optical waveguide.

  However, as in Patent Document 1, manufacturing each region as a separate element leads to a complicated manufacturing process and an increase in cost. In addition, in the case of a structure in which a heat insulating groove is provided between optical waveguides as in Patent Document 2, in the case of an optical waveguide formed of a polymer material, there is a possibility that the light propagation characteristic is deteriorated due to structural distortion.

Special table 2015-501945 gazette JP 2007-78861 A

  The problem to be solved by the present invention is to solve the above-described problems and provide an optical waveguide device capable of effectively suppressing thermal crosstalk from the bias point adjustment region to the high frequency modulation region. is there.

In order to solve the above problems, the optical waveguide device of the present invention has the following technical features.
(1) Optical light having a substrate having an electro-optic effect, an optical waveguide formed on the substrate, a control electrode for modulating a light wave propagating through the optical waveguide, and a heater electrode for adjusting a bias point In the waveguide element, the control electrode includes a signal electrode formed on one surface of the substrate and a back surface ground electrode formed on a surface opposite to the one surface of the substrate, and the heater electrode Is formed on the one surface of the substrate, and has a heat radiating means for radiating the heat generated by the heater electrode below the heater electrode on the opposite surface of the substrate.

(2) In the optical waveguide device according to (1), the heater electrode has an input end or an output end at one side end along the light wave traveling direction of the substrate. The substrate is formed so that the amount of heat conduction increases toward the one side edge of the substrate.

(3) In the optical waveguide device according to (2), the heat radiating means is a metal, and is formed so that a width in a light wave traveling direction is widened toward the one side end of the substrate. And

(4) In the optical waveguide device according to any one of (1) to (3), the optical waveguide includes a plurality of parallel waveguides extending in parallel, and the heater electrode is formed of the plurality of parallel waveguides. The heat dissipating means is provided on either side, and is formed below the parallel waveguide provided with the heater electrode, but is not formed below the other parallel waveguide.

(5) The optical waveguide device according to any one of (1) to (4), wherein the optical waveguide is formed of an organic polymer material.

  According to the present invention, since the heat dissipating means for dissipating the heat generated by the heater electrode is provided under the heater electrode on the surface opposite to the heater electrode of the substrate, the high frequency modulation is performed from the bias point adjustment region. It is possible to effectively suppress thermal crosstalk to the region.

It is a top view which shows the example of the optical waveguide element which concerns on one Embodiment of this invention. It is a perspective view which shows the back surface ground electrode and metal film for thermal radiation of the optical waveguide element of FIG. It is a side view of the optical waveguide element of FIG. FIG. 2 is a plan view showing an example of an optical modulator in which the optical waveguide element of FIG. 1 is housed in a housing. FIG. 4B is a cross-sectional view taken along line A-A ′ in the optical modulator of FIG. 4A.

The optical waveguide device according to the present invention will be described in detail using a suitable example. In addition, this invention is not limited by the example shown below.
As shown in FIGS. 1 and 2, for example, the optical waveguide device of the present invention includes a substrate (11) having an electro-optic effect, an optical waveguide (12) formed on the substrate, and an optical wave propagating through the optical waveguide. In the optical waveguide device (10) having the control electrode for modulating the temperature and the heater electrode (41) for adjusting the bias point, the control electrode is a signal electrode (on the one surface of the substrate ( 21) and a back surface ground electrode (31) formed on the surface opposite to the one surface of the substrate, the heater electrode being formed on the one surface of the substrate, A heat dissipating means (51) for dissipating heat generated by the heater electrode is provided below the heater electrode on the opposite surface. The heat dissipation means is not limited to the structure formed so as to be in direct contact with the opposite surface of the substrate, and includes a structure formed on another surface of the substrate via another layer different from the heat dissipation means. It is.

  According to such a configuration, since the heat generated from the heater electrode is radiated from the heat radiating means disposed below the heater electrode, it is possible to suppress the heat generated from the heater electrode from propagating to the signal electrode side. . In addition, when the light modulation element is formed, a complicated and high cost is required in which a part for forming a signal electrode and a part for forming a heater electrode are manufactured and joined on separate substrates as in Patent Document 1. A process becomes unnecessary. Therefore, although it has a simple structure, it is possible to suppress thermal crosstalk and to provide a high-performance optical waveguide device at low cost.

Hereinafter, a specific configuration of the optical waveguide device according to the present invention will be described with reference to the drawings.
FIG. 1 is a plan view showing an example of an optical waveguide device according to an embodiment of the present invention. FIG. 2 is a perspective view showing the back ground electrode and the heat-dissipating metal film of the optical waveguide device of FIG. FIG. 3 is a side view of the optical waveguide device of FIG.

  The optical waveguide device 10 of this example includes a base material 15, a substrate 11 having an electro-optic effect, an optical waveguide 12 formed on the substrate, a control electrode for modulating a light wave propagating through the optical waveguide, And a heater electrode 41 for adjusting the bias point.

  The base material 15 is not particularly limited in terms of material and shape as long as it has sufficient flatness to form the optical waveguide 12 and mechanically sufficient strength. As the base material 15, for example, a silicon substrate, a quartz substrate, a glass substrate, a ceramic substrate, or the like can be used.

  The substrate 11 is configured by laminating a lower clad layer, a core layer, an upper clad layer, and the like. A material having a higher refractive index than that of the upper and lower cladding layers is used for the core layer, and the optical waveguide 12 is formed by controlling the shape of the core layer. Although there is no restriction | limiting in particular about the shape of the optical waveguide 12, For example, there exists a rib-shaped optical waveguide which made some core layers protrude the upper side or the lower side.

  At least one of the core layer and the upper and lower cladding layers is formed of an organic electro-optic polymer material in which an organic nonlinear optical compound is dispersed in a polymer material. Examples of the polymer material used for the organic electro-optic polymer material include acrylic resins such as polymethyl methacrylate, epoxy resins, polyimide resins, silicone resins, polystyrene resins, polyamide resins, polyester resins, and phenols. Resin, polyquinoline resin, polyquinoxaline resin, polybenzoxazole resin, polybenzothiazole resin, polybenzimidazole resin, and the like.

The nonlinear optical organic compound is not particularly limited as long as it is a known one, but in one molecule, an atomic group having an electron donating property (hereinafter referred to as “donor”) and an atomic group having an electron withdrawing property (hereinafter referred to as “donor”). And a molecule having a structure in which a π-electron conjugated atomic group is arranged between the donor and the acceptor. Specific examples of such molecules include Disperse Reds, Disperse Oranges, and stilbene compounds. The nonlinear optical organic compound can be introduced into the polymer material by addition to the polymer material described above or by chemical bonding to the side chain or main chain of the polymer material described above.
By orienting the dipole of the nonlinear optical organic compound dispersed in the organic electro-optic polymer material, the substrate 11 can have an electro-optic effect.

  On the substrate 11, a control electrode for modulating a light wave propagating through the optical waveguide 12 and a heater electrode 41 for adjusting a bias point are arranged. The control electrode includes a signal electrode 21 formed on one surface (front surface) of the substrate 11 and a back ground electrode 31 formed on the opposite surface (back surface). The back surface ground electrode 31 is formed between the substrate 11 and the base material 15 below the substrate 11. The signal electrode 21 and the back ground electrode 31 arranged so as to sandwich the substrate 11 form a transmission line having a microstrip line structure.

Further, on the surface of the substrate 11, surface ground electrodes 22 (1) to (4) electrically connected to the back surface ground electrode 31 through vias 24 penetrating the substrate 11 are also formed. The surface ground electrodes 22 (1) and (2) are arranged so as to sandwich the input end portion (input feedthrough) of the signal electrode 21, and the surface ground electrodes 22 (3) and (4) 21 is arranged so as to sandwich the output end portion (output feedthrough).
These electrodes can be formed by, for example, forming a base electrode pattern of Ti / Au or the like on the surface of the substrate and performing a gold plating method or the like. The surface ground electrode is also referred to as “upper ground electrode”, and the back surface ground electrode is also referred to as “lower ground electrode”.

  The signal electrode 21 includes an action section extending above the optical waveguide 12 in the same direction as the extending direction of the optical waveguide 12, a section extending from the input end of the signal electrode 21 toward the start point of the action section, and an end point of the action section. And a section extending toward the output end of the signal electrode 21. A high frequency modulation signal is input to the signal electrode 21 from an external driver element (not shown). The action section is a section in which a modulation action is exerted on a light wave propagating through the optical waveguide 12 by an electric field generated by a high-frequency modulation signal.

  The heater electrode 41 has a bias point adjustment section extending above the optical waveguide 12 in the same direction as the extending direction of the optical waveguide 12, a section extending from the input end of the heater electrode 41 toward the start point of the bias point adjustment section, And a section extending from the end point of the bias point adjustment section toward the output end of the heater electrode 41. A DC signal for bias modulation is input to the heater electrode 41 from an external DC voltage controller 42. The bias point adjustment section is an section in which a bias point adjustment action is exerted on the light wave propagating through the optical waveguide 12 by heat generation due to application of a DC signal.

  The heater electrode 41 is formed on the front surface of the substrate 11 (the same surface as the signal electrode 21), and the back surface of the substrate 11 radiates heat generated by the heater electrode 41 so as to cover the lower portion of the heater electrode 41. The heat dissipating means 52 is provided. In this example, a metal heat dissipating film formed of the same material as the back ground electrode 31 is used as the heat dissipating means 52. The back surface ground electrode 31 and the heat radiating means 52 may be formed of different metal materials, but it is more efficient to form them with the same metal material because they can be manufactured in the same process.

  The heat dissipating means 52 is formed up to a region reaching one side end (side end where the input / output ends of the signal electrode and the heater electrode are provided) along the light wave traveling direction of the optical waveguide element 10. Therefore, the heat generated from the heater electrode 41 is radiated from the side surface of the optical waveguide element 10 through the heat radiating means 52 located below the heater electrode 41. If the heat dissipation means has a sufficient heat dissipation capability, the heat dissipation means may not be formed up to a region reaching one side end along the light wave traveling direction of the optical waveguide element.

  Here, in order to efficiently dissipate heat from the side surface of the optical waveguide element 10, it is preferable to form the heat dissipating means 52 so that the amount of heat conduction increases toward the side end of the substrate 11. In this example, the width of the heat radiation means 52 in the light wave traveling direction is W1 on the side where the bias point adjustment section is present, and W2 is the width on the side where the heater electrode input / output end is located. And W2> W1. The width is continuously increased from W1 to W2. With such a structure, the heat generated from the heater electrode 41 can be efficiently radiated toward the side surface of the optical waveguide element 10. 2 shows an example in which the width of the heat radiating means is linearly expanded, the shape may be a shape in which the width is increased so as to draw a curve, or a shape in which the width is gradually increased.

  Further, in the optical waveguide element 10 of this example, the heater electrode 41 is provided for one of the two parallel waveguides extending in parallel, and the heat dissipation means 51 is the parallel waveguide provided with the heater electrode 41. While formed in the lower part, it is not formed in the lower part of other parallel waveguides. Therefore, the heat generated by the heater electrode 41 can suppress the influence on other parallel waveguides. In addition, the structure which provides a heater electrode separately with respect to each of two parallel waveguides may be sufficient, and the heat dissipation means should just be provided separately in this case. In this case, the heat dissipating means may be configured so that the heat conduction direction of one heat dissipating means is opposite to or different from the heat conduction direction of the other heat dissipating means. Further, when the heat dissipation capability of the heat dissipation means is sufficiently high, the heat dissipation means may be integrated without being provided separately.

FIG. 4A is a plan view showing an example of an optical modulator in which the optical waveguide element of FIG. 1 is housed in a housing. 4B is a cross-sectional view taken along line AA ′ in the optical modulator of FIG. 4A.
The optical waveguide element 10 shown in the figure is accommodated in a housing 80 of the optical modulator. The housing 80 further accommodates relay boards 81 and 82 on which relay signal lines for electrically connecting the control electrodes of the optical waveguide element 10 and external driver elements are formed. The relay transmission line of the relay board 81 is electrically connected to the input terminal of the control electrode by wire bonding or the like, and the relay transmission line of the relay board 82 is electrically connected to the output terminal of the control electrode by wire bonding or the like. .

  Lead pins 83 and 84 for electrically connecting the heater electrode of the optical waveguide element 10 to an external DC voltage controller are disposed on the side wall of the housing 80. The lead pin 83 is electrically connected to the input terminal of the heater electrode by wire bonding or the like, and the lead pin 88 is electrically connected to the output terminal of the heater electrode by wire bonding or the like.

  The heat radiating means 51 is connected to the heat conducting means 91 that conducts the heat from the heat radiating means 51 to the housing 80 at the portion that appears on the side surface of the optical waveguide element 10. The heat conducting means 91 is connected not only to the heat radiating means 51 but also to the inner surface (bottom surface or side surface) of the housing 80. Such a configuration enables more efficient heat dissipation. As the heat conducting means 91, for example, a sheet containing a heat dissipating filler such as ceramics or graphite, or a paint can be used. When using such a paint, it is desirable to use a thermosetting or ultraviolet curable paint.

  The heat conducting means 91 is fixed to the housing 80 and the heat radiating means 51 using a conductive adhesive. In this case, the heat radiation means 51 is grounded, but there is no particular problem. On the contrary, if the heat dissipating means 51 is completely grounded without being grounded, there is a concern about negative influence, which can be said to be a more preferable mode.

  As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described contents, and can be appropriately changed in design without departing from the gist of the present invention. Needless to say, the embodiments can be appropriately combined.

  According to the present invention, it is possible to provide an optical waveguide device capable of effectively suppressing thermal crosstalk from the bias point adjustment region to the high frequency modulation region.

DESCRIPTION OF SYMBOLS 10 Optical waveguide element 11 Board | substrate 12 Optical waveguide 21 Signal electrode 22 Surface ground electrode 24 Via 31 Back surface ground electrode 41 Heater electrode 42 DC voltage control part 51 Thermal conduction suppression means 80 Housing | casing 81,82 Relay board 83,84 Lead pin 91 Thermal conduction means

Claims (5)

In an optical waveguide device having a substrate having an electro-optic effect, an optical waveguide formed on the substrate, a control electrode for modulating a light wave propagating through the optical waveguide, and a heater electrode for adjusting a bias point ,
The control electrode includes a signal electrode formed on one surface of the substrate, and a back ground electrode formed on the surface opposite to the one surface of the substrate,
The heater electrode is formed on the one surface of the substrate;
An optical waveguide device comprising heat dissipating means for dissipating heat generated by the heater electrode below the heater electrode on the opposite surface of the substrate. The optical waveguide device according to claim 1,
The heater electrode has an input end or an output end at one side end along the light wave traveling direction of the substrate,
The heat radiating means is formed so that the amount of heat conduction increases toward the one side end of the substrate. The optical waveguide device according to claim 2, wherein
The heat radiation means is a metal, and is formed so that the width of the light wave traveling direction increases toward the one side end of the substrate. In the optical waveguide device according to any one of claims 1 to 3,
The optical waveguide includes a plurality of parallel waveguides extending in parallel,
The heater electrode is provided for any of the plurality of parallel waveguides,
The optical waveguide element, wherein the heat radiating means is formed below a parallel waveguide provided with the heater electrode, but is not formed below another parallel waveguide. In the optical waveguide device according to any one of claims 1 to 4,
An optical waveguide element, wherein the optical waveguide is made of an organic polymer material.

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