WO2025203387A1 - Optical device and optical transmission device - Google Patents

Abstract

The present invention effectively reduce the effect of heat from a circuit element on the characteristics of an optical waveguide element in an optical device in which the circuit element and the optical waveguide element are accommodated in an enclosure.　In an optical device (1), a pedestal (3), on which an optical waveguide element (2) is mounted, and a circuit element (4), which is a heat-generating body, are accommodated in a single enclosure (5). The pedestal (3) has: a first surface oriented in the direction of the circuit element (4); and a leg portion that protrudes from a fourth surface opposite a third surface on which the optical waveguide is mounted, and contacts the enclosure. The pedestal (3) has a leg portion (35) in a first region (36) that is farther away from the circuit element than a boundary position at a prescribed distance of 1/3 or more of the pedestal length from the first surface, while in a second region (37) near the circuit element from the boundary position, no leg portion is provided, or one or more leg portions are provided such that the total area of the portion in contact with the enclosure is no more than 1/2 the area of the second region.

Description

Optical device and optical transmitter

The present invention relates to an optical device and an optical transmitter.

Patent Document 1 describes an optical device in which an optical modulation element and a base on which a drive circuit element, which is a heat-generating element, are mounted within a single housing. In this optical device, the base is configured so that the area of the mounting surface on which the drive circuit element is mounted is smaller than the area of the surface that is fixed to the housing. This allows heat generated by the drive circuit element to be efficiently dissipated to the housing.

International Publication No. 2023/188366

The power consumption of a driver circuit element that drives an optical waveguide element that uses LiNbO ₃ (hereinafter referred to as LN) as a substrate is generally around a few watts (2-5 W), and if heat dissipation is insufficient, the surface temperature of the driver circuit element during operation will rise to over 100°C. For this reason, a heat dissipation path for the driver circuit element, such as the pedestal shown in the above-mentioned prior art, is provided inside the housing of the optical device that includes the driver circuit element. This reduces the surface temperature of the driver circuit element during operation to around 60°C.

However, heat traveling from the driver circuit element through the base to the bottom of the housing creates a temperature gradient in the housing and the components mounted inside, including the optical waveguide element. This temperature gradient can cause a temperature rise and/or uneven temperature distribution in the substrate of the optical waveguide element, potentially affecting the characteristics of the optical waveguide element.

In particular, optical waveguide elements such as optical modulation elements formed on approximately rectangular substrates are prone to temperature gradients in the longitudinal direction of the substrate, which can cause characteristic fluctuations such as bias point fluctuations. Furthermore, such temperature gradients change depending on the placement of various heat-generating devices within the equipment in which the optical device is mounted, as well as fluctuations over time in the environmental temperature, and can become a factor in destabilizing the operation of the optical waveguide element.

The object of the present invention is to effectively reduce the impact of heat generated by circuit elements on the characteristics of optical waveguide elements in optical devices that house heat-generating circuit elements in the same housing as optical waveguide elements.

One aspect of the present invention is an optical device having a base on which an optical waveguide element including an optical waveguide formed on a substrate is mounted, a circuit element that is a heating element, and a housing that houses the base on which the optical waveguide element is mounted and the circuit element, wherein the base has a first surface arranged inside the housing so as to face the direction of the circuit element, a second surface opposite to the first surface, a third surface on which the optical waveguide element is mounted, a fourth surface opposite to the third surface, and one or more projections that protrude from the fourth surface and contact the housing. and a plurality of legs, and on the fourth surface of the base, when the distance between the first surface and the second surface is the base length, the legs are provided in a first region farther from the circuit element than a boundary position that is a predetermined distance of at least 1/3 of the base length from the first surface toward the second surface, and in a second region closer to the circuit element than the boundary position, either no legs are provided or one or more legs are provided whose total area in contact with the housing is 1/2 or less of the area of the second region.
Another aspect of the present invention is an optical transmission apparatus comprising the optical device described above and an electronic circuit that generates an electrical signal for causing the optical device to perform a modulation operation.

In an optical device in which a heat-generating circuit element and an optical waveguide element are housed in the same housing, the present invention effectively reduces the impact of heat generated by the circuit element on the characteristics of the optical waveguide element.

FIG. 1 is a plan view showing the configuration of an optical device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the optical device shown in FIG. 1 taken along line II-II. FIG. 3 is a diagram showing an example of the configuration of an optical waveguide element. FIG. 4 is a diagram showing the configuration of the base. FIG. 5 is a diagram showing the configuration of a base according to a first modified example. FIG. 6 is a diagram showing the configuration of a base according to a second modified example. FIG. 7 is an enlarged view of the rear surface of the base according to the second modified example shown in FIG. FIG. 8 is a diagram showing the configuration of a base according to a third modified example. FIG. 9 is an enlarged view of the rear surface of the base according to the third modified example shown in FIG. FIG. 10 is a diagram showing the configuration of a base according to a fourth modified example. FIG. 11 is an enlarged view of the rear surface of the base according to the fourth modified example shown in FIG. FIG. 12 is a diagram showing the configuration of a base according to the fifth modified example. FIG. 13 is an enlarged view of the rear surface of the base according to the fifth modified example shown in FIG. FIG. 14 is a diagram showing the configuration of a base according to a sixth modified example. FIG. 15 is a diagram showing the configuration of a base according to a seventh modified example. FIG. 16 is a diagram showing the configuration of an optical transmitting apparatus according to the second embodiment of the present invention.

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

In the optical device according to the embodiments described below, a base on which an optical waveguide element is mounted and a circuit element such as a drive circuit element, which is a heating element, are housed in a single housing. The base has a first surface arranged inside the housing so as to face the heating element, and a second surface opposite the first surface, with the distance between the first and second surfaces defining the base length. The base also has a third surface on which the optical waveguide element is mounted, a fourth surface opposite the third surface, and one or more legs that protrude from the fourth surface and come into contact with the housing.

In particular, legs are provided on the fourth surface of the base in a first region farther from the circuit element than a boundary position located a predetermined distance of at least 1/3 of the length of the base from the first surface toward the second surface, and in a second region closer to the circuit element than the boundary position, either no legs are provided or one or more legs are provided whose total area in contact with the housing is 1/2 or less of the area of the second region.

This effectively prevents heat from the circuit element, which is a heat-generating body, from being transmitted from the second region of the fourth surface, which is close to the circuit element, to the optical waveguide element mounted on the third surface, effectively reducing the impact of the heat on the characteristics of the optical waveguide element.

1. First embodiment
[1.1. Optical Device Configuration]
First, an optical device 1 according to a first embodiment of the present invention will be described.
Fig. 1 is a plan view showing the configuration of an optical device 1. Fig. 2 is a cross-sectional view of the optical device 1 shown in Fig. 1 taken along the line II-II.

In the optical device 1, a base 3 on which an optical waveguide element 2 is mounted and a circuit element 4, which is a heating element, are housed inside a single housing 5. The optical waveguide element 2 is, for example, an optical modulation element, and the circuit element 4 is, for example, an element that amplifies a signal to cause the optical waveguide element 2 to perform optical modulation. The circuit element 4 is mounted on a carrier 13 and housed inside the housing 5. A plate-shaped cover (not shown) is ultimately fixed to the opening of the housing 5, hermetically sealing the interior.

The housing 5 has a signal pin 7a for inputting a high-frequency electrical signal used to modulate the optical waveguide element 2, and a signal pin 7b for inputting an electrical signal used to adjust the operating point of the optical waveguide element 2, etc.

Furthermore, the optical device 1 has an input optical fiber 8a for inputting light into the housing 5, and an output optical fiber 8b for guiding light modulated by the optical waveguide element 2 to the outside of the housing 5, both located on the same surface of the housing 5.

Here, the input optical fiber 8a and the output optical fiber 8b are fixed to the housing 5 via supports 9a and 9b, which are fixing members. An optical unit 11 is arranged between the input optical fiber 8a and the output optical fiber 8b and the optical waveguide element 2. The optical unit 11 may include a lens and a polarization combiner (both not shown).

Light input from the input optical fiber 8a is collimated by the lens 10a arranged in the support 9a, and then input to the optical waveguide element 2 via the lens in the optical unit 11.

The optical waveguide element 2 modulates the input light and outputs two modulated lights with different polarization directions. The two output modulated lights are combined into a single beam by a polarization combiner in the optical unit 11, and then focused by a lens 10b arranged in the support 9b and coupled to the output optical fiber 8b.

The housing 5 includes a relay board 6. A high-frequency electrical signal for optical modulation operation is input to the relay board 6 from signal pin 7a, and an electrical signal for adjusting the operating point in optical modulation operation and other signals are input from signal pin 7b. The output of the electrical circuit of the relay board 6 is connected to an electrode of the optical waveguide element 2, for example, via wire bonding. The optical device 1 also includes a terminator 12 with a predetermined impedance inside the housing 5. The terminator 12 is mounted on the base 3, for example, and connected to an electrode of the optical waveguide element 2 via wire bonding, for example.

Figure 3 is a plan view showing an example of the configuration of the optical waveguide element 2. The optical waveguide element 2 includes a substrate 20 and an optical waveguide 22 formed on one main surface of the substrate 20.

The planar shape of the substrate 20, i.e., the planar shape of the optical waveguide element 2, is approximately rectangular, with a first short side 21a and a second short side 21b that face each other across the element length Le, which is the longitudinal length, and a first long side 21c and a second long side 21d that face each other across the element width We and are approximately perpendicular to the first short side 21a and the second short side 21b.

Substrate 20 is an LN substrate with an electro-optic effect that has been thinned and processed to a thickness of, for example, 2 μm or less (e.g., 1 μm). For reinforcement purposes, substrate 20 can be attached to a support substrate made of, for example, glass or the like, that has the same planar shape as substrate 20.

The optical waveguide 22 formed on the principal surface of the substrate 20 is, for example, a convex optical waveguide (e.g., a rib-type optical waveguide or a ridge-type optical waveguide) formed by a convex portion extending on the substrate 20. In this embodiment, the optical waveguide element 2 is, for example, an optical modulation element configured as a DP-QPSK modulator. The optical waveguide element 2 includes two nested Mach-Zehnder optical waveguides according to conventional technology, and performs DP-QPSK modulation on the light waves input from the input optical fiber 8a.

Optical waveguide 22, which is a DP-QPSK modulator configuration including two nested Mach-Zehnder optical waveguides, includes, according to conventional technology, a bias region BE in which a bias electrode (not shown) for bias point adjustment is formed, and a modulation region ME in which a modulation electrode (not shown) through which a high-frequency electrical signal for optical modulation is passed is formed. The modulation electrode is, for example, a traveling-wave electrode that constitutes a coplanar transmission line, and is driven by circuit element 4 that constitutes the driver circuit. One end of the modulation electrode is connected to the high-frequency signal output of circuit element 4, and the other end is connected to a termination resistor that constitutes terminator 12.

The optical waveguide 22 includes a folded waveguide that folds the propagation direction of light along the longitudinal direction of the substrate 20. The optical waveguide element 2 has a light folding region TB on the side of the first short side 21a of the substrate 20, where the folded waveguide is formed. The folded waveguide is, for example, a portion formed by bending waveguides in which a total of eight arm waveguides, such as two nested Mach-Zehnder optical waveguides, fold the propagation direction of light 180 degrees. As a result, the propagation direction of light input from the light input end 23a arranged on the second short side 21b of the substrate 20 is folded in the light folding region TB, and modulated light is output from the two light output ends 23b and 23c on the second short side 21b.

In this embodiment, due to the presence of the light folding region TB, the bias region BE and the modulation region ME are formed approximately parallel to each other in the width direction perpendicular to the longitudinal direction of the substrate 20.

Fig. 4 is a diagram showing the configuration of the base 3 on which the optical waveguide element 2 is mounted. Fig. 4(a) is a plan view of the base 3 seen from the same direction as the view of the optical device 1 shown in Fig. 1, Fig. 4(b) is a side view of the base 3, and Fig. 4(c) is a rear view of the base 3. Fig. 4(d) is a right side view of the base 3 shown in Fig. 4(b).
In this embodiment, the base 3 is mounted with a terminator 12 in addition to the optical waveguide element 2 .
The base 3 is preferably made of a material having a lower thermal conductivity than the material making up the housing 5. Furthermore, the base 3 is preferably made of a material having a lower thermal conductivity than the material making up the carrier 13 on which the circuit elements 4 are mounted. For example, the housing 5 and the carrier 13 may be made of a copper-tungsten (CuW) alloy, and the base 3 may be made of Kovar.

The base 3 has a first surface 31 arranged inside the housing 5 so as to face the circuit element 4, and a second surface 32 opposite the first surface 31. The length of the base 3, or base length Lp, is the distance between the first surface 31 and the second surface 32. The optical waveguide element 2 is mounted on the base 3 so that the first short side 21a, on which the light folding region TB is located, is arranged on the first surface 31 side.

The base 3 also has a third surface 33 on which the optical waveguide element 2 is mounted, and a fourth surface 34 opposite the third surface 33.

In this embodiment, as shown in FIG. 4(c), in particular, when the region on the fourth surface 34 of the base 3 farther from the circuit element 4 than the boundary position indicated by line DL (shown as a dashed dotted line) a predetermined distance Ld of at least 1/3 of the base length Lp from the first surface 31 toward the second surface 32 is defined as the first region 36, and the region closer to the circuit element 4 than the boundary position is defined as the second region 37, legs 35 that protrude from the fourth surface 34 and come into contact with the housing 5 are provided within the first region 36, while no such legs are provided in the second region 37.

Furthermore, as shown in FIG. 4(a), in a plan view, the first surface 31 of the base 3 includes a substantially rectangular element region 38 with a length Lp equal to the length of the base and a width Wp, and a substantially rectangular extension region 39 with a length Lt and a width Wt that protrudes and extends from one long side of the element region 38 on the lower side in the figure. For example, a terminator 12 is mounted in the extension region 39. One short side on the right side in the figure of the extension region 39 and the short side on the right side of the element region 38 on which the second short side 21b of the optical waveguide element 2 is disposed are flush with each other on the second surface 32. Here, the length Lt of the extension region 39 can be less than half the base length Lp. Therefore, the distance D1 between the first surface 31 and the extension region 39 is greater than or equal to half the base length Lp.

Furthermore, legs 35 protruding from the fourth surface 34 are provided over the entire area of the fourth surface 34 corresponding to the extension area 39. The legs 35 are fixed within the housing 5 in contact with the inner bottom surface of the housing 5.

As a result, in the optical device 1, the legs 35 of the base 3 that contact the housing 5 are located within the first region 36, and as shown by the dotted arrow in Figure 2, heat generated in the circuit element 4, which is a heat-generating element, propagates to the legs 35 over a distance of at least one-third of the base length Lp. As a result, temperature increases and/or uneven temperature distribution in the base 3 caused by heat generated by the circuit element 4 are suppressed, effectively reducing the impact of the heat generation on the characteristics of the optical waveguide element 2.

In this embodiment, the legs 35 are particularly located below the extension area 39 in which the terminator 12 is mounted, and the distance D1 from the first surface 31 to the extension area 39 is at least half the base length Lp, so that temperature increases and/or uneven temperature distribution in the base 3 due to heat generated by the circuit element 4 are more effectively suppressed.

In order to effectively prevent temperature rises and/or uneven temperature distribution in the base 3 due to heat generated by the circuit elements 4, it is preferable that legs of the base 3 such as leg 35 are not provided in the second region 37 close to the circuit elements 4, which are heat-generating elements, or that if one or more legs are provided in the second region 37, the total area of those legs in contact with the housing 5 is no more than half the area of the second region 37.

Furthermore, it is preferable that the predetermined distance Ld from the first surface 31 of the line DL, which is the boundary between the first region 36 and the second region 37, be between 1/3 and 1/2 of the base length Lp. The reason why the predetermined distance Ld is preferably 1/3 or more of the base length Lp is that if the predetermined distance Ld is less than 1/3 of the base length Lp, the first region 36 will be closer to the first surface 31, increasing the heat transfer from the circuit element 4 to the optical waveguide element 2. The reason why the predetermined distance Ld is preferably 1/2 or less of the base length Lp is that if the predetermined distance Ld is more than 1/2 of the base length Lp, the area of the first region 36 will be narrower, restricting the placement of the legs 35, which could reduce the stability of the fixation of the base 3 to the housing 5.

Furthermore, the position of the line DL, which is the boundary between the first region 36 and the second region 37, may be defined as the longitudinal centerline position of the substrate 20 of the optical waveguide element 2 mounted on the third surface 33 of the base 3. For example, the leg portion 35 provided on the fourth surface 34 can be provided in the first region 36 defined by the centerline position, i.e., the region farther from the circuit element 4 than the centerline position. In this case, too, the heat transfer path from the circuit element 4 to the optical waveguide element 2 has a distance of at least half the element length Le of the optical waveguide element 2, thereby preventing the heat generated in the circuit element 4 from being transferred to the optical waveguide element 2.

Furthermore, the legs 35 provided on the fourth surface 34 of the base 3 are preferably provided on a portion of the fourth surface 34 other than the area corresponding to the bias region BE and/or modulation region ME of the optical waveguide element 2 mounted on the third surface 33. This makes it possible to prevent heat from being transferred via the legs to the bias region BE and/or modulation region ME of the optical waveguide element 2, whose characteristics are susceptible to changes in response to temperature fluctuations or uneven temperature distribution on the substrate 20.

Modified examples of the base 3 that can be used in the optical device 1 will be described below.
[1.2. First Modification]
First, a description will be given of a base 3A, which is a first modified example of the base 3. The base 3A can be used in the optical device 1 in place of the base 3.
Fig. 5 is a diagram showing the configuration of the base 3A, and corresponds to Fig. 4 showing the configuration of the base 3. In Fig. 5, components that are the same as the components of the base 3 shown in Fig. 4 are designated by the same reference numerals as in Fig. 4, and the explanation of Fig. 4 above is incorporated herein.

(a) in Figure 5 is a plan view of the base 3A viewed from the same direction as the view of the optical device 1 shown in Figure 1, (b) in Figure 5 is a side view of the base 3A, and (c) in Figure 5 is a rear view of the base 3A. (d) in Figure 5 is a right side view of the base 3A shown in (b) in Figure 5.

Pedestal 3A has a similar configuration to pedestal 3 shown in Figure 4, but differs in that it has leg 35a instead of leg 35 (see Figure 5(c)). Leg 35a extends from the region of first region 36 of fourth surface 34 that corresponds to extension region 39 of third surface 33 and further to part of the region that corresponds to element region 38. This improves the connection strength of pedestal 3A to housing 5 compared to pedestal 3.

However, as shown in Figure 4(c), it is preferable that the legs 35a are arranged so that they do not extend into the areas corresponding to the modulation region ME and bias region BE of the optical waveguide element 2 mounted on the third surface 33. This makes it possible to prevent heat from being transferred via the legs 35a to the bias region BE and/or modulation region ME, whose characteristics are susceptible to changes in response to temperature fluctuations or uneven temperature distribution on the substrate 20.

[1.3. Second Modification]
Next, a description will be given of a base 3B, which is a second modified example of the base 3. The base 3B can be used in the optical device 1 in place of the base 3.
Fig. 6 is a diagram showing the configuration of base 3B, and corresponds to Fig. 5 showing the configuration of base 3A. In Fig. 6, components that are the same as those of base 3A shown in Fig. 5 are designated by the same reference numerals as those in Fig. 5, and the description of Fig. 5 above is applicable.

(a) of Figure 6 is a plan view of the base 3B viewed from the same direction as the view of the optical device 1 shown in Figure 1, (b) of Figure 6 is a side view of the base 3B, and (c) of Figure 6 is a rear view of the base 3B. (d) of Figure 6 is a right side view of the base 3B shown in (b) of Figure 6. (c) of Figure 6 is an enlarged detailed view of the rear view of the base 3B shown in (c) of Figure 6.

Pedestal 3B has a similar configuration to pedestal 3A shown in Figure 5, but differs in that it has leg 35b in addition to leg 35a (see Figure 6(c) and Figure 7). As shown in Figure 7, on the fourth surface 34 of pedestal 3B, a first portion P1 can be defined, which is an area outside the area corresponding to the modulation region ME of the optical waveguide element 2 mounted on the third surface 33; a second portion P2 corresponding to the area between the modulation region ME and the bias region BE; and a third portion P3 outside the area corresponding to the bias region BE.

Furthermore, the base 3B has individual legs 35a and 35b provided on the first portion P1 and the third portion P3, respectively. In this way, the base 3B does not have legs on the portions of the fourth surface 34 that correspond to the modulation region ME and bias region BE of the optical waveguide element 2, which prevents heat from being transferred from the circuit element 4 to the bias region BE and/or modulation region ME, whose characteristics are sensitive to temperature fluctuations or uneven temperature distribution on the substrate 20.

Furthermore, the base 3B may also have individual legs on the second portion P2 of the fourth surface 34. This can further improve the stability of the base 3B fixed to the housing 5 while suppressing the transfer of heat from the circuit element 4 to the bias region BE and/or modulation region ME.

Furthermore, in the base 3B, the legs 35a and 35b may extend toward the first surface 31 along the first portion P1 and the third portion P3, respectively. The extension range may be to a position farther from the first surface 31 than the light turning region TB of the optical waveguide element 2, or may be to a position closer to the first surface 31 than the light turning region TB.

[1.4. Third Modification]
Next, a description will be given of a base 3C, which is a third modification of the base 3. The base 3C can be used in the optical device 1 in place of the base 3.
Fig. 8 is a diagram showing the configuration of the base 3C, and corresponds to Fig. 6 showing the configuration of the base 3B. Fig. 8(a) is a plan view of the base 3C seen from the same direction as the view of the optical device 1 shown in Fig. 1, Fig. 8(b) is a side view of the base 3C, and Fig. 8(c) is a rear view of the base 3C. Fig. 8(d) is a right side view of the base 3C shown in Fig. 8(b). Fig. 9 is a detailed enlarged view of the rear view of the base 3C shown in Fig. 8(c).

In Figures 8 and 9, components that are the same as those of the base 3B shown in Figures 6 and 7, respectively, are indicated by the same reference numerals as in Figures 6 and 7, and the explanations for Figures 6 and 7 above are incorporated herein.

Pedestal 3C has a similar configuration to pedestal 3B shown in Figure 5, but differs in that it has one leg 35c instead of two legs 35a and 35b. As shown in Figure 9, leg 35c is configured as a single leg in which the portions extending to the first portion P1, second portion P2, and third portion P3 of fourth surface 34 are connected by a portion extending along second surface 32. Furthermore, the portions of leg 35c that extend along the first portion P1, second portion P2, and third portion P3 of fourth surface 34 do not extend to a position corresponding to the light folding region TB of the optical waveguide element 2, but instead extend within the range of first region 36.

In the base 3C, the leg 35c is configured as a single leg that includes portions extending to the first portion P1, the second portion P2, and the third portion P3 of the fourth surface 34. This prevents heat from being transferred from the circuit element 4 to the bias region BE and/or the modulation region ME, while improving the stability of the fixation of the base 3C to the housing 5 compared to the base 3B shown in Figures 6 and 7.

[1.5. Fourth Modification]
Next, a description will be given of a base 3D, which is a fourth modification of the base 3. The base 3D can be used in the optical device 1 in place of the base 3.
Fig. 10 is a diagram showing the configuration of the base 3D, and corresponds to Fig. 8 showing the configuration of the base 3C. Fig. 10(a) is a plan view of the base 3D seen from the same direction as the view of the optical device 1 shown in Fig. 1, Fig. 10(b) is a side view of the base 3D, and Fig. 10(c) is a rear view of the base 3D. Fig. 10(d) is a right side view of the base 3D shown in Fig. 10(b). Fig. 11 is a detailed enlarged view of the rear view of the base 3D shown in Fig. 10(c).

In Figures 10 and 11, components that are the same as those of the base 3C shown in Figures 8 and 9, respectively, are indicated by the same reference numerals as in Figures 8 and 9, and the explanations for Figures 8 and 9 above are incorporated herein.

Pedestal 3D has a similar configuration to pedestal 3C shown in Figures 8 and 9, but differs in that it has leg 35d instead of leg 35c. Leg 35d has a similar configuration to leg 35c, but the length of the portion extending along the first portion P1, second portion P2, and third portion P3 of fourth surface 34 differs from that of leg 35c. That is, the portion of leg 35d shown in Figure 11 that extends along the first portion P1, second portion P2, and third portion P3 of fourth surface 34 extends into the range of second region 37 and further into a certain range of light folding region TB of the optical waveguide element 2.

As a result, the base 3D can suppress the transfer of heat from the circuit element 4 to the bias region BE and/or modulation region ME, while further improving the stability of the base 3D when fixed to the housing 5 compared to the base 3C shown in Figures 8 and 9.

Here, it is preferable that the total area of the portions of the leg 35d that extend along the first portion P1, the second portion P2, and the third portion P3 of the fourth surface 34 and that come into contact with the housing 5 within the second region 37 is configured to be half or less of the area of the second region 37.

This effectively suppresses heat transfer from the circuit element 4 to the optical waveguide element 2 via the portion of the leg 35d that extends into the second region 37.

[1.6. Fifth Modification]
Next, a description will be given of a base 3E, which is a fifth modification of the base 3. The base 3E can be used in the optical device 1 in place of the base 3.
Fig. 12 is a diagram showing the configuration of the base 3E, and corresponds to Fig. 10 showing the configuration of the base 3D. Fig. 12(a) is a plan view of the base 3E seen from the same direction as the view of the optical device 1 shown in Fig. 1, Fig. 12(b) is a side view of the base 3E, and Fig. 12(c) is a rear view of the base 3E. Fig. 12(d) is a right side view of the base 3E shown in Fig. 12(b). Fig. 13 is a detailed enlarged view of the rear view of the base 3E shown in Fig. 12(c).

In Figures 12 and 13, components that are the same as those of the base 3D shown in Figures 10 and 11, respectively, are indicated by the same reference numerals as in Figures 10 and 11, and the explanations for Figures 10 and 11 above are incorporated herein.

Pedestal 3E has a similar configuration to pedestal 3D shown in Figures 10 and 11, but differs in that it has leg 35e instead of leg 35d. Leg 35e has a similar configuration to leg 35d, but the length of the portion extending along the first portion P1, second portion P2, and third portion P3 of fourth surface 34 differs from that of leg 35d. That is, the portion of leg 35e shown in Figure 13 that extends along the first portion P1, second portion P2, and third portion P3 of fourth surface 34 extends into the second region 37 and further extends to the first surface 31 of pedestal 3E.

As a result, the base 3E can suppress the transfer of heat from the circuit element 4 to the bias region BE and/or modulation region ME, while further improving the stability of the base 3E fixed to the housing 5 compared to the base 3D shown in Figures 10 and 11.

Here, it is preferable that the total area of the portions of leg 35e that extend along the first portion P1, second portion P2, and third portion P3 of fourth surface 34 and come into contact with housing 5 within second region 37 is configured to be half or less of the area of second region 37, similar to leg 35d.

This effectively suppresses heat transfer from the circuit element 4 to the optical waveguide element 2 via the portion of the leg 35e that extends into the second region 37.

[1.7. Sixth Modification]
Next, a description will be given of a base 3F, which is a sixth modified example of the base 3. The base 3F can be used in the optical device 1 in place of the base 3.
Fig. 14 is a diagram showing the configuration of the base 3F, and corresponds to Fig. 4 showing the configuration of the base 3. Fig. 14(a) is a plan view of the base 3F seen from the same direction as the view of the optical device 1 shown in Fig. 1, Fig. 14(b) is a side view of the base 3F, and Fig. 14(c) is a rear view of the base 3F. Fig. 14(d) is a right side view of the base 3F shown in Fig. 14(b).

In Figure 14, components that are the same as those of the base 3A shown in Figure 4 are indicated by the same reference numerals as in Figure 4, and the explanation for Figure 4 above is applicable.

Pedestal 3F has a similar configuration to pedestal 3 shown in Figure 4, but differs in that it has extension region 39f instead of extension region 39. Extension region 39f differs from extension region 39 in size in the pedestal length direction when viewed from above on first surface 31; it protrudes from the illustrated underside of element region 38, extends a length Lp that is the same as the pedestal length, and has a width Wf. Furthermore, pedestal 3F has legs 35f protruding from fourth surface 34 over the entire area of fourth surface 34 that corresponds to extension region 39f, instead of legs 35.

As a result, the base 3F can prevent heat from being transferred from the circuit element 4 to the bias region BE and/or modulation region ME. Furthermore, the contact area of the legs 35f of the base 3F with the housing 5 can be made larger than the contact area of the legs 35 of the base 3 with the housing 5, so the base 3F can be fixed to the housing 5 with improved stability compared to the base 3.

Here, it is preferable that the area of the portion of the leg 35f that contacts the housing 5 within the range of the second region 37 is configured to be equal to or less than half the area of the second region 37. This makes it possible to effectively suppress the transfer of heat from the circuit element 4 to the optical waveguide element 2 via the portion of the leg 35f that extends into the second region 37.
[1.8. Seventh Modification]
Next, a description will be given of a base 3G, which is a seventh modification of the base 3. The base 3G can be used in the optical device 1 in place of the base 3.
Fig. 15 is a diagram showing the configuration of the base 3G, and corresponds to Fig. 4 showing the configuration of the base 3. Fig. 15(a) is a plan view of the base 3G seen from the same direction as the view of the optical device 1 shown in Fig. 1, Fig. 15(b) is a side view of the base 3G, and Fig. 15(c) is a rear view of the base 3G. Fig. 15(d) is a right side view of the base 3G shown in Fig. 15(b).

In Figure 15, components that are the same as those of the base 3 shown in Figure 4 are indicated by the same reference numerals as in Figure 4, and the explanation for Figure 4 above is incorporated herein.

The base 3G has a similar configuration to the base 3 shown in Figure 4, but in the region of the fourth surface 34 corresponding to the element region 38 of the third surface 33, a thick portion 40 is formed in a substantially rectangular area extending from the second surface 32, which is thicker than the other portions excluding the leg portions 35.

This allows the base 3G to increase the rigidity of the element region 38 and improve the stability of the optical characteristics of the optical waveguide element 2.

[2. Second embodiment]
Next, a second embodiment of the present invention will be described. This embodiment is an optical transmitting device 50 equipped with the optical device 1 according to the first embodiment. FIG. 16 is a diagram showing the configuration of the optical transmitting device 50 according to this embodiment. This optical transmitting device 50 has the optical device 1, a light source 51 that inputs light to the optical device 1, and a modulation signal generating unit 52. Note that the optical device 1 used in the optical transmitting device 50 can use any of the bases 3A to 3G according to any of the above-mentioned modified examples in place of the base 3.

The modulation signal generator 52 is an electronic circuit that generates an electrical signal to cause the optical device 1 to perform a modulation operation. Based on externally provided transmission data, it generates a modulation signal, which is a high-frequency signal that causes the optical device 1 to perform an optical modulation operation in accordance with the modulation data, and inputs this signal to the signal pin 7a of the optical device 1.

The optical transmitter 50 uses an optical device 1 that can achieve stable optical characteristics while housing a circuit element 4, which is a heat-generating element, and an optical waveguide element 2 in the same housing, thereby achieving stable and excellent optical transmission.

The present invention is not limited to the configuration of the above embodiment, and can be implemented in various forms without departing from the spirit of the invention.

3. Configurations supported by the above embodiment
The above-described embodiment and its modifications support the following configurations.

(Configuration 1) An optical device having a base on which an optical waveguide element including an optical waveguide formed on a substrate is mounted, a circuit element that is a heating element, and a housing that houses the base on which the optical waveguide element is mounted and the circuit element, wherein the base has a first surface arranged inside the housing so as to face the direction of the circuit element, a second surface opposite to the first surface, a third surface on which the optical waveguide element is mounted, a fourth surface opposite to the third surface, and one or more legs that protrude from the fourth surface and contact the housing. and, when the distance between the first surface and the second surface is defined as a base length, the legs are provided on the fourth surface of the base in a first region farther from the circuit element than a boundary position that is a predetermined distance of at least 1/3 of the base length from the first surface toward the second surface, and in a second region closer to the circuit element than the boundary position, either the legs are not provided or one or more legs are provided whose total area of the portion in contact with the housing is 1/2 or less of the area of the second region.
According to the optical device of configuration 1, the base on which the optical waveguide element is mounted has no legs that come into contact with the housing within a predetermined distance from the circuit element, which is a heat-generating element, or has legs with a limited contact area with the housing, thereby effectively reducing the effect of heat generated by the circuit element on the characteristics of the optical waveguide element.

(Configuration 2) The optical device according to configuration 1, wherein the predetermined distance is equal to or less than half the length of the base.
According to the optical device of configuration 2, the range of the base on which the optical waveguide element is mounted, in which the configuration of the legs that come into contact with the housing is restricted, is limited to less than half the length of the base, so that the base can be stably fixed to the housing by the legs provided in other ranges.

(Configuration 3) The optical device according to Configuration 1 or 2, wherein the optical waveguide element is an optical modulation element that performs optical modulation operation and includes a Mach-Zehnder optical waveguide in the optical waveguide, and includes, on a substrate on which the optical waveguide is formed, a bias electrode that adjusts an operating point of the optical modulation operation, and a modulation electrode to which a high-frequency electrical signal that modulates light is passed, and the leg portion is provided in a portion of the fourth surface other than a region corresponding to a bias region in which the bias electrode of the optical waveguide element is formed.
According to the optical device of configuration 3, even when an optical modulation element including a Mach-Zehnder optical waveguide is used as the optical waveguide element, it is possible to suppress the heat from being transmitted through the legs to the bias region whose characteristics are susceptible to changes in sensitivity to temperature fluctuations or non-uniformity in temperature distribution of the substrate on which the optical waveguide is formed.

(Configuration 4) The optical device according to any one of configurations 1 to 3, wherein the optical waveguide element is an optical modulation element that performs optical modulation operation and includes a Mach-Zehnder optical waveguide in the optical waveguide, and includes, on a substrate on which the optical waveguide is formed, a bias electrode that adjusts an operating point of the optical modulation operation, and a modulation electrode to which a high-frequency electrical signal that modulates light is passed, and the leg portion is provided in a portion of the fourth surface other than a region corresponding to a modulation region in which the modulation electrode of the optical waveguide element is formed.
According to the optical device of configuration 3, even when an optical modulation element including a Mach-Zehnder optical waveguide is used as the optical waveguide element, it is possible to suppress the heat from being transmitted through the legs to the modulation region whose characteristics are susceptible to changes in sensitivity to temperature fluctuations or uneven temperature distribution in the substrate on which the optical waveguide is formed.

(Configuration 5) The optical device described in Configuration 3 or 4, wherein the substrate of the optical waveguide element is approximately rectangular in plan view, the optical waveguide includes a folded waveguide that folds the propagation direction of light along the longitudinal direction of the substrate, a bias region of the substrate in which the bias electrode of the optical waveguide element is formed and a modulation region in which the modulation electrode is formed are formed approximately parallel to each other in a width direction perpendicular to the longitudinal direction of the substrate, and the leg portions are individually formed in one or more of a first portion that is a region of the fourth surface outside a region corresponding to the modulation region, a second portion that corresponds to a region between the modulation region and the bias region, and a third portion that is outside the region corresponding to the bias region, or are formed as a single leg portion including a portion extending to one or more of the first portion, the second portion, and the third portion.
According to the optical device of configuration 5, it is possible to improve the stability of fixing the base to the housing while suppressing the transfer of heat from the circuit elements to the bias region and modulation region, whose characteristics are susceptible to changes in temperature or uneven temperature distribution of the substrate on which the optical waveguide is formed.

(Configuration 6) The optical device described in Configuration 5, wherein the optical waveguide element is mounted on the base so that the short side of the substrate on which the folded waveguide is formed is arranged on the side of the first surface, and the leg portion extends along the fourth surface in a direction from the second surface to the first surface, in a range that does not include an area of the substrate corresponding to the area on which the folded waveguide is formed.
According to the optical device of configuration 6, the extension range of the legs is limited to a position farther from the circuit element than the area in which the folded waveguide is formed, thereby effectively suppressing heat transfer from the circuit element to the optical waveguide element.

(Configuration 7) The optical device described in Configuration 5, wherein the optical waveguide element is mounted on the base so that the short side of the substrate on which the folded waveguide is formed is arranged on the side of the first surface, and the leg portion extends along the fourth surface in a direction from the second surface to the first surface, over a range including the region of the substrate on which the folded waveguide is formed.
According to the optical device of configuration 7, the extension range of the legs is expanded to the area where the folded waveguide is formed, thereby ensuring a large contact area between the legs and the housing within a range that can suppress the effect of heat transferred from the circuit element to the optical waveguide element, thereby increasing the stability of the fixation of the base to the housing.

(Configuration 8) An optical device described in Configuration 5, wherein the leg portion is provided in a region of the fourth surface that is farther from the circuit element than a position corresponding to the longitudinal center position of the substrate of the optical waveguide element, along the direction from the second surface to the first surface.
According to the optical device of configuration 8, the extension range of the legs is set in an area farther from the circuit element than the position corresponding to the longitudinal center position of the substrate of the optical waveguide element, so that the influence of heat transferred from the circuit element to the optical waveguide element can be effectively suppressed.

(Configuration 9) An optical device described in any one of configurations 1 to 8, wherein the base has, in a planar view, an approximately rectangular element region on which the optical waveguide element is mounted, and an approximately rectangular extension region that extends and protrudes from one long side of the element region.
According to the optical device of configuration 9, legs can be provided at the bottom of the extension region extending from the element region in which the optical waveguide element is mounted, thereby effectively suppressing heat transfer from the circuit element to the optical waveguide element.

(Configuration 10) The optical device according to any one of configurations 1 to 9, wherein the base is made of a material having a lower thermal conductivity than the material constituting the housing.
According to the optical device of configuration 10, the thermal resistance of the base can be increased, and the heat transferred from the circuit element to the optical waveguide element can be effectively reduced.

(Configuration 11) The optical device according to any one of configurations 1 to 10, wherein the optical waveguide element is an optical modulation element.
According to the optical device of configuration 11, it is possible to suppress the influence of heat generated by the circuit elements, which are heat generating bodies mounted inside the housing, and to realize an optical modulation device having stable optical modulation characteristics.

(Configuration 12) An optical transmitter comprising: the optical device according to configuration 11; and an electronic circuit that generates an electrical signal for causing the optical device to perform a modulation operation.
According to the optical transmission device of configuration 12, an optical device is used that can realize stable optical characteristics while accommodating a circuit element and an optical waveguide element, which are heat-generating bodies, in the same housing, thereby realizing stable and good optical transmission.

REFERENCE SIGNS LIST 1...optical device, 2...optical waveguide element, 3, 3A, 3B, 3C, 3D, 3E, 3F, 3G...base, 4...circuit element, 5...housing, 6...relay board, 7a, 7b...signal pin, 8a...input optical fiber, 8b...output optical fiber, 9a, 9b...support, 10a, 10b...lens, 11...optical unit, 12...terminator, 13...carrier, 20...substrate, 21a...first short side, 21b...second short side, 21 c...first long side, 21d...second long side, 22...optical waveguide, 23a...optical input end, 23b, 23c...optical output end, 31...first surface, 32...second surface, 33...third surface, 34...fourth surface, 35, 35a, 35b , 35c, 35d, 35e, 35f...leg portion, 36...first region, 37...second region, 38...element region, 39...extension region, 40...thick part, 50...optical transmitter, 51...light source, 52...modulated signal generation section.

Claims (12)

a base on which an optical waveguide element including an optical waveguide formed on a substrate is mounted;
a circuit element that is a heating element;
a housing that houses the base on which the optical waveguide element is mounted and the circuit element;
An optical device having
The base is
a first surface disposed inside the housing so as to face the circuit element and a second surface opposed to the first surface;
a third surface on which the optical waveguide element is mounted, and a fourth surface opposite to the third surface;
one or more legs that protrude from the fourth surface and contact the housing;
and
The fourth surface of the base has
When the distance between the first surface and the second surface is defined as a base length,
the leg portion is provided in a first region on a side farther from the circuit element than a boundary position that is a predetermined distance of at least one-third of the length of the base from the first surface toward the second surface,
In the second region closer to the circuit element than the boundary position, the leg portion is not provided, or one or more legs are provided, the total area of the parts contacting the housing being 1/2 or less of the area of the second region.
Optical devices. The predetermined distance is equal to or less than half the length of the base.
The optical device of claim 1 . The optical waveguide element is an optical modulation element that performs optical modulation operation and includes a Mach-Zehnder optical waveguide in the optical waveguide, and includes, on a substrate on which the optical waveguide is formed, a bias electrode that adjusts an operating point of the optical modulation operation, and a modulation electrode through which a high-frequency electrical signal that modulates light is passed,
the leg portion is provided on the fourth surface in a portion other than a region corresponding to a bias region in which the bias electrode of the optical waveguide element is formed.
The optical device of claim 1 . The optical waveguide element is an optical modulation element that performs optical modulation operation and includes a Mach-Zehnder optical waveguide in the optical waveguide, and includes, on a substrate on which the optical waveguide is formed, a bias electrode that adjusts an operating point of the optical modulation operation, and a modulation electrode through which a high-frequency electrical signal that modulates light is passed,
the leg portion is provided on the fourth surface in a portion other than a region corresponding to a modulation region in which the modulation electrode of the optical waveguide element is formed.
The optical device of claim 1 . the substrate of the optical waveguide element is substantially rectangular in plan view,
the optical waveguide includes a folded waveguide that folds the propagation direction of light along the longitudinal direction of the substrate,
a bias region of the substrate in which the bias electrode of the optical waveguide element is formed and a modulation region in which the modulation electrode is formed are formed substantially parallel to each other in a width direction perpendicular to a longitudinal direction of the substrate,
The leg portion is provided on the fourth surface.
The first portion is formed individually in one or more of a first portion which is an area outside the area corresponding to the modulation area, a second portion which is an area between the modulation area and the bias area, and a third portion which is outside the area corresponding to the bias area, or the first portion is formed as a leg portion including a portion which extends to one or more of the first portion, the second portion, and the third portion.
4. The optical device according to claim 3. the optical waveguide element is mounted on the base so that a short side of the substrate on which the folded waveguide is formed is disposed on the first surface side;
The leg portion is provided on the fourth surface.
extending in a direction from the second surface toward the first surface in a range that does not include a region of the substrate corresponding to a region in which the folded waveguide is formed;
6. The optical device according to claim 5. the optical waveguide element is mounted on the base so that a short side of the substrate on which the folded waveguide is formed is disposed on the first surface side;
The leg portion is provided on the fourth surface.
extending in a direction from the second surface toward the first surface to a range including a region of the substrate where the folded waveguide is formed;
6. The optical device according to claim 5. The leg portion is provided on the fourth surface.
the optical waveguide element is provided in a region farther from the circuit element than a position corresponding to a center position of the substrate in a longitudinal direction of the optical waveguide element, along a direction from the second surface toward the first surface;
6. The optical device according to claim 5. the base has, in a plan view, a substantially rectangular element region on which the optical waveguide element is mounted, and a substantially rectangular extension region that extends and protrudes from one long side of the element region.
The optical device of claim 1 . the base is made of a material having a lower thermal conductivity than a material constituting the housing;
The optical device of claim 1 . The optical device according to claim 1 , wherein the optical waveguide element is an optical modulation element. The optical device of claim 11;
an electronic circuit for generating an electrical signal for causing the optical device to perform a modulation operation;
An optical transmitting device comprising: