Optical module

Abstract

In order to make it possible to efficiently transmit heat to a ring resonator, this optical module comprises: a first substrate (30); a second substrate (40) that is stacked on the first substrate (30); a ring resonator (10) that has an annular optical waveguide and is attached to the first substrate (30); a heater (20) that is provided inside a first region (R1) of which the outer periphery is the optical waveguide when viewed through the first substrate (30) from a direction perpendicular to the first substrate (30), the heater (20) being provided inside the first substrate (30) and heating the ring resonator (10); and a gap (50) that is located between the first substrate (30) and the second substrate (40) and is formed so that the first substrate (30) and the second substrate (40) are spaced away from each other within the first region (R1).

Description

Optical Module

[0001] The present invention relates to, for example, an optical module including a heater and a ring resonator.

[0002] In optical communications, optical waveguide ring resonators (sometimes simply called ring resonators) are used as optical filters to process light. Optical waveguide ring resonators are compact and can achieve periodic transmission wavelength characteristics, so they are widely used in wavelength tunable filters, optical switches, and modulators. The transmission wavelength of an optical waveguide ring resonator is determined by the ring length and the refractive index of the waveguide, and wavelength tunability can be achieved by temperature control using a microheater loaded on the optical waveguide.

[0003] Patent Document 1 discloses, for example, a heater (microheater) provided in a ring resonator structure, and Patent Document 2 discloses a film heater (microheater) provided along a wavelength-tunable ring-shaped waveguide.

[0004] JP 2022-061930 A JP 2006-245344 A

[0005] However, the use of a microheater poses a problem of high power consumption. For example, in Patent Document 1, a ring resonator structure and an SOI (Silicon On Insulator) substrate are stacked, which results in a structure in which heat from the heater is easily transferred to the SOI substrate. Therefore, according to the technology described in Patent Document 1, part of the heat from the heater is transferred to the SOI substrate, and the heat from the heater cannot be efficiently transferred to the ring resonator structure.

[0006] In view of the above-mentioned problems, an object of the present invention is to enable efficient transfer of heat to a ring resonator.

[0007] The present invention is an optical module comprising: a first substrate; a second substrate laminated on the first substrate; a ring resonator having a ring-shaped optical waveguide and attached to the first substrate; a heater provided inside the first substrate in a first region having the optical waveguide as its outer periphery when light passes through the first substrate in a direction perpendicular to the surface of the first substrate, the heater heating the ring resonator; and a gap located between the first substrate and the second substrate, formed to separate the first substrate from the second substrate within the first region.

[0008] According to the present invention, it is possible to provide an optical module that efficiently transfers heat from a heater to a ring resonator.

[0009] FIG. 1 is a top view showing a configuration example of an optical module according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view for explaining details of the optical module according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view for explaining details of the optical module according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view for explaining details of the optical module according to the first embodiment of the present invention. FIG. 5 is a cross-sectional view for explaining details of the optical module according to the first embodiment of the present invention. FIG. 6 is a cross-sectional view for explaining details of the optical module according to the first embodiment of the present invention. FIG. 7 is a diagram showing a modified example of the optical module according to the first embodiment of the present invention. FIG. 8 is a diagram showing a modified example of the optical module according to the first embodiment of the present invention. FIG. 9 is a top view showing a configuration example of an optical module according to a second embodiment of the present invention. FIG. 10 is a cross-sectional view for explaining details of the optical module according to the second embodiment of the present invention.

[0010] First Embodiment An optical module 1 according to a first embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view showing an example of the configuration of the optical module 1. Fig. 2 is a cross-sectional view of the optical module 1. Specifically, Fig. 2 is a cross-sectional view of the optical module 1 taken along line AA' shown in Fig. 1.

[0011] 1, the optical module 1 includes a ring resonator 10, a heater 20, a first substrate 30, and a gap 50. Also, as shown in FIG. 2, the optical module 1 includes a ring resonator 10, a heater 20, a first substrate 30, a second substrate 40, and a gap 50.

[0012] As shown in Fig. 1, ring resonator 10 has at least a ring-shaped optical waveguide 11. Light is incident on ring-shaped optical waveguide 11 included in ring resonator 10, and only light of a certain wavelength of the incident light is output from ring-shaped optical waveguide 11. The wavelength of the output light is determined by the length of ring-shaped optical waveguide 11 and the refractive index of the optical waveguide. Although not shown in Fig. 1, ring resonator 10 may further include a waveguide that guides light to enter ring-shaped optical waveguide 11 and a waveguide that guides light output from ring-shaped optical waveguide 11 to another optical element.

[0013] As shown in Fig. 1, the heater 20 is provided inside the ring-shaped optical waveguide 11 included in the ring resonator 10. Specifically, the heater 20 is provided inside the first substrate 30, in a first region whose outer periphery is the ring-shaped optical waveguide 11 when light passes through the first substrate 30 in a direction perpendicular to the surface of the first substrate 30. As shown in Fig. 2, the heater 20 is disposed at the same height as the ring resonator 10 in the direction perpendicular to the surface of the first substrate 30 (the thickness direction of the first substrate 30 (the up-down direction on the paper surface of Fig. 2)). The heights of the heater 20 and the ring resonator 10 may be different from each other.

[0014] The position of the heater 20 will be described using FIGS. 3 and 4 . FIG. 3 is a diagram in which a first region R1 is added by diagonal lines to FIG. 1 . FIG. 4 is a diagram in which a three-dimensional region corresponding to the first region R1 among the first substrate 30 and the second substrate 40 is added by diagonal lines to FIG. 2 . The three-dimensional region corresponding to the first region R1 refers to the region where the first substrate 30 and the second substrate 40 overlap with a figure obtained by extending the first region R1 in a direction perpendicular to the surface of the first substrate 30. As shown in FIG. 3 , the outer periphery of the first region R1 is the shape of the ring-shaped optical waveguide 11 when light passes through the first substrate 30 in a direction perpendicular to the surface of the first substrate 30. Note that in the example of FIG. 3 , the inner periphery of the ring-shaped optical waveguide 11 is the outer periphery of the first region R1, but the outer periphery of the ring-shaped optical waveguide may also be the outer periphery of the first region R1.

[0015] 4, the three-dimensional region corresponding to the first region R1 has a columnar shape whose bottom surface corresponds to the shape of the ring-shaped optical waveguide 11 when light passes through the first substrate 30 from a direction perpendicular to the surface of the first substrate 30. In the example of FIG. 4, the three-dimensional region corresponding to the first region R1 is a region sandwiched between a portion of one bottom surface of the first substrate 30 (the upper surface in FIG. 4) and a portion of the other bottom surface of the first substrate 30 (the lower surface in FIG. 4). That is, in the examples shown in FIGS. 1, 2, 3, and 4, the three-dimensional region corresponding to the first region R1 has a columnar shape whose bottom surface corresponds to each of the portions of the two bottom surfaces of the first substrate 30 that have the shape of the ring-shaped optical waveguide 11 as their outer periphery.

[0016] 2 and 4, the heater 20 is disposed so that the distance from the bottom surface of the first substrate 30 (e.g., the top surface in FIGS. 2 and 4) to the annular optical waveguide 11 is the same as the distance from the bottom surface of the first substrate 30 (e.g., the top surface in FIGS. 2 and 4) to the annular optical waveguide 11. However, the annular optical waveguide 11 and the heater 20 may be disposed so that these distances are different.

[0017] The heater 20 generates heat in response to power input from a drive circuit (not shown). As a result, the heater 20 heats the annular optical waveguide 11. Specifically, the heater 20 heats the first substrate 30 and the annular optical waveguide 11. In the examples of Figures 1 and 3, the shape of the surface of the heater 20 when light passes through the first substrate 30 in a direction perpendicular to the surface of the first substrate 30 is rectangular, but it may also be a polygon with a shape greater than a rectangle, an arc, a circle, or an ellipse.

[0018] Preferably, the heater 20 is disposed at a position including the center of the first region having the optical waveguide 11 as its outer periphery. As shown in Fig. 3, the heater 20 is disposed at the center of the shaded region indicating the first region R1. More specifically, the heater 20 is disposed within the first substrate 30 on a straight line from the center of one bottom surface of the first region R1 to the center of the other bottom surface. Note that the heater 20 does not necessarily have to be disposed at a position including the center of the first region.

[0019] The first substrate 30 is a plate-shaped substrate made of, for example, at least quartz glass. At least the ring resonator 10 and the heater 20 are attached to the first substrate 30. An optical waveguide other than the ring-shaped optical waveguide 11 and electronic devices may also be attached to the first substrate 30. The first substrate 30 is stacked on the second substrate 40 in a first direction. In this description, the first direction refers to the up-down direction indicated by the arrow A1 in FIGS. 2 and 4 .

[0020] The second substrate 40 is a plate-shaped substrate containing at least silicon, for example. The second substrate 40 is stacked in a first direction on the first substrate 30. The second substrate 40 also has a hole 41. The hole 41 is formed in a surface of the second substrate 40 that contacts the first substrate 30. As shown in FIGS. 2 and 4 , the second substrate 40 is bonded to the first substrate 30 via a region of the surface of the second substrate 40 that faces the first substrate 30, other than the region where the hole 41 is provided.

[0021] The void 50 is the space inside a hole provided on the surface of the second substrate 40 facing the first substrate 30. The void 50 is formed so as to include at least a region of the first region R1 that is located between the first substrate 30 and the second substrate 40 (a second region R2 described below). The void 50 is filled with, for example, argon. Details of the void 50 will be described using FIGS. 5 and 6 .

[0022] Fig. 5 shows a part of the three-dimensional region corresponding to the first region R1 shown in Fig. 4 as a second region R2. The second region R2 is a three-dimensional region of the three-dimensional region corresponding to the first region R1 that is located between the first substrate 30 and the second substrate 40. Fig. 6 is a top view of the second substrate 40. As shown in Fig. 6, the second substrate 40 has a hole 41. Furthermore, the void 50 is a space located inside the hole 41. In this case, the hole 41 is formed so that the void 50 includes at least the second region R2.

[0023] Similar to the three-dimensional region corresponding to the first region R1, the second region R2 has a bottom surface whose outer periphery is the shape of the ring-shaped optical waveguide 11. Therefore, similar to the three-dimensional region corresponding to the first region R1, the second region R2 has a columnar shape whose bottom surface has the same shape as the ring-shaped optical waveguide 11. The distance between the two bottom surfaces in the second region R2 can be set arbitrarily.

[0024] As described above, the optical module 1 includes a ring resonator 10, a heater 20, a first substrate 30, a second substrate 40, and a gap 50. The ring resonator 10 has a ring-shaped optical waveguide 11 and is attached to the first substrate 30. The heater 20 is provided inside the first substrate 30 within a first region R1 that surrounds the optical waveguide 11 when light passes through the first substrate 30 in a direction perpendicular to the surface of the first substrate 30, and heats the ring resonator 10. The second substrate 40 is stacked on the first substrate 30. The gap 50 is located between the first substrate 30 and the second substrate 40, and is formed so as to separate the first substrate 30 and the second substrate 40 within the first region R1.

[0025] For example, if the gap 50 is not formed and the first substrate 30 and the second substrate 40 are not spaced apart, the heat from the heater 20 is transferred to the second substrate 40 before reaching the ring-shaped optical waveguide 11. Therefore, the heat from the heater 20 cannot be efficiently transferred to the ring-shaped optical waveguide 11 (ring resonator structure).

[0026] On the other hand, as described above, the optical module 1 has a gap formed within the first region R1 to separate the first substrate 30 and the second substrate 40 when light passes through the first substrate 30 in a direction perpendicular to the surface of the first substrate 30. When light passes through the first substrate 30 in a direction perpendicular to the surface of the first substrate 30, the first region R1 has the shape of the optical waveguide 11 as its outer periphery, so the gap 50 is formed within the region of the first substrate 30 where the first region R1 is located. Therefore, heat from the heater 20 is not transmitted to the second substrate 40 until it is transmitted to the ring-shaped optical waveguide 11. As a result, heat from the heater 20 can be efficiently transmitted to the ring-shaped optical waveguide (ring resonator structure). This also allows the optical module 1 to reduce power consumption in the heater 20.

[0027] Furthermore, in the optical module 1, the heater 20 is disposed at a position including the center of the first region R1 that surrounds the optical waveguide 11. A typical heater for heating an optical waveguide may be disposed near the optical waveguide to efficiently heat the optical waveguide. However, in the optical module 1, the heater 20 is already capable of efficiently heating the optical waveguide due to the formation of the void 50, so the heater 20 may be disposed at a position including the center of the first region R1 that surrounds the optical waveguide 11. This eliminates the need to dispose the heater 20 near the optical waveguide, thereby improving the degree of freedom in the shape and position of the heater 20. This also allows for greater freedom in determining the placement locations of other optical and electronic components in the optical module 1.

[0028] Next, an optical module 1A will be described. The optical module 1A is a first modified example of the optical module 1. FIG. 7 is a diagram for explaining the optical module 1A. As shown in FIG. 7, the optical module 1A includes a ring resonator 10, a heater 20, a first substrate 30, a second substrate 40, and a gap 50, similar to the optical module 1. However, in the optical module 1A, the second substrate 40 does not have a hole 41, and the first substrate 30 has a hole 31. In this case, the gap 50 is a space formed inside the hole 31 of the first substrate 30. In the optical module 1A, the first substrate 30 is bonded to the second substrate 40 via a region of the surface of the first substrate 30 facing the second substrate 40 other than the region where the hole 31 is provided.

[0029] Next, the optical module 1B will be described. The optical module 1B is a second modified example of the optical module 1. FIG. 8 is a diagram for explaining the optical module 1B. As shown in FIG. 8, the optical module 1B includes a ring resonator 10, a heater 20, a first substrate 30, a second substrate 40, and a gap 50, similar to the optical module 1. The optical module 1B further includes a third substrate 60. The third substrate 60 is stacked in a first direction relative to the first substrate 30 and the second substrate 40. In this description, the first direction refers to the up-down direction indicated by the arrow A1 in FIG. 8. On the other hand, in the optical module 1B, the second substrate 40 does not have a hole 41, but the third substrate 60 has a hole 61. Therefore, the gap 50 is a space formed inside the hole 61 of the third substrate 60.

[0030] Next, an optical module 1C will be described. The optical module 1C is a third modified example of the optical module 1. FIG. 9 is a diagram for explaining the optical module 1C. As shown in FIG. 9, the optical module 1C includes a ring resonator 10, a heater 20, a first substrate 30, a second substrate 40, and a gap 50, similar to the optical module 1. Also, FIG. 9 illustrates a first region R1 and a second region R2, similar to FIG. 5. In the description of the optical module 1, as shown in FIGS. 2 and 5, the gap 50 is shown to be larger than the second region R2. However, in the optical module 1C, as shown in FIG. 9, the gap 50 may be the same size as the second region R2. <Second Embodiment> An optical module 2 according to a second embodiment will be described with reference to FIG. 10. FIG. 10 is a block diagram showing an example configuration of the optical module 2. Also, FIG. 11 is a cross-sectional view of the optical module 2. Specifically, FIG. 11 is a cross-sectional view of the optical module 2 taken along line BB' shown in FIG. 10. 12 is a diagram in which a three-dimensional region corresponding to the first region R1 is added to FIG.

[0031] 10, the optical module 2 includes a ring resonator 10, a heater 20, a first substrate 30, and a gap 50. Also, as shown in FIG. 11, the optical module 1 includes a ring resonator 10, a heater 20, a first substrate 30, a second substrate 40, and a gap 50.

[0032] The ring resonator 10 has a ring-shaped optical waveguide 11 and is attached to a first substrate 30. As shown in Fig. 10, the heater 20 is provided in the first substrate 30 within a first region R1 that surrounds the optical waveguide 11 when light passes through the first substrate 30 in a direction perpendicular to the surface of the first substrate 30, and heats the ring resonator 10. A second substrate 40 is stacked on the first substrate 30. A gap 50 is located between the first substrate 30 and the second substrate 40, and is formed so that the first substrate 30 and the second substrate 40 are spaced apart within a three-dimensional region corresponding to the first region R1.

[0033] For example, if the gap 50 is not formed and the first substrate 30 and the second substrate 40 are not spaced apart, the heat from the heater 20 is transferred to the second substrate 40 before reaching the ring-shaped optical waveguide 11. Therefore, the heat from the heater 20 cannot be efficiently transferred to the ring-shaped optical waveguide 11 (ring resonator structure).

[0034] On the other hand, as described above, the optical module 2 has a gap formed within the first region R1 to separate the first substrate 30 and the second substrate 40 when light passes through the first substrate 30 in a direction perpendicular to the surface of the first substrate 30. When light passes through the first substrate 30 in a direction perpendicular to the surface of the first substrate 30, the first region R1 has the shape of the optical waveguide 11 as its outer periphery, so the gap 50 is formed within the region of the first substrate 30 where the first region R1 is located. Therefore, heat from the heater 20 is not transferred to the second substrate 40 until it is transferred to the ring-shaped optical waveguide 11. As a result, heat from the heater 20 can be efficiently transferred to the ring-shaped optical waveguide (ring resonator structure). This also allows the optical module 2 to reduce power consumption in the heater 20. Some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes. (Supplementary Note 1) An optical module comprising: a first substrate, a second substrate laminated on the first substrate, a ring resonator having a ring-shaped optical waveguide and attached to the first substrate, a heater provided inside the first substrate in a first region having the optical waveguide as its outer periphery when light passes through the first substrate in a direction perpendicular to the surface of the first substrate and for heating the ring resonator, and a gap located between the first substrate and the second substrate and formed to separate the first substrate from the second substrate within the first region. (Supplementary Note 2) The optical module according to Supplementary Note 1, wherein the gap is a space inside a hole provided in a surface of the second substrate facing the first substrate, and the second substrate is bonded to the first substrate via a region of the surface of the second substrate facing the first substrate other than the region where the hole is provided. (Supplementary Note 3) The optical module of Supplementary Note 1 or 2, wherein the heater is disposed in the center of the first region. (Supplementary Note 4) The optical module of any one of Supplements 1 to 3, wherein the gap is filled with argon. (Supplementary Note 5) The optical module of any one of Supplements 1 to 4, wherein the first substrate contains at least quartz glass. (Supplementary Note 6) The optical module of any one of Supplements 1 to 5, wherein the second substrate contains at least silicon.

[0035] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0036] REFERENCE SIGNS 1, 1A, 1B, 1C, 2 Optical module 10 Ring resonator 11 Optical waveguide 20 Heater 30 First substrate 31 Hole 40 Second substrate 41 Hole 50 Air gap 60 Third substrate 61 Hole R1 First region R2 Second region

Claims

1. a first substrate; a second substrate laminated on the first substrate; a ring resonator having a ring-shaped optical waveguide and attached to the first substrate; a heater provided inside the first substrate in a first region having the optical waveguide as an outer periphery when light passes through the first substrate in a direction perpendicular to a surface of the first substrate, the heater heating the ring resonator; a gap located between the first substrate and the second substrate, the gap being formed so as to separate the first substrate and the second substrate within the first region; Equipped with Optical module.

2. the gap is a space inside a hole provided on a surface of the second substrate facing the first substrate, 2. The optical module according to claim 1, wherein the second substrate is bonded to the first substrate through an area of ​​the second substrate facing the first substrate other than the area in which the hole is provided.

3. The optical module according to claim 1 , wherein the heater is disposed in a central portion within the first region.

4. 3. The optical module according to claim 1, wherein the gap is filled with argon.

5. 3. The optical module according to claim 1, wherein the first substrate is made of at least quartz glass.

6. 3. The optical module according to claim 1, wherein the second substrate contains at least silicon.