Optical device, optical transmission apparatus, and optical reception apparatus

Abstract

To provide an optical device or the like capable of stabilizing extinction characteristics.SOLUTION: The optical device has: a rib-type optical waveguide formed on a substrate; a P-doped region formed in a first slab region of the rib-type optical waveguide; and an N-doped region formed in a second slab region of the rib-type optical waveguide. The optical device has: a first electrode connected to the P-doped region; a second electrode connected to the N-doped region; and a heater electrode for heating the rib-type optical waveguide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical device, an optical transmitting apparatus, and an optical receiving apparatus. [Background technology]

[0002] In recent years, the demand for optical fiber communications has increased along with the increase in communication capacity. Therefore, the development of optical devices, typified by silicon photonics, has been actively pursued. Known examples of such optical devices include optical attenuators such as variable optical attenuators (VOAs), which attenuate the intensity of signal light propagating through an optical waveguide in response to an electrical signal.

[0003] Fig. 15 is a schematic plan view showing an example of an optical device 100, and Fig. 16 is a schematic cross-sectional view taken along line AA shown in Fig. 15. A VOA 110, which is the optical device 100, has a Si substrate 121, a rib-type optical waveguide 102 formed on the Si substrate 121, and electrodes 103 connected to both sides of the rib-type optical waveguide 102. Furthermore, the VOA 110 has a cladding layer 122 formed on the Si substrate 121 and surrounding the rib-type optical waveguide 102 and the two electrodes 103.

[0004] The rib-type optical waveguide 102 has, for example, a waveguide 102A forming a Si core, and a first slab region 102D and a second slab region 102E on either side of the waveguide 102A. The rib-type optical waveguide 102 has an optical input section 102B and an optical output section 102C. The optical input section 102B is the input stage of the rib-type optical waveguide 102 that inputs signal light to the waveguide 102A. The optical output section 102C is the output stage of the rib-type optical waveguide 102 that outputs signal light from the waveguide 102A. A P-doped region 102F is formed in the first slab region 102D, and an N-doped region 102G is formed in the second slab region 102E. The waveguide 102A, the first slab region 102D, and the second slab region 102E are undoped regions. The rib-type optical waveguide 102 has a PIN diode structure with the P-doped region 102F, the undoped region, and the N-doped region 102G.

[0005] The electrode 103 includes a first electrode 103A electrically connected to the P-doped region 102F and a second electrode 103B electrically connected to the N-doped region 102G. The first electrode 103A serves as a signal electrode connected to an input pad 104 to which a voltage is applied, and the second electrode 103B serves as a ground electrode connected to a ground pad 105.

[0006] In the optical device 100, the input pad 104 is located near the center of the VOA 110, and power is supplied from the input pad 104 to the first electrode 103A via an input via 104A. In the optical device 100, the ground pad 105 is located near the center of the VOA 110, and grounding is provided from the second electrode 103B to the ground pad 105 via a ground via 105A.

[0007] When a positive voltage is applied to the first electrode 103A from the input pad 104, a current flows from the first electrode 103A to the second electrode 103B, and therefore a current flows in the rib-type optical waveguide 102 disposed between the first electrode 103A and the second electrode 103B. As a result, the signal light guided through the rib-type optical waveguide 102 is absorbed by free carrier absorption of the current flowing through the rib-type optical waveguide 102, and the intensity of the signal light is attenuated. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2013 / 062096 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-321712 [Patent Document 3] US Patent Application Publication No. 2007 / 0230522 Summary of the Invention [Problem to be solved by the invention]

[0009] The extinction characteristics of the VOA, which is the optical device 100, change over time. This change over time has large initial fluctuations, so by performing aging by heating before shipping, the change over time of the extinction characteristics can be accelerated and the extinction characteristics can be stabilized.

[0010] One way to stabilize the extinction characteristics is to heat the entire optical circuit chip on which the optical device 100 is mounted. However, since the optical circuit chip is equipped with not only the optical device 100 but also other elements, it is conceivable that heating may affect the other elements. Therefore, there is a demand for an optical device that can stabilize the extinction characteristics without affecting the other elements.

[0011] In one aspect, an object is to provide an optical device or the like that can stabilize extinction characteristics. [Means for solving the problem]

[0012] An optical device according to one embodiment comprises a rib-type optical waveguide formed on a substrate, a P-doped region formed in a first slab region of the rib-type optical waveguide, and an N-doped region formed in a second slab region of the rib-type optical waveguide, and further comprises a first electrode connected to the P-doped region, a second electrode connected to the N-doped region, and a heater electrode for heating the rib-type optical waveguide. [Effects of the Invention]

[0013] According to one aspect, the extinction characteristics can be stabilized. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic plan view showing an example of an optical device according to a first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 3] FIG. 3 is a schematic plan view illustrating an example of an optical device according to a second embodiment. [Figure 4]FIG. 4 is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 5] FIG. 5 is a schematic cross-sectional view taken along line BB shown in FIG. [Figure 6] FIG. 6 is a schematic plan view showing an example of an optical device according to a third embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 8] FIG. 8 is a schematic plan view showing an example of an optical device according to a fourth embodiment. [Figure 9] FIG. 9 is a schematic plan view showing an example of an optical device according to a fifth embodiment. [Figure 10] FIG. 10 is a schematic plan view showing an example of an optical device according to a sixth embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 12] FIG. 12 is a schematic cross-sectional view taken along line BB shown in FIG. [Figure 13] FIG. 13 is a schematic cross-sectional view taken along line CC shown in FIG. [Figure 14] FIG. 14 is an explanatory diagram showing an example of an optical transceiver that employs the optical device of this embodiment. [Figure 15] FIG. 15 is a schematic plan view showing an example of an optical device. [Figure 16] FIG. 16 is a schematic cross-sectional view taken along line AA shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, examples of optical devices and the like disclosed in the present application will be described in detail with reference to the drawings. Note that the disclosed technology is not limited to these examples. Furthermore, the examples shown below may be combined as appropriate within the scope of not causing any contradiction. [Example]

[0016] Fig. 1 is a schematic plan view showing an example of an optical device 1 according to a first embodiment, and Fig. 2 is a schematic cross-sectional view taken along line AA shown in Fig. 1. The optical device 1 shown in Fig. 1 is, for example, an optical attenuator such as a VOA (Variable Optical Attenuator). The optical device 1 includes a Si substrate 21, a rib-type optical waveguide 2 formed on the Si substrate 21, electrodes 3 electrically connected to both sides of the rib-type optical waveguide 2, and a cladding layer 22 formed on the Si substrate 21 and surrounding the rib-type optical waveguide 2 and the two electrodes 3. The optical device 1 further includes a heater electrode 6 disposed near the rib-type optical waveguide 2 and configured to heat the rib-type optical waveguide 2.

[0017] The rib-type optical waveguide 2 is formed of, for example, Si. The rib-type optical waveguide 2 has a waveguide 2A that forms a core. The waveguide 2A has a linear structure of the same width. The rib-type optical waveguide 2 has an optical input section 2B and an optical output section 2C. The optical input section 2B is the input stage of the rib-type optical waveguide 2 that inputs signal light to the waveguide 2A. The optical output section 2C is the output stage of the rib-type optical waveguide 2 that outputs signal light from the waveguide 2A.

[0018] The rib-type optical waveguide 2 has a first slab region 2D formed on one side of the waveguide 2A and a second slab region 2E formed on the other side of the waveguide 2A. The rib-type optical waveguide 2 has a P-doped region 2F formed in the first slab region 2D and an N-doped region 2G formed in the second slab region 2E. The P-doped region 2F is a region outside the first slab region 2D that is P-doped and electrically connected to the first electrode 3A. The N-doped region 2G is a region outside the second slab region 2E that is N-doped and electrically connected to the second electrode 3B.

[0019] The waveguide 2A, first slab region 2D, and second slab region 2E are undoped regions in the rib-type optical waveguide 2. The rib-type optical waveguide 2 has a PIN diode structure, for example, with a P-doped region 2F, an undoped region, and an N-doped region 2G.

[0020] The electrode 3 includes a first electrode 3A electrically connected to the P-doped region 2F and a second electrode 3B electrically connected to the N-doped region 2G. The first electrode 3A is a signal electrode connected to an input pad 4A to which a voltage is applied. The first electrode 3A is made of a material having electrical resistance, such as a metal such as aluminum or a semiconductor material such as silicon. The second electrode 3B is a ground electrode connected to a ground pad 5A. The second electrode 3B is also made of a material having electrical resistance, such as a metal such as aluminum or a semiconductor material such as silicon or germanium.

[0021] The cladding layer 22 is formed of, for example, SiO2. The input pad 4A is an electrode pad connected to the first electrode 3A via an input via 4A1. The ground pad 5A is an electrode pad connected to the second electrode 3B via a ground via 5A1.

[0022] In the optical device 1, the input pad 4A is located near the center of the optical device 1, and power is supplied from the input pad 4A to the first electrode 3A via the input via 4A1. In the optical device 1, the ground pad 5A is located near the center of the optical device 1, and power is supplied from the second electrode 3B to the ground pad 5A via the ground via 5A1.

[0023] When a voltage is applied to the first electrode 3A from the input pad 4A, a current flows from the first electrode 3A to the second electrode 3B, and therefore a current flows in the waveguide 2A in the rib-type optical waveguide 2 disposed between the first electrode 3A and the second electrode 3B. As a result, the signal light guided through the waveguide 2A is absorbed by free carrier absorption of the current flowing through the waveguide 2A, and the intensity of the signal light is attenuated.

[0024] The heater electrode 6 is disposed near the rib-type optical waveguide 2, for example, above the waveguide 2A within the rib-type optical waveguide 2, and heats the rib-type optical waveguide 2. The heater electrode 6 has a linear structure with the same width. For convenience of explanation, the heater electrode 6 is disposed above the waveguide 2A, but it may also be disposed below the waveguide 2A, and this can be modified as appropriate. The heater electrode 6 has an input pad 11A with an input via 11A1 connected to the input end of the heater electrode 6, and a ground pad 12A with a ground via 12A1 connected to the output end of the heater electrode 6.

[0025] The heater electrode 6 applies a voltage from the input pad 11A through the input via 11A1 to the input end of the heater electrode 6. The heater electrode 6 is grounded from the output end of the heater electrode 6 to the ground pad 12A through the ground via 12A1.

[0026] Before shipping the optical device 1, a probe (not shown) is connected to the input pad 11A and the ground pad 12A of the heater electrode 6. When a positive voltage is applied to the input end of the heater electrode 6 from the input pad 11A through the input via 11A1, a current flows from the input end to the output end of the heater electrode 6. As a result, the current flows from the input end to the output end of the heater electrode 6, causing the heater electrode 6 to generate heat, which heats the rib-type optical waveguide 2 running parallel to the heater electrode 6. Then, by aging the rib-type optical waveguide 2 by heating, the change in the extinction characteristics over time is accelerated, and the extinction characteristics of the VOA are stabilized.

[0027] In the optical device 1 of Example 1, before shipping, a probe is connected to the input pad 11A and the ground pad 12A, and a voltage is applied from the input pad 11A, causing a current to flow from the input end to the output end of the heater electrode 6. Then, as a result of the current flowing from the input end to the output end of the heater electrode 6, the heater electrode 6 generates heat, which heats the rib-type optical waveguide 2 running parallel to the heater electrode 6. As a result, by avoiding a situation in which other elements are also heated, as in the conventional case, the extinction characteristics of the VOA can be stabilized. Moreover, by avoiding the adverse effects of heating on other elements in the optical circuit chip on which the optical device 1, such as the VOA, is mounted, the long-term reliability of the optical circuit chip can be ensured.

[0028] For convenience of explanation, the waveguide 2A and the heater electrode 6 are shown as having a linear structure with the same width, but the present invention is not limited to this and can be modified as appropriate.

[0029] In the optical device 1 of Example 1, before shipping, the heater electrode 6 is heated and then the heater electrode 6 is not used. However, since the heater electrode 6 can be used even after shipping, the rib-type optical waveguide 2 may be heated using the heater electrode 6, and this can be changed as appropriate.

[0030] In the optical device 1 of Example 1, an input pad 11A connected to the input end of the heater electrode 6 and a ground pad 12A connected to the output end of the heater electrode 6 are connected as an example. However, if the distance between the input end and output end of the heater electrode 6 is increased, the electrical resistance may increase, and the voltage required for heating may also increase. Therefore, in order to shorten the distance over which current flows to the heater electrode 6, electrode pads other than the input pad 11A and the ground pad 12A may be disposed between the input end and output end of the heater electrode 6, and such an embodiment will be described below as Example 2. [Example]

[0031] Fig. 3 is a schematic plan view showing an example of an optical device 1A of Example 2, Fig. 4 is a schematic cross-sectional view taken along line AA shown in Fig. 3, and Fig. 5 is a schematic cross-sectional view taken along line BB shown in Fig. 3. Note that the same components as those in the optical device 1 of Example 1 are given the same reference numerals, and redundant explanations of the components and operations will be omitted.

[0032] The optical device 1A of Example 2 differs from the optical device 1 of Example 1 in that an electrode pad different from the input pad 11A and the ground pad 12A is disposed in a region between the input end and the output end of the heater electrode 6. The heater electrode 6 has a ground pad 12B, which is an electrode pad having a ground via 12B1, which is a connection via, connected to the vicinity of the intermediate region between the input end and the output end of the heater electrode 6. Furthermore, the heater electrode 6 has an input pad 11B, which is an electrode pad having an input via 11B1, which is a connection via, connected to the vicinity of the intermediate region.

[0033] The ground via 12B1 is connected to the intermediate portion closer to the input pad 11A. Therefore, the distance between the input via 11A1 and the ground via 12B1 is shorter than the distance between the input via 11A1 and the ground via 12A1 of the heater electrode 6. The input via 11B1 is connected to the intermediate portion closer to the ground pad 12A. Therefore, the distance between the input via 11B1 and the ground via 12A1 is shorter than the distance between the input via 11A1 and the ground via 12A1 of the heater electrode 6.

[0034] A voltage is applied from input pad 11A to the input end of heater electrode 6 via input via 11A1. Heater electrode 6 is grounded to ground pad 12B from near the middle of heater electrode 6 via ground via 12B1. In other words, the distance between input via 11A1 and ground via 12B1 is made shorter than the distance between input via 11A1 and ground via 12A1 of heater electrode 6. As a result, electrical resistance is reduced, and the applied voltage required for heating can be suppressed.

[0035] Furthermore, a voltage is applied from input pad 11B to the vicinity of the middle portion of heater electrode 6 via input via 11B1. Heater electrode 6 is grounded from the output end of heater electrode 6 to ground pad 12A via ground via 12A1. In other words, the distance between input via 11B1 and ground via 12A1 is made shorter than the distance between input via 11A1 of heater electrode 6 and ground via 12A1. As a result, electrical resistance is reduced, and the applied voltage required for heating can be suppressed.

[0036] Before shipping the optical device 1A, probes (not shown) are connected to the input pads 11A, 11B, and ground pads 12A and 12B of the heater electrode 6, and a voltage is applied between the input pads 11A and 11B. Then, a current flows from the input end of the heater electrode 6 to the vicinity of the intermediate portion, and from the vicinity of the intermediate portion to the output end, causing the heater electrode 6 to generate heat, which heats the rib-type optical waveguide 2 running parallel to the heater electrode 6. Then, aging the rib-type optical waveguide 2 by heating accelerates the change in the extinction characteristics over time, stabilizing the extinction characteristics of the VOA.

[0037] In the optical device 1A of Example 2, before shipping, probes are connected to the input pads 11A, 11B, and ground pads 12A and 12B of the heater electrode 6, and a voltage is applied between the input pads 11A and 11B. Then, current flows from the input end of the heater electrode 6 to the vicinity of the intermediate portion and from the vicinity of the intermediate portion to the output end, causing the heater electrode 6 to generate heat, which heats the rib-type optical waveguide 2 running parallel to the heater electrode 6. As a result, electrical resistance is reduced, and the applied voltage required for heating can be suppressed. Furthermore, by avoiding the situation where other elements are also heated, as in the conventional case, the extinction characteristics of the VOA can be stabilized. Moreover, by avoiding the adverse effects of heating on other elements in the optical circuit chip on which the optical device 1A, such as the VOA, is mounted, the long-term reliability of the optical circuit chip can be ensured.

[0038] In the optical device 1A of Example 2, two input pads 11A and 11B connected to the heater electrode 6 and two ground pads 12A and 12B connected to the heater electrode 6 are illustrated. However, before shipping, probes must be connected to these two input pads 11A and 11B and two ground pads 12A and 12B, which is a significant workload. To address this issue, an embodiment in which the number of input pads and ground pads is reduced will be described below as Example 3. [Example]

[0039] Fig. 6 is a schematic plan view showing an example of an optical device 1B of Example 3, and Fig. 7 is a schematic cross-sectional view taken along line AA shown in Fig. 6. Note that the same components as those in the optical device 1A of Example 2 are given the same reference numerals, and explanations of the overlapping components and operations will be omitted. The optical device 1A of Example 2 and the optical device 1B of Example 3 differ in that they have a single input pad 11C connecting the input via 11C1 and the input via 11C2, and a single ground pad 12C connecting the ground via 12C1 and the ground via 12C2.

[0040] The input pad 11C has an input via 11C1 connected to the input end of the heater electrode 6, an input via 11C2 connected to an intermediate portion of the heater electrode 6, and a first connection line 25 connecting the input vias 11C1 and 11C2. The ground pad 12C has a ground via 12C1 connected to the output end of the heater electrode 6, a ground via 12C2 connected to an intermediate portion of the heater electrode 6, and a second connection line 26 connecting the ground vias 12C1 and 12C2.

[0041] The heater electrode 6 applies a voltage from the input pad 11C via input vias 11C1 and 11C2 to the input end and the vicinity of the intermediate portion of the heater electrode 6. The heater electrode 6 is grounded from the vicinity of the intermediate portion and the output end of the heater electrode 6 to the ground pad 12C via ground vias 12C1 and 12C2.

[0042] Before shipping the optical device 1B, a probe (not shown) is connected to the input pad 11C and ground pad 12C of the heater electrode 6, and a voltage is applied from the input pad 11C. Then, a current flows from the input end of the heater electrode 6 to near the intermediate portion, and from near the intermediate portion to the output end, causing the heater electrode 6 to generate heat, which heats the rib-type optical waveguide 2 running parallel to the heater electrode 6. Then, aging the rib-type optical waveguide 2 by heating accelerates the change over time in the extinction characteristics, stabilizing the extinction characteristics of the VOA.

[0043] In the optical device 1B of the third embodiment, before shipping, probes are connected to the input pad 11C and the ground pad 12C, and a current flows through the heater electrode 6 to heat the rib-type optical waveguide 2. As a result, the workload for connecting the probes to the input pad 11C and the ground pad 12C can be reduced.

[0044] In addition, in the optical device 1B, when a voltage is applied from the input pad 11C and a current flows from the input end of the heater electrode 6 to the vicinity of the intermediate portion and from the vicinity of the intermediate portion to the output end, the heater electrode 6 generates heat, which heats the rib-type optical waveguide 2 running parallel to the heater electrode 6. As a result, the extinction characteristics of the VOA can be stabilized by avoiding the situation where other elements are also heated, as in the conventional case. Moreover, by avoiding the adverse effects of heating on other elements in the optical circuit chip on which the optical device 1B, such as the VOA, is mounted, the long-term reliability of the optical circuit chip can be ensured.

[0045] In addition, the optical device 1B of Example 3 is exemplified as having an input pad 4A, a ground pad 5A, an input pad 11C, and a ground pad 12C, but the ground pad 5A may also be used as the ground pad 12C, and this embodiment will be described below as Example 4. [Example]

[0046] 8 is a schematic plan view showing an example of an optical device 1C according to a fourth embodiment. The same components as those in the optical device 1B according to the third embodiment are denoted by the same reference numerals, and explanations of the overlapping components and operations will be omitted. The optical device 1B according to the third embodiment differs from the optical device 1C according to the fourth embodiment in that the ground pad 5A for the VOA is also used as the ground pad 12D for the heater electrode 6.

[0047] Input pad 11C has input via 11C1 connected to the input end of heater electrode 6, input via 11C2 connected to an intermediate portion of heater electrode 6, and a first connection line 25 connecting input via 11C1 and input via 11C2. Ground pad 12D has ground via 12C1 connected to the output end of heater electrode 6, ground via 12C2 connected to an intermediate portion of heater electrode 6, and a second connection line 26A connecting ground via 12C1 and ground via 12C2. Second connection line 26A is electrically connected to ground via 5A1 connected to second electrode 3B.

[0048] Before shipping the optical device 1C, a probe (not shown) is connected to the input pad 11C and ground pad 12D of the heater electrode 6, and a voltage is applied from the input pad 11C. Then, a current flows from the input end of the heater electrode 6 to near the intermediate portion, and from near the intermediate portion to the output end, causing the heater electrode 6 to generate heat, which heats the rib-type optical waveguide 2 running parallel to the heater electrode 6. Then, aging the rib-type optical waveguide 2 by heating accelerates the change in the extinction characteristics over time, stabilizing the extinction characteristics of the VOA.

[0049] When a voltage is applied to the first electrode 3A from the input pad 4A, a current flows from the first electrode 3A to the second electrode 3B, and thus a current flows in the waveguide 2A in the rib-type optical waveguide 2 disposed between the first electrode 3A and the second electrode 3B. The second electrode 3B is then grounded to the ground pad 12D via the ground via 5A1 and the second connection line 26A. As a result, the signal light guided through the waveguide 2A is absorbed by free carrier absorption of the current flowing through the waveguide 2A, and the intensity of the signal light is attenuated.

[0050] In the optical device 1C of the fourth embodiment, the ground via 5A1, the ground via 12C1, and the ground via 12C2 are shared by the ground pad 12D, which results in a reduction in the number of ground pads compared to the optical device 1B shown in FIG.

[0051] In the optical device 1C, probes are connected to the input pads 11C and the ground pads 12D before shipping, which reduces the workload involved in connecting the probes to the input pads 11C and the ground pads 12D.

[0052] In addition, in the optical device 1C, when a voltage is applied from the input pad 11C and a current flows from the input end of the heater electrode 6 to the vicinity of the intermediate portion and from the vicinity of the intermediate portion to the output end, the heater electrode 6 generates heat, which heats the rib-type optical waveguide 2 running parallel to the heater electrode 6. As a result, the extinction characteristics of the VOA can be stabilized by avoiding the situation where other elements are also heated, as in the conventional case. Moreover, by avoiding the adverse effects of heating on other elements in the optical circuit chip on which the optical device 1B, such as the VOA, is mounted, the long-term reliability of the optical circuit chip can be ensured.

[0053] In the optical device 1C of Example 4, the ground pad 5A is also used as the ground pad 12D. However, it is possible that a voltage may be applied to the heater electrode 6 even after the rib-type optical waveguide 2 has been heated by the heater electrode 6. Therefore, an embodiment for dealing with such a situation will be described below as Example 5. [Example]

[0054] 9 is a schematic plan view showing an example of an optical device 1D according to a fifth embodiment. The same components as those in the optical device 1C according to the fourth embodiment are designated by the same reference numerals, and explanations of the overlapping components and operations will be omitted. The optical device 1C according to the fourth embodiment differs from the optical device 1D according to the fifth embodiment in that the input pad 11C and the ground pad 12D are electrically connected by wire bonding 13 after the heating process using the heater electrode 6.

[0055] After the optical device 1D is subjected to a heating process by the heater electrode 6, the input pad 11C and the ground pad 12D are electrically connected by a bonding wire 13. As a result, it is possible to prevent a voltage from being applied to the heater electrode 6 after the heating process.

[0056] In the optical device 1 of Example 1, a rib-type optical waveguide 2 with a straight structure is exemplified, but this is not limited to this and a rib-type optical waveguide with a folded structure may also be used, and an embodiment of this will be described below as Example 6. [Example]

[0057] Fig. 10 is a schematic plan view showing an example of an optical device 1E of Example 6, Fig. 11 is a schematic cross-sectional view taken along line AA shown in Fig. 10, Fig. 12 is a schematic cross-sectional view taken along line BB shown in Fig. 10, and Fig. 13 is a schematic cross-sectional view taken along line CC shown in Fig. 10. Note that the same components as those in the optical device 1 of Example 1 are given the same reference numerals, and redundant explanations of the components and operations will be omitted.

[0058] The optical device 1E of the sixth embodiment differs from the optical device 1 of the first embodiment in that the optical device 1E of the sixth embodiment includes an outgoing path device 1E1, a return path device 1E2, and a folded waveguide 2A3 that connects the output end of the outgoing path device 1E1 and the input end of the return path device 1E2. In other words, the optical device 1E folds the outgoing path device 1E1 and the return path device 1E2 back at the folded waveguide 2A3, so that the length of the optical device 1E can be shortened.

[0059] The first electrode 3A has a first electrode 3A1 on the outgoing path, a first electrode 3A2 on the return path, and a first electrode 3A3 on the return path that electrically connects the first electrode 3A1 on the outgoing path and the first electrode 3A2 on the return path. The first electrode 3A1 on the outgoing path has an input pad 4B with an input via 4B1 that electrically connects them. The second electrode 3B has a ground pad 5B with a ground via 5B1 that electrically connects to the input end of the second electrode 3B1.

[0060] The outgoing device 1E1 includes a first waveguide 2A1 forming the core of a first rib-type optical waveguide formed on a Si substrate 21, and a first P-doped region 2F1 formed in a first slab region 2D1 of the first waveguide 2A1. The outgoing device 1E1 also includes a first N-doped region 2G1 formed in a second slab region 2E1 of the first waveguide 2A1, a first electrode 3A1 on the return side connected to the first P-doped region 2F1, and a second electrode 3B1 connected to the first N-doped region 2G1. The outgoing device 1E1 also includes a first heater electrode 6A1 disposed near the first waveguide 2A1 and configured to heat the first waveguide 2A1.

[0061] The return-side device 1E2 includes a second waveguide 2A2 forming the core of a second rib-type optical waveguide formed on a Si substrate 21, a second P-doped region 2F2 formed in a third slab region 2D2 of the second waveguide 2A2 and connected to the first return-side electrode 3A2, a second N-doped region 2G2 formed in a fourth slab region 2E2 of the second waveguide 2A2 and connected to the second electrode 3B1, and a second heater electrode 6A2 disposed near the second waveguide 2A2 and heating the second waveguide 2A2.

[0062] The folded waveguide 2A3 optically couples the first waveguide 2A1 and the second waveguide 2A2.

[0063] The first heater electrode 6A1 has an input pad 11E with a first input via 11E1 connecting to the input end of the first heater electrode 6A1. The second heater electrode 6A2 has a ground pad 12E with a second ground via 12E2 connecting to the output end of the second heater electrode 6A2. The first heater electrode 6A1 has a first ground via 12E1 connecting to the output end of the first heater electrode 6A1 and a second connection line 26E connecting between the first ground via 12E1 and the second ground via 12E2. The second heater electrode 6A2 has a second input via 11E2 connecting to the output end of the second heater electrode 6A2 and a first connection line 25E connecting between the second input via 11E2 and the first input via 11E1.

[0064] Before shipping, the optical device 1E has a probe (not shown) connected to the input pad 11E and the ground pad 12E, and a voltage is applied from the input pad 11E. Then, a current flows from the input terminal to the output terminal of the first heater electrode 6A1 and the second heater electrode 6A2, causing the first heater electrode 6A1 and the second heater electrode 6A2 to generate heat. The first heater electrode 6A1 heats the parallel first waveguide 2A1, and the second heater electrode 6A2 heats the parallel second waveguide 2A2. Aging the first waveguide 2A1 and the second waveguide 2A2 by heating accelerates the change in the extinction characteristics over time, stabilizing the extinction characteristics of the VOA.

[0065] In the optical device 1E of Example 6, before shipping, probes are connected to the input pad 11E and the ground pad 12E. Applying a voltage to the input pad 11E causes a current to flow from the input terminals of the first heater electrode 6A1 and the second heater electrode 6A2 to the output terminals. The current flowing from the input terminals to the output terminals of the first heater electrode 6A1 and the second heater electrode 6A2 generates heat. The first heater electrode 6A1 heats the parallel first waveguide 2A1, and the second heater electrode 6A2 heats the parallel second waveguide 2A2. This prevents other elements from being heated, as in the conventional case, thereby stabilizing the extinction characteristics of the VOA. Furthermore, the long-term reliability of the optical circuit chip can be ensured by preventing the adverse effects of heating on other elements within the optical circuit chip on which the optical device 1E, such as the VOA, is mounted. Moreover, since the optical waveguide of the optical device 1E has a folded structure, the length of the optical device can be shortened.

[0066] Furthermore, since the optical device 1E has a folded optical waveguide, the length dimensions of the first heater electrode 6A1 for heating the first waveguide 2A1 and the second heater electrode 6A2 for heating the second waveguide 2A2 are shortened, thereby reducing the electrical resistance and suppressing the applied voltage required for heating.

[0067] For ease of explanation, an electrode pad other than the ground pad 12E and the input pad 11E may be connected to an intermediate portion between the input and output ends of the first heater electrode 6A1, and this configuration can be modified as appropriate. In this case, the first heater electrode 6A1 has a first electrode pad other than the input pad 11E and the ground pad 12E, which has a first connection via connected to an intermediate portion of the first heater electrode 6A1 between the first input via 11E1 and the first ground via 12E1. The distance between the input via 11A1 and the first connection via is made shorter than the distance between the first input via 11E1 and the first ground via 12E1 of the first heater electrode 6A1. As a result, electrical resistance is reduced, and the applied voltage required for heating can be suppressed.

[0068] Alternatively, an electrode pad other than the ground pad 12E and the input pad 11E may be connected to an intermediate portion between the input and output ends of the second heater electrode 6A2, and this configuration can be modified as appropriate. In this case, the second heater electrode 6A2 has a second electrode pad other than the input pad 11E and the ground pad 12E, which has a second connection via connected to an intermediate portion of the second heater electrode 6A2 between the second input via 11E2 and the second ground via 12E2. The distance between the input via 11A2 and the second connection via is made shorter than the distance between the second input via 11E2 and the second ground via 12E2 of the second heater electrode 6A2. As a result, electrical resistance is reduced, and the applied voltage required for heating can be suppressed.

[0069] Next, an optical transceiver 50 employing the optical devices 1 to 1E of the first to sixth embodiments will be described. FIG. 14 is an explanatory diagram showing an example of an optical transceiver 50 employing the optical device 1 of the present embodiment. The optical transceiver 50 shown in FIG. 14 is connected to an output optical fiber FC and an input optical fiber FC. The optical transceiver 50 includes a DSP (Digital Signal Processor) 51, an optical transmitter 53, and an optical receiver 54. The DSP 51 is an electrical component that performs digital signal processing. For example, the DSP 51 performs processing such as encoding transmission data, generates an electrical signal including the transmission data, and outputs the generated electrical signal to the optical transmitter 53. The DSP 51 also acquires an electrical signal including reception data from the optical receiver 54 and performs processing such as decoding the acquired electrical signal to obtain the reception data.

[0070] The optical transmitter 53 modulates the supplied light with the electrical signal output from the DSP 51 and outputs the obtained transmission light to the optical fiber FC. The optical transmitter 53 has an optical modulation unit 53A that generates transmission light by modulating the supplied light with the electrical signal input to the optical modulator as the light propagates through the waveguide.

[0071] The optical receiver 54 has an optical receiving section 54A that receives an optical signal from the optical fiber FC and demodulates the received light using the supplied light. The optical receiver 54 then converts the demodulated received light into an electrical signal and outputs the converted electrical signal to the DSP 51. The optical transmitter 53 and the optical receiver 54 each incorporate optical devices 1 to 1E that guide light.

[0072] For convenience of explanation, the optical transceiver 50 has been illustrated as having a built-in optical transmitter 53 and an optical receiver 54, but the optical transceiver 50 may have a built-in optical transmitter 53 or an optical receiver 54. For example, the optical devices 1 to 1E may be applied to an optical transceiver 50 having a built-in optical transmitter 53 or an optical transceiver 50 having a built-in optical receiver 54, and modifications can be made as appropriate.

[0073] In the embodiment, the rib-type optical waveguide 2 may be a PLC (Planar Lightwave Circuit) in which both the core and clad are made of SiO2, an InP waveguide, or a GaAs waveguide. The core may be Si or Si3N4, the lower clad may be SiO2, and the upper clad may be SiO2 or air, etc.

[0074] Furthermore, the components of each unit shown in the figure do not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each unit is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0075] Furthermore, the various processing functions performed by each device may be executed in whole or in part on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit) or MCU (Micro Controller Unit)). Needless to say, the various processing functions may be executed in whole or in part on a program analyzed and executed by a CPU (or a microcomputer such as an MPU or MCU), or on hardware using wired logic. [Explanation of symbols]

[0076] 1 Optical Devices 2 Rib-type optical waveguide 2A waveguide 2D First Slab Region 2E Second Slab Area 2F P-doped region 2G N-doped region 3A First electrode 3B Second electrode 6 heater electrode

Claims

1. a rib-type optical waveguide formed on a substrate; a P-doped region formed in the first slab region of the rib-type optical waveguide; an N-doped region formed in the second slab region of the rib-type optical waveguide; a first electrode in contact with the P-doped region; a second electrode connected to the N-doped region; a heater electrode for heating the rib-type optical waveguide; An optical device comprising:

2. The heater electrode is an input pad having an input via connected to an input end of the heater electrode; a ground pad having a ground via connected to the output end of the heater electrode; an electrode pad different from the ground pad and the input pad, the electrode pad including a connection via connected to a portion between the input via and the ground via; 2. The optical device according to claim 1, wherein:

3. The connection via is a first connection via; a second connection via connected to a portion between the input via and the first connection via; The input pad is 3. The optical device according to claim 2, further comprising a first connection line electrically connecting the input via and the first connection via.

4. The connection via is a first connection via; a second connection via connected to a portion between the input via and the first connection via; The ground pad is 3. The optical device according to claim 2, further comprising a second connection line electrically connecting the ground via and the second connection via.

5. The connection via is a first connection via; a second connection via connected to a portion between the input via and the first connection via; The input pad is a first connection line electrically connecting the input via and the first connection via; The ground pad is 3. The optical device according to claim 2, further comprising a second connection line electrically connecting the ground via and the second connection via.

6. The second connecting line is 6. The optical device according to claim 5, further comprising a third connection via electrically connected to the second electrode.

7. 7. The optical device according to claim 5, wherein after the rib-type optical waveguide is heated by the heater electrode, the input pad and the ground pad are electrically connected by wire bonding.

8. a first rib-type optical waveguide formed on a substrate; a first P-doped region formed in a first slab region of the first rib-type optical waveguide; a first N-doped region formed in the second slab region of the first rib-type optical waveguide; a first electrode in contact with the first P-doped region; a second electrode in contact with the first N-doped region; a first heater electrode for heating the first rib-type optical waveguide; and a second rib-type optical waveguide formed on the substrate; a second P-doped region formed in the third slab region of the second rib-type optical waveguide and connected to the first electrode; a second N-doped region formed in the fourth slab region of the second rib-type optical waveguide and connected to the second electrode; a return-side device having a second heater electrode for heating the second rib-type optical waveguide; an optical waveguide connecting the first rib-type optical waveguide and the second rib-type optical waveguide;

9. The first heater electrode comprises: an input pad having a first input via connected to an input end of the first heater electrode; The second heater electrode comprises: a ground pad having a second ground via connected to an output end of the second heater electrode; The first heater electrode comprises: a first ground via connected to an output end of the first heater electrode, and a second connection line connecting the first ground via and the second ground via; The second heater electrode comprises:

9. The optical device according to claim 8, further comprising a second input via connected to the input end of the second heater electrode, and a first connecting line connecting between the second input via and the first input via.

10. The first heater electrode comprises: a first electrode pad different from the first input pad and the first ground pad, the first electrode pad having a first connection via connected to a portion of the first heater electrode between the first input via and the first ground via; The second heater electrode comprises:

10. The optical device of claim 9, further comprising a second electrode pad different from the second input pad and the second ground pad, the second electrode pad having a second connection via that connects to a portion of the second heater electrode between the second input via and the second ground via.

11. an optical modulation unit that optically modulates light using a transmission signal and transmits the transmission light; an optical device disposed in the optical modulation unit, The optical device is a rib-type optical waveguide formed on a substrate; a P-doped region formed in the first slab region of the rib-type optical waveguide; an N-doped region formed in the second slab region of the rib-type optical waveguide; a first electrode in contact with the P-doped region; a second electrode connected to the N-doped region; a heater electrode for heating the rib-type optical waveguide; An optical transmitting device comprising:

12. an optical receiving unit that receives a reception signal from the received light using light; an optical device disposed in the optical receiving unit, The optical device is a rib-type optical waveguide formed on a substrate; a P-doped region formed in the first slab region of the rib-type optical waveguide; an N-doped region formed in the second slab region of the rib-type optical waveguide; a first electrode in contact with the P-doped region; a second electrode connected to the N-doped region; a heater electrode for heating the rib-type optical waveguide; An optical receiving device comprising:

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