Optical device, optical receiver, and optical transmitter

Abstract

The invention relates to an optical device, an optical receiver, and an optical transmitter. The optical device includes: a channel waveguide having a waveguide width that increases in a tapered manner; and a rib waveguide connected to a side of the channel waveguide where the waveguide width is increased, and including a rib portion and a plate portion. The rib-shaped waveguide includes a tapered waveguide in which a rib width of a rib portion increases in a tapered manner further away from a portion at a side connected to the channel waveguide.

Description

Technical Field

[0001] The implementation methods discussed in this article involve optical devices, optical receivers, and optical transmitters. Background Technology

[0002] Figure 12 This is a schematic plan view showing an example of a conventional edge coupler (EC) 200. Figure 12 The EC 200 shown is a substrate-type optical waveguide element, which is arranged near the chip end face D1 and optically coupled to the core C of the optical fiber F. Furthermore, the EC 200 is a spot size converter, which, for example, makes the spot size of the signal light or locally oscillating light closer to the mode field diameter of the optical fiber F.

[0003] EC 200 includes a cladding layer 222 made of, for example, SiO2, and an optical waveguide 210 covered by the cladding layer 222 and made of, for example, Si. The optical waveguide 210 is, for example, an optical waveguide with a channel structure. The optical waveguide 210 includes a tapered waveguide 211 and a linear waveguide 212 connected to the tapered waveguide 211. The tapered waveguide 211 has a structure in which the waveguide width gradually increases with distance from the starting point of the tapered waveguide 211. The linear waveguide 212 is a waveguide connected to the side of the tapered waveguide 211 where the waveguide width increases. Simultaneously, the linear waveguide 212 and the tapered waveguide 211 have the same waveguide thickness.

[0004] Figure 13 It shows along Figure 12 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line AA in EC 200. Figure 13 The EC 200 shown includes a Si substrate 221, a cladding layer 222, and a component layer 223 disposed on the Si substrate 221. Along as shown... Figure 13 The schematic cross-section shown by line AA is the section of EC 200 in which the linear waveguide 212 is arranged. The linear waveguide 212 and the tapered waveguide 211 of the optical waveguide 210 are arranged in the component layer 223.

[0005] Patent Document 1: Japanese Publication No. 2017-534926, PCT International Application

[0006] Patent Document 2: Japanese Patent Application Publication No. 2009-251218

[0007] Patent Document 3: U.S. Patent Application Publication No. 2019 / 0170941

[0008] Patent Document 4: US Patent No. 10162133

[0009] However, the conventional EC 200 includes an optical waveguide 210 with a channel structure; therefore, sidewall roughening occurs due to etching during the formation of the optical waveguide 210, and optical loss or reflection increases due to light scattering caused by the sidewall roughening. Furthermore, the effect of sidewall roughening is significant in the thickened portions of the optical waveguide 210.

[0010] Therefore, one aspect of the embodiments of the present invention is to provide an optical device or the like that can improve coupling loss and light reflection. Summary of the Invention

[0011] According to one aspect of the embodiments, an optical device includes: a channel waveguide having a waveguide width that increases in a tapered manner; and a ribbed waveguide connected to the side of the channel waveguide where the waveguide width increases, and including a rib portion and a planar portion. The ribbed waveguide includes a tapered waveguide in which the rib width of the rib portion increases in a tapered manner as it moves away from the side connected to the channel waveguide. Attached Figure Description

[0012] Figure 1 This is a schematic plan view illustrating an example of an EC according to the first embodiment;

[0013] Figure 2A It shows along Figure 1 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line AA in EC;

[0014] Figure 2B It shows along Figure 1 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line BB in EC;

[0015] Figure 2C It shows along Figure 1 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line CC in EC;

[0016] Figure 3 This is a schematic plan view illustrating an example of an EC according to a second embodiment;

[0017] Figure 4A It shows along Figure 3 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line AA in EC;

[0018] Figure 4B It shows along Figure 3 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line BB in EC;

[0019] Figure 4C It shows along Figure 3 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line CC in EC;

[0020] Figure 4D It shows along Figure 3 A schematic cross-sectional view of an example of a schematic cross-sectional portion of line DD in EC shown;

[0021] Figure 5 This is a schematic plan view illustrating an example of an EC according to a third embodiment;

[0022] Figure 6A It shows along Figure 5 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line AA in EC;

[0023] Figure 6B It shows along Figure 5 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line BB in EC;

[0024] Figure 6C It shows along Figure 5 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line CC in EC;

[0025] Figure 6D It shows along Figure 5 A schematic cross-sectional view of an example of a schematic cross-sectional portion of line DD in EC shown;

[0026] Figure 7 This is a schematic plan view illustrating an example of the EC according to the fourth embodiment;

[0027] Figure 8 It shows along Figure 7 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line AA in EC;

[0028] Figure 9 This is a diagram illustrating an example of an optical transceiver in one embodiment;

[0029] Figure 10 This is a schematic plan view of an example of the EC, which is a comparative example;

[0030] Figure 11 It shows along Figure 10 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line AA in EC;

[0031] Figure 12 This is a schematic plan view showing an example of a conventional EC; and

[0032] Figure 13 It shows along Figure 12 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line AA in EC. Detailed Implementation

[0033] In a conventional EC 200, the optical waveguide 210 has a channel structure, and therefore light scattering occurs due to the roughening of the sidewalls. To address this, the applicant of this application proposed a comparative example EC 100, which is capable of handling the situation described above.

[0034] Comparative example

[0035] Figure 10 This is a schematic plan view of an example of the EC 100, which is a comparative example. Figure 10 The EC 100 shown is part of a substrate-type optical waveguide element disposed near the chip end face D1 and optically coupled to the core C of the optical fiber F. Furthermore, the EC 100 is a spot size converter, which, for example, makes the spot size of the signal light or locally oscillating light closer to the mode field diameter of the optical fiber F.

[0036] EC 100 includes a cladding layer 122 made of, for example, SiO2, and an optical waveguide 110 covered by the cladding layer 122 and made of, for example, Si. For example, the optical waveguide 110 is a ribbed waveguide including a rib portion 110A and a flat plate portion 110B, the flat plate portion 110B being disposed on both sides of the rib portion 110A and having a thinner thickness than the rib portion 110A. The optical waveguide 110 includes a tapered waveguide 111 and a linear waveguide 112 connected to the tapered waveguide 111. The tapered waveguide 111 has a structure in which the waveguide width gradually increases with distance from the starting point of the tapered waveguide 111. The linear waveguide 112 is a waveguide connected to the side of the tapered waveguide 111 where the waveguide width increases and has a constant waveguide width. Simultaneously, the linear waveguide 112 and the tapered waveguide 111 have the same waveguide thickness.

[0037] Figure 11 It shows along Figure 10 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line AA in EC 100. Figure 11 The EC 100 shown includes a Si substrate 121, a cladding layer 122, and a component layer 123 disposed on the Si substrate 121. Along as shown... Figure 11 The schematic cross-section shown by line AA is the section of EC 100 in which the linear waveguide 112 is arranged. The linear waveguide 112 of the optical waveguide 110 is arranged in the component layer 123. In addition, the tapered waveguide 111 of the optical waveguide 110 is arranged in the component layer 123.

[0038] In the comparative example EC 100, the optical waveguide 110 has a rib structure; therefore, sidewall roughening does not occur, and optical coupling loss and optical reflection caused by light scattering due to sidewall roughening can be prevented.

[0039] However, in the comparative example EC 100, because the optical waveguide 110 has a rib structure, the light confinement of the tapered waveguide 111 of the optical waveguide 110 is very strong, and it is difficult to increase the mode field.

[0040] Preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments. Furthermore, the embodiments described below can be appropriately combined as long as no contradiction is found.

[0041] (a) First embodiment

[0042] Figure 1 This is a schematic plan view illustrating an example of EC 1 according to the first embodiment. Figure 1 The EC 1 shown is part of a substrate-type optical waveguide element arranged near the chip end face D1 and optically coupled to the core C of the optical fiber F. Furthermore, EC 1 is a spot size converter, which, for example, makes the spot size of the signal light or locally oscillating light closer to the mode field diameter of the optical fiber F.

[0043] EC 1 includes a cladding layer 22 made of, for example, SiO2, and an optical waveguide 10 covered by the cladding layer 22 and made of, for example, Si. The optical waveguide 10 includes: a channel waveguide 11 in which the waveguide width tapers from near the chip end face D1; and a ribbed waveguide 12 connected to the side of the channel waveguide 11 where the width increases, and including a rib portion 12A and a flat portion 12B. The channel waveguide 11 is configured with a tapered waveguide in which the waveguide width gradually increases with increasing distance from the chip end face D1.

[0044] The ribbed waveguide 12 includes a rib portion 12A and a flat plate portion 12B, which is formed on both sides of the rib portion 12A and has a thinner thickness than the rib portion 12A. The ribbed waveguide 12 includes a tapered waveguide 13 and a linear waveguide 14 connected to the tapered waveguide 13. The tapered waveguide 13 is connected to the side of the channel waveguide 11 where the waveguide width increases, and has a structure where the waveguide width gradually increases away from the starting point of the tapered waveguide 13. The linear waveguide 14 is a linear waveguide connected to the side of the tapered waveguide 13 where the waveguide width increases and has a constant waveguide width. Simultaneously, the linear waveguide 14 and the tapered waveguide 13 have the same waveguide thickness. In other words, the rib width of the rib portion 12A of the ribbed waveguide 12 increases in a tapered manner away from the portion connected to the channel waveguide 11.

[0045] Figure 2AIt shows along Figure 1 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line AA in EC 1. Figure 2A EC 1 shown includes a Si substrate 21, a cladding layer 22, and a first component layer 23 disposed on the Si substrate 21. Along as shown... Figure 2A The schematic cross-section shown by line AA is the section of EC 1 in which the linear waveguide 14 of the ribbed waveguide 12 is arranged. The linear waveguide 14 of the ribbed waveguide 12 is arranged in the first component layer 23.

[0046] Figure 2B It shows along Figure 1 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line BB in EC 1. Figure 2B The EC 1 shown includes a Si substrate 21, a cladding layer 22, and a first component layer 23. Along as shown... Figure 2B The schematic cross-section shown by line BB is the cross-section of EC 1 in which the tapered waveguide 13 of the ribbed waveguide 12 is arranged. The tapered waveguide 13 of the ribbed waveguide 12 is arranged in the first component layer 23.

[0047] Figure 2C It shows along Figure 1 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line CC in EC 1. Figure 2C The EC 1 shown includes a Si substrate 21, a cladding layer 22, and a first component layer 23. Along as shown... Figure 2C The schematic cross-section shown by line CC is the section of EC 1 in which the channel waveguide 11 is arranged. The channel waveguide 11 is arranged in the first component layer 23.

[0048] In the EC 1 of the first embodiment, a ribbed waveguide 12 is used in a portion of the optical waveguide; therefore, sidewall roughening does not occur, and optical coupling loss and optical reflection caused by light scattering due to sidewall roughening can be prevented. Furthermore, the EC 1 uses a channel waveguide 11 in the portion of the optical waveguide 10 that is coupled to the fiber F, resulting in weaker light confinement and increased mode field. Furthermore, the EC 1 achieves low-loss spot size conversion. Moreover, in the EC 1, even when a channel waveguide 11 is used in the portion coupled to the fiber F, the core width is reduced, thus minimizing the effects caused by sidewall roughening.

[0049] The first embodiment of the ribbed waveguide 12 has been described, in which the planar width of each of the flat sections 12B of the tapered waveguide 13 is constant. However, the embodiment is not limited to this example; for example, the planar width of the tapered waveguide 13 of the ribbed waveguide 12 can gradually decrease from the portion of the flat section 12B connected to the linear waveguide 14 toward the channel waveguide 11, and can be appropriately modified. In this case, the planar width of the tapered waveguide 13 gradually approaches the channel waveguide 11, allowing for a moderate change in the mode field.

[0050] Furthermore, in EC 1 of the first embodiment, a spot size converter including an optical waveguide 10 was described by way of example. This optical waveguide 10 includes a channel waveguide 11 and a ribbed waveguide 12 and is made of Si. However, in some cases, it may be difficult to fully increase the mode field using only the optical waveguide 10 made of Si. Therefore, an embodiment addressing the above situation will be described below as a second embodiment.

[0051] (b) Second Embodiment

[0052] Figure 3 This is a schematic plan view illustrating an example of EC 5 according to the second embodiment. Meanwhile, components identical to those in EC 1 of the first embodiment are indicated by the same reference numerals, and explanations of identical components and operations will be omitted. Figure 3 The EC 5 shown includes a first EC 1A and a second EC 3. Meanwhile, the first EC 1A is EC 1 in the first embodiment, which includes a channel waveguide 11 and a ribbed waveguide 12 connected to the channel waveguide 11.

[0053] The second EC 3 includes a cladding layer 22 made of SiO2 or the like, and a SiN waveguide 30 covered by the cladding layer 22 and made of, for example, Si3N4 (hereinafter referred to as silicon nitride (SiN)). The SiN waveguide 30 includes a first tapered waveguide 31 and a second tapered waveguide 32 connected to the first tapered waveguide 31. The first tapered waveguide 31 has a structure in which the waveguide width gradually increases from the optical input-output unit near the chip end face D1 toward the second tapered waveguide 32. The second tapered waveguide 32 has a structure in which the waveguide width gradually decreases from the portion connected to the first tapered waveguide 31 as it moves away from the first tapered waveguide 31. The second tapered waveguide 32 is referred to as a different tapered waveguide.

[0054] EC 5 includes a transition unit 33 and an inverted conical portion 34. The transition unit 33 allows light to thermally transition between the channel waveguide 11 in the first EC 1A and the second conical waveguide 32 in the SiN waveguide 30 in the second EC 3. The inverted conical portion 34 has a structure in which the waveguide width gradually decreases towards the chip end face D1. The inverted conical portion 34 is the first conical waveguide 31 of the SiN waveguide 30 arranged near the chip end face D1 and guiding the signal light from the optical fiber F1.

[0055] The transition unit 33 includes a channel waveguide 11, a second tapered waveguide 32, and a portion of a tapered waveguide 13, and enables light to transition between the combination of the channel waveguide 11 and a portion of the tapered waveguide 13 and the second tapered waveguide 32. In other words, in the transition unit 33, signal light from the second tapered waveguide 32 transitions to the linear waveguide 14 via the channel waveguide 11 and the ribbed tapered waveguide 13.

[0056] Figure 4A It shows along Figure 3 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line AA in EC 5. Figure 4A The EC 5 shown includes a Si substrate 21, a cladding layer 22, a first component layer 23 disposed on the side close to the Si substrate 21, and a second component layer 24 disposed on the side away from the Si substrate 21. Along as... Figure 4A The schematic cross-section shown by line AA is the cross-section of the first EC 1A in which the linear waveguide 14 of the ribbed waveguide 12 is arranged. The linear waveguide 14 of the ribbed waveguide 12 is arranged in the first component layer 23.

[0057] Figure 4B It shows along Figure 3 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line BB in EC 5. Figure 4B The EC 5 shown includes a Si substrate 21, a cladding layer 22, a first component layer 23, and a second component layer 24. Along as... Figure 4B The schematic cross-section shown by line BB is the cross-section of the transition unit 33 in which the tapered waveguide 13 of the ribbed waveguide 12 is arranged. The tapered waveguide 13 of the ribbed waveguide 12 is arranged in the first component layer 23. The second tapered waveguide 32 of the SiN waveguide 30 is arranged in the second component layer 24. In other words, the second tapered waveguide 32 of the SiN waveguide 30 is arranged in a different layer from the ribbed waveguide 12 at a position where it overlaps with the tapered waveguide 13 of the ribbed waveguide 12 along the planar direction.

[0058] Figure 4C It shows along Figure 3A schematic cross-sectional view of an example of a schematic cross-sectional portion of line CC in EC 5 shown. Figure 4C The EC 5 shown includes a Si substrate 21, a cladding layer 22, a first component layer 23, and a second component layer 24. Along as... Figure 4C The schematic cross-section shown by line CC is the section of transition unit 33 in which the channel waveguide 11 is arranged. The channel waveguide 11 is arranged in the first component layer 23. The second tapered waveguide 32 of the second EC 3 is arranged in the second component layer 24. In other words, the second tapered waveguide 32 of the SiN waveguide 30 is arranged in a different layer from the channel waveguide 11 at the position where it overlaps with the channel waveguide 11 along the planar direction.

[0059] Figure 4D It shows along Figure 3 A schematic cross-sectional view of an example of a schematic cross-sectional portion of line DD in EC 5 shown. Figure 4D The EC 5 shown includes a Si substrate 21, a cladding layer 22, a first component layer 23, and a second component layer 24. Along... Figure 4D The schematic cross-section of line DD shown is the section of the inverted conical portion 34 in which the first conical waveguide 31 is arranged. The first conical waveguide 31 is arranged in the second component layer 24.

[0060] The transition unit 33 includes a channel waveguide 11 made of Si, thus reducing optical confinement compared to the case where only a ribbed waveguide made of Si is included. This effect is particularly significant when the light to be guided is TE light. Therefore, in the transition unit 33, the mode field of the TE light transitioning from the channel waveguide 11 to the SiN waveguide 30 in the second tapered waveguide 32 increases, and the transition efficiency of the TE light from the channel waveguide 11 to the SiN waveguide 30 increases. As a result, the efficiency of the adiabatic conversion of the TE light in the transition unit 33 can be improved.

[0061] In the second embodiment of EC 5, a ribbed waveguide 12 is used as part of the optical waveguide 10 of the first EC 1A; therefore, sidewall roughening does not occur, and optical coupling loss and optical reflection caused by light scattering due to sidewall roughening can be prevented. In the first EC 1A, a channel waveguide 11 is used as the transition portion relative to the second tapered waveguide 32 of the SiN waveguide 30, resulting in weaker light confinement and increased mode field. Furthermore, in the first EC 1A, even when the channel waveguide 11 is used as the transition portion relative to the second tapered waveguide 32, the core width is reduced, thus preventing the effects caused by sidewall roughening.

[0062] For example, when a ribbed waveguide is used instead of the channel waveguide 11 as the transition unit and the TE light transitions from the ribbed waveguide to the second tapered waveguide 32, the optical confinement is enhanced in the ribbed waveguide, resulting in a decrease in the transition efficiency of the TE light and an increase in the loss of the TE light. Conversely, the transition unit 33 according to this embodiment increases the mode field of the TE light transitioning from the channel waveguide 11 to the SiN waveguide 30 via the second tapered waveguide 32. Furthermore, the optical confinement in the channel waveguide 11 is weaker, which allows for a significant improvement in the transition efficiency of the TE light from the channel waveguide 11 to the SiN waveguide 30. Therefore, the efficiency of the adiabatic transition of the TE light in the transition unit 33 can be improved, and the loss of the TE light can be reduced.

[0063] EC 5 allows signal light from fiber F to propagate through transition unit 33 by using an inverted conical portion 34. In transition unit 33, the waveguide widths of the channel waveguide 11 made of Si and the second conical waveguide 32 made of SiN are changed in a conical manner. The second conical waveguide 32 made of SiN has a lower refractive index than the channel waveguide 11 made of Si, allowing for a complete increase in the mode field of the signal light, reducing coupling loss of TE and TM light relative to fiber F, and improving coupling efficiency due to its small polarization dependence.

[0064] Meanwhile, in the ribbed waveguide 12 of the first EC 1A in the second embodiment, the flat plate portion 12B has a constant width. Therefore, in the transition unit 33 including the tapered waveguide 13 and the channel waveguide 11, the flat plate width changes significantly between the tapered waveguide 13 and the channel waveguide 11, which may cause a significant change in the mode field and may result in radiation loss. Therefore, an embodiment that addresses the above situation will be described below as a third embodiment.

[0065] (c) Third implementation method

[0066] Figure 5 This is a schematic plan view illustrating an example of EC 5A according to the third embodiment. Meanwhile, components identical to those in EC 5 of the second embodiment are indicated by the same reference numerals, and explanations of identical components and operations will be omitted. The difference between EC 5 of the second embodiment and EC 5 of the third embodiment is that, although the planar width of the flat plate portion 12B1 of the linear waveguide 14 of the ribbed waveguide 12 is constant, the planar width of the flat plate portion 12B2 of the tapered waveguide 13A of the ribbed waveguide 12 changes continuously.

[0067] The planar width of each of the flat plate portions 12B2 of the tapered waveguide 13A of the ribbed waveguide 12 continuously changes from the portion connected to each of the flat plate portions 12B1 of the linear waveguide 14 toward the channel waveguide 11. The transition unit 33A allows light to thermally transition between the Si-made tapered waveguide 13A and the SiN-made channel waveguide 11 and the second tapered waveguide 32. As a result, the planar width of the flat plate portion 12B2 of the tapered waveguide 13A gradually approaches the channel waveguide 11, thus preventing rapid changes in the mode field.

[0068] Figure 6A It shows along Figure 5 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken by line AA in EC 5A shown. Figure 6A The EC 5A shown includes a Si substrate 21, a cladding layer 22, a first component layer 23, and a second component layer 24. Along as... Figure 6A The schematic cross-section shown by line AA is the cross-section of the first EC 1B in which the linear waveguide 14 of the ribbed waveguide 12 is arranged. The linear waveguide 14 of the ribbed waveguide 12 is arranged in the first component layer 23.

[0069] Figure 6B It shows along Figure 5 A schematic cross-sectional view of an example of a schematic cross-sectional portion taken from line BB in EC 5A shown. Figure 6B The EC 5A shown includes a Si substrate 21, a cladding layer 22, a first component layer 23, and a second component layer 24. Along as... Figure 6B The schematic cross-section shown by line BB is the section of transition unit 33A in which the tapered waveguide 13A of the ribbed waveguide 12 is arranged. The tapered waveguide 13A of the ribbed waveguide 12 is arranged in the first component layer 23. The second tapered waveguide 32 of the SiN waveguide 30 is arranged in the second component layer 24. In other words, the second tapered waveguide 32 of the SiN waveguide 30 is arranged in a different layer from the ribbed waveguide 12 at a position where it overlaps with the tapered waveguide 13A of the ribbed waveguide 12 along the planar direction.

[0070] Figure 6C It shows along Figure 5 A schematic cross-sectional view of an example of a schematic cross-sectional portion of line CC in EC 5A shown. Figure 6C The EC 5A shown includes a Si substrate 21, a cladding layer 22, a first component layer 23, and a second component layer 24. Along as... Figure 6CThe schematic cross-section shown by line CC is the section of transition unit 33A in which the channel waveguide 11 is arranged. The channel waveguide 11 is arranged in the first component layer 23. The second tapered waveguide 32 of the SiN waveguide 30 is arranged in the second component layer 24. In other words, the second tapered waveguide 32 of the SiN waveguide 30 is arranged in a different layer than the ribbed waveguide 12 at the position where it overlaps with the channel waveguide 11 along the planar direction.

[0071] Figure 6D It shows along Figure 5 A schematic cross-sectional view of an example of a schematic cross-sectional portion of line DD in EC 5A shown. Figure 6D The EC 5A shown includes a Si substrate 21, a cladding layer 22, a first component layer 23, and a second component layer 24. Along... Figure 6D The schematic cross-section of line DD shown is the section of the inverted conical portion 34 in which the first conical waveguide 31 is arranged. The first conical waveguide 31 is arranged in the second component layer 24.

[0072] In the third embodiment of EC 5A, the planar width of each of the planar portions 12B2 of the tapered waveguide 13A of the ribbed waveguide 12 gradually decreases from the portion connected to each of the planar portions 12B1 of the linear waveguide 14 toward the channel waveguide 11. In other words, the planar width of the planar portion 12B2 of the tapered waveguide 13A gradually approaches the channel waveguide 11, allowing the change in planar width to be moderate. As a result, the change in the mode field between the tapered waveguide 13A and the channel waveguide 11 is moderate, thus preventing radiation loss.

[0073] Furthermore, in EC 5A, a ribbed waveguide 12 is used as part of the optical waveguide 10; therefore, sidewall roughening does not occur, and optical coupling loss and optical reflection caused by light scattering due to sidewall roughening can be prevented. In the first EC 1B, a channel waveguide 11 is used as a transition section relative to the second tapered waveguide 32 of the SiN waveguide 30, resulting in weaker optical confinement and increased mode field.

[0074] By using the inverted conical portion 34, EC 5A allows signal light from fiber F to propagate through transition unit 33A. In transition unit 33A, the waveguide widths of the channel waveguide 11 made of Si and the second conical waveguide 32 made of SiN are changed in a conical manner. The second conical waveguide 32 made of SiN has a lower refractive index than the channel waveguide 11 made of Si, allowing for a complete increase in the mode field of the signal light, reducing coupling loss of TE and TM light relative to fiber F, and improving coupling efficiency due to its small polarization dependence.

[0075] Meanwhile, in the EC 5A of the third embodiment, a tapered channel waveguide 11 is illustrated by way of example. However, if the waveguide width of the channel waveguide 11 is too large, the coupling loss and optical reflection may increase. Therefore, an embodiment for dealing with the above situation will be described below as the fourth embodiment.

[0076] (d) Fourth embodiment

[0077] Figure 7 is a schematic plan view showing an example of the EC 5B of the fourth embodiment. Meanwhile, components identical to those of the EC 5A of the third embodiment are denoted by the same reference numerals, and the explanation of the same components and the same operations will be omitted. The difference between the EC 5A of the third embodiment and the EC 5B of the fourth embodiment is that a tapered channel waveguide 11A having a waveguide width smaller than that of the tapered channel waveguide 11 is provided.

[0078] In Figure 7 the waveguide length of the channel waveguide 11A of the transition unit 33A1 is represented by Lch, and the waveguide length of the tapered waveguide 13A of the transition unit 33A1 is represented by Lrib. In addition, the waveguide width of the channel waveguide 11A at the starting point of the transition unit 33A1 is represented by w1, and the waveguide width of the channel waveguide 11A in the portion connected to the tapered waveguide 13A of the transition unit 33A1 is represented by w2. In addition, the waveguide width of the tapered waveguide 13A in the portion connected to the linear waveguide 14 at the end point of the transition unit 33A1 is represented by w3.

[0079] The waveguide length Lch of the channel waveguide 11A is set to a specific length such that light can be completely transitioned between the tapered waveguide 13A and the second tapered waveguide 32 through the transition unit 33A1. In addition, the waveguide width w2 of the channel waveguide 11A is set to a specific width that can prevent coupling loss and optical reflection. In addition, the waveguide widths have a specific relationship such that w1 < w2 < w3. In addition, the taper angle α1 of the channel waveguide 11A is set to ((w2 - w1) / Lch). In addition, the taper angle α2 of the tapered waveguide 13A of the rib waveguide 12 is set to ((w3 - w2) / Lrib). The taper angle α1 of the channel waveguide 11A is different from the taper angle α2 of the tapered waveguide 13A.

[0080] Figure 8 is a schematic cross-sectional view showing an example of a schematic cross-sectional portion taken along line A-A in the EC 5B shown in Figure 7 The EC 5B shown in Figure 8 includes a Si substrate 21, a cladding layer 22, a first component layer 23, and a second component layer 24. Along as shown in Figure 8The schematic cross-section shown by line AA is the section of transition unit 33A1 in which the channel waveguide 11A is arranged. The channel waveguide 11A is arranged in the first component layer 23. The second tapered waveguide 32 of the second EC 3 is arranged in the second component layer 24. In other words, the second tapered waveguide 32 of the SiN waveguide 30 is arranged in a different layer from the channel waveguide 11A at the position where it overlaps with the channel waveguide 11A along the planar direction.

[0081] In the fourth embodiment of EC 5B, the transition unit 33A1 sets the waveguide length Lch of the channel waveguide 11A to a specific length required for adiabatic transition, and sets the waveguide width w2 of the channel waveguide 11A to a specific width that can prevent coupling loss and light reflection. Therefore, coupling loss and light reflection in the transition unit 33A1 can be prevented.

[0082] Figure 9 This is a diagram illustrating an example of an optical transceiver 70 according to this embodiment. Figure 9 The optical transceiver 70 shown is connected to an optical fiber on the output side and an optical fiber on the input side. The optical transceiver 70 includes a digital signal processor (DSP) 72 and an optical transceiver 73. The optical transceiver 73 includes an optical transmitter 73A and an optical receiver 73B. The DSP 72 is an electronic component that performs digital signal processing. The DSP 72 performs processing (such as encoding) on ​​the transmitted data, generates an electrical signal including the transmitted data, and outputs the generated electrical signal to the optical transmitter 73A. Furthermore, the DSP 72 acquires an electrical signal including received data from the optical receiver 73B, performs processing such as decoding on the acquired electrical signal, and obtains the received data.

[0083] The optical transmitter 73A includes an optical modulator element 73A1 that modulates the supplied light by an electrical signal output from the DSP 72 and outputs the electrically modulated transmitted light to an optical fiber. The optical modulator element 73A1 incorporates an optical device with a substrate-type optical waveguide element that guides the light output to the optical fiber.

[0084] The optical receiver 73B includes an optical receiver element 73B1 that receives an optical signal from an optical fiber and demodulates the received light using the provided light, converting the demodulated received light into an electrical signal, and outputting the converted electrical signal to the DSP 72. The optical receiver element 73B1 incorporates an optical device with a substrate-type optical waveguide element for guiding the light received from the optical fiber.

[0085] The optical transceiver 70 includes the following optical components: a channel waveguide in which the waveguide width increases in a tapered manner; and a ribbed waveguide connected to the widened side of the channel waveguide and including a rib portion and a planar portion. The ribbed waveguide includes a tapered waveguide in which the rib width increases in a tapered manner with respect to the portion away from the side connected to the channel waveguide. Therefore, optical components capable of improving optical coupling loss and optical reflection can be provided.

[0086] For the sake of simplicity, an example has been described in which an optical transceiver 70 incorporates an optical transmitter 73A and an optical receiver 73B, but the optical transceiver 70 may incorporate either the optical transmitter 73A or the optical receiver 73B. For example, optical devices may be used in the optical transceiver 70 in which the optical receiver 73B is incorporated, and appropriate modifications may be made.

[0087] Furthermore, the components of each unit shown in the accompanying drawings do not always need to be physically configured in the manner shown. In other words, the specific form of distribution and integration of each unit is not limited to those shown in the accompanying drawings, and all or some units can be functionally or physically distributed or integrated in any unit according to various loads or usage conditions.

[0088] Furthermore, all or any part of the various processing functions implemented by the device can be implemented by a central processing unit (CPU) (or a microcomputer, such as a microprocessor unit (MPU) or a microcontroller unit (MCU)). Additionally, all or any part of the various processing functions can be implemented by a program analyzed and executed by the CPU, or by hardware using wired logic.

[0089] From one perspective, optical devices that can improve coupling loss and light reflection can be provided.

Claims

1. An optical device, the optical device comprising: Channel waveguide, the channel waveguide having a waveguide width that increases in a tapered manner; as well as A ribbed waveguide is connected to the side of the channel waveguide where the waveguide width increases, and includes a rib portion and a flat plate portion, wherein... The ribbed waveguide includes a tapered waveguide in which the rib width increases taperingly as it moves away from the side connected to the channel waveguide.

2. The optical device according to claim 1, wherein, The flat plate portion of the tapered waveguide has a plate width that decreases as it approaches the side connected to the channel waveguide.

3. The optical device according to claim 1 or 2, further comprising different tapered waveguides, the different tapered waveguides being arranged in a different layer from the tapered waveguide and the channel waveguide at locations overlapping with a portion of the channel waveguide and the tapered waveguide in the planar direction, and having a waveguide width that increases in a tapered manner from the tapered waveguide toward the channel waveguide.

4. The optical device of claim 3, further comprising a transition portion that allows light to transition between the collection of the channel waveguide and the portion of the tapered waveguide and the different tapered waveguides.

5. The optical device according to claim 4, further comprising an inverted tapered waveguide connected to the side of the different tapered waveguides where the waveguide width increases, and having a waveguide width that decreases in a tapered manner as it moves away from the different tapered waveguides.

6. The optical device according to claim 5, wherein, The channel waveguide and the ribbed waveguide are formed of Si waveguides, and The different tapered waveguides and the inverted tapered waveguide are formed from SiN waveguides.

7. An optical receiver, the optical receiver comprising: An optical receiver element that converts received signal light into an electrical signal, wherein... The optical receiver element includes: A channel waveguide having a waveguide width that increases in a tapered manner; and A ribbed waveguide is connected to the side of the channel waveguide where the waveguide width increases, and has a rib portion and a flat plate portion. The ribbed waveguide includes a tapered waveguide in which the rib width increases taperingly as it moves away from the side connected to the channel waveguide.

8. An optical transmitter, the optical transmitter comprising: An optical modulator element, wherein the optical modulator element modulates guided light according to an electrical signal, wherein the optical modulator element comprises: A channel waveguide having a waveguide width that increases in a tapered manner; and A ribbed waveguide is connected to the side of the channel waveguide where the waveguide width increases, and has a rib portion and a flat plate portion. The ribbed waveguide includes a tapered waveguide in which the rib width increases taperingly as it moves away from the side connected to the channel waveguide.

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