Optical device, optical receiver, and optical transceiver

Abstract

The invention relates to an optical device, an optical receiver and an optical transceiver. An optical device includes: a first edge coupler connected to a polarization multiplexer-demultiplexer and in contact with an end surface; and a second edge coupler connected to the optical mixing circuit and in contact with the end face. The optical device includes: a first tapered portion that guides light from an end face and is included in a first edge coupler; and a second tapered portion that guides light from the end face and is included in the second edge coupler. The second tapered portion has a structure in which a taper angle of the second tapered portion with respect to the end face is smaller than a taper angle of the first tapered portion with respect to the end face.

Description

Technical Field

[0001] The embodiments discussed herein relate to optical devices, optical receivers, and optical transceivers. Background Art

[0002] Fig.11 is a diagram illustrating an example of a conventional optical chip 100. For example, Fig.11 The optical chip 100 shown is an optical IC chip including an optical receiver 110 having a digital coherent function. The optical receiver 110 includes a first edge coupler (EC) 111 arranged in a signal light port for inputting signal light, a second EC 112 arranged in a local oscillation light port for inputting local oscillation light, and a polarization beam splitter (PBS) 113. The optical receiver 110 includes a polarization rotator (PR) 114, a first optical hybrid circuit 115A, a second optical hybrid circuit 115B, a first photodiode (PD) 116A to a fourth photodiode (PD) 116D, and a first output port 117A to a fourth output port 117D. For example, the second EC 112 and the first optical hybrid circuit 115A, the second EC 112 and the second optical hybrid circuit 115B, the first EC 111 and the PBS 113 are connected to an optical waveguide such as a Si waveguide.

[0003] The first EC 111 of the signal light port is formed on the chip end face D11, which is a side surface end in the optical chip 100, and is, for example, an EC connected to a port of the first optical fiber F11 to which an optical signal is input. It is noted that by forming the wafer into a chip, the signal light port is exposed on the chip end face D11 of the optical chip 100. The second EC 112 of the local oscillator light port is formed on the chip end face D11 of the optical chip 100, and is, for example, an EC connected to a port of the second optical fiber F12 to which local oscillator light from a light source is input. It is noted that by forming the wafer into a chip, the local oscillator light port is exposed on the chip end face D11 of the optical chip 100.

[0004] The PBS 113 divides the received light (i.e., the signal light input from the first EC 111) into two cross polarization states, for example, an X polarization wave component as a transverse electric (TE) polarization wave and a Y polarization wave component as a transverse magnetic (TM) polarization wave. The PBS 113 outputs the received light of the X polarization wave component to the first optical hybrid circuit 115A. In addition, the PR 114 performs a 90-degree polarization rotation on the received light of the Y polarization wave component from the PBS 113 to convert the received light into the received light of the Y polarization wave component after the polarization rotation, and outputs the received light to the second optical hybrid circuit 115B.

[0005] The first optical hybrid circuit 115A interferes the received light of the X polarization component with the local oscillator light, and obtains optical signals of the I component and the Q component. It should be noted that the I component is an in-phase component, and the Q component is an orthogonal phase component. The first optical hybrid circuit 115A outputs the optical signal of the I component in the received light of the X polarization component to the first PD 116A. The first optical hybrid circuit 115A outputs the optical signal of the Q component in the received light of the X polarization component to the second PD 116B.

[0006] The second optical hybrid circuit 115B interferes the received light of the Y polarization component with the local oscillation light, and obtains optical signals of the I component and the Q component. The second optical hybrid circuit 115B outputs the optical signal of the I component in the received light of the Y polarization component to the third PD 116C. The second optical hybrid circuit 115B outputs the optical signal of the Q component in the received light of the Y polarization component to the fourth PD 116D.

[0007] The first PD 116A electrically converts the optical signal of the I component of the X polarization component from the first optical hybrid circuit 115A, adjusts the gain, and then outputs the electrical signal after the gain adjustment to the first output port 117A. The second PD 116B electrically converts the optical signal of the Q component of the X polarization component from the first optical hybrid circuit 115A, adjusts the gain, and then outputs the electrical signal after the gain adjustment to the second output port 117B.

[0008] The third PD 116C electrically converts the optical signal of the I component of the Y polarization component from the second optical hybrid circuit 115B, adjusts the gain, and then outputs the gain-adjusted electrical signal to the third output port 117C. The fourth PD 116D electrically converts the optical signal of the Q component of the Y polarization component from the second optical hybrid circuit 115B, adjusts the gain, and then outputs the gain-adjusted electrical signal to the fourth output port 117D.

[0009] Fig.12 is a plan view schematically illustrating an example of an EC portion in the optical chip 100 . Fig.12 The EC portion shown is a portion of a plate-type optical waveguide device optically connected to the core C of the optical fiber. The EC portion includes a first EC 111 of a signal light port and a second EC 112 of a local oscillator light port. The received light contains TE light and TM light, so the first EC 111 guides the TE light and the TM light. The local oscillator light is TE light, so the second EC 112 guides the TE light. It is to be noted that the second EC 112 has the same construction as that of the first EC 111 and is assigned the same reference numerals, so the description of the redundant construction and operation will be omitted.

[0010] The first EC 111 includes a clad body 121 formed of SiO2 or the like, and a first waveguide 122 covered with the clad body 121, the first waveguide 122 being formed of, for example, Si3N4 (hereinafter referred to as SiN (silicon nitride)). The first EC 111 includes: a second waveguide 123, which is covered with the clad body 121 and formed of, for example, Si or the like; and a heat-insulating conversion portion 124 in which light is optically converted between the first waveguide 122 and the second waveguide 123 in a heat-insulating manner. In addition, the first EC 111 has an inverse tapered portion 125 having a structure in which the waveguide width of the first waveguide 122 to the chip end face D11 gradually decreases.

[0011] The first waveguide 122 includes a first tapered waveguide 122A and a second tapered waveguide 122B connected to the first tapered waveguide 122A. The first tapered waveguide 122A has a structure in which the waveguide width gradually increases from the optical input and output portion close to the chip end face D11 to the starting point. The second tapered waveguide 122B has a structure in which a portion connected to the starting point of the first tapered waveguide 122A serves as the starting point, and the waveguide width gradually decreases as it is separated from the starting point of the first tapered waveguide 122A.

[0012] The second waveguide 123 includes: a third tapered waveguide 123A arranged in a position such that at least a portion of the third tapered waveguide 123A overlaps with the second tapered waveguide 122B in a planar direction; and a liner waveguide 123B connected to the third tapered waveguide 123A. The third tapered waveguide 123A has a structure in which the waveguide width gradually increases as it separates from the starting point of the second tapered waveguide 122B. The liner waveguide 123B is a waveguide connected to the side of the third tapered waveguide 123A where the waveguide width is wider.

[0013] Fig.13A is an example of Fig.12 An illustration of an example of a schematic cross-sectional portion of the first EC 111 taken along line AA is shown. Fig.13A The illustrated first EC 111 includes a Si substrate 131 , an encapsulation body 121 , a first assembly layer 141A disposed on a side away from the Si substrate 131 , and a second assembly layer 141B disposed on a side close to the Si substrate 131 . Fig.13A The cross-sectional portion shown taken along line AA is a cross-sectional portion of the first EC 111 in which the liner waveguide 123B is arranged. The liner waveguide 123B in the second waveguide 123 is arranged in the second assembly layer 141B.

[0014] Fig. 13B is an example of Fig.12 2 is a diagram illustrating an example of a schematic cross-sectional portion of the first EC 111 taken along line BB shown in FIG. Fig. 13BThe first EC 111 shown in FIG. 1 includes a Si substrate 131 , an encapsulation body 121 , a first assembly layer 141A, and a second assembly layer 141B. Fig. 13B The schematic cross-sectional portion taken along line BB shown in FIG. 1 is a cross-sectional portion of the first EC 111 in which the adiabatic conversion portion 124 is arranged. The third tapered waveguide 123A of the second waveguides 123 is arranged in the second assembly layer 141B. The second tapered waveguide 122B of the first waveguide 122 is arranged in the first assembly layer 141A.

[0015] Fig. 13C is an example of Fig.12 An illustration of an example of a schematic cross-sectional portion of the first EC 111 taken along line CC is shown. Fig. 13C The illustrated first EC 111 includes a Si substrate 131 and an encapsulation body 121 laminated on the Si substrate 131 . Fig. 13C The schematic cross-sectional portion shown along line CC is a cross-sectional portion of the first EC 111 in which the reverse tapered portion 125 is arranged. In addition, the first EC 111 includes a first assembly layer 141A and a second assembly layer 141B. A first tapered waveguide 122A in the first waveguide 122 is arranged in the first assembly layer 141A.

[0016] The configuration of the adiabatic conversion portion 124 and the reverse tapered portion 125 of the first EC 111 is the same as that of the second EC 112, and has the same waveguide width, waveguide length, and waveguide thickness.

[0017] Fig.12 The first EC 111 shown guides the received light from the first optical fiber F11 to the adiabatic conversion portion 124 using the reverse tapered portion 125. In the adiabatic conversion portion 124, the waveguide widths of the first waveguide 122 and the second waveguide 123 become tapered. The first waveguide 122 has a lower refractive index than that of the second waveguide 123, so it is possible to increase the mode field of the received light and reduce the coupling loss with the first optical fiber F11.

[0018] The second EC 112 guides the local oscillation light from the second optical fiber F12 to the adiabatic conversion portion 124 using the inverted tapered portion 125. In the adiabatic conversion portion 124, the waveguide widths of the first waveguide 122 and the second waveguide 123 become tapered. The first waveguide 122 has a lower refractive index than that of the second waveguide 123, so it is possible to increase the mode field of the local oscillation light and reduce the connection loss with the second optical fiber F12.

[0019] Patent Document 1: U.S. Patent Application Publication No. 2005 / 0185893

[0020] Patent Document 2: U.S. Patent Application Publication No. 2018 / 0321445

[0021] Patent Document 3: Japanese Publication of International Patent Application No. 2008-530615

[0022] Patent Document 4: Japanese Publication of International Patent Application No. 2006-517673

[0023] However, in EC, in order to reduce the connection loss with the optical fiber, the waveguide needs to have an appropriate waveguide width on the chip end face D11. Fig.12 When the waveguide width of the inverted tapered portion 125 increases in a tapered form from the chip end face D11, the waveguide width of the first waveguide 122 on the chip end face D11 is different from the designed value due to the deviation from the tolerance of the dicing line DL when the wafer is diced or polished. As a result, in the EC, the connection loss with the optical fiber increases due to the deviation from the tolerance caused by dicing or polishing.

[0024] When the cutting position is due to Fig.12 When the waveguide length of the inverted tapered portion 125 of the second EC 112 is reduced and the waveguide width of the inverted tapered portion 125 on the chip end face D11 side is shifted in the left direction in the figure due to the deviation of the tolerance of the cutting line DL in the second EC 112, the waveguide width of the inverted tapered portion 125 on the chip end face D11 side is increased. As a result, the connection loss with the core C of the second optical fiber F12 is increased, and the loss of the TE light guided in the second EC 112 is increased. Specifically, the local oscillation light guided in the second EC 112 of the local oscillation light port is TE light, and therefore the loss of the TE light is significant compared to the first EC 111.

[0025] Therefore, an object in one aspect of an embodiment of the present invention is to provide an optical device or the like capable of reducing the connection loss between a second EC and a second optical fiber on the local oscillator optical port side due to a deviation in tolerance in cutting. Summary of the invention

[0026] According to one aspect of the embodiment, an optical device includes: a first edge coupler, a second edge coupler, a first tapered portion, and a second tapered portion. The first edge coupler is connected to a polarization multiplexer-demultiplexer and is in contact with an end face. The second edge coupler is connected to an optical hybrid circuit and is in contact with the end face. The first tapered portion guides light from the end face and is included in the first edge coupler. The second tapered portion guides light from the end face and is included in the second edge coupler. The second tapered portion has a structure in which a taper angle of the second tapered portion relative to the end face is smaller than a taper angle of the first tapered portion relative to the end face. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1is a diagram illustrating an example of an optical chip of the present example;

[0028] Figure 2 is a schematic plan view illustrating an example of an EC portion in the optical chip of Example 1;

[0029] Figure 3A is an example of Figure 2 An illustration of an example of a schematic cross-sectional portion of a second EC taken along line AA shown in FIG.

[0030] Figure 3B is an example of Figure 2 An illustration of an example of a schematic cross-sectional portion of a second EC taken along line BB shown in FIG.

[0031] Figure 3C is an example of Figure 2 An illustration of an example of a schematic cross-sectional portion of a second EC taken along line CC shown in FIG.

[0032] Figure 4A is a diagram illustrating an example of the relationship between the cutting position and the light loss with respect to each tapered length of the second reverse tapered portion;

[0033] Figure 4B is a diagram illustrating an example of the relationship between the cutting position and the light loss with respect to each tapered length of the first inverse tapered portion;

[0034] Figure 5 is a schematic plan view illustrating an example of an EC portion in an optical chip of Example 2;

[0035] Figure 6 is a schematic plan view illustrating an example of an EC portion in an optical chip of Example 3;

[0036] Figure 7 is a schematic plan view illustrating an example of an EC portion in an optical chip of Example 4;

[0037] Fig. 8A is an example of Figure 7 An illustration of an example of a schematic cross-sectional portion of a second EC taken along line AA shown in FIG.

[0038] Figure 8B is an example of Figure 7 An illustration of an example of a schematic cross-sectional portion of a second EC taken along line BB shown in FIG.

[0039] Figure 8C is an example of Figure 7 An illustration of an example of a schematic cross-sectional portion of a second EC taken along line CC shown in FIG.

[0040] Fig. 9is a schematic plan view illustrating an example of an EC portion in an optical chip of Example 5;

[0041] Fig.10 is a diagram illustrating an example of an optical transceiver of the present example;

[0042] Fig.11 is a diagram illustrating an example of a conventional optical chip;

[0043] Fig.12 is a plan view schematically illustrating an example of an EC portion in an optical chip;

[0044] Fig.13A is an example of Fig.12 An illustration of an example of a schematic cross-sectional portion of a first EC taken along line AA shown in FIG.

[0045] Fig. 13B is an example of Fig.12 an illustration of an example of a schematic cross-sectional portion of the first EC taken along line BB shown in ; and

[0046] Fig. 13C is an example of Fig.12 0047 is a diagram of an example of a schematic cross-sectional portion of a first EC taken along line CC shown in FIG. DETAILED DESCRIPTION

[0047] Preferred embodiments of the present invention will be described with reference to the accompanying drawings. It is to be noted that the embodiments do not limit the present disclosure. It is to be noted that the examples shown below can be appropriately combined within the range not causing inconsistency.

[0048] (a) Example 1

[0049] Figure 1 is a diagram illustrating an example of the optical chip 1 of this example. For example, Figure 1 The optical chip 1 shown is an optical IC chip of an optical receiver 10 including a digital coherent function. The optical receiver 10 includes a first edge coupler (EC) 11 arranged in a signal light port of an input signal light, a second EC 12 arranged in a local oscillator light port of an input local oscillator light, a polarization beam splitter (PBS) 13, and a polarization rotator (PR) 14. The optical receiver 10 includes a first optical hybrid circuit 15A, a second optical hybrid circuit 15B, a first photodiode (PD) 16A to a fourth photodiode (PD) 16D, and a first output port 17A to a fourth output port 17D. For example, the second EC 12 and the first optical hybrid circuit 15A, the second EC 12 and the second optical hybrid circuit 15B, the first EC 11, and the PBS 13 are connected to an optical waveguide (such as a Si waveguide).

[0050] The first EC 11 of the signal light port is formed on the chip end face D1 which is the side surface end in the optical chip 1, and is, for example, an EC connected to a port of the first optical fiber F1, to which the received light as the optical signal is input. It is to be noted that by forming the wafer into a chip, the signal light port is exposed on the chip end face D1 of the optical chip 1. The second EC 12 of the local oscillator light port is formed on the chip end face D1 of the optical chip 1, and is, for example, an EC connected to a port of the second optical fiber F2, to which the local oscillator light from the light source is input. It is to be noted that by forming the wafer into a chip, the local oscillator light port is exposed on the chip end face D1 of the optical chip 1.

[0051] The PBS 13 is a polarization multiplexer-demultiplexer, which divides the received light input from the first EC 11 into two crossed polarization states, for example, the received light of the X polarization wave component as a transverse electric (TE) polarization wave, and the received light of the Y polarization wave component as a transverse magnetic (TM) polarization wave. The PBS 13 outputs the received light of the X polarization wave component from the received light to the first optical hybrid circuit 15A. In addition, the PR 14 performs a 90-degree polarization rotation on the received light of the Y polarization wave component from the PBS 13 to convert the received light into the received light of the Y polarization wave component after the polarization rotation, and outputs the received light to the second optical hybrid circuit 15B.

[0052] The first optical hybrid circuit 15A interferes the received light of the X polarization component with the local oscillator light, and obtains the optical signals of the I component and the Q component. It should be noted that the I component is the in-phase component, and the Q component is the orthogonal phase component. The first optical hybrid circuit 15A outputs the optical signal of the I component in the received light of the X polarization component to the first PD 16A. The first optical hybrid circuit 15A outputs the optical signal of the Q component in the received light of the X polarization component to the second PD 16B.

[0053] The second optical hybrid circuit 15B interferes the received light of the Y polarization component with the local oscillation light, and obtains optical signals of the I component and the Q component. The second optical hybrid circuit 15B outputs the optical signal of the I component in the received light of the Y polarization component to the third PD 16C. The second optical hybrid circuit 15B outputs the optical signal of the Q component in the received light of the Y polarization component to the fourth PD 16D.

[0054] The first PD 16A electrically converts the optical signal of the I component of the X polarization component from the first optical hybrid circuit 15A, adjusts the gain, and then outputs the gain-adjusted electrical signal to the first output port 17A. The second PD 16B electrically converts the optical signal of the Q component of the X polarization component from the first optical hybrid circuit 15A, adjusts the gain, and then outputs the gain-adjusted electrical signal to the second output port 17B.

[0055] The third PD 16C electrically converts the optical signal of the I component of the Y polarization component from the second optical hybrid circuit 15B, adjusts the gain, and then outputs the gain-adjusted electrical signal to the third output port 17C. The fourth PD 16D electrically converts the optical signal of the Q component of the Y polarization component from the second optical hybrid circuit 15B, adjusts the gain, and then outputs the gain-adjusted electrical signal to the fourth output port 17D.

[0056] Figure 2 is a plan schematic diagram illustrating an example of an EC portion in the optical chip 1 . Figure 2 The EC section shown is an EC of a plate-type optical waveguide device optically connected to the core C of the optical fiber. The EC section includes a first EC 11 of a signal light port and a second EC 12 of a local oscillator light port. The received light contains TE light and TM light, so the first EC 11 guides the TE light and TM light. The local oscillator light is TE light, so the second EC 12 guides the TE light.

[0057] The first EC 11 includes a cladding 21 formed of SiO2 or the like and a first waveguide 22 covered with the cladding 21 and formed of, for example, Si3N4 (hereinafter referred to as SiN (silicon nitride)) or the like. The first EC 11 includes: a second waveguide 23 covered with the cladding 21 and formed of, for example, Si or the like; and a first thermal insulation conversion portion 24 that optically converts light in a thermal insulation manner between the first waveguide 22 and the second waveguide 23. In addition, the first EC 11 has a first inverted tapered portion 25 having a structure in which the waveguide width of the first waveguide 22 to the chip end face D1 gradually decreases. The first inverted tapered portion 25 is a first tapered portion that is included in the first EC 11 and guides the received light from the first optical fiber F1 connected to the chip end face D1.

[0058] The first waveguide 22 includes a first tapered waveguide 22A and a second tapered waveguide 22B connected to the first tapered waveguide 22A. The first tapered waveguide 22A has a structure in which the waveguide width gradually increases from the light input and output portion close to the chip end face D1 to the starting point. The second tapered waveguide 22B has a structure in which a portion connected to the starting point of the first tapered waveguide 22A serves as a starting point and the waveguide width gradually decreases as it leaves the starting point of the first tapered waveguide 22A.

[0059] The second waveguide 23 includes: a third tapered waveguide 23A arranged at a position such that at least a portion of the third tapered waveguide 23A overlaps with the second tapered waveguide 22B in a planar direction; and a liner waveguide 23B connected to the third tapered waveguide 23A. The third tapered waveguide 23A has a structure in which the waveguide width gradually increases as it separates from the starting point of the second tapered waveguide 22B. The liner waveguide 23B is a waveguide connected to the side of the third tapered waveguide 23A where the waveguide width is wider.

[0060] The second EC 12 includes a clad 21 formed of SiO2 or the like and a third waveguide 32 covered with the clad 21 and formed of, for example, SiN or the like. The second EC 12 includes: a fourth waveguide 33 covered with the clad 21 and formed of, for example, Si or the like; and a second adiabatic conversion portion 34 that optically converts light in an adiabatic manner between the third waveguide 32 and the fourth waveguide 33. In addition, the second EC 12 has a second inverted tapered portion 35 having a structure in which the waveguide width of the third waveguide 32 to the chip end face D1 gradually decreases. The second inverted tapered portion 35 is a second tapered portion included in the second EC 12 and guiding the local oscillation light from the second optical fiber F2 connected to the chip end face D1.

[0061] The third waveguide 32 includes a fourth tapered waveguide 32A and a fifth tapered waveguide 32B connected to the fourth tapered waveguide 32A. The fourth tapered waveguide 32A has a structure in which the waveguide width gradually increases from the optical input-output portion close to the chip end face D1 to the starting point. The fifth tapered waveguide 32B has a structure in which a portion connected to the starting point of the fourth tapered waveguide 32A serves as the starting point, and the waveguide width gradually decreases as it is separated from the starting point of the fourth tapered waveguide 32A.

[0062] The fourth waveguide 33 includes: a sixth tapered waveguide 33A arranged at a position such that at least a portion of the sixth tapered waveguide 33A overlaps with the fifth tapered waveguide 32B in a planar direction; and a liner waveguide 33B connected to the sixth tapered waveguide 33A. The sixth tapered waveguide 33A has a structure in which the waveguide width gradually increases as it separates from the starting point of the fifth tapered waveguide 32B. The liner waveguide 33B is a waveguide connected to the side of the sixth tapered waveguide 33A where the waveguide width is wider.

[0063] Figure 3A is an example of Figure 2 2 is a diagram illustrating an example of a schematic cross-sectional portion of the second EC 12 taken along line AA shown in FIG. Figure 3A The second EC 12 shown includes a Si substrate 41 , a package 121 , a first assembly layer 42A disposed on a side away from the Si substrate 41 , and a second assembly layer 42B disposed on a side close to the Si substrate 41 . Figure 3A The cross-sectional portion shown taken along the line AA is a cross-sectional portion of the second EC 12 in which the liner waveguide 33B is arranged. The liner waveguide 33B in the fourth waveguide 33 is arranged in the second assembly layer 42B.

[0064] Figure 3B is an example of Figure 2 An illustration of an example of a schematic cross-sectional portion of the second EC 12 taken along line BB is shown. Figure 3BThe second EC 12 shown includes a Si substrate 41, an encapsulation body 21, a first assembly layer 42A, and a second assembly layer 42B. Figure 3B The schematic cross-sectional portion shown along line BB is a cross-sectional portion of the second EC 12 where the second adiabatic conversion portion 34 is arranged. The sixth tapered waveguide 33A of the fourth waveguides 33 is arranged in the second assembly layer 42B. The fifth tapered waveguide 32B of the third waveguide 32 is arranged in the first assembly layer 42A.

[0065] Figure 3C is along Figure 2 2 is a diagrammatic illustration of an example of a schematic cross-sectional portion of the second EC 12 taken along line CC shown in FIG. Figure 3C The second EC 12 shown in FIG. 1 includes a Si substrate 41 and an encapsulation body 21 laminated on the Si substrate 41 . Figure 3C The schematic cross-sectional portion taken along line CC shown in FIG. 1 is a cross-sectional portion of the second EC 12 arranged with the second reverse tapered portion 35. Furthermore, the second EC 12 includes a first assembly layer 42A and a second assembly layer 42B. The fourth tapered waveguide 32A in the third waveguide 32 is arranged in the first assembly layer 42A.

[0066] The size of the waveguide length of the second adiabatic conversion portion 34 of the second EC 12 that guides only TE light is equal to the size of the waveguide length of the first adiabatic conversion portion 24 of the first EC 11 that guides both TE light and TM light. However, the taper angle of the second inverted tapered portion 35 of the second EC 12 relative to the chip end face D1 is smaller than the taper angle of the first inverted tapered portion 25 of the first EC 11 relative to the chip end face D1. The waveguide length (taper length) of the second inverted tapered portion 35 is longer than the waveguide length (taper length) of the first inverted tapered portion 25. The waveguide width of the second inverted tapered portion 35 on the chip end face D1 side is narrower than the waveguide width of the first inverted tapered portion 25 on the chip end face D1 side.

[0067] Figure 4A 3 is a diagram illustrating an example of the relationship between the cutting position and the optical loss for each tapered length of the second inverse tapered portion 35. When the cutting position between the wafer and the optical chip 1 is 0 (no offset), the loss of TE light is 0.8 dB, and when Figure 2 When the cutting position is shifted to the left by 20 μm and the cone length of the second inverse tapered portion 35 is reduced to 60 μm, the loss of TE light increases to 1.2 dB. Figure 2 When the middle cutting position is shifted to the right and the tapered length of the second inverse tapered portion 35 is increased to 120 μm, the loss of TE light is slightly increased.

[0068] Figure 4Bis a diagram illustrating an example of the relationship between the cutting position and the light loss with respect to each tapered length of the first reverse tapered portion 25. Figure 2 When the cutting position between the wafer and the optical chip 1 is shifted to the right and the taper length of the first inverse tapered portion 25 is increased to 120 μm, the loss of TM light increases to 1.5 dB. Figure 2 When the middle cutting position is shifted to the left and the taper length of the first inverse tapered portion 25 is reduced to 60 μm, the loss of TM light can be suppressed to 1.1 dB. Therefore, the taper length of the second inverse tapered portion 35 is 120 μm and the taper length of the first inverse tapered portion 25 is 60 μm shorter than the taper length of the second inverse tapered portion 35, so that the increase in optical loss due to the cutting shift can be suppressed.

[0069] Figure 2 The first EC 11 shown guides the received light from the first optical fiber F1 to the first adiabatic conversion portion 24 using the first inverse tapered portion 25. In the first adiabatic conversion portion 24, the waveguide widths of the first waveguide 22 and the second waveguide 23 become tapered. The first waveguide 22 has a lower refractive index than that of the second waveguide 23, and thus can increase the mode field of the received light and reduce the coupling loss with the first optical fiber F1.

[0070] The second EC 12 guides the local oscillation light from the second optical fiber F2 to the second adiabatic conversion portion 34 using the second inverse tapered portion 35. In the second adiabatic conversion portion 34, the waveguide widths of the third waveguide 32 and the fourth waveguide 33 are tapered. The third waveguide 32 has a lower refractive index than that of the fourth waveguide 33, and thus can increase the mode field of the local oscillation light and reduce the connection loss with the second optical fiber F2.

[0071] The taper angle of the second inverted tapered portion 35 of the second EC 12 relative to the chip end face D1 is smaller than the taper angle of the first inverted tapered portion 25 of the first EC 11 relative to the chip end face D1. The waveguide length (taper length) of the second inverted tapered portion 35 is longer than the waveguide length (taper length) of the first inverted tapered portion 25. The waveguide width of the second inverted tapered portion 35 on the chip end face D1 side is narrower than the waveguide width of the first inverted tapered portion 25 on the chip end face D1 side. As a result, it is possible to reduce the connection loss between the second EC 12 and the second optical fiber F2 due to deviation from the tolerance in cutting, and realize an EC with high tolerance to deviation from the tolerance in cutting.

[0072] It is to be noted that the case where the taper angle of the second inverse tapered portion 35 with respect to the chip end face D1 is smaller than the taper angle of the first inverse tapered portion 25 with respect to the chip end face D1 and the taper length of the second inverse tapered portion 35 is longer than the taper length of the first inverse tapered portion 25 in Example 1 has been exemplified. However, regardless of the taper length of the second inverse tapered portion 35, the same effect can be obtained by simply setting the taper angle of the second inverse tapered portion 35 with respect to the chip end face D1 to be smaller than the taper angle of the first inverse tapered portion 25 with respect to the chip end face D1. Moreover, in this case, since the waveguide width of the second inverse tapered portion 35 on the chip end face D1 side is narrower than the waveguide width of the first inverse tapered portion 25 on the end face D1 side, the connection loss with the core C of the second optical fiber F2 is reduced, so that the loss of the TE light guided in the second EC 12 can be reduced. Therefore, the connection loss between the second EC 12 and the second optical fiber F2 caused by the deviation from the tolerance in cutting can be reduced, and an EC with high tolerance to the deviation from the tolerance in cutting can be achieved.

[0073] When the deviation from the tolerance of the cutting line DL causes Figure 2 When the middle cutting position is shifted in the right direction so that the waveguide length of the first inverted tapered portion 25 of the first EC 11 increases, the portion of the waveguide width of the first inverted tapered portion 25 on the chip end face D1 side continues to lengthen. The confinement of the TM light guided in the first EC 11 is lower than that of the TE light, and the portion of the waveguide width of the first inverted tapered portion 25 on the chip end face D1 side continues to lengthen so that the loss of the TM light increases. An embodiment for handling this situation will be described below as Example 2.

[0074] (b) Example 2

[0075] Figure 5 1 is a plan schematic diagram illustrating an example of the EC portion in the optical chip 1A of Example 2. It is to be noted that the same construction as that of the optical chip 1 of Example 1 is assigned the same reference numerals, and thus descriptions of redundant constructions and operations will be omitted. The optical chip 1A differs from the optical chip 1 of Example 1 in that the endpoint of the second inverted tapered portion 35 is not the chip end face D1, and a second additional portion 52 is arranged between the endpoint of the second inverted tapered portion 35 and the chip end face D1. Another difference is that the endpoint of the first inverted tapered portion 25 is not the chip end face D1, and a first additional portion 51 is arranged between the endpoint of the first inverted tapered portion 25 and the chip end face D1.

[0076] The first additional portion 51 is a liner waveguide that optically couples the first inverted tapered portion 25 and the core C of the first optical fiber F1 and guides the received light from the core C of the first optical fiber F1, and is a part of the first waveguide 22. The waveguide width of the first additional portion 51 is equal to the waveguide width of the first inverted tapered portion 25 at the end point side. Even if the cutting position is offset, the first additional portion 51 allows the cutting position to be offset within the range of the waveguide length of the first additional portion 51. When the offset of the cutting is within the first additional portion 51, the offset has no effect on the waveguide width in the end point of the first inverted tapered portion 25.

[0077] The second additional portion 52 is a liner waveguide that optically connects the second inverted tapered portion 35 and the core C of the second optical fiber F2, guides the local oscillation light from the core C of the second optical fiber F2, and is a part of the third waveguide 32. The waveguide width of the second additional portion 52 is equal to the waveguide width of the second inverted tapered portion 35 at the end point side. Even if the cutting position is offset, the second additional portion 52 allows the cutting position to be offset within the range of the waveguide length of the second additional portion 52. When the offset of the cutting is within the second additional portion 52, the offset has no effect on the waveguide width in the end point of the second inverted tapered portion 35. The waveguide length of the first additional portion 51 is equal to the waveguide length of the second additional portion 52.

[0078] Figure 5 The first EC 11 shown guides the received light from the first optical fiber F1 to the first inverted tapered portion 25 using the first additional portion 51, and guides the received light to the first adiabatic conversion portion 24 using the first inverted tapered portion 25. In the first adiabatic conversion portion 24, the waveguide widths of the first waveguide 22 and the second waveguide 23 become tapered forms. The first waveguide 22 has a lower refractive index than that of the second waveguide 23, so that the mode field of the received light can be increased and the coupling loss with the first optical fiber F1 can be reduced.

[0079] The second EC 12A guides the local oscillation light from the second optical fiber F2 to the second inverse tapered portion 35 using the second additional portion 52, and guides the local oscillation light from the second optical fiber F2 using the second inverse tapered portion 35. In the second heat-insulating conversion portion 34, the waveguide widths of the third waveguide 32 and the fourth waveguide 33 are changed into a tapered form. The third waveguide 32 has a lower refractive index than that of the fourth waveguide 33, and thus can increase the mode field of the local oscillation light and reduce the connection loss with the second optical fiber F2.

[0080] The taper angle of the second inverted tapered portion 35 of the second EC 12A relative to the chip end face D1 is smaller than the taper angle of the first inverted tapered portion 25 of the first EC 11 relative to the chip end face D1. The waveguide length (taper length) of the second inverted tapered portion 35 is longer than the waveguide length (taper length) of the first inverted tapered portion 25. As a result, the waveguide width of the second inverted tapered portion 35 on the chip end face D1 side is narrower than the waveguide width of the first inverted tapered portion 25 on the chip end face D1 side, so the connection loss with the core C of the second optical fiber F2 is reduced, which makes it possible to reduce the loss of the TE light guided in the second EC 12A.

[0081] Furthermore, the waveguide width of the second additional portion 52 is equal to the waveguide width of the second inverse tapered portion 35 on the chip end face D1 side, and the waveguide width of the first additional portion 51 is equal to the waveguide width of the first inverse tapered portion 25 on the chip end face D1 side. As a result, even if a cutting position shift occurs within the waveguide length range of the first additional portion 51 and the second additional portion 52, the waveguide width of the first inverse tapered portion 25 on the chip end face D1 side and the waveguide width of the second inverse tapered portion 35 on the chip end face D1 side can be prevented from changing due to the shift in the cutting position. As a result, the connection loss between the second EC 12A and the second optical fiber F2 due to the deviation from the tolerance in cutting can be reduced, and an EC with high tolerance to the deviation from the tolerance in cutting can be realized.

[0082] For the second additional portion 52 of Example 2, the case where the waveguide width of the second inverse tapered portion 35 on the chip end face D1 side is narrower than the waveguide width of the first inverse tapered portion 25 on the chip end face D1 side has been exemplified. However, the waveguide width of the second inverse tapered portion 35 on the chip end face D1 side may be equal to the waveguide width of the first inverse tapered portion 25, and may be appropriately changed.

[0083] It is to be noted that, for the optical chip 1A of Example 2, the case where the cutting position is shifted and the waveguide length of the first additional portion 51 and the second additional portion 52 is reduced has been exemplified, and the case where the cutting position is shifted and the waveguide length of the first additional portion 51 and the second additional portion 52 is increased is also conceivable. When the cutting position is shifted and the waveguide length of the first additional portion 51 and the second additional portion 52 is increased, the optical loss in the first additional portion 51 guiding the TM light increases. This is because the wavelength width of the first additional portion 51 is narrower than the waveguide width of the first inverse tapered portion 25, the confinement of the light is low, and the propagation loss of the TM light increases.

[0084] An implementation for handling this situation will be described below as Example 3.

[0085] (c) Example 3

[0086] Figure 61 is a plan view schematically illustrating an example of an EC portion in an optical chip 1B of Example 3. It is noted that the same reference numerals are assigned to the same configurations as those of the optical chip 1A of Example 2, and thus descriptions of redundant configurations and operations will be omitted. The optical chip 1B of Example 3 is different from the optical chip 1A of Example 2 in that the waveguide length of the first additional portion 51A is shorter than the waveguide length of the second additional portion 52.

[0087] In the optical chip 1B of Example 3, even when the cutting position is shifted toward the wafer side and the waveguide lengths of the first additional portion 51A and the second additional portion 52 are increased, the waveguide length of the first additional portion 51A that guides the TM light can be shorter than the waveguide length of the second additional portion 52. As a result, the loss of the TM light in the first additional portion 51A that guides the TM light can be suppressed.

[0088] For the optical chip 1 of Example 1, the case where the taper length of the second inverse tapered portion 35 is longer than the taper length of the first inverse tapered portion 25 is exemplified; however, the optical chip is not limited thereto, and an embodiment thereof will be described below as Example 4.

[0089] (d) Example 4

[0090] Figure 7 1 is a plan view schematically illustrating an example of an EC portion in an optical chip 1C of Example 4. It is noted that the same reference numerals are assigned to the same configurations as those of the optical chip 1 of Example 1, and thus descriptions of redundant configurations and operations will be omitted. The optical chip 1C of Example 4 is different from the optical chip 1 of Example 1 in that, instead of including the second inverted tapered portion 35, it includes a third inverted tapered portion 35A, and the third inverted tapered portion 35A includes an eighth tapered waveguide 32A11 and a ninth tapered waveguide 32A12 having different tapered angles.

[0091] The third inverse tapered portion 35A includes an eighth tapered waveguide 32A11 and a ninth tapered waveguide 32A12 connected to the eighth tapered waveguide 32A11. The eighth tapered waveguide 32A11 has a structure in which the waveguide width gradually increases from the chip end face D1 toward the starting point of the eighth tapered waveguide 32A11. The ninth tapered waveguide 32A12 has a structure in which a portion connected to the starting point of the eighth tapered waveguide 32A11 serves as the starting point of the ninth tapered waveguide 32A12, and the waveguide width gradually increases as it separates from the starting point of the eighth tapered waveguide 32A11. In the ninth tapered waveguide 32A12, an end point of the ninth tapered waveguide 32A12 is connected to the fifth tapered waveguide 32B in the second adiabatic conversion portion 34. The taper angle of the eighth tapered waveguide 32A11 with respect to the chip end face D1 is smaller than the taper angle of the ninth tapered waveguide 32A12 with respect to the chip end face D1 at the starting point of the eighth tapered waveguide 32A11. As a result, the taper length (waveguide length) of the third inverse tapered portion 35A can be shorter than Figure 2 The taper length (waveguide length) of the second inverse tapered portion 35 is shown.

[0092] Fig. 8A is an example of Figure 7 An illustration of an example of a schematic cross-sectional portion of the second EC 12C taken along line AA is shown. Fig. 8A The second EC 12C shown includes a Si substrate 41, a package 21, a first assembly layer 42A, and a second assembly layer 42B. Fig. 8A The cross-sectional portion shown taken along the line AA is a cross-sectional portion of the second EC 12C in which the liner waveguide 33B is arranged. The liner waveguide 33B in the fourth waveguide 33 is arranged in the second assembly layer 42B.

[0093] Figure 8B is an example of Figure 7 An illustration of an example of a schematic cross-sectional portion of the second EC 12C taken along line BB is shown. Figure 8B The second EC 12C shown includes a Si substrate 41, a package 21, a first assembly layer 42A, and a second assembly layer 42B. Figure 8B The schematic cross-sectional portion shown along line BB is a cross-sectional portion of the second EC 12C where the second adiabatic conversion portion 34 is arranged. The sixth tapered waveguide 33A of the fourth waveguides 33 is arranged in the second assembly layer 42B. The fifth tapered waveguide 32B of the third waveguide 32 is arranged in the first assembly layer 42A.

[0094] Figure 8C is an example of Figure 7 An illustration of an example of a schematic cross-sectional portion of the second EC 12C taken along line CC is shown. Figure 8C The second EC 12C shown includes a Si substrate 41 and a package 21 laminated on the Si substrate 41 . Figure 8C The schematic cross-sectional portion taken along line CC shown is a cross-sectional portion in which the third reverse tapered portion 35A is arranged in the second EC 12C. In addition, the second EC 12C includes a first assembly layer 42A and a second assembly layer 42B. The ninth tapered waveguide 32A12 in the third waveguide 32 is arranged in the first assembly layer 42A.

[0095] The waveguide length of the second adiabatic conversion portion 34 that guides only TE light is equal to the waveguide length of the first adiabatic conversion portion 24 that guides TE light and TM light. However, the waveguide width of the third inverted tapered portion 35A at the starting point is equal to the waveguide width of the first inverted tapered portion 25 at the starting point. In addition, the taper angle of the third inverted tapered portion 35A relative to the chip end face D1 is smaller than the taper angle of the first inverted tapered portion 25 relative to the chip end face D1. As a result, even when the taper length of the third inverted tapered portion 35A remains equal to the taper length of the first inverted tapered portion 25, the waveguide width of the third inverted tapered portion 35A on the chip end face D1 side is narrower than the waveguide width of the first inverted tapered portion 25 on the chip end face D1 side. As a result, the connection loss with the core C of the second optical fiber F2 is reduced, so that the loss of the TE light guided in the second EC 12C can be reduced. Therefore, it is possible to reduce the connection loss between the second EC 12C and the second optical fiber F2 due to the deviation from the tolerance in cutting, and realize an EC with high tolerance to the deviation from the tolerance in cutting.

[0096] The waveguide length of the third inverse tapered portion 35A can be shorter than Figure 2 The waveguide length of the second inverse tapered portion 35 is shown, so this can help reduce the size of the optical device.

[0097] For the optical chip 1 of Example 1, the case where the taper length of the second inverse tapered portion 35 is longer than the taper length of the first inverse tapered portion 25 has been exemplified; however, the optical chip is not limited thereto, and an embodiment thereof will be described below as Example 5.

[0098] (e) Example 5

[0099] Fig. 9 1 is a plan view schematically illustrating an example of an EC portion in an optical chip 1D of Example 5. It is noted that the same reference numerals are assigned to the same configurations as those of the optical chip 1 of Example 1, and thus descriptions of redundant configurations and operations will be omitted. The optical chip 1D of Example 5 differs from the optical chip 1 of Example 1 in that a fourth inverted tapered portion 35C is included instead of the second inverted tapered portion 35.

[0100] Although the taper length of the fourth inverse tapered portion 35C is shorter than Figure 2The taper length of the second inverted tapered portion 35 shown in the figure is smaller than that of the fourth inverted tapered portion 35C, but the waveguide width on the chip end face D1 side of the fourth inverted tapered portion 35C is narrower than the waveguide width on the chip end face D1 side of the first inverted tapered portion 25. The waveguide width on the chip end face D1 side is the width of the tip of the inverted tapered portion. As a result, the connection loss with the core C of the second optical fiber F2 is reduced, so the loss of the TE light guided in the second EC 12D can be reduced. Therefore, the connection loss between the second EC 12D and the second optical fiber F2 caused by the deviation from the tolerance in cutting can be reduced, and an EC with high tolerance to the deviation from the tolerance in cutting can be achieved.

[0101] It is to be noted that the case where the first waveguide, the second waveguide 23, the third waveguide and the fourth waveguide 33 are channel waveguides has been illustrated; however, the waveguide is not limited thereto, for example, the waveguide may be a rib waveguide, a ridge waveguide or a plate waveguide, and is variable.

[0102] Fig.10 is a diagram illustrating an example of the optical transceiver 70 of the present example. Fig.10 The optical transceiver 70 shown is connected to the optical fiber on the output side and the optical fiber on the input side. The optical transceiver 70 includes a light source 71, 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. For example, the DSP 72 performs processing such as encoding transmission data, generates an electrical signal containing the transmission data, and outputs the generated electrical signal to the optical transmitter 73A. The DSP 72 receives the electrical signal containing the received data from the optical receiver 73B, and performs processing such as decoding the acquired electrical signal, thereby obtaining the received data.

[0103] The light source 71 includes, for example, a laser diode, generates light of a given wavelength, and supplies the light to the optical transmitter 73A and the optical receiver 73B. The optical transmitter 73A modulates the light supplied from the light source 71 using an electrical signal output from the DSP 72, and outputs the resulting transmission signal to the optical fiber. The optical transmitter 73A includes an optical modulator element 73A1 that generates transmission light by modulating the light supplied from the light source 71 using an electrical signal input to the optical modulator when the light propagates through a waveguide.

[0104] 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 light supplied from the light source 71. The optical receiver 73B converts the demodulated received light into an electrical signal and outputs the converted electrical signal to the DSP 72. The optical receiver 73B includes an optical device of a plate-type optical waveguide device that guides light.

[0105] The optical device in the optical transceiver 70 includes a first EC connected to a polarization multiplexer-demultiplexer and in contact with a chip end face, and a second EC connected to an optical hybrid circuit and in contact with the chip end face. The optical device includes: a first tapered portion that guides light from an optical fiber on the input side connected to the chip end face and is included in the first EC; and a second tapered portion that guides light from an optical fiber connected to the chip end face and connected to a light source 71, and is included in a second edge coupler. The second tapered portion has a structure in which a taper angle of the second tapered portion relative to the chip end face is smaller than a taper angle of the first tapered portion relative to the chip end face. As a result, the waveguide width of the second inverted tapered portion on the chip end face side is narrower than the waveguide width of the first inverted tapered portion on the chip end face side, so the connection loss with the light source is reduced, which makes it possible to reduce the loss of the ET light guided in the second EC. Therefore, it is possible to reduce the connection loss of the second EC 12 with the light source and the optical fiber due to deviations from tolerances in cutting, and to achieve an EC with high tolerance to deviations from tolerances in cutting.

[0106] For the convenience of description, the case where the optical transceiver 70 includes the optical transmitter 73A and the optical receiver 73B has been exemplified; however, the optical transceiver 70 may include any one of the optical transmitter 73A and the optical receiver 73B. For example, an optical device may be applied to the optical transceiver 70 including the optical receiver 73B, and can be appropriately changed.

[0107] Each component of each unit shown in the drawings does not necessarily need to be physically constructed as shown in the drawings. In other words, the specific modes of distribution and integration of the units are not limited to those shown in the drawings, and all units or part of the units may be constructed by functionally or physically distributing or integrating in any unit according to various types of loads and uses.

[0108] In addition, all or a given part of various types of processing functions implemented by each device may be executed on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit) or an MCU (Micro Controller Unit)). Needless to say, all or any part of various types of processing functions may be executed on a program analyzed and executed by a CPU (or a microcomputer such as an MPU or an MCU), or on hardware according to wired logic.

[0109] According to one aspect, the coupling loss between the second edge coupler and the end face on the local oscillation light port side due to deviation from tolerance in cutting can be reduced.

Claims

1. An optical device, comprising: a first edge coupler connected to the polarization multiplexer-demultiplexer and making contact with the end face; a second edge coupler connected to the optical hybrid circuit and making contact with the end face; a first tapered portion that directs light from the end face and is included in the first edge coupler; as well as a second tapered portion that guides light from the end face and is included in the second edge coupler, The second tapered portion has a structure in which a taper angle of the second tapered portion relative to the end surface is smaller than a taper angle of the first tapered portion relative to the end surface.

2. The optical device according to claim 1, wherein: The second tapered portion has a structure in which a tapered length of the second tapered portion is longer than a tapered length of the first tapered portion.

3. The optical device according to claim 1, further comprising: a first additional portion connected to the first tapered portion on an end face side; as well as a second additional portion connected to the second tapered portion on an end face side, Here, the second tapered portion has a structure in which a waveguide width of the second tapered portion on the end surface side is narrower than a waveguide width of the first tapered portion on the end surface side.

4. The optical device according to claim 3, wherein: The first additional portion has a structure in which a waveguide length of the first additional portion is shorter than a waveguide length of the second additional portion.

5. The optical device according to claim 1, wherein: The second tapered portion comprises: a third tapered portion disposed on the end surface side; and a fourth tapered portion optically connected to the third tapered portion, and The third tapered portion has a structure in which a tapered angle of the third tapered portion relative to the end surface is smaller than a tapered angle of the fourth tapered portion relative to the end surface.

6. The optical device according to claim 1, wherein: The first edge coupler inputs light from the end face as signal light, and The second edge coupler inputs light from the end face as local oscillation light.

7. The optical device according to claim 1, wherein: The second edge coupler inputs light whose polarization state is transverse electric (TE) from the end face.

8. An optical receiver, comprising an optical receiver element that converts received signal light into an electrical signal, wherein: The light receiver element includes a first edge coupler connected to the polarization multiplexer-demultiplexer and making contact with the end face; a second edge coupler connected to the optical hybrid circuit and making contact with the end face; a first tapered portion that directs light from the end face and is included in the first edge coupler; as well as a second tapered portion that guides light from the end face and is included in the second edge coupler, The second tapered portion has a structure in which a tapered angle of the second tapered portion relative to the end surface is smaller than a tapered angle of the first tapered portion relative to the end surface.

9. An optical transceiver, comprising: a light modulator element that modulates the guided light according to an electrical signal; a light receiver element that converts received light into an electrical signal; as well as a signal processor that generates an electrical signal to the light modulator element and acquires the electrical signal from the light receiver element, Wherein, the optical receiver element comprises: a first edge coupler connected to the polarization multiplexer-demultiplexer and making contact with the end face; a second edge coupler connected to the optical hybrid circuit and making contact with the end face; a first tapered portion that guides light from the end face and is included in the first edge coupler; and a second tapered portion that guides light from the end face and is included in the second edge coupler, The second tapered portion has a structure in which a taper angle of the second tapered portion relative to the end surface is smaller than a taper angle of the first tapered portion relative to the end surface.

Images