Optical Devices

Abstract

To provide a structure with which it is possible to test with good accuracy the optical circuit formed in an optical IC chip before cutting out the optical IC chip from a wafer.SOLUTION: An optical device formed on an optical IC chip comprises: a first 1×2 optical coupler that includes an optical circuit, a first grating coupler, a second grating coupler, a first optical port provided at a single port terminal, and a second optical port and a third optical port provided at two port terminals; and a second 1×2 optical coupler that includes a fourth optical port provided at a single port terminal, and a fifth optical port and a sixth optical port provided at two port terminals. The first grating coupler is coupled to the first optical port. The second optical port is coupled to the optical circuit. The third port is coupled to the fourth optical port. The fifth optical port is coupled to the second grating coupler.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an optical device including an optical circuit formed on an optical IC chip. [Background technology]

[0002] FIG. 1 shows an example of a method for testing an optical device. In this example, the optical device includes an optical circuit 11. The optical circuit 11 includes, for example, an optical receiver. Alternatively, the optical circuit 11 includes an optical receiver and an optical transmitter. In this case, the optical transmitter includes an optical modulator. The optical circuit 11 is formed on an optical IC chip 10. An optical waveguide 12 is formed on the surface of the optical IC chip 10. The optical waveguide 12 guides input light to the optical circuit 11.

[0003] In testing an optical device, a light source 101 is used. The light source 101 is, for example, a laser light source, and outputs an optical signal (or continuous light). A polarization controller (PC) 102 controls the polarization of the optical signal output from the light source 101. The optical signal that has passed through the polarization controller 102 is input to an optical waveguide 12 via an optical fiber 103. This optical signal is guided to an optical circuit 11 via the optical waveguide 12.

[0004] When the optical circuit 11 is an optical receiver, the optical circuit 11 generates an electrical signal representing an input optical signal. Whether the optical circuit 11 is normal or not is determined based on this electrical signal. When the optical circuit 11 is an optical modulator, continuous light is input to the optical circuit 11 via the optical waveguide 12, and a drive signal (not shown) is also provided. This causes a modulated optical signal corresponding to the drive signal to be generated. Whether the optical circuit 11 is normal or not is determined based on this modulated optical signal.

[0005] 1 is performed on each optical IC chip 10 after it has been cut out from a wafer. At this time, the optical fiber 103 must be aligned with the end face of the optical waveguide 12 formed on the optical IC chip 10. This increases the time required to test the optical device.

[0006] Figure 2 shows another example of a method for testing optical devices. In the method shown in Figure 2, optical devices are tested on a wafer before each optical IC chip is cut out from the wafer. Here, testing optical devices on a wafer requires a configuration in which light is irradiated onto the surface of the wafer and the light is guided to an optical circuit 11. For this reason, a grating coupler is formed near the optical circuit 11.

[0007] 2, the optical IC chip 10 includes a device region 10a for forming an optical circuit 11, and a coupler region 10b for forming grating couplers (GCs) 21 and 22. In the coupler region 10b, the grating coupler 21 is coupled to a 1×2 optical coupler 25 via an optical waveguide 23. The 1×2 optical coupler 25 includes one optical port P1 and a pair of optical ports P2 and P3. The optical waveguide 23 is coupled to the optical port P1 of the 1×2 optical coupler 25. The optical port P2 is coupled to the optical circuit 11 via an optical waveguide 12. The optical port P3 is coupled to the grating coupler 22 via an optical waveguide 24.

[0008] When testing an optical device, test light output from light source 101 is input to grating coupler 21 via polarization controller 102 and optical fiber 103. This test light is then guided to optical circuit 11 via optical waveguide 23, 1×2 optical coupler 25, and optical waveguide 12. This test light is then used to check the operation of optical circuit 11. At this time, it is preferable to measure the power of the test light input to optical circuit 11. Therefore, the test light is branched using 1×2 optical coupler 25, and this branched light is guided to grating coupler 22 via optical waveguide 24. Furthermore, light output from grating coupler 22 is guided to optical power meter 105 via optical fiber 104. The power of the test light input to optical circuit 11 is then calculated based on the optical power measured by optical power meter 105.

[0009] A dicing line is set between the device region 10a and the coupler region 10b. When the optical IC chips 10 are cut out from the wafer, the coupler region 10b is separated from the device region 10a. Note that a configuration has been proposed in which the characteristics of optical devices are measured on the wafer before the optical IC chips are cut out from the wafer (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2020-021015 [Patent Document 2] U.S. Patent 10,145,758 Summary of the Invention [Problem to be solved by the invention]

[0011] The configuration shown in Figure 2 allows testing of each optical IC chip on a wafer. In this case, the process of arranging the end of the optical fiber near the grating coupler is easier than the process of aligning the optical fiber with the end face of the optical waveguide. Compared to the method shown in Figure 1, the method shown in Figure 2 can shorten the testing time.

[0012] 2, it is necessary to take into account the loss of the grating coupler in order to calculate the power of the test light input to the optical circuit 11. For this reason, the test light guided from the grating coupler 21 to the optical circuit 11 is branched by the 1×2 optical coupler 25 and guided to the optical power meter 105. Then, based on the value measured by the optical power meter 105, the power of the test light input to the optical circuit 11 is calculated.

[0013] In this case, it is assumed that the loss due to the 1 × 2 optical coupler 25 is known. Although the loss due to the 1 × 2 optical coupler 25 is approximately 3 dB, in reality, variations occur. For this reason, if the loss of the grating coupler is estimated using the loss value of a general 1 × 2 optical coupler, there is a risk that the power of the test light input to the optical circuit 11 cannot be measured accurately. On the other hand, if a dedicated circuit for measuring the loss of the 1 × 2 optical coupler is provided on the optical IC chip 10, it will result in poor wafer space efficiency and will require a process for measuring the loss of the 1 × 2 optical coupler.

[0014] An object of one aspect of the present invention is to provide a configuration that allows for accurate testing of an optical circuit formed on an optical IC chip before the optical IC chip is cut out from a wafer. [Means for solving the problem]

[0015] An optical device according to one embodiment of the present invention is formed on an optical IC chip. The optical device includes an optical circuit, a first grating coupler, a second grating coupler, a first 1x2 optical coupler having a first optical port at a single port end and a second and third optical ports at a two-port end, and a second 1x2 optical coupler having a fourth optical port at the single port end and a fifth and sixth optical ports at a two-port end. The first grating coupler is coupled to the first optical port. The second optical port is coupled to the optical circuit. The third optical port is coupled to the fourth optical port. The fifth optical port is coupled to the second grating coupler. [Effects of the Invention]

[0016] According to the above-described aspect, the optical circuit formed on the optical IC chip can be tested with high precision before the optical IC chip is cut out from the wafer. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating an example of a testing method for an optical device. [Figure 2] FIG. 10 is a diagram illustrating another example of a testing method for an optical device. [Figure 3] FIG. 1 is a diagram showing an example of a wafer on which a plurality of optical IC chips are formed. [Figure 4] FIG. 1 is a diagram showing an example of an optical device mounted on an optical IC chip. [Figure 5] FIG. 1 is a diagram illustrating emission and incidence by a grating coupler. [Figure 6] 1 is a diagram illustrating an example of an optical device according to an embodiment of the present invention. [Figure 7] 1A and 1B are diagrams illustrating a first variation of an optical device according to an embodiment of the present invention. [Figure 8] FIG. 1 illustrates an embodiment of an optical terminator. [Figure 9] FIG. 10 is a diagram showing a second variation of the optical device according to the embodiment of the present invention. [Figure 10] FIG. 10 is a diagram showing a third variation of the optical device according to the embodiment of the present invention. [Figure 11] FIG. 10 is a diagram showing a fourth variation of the optical device according to the embodiment of the present invention. [Figure 12] FIG. 10 is a diagram showing a fifth variation of the optical device according to the embodiment of the present invention. [Figure 13] 1 is a diagram illustrating an example of an optical transceiver module according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0018] FIG. 3 shows an example of a wafer on which a plurality of optical IC chips are formed. A plurality of optical IC chips are formed on the surface of a wafer 500. In the example shown in FIG. 3, 24 optical IC chips are formed on the wafer 500. Each optical IC chip constitutes an optical device (i.e., an optical transceiver) including, for example, an optical receiver and an optical modulator. Therefore, a plurality of optical devices can be obtained from the wafer 500 by dicing. However, testing of each optical device is performed on the wafer 500 before each optical IC chip is cut out from the wafer 500.

[0019] 4 shows an example of an optical device mounted on an optical IC chip. In this example, the optical IC chip 10 is composed of a device region 10a and a coupler region 10b. A dicing line is set between the device region 10a and the coupler region 10b.

[0020] An optical circuit 11 is formed in the device region 10a. As described above, the optical circuit 11 includes an optical receiver and / or an optical modulator. An optical waveguide 12 is coupled to the optical circuit 11. The optical waveguide 12 can guide input light to the optical circuit 11. The optical waveguide 12 is also formed beyond the dicing line into the coupler region 10b. Other circuits or elements (not shown) may also be formed in the device region 10a.

[0021] Grating couplers (GCs) 21 and 22 and 1×2 optical couplers 25 and 26 are formed in the coupler region 10b. Each of the 1×2 optical couplers 25 and 26 has one optical port P1 and a pair of optical ports P2 and P3. When light is input from the optical port P1, the light is branched and guided to the optical ports P2 and P3. When light is input from the optical port P2, the light is guided to the optical port P1. Similarly, when light is input from the optical port P3, the light is guided to the optical port P1. In this case, the loss between the optical port P1 and the optical port P2 is substantially the same on the path from the optical port P1 to the optical port P2 and on the path from the optical port P2 to the optical port P1. Furthermore, the loss between the optical port P1 and the optical port P3 is substantially the same on the path from the optical port P1 to the optical port P3 and on the path from the optical port P3 to the optical port P1.

[0022] Other circuits or elements not shown may be formed in the coupler region 10b. In Fig. 4 (and Figs. 6 to 7 and 9 to 11, etc., which will be described later), the coupler region 10b is depicted relatively large compared to the device region 10a for ease of viewing, but in practice, it is preferable that the coupler region 10b be sufficiently small compared to the device region 10a.

[0023] The grating coupler 21 is coupled to the optical port P1 of the 1×2 optical coupler 25 via an optical waveguide 23. The optical waveguide 12 is coupled to the optical port P2 of the 1×2 optical coupler 25. That is, the optical port P2 of the 1×2 optical coupler 25 is coupled to the optical circuit 11 via the optical waveguide 12. The optical port P3 of the 1×2 optical coupler 25 is coupled to the optical port P2 of the 1×2 optical coupler 26 via an optical waveguide 24. The optical port P1 of the 1×2 optical coupler 26 is coupled to the grating coupler 22 via an optical waveguide 27. Note that the optical port P3 of the 1×2 optical coupler 26 is unused in this embodiment.

[0024] The test system for testing the optical circuit 11 includes a light source 101, a polarization controller (PC) 102, and an optical power meter 105. The light source 101 outputs an optical signal (or continuous light). The polarization controller 102 controls the polarization of the optical signal output from the light source 101. For example, in TE polarization measurement, the polarization controller 102 controls the polarization of the optical signal output from the light source 101 so that a TE wave is input to the optical circuit 11. The optical signal output from the polarization controller 102 is guided to the grating coupler 21 via an optical fiber 103. The optical fiber 104 guides the light output from the grating coupler 22 to the optical power meter 105. The optical power meter 105 measures the power of the light output from the grating coupler 22.

[0025] A grating coupler is formed, for example, by providing a grating on the surface of a waveguide. As shown in FIG. 5(a), when guided light propagating through an optical waveguide passes through the grating coupler, a portion of the guided light is emitted in a predetermined direction relative to the substrate. In the following description, the direction in which a portion of the guided light is emitted by the grating coupler may be referred to as the "diffraction direction." Furthermore, as shown in FIG. 5(b), when light is incident on the grating coupler at a predetermined angle relative to the substrate, a portion of the incident light propagates through the optical waveguide.

[0026] Therefore, if the end face of the optical fiber 103 is located near the grating coupler 21, light can be incident on the optical waveguide 23 via the optical fiber 103. Also, if the end face of the optical fiber 104 is located near the grating coupler 22, light propagating through the optical waveguide 27 can be obtained. In other words, the grating couplers 21 and 22 can optically couple the optical fibers 103 and 104 to the optical waveguides 23 and 27 on the surface of the optical IC chip 10.

[0027] The grating couplers 21 and 22 are preferably formed so that their diffraction directions are the same. In this case, the optical fibers 103 and 104 may be realized by an optical fiber array.

[0028] When testing the optical circuit 11, test light output from the light source 101 is input to the grating coupler 21 via the polarization controller 102 and the optical fiber 103. This test light is then guided to the optical circuit 11 via the optical waveguide 23, the 1×2 optical coupler 25, and the optical waveguide 12. The operation of the optical circuit 11 is then confirmed using this test light.

[0029] The test light is branched by the 1×2 optical coupler 25 and output from optical port P3. In the following description, the branched light output from optical port P3 of the 1×2 optical coupler 25 may be referred to as "reference light." Here, the branching ratio of the 1×2 optical coupler 25 is, for example, 1:1. In this case, the power of the test light output from optical port P2 of the 1×2 optical coupler 25 and the power of the reference light output from optical port P3 of the 1×2 optical coupler 25 are substantially the same.

[0030] The reference light output from optical port P3 of 1×2 optical coupler 25 is guided to optical port P2 of 1×2 optical coupler 26 via optical waveguide 24. Then, this reference light is output from optical port P1 of 1×2 optical coupler 26 and guided to grating coupler 22 via optical waveguide 27. Furthermore, the reference light output from grating coupler 22 is guided to optical power meter 105 via optical fiber 104. Then, based on the power of the reference light measured by optical power meter 105, the power of the test light input to optical circuit 11 is calculated.

[0031] In the above test, when the power of the output light from the light source 101 is P_LD and the power of the reference light measured by the optical power meter 105 is P_ref, the following equation (1) is obtained. P_LD-Lin-GC21-CPL25-CPL26-GC22-Lout=P_ref (1) P_LD is assumed to be known. Lin represents the loss due to the polarization controller 102 and the optical fiber 103, which can be measured in advance. GC21 represents the loss due to the grating coupler 21. CPL25 represents the loss due to the 1×2 optical coupler 25. CPL26 represents the loss due to the 1×2 optical coupler 26. GC22 represents the loss due to the grating coupler 22. Lout represents the loss due to the optical fiber 104, which can be measured in advance.

[0032] Therefore, by measuring the power P_ref of the reference light using optical power meter 105, the coupling / branching loss L (= GC21 + CPL25 + CPL26 + GC22) can be obtained. That is, the sum of the losses due to grating coupler 21, 1×2 optical coupler 25, 1×2 optical coupler 26, and grating coupler 22 can be obtained. Here, it is assumed that the losses due to grating couplers 21 and 22 are the same. It is also assumed that the losses due to 1×2 optical couplers 25 and 26 are the same. In this case, the coupling / branching loss L represents the sum of the losses due to two grating couplers and two 1×2 optical couplers. Therefore, by dividing the coupling / branching loss L by "2," the sum of the losses due to one grating coupler and one 1×2 optical coupler can be calculated. That is, in FIG. 4, the sum of the losses due to grating coupler 21 and 1×2 optical coupler 25 is calculated.

[0033] In this way, by measuring the power P_ref of the reference light using the optical power meter 105, the sum of the loss due to the grating coupler 21 and the loss due to the 1×2 optical coupler 25 can be calculated. Therefore, by performing calibration using this value, the power of the test light input to the optical circuit 11 can be estimated with high accuracy.

[0034] However, in the configuration shown in Fig. 4, there is a risk that measurement accuracy may be reduced due to reflections in the 1x2 optical coupler. As shown in Fig. 4, the 1x2 optical coupler has one optical port (P1) and a pair of optical ports (P2, P3). Here, an input / output terminal provided with one optical port will be called a "single-port terminal (or single-port face, single-port side)," and an input / output terminal provided with a pair of optical ports will be called a "two-port terminal (or two-port face, two-port side)."

[0035] When viewed from the single-port end to the two-port end, the two optical paths are symmetric. Therefore, when light is input from the optical port provided at the single-port end (i.e., optical port P1), reflection is small. For example, when test light is input to optical port P1 of the 1x2 optical coupler 25, reflection is sufficiently small.

[0036] However, when viewed from the two-port end to the single-port end, the optical path is asymmetric. Therefore, when light is input from an optical port (e.g., optical port P2) provided at the two-port end, reflection is likely to occur. For example, when reference light is input to optical port P2 of the 1×2 optical coupler 26, a large reflection may occur. If reflection occurs in the 1×2 optical coupler 26, this reflected light is guided to the light source 101 via the 1×2 optical coupler 25, grating coupler 21, and optical fiber 103. This makes the operation of the light source 101 (e.g., laser oscillation operation) unstable, reducing measurement accuracy.

[0037] Fig. 6 shows an example of an optical device according to an embodiment of the present invention. The optical device 1 according to the embodiment of the present invention has almost the same configuration as that shown in Fig. 4. That is, an optical circuit 11 is formed in a device region 10a. Furthermore, grating couplers 21 and 22 and 1x2 optical couplers 25 and 26 are formed in a coupler region 10b.

[0038] 4, in the optical device 1, the optical port P3 of the 1×2 optical coupler 25 that outputs the reference light is coupled to the optical port P1 of the 1×2 optical coupler 26 via the optical waveguide 24. In addition, the optical port P2 of the 1×2 optical coupler 26 is coupled to the grating coupler 22 via the optical waveguide 27.

[0039] That is, when test light is input to the optical device 1, reference light is input to optical port P1 provided at the single-port end of the 1×2 optical coupler 26. Then, this reference light is output from optical ports P2 and P3 provided at the two-port end of the 1×2 optical coupler 26. Furthermore, the reference light output from optical port P2 is guided to the optical power meter 105 via the optical waveguide 27, the grating coupler 22, and the optical fiber 104.

[0040] 4 and 6, the method for calculating the power of the test light input to the optical circuit 11 is substantially the same. That is, in the optical device 1, the sum of the loss due to the grating coupler 21 and the loss due to the 1×2 optical coupler 25 is calculated using the above-mentioned formula (1). Therefore, by measuring the power P_ref of the reference light using the optical power meter 105, the power of the test light input to the optical circuit 11 can be estimated with high accuracy. Note that in the 1×2 optical coupler 26, the loss for the light input from the optical port P2 and output from the optical port P1 (FIG. 4) and the loss for the light input from the optical port P1 and output from the optical port P2 (FIG. 6) are assumed to be the same.

[0041] 6, the reference light output from the 1×2 optical coupler 25 is input to the optical port (i.e., P1) provided at the single port end of the 1×2 optical coupler 26. Therefore, the reflection of the reference light is reduced compared to the configuration shown in FIG. 4. As a result, the operation (e.g., laser oscillation operation) of the light source 101 is stabilized, and measurement accuracy is improved.

[0042] As described above, the optical circuit 11 is tested before each optical IC chip 10 is cut out from the wafer. After the test is completed, the optical IC chips 10 are cut out from the wafer. Furthermore, the coupler region 10b is cut out from the optical IC chip 10. Here, when the coupler region 10b is cut out from the optical IC chip 10, the tip of the optical waveguide 12 is positioned at the edge of the device region 10a. Therefore, when the optical device 1 is mounted in an optical module, the optical fiber is aligned and held at the tip of the optical waveguide 12.

[0043] 6, the optical device 1 is composed of a device region 10a and a coupler region 10b. However, the optical device 1 may also refer to the optical IC chip 10 after the coupler region 10b has been separated.

[0044] 7 shows a first variation of an optical device according to an embodiment of the present invention. In the optical device 1 shown in FIG. 6, the other optical port (i.e., P3) of a pair of optical ports provided at the two-port end of the 1×2 optical coupler 26 is open. In contrast, in the optical device 1B according to the first variation, as shown in FIG. 7, the optical port P3 of the 1×2 optical coupler 26 is connected to an optical terminator (T) 29 via an optical waveguide 28. Therefore, the branched light of the reference light input to the 1×2 optical coupler 26 (i.e., the light output from the optical port P3) is absorbed or emitted in the optical terminator 29. As a result, reflection of the reference light is further suppressed compared to the configuration shown in FIG. 6.

[0045] FIG. 8(a) shows an example of an optical terminator 29 mounted on the optical device 1B shown in FIG. 7. In this embodiment, the optical terminator 29 is realized by a tapered waveguide. That is, the optical terminator 29 is realized by gradually narrowing the width of the optical waveguide coupled to the optical port P3 of the 1×2 optical coupler 26 toward its tip. With this configuration, the light output from the optical port P3 of the 1×2 optical coupler 26 is emitted from the tip of the tapered waveguide. Therefore, when the reference light is input from the optical port P1 of the 1×2 optical coupler 26, reflection is suppressed.

[0046] FIG. 8(b) shows another example of the optical terminator 29 mounted on the optical device 1B shown in FIG. 7. In this embodiment, the optical terminator 29 is realized by providing a light-absorbing material in a predetermined region including the tip of the optical waveguide coupled to the optical port P3 of the 1×2 optical coupler 26. The light-absorbing material may be, for example, a metal such as aluminum or gold, a semiconductor thin film, or a silicon material doped with impurities such as boron. With this configuration, the light output from the optical port P3 of the 1×2 optical coupler 26 is absorbed at the tip of the optical waveguide 28. Therefore, when the reference light is input from the optical port P1 of the 1×2 optical coupler 26, reflection is suppressed.

[0047] 9 shows a second variation of an optical device according to an embodiment of the present invention. In the first variation shown in FIG. 7, the optical waveguide 28 coupled to the optical port P3 of the 1×2 optical coupler 26 extends toward the grating couplers 21 and 22. Therefore, if the optical terminator 29 is realized by the tapered waveguide shown in FIG. 8(a), there is a risk that the light emitted from the tip of the tapered waveguide will be recoupled in the grating couplers 21 and 22.

[0048] To alleviate this problem, in the optical device 1C according to the second variation, the optical waveguide 28 coupled to the optical port P3 of the 1×2 optical coupler 26 is formed to extend in a direction away from the grating couplers 21 and 22. In the example shown in FIG. 9, the optical waveguide 28 is bent at approximately 90 degrees. With this configuration, when the optical terminator 29 is realized using the tapered waveguide shown in FIG. 8(a), the tip of the tapered waveguide faces in a direction away from the grating couplers 21 and 22. Therefore, light emitted from the tip of the tapered waveguide is less likely to be recoupled in the grating couplers 21 and 22. Furthermore, when the optical terminator 29 is realized using the light-absorbing material shown in FIG. 8(b), even if residual light leaks from the optical waveguide, the residual light is less likely to be recoupled in the grating couplers 21 and 22. Therefore, it is possible to prevent unintended light from being guided to the light source 101 and / or the optical power meter 105, thereby improving measurement accuracy.

[0049] Fig. 10 shows a third variation of an optical device according to an embodiment of the present invention. In the first variation shown in Fig. 7 or the second variation shown in Fig. 9, an optical terminator 29 is provided in the region between the grating couplers 21, 22 and the 1x2 optical couplers 25, 26. Therefore, in the first or second variation, the region between the grating couplers 21, 22 and the 1x2 optical couplers 25, 26 becomes larger, which may increase the size of the coupler region 10b.

[0050] In the optical device 1D according to the third variation, the orientations of the 1×2 optical couplers 25 and 26 are different from each other. In the example shown in FIG. 10, the 1×2 optical coupler 25 is arranged in the direction from the grating coupler 21 toward the optical circuit 11. On the other hand, the 1×2 optical coupler 26 is arranged in a direction orthogonal to the direction from the grating coupler 21 toward the optical circuit 11. Therefore, the optical terminator 29 can be provided in a free space region different from the region between the grating couplers 21, 22 and the 1×2 optical couplers 25, 26. In this embodiment, the optical terminator 29 is provided in the vicinity of the dicing line. Therefore, according to this configuration, compared with the configuration shown in FIG. 7 or FIG. 9, the region between the grating couplers 21, 22 and the 1×2 optical couplers 25, 26 can be reduced, so that the height H of the coupler region 10b can be reduced. That is, since the size of each optical IC chip 10 can be reduced, the area efficiency of the wafer is increased.

[0051] FIG. 11 shows a fourth variation of the optical device according to an embodiment of the present invention. In the optical device 1E according to the fourth variation, the optical terminator 29 is provided between the grating couplers 21, 22. The interval between the grating couplers 21, 22 is designed based on, for example, the pitch of the optical fiber array. In this case, the interval between the grating couplers 21, 22 is, for example, about 127 μm. Also, the size of each of the grating couplers 21, 22 is about 20 μm. Therefore, in this case, the optical terminator 29 can be formed between the grating couplers 21, 22. Then, the optical terminator 29 is coupled to the optical port P3 of the 1×2 optical coupler 26 via the optical waveguide 28.

[0052] According to this configuration, even when the optical terminator 29 is realized by the tapered waveguide shown in FIG. 8(a), the light radiated from the tip of the tapered waveguide does not recombine in the grating couplers 21, 22. In addition, the size of the coupler region 10b can be reduced.

[0053] 6 to 7 and 9 to 11, two grating couplers are provided on optical IC chip 10, but the present invention is not limited to this configuration. That is, three or more grating couplers may be provided on optical IC chip 10 as needed. For example, in the case of performing a test to measure the quality of an optical signal generated by optical circuit 11, in addition to grating couplers 21 and 22, a grating coupler for emitting the optical signal generated by optical circuit 11 is provided.

[0054] When three or more grating couplers are provided on the optical IC chip 10, it is preferable that the diffraction directions of the grating couplers are the same. In addition, it is preferable that the grating couplers are arranged at equal intervals on a straight line. Here, the intervals at which the grating couplers are arranged are the same as the pitch of the optical fiber array. This improves the efficiency of testing each optical IC chip on the wafer.

[0055] Fig. 12 shows a fifth variation of an optical device according to an embodiment of the present invention. Fig. 12 illustrates a plurality of optical IC chips 10C to 10F formed on a wafer. Only a portion of each of the optical IC chips 10C and 10F is illustrated.

[0056] On each optical IC chip, an optical circuit 11, grating couplers 21 and 22, and 1×2 optical couplers 25 and 26 are formed, similar to the configurations shown in Figures 6 to 7 or 9 to 11. Also, optical waveguides 23, 24, and 27 are formed to couple these together. Furthermore, an optical terminator 29 may be provided on each optical IC chip.

[0057] However, in the fifth variation, the optical circuit 11 formed on each optical IC chip is connected to a coupling circuit formed on an adjacent optical IC chip. Here, the coupling circuit includes grating couplers 21 and 22 and 1×2 optical couplers 25 and 26. For example, the optical circuit 11 formed on optical IC chip 10D is connected to the coupling circuit formed on optical IC chip 10C, and the optical circuit 11 formed on optical IC chip 10E is connected to the coupling circuit formed on optical IC chip 10D. Each optical circuit 11 and the corresponding coupling circuit are coupled by an optical waveguide 12.

[0058] When testing optical circuit 11, a coupling circuit formed on an adjacent optical IC chip is used. For example, when testing optical circuit 11 on optical IC chip 10D, optical fibers 103 and 104 are placed near grating couplers 21 and 22 formed on optical IC chip 10C. Test light incident via grating coupler 21 is guided to optical circuit 11 via 1×2 optical coupler 25. At this time, light branched by 1×2 optical coupler 25 (i.e., reference light) is guided to power meter 105 via 1×2 optical coupler 26 and grating coupler 22.

[0059] After testing of each optical circuit 11 is completed, each optical IC chip is cut out from the wafer. As a result, a plurality of optical devices are obtained. Here, in the configurations shown in FIGS. 6 to 7 or 9 to 11, the coupler region is cut out from the optical IC chip. In contrast, in the fifth variation shown in FIG. 12, the grating couplers 21 and 22 and the 1×2 optical couplers 25 and 26 remain in each IC chip. Furthermore, when the optical IC chips are cut out from the wafer, the optical waveguides 12 coupled to the optical circuits 11 are cut off. That is, the tips of the optical waveguides 12 are positioned at the edges of the optical IC chips. Therefore, when the optical device is mounted in an optical module, an optical fiber is aligned and held at the tips of the optical waveguides 12.

[0060] 13 shows an example of an optical transceiver module according to an embodiment of the present invention. The optical transceiver module 200 includes an optical device 201, a light source 202, and a digital signal processor (DSP) 203.

[0061] The optical device 201 is realized by the optical IC chip shown in FIG. 4, FIGS. 6 to 7, or FIGS. 9 to 12. That is, the optical device 201 includes an optical circuit 11. The optical circuit 11 includes, for example, an optical modulator and an optical receiver. A light source 202 generates continuous light. This continuous light is provided to the optical modulator. When the optical receiver is a coherent receiver, the continuous light is also provided to the optical receiver. A received optical signal (Rx_In) is guided to the optical receiver. A modulated optical signal (Tx_Out) generated by the optical modulator is output to an optical fiber transmission line. A digital signal processor 203 generates a data signal for generating a modulated optical signal in the optical device 201. The digital signal processor 203 also processes an electrical signal representing the received optical signal of the optical device 201. [Explanation of symbols]

[0062] 1, 1B, 1C, 1D, 1E Optical Devices 10 Optical IC chip 10a Device Area 10b Coupler area 11 Optical circuit 12, 23, 24, 27, 28 Optical waveguide 21, 22 Grating coupler 25, 26 1x2 optical coupler 29 Optical terminator 200 Optical Transceiver Module 201 Optical Devices 500 wafers

Claims

1. An optical device formed on an optical IC chip, An optical circuit, a first grating coupler; a second grating coupler; and a first 1×2 optical coupler having a first optical port provided at a single port end and a second optical port and a third optical port provided at a two port end; a second 1×2 optical coupler having a fourth optical port provided at the single-port end and fifth and sixth optical ports provided at the two-port end; the first grating coupler is coupled to the first optical port; the second optical port is coupled to the optical circuit; the third optical port is coupled to the fourth optical port; the fifth optical port is coupled to the second grating coupler; the optical circuit is formed in a device region of the optical IC chip; the first grating coupler, the second grating coupler, the first 1×2 optical coupler, and the second 1×2 optical coupler are formed in a coupler region of the optical IC chip; A dicing line is set between the device region and the coupler region. An optical device characterized by:

2. an optical terminator coupled to the sixth optical port; 2. The optical device according to claim 1.

3. The optical terminator includes an optical waveguide coupled to the sixth optical port and a tapered waveguide that emits light propagating through the optical waveguide.

3. The optical device according to claim 2.

4. The tip of the tapered waveguide faces in a direction in which the first grating coupler and the second grating coupler are not formed.

4. The optical device according to claim 3.

5. The optical terminator includes an optical waveguide coupled to the sixth optical port and a light absorbing material that absorbs light propagating through the optical waveguide.

3. The optical device according to claim 2.

6. The second 1×2 optical coupler is arranged such that two port ends of the second 1×2 optical coupler face a direction in which the first grating coupler and the second grating coupler are not formed.

3. The optical device according to claim 2.

7. The optical terminator is disposed in a region between the first grating coupler and the second grating coupler.

3. The optical device according to claim 2.

8. A wafer on which a plurality of optical IC chips are formed, Each optical IC chip is An optical circuit, a first grating coupler; a second grating coupler; and a first 1×2 optical coupler having a first optical port provided at a single port end and a second optical port and a third optical port provided at a two port end; a second 1×2 optical coupler having a fourth optical port provided at the single-port end and fifth and sixth optical ports provided at the two-port end; In each optical IC chip, the first grating coupler is coupled to the first optical port; the third optical port is coupled to the fourth optical port; the fifth optical port is coupled to the second grating coupler; the optical circuit is formed in a device region of the optical IC chip; the first grating coupler, the second grating coupler, the first 1×2 optical coupler, and the second 1×2 optical coupler are formed in a coupler region of the optical IC chip; a dicing line is set between the device region and the coupler region; an optical circuit formed in the device region in a first optical IC chip among the plurality of optical IC chips is coupled to a second optical port of a first 1×2 optical coupler formed in the coupler region in a second optical IC chip adjacent to the first optical IC chip; A second optical port of a first 1×2 optical coupler formed in the coupler region in the first optical IC chip is coupled to an optical circuit formed in the device region in a third optical IC chip adjacent to the first optical IC chip. A wafer characterized by:

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