Integrated optical devices

Abstract

This disclosure aims to enable the connection of optical waveguide circuits using end-face connections, even with thin SiPh having through-hole vias. [Solution] The present disclosure provides an integrated optical device comprising an optical signal processing circuit for processing an optical signal and an optical waveguide circuit for guiding the optical signal, wherein the waveguide substrate provided in the optical waveguide circuit has an excess length portion that is longer than the waveguide core provided in the optical waveguide circuit, the first end face of the waveguide core located at the boundary with the excess length portion of the optical waveguide circuit is end-face connected to the waveguide core provided in the optical signal processing circuit, and at least a portion of the excess length portion of the waveguide substrate is fixed to the optical signal processing circuit.

Description

[Technical Field]

[0001] This disclosure relates to an integrated optical device for connecting silicon photonics to optical fibers. [Background technology]

[0002] A technique has been proposed to connect an optical fiber assembly (hereinafter sometimes abbreviated as FA) to silicon photonics (hereinafter sometimes abbreviated as SiPh) for optical signal input and output to SiPh (see, for example, Patent Document 1). SiPh is an optical signal processing circuit that uses silicon (Si) as the waveguide core material and silica (SiO2) as the cladding material. In Patent Document 1, a Planar Lightwave Circuit (PLC) is provided as a spot size converter (SSC) between SiPh and the optical fiber assembly, with a mode field diameter close to that of the optical fiber assembly and SiPh, respectively.

[0003] End-face connection using SSC, as described in Patent Document 1, enables low-loss optical coupling compared to surface connection using grating couplers. Therefore, it is suitable for SiPh for optical coherent communication modules where the characteristics, including optical loss, are strictly required. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 7208498 [Overview of the project] [Problems that the invention aims to solve]

[0005] To reduce costs and increase bandwidth in optical coherent communication modules, high-density packaging using flip-chip silicon-based phosphors (SiPh) is required. However, in order to create through-hole vias in the SiPh to realize the flip-chip, the Si substrate, which was originally about 600-700 μm thick, needs to be thinned to about 100 μm. As a result, the connection area for end-face connection of the SiPh to optical waveguide circuits such as PLCs is drastically reduced, and consequently, the connection strength is also significantly reduced.

[0006] This disclosure aims to enable the connection of optical waveguide circuits using end-face connections, even with thin SiPh having through-hole vias. [Means for solving the problem]

[0007] The integrated optical device of this disclosure is An optical signal processing circuit that processes optical signals, An optical guide circuit for guiding the aforementioned optical signal, Equipped with, The waveguide substrate provided in the optical waveguide circuit has an excess length portion that protrudes toward the end face side of the waveguide core provided in the optical waveguide circuit. The first end face of the waveguide core located at the boundary with the excess length portion of the optical waveguide circuit is end-face connected to the waveguide core provided in the optical signal processing circuit. At least a portion of the excess length of the waveguide substrate is fixed to the optical signal processing circuit.

[0008] The integrated optical device of this disclosure allows the excess length of the waveguide substrate to be fixed to the optical signal processing circuit in relation to the optical waveguide circuit. Therefore, even if the SiPh is thin, such as having through-hole vias, the integrated optical device of this disclosure can connect the optical waveguide circuit using end-face connections.

[0009] The integrated optical device of this disclosure may include an optical fiber assembly in which the sides of the optical fiber are held by a glass block. In this embodiment, the waveguide substrate in the optical waveguide circuit is thicker than the substrate in the optical signal processing circuit. Furthermore, the second end face of the waveguide core opposite the first end face is end-connected to the optical fiber in the optical fiber assembly. The end face side of the optical fiber in the glass block and the second end face side of the waveguide substrate are fixed together.

[0010] The optical waveguide circuit may further include a spot size converter on the first end face for matching the mode field diameter of the waveguide core in the optical waveguide circuit with the mode field diameter of the waveguide core in the optical signal processing circuit. This configuration makes it possible to connect the optical waveguide circuit, which uses a quartz substrate as the waveguide substrate, and the optical signal processing circuit with low loss.

[0011] The optical waveguide circuit may further include a spot size converter on the second end face for matching the mode field diameter of the waveguide core in the optical waveguide circuit with the mode field diameter of the optical fiber in the optical fiber assembly. This configuration makes it possible to connect the optical waveguide circuit, which uses a Si substrate as the waveguide substrate, and the optical fiber assembly with low loss.

[0012] The waveguide core of the optical signal processing circuit may have a step where the waveguide core has been removed at the connection point with the optical waveguide circuit. In this embodiment, the end face of the waveguide core exposed at the step is end-face connected to the first end face of the optical waveguide circuit.

[0013] Furthermore, the above disclosures can be combined as much as possible. [Effects of the Invention]

[0014] The integrated optical device of the present disclosure can connect an optical waveguide circuit even with a thin SiPh having through-hole vias, by using end-face connection. Thereby, the integrated optical device of the present disclosure enables high-density mounting with low loss in silicon photonics.

Brief Description of Drawings

[0015] [Figure 1] It is a configuration example of the integrated optical device of the present disclosure. [Figure 2] It is a configuration example of an optical fiber assembly, (a) shows a top view, and (b) shows a cross-sectional view. [Figure 3] It is a configuration example of an optical signal processing circuit, (a) shows a top view, and (b) shows a cross-sectional view. [Figure 4] It is a configuration example of an optical waveguide circuit, (a) shows a top view, and (b) shows a cross-sectional view. [Figure 5] It is a configuration example of an optical waveguide circuit, (a) shows a top view, and (b) shows a cross-sectional view. [Figure 6] It is a cross-sectional configuration example of the integrated optical device of the present disclosure. [Figure 7] It is a circuit configuration example of an optical signal processing circuit. [Figure 8] It is a configuration example of an optical waveguide circuit, (a) shows a top view, and (b) shows a cross-sectional view. [Figure 9] It is an example of an embodiment of the integrated optical device of the present disclosure, (a) shows a top view, and (b) shows a cross-sectional view. [Figure 10] It shows an example of the cross-sectional configuration of an optical signal processing circuit. <00001​​​​​​​​​​​​

[0016] Embodiments of this disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the embodiments shown below. These examples are illustrative, and this disclosure can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. In this specification and in the drawings, components with the same reference numerals refer to the same components.

[0017] (First Embodiment) Figure 1 shows an example of an embodiment of the integrated optical device of this disclosure. The integrated optical device of this embodiment comprises an optical signal processing circuit 91, an optical fiber assembly 92, and an optical waveguide circuit 93.

[0018] The optical signal processing circuit 91 is a circuit that processes optical signals and corresponds to SiPh. The processing of optical signals performed in the optical signal processing circuit 91 is arbitrary. The specific circuit for processing is omitted in Figure 1. The optical fiber assembly 92 comprises optical fibers 21 that are greater than or equal to the number of waveguide cores 14 provided in the optical signal processing circuit 91.

[0019] The optical waveguide circuit 93 is a Planar Lightwave Circuit (PLC) that guides optical signals. The optical signal emitted from the optical fiber 21 is incident on the waveguide core 14 of the optical signal processing circuit 91 via the waveguide core 34 of the PLC. The optical signal emitted from the waveguide core 14 of the optical signal processing circuit 91 is incident on the optical fiber 21 via the waveguide core 34 of the PLC.

[0020] Figures 2 and 3 show examples of the configuration of an optical fiber assembly 92 and an optical signal processing circuit 91. The optical fiber assembly 92 is an optical component in which one or more optical fibers 21 are held together by a glass block 22. The glass block 22 has a flat surface 25 on the end face 23 side of the optical fiber 21. The optical signal processing circuit 91 consists of a Si substrate 12, an undercladding 13, a waveguide core 14, and an overcladding 15 stacked together.

[0021] The undercladding 13 and overcladding 15 are made of SiO2, and the waveguide core 14 is made of Si. The thickness of the undercladding 13 can be any value between 1 μm and 5 μm, the thickness of the waveguide core 14 between 0.1 μm and 0.5 μm, and the thickness of the overcladding 15 between 1 μm and 3 μm. For example, the undercladding thickness can be 3 μm, the overcladding thickness 3 μm, and the waveguide core thickness 0.22 μm. The thickness T of the optical signal processing circuit 91. 91 This is any thickness on which through-hole vias can be provided in the Si substrate 12, for example, about 100 μm can be exemplified. In the following figures, the undercladding 13, waveguide core 14, and overcladding 15 may be indicated by the symbol "11".

[0022] Figure 4 shows an example of the configuration of an optical waveguide circuit 93. The optical waveguide circuit 93 comprises a waveguide substrate 32, an undercladding 33, a waveguide core 34, and an overcladding 35. The end face 42 of the waveguide core 34 functions as the first end face, and the end face 41 of the waveguide core 34 functions as the second end face. In the following figures, the undercladding 33, waveguide core 34, and overcladding 35 may be denoted by the symbol "31".

[0023] The waveguide substrate 32 has a flat surface 45 on the end face 41 side of the waveguide core 34. The waveguide substrate 32 has a thickness T that allows it to be fixed to the glass block 22. 32 and width W 32 It has a thickness T. 32 For this, approximately 1 mm can be used as an example. The thicknesses of the underclad 33, waveguide core 34, and overclad 35 can be any value that allows optical signals to propagate through the waveguide core 34. For example, the thickness of the underclad 33 can be any value between 10 μm and 20 μm, the thickness of the waveguide core 34 can be any value between 3 μm and 10 μm, and the thickness of the overclad 35 can be any value between 10 μm and 20 μm. In the following embodiment, an example of the configuration of the waveguide substrate 32 will be described in which the thicknesses of the underclad 33 and overclad 35 are approximately 20 μm.

[0024] The waveguide substrate 32 includes an excess length portion 43 that protrudes from the end face side of the waveguide core 34 provided in the optical waveguide circuit 93. The length L of the excess length portion 43 43 For example, thickness T 32 It can be made to the same or even better level.

[0025] The material of the waveguide substrate 32 is arbitrary, but for example, a Si substrate can be used. In this embodiment, since the dry etching of SiO2, which is the material of the undercladding 33, waveguide core 34, and overcladding 35, has a high selectivity ratio with Si, the waveguide substrate 32 can be used as a stop layer. This allows the excess length portion 43 to be formed using dry etching. Dry etching also has the advantage of eliminating the need to polish the optical connection end face, as a smooth end face 41 can be obtained.

[0026] In this embodiment, the excess portion 43 is formed by removing the undercladding 33, waveguide core 34, and overcladding 35, and the surface of the excess portion 43 after removal is referred to as the bottom surface of the groove. As shown in Figure 5, the excess portion 43 in this disclosure may also be formed by removing part of the waveguide substrate 32.

[0027] Figure 6 shows an example of the cross-sectional configuration of the integrated optical device of this embodiment. For ease of understanding, the figure shows the cross-sectional configuration of the waveguide core 14, waveguide core 34, and optical fiber 21, which are the optical signal propagation paths. The end face 42 of the waveguide core 34, located at the boundary with the excess length portion 43 of the optical waveguide circuit 93, is end-connected to the waveguide core 14 provided in the optical signal processing circuit 91. In addition, the end face 41 of the waveguide core 34 is end-connected to the optical fiber 21 provided in the optical fiber assembly 92.

[0028] In this embodiment, the flat surface 25 on the glass block 22 and the flat surface 45 on the waveguide substrate 32 are fixed together. The flat surface 45 has a thickness T that allows it to be fixed to the flat surface 25 of the glass block 22. 32 and width W 32 This embodiment allows for the secure fixation of the waveguide core 34 and the end face of the optical fiber 21 using adhesive 95.

[0029] Furthermore, in this embodiment, since the excess length portion 43 protrudes toward the optical signal processing circuit 91, the thickness of the underclad 33 is such that a gap is created between the bottom surface 44 of the groove and the optical waveguide circuit 93 when the waveguide core 34 and the waveguide core 14 are connected at their end faces. For this reason, in this embodiment, the integrated optical device can be connected at the end faces of the waveguide core 34 and the waveguide core 14 using adhesive 94, and at the same time, the bottom surface 44 of the groove can be fixed to the overclad 15.

[0030] The optical fiber assembly 92 is connected to the optical waveguide circuit 93, and light is input and output from the optical fiber assembly 92 through the optical waveguide circuit 93, thereby aligning the optical signal processing circuit 91 and the optical waveguide circuit 93. After alignment, adhesive 94 is applied between the surface and optical connection end face of the optical signal processing circuit 91 and the bottom surface 44 of the groove and optical connection end face 41 of the optical waveguide circuit 93, and cured to fix the connection.

[0031] Here, the bottom surface 44 of the groove in the optical waveguide circuit 93 is perpendicular to the end faces of the waveguide core 34 and the waveguide core 14. Therefore, the integrated optical device of this embodiment can firmly fix the end faces of the waveguide core 34 and the waveguide core 14. The present disclosure is not limited to this embodiment, and the objective of this disclosure can be achieved by fixing at least a portion of the excess length 43 of the waveguide substrate 32 to the optical signal processing circuit 91.

[0032] As described above, in this embodiment, when inputting and outputting optical signals from the optical fiber assembly 92 to the optical signal processing circuit 91, an optical waveguide circuit 93 is used in between, and the optical fiber assembly 92 and the optical signal processing circuit 91 are fixed to the optical waveguide circuit 93 while inputting and outputting optical signals through the optical waveguide circuit 93 by optical coupling to the optical waveguide circuit 93. A feature of this optical waveguide circuit 93 is the excess length portion 43 of the waveguide substrate 32, and the optical coupling with the optical signal processing circuit 91 uses the end face 42 of the waveguide core 34 located inside the end of the waveguide substrate 32 as the optical coupling end face.

[0033] By optically coupling the end faces of the waveguide cores of the optical signal processing circuit 91 and the optical waveguide circuit 93 facing each other, a large connection area can be achieved between the bottom surface 44 of the groove of the optical waveguide circuit 93 and the surface of the optical signal processing circuit 91, enabling a mechanically stable connection. In other words, the key point is to shift from a conventional structure where the ends of the circuits were connected and fixed together to a connection structure where the surfaces are primarily connected. In this case, for the connection with the optical fiber assembly 92, the optical waveguide circuit 93, which has a waveguide substrate 32 thicker than that of the optical signal processing circuit 91, can be used to stably fix the optical fiber assembly 92. By using such an optical waveguide circuit 93 between the optical fiber assembly 92 and the optical signal processing circuit 91, it becomes possible to optically connect the optical signal processing circuit 91 and the optical fiber assembly 92 while stably fixing them together.

[0034] During alignment, the end face of the waveguide core 14 of the optical signal processing circuit 91 and the end face of the waveguide core 34 of the optical waveguide circuit 93 face each other, and since both substrates are made of Si, it is difficult to visually confirm the positions of the waveguide cores 14 and 34. In this regard, if a quartz substrate is used for the waveguide substrate 32, it becomes easy to confirm the positions of the end faces of the waveguide cores 14 and 34 of the optical signal processing circuit 91 and the optical waveguide circuit 93 by passing through the waveguide substrate 32.

[0035] (Second embodiment) Figure 7 shows an example of the circuit configuration of the optical signal processing circuit 91 in this embodiment. The optical signal processing circuit 91 includes a branching unit 101, a receiving unit 102, and a transmitting unit 103. In this embodiment, the waveguide 14 provided in the optical signal processing circuit 91 includes three waveguides 141, 142, and 143.

[0036] The integrated optical device of this disclosure can connect an optical signal processing circuit 91 and an optical fiber assembly 92 using an end-face connection. Therefore, the integrated optical device of this disclosure is applicable to optical coherent communication modules that have stringent requirements for characteristics including optical loss. In optical coherent communication modules, transmitted light, station-emitting light, and received light are used as optical signals.

[0037] An optical signal is input to waveguide 141. A local light emission Lo for coherent reception is input to waveguide 142. The branching unit 101 branches the local light emission Lo and outputs it to the receiving unit 102 and the transmitting unit 103. The receiving unit 102 receives the optical signal input to waveguide 141 using the local light emission Lo branched by branching unit 101. The receiving unit 102 can use a 90° optical hybrid or a photodetector. The transmitting unit 103 performs phase modulation or the like on the local light emission Lo branched by branching unit 101 and transmits it to waveguide 143.

[0038] Figure 8 shows an example of the configuration of the optical waveguide circuit 93 in this embodiment. The optical waveguide circuit 93 includes three waveguide cores 34 that correspond to the input and output of the optical signal processing circuit 91 and the optical fiber assembly 92. A spot size converter 51 is provided on one end face 41 of the waveguide core 34 to match the mode field diameter of the waveguide core 34 to the mode field diameter of the optical fiber 21. A spot size converter 52 is provided on one end face 42 of the waveguide core 34 to match the mode field diameter of the waveguide core 34 to the mode field diameter of the waveguide core 14. The spot size converters 51 and 52 can be realized by presetting the width and height of the waveguide core 34 so that the mode field diameter of the waveguide core 34 becomes a desired value.

[0039] Figure 9 shows an example of the configuration of the integrated optical device of this embodiment. The end face 41 of the waveguide core 34 is polished at an angle of 8 degrees or so with respect to the plane perpendicular to the longitudinal direction of the waveguide core 34. The end face of the optical fiber 21 connected to the end face 41 is also polished at the same angle as the end face 41. This makes it possible to suppress reflected light generated at the connection surface between the waveguide core 34 and the optical fiber 21 from returning to the waveguide core 34.

[0040] In this embodiment, a bending portion 37 in which the waveguide core 34 is bent is provided in the waveguide core 34 between the spot size converters 51 and 52. The angle at which the waveguide core 34 is bent in the bending portion 37 can be any angle that can suppress the reflected return light at the end face 42 from reaching the end face 41 and suppress the reflected return light at the end face 41 from reaching the end face 42. For example, about 10 degrees can be exemplified.

[0041] (Third Embodiment) FIG. 10 shows an example of the cross-sectional configuration of the optical signal processing circuit 91 of this embodiment. In this embodiment, a step 16 in which the waveguide core 34 is removed is provided at the connection portion of the waveguide core 14 of the optical signal processing circuit 91 with the optical waveguide circuit 93. This step 16 is formed by etching from the overclad 15 side of the optical signal processing circuit 91 and is provided to a position reaching the Si substrate 12 under the underclad 13 of the optical signal processing circuit 91. By forming the step 16 by etching, a smooth optical connection end face of the waveguide core 14 can be obtained, so there is an advantage that polishing of the optical connection end face becomes unnecessary.

[0042] 4>As shown in FIG. 10, the step 16 may be provided halfway through the Si substrate 12. The height H of the step 16 16 and the depth D 16 can adopt any values that can obtain the connection strength between the waveguide cores 14 and 34. For example, if the thicknesses of the underclad 33, the waveguide core 34, and the overclad 35 are less than 15 μm, the height H of the step 16 16 can be made 15 μm or more.

[0043] FIG. 11 shows an enlarged view of the connection portion between the optical signal processing circuit 91 and the optical waveguide circuit 93 in this embodiment. The end face of the waveguide core 14 exposed at the step 16 is end-face connected to the end face 42 of the optical waveguide circuit 93. By providing the step 16 in the optical signal processing circuit 91, the bonding surface of the adhesive 94 increases, so the end faces of the waveguide core 34 and the waveguide core 14 can be fixed more firmly.

[0044] Furthermore, if the thickness of the overcladding 35 is 15 μm or more, interference between the overcladding 35 and the Si substrate 12 may be prevented by reducing the thickness of the overcladding 35 of the optical waveguide circuit 93 to about 10 μm.

[0045] (Fourth embodiment) Figure 12 shows an example of the configuration of the optical waveguide circuit 93 in this embodiment. In this embodiment, the optical waveguide circuit 93 is equipped with an "intermediate connection SiPh". Specifically, the optical waveguide circuit 93 in this embodiment is equipped with a Si substrate 62 instead of a waveguide substrate 32, and is equipped with an underclad 63, waveguide core 64, and overclad 65 instead of an underclad 33, waveguide core 34, and overclad 35. The underclad 63 and overclad 65 are formed of silica (SiO2), and the waveguide core 64 is formed of Si. In this embodiment as well, similar to the second embodiment, the optical waveguide circuit 93 is shown as an example in which three waveguides 64 corresponding to input and output with the optical signal processing circuit 91 and optical fiber assembly 92 are formed.

[0046] Thickness T of Si substrate 62 62 This can be made to approximately 700 μm, the same as conventional SiPh. In this configuration, the waveguide core 64 and the end faces of the optical fiber 21 can be firmly fixed using the adhesive 95.

[0047] Figure 13 shows an example of the cross-sectional configuration of the integrated optical device of this embodiment. In this embodiment, the mode field diameters of the waveguide core 14 and the waveguide core 64 can be made the same. Therefore, it is possible to significantly reduce the optical connection loss between the optical signal processing circuit 91 and the optical waveguide circuit 93.

[0048] To match the mode field diameters of the waveguide core 64 and the optical fiber 21, the optical waveguide circuit 93 includes a spot size converter 51. The spot size converter 51 matches the mode field diameter of SiPh to the mode field diameter of the optical fiber 21. The configuration of the spot size converter 51 can be realized, as in the second embodiment, by presetting the width and height of the waveguide core 64 so that the mode field diameter of the waveguide core 64 becomes a desired value.

[0049] The mode field diameter of the waveguide core 64 may differ from that of the waveguide core 14. In this embodiment, the optical waveguide circuit 93 includes a spot size converter 52 for matching the mode field diameter of the waveguide core 64 to that of the waveguide core 14. The configuration of the spot size converter 52 can be realized, as in the second embodiment, by presetting the width and height of the waveguide core 64 so that the mode field diameter of the waveguide core 64 becomes a desired value.

[0050] In this embodiment, the waveguide core 14, waveguide core 64, and optical fiber 21 are arranged in a straight line. The angle α between the straight line in which the waveguide core 14, waveguide core 64, and optical fiber 21 are arranged and the normal to the connecting end face of the waveguide core 64 and optical fiber 21 is 10°. Also, the angle β between the straight line in which the waveguide core 14, waveguide core 64, and optical fiber 21 are arranged and the normal to the connecting end face of the waveguide core 14 and waveguide core 64 is 10°. This suppresses the reflected light from the end face 42 of the waveguide core 64 from reaching the end face 41, and also suppresses the reflected light from the end face 41 of the waveguide core 64 from reaching the end face 42. Note that the numerical values ​​of angles α and β can be any values ​​that can suppress reflected light.

[0051] In this embodiment as well, a step 16 may be provided on the end face of the optical signal processing circuit 91, similar to the second embodiment.

[0052] (Other embodiments) In this embodiment, the optical fiber 21 is shown as a single-core fiber, but it may also be a multi-core fiber. [Explanation of Symbols]

[0053] 12, 62: Si substrate 13, 33, 63: Underclad 14, 34, 64, 141, 142, 143: Waveguide cores 15, 35, 65: Overclad 16: Step 21: Fiber optic 22: Glass Blocks 32: Waveguide substrate 37: Bending section 41, 42, 71, 72: End face 43:Extra length 44: Bottom of the groove 51, 52: Spot Size Converter 91: Optical signal processing circuit 92: Fiber Optic Assembly 93: Optical waveguide circuit 94, 95: Adhesive 101: Branching point 102: Receiver 103: Transmitter

Claims

1. An optical signal processing circuit that processes optical signals, An optical fiber assembly in which the sides of multiple optical fibers are held by a glass block, An optical waveguide circuit is positioned between the optical signal processing circuit and the optical fiber assembly to enable input and output of the optical signal from the plurality of optical fibers, Equipped with, The waveguide substrate provided in the optical waveguide circuit has an excess length portion that protrudes toward the end face side of the waveguide core provided in the optical waveguide circuit. The first end face of the waveguide core located at the boundary with the excess length portion of the optical waveguide circuit is end-face connected to the waveguide core provided in the optical signal processing circuit. The second end face of the waveguide core, which is opposite the first end face, is end-connected to the plurality of optical fibers provided in the optical fiber assembly. The flat surfaces on the end faces of the multiple optical fibers in the glass block and the flat surfaces on the second end face of the waveguide substrate are fixed together. At least a portion of the excess length of the waveguide substrate is fixed to the optical signal processing circuit. Integrated optical device.

2. The waveguide substrate in the optical waveguide circuit is thicker than the substrate in the optical signal processing circuit. The integrated optical device according to claim 1.

3. The excess length is bonded to a part of the surface of the overcladding of the optical signal processing circuit that is parallel to the waveguide core. The integrated optical device according to claim 1.

4. The optical waveguide circuit further includes, on the first end face, a spot size converter for matching the mode field diameter of the waveguide core in the optical waveguide circuit to the mode field diameter of the waveguide core in the optical signal processing circuit. The integrated optical device according to claim 1.

5. The waveguide substrate is a quartz substrate. The integrated optical device according to claim 4.

6. The optical waveguide circuit further includes, on the second end face, a spot size converter for matching the mode field diameter of the waveguide core provided in the optical waveguide circuit to the mode field diameters of the plurality of optical fibers provided in the optical fiber assembly. The integrated optical device according to claim 3.

7. The waveguide substrate is a Si substrate. The integrated optical device according to claim 6.

8. The waveguide core of the optical signal processing circuit is provided with a step where the waveguide core has been removed at the connection point with the optical waveguide circuit. The end face of the waveguide core exposed at the step is end-connected to the first end face of the optical waveguide circuit. The integrated optical device according to claim 1.

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