WO2024034131A1 - Optical waveguide circuit and method for manufacturing optical waveguide circuit - Google Patents

Optical waveguide circuit and method for manufacturing optical waveguide circuit Download PDF

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Publication number
WO2024034131A1
WO2024034131A1 PCT/JP2022/030790 JP2022030790W WO2024034131A1 WO 2024034131 A1 WO2024034131 A1 WO 2024034131A1 JP 2022030790 W JP2022030790 W JP 2022030790W WO 2024034131 A1 WO2024034131 A1 WO 2024034131A1
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optical waveguide
core
optical
layer
substrate
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PCT/JP2022/030790
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French (fr)
Japanese (ja)
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祥江 森本
摂 森脇
賢哉 鈴木
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日本電信電話株式会社
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Priority to PCT/JP2022/030790 priority Critical patent/WO2024034131A1/en
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/13—Integrated optical circuits characterised by the manufacturing method
    • G02B6/132—Integrated optical circuits characterised by the manufacturing method by deposition of thin films
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/30—Optical coupling means for use between fibre and thin-film device

Definitions

  • the present disclosure relates to an optical waveguide circuit, and more particularly, to an optical waveguide circuit in which two types of optical waveguides with significantly different mode field sizes are formed on the same substrate, and a method for manufacturing the same.
  • a silicon optical circuit which serves as an optical transmission medium in silicon photonics technology, is composed of a silicon thin wire waveguide having a core of Si and a cladding of SiO 2 .
  • the relative refractive index difference between the core and cladding is approximately 40%, and light propagation is possible within an extremely small cross-sectional area of several 100 nm square in the vicinity of 1550 nm, which is the wavelength band used for single mode communication. be. Since the allowable bending radius of the waveguide is also small, on the order of several micrometers, by using a silicon thin wire waveguide, it is possible to draw a complex wiring pattern within a narrow area. For these reasons, large-scale integration of optical circuits using silicon photonics technology is expected.
  • a silicon wire waveguide is manufactured using a well-known SOI (Silicon on insulator) substrate.
  • the SOI substrate includes a silicon support substrate, a buried silicon oxide layer (BOX layer) on the silicon support substrate, and a silicon active layer on the BOX layer.
  • the BOX layer is used as an undercladding, a silicon active layer is processed into a waveguide shape to form a core, and a quartz glass film is further formed on this core to form an overcladding layer.
  • a silicon thin wire waveguide can be formed. Since the silicon thin wire waveguide can be formed on the SOI substrate in this way, monolithic integration with electronic circuits is possible. From the viewpoint of manufacturing technology, since mature semiconductor microfabrication technology can be applied, fine patterns can be easily formed. Furthermore, by combining silicon photonics technology with semiconductor technology and electronic circuit technology, it is expected that optoelectronic integrated devices will be realized.
  • silicon thin wire waveguides have had major problems in terms of connection with other optical devices.
  • connecting optical elements in order to reduce loss at the connection point, it is important to match the mode fields of light propagating within the optical elements to be connected.
  • the coupling efficiency of propagating light at the connecting portion of the optical elements is determined by the integral of the overlap of their mode fields.
  • the mode field diameter (hereinafter referred to as MFD) of a silicon optical circuit is about 300 nm.
  • SMF single mode fiber
  • the MFD of a general SMF used for long-distance transmission is about 9 ⁇ m, and even for an SMF with a high relative refractive index difference design developed for connection with a small MFD optical waveguide, the MFD is about 4 ⁇ m.
  • the MFD of the silicon thin wire waveguide and the MFD of the SMF are 10 to several tens of times different in size. Therefore, if the two are directly connected, a significant coupling loss will occur due to the difference in MFD.
  • SSC spot size conversion
  • FIG. 3 is a diagram for explaining the configuration of a conventional SSC structure.
  • FIG. 3 shows a substrate 601, an underclad layer 602, two types of optical waveguides having different MFDs, a silicon wire waveguide 610, a planar optical waveguide 620, a silicon wire waveguide core 603, and a planar optical waveguide.
  • a structure of a silicon optical circuit 600 is shown including an SSC structure 630 having a core 604 and an overcladding layer 605 to mitigate the effects of MFD differences.
  • 3(a) is an XZ plane cross-sectional view passing through the silicon thin wire waveguide core 603 of the silicon optical circuit 600 (passing along the cross-sectional line IIIa-IIIa in FIG. 3(b)), and FIG.
  • FIG. 3(b) is an 3A is a YZ plane cross-sectional view of a side surface passing through the centers of a silicon thin wire waveguide core 603 and a planar optical waveguide core 604 (passing along the cross-sectional line IIIb-IIIb shown in FIG. 3A) of the silicon optical circuit 600.
  • FIG. 3(c) is an XY plane cross-sectional view taken along the cross-sectional line IIIc-IIIc shown in FIG. 3(b), which is the plane where the silicon thin wire waveguide 603 and the planar optical waveguide 604 of the silicon optical circuit 600 begin to overlap. . Referring to the YZ plane cross-sectional view of FIG.
  • an underclad layer 602 is formed on a silicon substrate 601, and a silicon thin wire waveguide core 603 with a small MFD is further formed on the underclad layer 602. It is formed.
  • the silicon optical circuit 600 is further entirely covered with an overcladding layer 605.
  • a silicon optical circuit 600 is manufactured by using an SOI substrate as a common substrate for a silicon substrate 601, an underclad 602, and a silicon wire waveguide core (Si core) 603.
  • the tip of the silicon thin wire waveguide core 603 is formed into a tapered reverse taper portion 603-1;
  • a planar optical waveguide core 604 is arranged so as to cover -1.
  • the relative refractive index difference between the planar optical waveguide core 604 and the undercladding layer 602 and overcladding layer 605 is smaller than the relative refractive index difference between the silicon thin wire waveguide core 603-2 and the undercladding layer 602 and overcladding layer 605.
  • the planar optical waveguide core 604 has a larger core cross-sectional area and MFD than the silicon wire waveguide core 603.
  • the light in the core 603-2 of the silicon thin wire waveguide approaches the tip of the core at the inverted tapered part 603-1 of the SSC structure 630, it can no longer be confined within the inverted tapered core, and the light in the inverted tapered part 603-1 becomes unable to be confined within the inverted tapered core. Leakage to the surrounding cladding of 1. Therefore, the light leaking from the reverse tapered portion 603-1 adiabatically transitions to the planar optical waveguide core 604 covering the silicon thin wire waveguide core 603. Since this light transition process is adiabatic, theoretically no loss of light energy occurs.
  • Planar optical waveguides with a larger MFD than the silicon thin wire waveguide shown in Figure 3 include silica-based optical waveguides with SiOx as the core and SiO2 as the cladding material, and polymer optical waveguides with the core and cladding materials as polymer materials. etc. are used.
  • the relative refractive index difference is on the order of 1 to several percent.
  • the core cross section can be expanded from the silicon thin wire waveguide core 603-2 of several hundred nanometers square to the planar optical waveguide core 604 of several micrometers square. It becomes possible to improve the coupling efficiency with SMF.
  • a silica-based optical waveguide which is a quartz-based material similar to optical fibers, is used as a planar optical waveguide, it will have low loss in the communication wavelength band, low temperature dependence and polarization dependence, and high reliability and high performance.
  • An optical device can be obtained.
  • Non-Patent Document 1 problems still remain with conventional optical circuits in which silicon thin wire waveguides and planar optical waveguides with significantly different MFDs are integrated on an SOI substrate.
  • the silicon thin wire waveguide and the planar optical waveguide are fabricated using the SOI substrate as a common substrate. Therefore, in the SSC structure of the silicon optical circuit as shown in FIG.
  • the cores of the optical waveguide are in a positional relationship in which the heights of their bottom surfaces match each other, and a planar optical waveguide core is formed in a shape that wraps around the silicon thin wire waveguide core from above.
  • the manufacturing process for such an SSC structure is to form a silicon thin wire waveguide core, and then to form a film of material that will become the planar optical waveguide core on top of the silicon thin wire waveguide core and process it. , a planar optical waveguide core is formed.
  • planar optical waveguide it is desirable to use a silica-based optical waveguide, which has low loss in the communication wavelength band, low temperature dependence and polarization dependence, and is highly reliable and high performance.
  • a quartz-based optical waveguide the formed glass film must be subjected to high-temperature treatment exceeding 1000°C in order to make the formed glass film transparent and to make the refractive index uniform. is common.
  • this high-temperature treatment is essential for the core film, whose refractive index is directly linked to the performance of the optical waveguide.
  • the material film of the planar optical waveguide core 604 of the optical circuit having the SSC structure shown in FIG. 3 is formed after the silicon thin wire waveguide core 603 is formed.
  • the silicon thin wire waveguide core 603 When subjecting to high temperature treatment, the silicon thin wire waveguide core 603 is also exposed to a high temperature environment at the same time.
  • a high temperature environment typically, when silicon is heated to 800° C. or higher in an environment where oxidizing species are present in the surroundings, such as the atmosphere, an oxidation reaction occurs and it becomes silicon oxide.
  • an oxidation reaction occurs in the silicon optical waveguide core 603, and silicon oxide is generated along the outer periphery of the silicon thin wire waveguide core 603.
  • the shape of 603 may deteriorate or be damaged.
  • the purpose of the present invention is to provide an optical waveguide circuit in which two types of optical waveguides with significantly different mode field sizes, such as silicon photonics and quartz optical waveguides, are formed on the same substrate, which is essential for the production of silica optical waveguides.
  • the goal is to prevent high-temperature processing from deteriorating the shape and performance of silicon photonics circuits.
  • the present disclosure is characterized by having the following configuration.
  • An optical waveguide circuit in which at least two types of optical waveguides are formed on a substrate, an underclad layer formed on the substrate; a second optical waveguide core formed on the undercladding layer; A core of a first optical waveguide formed of a material having a higher refractive index than the core of the second optical waveguide on the core of the second optical waveguide; An over cladding layer having a shape that wraps around the core of the second optical waveguide and the core of the first optical waveguide, and formed of a material having a lower refractive index than the core of the second optical waveguide on the under cladding layer.
  • An optical waveguide circuit comprising:
  • a method for manufacturing an optical waveguide circuit comprising: a step of depositing a material forming the core of the second optical waveguide on the substrate; a heat treatment step of heating a film made of a material forming the core of the second optical waveguide;
  • a method for manufacturing an optical waveguide circuit comprising the step of forming a layer of a material forming the core of the first optical waveguide on the second optical waveguide after the heat treatment step.
  • the high temperature treatment that is essential for manufacturing the second optical waveguide is performed on the first optical waveguide. It is possible to prevent deterioration of the wave path shape and performance.
  • FIG. 1 is a diagram showing an optical waveguide circuit according to an embodiment of the present invention.
  • FIG. 2 is a diagram showing a method for manufacturing an optical waveguide circuit according to an embodiment of the present invention.
  • FIG. 3 is a diagram illustrating a silicon optical circuit with a conventional SSC structure.
  • FIG. 1 shows an optical waveguide circuit 100 according to an embodiment of the present invention, which includes a substrate 101, an undercladding layer 102, two optical waveguides 110 and 120 having different MFDs, and an optical waveguide core of the optical waveguide 110. 104, an optical waveguide core 103 of an optical waveguide 120, an SSC region 130 for mitigating the effects of MFD differences, and an overcladding layer 105.
  • FIG. 1(a) is an XZ plane cross-sectional view passing through the optical waveguide core 104 of the optical waveguide circuit 100 (passing along the cross-sectional line Ia-Ia in FIG. 1(b)), and FIG. 1(b) is a cross-sectional view of the two optical waveguides.
  • FIG. 2 is a YZ plane cross-sectional view of a side surface passing through the center of each core 104, 103 of the wave path (passing along the cross-sectional line Ib-Ib shown in FIG. 1(a)).
  • FIG. 1(c) is an XY plane cross-sectional view of the optical waveguide circuit 100 taken along the cross-sectional line Ic-Ic shown in FIG. 1(b), and similarly, FIG.
  • FIG. 1B is an XY plane cross-sectional view taken along the cross-section line Id-Id and the cross-section line Ie-Ie in FIG. 1(b).
  • the optical waveguide circuit 100 in FIG. 1 has a structure in which two different types of optical waveguides, a first optical waveguide 110 and a second optical waveguide 120, formed on a common substrate 101 are optically connected. There is.
  • an underclad layer 102 is formed on the substrate 101, and a second optical waveguide core 103 is formed on the underclad layer 102.
  • a first optical waveguide core 104 is formed on the second optical waveguide core 103.
  • an overcladding layer 105 is formed on the undercladding layer 102 in a shape that wraps around the second optical waveguide core 103 and the first optical waveguide core 104 .
  • each figure in FIG. 1 shows only a part of the optical circuit according to the first embodiment in which two optical waveguides 110 and 120 are integrally integrated on a substrate 101.
  • the number of optical waveguides is not limited to this, and other optical waveguides may be included in the circuit.
  • FIG. 1 shows a shape in which the top surface of the second optical waveguide core 103 and the bottom surface of the first optical waveguide core 104 are in contact with each other, in this embodiment, the second optical waveguide core 103 The two cores do not need to be in contact with each other as long as the positional relationship that the first optical waveguide core 104 is arranged above is satisfied.
  • the materials constituting the first optical waveguide 110 and the second optical waveguide 120 have a refractive index such that the core of the first optical waveguide>core of the second optical waveguide>the cladding of the second optical waveguide.
  • the material is not limited as long as it satisfies the relationship.
  • the material of the core of the first optical waveguide is single crystal silicon (Si)
  • the material of the core of the second optical waveguide is SiO 2 having a relatively high refractive index.
  • the material of the cladding of the second optical waveguide is a silica-based glass having SiO 2 as a base material, such as SiO 2 having a relatively low refractive index, but the material used is not limited to this.
  • Si, SiN, SiON, etc. can be used as the core material of the first optical waveguide, and SiO 2 , SiOx, polymer, etc. can be used as the material of the second optical waveguide.
  • Both the first optical waveguide 110 and the second optical waveguide 120 have no upper limit on the core cross-sectional size, and are multimode optical waveguides that propagate light in multiple modes for the wavelength of the optical signal used. You can also do that. Furthermore, by reducing the core cross-sectional size, it is possible to create a single-mode optical waveguide that propagates only the lowest-order mode.
  • the core 104 of the first optical waveguide 110 is formed as a Si core
  • the core 103 of the second optical waveguide 120 is formed as a SiO 2 core
  • the overcladding layer 105 is formed as a SiO 2 cladding. can do.
  • the first optical waveguide is formed as a silicon wire waveguide
  • the second optical waveguide is formed as a planar optical waveguide.
  • the difference in refractive index between the core and cladding of the first optical waveguide 110 is large, and therefore the core cross-sectional size can be reduced to several hundreds of nanometers square.
  • the difference in refractive index between the core and cladding is smaller than that in the first optical waveguide. Therefore, the core cross-sectional size of the second optical waveguide ranges from several ⁇ m to about 10 ⁇ m square.
  • the core cross-sectional size of the first optical waveguide is about several hundred nm square, and the second optical waveguide is several ⁇ m square. ⁇ 10 ⁇ m square. Therefore, the magnitudes of the mode fields propagating within the cores of the two waveguides (mode field diameter: MFD) are significantly different from each other, and the MFD of the second optical waveguide 120 is larger than that of the first optical waveguide 110. value.
  • MFD mode field diameter
  • the size of the mode field (mode field diameter: MFD) propagating within the core (Si core) 104 of the first optical waveguide is gradually expanded.
  • MFD mode field diameter
  • SSC spot size conversion
  • the structure for realizing the SSC function does not matter; for example, it can be realized by a structure in which the first optical waveguide core (Si core) 104 has a tapered shape.
  • the first optical waveguide core (Si core) 104 may have a tapered shape in the vertical direction of the substrate such that the height gradually decreases, or the first optical waveguide core (Si core) 104 may have a tapered shape in the vertical direction of the substrate. It can also be realized by a segment-like structure divided in the propagation direction. Furthermore, both the tapered shape and the segmented shape may be combined.
  • connection loss There are two main types of methods for connecting cores in single mode.
  • One connection method is adiabatic coupling, in which two cores are arranged so as to be in contact with each other in the propagation direction, and one core is made into a tapered shape so that the equivalent refractive index of the mode propagating within the core is By gradually decreasing the amount, the optical energy of the mode that can no longer be confined is adiabatically transferred to the other adjacent core.
  • connection method is butt coupling, in which cores are arranged with their end surfaces butted against each other, and the coupling efficiency is defined by the overlapping integral of the mode profiles existing in each of the two cores.
  • the optical energy propagating within the first optical waveguide core (Si core) 104 is transferred to an adjacent second optical waveguide core. can be adiabatically transitioned to the optical waveguide core (SiO 2 core) 103.
  • the tip of the first optical waveguide core (Si core) 104 having a tapered structure it is possible to maximize the optical energy that undergoes adiabatic transition.
  • the width of the taper tip by processing the width of the taper tip to be as thin as 0.1 ⁇ m or less, more than 90% of the optical energy of the polarized wave component in the horizontal direction of the substrate propagating through the first optical waveguide core (Si core) 104 can be Adiabatic transition can be made to the second optical waveguide core (SiO 2 core) 103.
  • FIG. 2(a) of FIG. 2 is an end view showing the structure seen from the XY plane side
  • FIG. 2(b) is an end view showing the structure seen from the YZ plane side passing through the cross-sectional line IIb-IIb shown in FIG. 2(a).
  • FIGS. 2(c), 2(e), and 2(g) are end views showing the structure viewed from the XY plane
  • FIG. 2(d) is shown in FIG. 2(c).
  • the substrate forming the optical waveguide circuit 100 shown in FIGS. 2(a) and 2(b) is produced by the following steps.
  • a SiO 2 layer 102 is formed on a substrate 101 with a smooth surface (specific examples include a glass substrate, but a Si substrate is particularly preferred) on which a SiO 2 layer can be formed.
  • any method may be used as long as it can form a uniform and smooth layer to the extent that another layer can be formed directly above the formed layer, but for example, a film forming method such as a flame deposition method may be used. Can be used.
  • a SiO 2 layer 203 Directly above the SiO 2 layer 102, a SiO 2 layer 203 having a higher refractive index than the SiO 2 layer 102 is formed.
  • the refractive index may be controlled by adding GeO 2 , ZrO 2 , HfO 2 , P 2 O 5 , B 2 O 3 or the like.
  • a film forming method such as a flame deposition method can be used, for example. After forming the SiO 2 layer 203, the film is subjected to heat treatment at a temperature exceeding 1000° C. for the purpose of making the film transparent and making the refractive index uniform.
  • a Si layer 204 is formed directly on the SiO 2 layer 203 and is flattened, as shown in FIG. 2(a). Then, the multilayer substrate shown in FIG. 2(b) is created.
  • the Si layer 204 may be formed by sputtering amorphous silicon, or after bonding another Si substrate to the upper surface of the substrate 101 (on the SiO 2 layer 203), the Si layer 204 may be formed to a desired Si film thickness. You may obtain.
  • SiO 2(a) and 2(b) are made of a single SiO 2 layer formed under the surface Si layer of a general SOI (Silicon on Insulator) substrate, that is, a BOX (Buried Oxide). It can be said that two SiO 2 layers having different refractive indexes, that is, the SiO 2 layer 102 and the SiO 2 layer 203, are formed instead of the two SiO 2 layers. Note that a material layer having a lower refractive index than the SiO 2 layer 203 and the Si layer 204 may be formed between the SiO 2 layer 203 and the Si layer 204.
  • SOI Silicon on Insulator
  • BOX Buried Oxide
  • the Si layer 204 of the multilayer substrate of FIGS. 2(a) and 2(b) is used as the first optical waveguide core (104) to provide light.
  • the Si core 104 is formed by processing the Si core 104 so that it can propagate.
  • an optical circuit for Si photonics may be formed in conjunction with the formation of the Si core 104.
  • the SiO 2 layer 203 is further processed to allow light to propagate as the core 103 of the second optical waveguide .
  • a core 103 is formed.
  • it is desirable that the width of the SiO 2 core 103 is wider than the width of the Si core 104 that has already been processed. Thereby, it is possible to eliminate the influence of the processing of the SiO 2 core 103 on the side wall of the Si core 104 that has already been processed.
  • a SiO 2 layer 105 having a lower refractive index than the SiO 2 core 103 is formed to fabricate an optical waveguide circuit.
  • the first optical waveguide and the second optical waveguide are each composed of a SiO 2 core 103, a Si core 104, a SiO 2 cladding layer 105, etc.
  • the materials constituting the first optical waveguide 110 and the second optical waveguide 120 have a refractive index such that the core of the first optical waveguide > the core of the second optical waveguide > the core of the second optical waveguide.
  • the material to be used is not limited as long as it satisfies the relationship: cladding.
  • the high-temperature treatment of the SiO 2 layer 203 which is an essential step for making the core (SiO 2 core) 103 of the second optical waveguide transparent and uniformizing the refractive index, is performed on the SiO 2 layer 203. 204 or processing of the Si layer 204 to form the first optical waveguide core (Si core 104). Therefore, the Si core 104 is not exposed to the high-temperature treatment that is essential for forming the SiO 2 core 103, and an optical waveguide circuit that maintains the shape and characteristics when the Si core 104 was processed can be manufactured.
  • the high temperature treatment that is essential for manufacturing the second optical waveguide is performed on the first optical waveguide. It is possible to prevent deterioration of the shape and performance of the optical waveguide.
  • silica-based optical waveguides can be used in an optical waveguide circuit in which two types of optical waveguides with significantly different mode field sizes, such as silicon photonics and quartz-based optical waveguides, are formed on the same substrate.
  • silicon photonics circuit in the upper layer of the waveguide, it is possible to prevent the high-temperature treatment that is essential for manufacturing silica-based optical waveguides from deteriorating the shape and performance of the silicon photonics circuit.

Abstract

This optical waveguide circuit (100) has two or more types of optical waveguides (110, 120) formed on a substrate (101), and comprises: an undercladding layer (102) formed on the substrate (101); a core (103) of the second optical waveguide (120), said core being formed on the undercladding layer (102); a core (104) of the first optical waveguide (110), said core being formed on the core (103) of the second optical waveguide (120) and being formed of a material having a higher refractive index than the core (103) of the second optical waveguide (120); and an over-cladding layer (105) that is formed on the undercladding layer (102) in a shape enclosing the core (103) of the second optical waveguide (120) and the core (104) of the first optical waveguide (110), and is formed of a material having a lower refractive index than the core (103) of the second optical waveguide (120).

Description

光導波回路および光導波回路の製造方法Optical waveguide circuit and method for manufacturing optical waveguide circuit
　本開示は、光導波回路に関し、より詳細には、モードフィールドの大きさが大きく異なる２種類の光導波路を同一基板上に形成する光導波回路およびその製造方法に関する。 The present disclosure relates to an optical waveguide circuit, and more particularly, to an optical waveguide circuit in which two types of optical waveguides with significantly different mode field sizes are formed on the same substrate, and a method for manufacturing the same.
　近年のデータセンタ内通信のトラフィック増大に伴い、コンピュータ筐体内素子の光配線化技術の重要性が高まっている。なかでも、多数の光回路を高密度に集積可能なシリコンフォトニクス技術が注目を集めている。 With the recent increase in communication traffic within data centers, the importance of optical wiring technology for elements inside computer cases is increasing. Among these, silicon photonics technology, which enables the high-density integration of large numbers of optical circuits, is attracting attention.
　シリコンフォトニクス技術において光伝送媒体となるシリコン光回路は、ＳｉをコアとしＳｉＯ２をクラッドとするシリコン細線導波路によって構成される。シリコン細線導波路では、コアとクラッドとの比屈折率差が４０％程度であり、シングルモード通信の使用波長帯である１５５０ｎｍ付近において、数１００ｎｍ角という極小断面領域内での光伝搬が可能である。導波路の許容曲げ半径も数μｍ程度と小さいため、シリコン細線導波路を用いることにより、狭い領域内に複雑な配線パターンの描画が可能である。これらのことから、シリコンフォトニクス技術による光回路の大規模集積化が期待されている。 A silicon optical circuit, which serves as an optical transmission medium in silicon photonics technology, is composed of a silicon thin wire waveguide having a core of Si and a cladding of SiO 2 . In silicon thin wire waveguides, the relative refractive index difference between the core and cladding is approximately 40%, and light propagation is possible within an extremely small cross-sectional area of several 100 nm square in the vicinity of 1550 nm, which is the wavelength band used for single mode communication. be. Since the allowable bending radius of the waveguide is also small, on the order of several micrometers, by using a silicon thin wire waveguide, it is possible to draw a complex wiring pattern within a narrow area. For these reasons, large-scale integration of optical circuits using silicon photonics technology is expected.
　シリコン細線導波路は、よく知られたＳＯＩ（Ｓｉｌｉｃｏｎ　ｏｎ　ｉｎｓｕｌａｔｏｒ）基板を用いて作製される。ＳＯＩ基板は、シリコン支持基板、シリコン支持基板上の埋込シリコン酸化層（ＢＯＸ層）、および、ＢＯＸ層上のシリコン活性層を備える。このようなＳＯＩ基板上で、ＢＯＸ層をアンダークラッドとし、シリコン活性層を導波路形状に加工したコアを形成し、さらにこのコアの上に石英ガラス膜を形成してオーバークラッド層とすることで、シリコン細線導波路を形成することができる。このようにシリコン細線導波路は、ＳＯＩ基板上に形成できることから、電子回路とのモノリシック集積が可能である。製造技術の観点では、成熟した半導体微細加工技術を適用できるため、微細パターンを容易に形成可能である。また、シリコンフォトニクス技術を半導体技術や電子回路技術と組み合わせることで、光電子集積型デバイスの実現も期待される。 A silicon wire waveguide is manufactured using a well-known SOI (Silicon on insulator) substrate. The SOI substrate includes a silicon support substrate, a buried silicon oxide layer (BOX layer) on the silicon support substrate, and a silicon active layer on the BOX layer. On such an SOI substrate, the BOX layer is used as an undercladding, a silicon active layer is processed into a waveguide shape to form a core, and a quartz glass film is further formed on this core to form an overcladding layer. , a silicon thin wire waveguide can be formed. Since the silicon thin wire waveguide can be formed on the SOI substrate in this way, monolithic integration with electronic circuits is possible. From the viewpoint of manufacturing technology, since mature semiconductor microfabrication technology can be applied, fine patterns can be easily formed. Furthermore, by combining silicon photonics technology with semiconductor technology and electronic circuit technology, it is expected that optoelectronic integrated devices will be realized.
　一方でシリコン細線導波路は、他の光素子との接続という観点で大きな問題を抱えていた。光素子同士を接続する際、接続点における損失を低減するためには、接続する光素子内を伝搬する光のモードフィールドを合わせることが重要である。二つの光素子を突き合わせて接続させた場合、光素子の接続部分での伝搬光の結合効率は両者のモードフィールドの重なり積分によって決定づけられる。一般に、シリコン光回路のモードフィールド径（以下、ＭＦＤと称する）は３００ｎｍ程度である。 On the other hand, silicon thin wire waveguides have had major problems in terms of connection with other optical devices. When connecting optical elements, in order to reduce loss at the connection point, it is important to match the mode fields of light propagating within the optical elements to be connected. When two optical elements are butted and connected, the coupling efficiency of propagating light at the connecting portion of the optical elements is determined by the integral of the overlap of their mode fields. Generally, the mode field diameter (hereinafter referred to as MFD) of a silicon optical circuit is about 300 nm.
　コンピュータ筐体内にて、回路外部の光伝送媒体として使用されているようなシングルモードファイバ（Ｓｉｎｇｌｅ　Ｍｏｄｅ　Ｆｉｂｅｒ：以下、ＳＭＦと称する）との接続を考える。長距離伝送にも用いられる一般的なＳＭＦのＭＦＤは９μｍ程度であり、ＭＦＤの小さな光導波路などとの接続用に開発された高比屈折率差設計のＳＭＦでもＭＦＤは４μｍ程度である。このように、シリコン細線導波路のＭＦＤとＳＭＦのＭＦＤとは、その大きさは１０～数十倍も異なっている。このため、両者を直接接続した場合には、ＭＦＤの相違によって甚大な結合損失が生じてしまう。このようなシリコン光回路とＳＭＦの間の接続性に関する問題を解決するために、スポットサイズ変換（Ｓｐｏｔ　Ｓｉｚｅ　Ｃｏｎｖｅｒｓｉｏｎ：以下、ＳＳＣと称する）構造を挿入する手法が提案されていた。 Consider connection to a single mode fiber (hereinafter referred to as SMF) that is used as an optical transmission medium outside the circuit inside a computer case. The MFD of a general SMF used for long-distance transmission is about 9 μm, and even for an SMF with a high relative refractive index difference design developed for connection with a small MFD optical waveguide, the MFD is about 4 μm. As described above, the MFD of the silicon thin wire waveguide and the MFD of the SMF are 10 to several tens of times different in size. Therefore, if the two are directly connected, a significant coupling loss will occur due to the difference in MFD. In order to solve such problems regarding the connectivity between the silicon optical circuit and the SMF, a method of inserting a spot size conversion (hereinafter referred to as SSC) structure has been proposed.
　図３は、従来技術のＳＳＣ構造の構成を説明するための図である。図３には、基板６０１と、アンダークラッド層６０２と、異なるＭＦＤを持つ２種類の光導波路である、シリコン細線導波路６１０と、平面光導波路６２０と、シリコン細線導波路コア６０３、平面光導波路コア６０４と、オーバークラッド層６０５とを有する、ＭＦＤの差異の影響を緩和するためのＳＳＣ構造部６３０を含むシリコン光回路６００の構造が示されている。図３（ａ）は、シリコン光回路６００のシリコン細線導波路コア６０３を通る（図３（ｂ）の断面線ＩＩＩa－ＩＩＩaを通る）のＸＺ平面断面図であり、図３（ｂ）は、シリコン光回路６００のシリコン細線導波路コア６０３および平面光導波路コア６０４の中心を通る側面（図３（ａ）に示す断面線ＩＩＩｂ－ＩＩＩｂを通る）のＹＺ平面断面図である。また、図３（ｃ）は、シリコン光回路６００のシリコン細線導波路６０３と平面光導波路６０４が重なり始める面である図３（ｂ）に示す断面線ＩＩＩｃ－ＩＩＩｃを通るＸＹ平面断面図である。図３（ｂ）のＹＺ平面断面図を参照すると、シリコン基板６０１の上に、アンダークラッド層６０２が形成されており、さらにアンダークラッド層６０２の上に、ＭＦＤの小さいシリコン細線導波路コア６０３が形成されている。シリコン光回路６００は、さらに全体がオーバークラッド層６０５により覆われている。シリコン光回路６００は、シリコン基板６０１、アンダークラッド６０２、シリコン細線導波路コア（Ｓｉコア）６０３が、ＳＯＩ基板を共通の基板として利用し作製される。 FIG. 3 is a diagram for explaining the configuration of a conventional SSC structure. FIG. 3 shows a substrate 601, an underclad layer 602, two types of optical waveguides having different MFDs, a silicon wire waveguide 610, a planar optical waveguide 620, a silicon wire waveguide core 603, and a planar optical waveguide. A structure of a silicon optical circuit 600 is shown including an SSC structure 630 having a core 604 and an overcladding layer 605 to mitigate the effects of MFD differences. 3(a) is an XZ plane cross-sectional view passing through the silicon thin wire waveguide core 603 of the silicon optical circuit 600 (passing along the cross-sectional line IIIa-IIIa in FIG. 3(b)), and FIG. 3(b) is an 3A is a YZ plane cross-sectional view of a side surface passing through the centers of a silicon thin wire waveguide core 603 and a planar optical waveguide core 604 (passing along the cross-sectional line IIIb-IIIb shown in FIG. 3A) of the silicon optical circuit 600. FIG. Further, FIG. 3(c) is an XY plane cross-sectional view taken along the cross-sectional line IIIc-IIIc shown in FIG. 3(b), which is the plane where the silicon thin wire waveguide 603 and the planar optical waveguide 604 of the silicon optical circuit 600 begin to overlap. . Referring to the YZ plane cross-sectional view of FIG. 3(b), an underclad layer 602 is formed on a silicon substrate 601, and a silicon thin wire waveguide core 603 with a small MFD is further formed on the underclad layer 602. It is formed. The silicon optical circuit 600 is further entirely covered with an overcladding layer 605. A silicon optical circuit 600 is manufactured by using an SOI substrate as a common substrate for a silicon substrate 601, an underclad 602, and a silicon wire waveguide core (Si core) 603.
　図３（ａ）ないし図３（ｃ）に示すように、シリコン光回路６００のＳＳＣ構造部６３０では、シリコン細線導波路コア６０３の先端を先細りの逆テーパ部６０３－１とし、逆テーパ部６０３－１を覆うように平面光導波路コア６０４が配置されている。平面光導波路コア６０４とアンダークラッド層６０２およびオーバークラッド層６０５との比屈折率差は、シリコン細線導波路コア６０３－２とアンダークラッド層６０２およびオーバークラッド層６０５との比屈折率差よりも小さい。また平面光導波路コア６０４は、シリコン細線導波路コア６０３よりもコア断面積およびＭＦＤが大きい。 As shown in FIGS. 3(a) to 3(c), in the SSC structure portion 630 of the silicon optical circuit 600, the tip of the silicon thin wire waveguide core 603 is formed into a tapered reverse taper portion 603-1; A planar optical waveguide core 604 is arranged so as to cover -1. The relative refractive index difference between the planar optical waveguide core 604 and the undercladding layer 602 and overcladding layer 605 is smaller than the relative refractive index difference between the silicon thin wire waveguide core 603-2 and the undercladding layer 602 and overcladding layer 605. . Further, the planar optical waveguide core 604 has a larger core cross-sectional area and MFD than the silicon wire waveguide core 603.
　シリコン細線導波路のコア６０３－２内の光は、ＳＳＣ構造部６３０の逆テーパ部６０３－１でコア先端に近づくにしたがい、逆テーパ形状のコア内には閉じ込めきれなくなり、逆テーパ部６０３－１の周囲のクラッドへ漏洩する。したがって、逆テーパ部６０３－１から漏洩した光は、シリコン細線導波路コア６０３を覆う平面光導波路コア６０４へと断熱的に遷移する。この光の遷移過程は断熱的であるので、理論上は光エネルギーの損失を発生しない。 As the light in the core 603-2 of the silicon thin wire waveguide approaches the tip of the core at the inverted tapered part 603-1 of the SSC structure 630, it can no longer be confined within the inverted tapered core, and the light in the inverted tapered part 603-1 becomes unable to be confined within the inverted tapered core. Leakage to the surrounding cladding of 1. Therefore, the light leaking from the reverse tapered portion 603-1 adiabatically transitions to the planar optical waveguide core 604 covering the silicon thin wire waveguide core 603. Since this light transition process is adiabatic, theoretically no loss of light energy occurs.
　図３に示すようなシリコン細線導波路よりもＭＦＤの大きい平面光導波路としては、ＳｉＯｘをコア、ＳｉＯ２をクラッド材料とする石英系光導波路や、ポリマー材料をコア、クラッド材料とするポリマー光導波路などが用いられる。これら平面光導波路の材料の組み合わせのいずれも、比屈折率差は１～数％程度である。 Planar optical waveguides with a larger MFD than the silicon thin wire waveguide shown in Figure 3 include silica-based optical waveguides with SiOx as the core and SiO2 as the cladding material, and polymer optical waveguides with the core and cladding materials as polymer materials. etc. are used. For any of these combinations of materials for the planar optical waveguide, the relative refractive index difference is on the order of 1 to several percent.
　図３のシリコン光回路６００のＳＳＣ構造部６３０によって、数１００ｎｍ角程度のシリコン細線導波路コア６０３－２から、数μｍ角程度の平面光導波路コア６０４にコア断面を拡大することができるので、ＳＭＦとの結合効率を改善することが可能となる。特に平面光導波路として、光ファイバと同様の石英系材料である石英系光導波路を採用すれば、通信波長帯で低損失であり、温度依存性や偏波依存性が低く、高信頼・高性能な光デバイスが得られる。 With the SSC structure 630 of the silicon optical circuit 600 in FIG. 3, the core cross section can be expanded from the silicon thin wire waveguide core 603-2 of several hundred nanometers square to the planar optical waveguide core 604 of several micrometers square. It becomes possible to improve the coupling efficiency with SMF. In particular, if a silica-based optical waveguide, which is a quartz-based material similar to optical fibers, is used as a planar optical waveguide, it will have low loss in the communication wavelength band, low temperature dependence and polarization dependence, and high reliability and high performance. An optical device can be obtained.
　以上説明したように、シリコン光回路に対して石英系光導波路を代表とする平面光導波路を組み合わせることで、ＭＦＤの異なる２種類の光導波路を低損失に接続し、シリコンフォトニクス技術の接続性を向上するものが知られていた（非特許文献１）。しかしながら、ＳＯＩ基板上に、ＭＦＤの大きく異なるシリコン細線導波路および平面光導波路を集積した従来技術の光回路では、依然として問題が残っている。 As explained above, by combining a planar optical waveguide, typically a silica-based optical waveguide, with a silicon optical circuit, two types of optical waveguides with different MFDs can be connected with low loss, and the connectivity of silicon photonics technology can be improved. It has been known that the improvement can be achieved (Non-Patent Document 1). However, problems still remain with conventional optical circuits in which silicon thin wire waveguides and planar optical waveguides with significantly different MFDs are integrated on an SOI substrate.
　上述したように、シリコン細線導波路および平面光導波路は、ＳＯＩ基板を共通の基板として作製されるため、図３に示すようなシリコン光回路のＳＳＣ構造部では、シリコン細線導波路のコアおよび平面光導波路のコアは、互いにその底面の高さが一致した位置関係にあり、シリコン細線導波路コアを上から包み込む形状で平面光導波路コアが形成されている。そして、このようなＳＳＣ構造部の製造工程としては、シリコン細線導波路コアを形成したのちに、シリコン細線導波路コアの上に平面光導波路コアとなる材料膜を成膜し、加工することで、平面光導波路コアが形成される。 As mentioned above, the silicon thin wire waveguide and the planar optical waveguide are fabricated using the SOI substrate as a common substrate. Therefore, in the SSC structure of the silicon optical circuit as shown in FIG. The cores of the optical waveguide are in a positional relationship in which the heights of their bottom surfaces match each other, and a planar optical waveguide core is formed in a shape that wraps around the silicon thin wire waveguide core from above. The manufacturing process for such an SSC structure is to form a silicon thin wire waveguide core, and then to form a film of material that will become the planar optical waveguide core on top of the silicon thin wire waveguide core and process it. , a planar optical waveguide core is formed.
　平面光導波路としては、通信波長帯で低損失であり、温度依存性や偏波依存性が低く、高信頼・高性能な石英系光導波路を採用することが望ましい。このような石英系光導波路を採用した場合には、成膜をしたガラス膜の透明化および屈折率の均一化のために、成膜したガラス膜に対して１０００℃を超える高温処理を施すことが一般的である。特に、屈折率の制御が光導波路の性能に直結するコア膜は、この高温処理が必須である。図３のＳＳＣ構造部を備える光回路の平面光導波路コア６０４の材料膜が成膜されるのは、シリコン細線導波路コア６０３が形成された後であるので、平面光導波路コア６０４の材料膜に高温処理を施す際に、シリコン細線導波路コア６０３も同時に高温環境下にさらされることになる。通常、シリコンは、大気などの周囲に酸化種が存在する環境下で８００℃以上に加熱された際に、酸化反応が生じシリコン酸化物となる。つまり、平面光導波路の製造上必須である高温処理によって、シリコン光導波路コア６０３に酸化反応が生じ、シリコン細線導波路コア６０３の外周部に沿ってシリコン酸化物が生成され、シリコン細線導波路コア６０３の形状劣化や損傷が生じてしまうことがあった。 As the planar optical waveguide, it is desirable to use a silica-based optical waveguide, which has low loss in the communication wavelength band, low temperature dependence and polarization dependence, and is highly reliable and high performance. When such a quartz-based optical waveguide is adopted, the formed glass film must be subjected to high-temperature treatment exceeding 1000°C in order to make the formed glass film transparent and to make the refractive index uniform. is common. In particular, this high-temperature treatment is essential for the core film, whose refractive index is directly linked to the performance of the optical waveguide. The material film of the planar optical waveguide core 604 of the optical circuit having the SSC structure shown in FIG. 3 is formed after the silicon thin wire waveguide core 603 is formed. When subjecting to high temperature treatment, the silicon thin wire waveguide core 603 is also exposed to a high temperature environment at the same time. Typically, when silicon is heated to 800° C. or higher in an environment where oxidizing species are present in the surroundings, such as the atmosphere, an oxidation reaction occurs and it becomes silicon oxide. In other words, due to the high-temperature treatment that is essential for manufacturing a planar optical waveguide, an oxidation reaction occurs in the silicon optical waveguide core 603, and silicon oxide is generated along the outer periphery of the silicon thin wire waveguide core 603. In some cases, the shape of 603 may deteriorate or be damaged.
　このように、シリコンフォトニクスと石英系光導波路のような、２種類の異なる材料の光導波路を同一基板上に集積した際、石英系光導波路の製造上必須である高温処理が、シリコン細線導波路の形状や性能に対して影響を与えることを防ぐことが困難であった。 In this way, when optical waveguides made of two different materials, such as silicon photonics and silica-based optical waveguides, are integrated on the same substrate, the high-temperature treatment that is essential for manufacturing silica-based optical waveguides is It was difficult to prevent this from affecting the shape and performance of the product.
　本発明の目的は、シリコンフォトニクスと石英系光導波路のような、モードフィールドの大きさが大きく異なる２種類の光導波路を同一基板上に形成する光導波回路において、石英系光導波路の製造上必須である高温処理が、シリコンフォトニクス回路の形状や性能を劣化させることを防ぐことにある。 The purpose of the present invention is to provide an optical waveguide circuit in which two types of optical waveguides with significantly different mode field sizes, such as silicon photonics and quartz optical waveguides, are formed on the same substrate, which is essential for the production of silica optical waveguides. The goal is to prevent high-temperature processing from deteriorating the shape and performance of silicon photonics circuits.
　本開示は、このような目的を達成するために、以下のような構成を備えることを特徴とする。 In order to achieve such an objective, the present disclosure is characterized by having the following configuration.
　（構成１）
　基板の上に、少なくとも２種類の光導波路を形成した光導波回路であって、
　基板の上に形成されたアンダークラッド層と、
　アンダークラッド層の上に形成された第２の光導波路のコアと、
　第２の光導波路のコアの上に、第２の光導波路のコアよりも屈折率が高い材料で形成された第１の光導波路のコアと、
　第２の光導波路のコアと第１の光導波路のコアとを包み込む形状で、アンダークラッド層の上に、第２の光導波路のコアよりも屈折率の低い材料で形成された、オーバークラッド層とを備える
ことを特徴とする光導波回路。 (Configuration 1)
An optical waveguide circuit in which at least two types of optical waveguides are formed on a substrate,
an underclad layer formed on the substrate;
a second optical waveguide core formed on the undercladding layer;
A core of a first optical waveguide formed of a material having a higher refractive index than the core of the second optical waveguide on the core of the second optical waveguide;
An over cladding layer having a shape that wraps around the core of the second optical waveguide and the core of the first optical waveguide, and formed of a material having a lower refractive index than the core of the second optical waveguide on the under cladding layer. An optical waveguide circuit comprising:
　（構成２）
　基板の上に、少なくとも２種類の異なる光導波路であって、第２の光導波路のコアよりも屈折率が高い材料で形成されたコアを有する第１の光導波路と第２の光導波路からなる光導波回路の製造方法であって、
　基板に第２の光導波路のコアを形成する材料を成膜する工程と、
　当該第２の光導波路のコアを形成する材料からなる膜の加熱処理を行なう加熱処理工程と、
　加熱処理工程の後に、第２の光導波路上に、第１の光導波路のコアを形成する材料の層を成膜して形成する工程を含むことを特徴とする光導波回路の製造方法。 (Configuration 2)
A first optical waveguide and a second optical waveguide each having a core formed of a material having a higher refractive index than the core of the second optical waveguide, which are at least two different types of optical waveguides on the substrate. A method for manufacturing an optical waveguide circuit, the method comprising:
a step of depositing a material forming the core of the second optical waveguide on the substrate;
a heat treatment step of heating a film made of a material forming the core of the second optical waveguide;
A method for manufacturing an optical waveguide circuit, comprising the step of forming a layer of a material forming the core of the first optical waveguide on the second optical waveguide after the heat treatment step.
　この構成によれば、モードフィールドの大きさが大きく異なる２種類の光導波路を同一基板上に形成する光導波回路において、第２の光導波路の製造上必須である高温処理が、第１の光導波路の形状や性能を劣化させることを防ぐことができる。 According to this configuration, in an optical waveguide circuit in which two types of optical waveguides with significantly different mode field sizes are formed on the same substrate, the high temperature treatment that is essential for manufacturing the second optical waveguide is performed on the first optical waveguide. It is possible to prevent deterioration of the wave path shape and performance.
図１は、本発明の実施形態の光導波路回路を示す図である。FIG. 1 is a diagram showing an optical waveguide circuit according to an embodiment of the present invention. 図２は、本発明の実施形態の光導波回路の製造方法を示す図である。FIG. 2 is a diagram showing a method for manufacturing an optical waveguide circuit according to an embodiment of the present invention. 図３は、従来のＳＳＣ構造を備えるシリコン光回路を示す図である。FIG. 3 is a diagram illustrating a silicon optical circuit with a conventional SSC structure.
　以下、図面を参照しながら本発明の実施形態について詳細に説明する。
図１を用いて、本発明の実施の形態である光導波回路１００について説明する。図１は、本発明の実施形態の光導波回路１００が示されており、基板１０１と、アンダークラッド層１０２と、異なるＭＦＤを持つ２つの光導波路１１０、１２０と、光導波路１１０の光導波路コア１０４と、光導波路１２０の光導波路コア１０３と、ＭＦＤの差異の影響を緩和するためのＳＳＣ領域１３０と、オーバークラッド層１０５とを含む光導波回路１００の構造が示されている。図１（ａ）は、光導波路回路１００の光導波路コア１０４を通る（図１（ｂ）の断面線Ｉａ－Ｉａを通る）ＸＺ平面断面図であり、図１（ｂ）は、２つの光導波路の各コア１０４、１０３の中心を通る側面（図１（ａ）に示す断面線Ｉｂ－Ｉｂを通る）のＹＺ平面断面図である。図１（ｃ）は、光導波回路１００の図１（ｂ）に示す断面線Ｉｃ－Ｉｃを通るＸＹ平面断面図であり、同様に、図１（ｄ）、図１(ｅ)は、それぞれ図１（ｂ）の断面線Ｉｄ－Ｉｄ、断面線Ｉｅ－Ｉｅを通るＸＹ平面断面図である。図１の光導波回路１００は、共通の基板１０１の上に形成された第１の光導波路１１０と第２の光導波路１２０の異なる２種類の光導波路が光学的に接続された構造を備えている。 Embodiments of the present invention will be described in detail below with reference to the drawings.
An optical waveguide circuit 100, which is an embodiment of the present invention, will be described using FIG. 1. FIG. 1 shows an optical waveguide circuit 100 according to an embodiment of the present invention, which includes a substrate 101, an undercladding layer 102, two optical waveguides 110 and 120 having different MFDs, and an optical waveguide core of the optical waveguide 110. 104, an optical waveguide core 103 of an optical waveguide 120, an SSC region 130 for mitigating the effects of MFD differences, and an overcladding layer 105. 1(a) is an XZ plane cross-sectional view passing through the optical waveguide core 104 of the optical waveguide circuit 100 (passing along the cross-sectional line Ia-Ia in FIG. 1(b)), and FIG. 1(b) is a cross-sectional view of the two optical waveguides. FIG. 2 is a YZ plane cross-sectional view of a side surface passing through the center of each core 104, 103 of the wave path (passing along the cross-sectional line Ib-Ib shown in FIG. 1(a)). FIG. 1(c) is an XY plane cross-sectional view of the optical waveguide circuit 100 taken along the cross-sectional line Ic-Ic shown in FIG. 1(b), and similarly, FIG. 1(d) and FIG. 1(e) are FIG. 1B is an XY plane cross-sectional view taken along the cross-section line Id-Id and the cross-section line Ie-Ie in FIG. 1(b). The optical waveguide circuit 100 in FIG. 1 has a structure in which two different types of optical waveguides, a first optical waveguide 110 and a second optical waveguide 120, formed on a common substrate 101 are optically connected. There is.
　図１（ｂ）を参照すると、基板１０１の上に、アンダークラッド層１０２が形成されており、アンダークラッド層１０２の上に第２の光導波路コア１０３が形成されている。そして、第２の光導波路コア１０３の上に第１の光導波路コア１０４が形成されている。また、第２の光導波路コア１０３、第１の光導波路コア１０４を包み込む形状で、アンダークラッド層１０２の上にオーバークラッド層１０５が形成されている。 Referring to FIG. 1(b), an underclad layer 102 is formed on the substrate 101, and a second optical waveguide core 103 is formed on the underclad layer 102. A first optical waveguide core 104 is formed on the second optical waveguide core 103. Further, an overcladding layer 105 is formed on the undercladding layer 102 in a shape that wraps around the second optical waveguide core 103 and the first optical waveguide core 104 .
　図１の各図には、例示のために、第１の実施形態に係る、２つの光導波路１１０、１２０が基板１０１上に一体集積された光回路の一部だけを切り出して示しており、光導波路の数はこれに限られないし、また他の光導波路が回路内に含まれていてもよい。
また、図１では、第２の光導波路コア１０３の上面と第１の光導波路コア１０４の底面が接している形状が示されているが、本実施形態においては、第２の光導波路コア１０３よりも上方に第１の光導波路コア１０４が配置されるという位置関係が満たされれば、二つのコアは互いに接していなくてもよい。 For illustrative purposes, each figure in FIG. 1 shows only a part of the optical circuit according to the first embodiment in which two optical waveguides 110 and 120 are integrally integrated on a substrate 101. The number of optical waveguides is not limited to this, and other optical waveguides may be included in the circuit.
Further, although FIG. 1 shows a shape in which the top surface of the second optical waveguide core 103 and the bottom surface of the first optical waveguide core 104 are in contact with each other, in this embodiment, the second optical waveguide core 103 The two cores do not need to be in contact with each other as long as the positional relationship that the first optical waveguide core 104 is arranged above is satisfied.
　第１の光導波路１１０および第２の光導波路１２０を構成する材料は、屈折率が、第１の光導波路のコア＞第２の光導波路のコア＞第２の光導波路のクラッド、であるという関係を満たしていればよく、材料は限定されない。本実施形態の説明における例示のための具体例として、第１の光導波路のコアの材料が単結晶シリコン（Ｓｉ）、第２の光導波路のコアの材料が相対的に屈折率の高いＳｉＯ２、第２の光導波路のクラッドの材料が相対的に屈折率の低いＳｉＯ２などの、ＳｉＯ２を母材とする石英系ガラスの場合で説明するが、使用する材料はこれに限られない。たとえば、第1の光導波路のコアの材料としてＳｉ，ＳｉＮ，ＳｉＯＮなどを使用することができ、第２の光導波路の材料としてＳｉＯ２、ＳｉＯｘ、ポリマーなどが使用できる。 The materials constituting the first optical waveguide 110 and the second optical waveguide 120 have a refractive index such that the core of the first optical waveguide>core of the second optical waveguide>the cladding of the second optical waveguide. The material is not limited as long as it satisfies the relationship. As a specific example for illustrative purposes in the description of this embodiment, the material of the core of the first optical waveguide is single crystal silicon (Si), and the material of the core of the second optical waveguide is SiO 2 having a relatively high refractive index. , a case will be explained in which the material of the cladding of the second optical waveguide is a silica-based glass having SiO 2 as a base material, such as SiO 2 having a relatively low refractive index, but the material used is not limited to this. For example, Si, SiN, SiON, etc. can be used as the core material of the first optical waveguide, and SiO 2 , SiOx, polymer, etc. can be used as the material of the second optical waveguide.
　第１の光導波路１１０と第２の光導波路１２０のいずれも、コア断面サイズに上限はなく、使用する光信号の波長に対して、複数のモードの光を伝搬させるマルチモードの光導波路とすることもできる。また、コア断面サイズを小さくすることで、最低次のモードのみを伝搬させるシングルモードの光導波路とすることもできる。 Both the first optical waveguide 110 and the second optical waveguide 120 have no upper limit on the core cross-sectional size, and are multimode optical waveguides that propagate light in multiple modes for the wavelength of the optical signal used. You can also do that. Furthermore, by reducing the core cross-sectional size, it is possible to create a single-mode optical waveguide that propagates only the lowest-order mode.
　本実施形態の光導波路回路を、例えば、第１の光導波路１１０のコア１０４をＳｉコアとし、第２の光導波路１２０のコア１０３をＳｉＯ２コアとし、オーバークラッド層１０５をＳｉＯ２クラッドとして形成することができる。 In the optical waveguide circuit of this embodiment, for example, the core 104 of the first optical waveguide 110 is formed as a Si core, the core 103 of the second optical waveguide 120 is formed as a SiO 2 core, and the overcladding layer 105 is formed as a SiO 2 cladding. can do.
　この例示の構成では、第１の光導波路は、シリコン細線導波路として、第２の光導波路は平面光導波路として形成されることになる。この場合には、第１の光導波路１１０のコアークラッド間の屈折率差は大きく、そのため、コア断面サイズを数１００ｎｍ角まで小さくすることができる。一方、コア、クラッドともにＳｉＯ２を用いる第２の光導波路１２０は、コアークラッド間の屈折率差が第１の光導波路に比べて小さい。そのため、第２の光導波路のコア断面サイズは、数μｍ～１０μｍ角程度までとなる。 In this exemplary configuration, the first optical waveguide is formed as a silicon wire waveguide, and the second optical waveguide is formed as a planar optical waveguide. In this case, the difference in refractive index between the core and cladding of the first optical waveguide 110 is large, and therefore the core cross-sectional size can be reduced to several hundreds of nanometers square. On the other hand, in the second optical waveguide 120 in which both the core and the cladding are made of SiO 2 , the difference in refractive index between the core and cladding is smaller than that in the first optical waveguide. Therefore, the core cross-sectional size of the second optical waveguide ranges from several μm to about 10 μm square.
　第１の光導波路１１０、第２の光導波路１２０のいずれもがシングルモードの光導波路である場合、コア断面サイズは、第1の光導波路は数１００ｎｍ角程度、第２の光導波路は数μｍ～１０μｍ角程度となる。そのため、二つの導波路のコア内を伝搬するモードフィールドの大きさ（モードフィールド径：ＭＦＤ）は互いに著しく異なり、第２の光導波路１２０のＭＦＤが第１の光導波路１１０のＭＦＤに比べて大きな値となる。 When both the first optical waveguide 110 and the second optical waveguide 120 are single-mode optical waveguides, the core cross-sectional size of the first optical waveguide is about several hundred nm square, and the second optical waveguide is several μm square. ~10μm square. Therefore, the magnitudes of the mode fields propagating within the cores of the two waveguides (mode field diameter: MFD) are significantly different from each other, and the MFD of the second optical waveguide 120 is larger than that of the first optical waveguide 110. value.
　(接続方式)
　第１の光導波路と第２の光導波路の接続部分には、第１の光導波路のコア（Ｓｉコア）１０４内を伝搬するモードフィールドの大きさ（モードフィールド径：ＭＦＤ）を徐々に拡大させる機能、すなわちスポットサイズ変換（ＳＳＣ）機能を有する領域、ＳＳＣ領域１３０がある。本実施形態において、ＳＳＣ機能を実現するための構造は問わないが、たとえば、第１の光導波路コア（Ｓｉコア）１０４を先細りのテーパ形状とする構造によって実現することができる。また、第１の光導波路コア（Ｓｉコア）１０４の高さが徐々に低くなる基板垂直方向のテーパ形状を有してもよく、もしくは、第１の光導波路コア（Ｓｉコア）１０４が光の伝搬方向に分断されたセグメント状の構造によっても実現することができる。さらに、テーパ形状とセグメント形状の両方を組み合わせてもよい。 (Connection method)
At the connecting portion between the first optical waveguide and the second optical waveguide, the size of the mode field (mode field diameter: MFD) propagating within the core (Si core) 104 of the first optical waveguide is gradually expanded. There is an area having a spot size conversion (SSC) function, an SSC area 130. In this embodiment, the structure for realizing the SSC function does not matter; for example, it can be realized by a structure in which the first optical waveguide core (Si core) 104 has a tapered shape. Further, the first optical waveguide core (Si core) 104 may have a tapered shape in the vertical direction of the substrate such that the height gradually decreases, or the first optical waveguide core (Si core) 104 may have a tapered shape in the vertical direction of the substrate. It can also be realized by a segment-like structure divided in the propagation direction. Furthermore, both the tapered shape and the segmented shape may be combined.
　(接続損失)
　シングルモードとなるコア同士を接続させる方式は２種類に大別される。一つの接続方式は断熱結合であり、２つのコアを伝搬方向に対して接するように配置し、一方のコアを、先細りのテーパ形状にするなどしてコア内を伝搬するモードの等価屈折率を徐々に減少させることで、もはや閉じ込めきれなくなったモードの光エネルギーが、隣接する他方のコアへと断熱的に遷移する。もう一つの接続方式は突き合わせ結合であり、コアどうしの端面を突き合わせて配置し、２つのコアそれぞれに存在するモードプロファイルの重なり積分でその結合効率が規定される。 (Connection loss)
There are two main types of methods for connecting cores in single mode. One connection method is adiabatic coupling, in which two cores are arranged so as to be in contact with each other in the propagation direction, and one core is made into a tapered shape so that the equivalent refractive index of the mode propagating within the core is By gradually decreasing the amount, the optical energy of the mode that can no longer be confined is adiabatically transferred to the other adjacent core. Another connection method is butt coupling, in which cores are arranged with their end surfaces butted against each other, and the coupling efficiency is defined by the overlapping integral of the mode profiles existing in each of the two cores.
　ＳＳＣ領域１３０において、第１の光導波路コア（Ｓｉコア）１０４をたとえば先細りのテーパ形状とすることによって、第１の光導波路コア（Ｓｉコア）１０４内を伝搬する光エネルギーを、隣接する第２の光導波路コア（ＳｉＯ２コア）１０３へと断熱的に遷移させることができる。特に、テーパ構造である第１の光導波路コア（Ｓｉコア）１０４の先端を十分に細く加工することによって、断熱遷移する光エネルギーを最大化することができる。たとえばテーパ先端の幅を０．１μｍ以下の細さに加工することで、第１の光導波路コア（Ｓｉコア）１０４を伝搬する、基板水平方向の偏波成分の光エネルギーの９０％以上を、第２の光導波路コア（ＳｉＯ２コア）１０３へと断熱遷移させることができる。 In the SSC region 130, by forming the first optical waveguide core (Si core) 104 into a tapered shape, the optical energy propagating within the first optical waveguide core (Si core) 104 is transferred to an adjacent second optical waveguide core. can be adiabatically transitioned to the optical waveguide core (SiO 2 core) 103. In particular, by processing the tip of the first optical waveguide core (Si core) 104 having a tapered structure to be sufficiently thin, it is possible to maximize the optical energy that undergoes adiabatic transition. For example, by processing the width of the taper tip to be as thin as 0.1 μm or less, more than 90% of the optical energy of the polarized wave component in the horizontal direction of the substrate propagating through the first optical waveguide core (Si core) 104 can be Adiabatic transition can be made to the second optical waveguide core (SiO 2 core) 103.
　(製造方法)
　図２を用いて、上記の実施形態に係る光導波回路１００の製造方法を説明する。図２の図２（ａ）は、ＸＹ面側から見た構造を示す端面図であり、図２（ｂ）は、図２（ａ）に示す断面線ＩＩｂ－ＩＩｂを通るＹＺ面側から見た構造を示す断面図である。同様に、図２（ｃ）、図２（ｅ）、図２（ｇ）は、それぞれＸＹ面側から見た構造を示す端面図であり、図２（ｄ）は図２（ｃ）に示す断面線ＩＩｄ－ＩＩｄを、図２（ｆ）は図２（ｅ）に示す断面線ＩＩｆ－ＩＩｆを、図２（ｈ）は図２（ｇ）に示す断面線ＩＩｈ－ＩＩｈを、通るＹＺ面側から見た構造を示す断面図である。 (Production method)
A method for manufacturing the optical waveguide circuit 100 according to the above embodiment will be explained using FIG. 2. 2(a) of FIG. 2 is an end view showing the structure seen from the XY plane side, and FIG. 2(b) is an end view showing the structure seen from the YZ plane side passing through the cross-sectional line IIb-IIb shown in FIG. 2(a). FIG. Similarly, FIGS. 2(c), 2(e), and 2(g) are end views showing the structure viewed from the XY plane, and FIG. 2(d) is shown in FIG. 2(c). A YZ plane passing through the cross-sectional line IId-IId, FIG. 2(f) through the cross-sectional line IIf-IIf shown in FIG. 2(e), and FIG. 2(h) through the cross-sectional line IIh-IIh shown in FIG. It is a sectional view showing the structure seen from the side.
　図２（ａ）および図２（ｂ）に示す光導波回路１００を形成する基板は、つぎの工程により作成される。直上にＳｉＯ２層を成膜可能な、表面が平滑な基板１０１（具体例としてガラス基板等が挙げられるが、特にＳｉ基板が好適である）の上に、ＳｉＯ２層１０２を形成する。ＳｉＯ２層１０２の形成方法については、形成した層の直上に他の層を形成可能な程度に、均一かつ平滑な層を形成できれば方法は問わないが、たとえば火炎堆積法などの成膜方法を用いることができる。ＳｉＯ２層１０２の直上には、ＳｉＯ２層１０２よりも高い屈折率を有するＳｉＯ２層２０３を形成する。ＳｉＯ２層２０３の形成にあたっては、ＧｅＯ２、ＺｒＯ２、ＨｆＯ２、Ｐ２Ｏ５やＢ２Ｏ３などを添加することで屈折率を制御してもよい。ＳｉＯ２層２０３の形成方法については、たとえば火炎堆積法などの成膜方法を用いることができる。ＳｉＯ２層２０３を成膜したのちに、膜の透明化および屈折率の均一化を目的に、膜に対して１０００℃を超える加熱処理を施す。その後、ＳｉＯ２層２０３をＣＭＰ（Ｃｈｅｍｉｃａｌ　Ｍｅｃｈａｎｉｃａｌ　Ｐｏｌｉｓｈｉｎｇ）などの手段により平たん化する工程を経たのち、ＳｉＯ２層２０３の直上にＳｉ層２０４を形成し、平たん化して、図２（ａ）および図２（ｂ）の多層基板を作成する。Ｓｉ層２０４の形成にあたっては、アモルファスシリコンのスパッタリングなどで製膜しても構わないし、別のＳｉ基板を基板１０１の上面（ＳｉＯ２層２０３上）に貼り合わせたのちに、所望のＳｉ膜厚を得てもよい。図２（ａ）および図２（ｂ）の多層基板は、一般的なＳＯＩ（Ｓｉｌｉｃｏｎ ｏｎ Ｉｎｓｔｕｌａｔｏｒ）基板の表層のＳｉ層の下に形成される単層のＳｉＯ２層、すなわちＢＯＸ（Ｂｕｒｉｄｅｄ Ｏｘｉｄｅ）層の代わりに、屈折率の異なる２層のＳｉＯ２層、すなわちＳｉＯ２層１０２とＳｉＯ２層２０３を形成したものといえる。なお、ＳｉＯ２層２０３とＳｉ層２０４の間に、ＳｉＯ２層２０３およびＳｉ層２０４よりも屈折率の低い材料層を形成してもよい。 The substrate forming the optical waveguide circuit 100 shown in FIGS. 2(a) and 2(b) is produced by the following steps. A SiO 2 layer 102 is formed on a substrate 101 with a smooth surface (specific examples include a glass substrate, but a Si substrate is particularly preferred) on which a SiO 2 layer can be formed. Regarding the method of forming the SiO 2 layer 102, any method may be used as long as it can form a uniform and smooth layer to the extent that another layer can be formed directly above the formed layer, but for example, a film forming method such as a flame deposition method may be used. Can be used. Directly above the SiO 2 layer 102, a SiO 2 layer 203 having a higher refractive index than the SiO 2 layer 102 is formed. When forming the SiO 2 layer 203, the refractive index may be controlled by adding GeO 2 , ZrO 2 , HfO 2 , P 2 O 5 , B 2 O 3 or the like. As for the method of forming the SiO 2 layer 203, a film forming method such as a flame deposition method can be used, for example. After forming the SiO 2 layer 203, the film is subjected to heat treatment at a temperature exceeding 1000° C. for the purpose of making the film transparent and making the refractive index uniform. Thereafter, after going through a process of flattening the SiO 2 layer 203 by means such as CMP (Chemical Mechanical Polishing), a Si layer 204 is formed directly on the SiO 2 layer 203 and is flattened, as shown in FIG. 2(a). Then, the multilayer substrate shown in FIG. 2(b) is created. The Si layer 204 may be formed by sputtering amorphous silicon, or after bonding another Si substrate to the upper surface of the substrate 101 (on the SiO 2 layer 203), the Si layer 204 may be formed to a desired Si film thickness. You may obtain. The multilayer substrates shown in FIGS. 2(a) and 2(b) are made of a single SiO 2 layer formed under the surface Si layer of a general SOI (Silicon on Insulator) substrate, that is, a BOX (Buried Oxide). It can be said that two SiO 2 layers having different refractive indexes, that is, the SiO 2 layer 102 and the SiO 2 layer 203, are formed instead of the two SiO 2 layers. Note that a material layer having a lower refractive index than the SiO 2 layer 203 and the Si layer 204 may be formed between the SiO 2 layer 203 and the Si layer 204.
　つぎに、図２（ｃ）および図２（ｄ）に示すように、図２（ａ）および図２（ｂ）の多層基板のＳｉ層２０４を、第１の光導波路コア（１０４）として光を伝搬させることができるように加工し、Ｓｉコア１０４を形成する。図には示されていないが、Ｓｉコア１０４の形成と併せて、Ｓｉフォトニクスの光回路を形成してもよい。 Next, as shown in FIGS. 2(c) and 2(d), the Si layer 204 of the multilayer substrate of FIGS. 2(a) and 2(b) is used as the first optical waveguide core (104) to provide light. The Si core 104 is formed by processing the Si core 104 so that it can propagate. Although not shown in the figure, an optical circuit for Si photonics may be formed in conjunction with the formation of the Si core 104.
　続いて、図２（ｅ）及び図２（ｆ）に示すように、さらに、ＳｉＯ２層２０３を、第２の光導波路のコア１０３として光を伝搬させることができるように加工し、ＳｉＯ２コア１０３を形成する。このとき、すでに加工されているＳｉコア１０４の幅よりも、ＳｉＯ２コア１０３の幅は広いことが望ましい。これにより、ＳｉＯ２コア１０３の加工による、すでに加工されているＳｉコア１０４の側壁への影響をなくすようにできる。最後に、図２（ｇ）および図２（ｈ）に示すように、ＳｉＯ２コア１０３よりも低い屈折率を有するＳｉＯ２層１０５を形成して、光導波路回路を作製する。 Subsequently, as shown in FIGS. 2(e) and 2(f), the SiO 2 layer 203 is further processed to allow light to propagate as the core 103 of the second optical waveguide . A core 103 is formed. At this time, it is desirable that the width of the SiO 2 core 103 is wider than the width of the Si core 104 that has already been processed. Thereby, it is possible to eliminate the influence of the processing of the SiO 2 core 103 on the side wall of the Si core 104 that has already been processed. Finally, as shown in FIGS. 2(g) and 2(h), a SiO 2 layer 105 having a lower refractive index than the SiO 2 core 103 is formed to fabricate an optical waveguide circuit.
　ここでの製造方法の説明においては、説明の便宜のために、第１の光導波路および第２の光導波路を、それぞれ、ＳｉＯ２コア１０３、Ｓｉコア１０４、ＳｉＯ２クラッド層１０５等により構成されるものを例示して説明した。上述したように、第１の光導波路１１０および第２の光導波路１２０を構成する材料は、屈折率が、第１の光導波路のコア＞第２の光導波路のコア＞第２の光導波路のクラッド、であるという関係を満たしていればよく、使用する材料は限定されない。 In the explanation of the manufacturing method here, for convenience of explanation, the first optical waveguide and the second optical waveguide are each composed of a SiO 2 core 103, a Si core 104, a SiO 2 cladding layer 105, etc. We have given examples and explanations. As described above, the materials constituting the first optical waveguide 110 and the second optical waveguide 120 have a refractive index such that the core of the first optical waveguide > the core of the second optical waveguide > the core of the second optical waveguide. The material to be used is not limited as long as it satisfies the relationship: cladding.
　この製造方法によれば、第２の光導波路のコア（ＳｉＯ２コア）１０３の透明化および屈折率の均一化のために必須の工程である、ＳｉＯ２層２０３への高温処理は、Ｓｉ層２０４の形成ないしはＳｉ層２０４の加工による第１の光導波路コア（Ｓｉコア１０４）の形成よりも前段階の工程で完了している。そのため、Ｓｉコア１０４は、ＳｉＯ２コア１０３形成のために必須である高温処理にさらされることがなく、Ｓｉコア１０４加工時の形状および特性を維持した光導波路回路を作製することができる。 According to this manufacturing method, the high-temperature treatment of the SiO 2 layer 203, which is an essential step for making the core (SiO 2 core) 103 of the second optical waveguide transparent and uniformizing the refractive index, is performed on the SiO 2 layer 203. 204 or processing of the Si layer 204 to form the first optical waveguide core (Si core 104). Therefore, the Si core 104 is not exposed to the high-temperature treatment that is essential for forming the SiO 2 core 103, and an optical waveguide circuit that maintains the shape and characteristics when the Si core 104 was processed can be manufactured.
　（発明の効果）
本実施形態によれば、モードフィールドの大きさが大きく異なる２種類の光導波路を同一基板上に形成する光導波回路において、第２の光導波路の製造上必須である高温処理が、第１の光導波路の形状や性能を劣化させることを防ぐことができる。 (Effect of the invention)
According to this embodiment, in an optical waveguide circuit in which two types of optical waveguides with significantly different mode field sizes are formed on the same substrate, the high temperature treatment that is essential for manufacturing the second optical waveguide is performed on the first optical waveguide. It is possible to prevent deterioration of the shape and performance of the optical waveguide.
　以上のように、本発明によれば、シリコンフォトニクスと石英系光導波路のような、モードフィールドの大きさが大きく異なる２種類の光導波路を同一基板上に形成する光導波回路において、石英系光導波路の上層にシリコンフォトニクス回路を形成することで、石英系光導波路の製造上必須である高温処理が、シリコンフォトニクス回路の形状や性能を劣化させることを防ぐことができる。 As described above, according to the present invention, in an optical waveguide circuit in which two types of optical waveguides with significantly different mode field sizes, such as silicon photonics and quartz-based optical waveguides, are formed on the same substrate, silica-based optical waveguides can be used. By forming the silicon photonics circuit in the upper layer of the waveguide, it is possible to prevent the high-temperature treatment that is essential for manufacturing silica-based optical waveguides from deteriorating the shape and performance of the silicon photonics circuit.

Claims (7)

  1. 　基板の上に、少なくとも２種類の光導波路を形成した光導波回路であって、
    　前記基板の上に形成されたアンダークラッド層と、
    　前記アンダークラッド層の上に形成された第２の光導波路のコアと、
    　前記第２の光導波路のコアの上に、前記第２の光導波路のコアよりも屈折率が高い材料で形成された第１の光導波路のコアと、
    　前記第２の光導波路のコアと前記第１の光導波路のコアとを包み込む形状で、前記アンダークラッド層の上に、前記第２の光導波路のコアよりも屈折率の低い材料で形成された、オーバークラッド層とを備える
    ことを特徴とする光導波回路。     An optical waveguide circuit in which at least two types of optical waveguides are formed on a substrate,
    an undercladding layer formed on the substrate;
    a core of a second optical waveguide formed on the underclad layer;
    A core of a first optical waveguide formed of a material having a higher refractive index than the core of the second optical waveguide on the core of the second optical waveguide;
    It has a shape that envelops the core of the second optical waveguide and the core of the first optical waveguide, and is formed of a material having a lower refractive index than the core of the second optical waveguide on the under cladding layer. An optical waveguide circuit comprising: , and an overcladding layer.
  2. 　前記第１の光導波路および前記第２の光導波路は、導波する光信号波長に対してシングルモード導波路である
    ことを特徴とする請求項１に記載の光導波回路。     2. The optical waveguide circuit according to claim 1, wherein the first optical waveguide and the second optical waveguide are single mode waveguides with respect to the wavelength of the optical signal to be guided.
  3. 　前記第１の光導波路と前記第２の光導波路の接続部分において、
    　前記第１の光導波路のコアの先端部が、前記第１の光導波路を伝搬する光信号のモードフィールド径を変化させる構造を有する
    ことを特徴とする請求項１または２に記載の光導波回路。     In the connecting portion between the first optical waveguide and the second optical waveguide,
    3. The optical waveguide circuit according to claim 1, wherein the tip of the core of the first optical waveguide has a structure that changes a mode field diameter of an optical signal propagating through the first optical waveguide. .
  4. 前記モードフィールド径を変化させる構造は、
    水平面内あるいは垂直面内においてテーパ形状に径変化する構造であるか、
    コアが断続的に形成される（コアが形成されている領域と形成されていない領域が交互に繰り返される）構造であるか、
    またはその両方を組み合わせた構造である
    ことを特徴とする請求項３に記載の光導波回路。     The structure for changing the mode field diameter is
    Is it a structure in which the diameter changes in a tapered shape in the horizontal or vertical plane?
    Is the structure in which the core is formed intermittently (regions where the core is formed and regions where it is not formed are repeated alternately)?
    4. The optical waveguide circuit according to claim 3, wherein the optical waveguide circuit has a structure that is a combination of the two or both.
  5. 前記第１の光導波路のコアは単結晶シリコンからなり、
    前記アンダークラッド層、前記第２の光導波路のコア、および前記オーバークラッド層はＳｉＯ２を母材とする石英系ガラスからなる
    ことを特徴とする請求項１または２に記載の光導波回路。     The core of the first optical waveguide is made of single crystal silicon,
    3. The optical waveguide circuit according to claim 1, wherein the under-cladding layer, the core of the second optical waveguide, and the over-cladding layer are made of silica-based glass having SiO2 as a base material.
  6. 　基板の上に、少なくとも２種類の異なる光導波路であって、第２の光導波路のコアよりも屈折率が高い材料で形成されたコアを有する第１の光導波路と前記第２の光導波路からなる光導波回路の製造方法であって、
    　基板に前記第２の光導波路のコアを形成する材料を成膜する工程と、
    　当該前記第２の光導波路のコアを形成する材料からなる膜の加熱処理を行なう加熱処理工程と、
    　前記加熱処理工程の後に、前記第２の光導波路上に、前記第１の光導波路のコアを形成する材料の層を成膜して形成する工程を含むことを特徴とする光導波回路の製造方法。     On the substrate, there are at least two different types of optical waveguides, a first optical waveguide having a core made of a material having a higher refractive index than the core of the second optical waveguide, and the second optical waveguide. A method for manufacturing an optical waveguide circuit, comprising:
    forming a film of a material forming the core of the second optical waveguide on the substrate;
    a heating treatment step of heating a film made of a material forming the core of the second optical waveguide;
    Manufacturing an optical waveguide circuit, comprising a step of forming a layer of a material forming a core of the first optical waveguide on the second optical waveguide after the heat treatment step. Method.
  7. 　前記第１の光導波路のコアを形成する材料が単結晶シリコンであり、前記第２の光導波路のコアを形成する材料がＳｉＯ２を母材とする石英系ガラスであることを特徴とする請求項６に記載の光導波回路の製造方法。 A claim characterized in that the material forming the core of the first optical waveguide is single-crystal silicon, and the material forming the core of the second optical waveguide is silica-based glass having SiO 2 as a base material. Item 6. The method for manufacturing an optical waveguide circuit according to item 6.
PCT/JP2022/030790 2022-08-12 2022-08-12 Optical waveguide circuit and method for manufacturing optical waveguide circuit WO2024034131A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090003770A1 (en) * 2007-06-29 2009-01-01 Alcatel-Lucent Vertical optical coupling structure
JP2014202997A (en) * 2013-04-08 2014-10-27 富士通株式会社 Spot size converter, optical waveguide, and method of manufacturing spot size converter
WO2015011845A1 (en) * 2013-07-23 2015-01-29 独立行政法人産業技術総合研究所 Interlayer lightwave coupling device
JP2016045440A (en) * 2014-08-26 2016-04-04 日本電信電話株式会社 Fabrication method of optical waveguide
JP2016090711A (en) * 2014-10-31 2016-05-23 富士通株式会社 Optical waveguide, spot size converter and optical device
WO2020187777A1 (en) * 2019-03-15 2020-09-24 Ligentec Sa Optical mode-size converter

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090003770A1 (en) * 2007-06-29 2009-01-01 Alcatel-Lucent Vertical optical coupling structure
JP2014202997A (en) * 2013-04-08 2014-10-27 富士通株式会社 Spot size converter, optical waveguide, and method of manufacturing spot size converter
WO2015011845A1 (en) * 2013-07-23 2015-01-29 独立行政法人産業技術総合研究所 Interlayer lightwave coupling device
JP2016045440A (en) * 2014-08-26 2016-04-04 日本電信電話株式会社 Fabrication method of optical waveguide
JP2016090711A (en) * 2014-10-31 2016-05-23 富士通株式会社 Optical waveguide, spot size converter and optical device
WO2020187777A1 (en) * 2019-03-15 2020-09-24 Ligentec Sa Optical mode-size converter

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