Optical waveguide substrate and optical device

Abstract

The present invention relates to an optical waveguide substrate having: a cladding layer A which comprises glass and has a cladding region A and a core region having a higher refractive index than that of the cladding region A and that is located on the surface; and a cladding layer B which is bonded to the cladding layer A and has a cladding region B having a lower refractive index than that of the core region in the cladding layer A. In a glass constituting the cladding region A and a glass constituting the core region, the content ratios of Na2O and Ag2O satisfy specific relationships.

Description

Optical waveguide substrate and optical device

[0001] The present invention relates to an optical waveguide substrate and an optical device including the optical waveguide substrate.

[0002] In recent years, high-speed, large-capacity transmission technologies have been attracting attention, starting with 5G and 6G wireless transmission using microwaves and millimeter waves. In order to achieve even larger capacity and lower latency transmission, "photonics-electronics convergence technology" is being considered, which uses optical signals to transmit part of the communication that has previously been carried out electrically inside computers and other devices. By using optical signals instead of electrical signals, it is expected that low power consumption, large-capacity communication, and low-latency transmission will be possible.

[0003] In photonics and electronics convergence technology, a substrate that can transmit both electricity and light is required. ２ In contrast, the Si-Ge substrate doped with Ge and the surrounding Si are covered with SiO ２ Various materials are being considered, such as substrates of Si nanowires surrounded by a metal, and polymer-based substrates in which different types of polymers are bonded.

[0004] In response to the above, substrates using glass materials have begun to be considered from the viewpoints of heat resistance, rigidity, degree of integration of electrical communication transmission lines, cost, etc. For example, Patent Document 1 discloses that an optical waveguide can be formed by ion-exchanging Na ions in glass with Ag ions.

[0005] Japan Special Table No. 2021-511538 Publication Japanese Patent No. 7059993

[0006] The technique of exchanging ions in glass for other ions is known as a technique for increasing the strength of glass, as disclosed in, for example, Patent Document 2.

[0007] In response to this, the inventors have found that even if an optical waveguide is formed using the above-mentioned conventional ion exchange technology, it is difficult to obtain a stable optical waveguide that achieves control of the core thickness and high uniformity, and it is particularly difficult to form an optical waveguide that can accommodate single-mode propagated light.

[0008] Furthermore, in the above-mentioned Patent Document 1, in order to make the Ag-Na IOX (ion exchange) region that becomes the core region a buried type, in addition to ion exchange in which Na ions are converted into Ag ions, reverse ion exchange in which Ag ions are converted back into Na ions is also performed. However, when the core region is formed by the above-mentioned ion exchange and reverse ion exchange, it is difficult to form a core region with a sufficiently large refractive index at a position deep from the surface of the optical waveguide substrate.

[0009] In contrast to this, optical waveguide substrates used in CPO (Co-Packaged Optics) technology, which has been attracting attention in recent years, are required to have a core region deep below the substrate surface that has a large difference in refractive index from the cladding region.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical waveguide substrate in which a core region can be formed even at a deep position from the surface of the substrate, and an optical device including the optical waveguide substrate.

[0011] As a result of further investigations into the above-mentioned problems, the inventors discovered that even when the core region is formed by ion exchange, the above-mentioned problems can be solved by constructing the cladding region surrounding the core region from two or more different materials, and thus completed the present invention.

[0012] That is, the present invention relates to the following [1] to

[13] : [1] A fiber having a cladding layer A and a cladding layer B bonded to the cladding layer A, wherein the cladding layer A is made of glass having a cladding region A and a core region having a refractive index higher than that of the cladding region A, and the glass constituting the cladding region A contains, in mole % on an oxide basis, Na ２ The glass constituting the core region contains 5% or more of O, and ２ O and Ag ２ O, and more Na than the glass constituting the cladding region A. ２ The content of O is low and Ag ２an optical waveguide substrate having a high O content, the core region being located in a region including a part of the surface of the cladding layer A facing the cladding layer B, and the cladding layer B having a cladding region B having a lower refractive index than the core region of the cladding layer A. [2] The optical waveguide substrate according to [1] above, wherein the cladding layer B is composed of a glass layer or a resin layer, and the cladding layer A and the glass layer or the resin layer are directly bonded together. [3] The optical waveguide substrate according to [1] above, wherein the cladding layer B is composed of an adhesive layer and a glass layer or a resin layer, the adhesive layer having a thickness of less than 5 μm, the cladding region B is composed of the adhesive layer and the glass layer or the resin layer, and the cladding layer A and the cladding layer B are bonded together via the adhesive layer. [4] The optical waveguide substrate according to [1], wherein the cladding layer B is composed of an adhesive layer and a glass layer or a resin layer, the adhesive layer having a thickness of 5 μm or more, the cladding region B is composed of the adhesive layer, and the cladding layer A and the cladding layer B are bonded via the adhesive layer. [5] The optical waveguide substrate according to [3], wherein the difference in refractive index between the adhesive layer constituting the cladding region B and the glass constituting the cladding region A is 0.1 or less. [6] The optical waveguide substrate according to [4], wherein the difference in refractive index between the adhesive layer constituting the cladding region B and the glass constituting the cladding region A is 0 to 0.003, and the adhesive layer has a thickness of 5 to 100 μm. [7] The optical waveguide substrate according to any one of [1] to [6], wherein the dielectric loss tangent at 10 GHz of the material constituting the cladding region B is 0.01 or less. [8] The thermal expansion coefficient of the material constituting the cladding region B is 5×10 －７ ~120 x 10 －７ [9] The optical waveguide substrate according to any one of the above [1] to [7], wherein the cladding layer B is composed of the adhesive layer and the glass layer, and the glass constituting the cladding region B has a higher Na content than the glass constituting the cladding region A. ２ The optical waveguide substrate according to the above [3] or [5], wherein the glass constituting the cladding region A has a low content of SiO, expressed in mole percent on an oxide basis.２ 45-80%, Al ２ O ３ 0-15%, B ２ O ３ 0 to 20%, the total of MgO, CaO, SrO and BaO 10 to 30%, and Na ２

[11] The cladding layer B is composed of an adhesive layer and a glass layer, the adhesive layer has a thickness of 5 μm or more, the cladding region B is composed of the adhesive layer, and the glass constituting the glass layer of the cladding layer B contains, in mole percent on an oxide basis, SiO 5 to 25%. ２ 57-70%, Al ２ O ３ 5-15%, B ２ O ３ 15-24%, MgO 0.1-10%, CaO 0.1-10%, SrO 0.1-10%, BaO 0-10%, and ZnO 0-0.1%.

[12] The optical waveguide substrate according to any one of [1] to

[11] above, wherein in the cladding layer A, a difference between the maximum refractive index of the core region and the refractive index of the cladding region A is 0.003-0.06.

[13] An optical device comprising: the optical waveguide substrate according to any one of [1] to

[12] above; and an optical coupler that extracts at least a portion of light transmitted by the optical waveguide substrate to the outside.

[0013] The optical waveguide substrate according to the present invention allows the core region to be formed deep beneath the substrate surface, making it suitable for use in CPO (Co-Packaged Optics) technology.

[0014] FIG. 1 is a schematic cross-sectional view showing one aspect of an optical waveguide substrate 10 according to this embodiment. FIG. 2 is a schematic cross-sectional view showing one aspect of an optical waveguide substrate 10' according to this embodiment. FIG. 3 is a schematic cross-sectional view showing one aspect of an optical waveguide substrate 10'' according to this embodiment. FIG. 4 is a schematic cross-sectional view showing one aspect of an optical waveguide substrate 10''' according to this embodiment.

[0015] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified as desired without departing from the gist of the present invention. Furthermore, the term "to" indicating a range of values ​​is used to mean that the values ​​before and after it are included as the lower and upper limits. In this specification, mass ratio and weight ratio, and mass % and weight % have the same meaning.

[0016] <Optical Waveguide Substrate> As shown in Fig. 1, the optical waveguide substrate 10 according to this embodiment has a cladding layer A (11) and a cladding layer B (12) bonded to the cladding layer A (11). The cladding layer A (11) is made of glass having a cladding region A (21) and a core region (31), and the core region (31) has a higher refractive index than the cladding region A (21). Specifically, the glass constituting the cladding region A (21) in the cladding layer A (11) contains, in mole percent on an oxide basis, Na ２ The glass constituting the core region (31) in the cladding layer A (11) contains 5% or more of O. ２ O and Ag ２ O, and more Na than the glass constituting the cladding region A (21). ２ The content of O is low and Ag ２ The core region (31) is located in a region including a part of the surface of the cladding layer A (11) on the side of the cladding layer B (12). The cladding layer B (12) has a cladding region B (22), and the refractive index of the cladding region B (22) is lower than the refractive index of the core region (31) of the cladding layer A (11).

[0017] As a more specific example of the optical waveguide substrate 10' according to this embodiment, as shown in FIG. 2, the cladding layer B (12') is composed of a glass layer or a resin layer (32'), and the cladding layer A (11') and the glass layer or the resin layer (32') constituting the cladding layer B (12') are directly bonded to each other to form an optical waveguide.

[0018] In another specific embodiment of the optical waveguide substrate 10" according to this embodiment, as shown in FIG. 3, the cladding layer B (12") is composed of an adhesive layer (33") and a glass or resin layer (32"), and the thickness of the adhesive layer (33") is less than 5 μm. In this case, the cladding region B (22") in the cladding layer B (12") is composed of the adhesive layer (33") and the glass or resin layer (32"). The cladding layer A (11") and the cladding layer B (12") are bonded via the adhesive layer (33") of the cladding layer B (12") to form an optical waveguide.

[0019] In another specific embodiment of the optical waveguide substrate 10''' according to this embodiment, as shown in FIG. 4, the cladding layer B (12''') is composed of an adhesive layer (33''') and a glass or resin layer (32'''), and the thickness of the adhesive layer (33''') is 5 μm or more. In this case, the cladding region B (22''') of the cladding layer B (12''') is composed of the adhesive layer (33''', and the refractive index of the glass or resin layer (32''') is not particularly limited. That is, the refractive index of the glass or resin layer (32''') may be greater than, smaller than, or the same as the refractive index of the core region (31''') of the cladding layer A (11'''). The cladding layer A (11''') and the cladding layer B (12''') are bonded via the adhesive layer (33''') of the cladding layer B (12''') to form an optical waveguide.

[0020] Next, each component of the optical waveguide substrate will be described.

[0021] <Cladding Layer A> The cladding layer A (11) in this embodiment is made of glass having a cladding region A (21) and a core region (31).

[0022] Cladding Region A In this embodiment, the refractive index of the cladding region A (21) is lower than the refractive index of the core region (31). The core region (31) in the cladding layer A (11) is typically formed by ion-exchanging a portion of the cladding layer A (11). Therefore, the composition of the glass constituting the cladding region A (21) is identical to the composition of the base glass constituting the cladding layer A (11). In other words, in this specification, the base composition of the glass constituting the cladding layer A is considered to be identical to the composition of the glass constituting the cladding layer A before the ion-exchange treatment. Except for cases where extreme ion-exchange treatment has been performed, the composition of the portion deeper than the ion-exchange depth (DOL) in the ion-exchanged region is considered to be identical to the base composition of the glass constituting the cladding layer A. In other words, the composition of the glass at the center of the plate thickness of the glass constituting the cladding layer A and the composition of the glass constituting the cladding region A typically match the base composition of the glass constituting the cladding layer A.

[0023] The glass constituting the cladding region A (21) in this embodiment contains, in mole percent on an oxide basis, Na ２ Contains 5% or more of O and the above Na ２ The O content is preferably 5 to 25%, more preferably 6 to 22.5%, even more preferably 7 to 20%, even more preferably 8 to 17.5%, and particularly preferably 9 to 16%. ２ O is a component that imparts a high refractive index to the core portion to function as an optical waveguide by ion exchange with Ag ions, and also improves the melting property of the glass. ２ The content of O is 5% or more, preferably 6% or more, more preferably 7% or more, even more preferably 8% or more, and even more preferably 9% or more. ２ The O content is preferably 25% or less, more preferably 22.5% or less, even more preferably 20% or less, even more preferably 17.5% or less, and particularly preferably 16% or less.

[0024] In this embodiment, the glass constituting the cladding region A (21) may be, for example, silicate glass or aluminosilicate glass.

[0025] For example, the above glass contains, in mole percentage on an oxide basis, Na ２ In addition to containing 5% or more of O, the content of other components is ２ 45 to 80%, and Al ２ O ３ It is preferable that the content of SiO is 0 to 15%. ２ It is also preferable that the total content of MgO, CaO, SrO and BaO is 45 to 80%, and the total content of SiO is 10 to 30%. ２ 45-80%, Al ２ O ３ It is more preferable that the total content of MgO, CaO, SrO and BaO is 10 to 30%. ２ It is more preferable that the O content is 5 to 25%.

[0026] More specifically, the glass constituting the cladding region A (21) in this embodiment preferably satisfies the following composition range in mole percent based on oxides: SiO ２ 45-80%, Al ２ O ３ 0-15%, B ２ O ３ 0 to 20%, the total of MgO, CaO, SrO and BaO 10 to 30%, and Na ２ O 5-25%

[0027] In this embodiment, the glass constituting the cladding region A (21) contains Na. ２ Components other than O will also be described below. Note that "%" indicates mole percentage based on oxide.

[0028] SiO ２ The content of is preferably 40 to 80%, more preferably 45 to 80%, even more preferably 45 to 75%, even more preferably 50 to 70%, particularly preferably 52.5 to 67.5%, and particularly preferably 55 to 65%. ２The content of SiO is preferably 40% or more, more preferably 45% or more, even more preferably 50% or more, even more preferably 52.5% or more, and particularly preferably 55% or more. ２ The content is preferably 80% or less, more preferably 75% or less, even more preferably 70% or less, even more preferably 67.5% or less, and particularly preferably 65% ​​or less.

[0029] Al ２ O ３ The content of Al is preferably 0 to 15%, more preferably 1 to 12.5%, even more preferably 1.5 to 10%, even more preferably 2 to 8%, and particularly preferably 2.5 to 7.5%. ２ O ３ However, from the viewpoint of increasing the ion exchange rate and improving productivity, Al ２ O ３ The content of Al is preferably 1% or more, more preferably 1.5% or more, even more preferably 2% or more, and even more preferably 2.5% or more. In addition, from the viewpoint of reducing the ion exchange rate from Na ions to Ag ions in the glass, realizing a desired thickness for the core region (31), and forming a highly homogeneous core region (31), ２ O ３ The content is preferably 15% or less, more preferably 12.5% ​​or less, even more preferably 10% or less, even more preferably 8% or less, and particularly preferably 7.5% or less.

[0030] B ２ O ３ The content of is preferably 0 to 20%, more preferably 2 to 17.5%, even more preferably 4 to 15%, even more preferably 6 to 12.5%, and particularly preferably 8 to 11%. ２ O ３ However, from the viewpoint of improving melting property, B ２ O ３ The content of B is preferably 2% or more, more preferably 4% or more, even more preferably 6% or more, and even more preferably 8% or more. On the other hand, from the viewpoint of suppressing deterioration in quality as an optical waveguide substrate due to the generation of striae during melting, ２ O ３The content of B is preferably 20% or less, more preferably 17.5% or less, even more preferably 15% or less, even more preferably 12.5% ​​or less, and particularly preferably 11% or less. ２ O ３ It is preferable that it does not contain

[0031] The total content of alkaline earth metal oxides, represented by the sum of MgO, CaO, SrO, and BaO, is preferably 10 to 30%, more preferably 11 to 27.5%, even more preferably 12 to 25%, even more preferably 13 to 22.5%, and particularly preferably 14 to 20%. From the viewpoints of reducing the ion exchange rate from Na ions to Ag ions in the glass, achieving the desired thickness for the core region (31), and forming a highly homogeneous core region (31), the total content is preferably 10% or more, more preferably 11% or more, even more preferably 12% or more, even more preferably 13% or more, and particularly preferably 14% or more. Furthermore, from the viewpoints of increasing the ion exchange rate to a certain extent and thereby improving the productivity of optical waveguides, the total content is preferably 30% or less, more preferably 27.5% or less, even more preferably 25% or less, even more preferably 22.5% or less, and particularly preferably 20% or less.

[0032] The MgO content is preferably 0 to 20%, more preferably 1 to 18%, even more preferably 2 to 16%, even more preferably 3 to 14%, and particularly preferably 4 to 12%. MgO may not be contained, but from the viewpoint of improving the meltability of the glass and controlling the ion exchange rate, the MgO content is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and particularly preferably 4% or more. Furthermore, from the viewpoint of preventing devitrification during melting, the MgO content is preferably 20% or less, more preferably 18% or less, even more preferably 16% or less, even more preferably 14% or less, and particularly preferably 12% or less.

[0033] The CaO content is preferably 0 to 20%, more preferably 1 to 18%, even more preferably 2 to 16%, even more preferably 3 to 14%, particularly preferably 4 to 12%, and particularly preferably 4.5 to 12%. CaO may not be contained, but from the viewpoint of improving the meltability of the glass and controlling the ion exchange rate, the CaO content is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, even more preferably 4% or more, and particularly preferably 4.5% or more. Furthermore, from the viewpoint of preventing devitrification during melting, the CaO content is preferably 20% or less, more preferably 18% or less, even more preferably 16% or less, even more preferably 14% or less, and particularly preferably 12% or less.

[0034] The SrO content is preferably 0 to 20%, more preferably 1 to 18%, even more preferably 2 to 16%, even more preferably 3 to 14%, still more preferably 4 to 12%, and particularly preferably 4.5 to 12%. SrO may not be contained, but from the viewpoint of improving the meltability of the glass and controlling the ion exchange rate, the SrO content is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, even more preferably 4% or more, and particularly preferably 4.5% or more. Furthermore, from the viewpoint of preventing devitrification during melting, the SrO content is preferably 20% or less, more preferably 18% or less, even more preferably 16% or less, even more preferably 14% or less, and particularly preferably 12% or less.

[0035] The BaO content is preferably 0 to 20%, more preferably 1 to 18%, even more preferably 2 to 16%, even more preferably 3 to 14%, even more preferably 4 to 12%, and particularly preferably 4.5 to 12%. BaO may not be contained, but from the viewpoint of improving the meltability of the glass and controlling the ion exchange rate, the BaO content is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, even more preferably 4% or more, and particularly preferably 4.5% or more. Furthermore, from the viewpoint of preventing devitrification during melting, the BaO content is preferably 20% or less, more preferably 18% or less, even more preferably 16% or less, even more preferably 14% or less, and particularly preferably 12% or less.

[0036] Li ２ The O content is preferably 0 to 10%, more preferably 0.1 to 5%, even more preferably 0.3 to 4%, even more preferably 0.4 to 3%, and particularly preferably 0.5 to 2.5%. ２ Although O may not be contained, from the viewpoint of improving melting property, Li ２ The content of O is preferably 0.1% or more, more preferably 0.3% or more, even more preferably 0.4% or more, and particularly preferably 0.5% or more. On the other hand, from the viewpoint of increasing the difference Δn between the maximum refractive index Nmax of the cladding layer A (11) and the refractive index N of the cladding region A (21), as will be described later, Li ２ The O content is preferably 10% or less, more preferably 5% or less, even more preferably 4% or less, even more preferably 3% or less, and particularly preferably 2.5% or less.

[0037] K ２ The O content is preferably 0 to 10%, more preferably 0.1 to 5%, even more preferably 0.3 to 4%, even more preferably 0.4 to 3%, and particularly preferably 0.5 to 2.5%. ２ Although O may not be contained, from the viewpoint of improving melting property, K ２ The content of O is preferably 0.1% or more, more preferably 0.3% or more, even more preferably 0.4% or more, and even more preferably 0.5% or more. On the other hand, from the viewpoint of widening the refractive index difference between the core region (31) and the cladding region A (21), K ２ The O content is preferably 10% or less, more preferably 5% or less, even more preferably 4% or less, even more preferably 3% or less, and particularly preferably 2.5% or less.

[0038] P ２ O ５ The content of P is preferably 0 to 4%, more preferably 0.5 to 3%, and even more preferably 1 to 2%. ２ O ５ However, from the viewpoint of ion exchange performance and chipping resistance, P ２ O ５ The content of P is preferably 0.5% or more, more preferably 1% or more, and even more preferably 2% or more. ２ O ５The content of P is preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, and even more preferably 1% or less. ２ O ５ It is preferable that the glass composition is substantially free of these elements. In this specification, "substantially free of these elements" means that the glass composition is free of these elements except for unavoidable impurities contained in raw materials, etc., that is, is not intentionally added. Specifically, this means that the content of these elements in the glass composition is less than 0.1 mol%.

[0039] The ZnO content is preferably 0 to 10%, more preferably 0.25 to 7%, even more preferably 0.25 to 5%, even more preferably 0.5 to 2%, and particularly preferably 0.5 to 1%. ZnO may not be contained, but from the viewpoint of meltability, the ZnO content is preferably 0.25% or more, and more preferably 0.5% or more. On the other hand, from the viewpoint of weather resistance, the ZnO content is preferably 10% or less, more preferably 7% or less, even more preferably 5% or less, even more preferably 2% or less, and particularly preferably 1% or less.

[0040] TiO ２ The content of TiO is preferably 0 to 1%, more preferably 0.1 to 0.5%, even more preferably 0.15 to 0.5%, and even more preferably 0.2 to 0.25%. ２ However, from the viewpoint of crushability, TiO ２ The content of TiO is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.2% or more. ２ The content is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.25% or less.

[0041] ZrO ２ The content of ZrO is preferably 0 to 8%, more preferably 0.5 to 6%, even more preferably 0.5 to 4%, even more preferably 1 to 2%, and particularly preferably 1 to 1.2%. ２ However, from the viewpoint of improving weather resistance, ZrO ２The content of ZrO is preferably 0.5% or more, and more preferably 1% or more. ２ The content is preferably 8% or less, more preferably 6% or less, even more preferably 4% or less, even more preferably 2% or less, and particularly preferably 1.2% or less.

[0042] Y ２ O ３ , La ２ O ３ , Nb ２ O ５ The content of each of is preferably 0 to 8%, more preferably 0.5 to 6%, even more preferably 1 to 5%, even more preferably 1.5 to 4%, particularly preferably 2 to 3%, and particularly preferably 2.5 to 3%. ２ O ３ , La ２ O ３ , Nb ２ O ５ However, from the viewpoint of improving weather resistance, Y ２ O ３ , La ２ O ３ , Nb ２ O ５ The content of each of Y is preferably 0.5% or more, more preferably 1% or more, even more preferably 1.5% or more, even more preferably 2% or more, and particularly preferably 2.5% or more. On the other hand, from the viewpoint of suppressing deterioration in quality due to devitrification, ２ O ３ , La ２ O ３ , Nb ２ O ５ The content of each of these is preferably 8% or less, more preferably 6% or less, even more preferably 5% or less, even more preferably 4% or less, and particularly preferably 3% or less.

[0043] Ta ２ O ５ , Gd ２ O ３ The content of each of is preferably 0 to 1%, more preferably 0 to 0.5%. ２ O ５ , Gd ２ O ３However, from the viewpoint of improving weather resistance, a small amount of Ta may be contained. ２ O ５ , Gd ２ O ３ The content of each of these is preferably 1% or less, more preferably 0.5% or less, and even more preferably substantially none.

[0044] Furthermore, when the glass is used after being colored, a coloring component may be added within a range that does not impair the desired effect. ３ O ４ , MnO ２ , Fe ２ O ３ , NiO, CuO, Cr ２ O ３ , V ２ O ５ , Bi ２ O ３ , SeO ２ , TiO ２ , CeO ２ , Er ２ O ３ , Nd ２ O ３ etc.

[0045] The total content of the coloring components is preferably 0 to 7%, more preferably 0 to 5%, even more preferably 0 to 3%, and even more preferably 0 to 1%. From the viewpoint of suppressing devitrification, the total content of the coloring components is preferably 7% or less, more preferably 5% or less, even more preferably 3% or less, even more preferably 1% or less, and it is particularly preferable that the coloring components are substantially not contained.

[0046] In addition, when a coloring component is added, it is preferable that the coloring component does not absorb at the wavelength used. Specifically, the absorption coefficient in the wavelength range of 1300 to 1600 nm is 1 cm －１ Preferably less than 0.5 cm －１ It is more preferable that it is less than 0.1 cm －１ It is particularly preferable that the absorption coefficient is less than 0.0001 cm. －１ That's all.

[0047] SO 4 is used as a fining agent when melting glass.３ , chloride, fluoride, etc. may be contained as appropriate. ２ O ３ It is preferable that Sb is not substantially contained. ２ O ３ When it is contained, it is preferably 0.3% or less, more preferably 0.1% or less, and even more preferably it is substantially not contained.

[0048] Ag ２ O may be contained from the viewpoint of improving ion exchangeability, but Ag of the glass constituting the core region (31) ２ The content of Ag is lower than that of O. ２ O is a component used to increase the refractive index of the core region (31), so Ag ２ Even if O is contained, Ag in the cladding region A (21) ２ The content of O is preferably less than 0.01%, more preferably 0.005% or less, and even more preferably 0.001% or less. ２ It is even more preferable that the material does not substantially contain O. ２ With regard to O, "substantially free" means that the amount is below the detection limit of the device.

[0049] The refractive index of the cladding region A (21) is not particularly limited as long as it is lower than the refractive index of the core region (31). However, since the core region (31) is formed by ion exchange, the refractive index of the cladding region A (21) is higher in the region near the boundary with the core region (31) and is not constant. Therefore, in this embodiment, the refractive index of the cladding region A (21) is the refractive index of glass having the same composition as the matrix composition of the glass before ion exchange, i.e., the matrix glass. Note that in the case of the cladding layer A (11) in this embodiment, if the refractive index of the cladding region A (21) is sufficiently far from the core region (31), it will be the same as the refractive index of the matrix composition. Therefore, although it depends on the thickness of the cladding layer A (11), for example, the refractive index of the glass at the center of the plate thickness of the cladding layer A (11) may be used as the refractive index of the cladding region A (21).

[0050] Considering the refractive index of the matrix composition of glass commonly used for optical waveguides, the refractive index of the cladding region A (21) is preferably, for example, 1.50 to 1.59, more preferably 1.51 to 1.58, even more preferably 1.52 to 1.57, even more preferably 1.525 to 1.56, and particularly preferably 1.53 to 1.555. Here, from the viewpoint of matching the refractive index with that of a silicon semiconductor and reducing loss due to bonding, the refractive index of the cladding region A (21) is preferably 1.50 or more, more preferably 1.51 or more, even more preferably 1.52 or more, even more preferably 1.525 or more, and particularly preferably 1.53 or more. In addition, SiO ２ From the viewpoint of receiving light from an optical fiber such as a 589 nm wavelength, the refractive index is preferably 1.59 or less, more preferably 1.58 or less, even more preferably 1.57 or less, even more preferably 1.56 or less, and particularly preferably 1.555 or less. Note that the refractive index in this specification refers to the refractive index of light with a wavelength of 589 nm.

[0051] Core Region The core region (31) of the cladding layer A (11) in this embodiment is a region that serves as an optical waveguide, and is formed by ion-exchanging Na ions in the glass with Ag ions. Therefore, the glass that constitutes the core region (31) contains Na ２ O and Ag ２ O, and more Na than the glass constituting the cladding region A (21). ２ The content of O is low and Ag ２ The core region (31) has a high O content, which makes the refractive index of the core region (31) higher than that of the cladding region A (21). In addition, since ion exchange is performed in a portion of the surface of the cladding layer A (11), the core region (31) is usually located in a region that includes a portion of the surface of the cladding layer A (11).

[0052] However, since the core region (31) in this embodiment is formed by ion exchange, Na in the core region (31) ２ O and Ag ２The O concentration is not constant, and a distribution also occurs in the refractive index. Therefore, the boundary between the core region (31) and the cladding region A (21) is defined as follows. First, in a cross-sectional view of the cladding layer A (11) perpendicular to the path of the optical waveguide, which is the core region (31), the maximum value of the refractive index is defined as Nmax. Also, the refractive index of the aforementioned cladding region A (21) is defined as N. The difference (Nmax - N) between the maximum refractive index Nmax and the refractive index N of the cladding region A (21) is defined as Δn, and the region where the refractive index is equal to or greater than the value expressed as {N + (Δn / 2)} is defined as the core region (31). In other words, the region of the cladding layer A (11) outside the core region (31) defined above is the cladding region A (21).

[0053] In this embodiment, the core region (31) is formed on a part of the surface of the cladding layer A (11), and therefore the composition of the glass constituting the core region (31) is Na, which is involved in ion exchange. ２ O and Ag ２ The contents of the components other than O are the same, and the preferred ranges are also the same.

[0054] Na in the glass constituting the core region (31) ２ The O content is determined by the Na content in the glass constituting the cladding region A (21). ２ The specific Na content of the core region (31) is as follows: ２ The O content is the same as that of Na in the cladding region A (21). ２ Although it cannot be generally defined because it varies depending on the O content, for example, it is preferably 0 to 20%, more preferably 1 to 17.5%, even more preferably 2 to 15%, even more preferably 3 to 12.5%, and particularly preferably 4 to 10%. ２ The O content is preferably 0% or more, more preferably 1% or more, even more preferably 2% or more, even more preferably 3% or more, and particularly preferably 4% or more. On the other hand, from the viewpoint of preventing the difference in refractive index between the core region (31) and the cladding region A (21) from becoming too large and preventing single-mode light from propagating, Na ２The O content is preferably 20% or less, more preferably 17.5% or less, even more preferably 15% or less, even more preferably 12.5% ​​or less, and particularly preferably 10% or less.

[0055] The glass constituting the core region (31) and the glass constituting the cladding region A (21) are ２ The difference in the O content is related to the amount of ion exchange between Na ions and Ag ions, and is, for example, preferably 1 to 15%, more preferably 1.5 to 14%, even more preferably 2 to 13%, even more preferably 2.5 to 12%, and particularly preferably 3 to 11%. ２ The difference in the O content is preferably 1% or more, more preferably 1.5% or more, even more preferably 2% or more, even more preferably 2.5% or more, and particularly preferably 3% or more, from the viewpoint of increasing the refractive index of the core region (31) by ion exchange with Ag ions and making it more suitable for handling single-mode propagated light as an optical waveguide even when the thickness of the core region (31) is small. On the other hand, from the viewpoint of preventing the core diameter required for single-mode light propagation from becoming extremely narrow due to an excessively large difference in refractive index between the core region (31) and the cladding region A (21), the difference in the Na content is ２ The difference in the O content is preferably 15% or less, more preferably 14% or less, even more preferably 13% or less, even more preferably 12% or less, and particularly preferably 11% or less.

[0056] Ag in the glass constituting the core region (31) ２ The content of O is, for example, preferably 0.01% or more, more preferably 0.01 to 10%, even more preferably 0.5 to 8%, even more preferably 1 to 6%, and particularly preferably 1.5 to 5%. ２ The O content is preferably 0.01% or more, more preferably 0.5% or more, even more preferably 1% or more, and even more preferably 1.5% or more. On the other hand, if the difference in refractive index between the core region (31) and the cladding region A (21) becomes too large, it becomes necessary to reduce the core diameter. ２ The O content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, and particularly preferably 5% or less.

[0057] The refractive index of the core region (31) is not particularly limited as long as it is higher than the refractive index of the cladding region A (21). However, as described above, since the core region (31) in this embodiment is formed by ion exchange, the Ag ２ The concentration of O is not constant, and a distribution also occurs in the refractive index. Therefore, in this embodiment, the maximum refractive index Nmax is used as an index of the refractive index in the core region (31). In consideration of the refractive index of the matrix composition of glass normally used for optical waveguides, the maximum refractive index Nmax is, for example, preferably 1.50 to 2.0, more preferably 1.51 to 1.9, even more preferably 1.52 to 1.8, even more preferably 1.525 to 1.7, and particularly preferably 1.53 to 1.6. Here, from the viewpoint of reducing loss due to bonding with a silicon semiconductor, Nmax is preferably 1.50 or more, more preferably 1.51 or more, even more preferably 1.52 or more, even more preferably 1.525 or more, and particularly preferably 1.53 or more. In addition, SiO ２ From the viewpoint of reducing loss due to splicing with an optical fiber made of the above, Nmax is preferably 2.0 or less, more preferably 1.9 or less, even more preferably 1.8 or less, even more preferably 1.7 or less, and particularly preferably 1.6 or less.

[0058] The difference Δn between the maximum refractive index Nmax in the core region (31) and the refractive index N in the cladding region A (21) is, for example, preferably 0.003 to 0.06, more preferably 0.005 to 0.05, more preferably 0.005 to 0.04, and may be 0.007 to 0.03, 0.01 to 0.02, or 0.012 to 0.018. From the viewpoint of controlling the bending of incident light, Δn is preferably 0.003 or more, more preferably 0.005 or more, and may be 0.007 or more, 0.01 or more, or 0.012 or more. There is no particular upper limit to Δn, but the refractive index difference that can be generated by ion exchange is usually 0.06 or less, preferably 0.05 or less, and may be 0.04 or less, 0.03 or less, 0.02 or less, or 0.018 or less.

[0059] The maximum propagation loss of light in the core region (31) at a wavelength of 1200 to 1600 nm is preferably 3.0 dB / cm or less, more preferably 2.0 dB / cm or less, even more preferably 1.0 dB / cm or less, even more preferably 0.5 dB / cm or less, and particularly preferably 0.2 dB / cm or less. The lower limit of the propagation loss of light is not particularly limited, as the smaller the better, but it is usually 0.001 dB / cm or more.

[0060] The thickness of the core region (31) in the thickness direction of the cladding layer A (11) is preferably 1.8 to 10 μm, more preferably 2 to 9 μm, and may be 3 to 8 μm, 4 to 7 μm, 4.25 to 6 μm, or 4.5 to 5.5 μm. The thickness may also be 3 to 8 μm, 3 to 7 μm, 3 to 6 μm, or 3 to 5.5 μm. Here, the smaller the thickness of the core region (31), the greater the difference in refractive index between the core region (31) and the cladding region A (21). However, this results in a change in the mode field diameter due to a slight change in the refractive index, making it difficult to strictly control the core thickness. Furthermore, if the optical waveguide has a curved region, it becomes difficult to confine light. From the above viewpoint, the thickness is preferably 1.8 μm or more, more preferably 2 μm or more, and may be 3 μm or more, 4 μm or more, 4.25 μm or more, or 4.5 μm or more. Furthermore, if the path of the optical waveguide has a curved region, in order to suppress bending loss, the thickness is preferably 10 μm or less, more preferably 9 μm or less, and may be 8 μm or less, 7 μm or less, 6 μm or less, or 5.5 μm or less.

[0061] The core region (31) may have a fan shape including a semicircle in a cross section perpendicular to the path of the optical waveguide, preferably a semicircle. The fan shape is formed by two radii and an arc between them, and the arc is preferably located vertically downward in the cross section. When the core region (31) has a fan shape in the cross section, the Ag concentration is high in the region close to the intersection of the two radii and decreases with increasing distance from the intersection.

[0062] Clad Layer A (11) The clad layer A (11) in this embodiment is made of glass having the clad region A (21) and the core region (31).

[0063] The thickness of the cladding layer A (11) varies depending on the thickness of the cladding layer B (12) and the device to be mounted, but is preferably 100 to 3000 μm, more preferably 200 to 2000 μm, and even more preferably 400 to 1000 μm. From the viewpoint of rigidity, the thickness is preferably 100 μm or more, more preferably 200 μm or more, and even more preferably 400 μm or more. Furthermore, from the viewpoint of reducing the height of the electronic component, the thickness is preferably 3000 μm or less, more preferably 2000 μm or less, and even more preferably 1000 μm or less.

[0064] <Cladding Layer B> In this embodiment, the cladding layer B (12) is bonded to the cladding layer A (11) and has a cladding region B (22). The refractive index of the cladding region B (22) is lower than the refractive index of the core region (31) in the cladding layer A (11).

[0065] The cladding layer B (12) may be composed of a glass layer or a resin layer (32), or may be composed of a glass layer or a resin layer (32) and an adhesive layer (33). When the cladding layer B (12) is composed of a glass layer or a resin layer (32), the cladding region B (22) is composed of a glass layer or a resin layer (32). When the cladding layer B (12) is composed of a glass layer or a resin layer (32) and an adhesive layer (33), if the thickness of the adhesive layer (33) is less than 5 μm, the cladding region B (22) is composed of the glass layer or the resin layer (32) and the adhesive layer (33). Furthermore, if the thickness of the adhesive layer is 5 μm or more, the cladding region B (22) is composed of the adhesive layer (33).

[0066] Cladding Region B In one embodiment of the cladding region B (22') in this embodiment, as shown in Figure 2, it is composed of a glass layer or a resin layer (32'), and the cladding layer A (11') and the glass layer or the resin layer (32') are directly bonded to each other. As a result, the glass layer or the resin layer (32') covers the periphery of the core region (31') together with the cladding region A (21'), thereby forming an optical waveguide. Therefore, the refractive index of the glass layer or the resin layer (32') in this case is lower than the refractive index of the core region (31').

[0067] When the cladding layer B (12') is composed of a cladding region B (22') made of a glass layer or a resin layer (32'), the difference Δn' between the refractive index N' of the glass layer or resin layer (32') and the maximum refractive index Nmax of the core region (31') is, for example, preferably 0.003 to 0.06, more preferably 0.005 to 0.05, more preferably 0.005 to 0.04, and may be 0.007 to 0.03, 0.01 to 0.02, or 0.012 to 0.018. Here, from the viewpoint of controlling the bending or the like of the incident light, Δn' is preferably 0.003 or more, more preferably 0.005 or more, and may be 0.007 or more, 0.01 or more, or 0.012 or more. There is no particular upper limit to Δn′, but the refractive index difference that can be produced by ion exchange is usually 0.06 or less, preferably 0.05 or less, and may be 0.04 or less, 0.03 or less, 0.02 or less, or 0.018 or less.

[0068] Another aspect of the cladding region B (22'') in this embodiment is composed of an adhesive layer (33'') having a thickness of less than 5 μm and a glass layer or resin layer (32''), as shown in Figure 3. The cladding layer A (11'') and the cladding layer B (12'') are bonded via the adhesive layer (33'').

[0069] When the cladding layer B (12") is composed of a cladding region B (22") that includes an adhesive layer (33") and a glass or resin layer (32"), the difference Δn" between the refractive index N" of the adhesive layer (33") and the maximum refractive index Nmax of the core region (31") is, for example, preferably 0.003 to 0.06, more preferably 0.005 to 0.05, and more preferably 0.005 to 0.04, and may be 0.007 to 0.03, 0.01 to 0.02, or 0.012 to 0.018. From the viewpoint of controlling the bending or the like of the incident light, Δn" is preferably 0.003 or more, more preferably 0.005 or more, and may be 0.007 or more, 0.01 or more, or 0.012 or more. There is no particular upper limit to Δn″, but the refractive index difference that can be produced by ion exchange is usually 0.06 or less, preferably 0.05 or less, and may be 0.04 or less, 0.03 or less, 0.02 or less, or 0.018 or less.

[0070] The difference Δn′″ between the refractive index N′″ of the glass layer or resin layer (32″) constituting the cladding region B (22″) and the maximum refractive index Nmax of the core region (31″) is, for example, preferably 0.003 to 0.06, more preferably 0.005 to 0.05, and more preferably 0.005 to 0.04, and may be 0.007 to 0.03, 0.01 to 0.02, or 0.012 to 0.018. From the viewpoint of controlling the bending or the like of the incident light, Δn′″ is preferably 0.003 or more, more preferably 0.005 or more, and may be 0.007 or more, 0.01 or more, or 0.012 or more. There is no particular upper limit to Δn′″, but the refractive index difference that can be produced by ion exchange is usually 0.06 or less, preferably 0.05 or less, and may be 0.04 or less, 0.03 or less, 0.02 or less, or 0.018 or less.

[0071] Another aspect of the cladding region B (22''') in this embodiment is when the thickness of the adhesive layer (33''') is 5 μm or more, and as shown in FIG. 4, the cladding region B (22''') is composed of the adhesive layer (33'''). The cladding layer A (11''') and the cladding layer B (12''') are bonded via the adhesive layer (33''').

[0072] When the cladding layer B (12'") is composed of a cladding region B (22'") that is made up of an adhesive layer (33'"), the difference Δn"" between the refractive index N"" of the adhesive layer (33'") and the maximum refractive index Nmax of the core region (31'") is, for example, preferably 0.003 to 0.06, more preferably 0.005 to 0.05, still more preferably 0.005 to 0.04, and may be 0.007 to 0.03, 0.01 to 0.02, or 0.012 to 0.018. From the viewpoint of controlling the bending or the like of the incident light, Δn"" is preferably 0.003 or more, more preferably 0.005 or more, and may be 0.007 or more, 0.01 or more, or 0.012 or more. Furthermore, there is no particular upper limit to Δn″″, but the refractive index difference that can be produced by ion exchange is usually 0.06 or less, preferably 0.05 or less, and may be 0.04 or less, 0.03 or less, 0.02 or less, or 0.018 or less.

[0073] In this case, the glass layer or resin layer (32''') of the cladding layer B (12''') does not contribute to the construction of the optical waveguide, so the refractive index is arbitrary and can be selected according to the desired characteristics.

[0074] In this embodiment, the dielectric loss tangent at 10 GHz of the material constituting the cladding region B (22) is preferably 0.01 or less, more preferably 0.005 or less, and even more preferably 0.003 or less, from the viewpoint that the optical waveguide substrate serves as a circuit for transmitting not only light but also electrical signals. The smaller the dielectric loss tangent, the more preferable it is, but it is usually 0.0001 or more. Here, when the cladding region B (22) is composed of an adhesive layer (33") and a glass or resin layer (32"), it is preferable that the dielectric loss tangents of both the adhesive layer (33") and the glass or resin layer (32") are within the above range. Furthermore, when the cladding region B (22) is composed only of an adhesive layer (33"'), it is preferable that the dielectric loss tangent of the adhesive layer (33"') is within the above range. On the other hand, from the viewpoint that the optical waveguide substrate also serves as a circuit, it is also preferable that the dielectric loss tangent of the glass or resin layer (32"') is within the above range.

[0075] In this embodiment, the thermal expansion coefficient of the material constituting the cladding region B (22) is 5×10 －７ ~120 x 10 －７ / K is preferred, and 10×10 －７ ~120 x 10 －７ / K is more preferable, and 20×10 －７ ~80 x 10 －７ / K is more preferable, and 30×10 －７ ~60 x 10 －７ From the viewpoint of suppressing thermal warping when connected to silicon, the thermal expansion coefficient is more preferably 5×10 －７ / K or more is preferable, and 10 × 10 －７ / K or more is more preferable, and 20×10 －７ / K or more is more preferable, and 30×10 －７ From the same viewpoint, the thermal expansion coefficient is more preferably 120×10 －７ / K or less is preferable, and 80 × 10－７ / K or less is more preferable, and 60×10 －７ / K or less is more preferable. In this specification, the thermal expansion coefficient means the average thermal expansion coefficient at 50 to 350°C.

[0076] Here, when the cladding region B (22) is composed of only the adhesive layer (33'''), it is preferable that the thermal expansion coefficient of the adhesive layer (33''') is within the above range. Also, when the cladding region B (22) is composed of the adhesive layer (33'') and the glass layer or resin layer (32''), it is preferable that the thermal expansion coefficients of both the adhesive layer (33'') and the glass layer or resin layer (32'') are within the above range.

[0077] In this embodiment, cladding region B (22) is bonded to cladding region A (21). When cladding region B (22) is composed of a glass layer, the composition of the glass constituting this glass layer may be the same as or different from the composition of the glass constituting cladding region A (21). In other words, this embodiment excludes a configuration in which cladding region A (21) and cladding region B (22) are composed of glass of the same composition, in which a region of a certain depth in a single glass plate is ion-exchanged, and a portion of the periphery of the core region formed by ion exchange is made into cladding layer A (11), and the other portion of the periphery is made into cladding layer B (12). On the other hand, the optical waveguide substrate according to this embodiment also includes a configuration in which a cladding layer A (11) is prepared, a cladding layer B (12) made of glass of the same composition as the glass constituting cladding region A (21) of cladding layer A (11), and the cladding layers are bonded together. The fact that cladding layer A (11) and cladding layer B (12) are bonded in this manner means that there is a bonding surface at the boundary between the two layers. The presence of a bonding surface can be confirmed, for example, by microscopic observation or composition analysis. However, in the optical waveguide substrate according to this embodiment, it is not essential to use glass with good ion exchange properties for cladding layer B (12). Considering that cladding layer B (12) can be preferably formed from glass or resin having desired properties, it is preferable that the composition of the glass forming the glass layer of cladding region B (22) be different from the composition of the glass forming cladding region A (21). It is also preferable that cladding region B (22) be formed from a resin layer.

[0078] Adhesive Layer The thickness of the adhesive layer (33) in this embodiment determines whether the glass layer or resin layer (32) in the cladding layer B (12) constitutes the cladding region B (22).

[0079] When the thickness of the adhesive layer (33) is less than 5 μm, the thickness of the adhesive layer (33'') is preferably 0.1 μm or more and less than 5 μm, more preferably 0.5 to 3 μm, even more preferably 0.8 to 2 μm, and even more preferably 1 to 2 μm. Here, from the viewpoint of adhesion between the cladding layer A (11'') and the cladding layer B (12''), the thickness is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 0.8 μm or more, and even more preferably 1 μm or more. Furthermore, from the viewpoint of hardly affecting the propagation state of light, the thickness is less than 5 μm, preferably 3 μm or less, and more preferably 2 μm or less.

[0080] In this case, from the viewpoint of confining light in the core region (31'') of the cladding layer A (11''), the refractive index difference between the adhesive layer (33'') and the glass constituting the cladding region A (21'') is preferably smaller than the refractive index difference between the core region (31'') and the cladding region A (21''). The refractive index difference between the adhesive layer (33'') and the glass constituting the cladding region A (21'') of the cladding layer A (11'') is preferably 0.1 or less. Here, the refractive index difference is preferably 0.1 or less, more preferably 0.02 or less, and even more preferably 0.01 or less. The lower limit of the refractive index difference is not particularly limited, and may be 0, i.e., the refractive index of the adhesive layer (33'') and the glass constituting the cladding region A (21'') may be the same. Furthermore, the refractive index difference may be, for example, 0.0005 or more.

[0081] The refractive index of the adhesive layer (33'') or the refractive index of the cladding region A (21'') may be either higher.

[0082] When the thickness of the adhesive layer (33) is 5 μm or more, the thickness of the adhesive layer (33''') is preferably 5 to 100 μm, more preferably 8 to 80 μm, and even more preferably 10 to 60 μm. Here, from the viewpoint of the adhesive layer (33''') suitably constituting an optical waveguide as the cladding region B (22''') together with the cladding region A (21''') and the core region (31'''), the thickness is 5 μm or more, preferably 8 μm or more, and more preferably 10 μm or more. Furthermore, from the viewpoint of heat resistance, the thickness is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 60 μm or less.

[0083] In this case, the refractive index difference between the adhesive layer (33''') and the glass constituting the cladding region A (21''') of the cladding layer A (11''') is preferably 0 to 0.003, more preferably 0 to 0.002, and even more preferably 0.0001 to 0.001. From the viewpoint of confining light in the core region (31''') of the cladding layer A (11'''), the refractive index difference is preferably 0.003 or less, more preferably 0.002 or less, and even more preferably 0.001 or less. The lower limit of the refractive index difference is not particularly limited, and may be 0, i.e., the refractive index of the adhesive layer (33''') and the glass constituting the cladding region A (21''') may be the same. The refractive index difference may also be, for example, 0.0001 or more.

[0084] The refractive index of the adhesive layer (33''') and the refractive index of the cladding region A (21''') may be either higher.

[0085] The adhesive layer (33) is not particularly limited as long as it can bond the cladding layer A (11) and the cladding layer B (12) and has the desired physical properties described above. Examples of materials that can be used to form the adhesive layer (33) include at least one resin or curing agent selected from the group consisting of acrylic resin, epoxy resin, urethane resin, silicone resin, enethiol resin, polyimide resin, fluororesin, photocuring agent, and thermosetting agent. Among these, from the viewpoint of heat resistance, acrylic resin, fluororesin, silicone resin, polyimide resin, or a resin composition containing these resins as the main component and further containing a photocuring agent or thermosetting agent is preferred. Here, the term "main component" in a resin composition refers to the component that is contained in the largest amount among the components that constitute the resin composition.

[0086] Glass Layer or Resin Layer Whether the glass layer or resin layer (32) in this embodiment constitutes the cladding region B (22) in the cladding layer B (12) is determined by the presence or absence of the adhesive layer (33) and its thickness.

[0087] When the adhesive layer (33) is not present, the glass layer or resin layer (32') becomes the cladding region B (22') that constitutes the cladding layer B (12') as shown in FIG. 2. When the thickness of the adhesive layer (33) is less than 5 μm, the glass layer or resin layer (32'') becomes the cladding region B (22') that constitutes the cladding layer B (12') together with the adhesive layer (33'') as shown in FIG. 3. When the thickness of the adhesive layer (33) is 5 μm or more, the adhesive layer (33''') constitutes the cladding region B (22''') as shown in FIG. 4, and therefore any glass layer or resin layer (32''') can be used.

[0088] Glass Layer When the glass layer or resin layer (32) constituting the cladding layer B (12) is a glass layer and such glass layer does not constitute the cladding region B (22), i.e., when the thickness of the adhesive layer (33) is 5 μm or more, any glass can be used to constitute the glass layer.

[0089] That is, it is preferable to use glass having a small dielectric loss tangent as the glass.－７ ~120 x 10 －７ It is also preferable to use glass having a refractive index of 1 / K.

[0090] Furthermore, the glass constituting the cladding region A (21) contains Na to form the core region (31) by ion exchange with Ag ions. ２ The glass of the glass layer constituting the clad layer B (12) needs to contain 5% or more of O. ２ Therefore, from the viewpoint of reducing the dielectric loss tangent, the glass in the glass layer contains more Na than the glass constituting the cladding region A (21) of the cladding layer A (11). ２ The O content is preferably low.

[0091] Examples of the glass in the glass layer that does not constitute the cladding region B (22) include borosilicate glass and silica glass.

[0092] For example, the above glass contains, in mole percentage on an oxide basis, SiO ２ 57-70%, and B ２ O ３ It is preferable that the content of SiO is 15 to 24%. ２ 57 to 70%, and Al ２ O ３ It is also preferable to satisfy the range of 5 to 15%.

[0093] More specifically, in this embodiment, the glass that does not constitute the cladding region B (22) preferably satisfies the following composition range in mole percent based on oxides: SiO ２ 57-70%, Al ２ O ３ 5-15%, B ２ O ３ 15-24%, MgO 0.1-10%, CaO 0.1-10%, SrO 0.1-10%, BaO 0-10%, and ZnO 0-0.1%.

[0094] The components of the glass that does not constitute the cladding region B (22) in this embodiment are described below. Note that "%" indicates mole percentage based on oxide.

[0095] SiO ２ is a network forming material. ２ The content is preferably 57 to 70%, more preferably 58 to 68%, even more preferably 60 to 66%, and even more preferably 61 to 65%. From the viewpoint of improving glass-forming ability and weather resistance and suppressing devitrification, the content is preferably 57% or more, more preferably 58% or more, even more preferably 60% or more, and even more preferably 61% or more. From the viewpoint of solubility, the content is preferably 70% or less, more preferably 68% or less, even more preferably 66% or less, even more preferably 65% ​​or less, particularly preferably 64% or less, and particularly preferably 63% or less.

[0096] Al ２ O ３ is a component that is effective in improving weather resistance, improving Young's modulus, suppressing phase separation of glass, and lowering the thermal expansion coefficient. ２ O ３ The content of Al is preferably 5 to 15%, more preferably 6 to 14%, even more preferably 7 to 13%, and even more preferably 8 to 12%. ２ O ３ From the viewpoint of fully obtaining the effect of containing, the content is preferably 5% or more, more preferably 6% or more, even more preferably 7% or more, and even more preferably 8% or more. From the viewpoint of solubility, etc., the content is preferably 15% or less, more preferably 14% or less, even more preferably 13% or less, and even more preferably 12% or less.

[0097] B ２ O ３ is a component that improves solubility. ２ O ３The content is preferably 15 to 24%, more preferably 16 to 23%, even more preferably 17 to 22%, and even more preferably 17.5 to 21%. Here, from the viewpoint of solubility and reducing the dielectric loss tangent in the high frequency range, the content is preferably 15% or more, more preferably 16% or more, even more preferably 17% or more, and even more preferably 17.5% or more. Furthermore, from the viewpoint of chemical resistance, the content is preferably 24% or less, more preferably 23% or less, even more preferably 22% or less, even more preferably 21% or less, particularly preferably 20% or less, particularly preferably 19% or less, and most preferably 18% or less.

[0098] MgO is a component that increases Young's modulus without increasing specific gravity. In other words, MgO is a component that increases the specific elastic modulus, thereby reducing the problem of deflection and improving fracture toughness and glass strength. MgO also improves solubility. The MgO content is preferably 0.1 to 10%, more preferably 0.2 to 9%, even more preferably 1 to 8%, and even more preferably 2 to 7%. Here, from the viewpoint of optimally obtaining the effect of containing MgO and suppressing an excessively low thermal expansion coefficient, the content is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 1% or more, and even more preferably 2% or more. Furthermore, from the viewpoint of suppressing an increase in the devitrification temperature, the content is preferably 10% or less, more preferably 9% or less, even more preferably 8% or less, even more preferably 7% or less, especially preferably 6% or less, even more preferably 5% or less, particularly preferably 4% or less, and most preferably 3% or less.

[0099] Among alkaline earth metals, CaO is the second most effective component after MgO in increasing the specific modulus of elasticity without excessively lowering the strain point, and like MgO, it also improves solubility. Furthermore, compared to MgO, CaO is less likely to increase the devitrification temperature. The CaO content is preferably 0.1 to 10%, more preferably 0.2 to 8%, even more preferably 0.5 to 7%, even more preferably 1 to 6%, and particularly preferably 2 to 5%. From the viewpoint of fully obtaining the effects of including CaO, the content is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, even more preferably 1% or more, and particularly preferably 2% or more. Furthermore, from the viewpoint of preventing the average thermal expansion coefficient from becoming too high and suppressing an increase in the devitrification temperature to prevent devitrification during glass production, the content is preferably 10% or less, more preferably 8% or less, even more preferably 7% or less, still more preferably 6% or less, particularly preferably 5% or less, even more preferably 4% or less, and particularly preferably 3% or less.

[0100] SrO is a component that improves the meltability of glass without increasing the devitrification temperature. The SrO content is preferably 0.1 to 10%, more preferably 0.2 to 9%, even more preferably 0.5 to 8%, even more preferably 1 to 7%, and particularly preferably 2 to 6%. From the viewpoint of fully obtaining the effects of containing SrO, the content is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, even more preferably 1% or more, and particularly preferably 2% or more. Furthermore, from the viewpoint of preventing the specific gravity from becoming too high and suppressing the average thermal expansion coefficient from becoming too high, the content is preferably 10% or less, more preferably 9% or less, even more preferably 8% or less, even more preferably 7% or less, particularly preferably 6% or less, even more preferably 5% or less, even more preferably 4% or less, particularly preferably 3% or less, and most preferably 2.5% or less.

[0101] BaO is a component that improves the meltability without increasing the devitrification temperature of the glass. The BaO content is preferably 0 to 10%, more preferably 0.1 to 8%, even more preferably 0.2 to 5%, even more preferably 1 to 5%, and particularly preferably 2 to 3%. When BaO is contained, from the viewpoint of fully obtaining the effects of BaO, the content is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 1% or more, and particularly preferably 2% or more. Furthermore, from the viewpoints of preventing the specific gravity from becoming too high and of Young's modulus, relative dielectric constant, average thermal expansion coefficient, etc., the content is preferably 10% or less, more preferably 8% or less, even more preferably 5% or less, and even more preferably 3% or less.

[0102] ZnO is a component that improves chemical resistance, but also makes phase separation more likely and increases the devitrification temperature. The ZnO content is preferably 0 to 0.1%. Here, the content is preferably 0.1% or less, more preferably 0.05% or less, even more preferably 0.03% or less, even more preferably 0.01% or less, and it is particularly preferable that the ZnO content is substantially zero. Note that "substantially zero ZnO content" means, for example, less than 0.01%.

[0103] In addition to the above, other components may be included in accordance with the desired properties of the glass that does not constitute the cladding region B (22). ２ O, Na ２ O.K. ２ Alkali metal oxides such as O and Se ２ O ３ , CdO, BeO, Sc ２ O ３ , TiO ２ , ZnO ２ , Ga ２ O ３ , GeO ２ , Y ２ O ３ , ZrO ２ , Nb ２ O ５ , In ２ O ３ , TeO ２ , HfO ２ , Ta ２ O ５ , W.O.３ , Bi ２ O ３ , La ２ O ３ , Gd ２ O ３ , Yb ２ O ３ , Lu ２ O ３ , SnO ２ , Cl, SO ３ etc.

[0104] When the glass layer or resin layer (32) constituting the cladding layer B (12) is a glass layer and this glass layer constitutes the cladding region B (22), i.e., when the thickness of the adhesive layer (33) is less than 5 μm, the refractive index of the glass constituting the glass layer is lower than the refractive index of the core region (31) of the cladding layer A (11). As a result, the cladding region B (22) including the glass layer can form an optical waveguide together with the core region (31) and the cladding region A (21).

[0105] As described above, the glass of the glass layer constituting the cladding region B (22) may have any composition as long as its refractive index is lower than that of the core region (31). Examples of the glass include aluminoborosilicate glass and silica glass. The specific composition may be the same as that used in the cladding region A (21) of the cladding layer A (11). Furthermore, the glass may have the same composition as that used in the case where the glass layer does not constitute the cladding region B (22), as long as the refractive index is low.

[0106] Resin layer When the glass layer or resin layer (32) constituting the clad layer B (12) is a resin layer and such a resin layer does not constitute the clad region B (22), i.e., when the thickness of the adhesive layer (33) is 5 μm or more, any resin can be used to constitute the resin layer.

[0107] That is, it is preferable to use a resin having a small dielectric loss tangent, for example, as the resin. －７ ~150 x 10 －７ It is also preferable to use a resin of 1 / K.

[0108] Such a resin layer that does not constitute the cladding region B (22) may contain at least one resin or curing agent selected from the group consisting of, for example, acrylic resin, epoxy resin, urethane resin, silicone resin, enethiol resin, polyimide resin, fluororesin, photocuring agent, and thermosetting agent.

[0109] More specifically, from the viewpoint of heat resistance, the resin layer preferably contains an acrylic resin, a fluororesin, a silicone resin, a polyimide resin, or a resin composition containing these resins as a main component and further containing a photocuring agent or a thermal curing agent. Here, the main component in the resin composition means the component that is contained in the largest amount among the components constituting the resin composition.

[0110] When the glass layer or resin layer (32) constituting the cladding layer B (12) is a resin layer and this resin layer constitutes the cladding region B (22), i.e., when the thickness of the adhesive layer (33) is less than 5 μm, the refractive index of the resin constituting the resin layer is lower than the refractive index of the core region (31) of the cladding layer A (11). As a result, the cladding region B (22) including the resin layer can form an optical waveguide together with the core region (31) and the cladding region A (21).

[0111] As described above, the resin of the resin layer constituting the cladding region B (22) need only have a refractive index lower than that of the core region (31), and the specific composition is not particularly limited. For example, the resin layer may contain at least one resin or curing agent selected from the group consisting of acrylic resin, epoxy resin, urethane resin, silicone resin, enethiol resin, polyimide resin, fluororesin, photocuring agent, and thermosetting agent. More specifically, from the viewpoint of heat resistance, acrylic resin, fluororesin, silicone resin, polyimide resin, or a resin composition containing these resins as the main component and further containing a photocuring agent or thermosetting agent is preferred. Here, the term "main component" in a resin composition refers to the component with the highest content among the components constituting the resin composition.

[0112] Clad layer B (12) In this embodiment, the clad layer B (12) has the clad region B (22). The thickness of the clad layer B (12) varies depending on the thickness of the clad layer A (11) and the device to be mounted, but is preferably 10 to 3,000 μm, more preferably 20 to 2,000 μm, and even more preferably 30 to 1,000 μm. From the viewpoint of confining light in the core region of the clad layer A, the thickness is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. Furthermore, from the viewpoint of reducing the height of the electronic component, the thickness is preferably 3,000 μm or less, more preferably 2,000 μm or less, and even more preferably 1,000 μm or less.

[0113] When the cladding layer B (12) consists only of the cladding region B (22), the preferred thickness of the cladding region B (22) is the same as the preferred thickness of the cladding layer B (12). On the other hand, when the cladding layer B (12) includes a glass layer or a resin layer (32) in addition to the cladding region B (22), the thickness of the cladding region B (22) is, for example, preferably 100 to 5000 μm, more preferably 200 to 4000 μm, and even more preferably 300 to 3000 μm. Here, from the viewpoint of rigidity, the thickness is preferably 100 μm or more, more preferably 200 μm or more, and even more preferably 300 μm or more. Furthermore, from the viewpoint of reducing the height of the electronic component, the thickness is preferably 5000 μm or less, more preferably 4000 μm or less, and even more preferably 3000 μm or less.

[0114] <Optical Waveguide Substrate> The thickness of the optical waveguide substrate according to this embodiment varies depending on the device to be mounted, but is preferably 0.1 to 4.0 mm (100 to 4000 μm), more preferably 0.15 to 2.0 mm, even more preferably 0.2 to 1.5 mm, even more preferably 0.25 to 1.0 mm, and particularly preferably 0.3 to 0.8 mm. From the viewpoint of ease of handling of the components, the thickness of the optical waveguide substrate is preferably 0.1 mm or more, more preferably 0.15 mm or more, even more preferably 0.2 mm or more, even more preferably 0.25 mm or more, and particularly preferably 0.3 mm or more. On the other hand, from the viewpoint of reducing the height of electronic components, the thickness of the optical waveguide substrate is preferably 4.0 mm or less, more preferably 2.0 mm or less, even more preferably 1.5 mm or less, even more preferably 1.0 mm or less, and particularly preferably 0.8 mm or less.

[0115] The optical waveguide substrate according to this embodiment is preferably used in an optical device, that is, the optical device according to this embodiment preferably includes the optical waveguide substrate and an optical coupler that extracts at least a portion of the light transmitted by the optical waveguide substrate to the outside.

[0116] The optical waveguide substrate according to this embodiment can be mounted, for example, on an optical integrated device. In one aspect of the optical integrated device, an optical waveguide substrate is connected to a semiconductor substrate, and single-mode propagated light is introduced into the semiconductor substrate via a core portion of the optical waveguide substrate. The semiconductor substrate is preferably, for example, a silicon semiconductor substrate. Furthermore, the optical waveguide substrate according to this embodiment can also be mounted on a pluggable device, without being limited to the above.

[0117] The optical waveguide substrate according to this embodiment can be applied not only to the optical transmission line as described above, but also to interposers and the like.

[0118] <Method for Manufacturing Optical Waveguide Substrate> <Method for Manufacturing Cladding Layer A> The method for manufacturing the cladding layer A in this embodiment is not particularly limited, but may include, for example, the following steps: (i) Na ２(ii) contacting a region of the glass plate that will become a core region in an optical waveguide with a molten salt containing Ag ions to exchange Na ions in the glass for Ag ions.

[0119] In step (i), glass may be produced or commercially available glass may be used as is. Conventionally known methods can be used to produce glass. For example, raw materials for the glass components are mixed and heated and melted in a glass melting furnace. The glass is then homogenized by a known method, formed into a desired shape, and slowly cooled to obtain a glass plate.

[0120] In the ion-exchanging step (ii), a partial region on one surface of the glass plate is ion-exchanged to exchange Na ions with Ag ions in the glass, and the refractive index of the ion-exchanged region becomes higher than that of the non-ion-exchanged region, i.e., a core region can be formed by the ion exchange.

[0121] To stably form a core region with a controlled ion exchange depth, it is important that the ion exchange rate from Na ions to Ag ions is not too fast. For example, an ion exchange rate that results in a core region thickness of 2.5 to 10 μm after ion exchange treatment for 20 minutes or more is preferable because it allows the ion exchange depth to be appropriately controlled and maintains the homogeneity of the core region. Furthermore, from the viewpoint of productivity, the time for the ion exchange treatment is preferably 6 hours or less.

[0122] It is preferable to reduce the content of Al component in the glass matrix composition for appropriately performing ion exchange from Na ions to Ag ions within the above-mentioned treatment time, i.e., the glass composition of the cladding region A. Furthermore, while alkaline earth metal components are components that increase the rate of ion exchange from Na ions to Ag ions, containing more than a certain amount of alkaline earth metal component conversely decreases the ion exchange rate.

[0123] In one embodiment of ion exchange, when ion exchange is performed by immersing a glass plate in molten salt, it is preferable to mask the area other than the area to be used as an optical waveguide. The masking material may be any material that does not react with the molten salt and that inhibits ion exchange between the components constituting the glass and the components of the molten salt even when the glass comes into contact with the molten salt. For example, Al ２ O ３ , SiO ２ , SiN, TiO ２ , ITO or the like is used for masking.

[0124] The masking may be adjusted appropriately according to the desired thickness of the core region and the maximum horizontal width in a cross-sectional view perpendicular to the desired optical waveguide path. For example, the width of the gap for forming the core region is preferably 1 to 12 μm, more preferably 2 to 11 μm, and even more preferably 3 to 10 μm. Here, from the viewpoint of enhancing the light confinement effect, the width is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. On the other hand, from the viewpoint of transmitting light in a single mode, the width is preferably 12 μm or less, more preferably 11 μm or less, and even more preferably 10 μm or less.

[0125] The method for bringing the masked glass sheet into contact with the molten salt containing Ag ions is not particularly limited, and examples thereof include immersion of the glass sheet in the molten salt, application of the molten salt, spraying of the molten salt, etc. Among these, immersion in the molten salt is preferred from the viewpoint of enabling treatment at high temperature for a long period of time.

[0126] The molten salt may be any salt containing Ag ions. Examples of salts containing Ag ions include AgNO ３ , Ag ２ SO ４ , Ag ２ CO ３ Among them, AgNO is preferred from the viewpoint of melting temperature. ３ The salt containing Ag ions may be used alone or in combination of two or more.

[0127] To adjust the Ag ion concentration in the molten salt, it is preferable to use a mixed molten salt in which a salt containing Ag ions is mixed with other salts. Examples of the other salts include nitrates, sulfates, carbonates, and chlorides. Among these, examples of nitrates include lithium nitrate, sodium nitrate, potassium nitrate, and cesium nitrate. Examples of sulfates include lithium sulfate, sodium sulfate, potassium sulfate, and cesium sulfate. Examples of carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of chlorides include lithium chloride, sodium chloride, potassium chloride, and cesium chloride. Among these, from the viewpoint of preventing unintentional stress from being applied to the glass, it is preferable to include sodium nitrate, sodium sulfate, sodium carbonate, and sodium chloride, and sodium nitrate and sodium sulfate are more preferable. The above other salts may be used alone or in combination.

[0128] The content ratio of Ag ions relative to the total amount of cations in the molten salt is preferably 0.5 to 20% by mass, more preferably 1.0 to 19%, even more preferably 1.5 to 18%, even more preferably 2.0 to 17%, and particularly preferably 2.5 to 16%. Here, from the viewpoint of achieving a large refractive index difference, the content of Ag ions is preferably 0.5% or more, more preferably 1.0% or more, even more preferably 1.5% or more, even more preferably 2.0% or more, and particularly preferably 2.5% or more. On the other hand, from the viewpoint that an excessively large refractive index makes control of the core diameter too delicate, the content of Ag ions is preferably 20% or less, more preferably 19% or less, even more preferably 18% or less, even more preferably 17% or less, and particularly preferably 16% or less.

[0129] The temperature of the molten salt is not particularly limited as long as it is equal to or higher than the melting point of the salt, but is, for example, preferably 250 to 490°C, more preferably 280 to 450°C, even more preferably 300 to 430°C, even more preferably 325 to 410°C, and particularly preferably 350 to 400°C. From the viewpoint of productivity, the temperature of the molten salt is preferably 250°C or higher, more preferably 280°C or higher, even more preferably 300°C or higher, even more preferably 325°C or higher, and particularly preferably 350°C or higher. On the other hand, from the viewpoint of achieving a desired core region thickness with higher homogeneity, the temperature of the molten salt is preferably 490°C or lower, more preferably 450°C or lower, even more preferably 430°C or lower, even more preferably 410°C or lower, and particularly preferably 400°C or lower.

[0130] The time for contact with the molten salt varies depending on the contact method, but when the glass plate is immersed in the molten salt, the immersion time is preferably 20 minutes to 6 hours, more preferably 30 minutes to 4 hours, even more preferably 35 minutes to 3 hours, even more preferably 40 minutes to 2.5 hours, and particularly preferably 45 minutes to 2 hours. Here, from the viewpoint of achieving a desired core region thickness with higher homogeneity, the immersion time is preferably 20 minutes or more, more preferably 30 minutes or more, even more preferably 35 minutes or more, even more preferably 40 minutes or more, and particularly preferably 45 minutes or more. On the other hand, from the viewpoint of productivity, the immersion time is preferably 6 hours or less, more preferably 4 hours or less, even more preferably 3 hours or less, even more preferably 2.5 hours or less, and particularly preferably 2 hours or less.

[0131] When carrying out the step (ii), the glass sheet may be preheated. The preheating temperature varies depending on the temperature of the molten salt, but is preferably 100° C. or higher, for example.

[0132] Furthermore, step (ii) may be followed by a washing step or a drying step. In the washing step, the glass is washed using industrial water, ion-exchanged water, or the like. The industrial water used may be treated as necessary. Among these, ion-exchanged water is preferred. Washing conditions vary depending on the cleaning solution used, but when ion-exchanged water is used, washing is preferably carried out at 0 to 100°C from the viewpoint of completely removing the adhering salt. In the washing step, various methods can be used, such as immersing the glass plate in a water tank containing ion-exchanged water, exposing the surface of the glass plate to running water, or spraying the cleaning solution onto the surface of the glass plate with a shower.

[0133] <Method for Manufacturing Clad Layer B> The method for manufacturing the clad layer B in this embodiment is not particularly limited, and an appropriate manufacturing method may be selected depending on the form of the clad layer B.

[0134] In the case of Figure 2, when the cladding layer B (12') is made of a glass layer and the cladding layer A (11') and the glass layer are directly bonded, for example, a glass layer is prepared in advance, and the cladding layer A (11') and the glass layer are bonded by thermal compression bonding or by activating the surface by plasma treatment.

[0135] 2, when the cladding layer B (12') is made of a resin layer and the cladding layer A (11') and the resin layer are directly bonded to each other, a bonding method can be used in which, for example, a thermosetting resin or a photocurable resin is selected as the resin layer, a precursor of the resin layer is prepared before curing, the precursor is placed on the cladding layer A (11'), and the precursor is cured by heating or light irradiation to form a resin layer. When the resin layer is a thermoplastic resin, a resin layer may be prepared in advance, and the resin layer may be bonded to the cladding layer A (11') by thermocompression bonding using heat.

[0136] As shown in Figure 3, when the cladding layer B (12'') is composed of a glass layer or a resin layer (32'') and an adhesive layer (33''), the cladding layer A (11'') and the cladding layer B (12'') are bonded via the adhesive layer (33''). In this case, the adhesive layer (33'') may be applied to the surface of the cladding layer A (11'') and the glass layer or the resin layer (32'') may be placed thereon for bonding, or the adhesive layer (33'') may be bonded to the glass layer or the resin layer (32'') in advance, and then the cladding layer A (11'') may be bonded to the adhesive layer (33'').

[0137] The method for joining the cladding layer A (11''') and the cladding layer B (12''') in the embodiment shown in FIG. 4 can be the same as the joining method in the embodiment shown in FIG.

[0138] The glass layer or resin layer (32) and adhesive layer (33) constituting the cladding layer B (12) can be formed by a conventionally known method.

[0139] The present invention will be described below based on specific examples, but the present invention is not limited to the following examples.

[0140] <<Cladding Layers: G1 to G18, G'1 to G'21>> Glass raw materials were weighed and mixed to achieve the composition shown in Tables 1 to 4, expressed in mole percentage based on oxides, and a glass weight of 400 g. The mixed raw materials were placed in a platinum crucible and melted in an electric furnace at 1500 to 1700°C for approximately 3 hours, followed by degassing and homogenization. Note that components marked with "-" in the tables indicate that they were not intentionally added.

[0141] The molten glass obtained above was poured into a metal mold and held at a temperature approximately 10°C higher than the glass transition point for 1 hour. It was then cooled to room temperature at a rate of 0.5°C / min to obtain a glass block. The obtained glass block was cut and ground, and finally, both surfaces were mirror-polished to obtain glass plates G1 to G18 and G'1 to G'21, each measuring 20 mm x 20 mm x 0.7 mm. The glass plates G1 to G18 may be used as clad layer B or as clad layer A as they are. When used as clad layer A, a core region is formed by subsequent ion exchange treatment. The glass plates G'1 to G'21 are used as clad layer B as they are.

[0142] <<Core Regions of Clad Layer A: A1 to A42>> The glass plates G1 to G18 obtained above and listed in Table 1 or Table 2 were subjected to ion exchange treatment under the conditions listed in Tables 5 to 7 to prepare A1 to A42, which would become the core regions of the clad layer A. The ion exchange treatment was carried out using AgNO as the Ag-containing salt. ３ and NaNO ３ The mixed molten salts of the above were used. The ratios (mass%) of Ag and Na in the mixed molten salts were as shown in "Ag-containing salt" in Tables 5 to 7. A glass plate preheated to 200°C was immersed in each Ag-containing molten salt. The temperature and immersion time of the molten salt were as shown in "Temperature 1 (°C)" and "Retention time 1 (hours)" in Tables 5 to 7. For A30 to A42, after the above ion exchange treatment, NaNO ３ The glass was immersed in molten salt to perform ion exchange again with Ag and Na. The temperature of the molten salt and the immersion time were as shown in "Temperature 2 (°C)" and "Retention time 2 (hours)" in Table 7.

[0143] The ion distribution in the core region of the cladding layer A after the ion exchange treatment obtained above was measured by an electron beam microanalyzer method from the surface of the glass plate to a depth of 100 μm. The amount of Ag and the amount of Na at the point where the amount of Ag ions in the glass was the maximum were respectively the amounts of Ag and Na in the glass forming the core region of the optical waveguide. ２ O content, Na ２These can be regarded as the O content, and are shown as "[Ag] (core region) (mol %)" and "[Na] (core region) (mol %)" in Tables 5 to 7. Note that other elements such as Si are not shown because there was no change in composition from the glass before the ion exchange treatment, i.e., from any of the glasses G1 to G18 that constitute the cladding region A.

[0144] In addition, since ion exchange was performed on the glass plates G1 to G18 without masking, all of the core regions in A1 to A42 were not completely surrounded by the cladding region. However, the amount of change between the refractive index of the mother glass before ion exchange and the maximum refractive index after ion exchange can be considered the same as when ion exchange is performed under the same conditions with masking to form a core region that will become an optical waveguide. Furthermore, the difference between the refractive index after ion exchange and the refractive index of cladding region B in cladding layer B can be considered the same as the difference in refractive index when ion exchange is performed under the same conditions with masking to form a core region that will become an optical waveguide.

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152] <Evaluation> <Refractive Index> The refractive index N of the glass plates G1 to G18 and G'1 to G'21 was measured using an automatic refractive index measuring instrument (KPR3000, manufactured by Shimadzu Corporation) at a wavelength of 589 nm. For the glass plates obtained through the ion exchange treatment described in A1 to A42, the refractive index was measured every 0.5 μm in the depth direction from the surface of the glass plate using a two-beam interferometer (TD-10020, manufactured by Mizojiri Optical Co., Ltd.), and the maximum refractive index Nmax was measured. For A1 to A29, it was confirmed that the refractive index at the surface of the glass plate was the maximum value Nmax, and that the refractive index decreased as the thickness from the surface of the glass plate increased. These results are shown in Tables 1 to 7. That is, Tables 1 to 4 show the refractive index N of light with a wavelength of 589 nm for glass plates G1 to G18 and G'1 to G'21, and Tables 5 to 7 show the refractive index change Δn, which is the difference between the maximum refractive index Nmax of the core region and the refractive index of the mother glass corresponding to the refractive index N of the glass constituting the cladding region A.

[0153] <Relative permittivity, dielectric loss tangent> Glasses G1 to G18 and G'1 to G'21 were processed into plates measuring 30.0 mm in length, 30.0 mm in width, and 0.5 mm in thickness, and the 30.0 mm x 30.0 mm surface was polished to a mirror finish. Using a network analyzer, the relative permittivity ε' and dielectric loss tangent tanδ at 10 GHz were measured by the slip post dielectric resonance method (SPDR method). The results are shown in Tables 1 to 4, respectively.

[0154] <Thermal expansion coefficient> For glasses G1 to G18 and G'1 to G'21, the thermal expansion coefficient CTE was measured using a differential thermal dilatometer according to the method specified in JIS R3102 (1995). The measurement temperature range was 50 to 350°C, and the unit was expressed as / K. Samples used were crystallized glass plates after heat treatment that were machined into circular (cylindrical) shapes with a diameter of 5 mm and a thickness of 20 mm. The results are shown in Tables 1 to 4, respectively.

[0155] <<Manufacturing of Optical Waveguide Substrate>> One embodiment of the optical waveguide substrate according to this embodiment employs any one of glasses G1 to G17 listed in Table 1 or Table 2, and partially ion-exchanges the glass to form cladding layer A. One embodiment of ion exchange is shown in Tables 5 to 7, and the maximum refractive index Nmax of the core region obtained by ion exchange is, for example, the value listed in A1 to A13 and A15 to A42 in Tables 5 to 7. Meanwhile, one embodiment of cladding layer B employs any one of glasses G1 to G18 listed in Table 1 or Table 2, or glasses G'1 to G'21 listed in Table 3 or Table 4. The cladding layers A and B may be combined to satisfy the desired physical properties, taking into consideration their respective refractive indices and thermal expansion coefficients. For example, the optical waveguide substrate according to this embodiment can be realized by employing a cladding layer A having a core region such as A1 to A13 and A15 to A42 from among the glasses A1 to A42 obtained above, and appropriately combining this with a cladding layer B. An example is shown below, but the optical waveguide substrate according to this embodiment is not limited to the following combination.

[0156] <Optical Waveguide Substrate 1> An example of an optical waveguide substrate according to this embodiment is the following combination. G14 glass is used as the glass for cladding layer A, and the core region of cladding layer A can be produced by masking and performing ion exchange on a portion of the region under the same conditions as A27. G'5 glass is used as the glass for cladding layer B. Cladding layer A and cladding layer B are bonded by directly bonding the glass plates together using thermocompression bonding. This results in an optical waveguide substrate.

[0157] <Optical Waveguide Substrate 2> The following combination can be given as an example of an optical waveguide substrate according to this embodiment. The cladding layer A having a core region is the same as that of the optical waveguide 1. The cladding layer B is made of G'5 glass and a 1 μm thick adhesive with a refractive index of 1.5283. The cladding layer A and the cladding layer B are bonded together using the adhesive that constitutes the cladding layer B. In this way, an optical waveguide substrate is obtained.

[0158] <Optical Waveguide Substrate 3> An example of an optical waveguide substrate according to this embodiment is the following combination. G2 glass is used as the glass for cladding layer A, and the core region of cladding layer A can be produced by masking and performing ion exchange on a portion of the region under the same conditions as A16. Cladding layer B is made of G'1 glass and a 15 μm thick adhesive with a refractive index of 1.559. Cladding layer A and cladding layer B are bonded together using the adhesive that constitutes cladding layer B. In this way, an optical waveguide substrate is obtained.

[0159] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2023-218368) filed on December 25, 2023, the contents of which are incorporated herein by reference.

[0160] 10, 10', 10'', 10''' Optical waveguide substrate 11, 11', 11'', 11''' Cladding layer A 21, 21', 21'', 21''' Cladding region A 31, 31', 31'', 31''' Core region 12, 12', 12'', 12''' Cladding layer B 22, 22', 22'', 22''' Cladding region B 32, 32', 32'', 32''' Glass layer or resin layer 33, 33', 33'', 33''' Adhesive layer

Claims

1. It has a cladding layer A and a cladding layer B joined to the cladding layer A. The cladding layer A is composed of glass having a cladding region A and a core region having a refractive index higher than that of the cladding region A. The glass constituting the cladding region A contains 5% or more of Na ２ O in terms of mol% based on oxides. The glass constituting the core region contains Na ２ O and Ag ２ O, and has a lower content ratio of Na ２ O and a higher content ratio of Ag ２ O than the glass constituting the cladding region A. The core region is located in a region including a part of the surface of the cladding layer A on the side of the cladding layer B. The cladding layer B has a cladding region B having a refractive index lower than that of the core region of the cladding layer A, an optical waveguide substrate.

2. The clad layer B is composed of a glass layer or a resin layer, and the clad layer A and the glass layer or the resin layer are directly joined. The optical waveguide substrate according to claim 1.

3. The clad layer B is composed of an adhesive layer and a glass layer or a resin layer. The thickness of the adhesive layer is less than 5 μm. The clad region B is composed of the adhesive layer and the glass layer or the resin layer. The clad layer A and the clad layer B are joined via the adhesive layer. The optical waveguide substrate according to claim 1.

4. The clad layer B is composed of an adhesive layer and a glass layer or a resin layer. The thickness of the adhesive layer is 5 μm or more. The clad region B is composed of the adhesive layer. The clad layer A and the clad layer B are joined via the adhesive layer. The optical waveguide substrate according to claim 1.

5. The refractive index difference between the adhesive layer constituting the clad region B and the glass constituting the clad region A is 0.1 or less. The optical waveguide substrate according to claim 3.

6. The refractive index difference between the adhesive layer constituting the clad region B and the glass constituting the clad region A is 0 to 0.003, and the thickness of the adhesive layer is 5 to 100 μm. The optical waveguide substrate according to claim 4.

7. The dielectric loss tangent of the material constituting the clad region B at 10 GHz is 0.01 or less. The optical waveguide substrate according to any one of claims 1 to 4.

8. The coefficient of thermal expansion of the material constituting the cladding region B is 5×10 －７ to 120×10 －７ / K. The optical waveguide substrate according to any one of claims 1 to 4.

9. The clad layer B is composed of the adhesive layer and the glass layer, and the glass constituting the clad region B has a lower Na ２ O content ratio than the glass constituting the clad region A. The optical waveguide substrate according to claim 3.

10. The glass constituting the cladding region A satisfies, in terms of mol% based on oxides, SiO ２ 45 to 80%, Al ２ O ３ 0 to 15%, B ２ O ３ 0 to 20%, a total of 10 to 30% of MgO, CaO, SrO and BaO, and 5 to 25% of Na ２ O. The optical waveguide substrate according to any one of claims 1 to 4.

11. The cladding layer B is composed of an adhesive layer and a glass layer. The thickness of the adhesive layer is 5 μm or more. The cladding region B is composed of the adhesive layer. The glass constituting the glass layer of the cladding layer B is expressed in mol% based on oxides as follows: SiO ２ 57 to 70%, Al ２ O ３ 5 to 15%, B ２ O ３ 15 to 24%, MgO 0.1 to 10%, CaO 0.1 to 10%, SrO 0.1 to 10%, BaO 0 to 10%, and ZnO 0 to 0.1%. The optical waveguide substrate according to claim 10, satisfying the above conditions.

12. In the clad layer A, the difference between the maximum value of the refractive index of the core region and the refractive index of the clad region A is 0.003 to 0.

06. The optical waveguide substrate according to any one of claims 1 to 4.

13. An optical device comprising the optical waveguide substrate according to any one of claims 1 to 4, and an optical coupler that extracts at least a part of the light transmitted by the optical waveguide substrate to the outside.

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