Optical waveguide element and optical waveguide sheet

Abstract

The present invention provides an optical waveguide element in which two optical waveguide sections having different absolute values of refractive indices of a core section and a cladding section and different refractive index differences between the core section and the cladding section are connected with high coupling efficiency. An optical waveguide element is provided with a coupling section (120) in which a first optical waveguide section (100) provided with a first cladding section (101) and a first cladding section (102) and a second optical waveguide section (110) provided with a second core section (111) and a second cladding section (112) are stacked. The optical waveguide element is characterized in that the respective core sections (101, 111) and the respective cladding sections (102, 112) individually have different refractive indices at a wavelength of 1300 nm and in that the difference in refractive index between the first cladding section (102) and the second cladding section (112) at a wavelength of 1300 nm is not greater than 0.05.

Description

Optical waveguide elements and optical waveguide sheets

[0001] This invention relates to optical waveguide elements and optical waveguide sheets.

[0002] In recent years, with the advancement of information and communication technology, communication traffic in data centers has been increasing dramatically. Therefore, optical wiring technology for components within computer chassis is becoming increasingly important. Among these technologies, silicon photonics, which integrates silicon optical waveguides, is attracting particular attention.

[0003] Silicon optical waveguides consist of a silicon core and a silicon dioxide cladding, resulting in a large difference in refractive index between the core and cladding, approximately 40%. Therefore, they enable optical propagation in extremely small cross-sectional areas of a few hundred nanometers in the near-infrared region (800-2500 nm), and also have a small allowable bending radius of a few micrometers. This allows for the high-density integration of complex patterns.

[0004] Incidentally, in optical communications, it is necessary to connect such silicon optical waveguides to optical fibers. Because silicon optical waveguides and optical fibers have significantly different core diameters and pitches, attempting to connect them directly results in very low coupling efficiency. Several coupling structures have been proposed to improve the coupling efficiency between the two, but one method involves introducing an optical waveguide made of polymer or glass between the silicon optical waveguide and the optical fiber to convert the spot size and pitch.

[0005] Because the polymer and glass optical waveguides mentioned above have different core diameters from silicon optical waveguides, butt coupling results in significant connection losses. Therefore, one approach to improve coupling efficiency is to use a coupling structure in which the two are stacked. In this coupling structure, the tip of the core portion of the silicon optical waveguide is tapered, and the effective refractive index changes, causing evanescent light to leak out of the silicon optical waveguide and causing optical coupling. For example, Patent Document 1 proposes a structure in which an optical waveguide with a large difference in refractive index between the core and cladding and an optical waveguide with a small difference in refractive index between the core and cladding are stacked in order to efficiently connect them. Furthermore, Patent Document 2 proposes an optical waveguide element equipped with two optical waveguides coupled by a so-called adiabatic coupling method, in order to perform highly efficient spot size conversion between two optical waveguide cores of different diameters, by tapering the tip of the smaller diameter core and transferring the leaked evanescent light to the larger diameter core.

[0006] Japanese Patent Publication No. 2007-52328 Japanese Patent Publication No. 2013-250435

[0007] However, with the aforementioned coupling method, the coupling efficiency and alignment tolerance change depending on the relative refractive indices of the core and cladding portions of each optical waveguide. Therefore, precise refractive index control is crucial, requiring appropriate structural design and constituent materials to achieve this.

[0008] The present invention was made to solve the above-mentioned problems and provides an optical waveguide element that connects two optical waveguide sections, which are adiabatically coupled, with high coupling efficiency, using two optical waveguide sections with different absolute refractive indices of the core and cladding sections, and different refractive index differences between the core and cladding sections.

[0009] As a result of diligent research by the inventors, we have discovered that coupling efficiency can be improved when the refractive index of each core and cladding in the connected optical waveguide section satisfies specific conditions, and have arrived at the present invention. The present invention comprises the following embodiments [1] to

[19] .

[0010] [1] An optical waveguide element comprising a coupling portion in which a first optical waveguide portion comprising a first core portion and a first cladding portion and a second optical waveguide portion comprising a second core portion and a second cladding portion are adiabatically coupled, wherein the refractive indices of the first core portion and the first cladding portion at a wavelength of 1300 nm are different, the refractive indices of the second core portion and the second cladding portion at a wavelength of 1300 nm are different, the refractive index of the second core portion at a wavelength of 1300 nm is 0.01 or greater than the refractive index of the first cladding portion at a wavelength of 1300 nm, and the absolute value of the refractive index difference between the first cladding portion and the second cladding portion at a wavelength of 1300 nm is 0.05 or less.

[0011] [2] In the wavelength range of 1000 to 2000 nm, there exists propagating light such that the relationship between the coupling efficiency X of the TE polarization component and the coupling efficiency Y of the TM polarization component of the first optical waveguide and the second optical waveguide is X / Y ≥ 1.0. The optical waveguide element according to [1].

[0012] [3] The optical waveguide element according to [1] or [2], wherein the absolute value of the refractive index difference is 0.03 or less.

[0013] [4]. An optical waveguide element according to [2] or [3], wherein there is propagating light in the range of wavelength 1260 to 1360 nm or 1460 to 1675 nm where X / Y ≥ 1.0.

[0014] [5] The optical waveguide element according to [2] or [3], wherein the wavelength of the propagating light is 1300 nm or 1550 nm.

[0015] [6] The optical waveguide element according to any one of [1] to [5], wherein the refractive index of the first core portion at a wavelength of 1300 nm is greater than the refractive index of the second core portion at a wavelength of 1300 nm.

[0016] [7] The optical waveguide element according to any one of [1] to [6], wherein the difference in relative refractive index between the first core portion and the first cladding portion at a wavelength of 1300 nm is greater than the difference in relative refractive index between the second core portion and the second cladding portion at a wavelength of 1300 nm.

[0017] [8] The optical waveguide element according to [6], wherein the plan view shape of the tip of the first core portion in the coupling portion is tapered, with the tip becoming narrower.

[0018] [9] The optical waveguide element according to [7], wherein the plan view shape of the tip of the first core portion in the coupling portion is tapered, with the tip becoming narrower.

[0019]

[10] The optical waveguide element according to [8], wherein the taper length at the tip of the first core portion is 100 μm or more.

[0020]

[11] The optical waveguide element according to [9], wherein the taper length at the tip of the first core portion is 100 μm or more.

[0021]

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

[11] , wherein the first core portion and the first cladding portion are each independently composed of at least one selected from the group consisting of Si, SiN, SiON, SiOx and those containing impurities thereon.

[0022]

[13] . The optical waveguide element according to any one of [1] to

[12] , wherein in the coupling portion, when the maximum length in the width direction of the cross-section of the second core portion is W [μm] and the maximum length in the height direction is H [μm], H / W is 0.1 to 10.

[0023]

[14] The optical waveguide element according to any one of [1] to

[13] , wherein the distance between the first core portion and the second core portion in the coupling portion is 10 μm or less.

[0024]

[15] The optical waveguide element according to any one of [1] to

[14] , wherein, in the joint, the angle between the line connecting the cross-sectional center of the first core and the cross-sectional center of the second core and the interface between the first optical waveguide and the second optical waveguide is 60° to 120°.

[0025]

[16] The optical waveguide element according to any one of [1] to

[15] , wherein the second core portion and / or the second cladding portion are formed from a polymer material.

[0026]

[17] The optical waveguide element according to any one of [1] to

[16] , wherein the second core portion and / or the second cladding portion are formed by curing an organopolysiloxane-containing composition.

[0027]

[18] An optical waveguide sheet comprising a second optical waveguide portion having a structure that can be adiabatically coupled with an optical waveguide portion 1 provided by an optical waveguide device, wherein the second optical waveguide portion comprises a second core portion and a second cladding portion, the refractive indices of the core portion and the cladding portion of the optical waveguide portion 1 at a wavelength of 1300 nm are different, the refractive indices of the second core portion and the second cladding portion at a wavelength of 1300 nm are different, the refractive index of the second core portion at a wavelength of 1300 nm is 0.01 or greater than the refractive index of the cladding portion of the optical waveguide portion 1 at a wavelength of 1300 nm, and the absolute value of the difference in refractive index between the second cladding portion and the cladding portion of the optical waveguide portion 1 at a wavelength of 1300 nm is 0.05 or less.

[0028]

[19] The optical waveguide sheet according to

[18] , wherein the second optical waveguide section has a configuration in which, in the wavelength range of 1000 to 2000 nm, there exists propagating light such that the relationship between the coupling efficiency X of the TE polarization component and the coupling efficiency Y of the TM polarization component of the optical waveguide section 1 and the second optical waveguide section is X / Y ≥ 1.0.

[0029] According to the present invention, two optical waveguide sections, each having different absolute refractive indices for the core and cladding sections, and different refractive index differences between the core and cladding sections, can be adibatially coupled and connected with high coupling efficiency.

[0030] This is a schematic cross-sectional view of the vicinity of the coupling portion where the second optical waveguide portion is stacked on the first optical waveguide portion in an optical waveguide element according to one embodiment of the present invention. This is a cross-sectional view of the optical waveguide element of Figure 1, cut in the direction of light propagation near the coupling portion. This is a partial perspective plan view of the optical waveguide element of Figure 1, viewed from above near the coupling portion, showing one example. This is a partial perspective plan view of the optical waveguide element of Figure 1, viewed from above near the coupling portion, showing another example. This is a cross-sectional view of the optical waveguide element of Figure 1, showing the relationship between the width and height of the first core portion. This is a cross-sectional view of the optical waveguide element of Figure 1, showing the height of the first cladding portion. This is a cross-sectional view of the optical waveguide element of Figure 1, showing the relationship between the width and height of the second core portion. This is a cross-sectional view of the optical waveguide element of Figure 1, showing the height of the second cladding portion. This is a cross-sectional view showing the gap between the first core portion and the second core portion of the optical waveguide element in Figure 1. This is a cross-sectional view showing a configuration in which the first core portion and the second core portion are in contact with each other in the optical waveguide element in Figure 1. This is a cross-sectional view showing a configuration in which the cross-sectional centers of the first core portion and the cross-sectional centers of the second core portion are offset from each other in the optical waveguide element in Figure 1. This is a cross-sectional view showing a configuration in which an adhesive layer is provided between the first optical waveguide portion and the second optical waveguide portion of the optical waveguide element in Figure 1, showing one example. This is a cross-sectional view showing a configuration in which an adhesive layer is provided between the first optical waveguide portion and the second optical waveguide portion of the optical waveguide element in Figure 1, showing another modified example. This is a cross-sectional view showing a configuration in which an adhesive layer and a barrier layer are provided between the first optical waveguide portion and the second optical waveguide portion of the optical waveguide element in Figure 1.

[0031] The following describes one embodiment of the optical waveguide element of the present invention. However, the present invention is not limited in any way to this embodiment. In the present invention, "(meth)acrylic" means "either acrylic or methacrylic or both." Also, a numerical range expressed using "~" means a range that includes the numbers written before and after "~" as the lower and upper limits. Furthermore, weight-average molecular weight means the weight-average molecular weight (Mw) in polystyrene equivalent obtained by gel permeation chromatography (GPC).

[0032] (Optical Waveguide Element) An optical waveguide element (also referred to as this optical waveguide element) according to one embodiment of the present invention, as shown in Figure 1, comprises a first optical waveguide section 100 having a first core section 101 and a first cladding section 102 covering it, and a second optical waveguide section 110 having a second core section 111 and a second cladding section 112 covering it, wherein the first optical waveguide section 100 and the second optical waveguide section 110 are adibatially coupled and stacked such that the second core section 111 is positioned above the first core section 101. As shown in Figure 2, the overlapping portion of the first core section 101 and the second core section 111 is designated as a coupling section 120, enabling optical propagation between the first core section 101 and the second core section 111. The length 121 of the joint portion 120 is not particularly limited, but is preferably 100 μm or more, more preferably 200 μm or more, and even more preferably 400 μm or more. In this embodiment, the second core portion 111 is stacked so as to be positioned above the first core portion 101, but it is sufficient for the second core portion 111 to be positioned adjacent to the first core portion 101, or for the second core portion 111 to be positioned around the first core portion 101 in directions such as below, left and right, or diagonally. Furthermore, each cladding portion 102, 112 may cover the entire core portion 101, 111, or it may cover a part of it while leaving it exposed.

[0033] The wavelength of light guiding the first core portion 101 of the first optical waveguide portion 100 and the second core portion 111 of the second optical waveguide portion 110 is preferably in the range of 1260 to 1360 nm or 1460 to 1675 nm, more preferably in the range of 1300 to 1310 nm or 1550 nm, even more preferably 1300 nm, 1310 nm or 1550 nm, and particularly preferably 1300 nm or 1550 nm, from the viewpoint of suppressing absorption originating from C-H bonds and O-H bonds and reducing transmission loss.

[0034] The first core portion 101 and the first cladding portion 102 have a refractive index difference. This allows light to propagate while being reflected at the interface between the two. In particular, the refractive index n of the first core portion 101 101 The refractive index n of the first cladding portion 102 102When it is larger than that, under specific conditions, light is totally reflected at the interface between the first core portion 101 and the first clad portion 102, and the light can be confined within the first core portion 101.

[0035] Assume that the second core portion 111 and the second clad portion 112 have a refractive index difference. Thereby, light propagates while being reflected at the interface between the two. In particular, the refractive index n of the second core portion 111 111 is the refractive index n of the second clad portion 112 112 When it is larger than that, under specific conditions, light is totally reflected at the interface between the core portion 111 and the clad portion 112, and the light can be confined within the core portion 111.

[0036] Hereinafter, it will be described assuming that the refractive index difference between the first core portion 101 and the first clad portion 102 of the first optical waveguide portion 100 is large, and the refractive index difference between the second core portion 111 and the second clad portion 112 of the second optical waveguide portion 110 is small. However, the present invention is not limited to this, and the reverse configuration may be adopted.

[0037] (First optical waveguide portion) The first optical waveguide portion 100 can suppress an increase in propagation loss when a sharp bend occurs in the light propagation path by increasing the refractive index difference between the first core portion 101 and the first clad portion 102.

[0038] The relative refractive index difference [Δ 100 between the first core portion 101 and the first clad portion 102 in the first optical waveguide portion 100 is defined as follows. Δ 100 = 100×(n 101 2 - n 102 2 ) / 2n 101 2

[0039] In the first optical waveguide section 100, the relative refractive index difference at a wavelength of 1300 nm is preferably 10% or more, and more preferably 20% or more. There is no particular upper limit, but it is preferably 80% or less, and more preferably 60% or less. For example, by setting the refractive index of the first core section 101 at a wavelength of 1300 nm to 3.50 and the refractive index of the first cladding section 102 at a wavelength of 1300 nm to 1.45, the relative refractive index difference at a wavelength of 1300 nm becomes 41.4%. When the relative refractive index difference is within the above range, it tends to be possible to achieve sharp bending, for example, with a bending radius of about 1 μm.

[0040] (Second Optical Waveguide Section) The second optical waveguide section 110 can achieve single-mode waveguide even with a wide core of several micrometers by reducing the refractive index difference between the second core section 111 and the second cladding section 112.

[0041] The relative refractive index difference Δ between the second core portion 111 and the second cladding portion 112 in the second optical waveguide portion 110. 110 Δ is defined as follows: 110 = 100 × (n 111 2 -n 112 2 ) / 2n 111 2

[0042] In the second optical waveguide section 110, which has a small refractive index difference, the relative refractive index difference at a wavelength of 1300 nm is preferably 5% or less, and more preferably 2% or less. The lower limit is not particularly limited, but it is preferably 0.1% or more, and more preferably 0.5% or more. For example, by setting the refractive index of the second core section 111 at a wavelength of 1300 nm to 1.469 and the refractive index of the second cladding section at a wavelength of 1300 nm to 1.450, the relative refractive index difference at a wavelength of 1300 nm becomes 1.29%. When the relative refractive index difference is within the above range, single-mode waveguides tend to be realized with a core diameter of, for example, about 3 μm.

[0043] ​(Plan view shape of the first core portion) The first core portion 101 of the first optical waveguide portion 100 is preferably formed in a tapered shape in plan view at the coupling portion 120, as shown in Figure 3-1, where it becomes narrower towards the tip. By forming the tip of the first core portion 101 in a tapered shape, evanescent light can be efficiently leaked out from the first core portion 101. In this optical waveguide element, a tapered shape is simply a shape that becomes narrower towards the tip, and the change in shape does not have to be constant. When the tip of the first core portion 101 is tapered, the top (tip portion) may be pointed, but it may also be a flat end surface obtained by cutting off the top.

[0044] The taper angle 122 at the tip of the first core portion 101 of the first optical waveguide portion 100 represents the angle between the point where the plan view shape of the core portion 101 begins to narrow and the tip of the core portion 101, as shown by the dashed line in Figure 3-1. If the tip of the core portion 101 is not pointed and is a flat end surface obtained by cutting off the top, the taper angle 122 can be estimated by extending the top and taking the point where the two lines intersect as the tip, as shown in Figure 3-2. The taper angle 122 at the tip of the first core portion 101 of the first optical waveguide portion 100 is preferably less than 1°, and more preferably 0.1° or less. The taper length 123 is preferably 100 μm or more, more preferably 200 μm or more, particularly preferably 400 μm or more, and most preferably 1000 μm or more.

[0045] As shown in Figure 4-1, the maximum length 146 in the width direction (horizontal direction) and the maximum length 147 in the height direction (vertical direction) of the first core portion 101 are not particularly limited. However, for example, if the material forming the core portion 101 is silicon (Si) and the material forming the cladding portion 102 is silicon dioxide, in order to make the waveguide mode a single mode, it is preferable that the maximum length in the width direction (horizontal direction) and height direction (vertical direction) of the core portion 101 be 0.5 μm or less. As shown in Figure 4-2, the maximum length 148 in the height direction (vertical direction) of the first cladding portion 102 is preferably 5 μm or more, and more preferably 10 μm or more.

[0046] (Material for the first optical waveguide section) The material forming the first core section 101 of the first optical waveguide section 100 can be any material that is transparent to light of wavelengths used in optical communication, and is preferably Si, SiON, SiN, SiOx, SiGe, InP, GaAs, or a mixture of these materials, with Si being particularly preferred from the viewpoint of processability and the like. The material forming the first core section 101 has a refractive index of 1.0 to 10 at a wavelength of 1300 nm, and more preferably 1.4 to 4.0. This material may contain other impurities, such as phosphorus, arsenic, and antimony.

[0047] The material forming the first cladding portion 102 of the first optical waveguide portion 100 can be any material that is transparent to light of wavelengths used in optical communication, and Si, SiON, SiN, SiOx, SiGe, InP, GaAs, or mixtures thereof are preferred. The material forming the first cladding portion 102 preferably has a refractive index of 1.0 to 10 at a wavelength of 1300 nm, more preferably 1.0 to 4.0, and has a different refractive index from that of the first core portion 101.

[0048] (Cross-sectional shape of the second core) As shown in Figure 5-1, the cross-sectional shape of the second core 111 of the second optical waveguide section 110 is such that when the maximum length 142 in the width direction (horizontal direction) of the cross-section of the second core 111 is W [μm] and the maximum length 143 in the height direction (vertical direction) is H [μm], the ratio H / W between the two is preferably 0.1 to 10, more preferably 0.1 to 5, and even more preferably 0.1 to 1. By setting H / W within this range, the optical coupling efficiency between the first core 101 of the first optical waveguide section 100 and the second core 111 of the second optical waveguide section 110 can be increased, and the polarization-dependent loss of light propagating through the second optical waveguide section 110 can be reduced. In this optical waveguide element, the cross-sectional shape of the second core 111 is square to rectangular, but it is not limited to this. For example, the cross-sectional shape may be a trapezoid, a circle, a semicircle, or other shape.

[0049] The aforementioned W and H can be identified by cutting the optical waveguide element and observing the cross-sectional shape of the core, for example, by using a scanning electron microscope (SEM).

[0050] The optical waveguide element may have different values ​​of H in some parts, as long as the H / W ratio satisfies the above range. For example, the H may be different at one end and the other end of the second optical waveguide section 110. Also, the H may be different at both ends of the second optical waveguide section 110 and at the intermediate part of the second core section 111 in the optical propagation direction.

[0051] Furthermore, in the case of an optical waveguide element in which multiple core portions 111 are arranged in parallel with respect to a cladding portion 112, there may be some core portions 111 whose maximum length in the height direction (H) and maximum length in the width direction (W) of the core portion 111 do not meet the above range. Specific examples of core portions 111 that do not meet the above range include core portions 111 used for positioning when connecting optical waveguide elements.

[0052] (Second cladding portion) As shown in Figure 5-2, the maximum length 145 in the height direction (vertical direction) of the second cladding portion 112 is not particularly limited, but is preferably 5 μm or more, and more preferably 10 μm or more.

[0053] (Distance between the first core and the second core) In this optical waveguide element, as shown in Figure 6, if there is a distance (gap) 141 between the first core 101 of the first optical waveguide section 100 and the second core 111 of the second optical waveguide section 110, the distance (gap) is preferably 10 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less. By making the distance 141 less than or equal to the above upper limit, the overlap of the mode fields of the light propagating through the first core 101 of the first optical waveguide section 100 and the light propagating through the second core 111 of the second optical waveguide section 110 increases, and the optical coupling efficiency can be improved. Furthermore, there is no particular lower limit to the distance (gap) 141. As will be described later, there may be no distance (gap). Note that the distance between the first core and the second core refers to the shortest vertical distance between the first core and the second core.

[0054] The distance 141 can be determined by cutting the optical waveguide element and observing the cross-sectional shapes of both cores 101 and 111, for example, by using a scanning electron microscope (SEM).

[0055] As shown in Figure 7, the first core portion 101 of the first optical waveguide portion 100 and the second core portion 111 of the second optical waveguide portion 110 may be in direct contact with each other, with a distance of 0 μm between them. For example, by adopting the configuration shown in Figure 7, the overlap of the mode fields between the first core portion 101 and the second core portion 111 can be increased, thereby improving the coupling efficiency.

[0056] (Arrangement of the first and second core portions) In this optical waveguide element, as shown in Figure 8, the angle 144 formed by the line connecting the cross-sectional center of the first core portion 101 of the first optical waveguide portion 100 and the cross-sectional center of the second core portion 111 of the second optical waveguide portion 110, and the line (interface) where the first cladding portion 102 of the first optical waveguide portion 100 and the second core portion 111 of the second optical waveguide portion 110 are in contact, i.e., the axial misalignment between the first and second core portions, is preferably in the range of 60° to 120°, more preferably 70° to 110°, even more preferably 80° to 100°, and most preferably 90° (vertical direction). By setting the angle 144 between the two lines within this range, the axial misalignment between the first core portion 101 of the first optical waveguide section 100 and the second core portion 111 of the second optical waveguide section 110 is reduced, increasing the overlap of the mode fields between the light propagating through the first core portion 101 of the first optical waveguide section 100 and the light propagating through the second core portion 111 of the second optical waveguide section 110, thereby improving the optical coupling efficiency. In the present invention, the center of the cross-section of the core portion is defined as the midpoint of the length W in the width direction (horizontal direction) of the cross-section of the core portion at H / 2 of the cross-section of the core portion, assuming that H is the maximum length in the height direction (vertical direction) of the cross-section of the core portion.

[0057] The angle 144 formed by the two lines can be determined by cutting the optical waveguide element and observing the cross-sectional shape of the core, for example, by using a scanning electron microscope (SEM).

[0058] (Refractive index of the second optical waveguide section) The refractive index of the second core section 111 of the second optical waveguide section 110 at a wavelength of 1300 nm is preferably 1.00 to 2.00, and more preferably 1.40 to 1.70. It is also preferable that the refractive index of the second core section 111 is different from that of the first core section 101 and the first cladding section 102. The refractive index of the second cladding section 112 at a wavelength of 1300 nm is preferably 1.00 to 2.00, and more preferably 1.40 to 1.50. It is also preferable that the refractive index of the second cladding section 112 is different from that of the first core section 101, the first cladding section 102, and the second core section 111.

[0059] (Difference in refractive index between the first cladding portion and the second core portion) The refractive index of the second core portion 111 of the second optical waveguide portion 110 at a wavelength of 1300 nm is preferably 0.01 or greater than the refractive index of the first cladding portion 102 of the first optical waveguide portion 100 at a wavelength of 1300 nm. It is more preferably 0.015 or greater, and even more preferably 0.02 or greater. There is no particular upper limit, but it is usually 0.1 or less. By setting the difference between the refractive index of the second core portion 111 of the second optical waveguide portion 110 at a wavelength of 1300 nm and the refractive index of the first cladding portion 102 of the first optical waveguide portion 100 at a wavelength of 1300 nm within this range, the coupling efficiency of the TE polarization component can be increased.

[0060] (Difference in refractive index between the first cladding portion and the second cladding portion) The absolute value of the difference in refractive index at a wavelength of 1300 nm between the refractive index of the first cladding portion 102 of the first optical waveguide portion 100 and the second cladding portion 112 of the second optical waveguide portion 110 is preferably 0.05 or less. By setting the difference in refractive index between the first cladding portion 102 of the first optical waveguide portion 100 and the second cladding portion 112 of the second optical waveguide portion 110 to this range, the mode field of the light guiding the second core portion 111 spreads out in a circular shape, increasing the overlap with the mode field of the light guiding the first core portion 101, and thereby increasing the coupling efficiency. From this viewpoint, the absolute value of the refractive index difference is more preferably 0.04 or less, even more preferably 0.03 or less, and particularly preferably 0.02 or less. The difference between the refractive index of the second cladding portion 112 of the second optical waveguide portion 110 and the refractive index of the first cladding portion 102 of the first optical waveguide portion 100 at a wavelength of 1300 nm ((refractive index of the second cladding portion 112) - (refractive index of the first cladding portion 102)) is preferably -0.02 or higher, more preferably -0.015 or higher, and even more preferably -0.01 or higher. On the other hand, it is preferably 0.05 or lower, more preferably 0.045 or lower, and even more preferably 0.04 or lower. For example, the range of -0.02 to 0.05 is preferred, the range of -0.015 to 0.045 is more preferred, and the range of -0.01 to 0.04 is even more preferred. The median value of the numerical range is not necessarily preferably zero and tends to change depending on the combination of refractive indices of each core portion and each cladding portion.

[0061] (Refractive index of the first core portion and the second core portion) Preferably, the refractive index of the first core portion at a wavelength of 1300 nm is greater than the refractive index of the second core portion at a wavelength of 1300 nm. A larger refractive index in the first core portion allows for a larger difference in the relative refractive index between the first core portion and the first cladding portion, which tends to reduce the allowable bending radius of the first optical waveguide portion. Depending on the material and refractive index of the cladding portion and the core portion, the refractive index of the first core portion at a wavelength of 1300 nm is preferably 0.50 or more greater than the refractive index of the second core portion at a wavelength of 1300 nm, more preferably 1.00 or more greater, even more preferably 1.80 or more greater, and particularly preferably 1.90 or more greater. Furthermore, the upper limit is preferably 2.50 or less, more preferably 2.20 or less, and even more preferably 2.10 or less.

[0062] In this optical waveguide element, an optical connection is made between the first core portion 101 of the first optical waveguide portion 100 and the second core portion 111 of the second optical waveguide portion 110. The coupling efficiency X of the TE polarization components of the first optical waveguide section and the second optical waveguide section refers to the coupling efficiency of the TE polarization component when light propagates from the first core section 101 of the first optical waveguide section 100 to the second core section 111 of the second optical waveguide section 110, or from the core section 111 of the second optical waveguide section 110 to the first core section 101 of the first optical waveguide section 100. The coupling efficiency Y of the TM polarization component refers to the coupling efficiency of the TM polarization component when light propagates from the first core section 101 of the first optical waveguide section 100 to the second core section 111 of the second optical waveguide section 110, or from the core section 111 of the second optical waveguide section 110 to the first core section 101 of the first optical waveguide section 100. In this case, when light propagates from the first optical waveguide to the second optical waveguide, and when light propagates from the second optical waveguide to the first optical waveguide, in at least one of these cases, the relationship between the coupling efficiency X (%) of the TE polarization component (Transverse Electric Wave) and the coupling efficiency Y (%) of the TM polarization component (Transverse Magnetic Wave) for light of a specific wavelength in the range of 1000 to 2000 nm is preferably X / Y ≥ 1.0, more preferably X / Y ≥ 1.2, and even more preferably X / Y ≥ 1.4. By setting X / Y within this range, noise in the light guiding the first core portion 101 of the first optical waveguide 100 can be reduced, and the transmission characteristics can be improved. Furthermore, although not particularly limited, X ≥ 70% is preferred, X ≥ 80% is more preferred, and X ≥ 90% is particularly preferred. Furthermore, Y ≤ 90% is preferred, Y ≤ 80% is more preferred, and Y ≤ 70% is particularly preferred. It is preferable that the coupling efficiency X and coupling efficiency Y satisfy the above relationship in both cases: when light propagates from the first optical waveguide to the second optical waveguide, and when light propagates from the second optical waveguide to the first optical waveguide. When the first optical waveguide and the second optical waveguide are single-mode waveguides, the coupling efficiency of the TE and TM polarization components is usually constant regardless of the direction of light propagation.The coupling efficiency X of the TE polarization component and the coupling efficiency Y of the TM polarization component can be obtained, for example, by coupling optical fibers to both ends of an optical waveguide element and evaluating the intensity of each emitted polarization component. Alternatively, estimation by optical simulation is also possible.

[0063] When light with a wavelength in the range of 1000 to 2000 nm propagates from the first core portion 101 of the first optical waveguide portion 100 to the second core portion 111 of the second optical waveguide portion 110, or from the core portion 111 of the second optical waveguide portion 110 to the first core portion 101 of the first optical waveguide portion 100, the wavelength of light that satisfies the above relational expression for the relationship between the coupling efficiency X of the TE polarization component and the coupling efficiency Y of the TM polarization component is preferably in the range of 1260 to 1360 nm or 1460 to 1675 nm, more preferably in the range of 1300 to 1310 nm or 1550 nm, even more preferably 1300 nm, 1310 nm or 1550 nm, and particularly preferably 1300 nm or 1550 nm.

[0064] For example, if the material forming the first cladding portion 102 of the first optical waveguide portion 100 is silicon dioxide, its refractive index in the near-infrared region (wavelength 1300 nm) is 1.45. In this case, given the above background, it is preferable that the refractive index of the second cladding portion 112 at a wavelength of 1300 nm be between 1.40 and 1.50. If the refractive index of the second cladding portion 112 exceeds 1.50, the mode field of the light guiding the second core portion 111 will be distorted towards the second cladding portion 112, leading to a decrease in the optical coupling efficiency with the first core portion 101. On the other hand, if the refractive index of the second cladding portion 112 is less than 1.40, it is preferable that the refractive index of the second core portion 111 at a wavelength of 1300 nm be less than 1.45 in order to achieve single-mode guidance. In this case, the refractive index of the first cladding portion 102 will be higher than that of the second core portion 111, resulting in a deterioration of transmission efficiency.

[0065] (Adhesive layer of optical waveguide element) In this optical waveguide element, an adhesive layer 131 may be provided between the first optical waveguide portion 100 and the second optical waveguide portion 110, as shown in Figure 9-1 or Figure 9-2. In Figure 9-1, the adhesive layer 131 is in a layered form, and in Figure 9-2, the second core portion 111 is embedded in the adhesive layer 131 and the upper part is covered with the second cladding portion 112.

[0066] As the material for the adhesive layer 131, for example, the material that forms the second cladding portion 112 can be used, and from the viewpoint of transparency in the near-infrared region, polymer materials such as those described later are preferred.

[0067] The refractive index of the adhesive layer 131 at a wavelength of 1300 nm is preferably close to the refractive index of the first cladding portion 102 of the first optical waveguide portion 100, and also preferably close to the refractive index of the second cladding portion 112 of the second optical waveguide portion 110. By setting the refractive index of the adhesive layer 131 within this range, the overlap of the mode fields of light propagating through the first core portion 101 of the first optical waveguide portion 100 and light propagating through the second core portion 111 of the second optical waveguide portion 110 increases, thereby improving the optical coupling efficiency. From this viewpoint, the refractive index of the adhesive layer 131 at a wavelength of 1300 nm is preferably in the range of ±0.10 relative to the refractive index of the first cladding portion 102, and more preferably in the range of ±0.05. Furthermore, it is preferably in the range of ±0.10 relative to the refractive index of the second cladding portion 112, and more preferably in the range of ±0.05.

[0068] From the viewpoint of bringing the refractive index of the adhesive layer 131 closer to that of the first cladding portion 102 of the first optical waveguide 100 and the second cladding portion 112 of the second optical waveguide portion 110, it is preferable that the adhesive layer 131 be made of the same material as either the first cladding portion 102 or the second cladding portion 112.

[0069] (Barrier layer of optical waveguide element) In this optical waveguide element, as shown in Figure 10, a barrier layer 150 may be formed on the surface of the first cladding portion 102 of the first optical waveguide 100 to suppress the diffusion of alkali metal ions such as sodium (Na). The thickness of the barrier layer 150 is, for example, 0.01 μm or more and 0.5 μm or less. As a material for forming the barrier layer 150, for example, silicon nitride (Si ３ N ４ ) can be used. In Figure 10, the adhesive layer 131 is provided on the barrier layer 150, but the barrier layer 150 may be provided on the adhesive layer 131.

[0070] (Material of the second optical waveguide section) From the viewpoint of transparency in the near-infrared region, polymer materials or silicon dioxide are preferred as the material for forming the second cladding section 112 of the second optical waveguide section 110. Among these, polymer materials are particularly preferred because they can be coated onto a substrate and complex patterns can be formed in a low-temperature processing process.

[0071] When the second core portion 111 and the second cladding portion 112 of the second optical waveguide portion 110 are formed from a polymer material, the polymer material can include organopolysiloxane, acrylic polymers, methacrylic polymers such as polymethyl methacrylate (PMMA), epoxy resins, oxetane resins, phenoxy resins, benzocyclobutene resins, norbornene resins, fluorine resins, phenolic resins, polyester resins, polycarbonate resins, polystyrene resins, polyamide resins, polyimide resins, poly(imide / isoindoquinazolindioneimide) resins, polyetherimide resins, polyetherketone resins, polyesterimide resins, polybenzoxazole resins, polysilanes, and the like. The second core portion 111 and the second cladding portion 112 of the second optical waveguide portion 110 are preferably formed by curing a composition containing an organopolysiloxane (hereinafter also referred to as an organopolysiloxane-containing composition), and more preferably by curing a composition containing a photocurable organopolysiloxane. The organopolysiloxane in this specification may contain metal atoms such as Ti and Zr in its structure. Organopolysiloxane is particularly transparent in the near-infrared wavelength band and has high heat resistance, making it suitable as a material for the second core portion 111 and the second cladding portion 112 of the second optical waveguide portion. Suitable organopolysiloxanes for this optical waveguide element will be described later.

[0072] Furthermore, for example, when using a polymer material to set the refractive index of the second cladding portion 112 of the second optical waveguide portion 110 to 1.40 to 1.50 at a wavelength of 1300 nm, the material forming the second cladding portion 112 is preferably an organopolysiloxane, a fluorine-containing polymer, a hollow filler-added resin, a silica filler-added resin, an acrylic resin, a methacrylic resin such as polymethyl methacrylate (PMMA), an epoxy resin, an oxetane resin, etc.

[0073] The material forming the second core portion 111 and the second cladding portion 112 of the second optical waveguide portion 110 preferably has high patternability when it is necessary to form a fine pattern. From the viewpoint of patternability, the polymer material forming the second core portion 111 and the second cladding portion 112 of the second optical waveguide portion 110 in the present invention preferably has polymerizable functional groups and exhibits curability.

[0074] Specific examples of polymerizable functional groups include vinyl groups, allyl groups, allyloxy groups, methacryloyl(oxy) groups, acryloyl(oxy) groups, vinyloxy groups, trifluorovinyl groups, trifluorovinyloxy groups, ethynyl groups, styryl groups, 1-oxocyclopenta-2,5-dien-3-yl groups, cyano groups, alkoxysilyl groups, oxirane groups, and epoxy groups. Vinyl groups, methacryloyl(oxy) groups, acryloyl(oxy) groups, trifluorovinyloxy groups, ethynyl groups, styryl groups, epoxy groups, and oxirane groups are preferred due to their high reactivity and high crosslinking density, with methacryloyl(oxy) groups or acryloyl(oxy) groups being more preferred, and methacryloyl(oxy) groups being the most preferred. Note that methacryloyl(oxy) groups refer to either methacryloyl groups or methacryloyloxy groups. The same applies to acryloyl(oxy) groups.

[0075] (Organopolysiloxane) The organopolysiloxane suitable for this optical waveguide element is preferably represented by the following formula [1]. (R １ R ２ R ３ SiO １／２ ) Ｍ１ (R ４ R ５ R ６ SiO １／２ ) Ｍ２ (R ７ R ８ SiO ２／２ ) Ｄ１ (R ９ R ６ SiO ２／２ ) Ｄ２ (R １０ SiO ３／２ ) Ｔ１(R ６ SiO ３／２ ) Ｔ２ (SiO ４／２ ) Ｑ (O １／２ R １１ ) Ｙ１ (O １／２ R ６ ) Ｙ２ ...[1]

[0076] In the above formula [1], R １ ~R ５ , R ７ ~R １１ Each of these is independently selected from the group consisting of organic groups and hydrogen atoms, one or more of these groups. １ ~R ３ , R ７ , R ８ , R １０ and R １１ It does not contain polymerizable functional groups. ６ is one or more organic groups containing polymerizable functional groups, and if there are multiple, they may be the same or different from each other, 0 ≤ M1, 0 ≤ D1, 0 ≤ T1, 0 ≤ Y1, 0 ≤ Y2, 0 ≤ Q 0 < M2 + D2 + T2, 0 < D1 + D2 + T1 + T2 + Q M1 + M2 + D1 + D2 + T1 + T2 + Q = 1.

[0077] In general formula [1], the coefficients M1, M2, D1, D2, T1, T2, and Q represent the proportions (based on moles) of each structure when M1 + M2 + D1 + D2 + T1 + T2 + Q = 1. Also, in general formula [1], the coefficients Y1 and Y2 represent the proportions (based on moles) of each structure when M1 + M2 + D1 + D2 + T1 + T2 + Q = 1. １／２ R １１ ) and (O １／２ R ６ This indicates the relative content (based on moles) of ).

[0078] In general formula [1], the coefficients M1 and M2 are so-called M-unit silicon (SiO₂), which has one oxygen atom bonded to a silicon atom. １／２ ) (Hereafter sometimes simply referred to as "M units") indicates the proportion of D-unit silicon (SiO₂) which has two oxygen atoms bonded to a silicon atom. ２／２) (Hereafter sometimes simply referred to as "D unit") indicates the proportion of T unit silicon (SiO2), where T1 and T2 are T unit silicon (SiO2) which has three oxygen atoms bonded to a silicon atom. ３／２ ) (Hereafter sometimes simply referred to as "T units") indicates the proportion of Q units of silicon (SiO₂), where Q is a silicon atom bonded to four oxygen atoms. ４／２ This indicates the proportion of (hereinafter sometimes simply referred to as "Q units"). M2, D2, and T2 are silicon atoms with R ６ This indicates the proportions of M units, D units, and T units to which organic groups containing polymerizable functional groups are bonded. Y1 represents the proportion of structures that do not contain polymerizable functional groups and have groups selected from the group consisting of organic groups and hydrogen atoms, specifically alkoxy groups or silanol groups, while Y2 represents the proportion of organic groups containing polymerizable functional groups bonded to silicon.

[0079] 0≦M1, 0≦D1, 0≦T1, 0≦Y1, 0≦Y2, 0≦Q means that M1, D1, T1, Y1, Y2, and Q are all greater than or equal to 0, and may be 0, meaning that the structural unit may not exist.

[0080] 0 < M2 + D2 + T2 is where R is present in the silicon atom. ６ This means that the organopolysiloxane has at least one of the M units, D units, or T units to which an organic group containing a polymerizable functional group is attached. 0 < D1 + D2 + T1 + T2 + Q means that the organopolysiloxane has at least one of the D units, T units, or Q units. M1 + M2 + D1 + D2 + T1 + T2 + Q = 1 means that the total proportion of M units, D units, T units, and Q units is 1.

[0081] <M2+D2+T2> In the organopolysiloxane represented by formula [1], if 0 < M2+D2+T2, the organopolysiloxane contains polymerizable functional groups, making it possible to easily obtain a cured product using a composition containing a polymerization initiator described later. If the content of polymerizable functional groups is too small, curing defects may occur during the preparation of the cured product, and the compatibility with other components added to the organopolysiloxane-containing composition described later will be poor. From these viewpoints, it is preferable that 0.10 ≤ M2+D2+T2, and more preferably that 0.12 ≤ M2+D2+T2. On the other hand, there is no particular upper limit to M2+D2+T2, but if the proportion of M2+D2+T2 is too large, the content of polymerizable functional groups increases, and the crosslinking density of the cured product increases, making it prone to brittleness. Therefore, it is preferable that M2+D2+T2 ≤ 0.75, and more preferably that M2+D2+T2 ≤ 0.60. As described above, it is preferable that 0.10 ≤ M2 + D2 + T2 ≤ 0.75, and even more preferable that 0.12 ≤ M2 + D2 + T2 ≤ 0.60.

[0082] <Q Units> Q units are the most oxidized form of silicon, and their inclusion in the structure of organopolysiloxanes can increase the heat resistance of the cured product. Q units are also found in quartz, and when organopolysiloxanes have Q units, a cured product having a refractive index close to that of the core material of a near-infrared single-mode silica-based optical fiber can be obtained using a composition containing the organopolysiloxane. In organopolysiloxanes represented by formula [1], Q units may or may not be present, but from the viewpoint of improving the heat resistance of the cured organopolysiloxane, it is preferable to have Q units, while from the viewpoint of improving the flexibility of the cured organopolysiloxane, it is preferable not to have Q units. When Q units are present, the coefficient Q is preferably greater than 0, and more preferably 0.04 or higher. On the other hand, if there are many Q units, the product will become solid or the viscosity will increase, reducing handling properties, so the upper limit is usually 0.65 or less, more preferably 0.6 or less, and even more preferably 0.45 or less. As described above, when the organopolysiloxane represented by formula [1] has Q units, the coefficient Q is preferably 0 < Q ≤ 0.65, more preferably 0.04 ≤ Q ≤ 0.6, and even more preferably 0.04 ≤ Q ≤ 0.45.

[0083] <D1+D2+T1+T2+Q> In the organopolysiloxane represented by formula [1], if 0 < D1+D2+T1+T2+Q, it is possible to introduce constituent units other than the M unit into the organopolysiloxane, which is advantageous from the viewpoint of curability and heat resistance after curing. 0.01 < D1+D2+T1+T2+Q is preferred, 0.1 < D1+D2+T1+T2+Q is more preferred, and 0.2 < D1+D2+T1+T2+Q is even more preferred. There is no particular upper limit, but by definition it is 1 or less. Furthermore, from the viewpoint of improving the heat resistance of the cured organopolysiloxane, it is preferable that the relation "0 < D1+D2+T1+T2+Q" in formula [1] be replaced with "0 < Q", that is, that it has a Q unit. This will be described later using formula [2].

[0084] <O １／２ R １１ > (O １／２ R１１ This structural unit does not have polymerizable functional groups and has a structure selected from the group consisting of organic groups and hydrogen atoms, specifically an alkoxy group and / or silanol group bonded to silicon. The viscosity of organopolysiloxane can be controlled by this structural unit and adjusted to a viscosity suitable for molding. Silanol groups have the effect of increasing viscosity, while alkoxy groups have the effect of decreasing viscosity. If the content of alkoxy groups or silanol groups is low, the amount of highly mobile end groups is small, and the siloxane skeleton becomes a rigid cage-like structure, thus increasing viscosity. Conversely, if the content of alkoxy groups or silanol groups is high, the amount of highly mobile end groups is large, and the siloxane skeleton becomes a flexible random structure rather than a cage-like structure, thus decreasing viscosity.

[0085] <Coefficient Y1> (O １／２ R １１ The coefficient Y1, which indicates the content ratio of ), is 0 or a positive value. In one embodiment, Y1 is R １１ From the definition, this indicates the total content ratio of silanol groups and alkoxy groups in the organopolysiloxane. The range of the coefficient Y1 is preferably 0 or more, more preferably 0.02 or more, even more preferably 0.025 or more, even more preferably 0.03 or more, and most preferably 0.035 or more, from the viewpoint of viscosity adjustment necessary for the synthesis of organopolysiloxane and the preparation of organopolysiloxane-containing compositions described later. On the other hand, from the viewpoint of storage stability and handling, the upper limit of the coefficient Y1 is preferably 0.25 or less, more preferably less than 0.25, even more preferably 0.2 or less, even more preferably 0.20 or less, most preferably 0.15 or less, and particularly preferably 0.1 or less. Preferred ranges in equation [1] are: 0.02 ≤ Y1 ≤ 0.25, more preferably 0.02 ≤ Y1 < 0.25, even more preferably 0.025 ≤ Y1 ≤ 0.2, even more preferably 0.025 ≤ Y1 ≤ 0.20, particularly preferably 0.03 ≤ Y1 ≤ 0.15, and especially preferably 0.035 ≤ Y1 ≤ 0.1. Y1 represents a relative value with respect to M1 + M2 + D1 + D2 + T1 + T2 + Q = 1.

[0086] <Coefficient Y2> Y2 is the proportion of one or more organic groups in the organopolysiloxane that contain polymerizable functional groups bonded to silicon via an oxygen atom. (O １／２ R ６ The coefficient Y2, which indicates the content of ), is 0 or a positive value, preferably Y2 > 0.25, more preferably Y2 > 0.30, and even more preferably Y2 > 0.35. When Y2 > 0.25, compatibility with other resins is improved. Organic groups containing polymerizable functional groups are easily hydrolyzed and removed by water, which can lead to a high water absorption rate. Therefore, it is preferable to use a method that is less affected by moisture. On the other hand, in environments affected by moisture, if Y2 is large, the cured product tends to become brittle due to moisture, so Y2 < 0.4 is preferable, Y2 < 0.3 is more preferable, and Y2 < 0.2 is even more preferable. It is also preferable for Y2 to be 0. Y2 represents a relative value to M1 + M2 + D1 + D2 + T1 + T2 + Q = 1.

[0087] <Coefficient M1> R containing polymerizable functional groups ６ M units that do not have are not essential constituent elements in organopolysiloxanes, but may be included. Therefore, R ６ M1, which is the proportion in M ​​units that does not contain, may be M1 > 0, and by substituting either the alkoxy group or the silanol group of the organopolysiloxane in M ​​units, the storage stability of the organopolysiloxane tends to be improved and the viscosity can be reduced. From the viewpoint of storage stability, the coefficient M1 is preferably 0.09 or more, usually 0.6 or less, preferably 0.5 or less, and more preferably 0.4 or less.

[0088] <Coefficient D1> R containing polymerizable functional groups ６ While D units that do not possess are not essential constituent elements in organopolysiloxanes, including such units tends to impart toughness to the cured product. That is, from the viewpoint of imparting toughness to the cured product, D1 ≥ 0.2 is preferable, D1 ≥ 0.3 is more preferable, and D1 ≥ 0.4 is even more preferable. On the other hand, R ６If the content of the D unit without [a certain group] is too high, the heat resistance of the cured product tends to decrease. That is, from the perspective of suppressing the decrease in the heat resistance of the cured product, it is preferable that D1 ≤ 0.5, more preferably D1 ≤ 0.4, and even more preferably D1 ≤ 0.3.

[0089] <Coefficient T1> The R containing a polymerizable functional group ６ The T unit without [a certain group] is not an essential constituent in organopolysiloxane, but by including such a unit, the compatibility with other components added to the organopolysiloxane-containing composition described later tends to be improved. From the perspective of improving the compatibility with other components, it is preferable that T1 ≥ 0.2, and more preferably T1 ≥ 0.3. On the other hand, the R ６ If the content of the T unit without [a certain group] is too high, curing defects are likely to occur due to the steric hindrance of the introduced organic groups. From the perspective of curability, it is preferable that T1 ≤ 0.5, more preferably T1 ≤ 0.4, and even more preferably T1 ≤ 0.3.

[0090] From the above, each coefficient in the above formula [1] is preferably 0 < Q ≤ 0.65, 0 < M2 + D2 + T2 ≤ 0.75, 0.02 ≤ Y1 ≤ 0.25, Y2 < 0.4, 0 < M1 ≤ 0.6, D1 ≤ 0.7, T1 ≤ 0.5, more preferably 0.04 ≤ Q ≤ 0.60, 0.10 ≤ M2 + D2 + T2 ≤ 0.75, 0.025 ≤ Y1 ≤ 0.20, Y2 < 0.3, 0.09 ≤ M1 ≤ 0.5, D1 ≤ 0.6, T1 ≤ 0.4, and even more preferably 0.04 ≤ Q ≤ 0.45, 0.12 ≤ M2 + D2 + T2 ≤ 0.6, 0.03 ≤ Y1 ≤ 0.15, Y2 < 0.2, 0.09 ≤ M1 ≤ 0.4, D1 ≤ 0.3, T1 ≤ 0.3.

[0091] In the organopolysiloxane represented by formula [1], each unit constituting the M unit, D unit, and T unit does not have to be the same. For example, among the units with a proportion of M1 (R １ R ２ R ３ SiO １／２ ), for example, a certain R １ is a hydrogen atom, and a certain R １It may have different structures, such as a methyl group. This is common to other R and X.

[0092] <R １ ~R ５ 、R ７ ~R １１ > R １ ~R ５ 、R ７ ~R １１ Each R is independently one or more groups selected from the group consisting of an organic group and a hydrogen atom. １ ~R ５ 、R ７ ~R １１ When R is an organic group, it is preferably an organic group having 1 to 20 carbon atoms. Specifically, it is preferably a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms, or an aromatic ring group having 6 to 20 carbon atoms. More specifically, it is preferably an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an octyl group, a cyclohexyl group, or a polyether group such as a polyalkylene glycol group. Particularly preferably, it is a methyl group.

[0093] It is also preferable that the organopolysiloxane is represented by the following formula [2]. (R １ R ２ R ３ SiO １／２ ) Ｍ１ (R ４ R ５ R ６ SiO １／２ ) Ｍ２ (R ７ R<000012​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Ｙ１ (O １／２ R ６ ) Ｙ２ ...[2]

[0094] In general formula [2], the coefficients M1, M2, D1, D2, T1, T2, and Q represent the proportions (based on moles) of each structure when M1 + M2 + D1 + D2 + T1 + T2 + Q = 1. Also, in general formula [2], the coefficients Y1 and Y2 represent the proportions (based on moles) of each structure when M1 + M2 + D1 + D2 + T1 + T2 + Q = 1. １／２ R １１ ) and (O １／２ R ６ This indicates the relative content (based on moles) of ).

[0095] The organopolysiloxane having polymerizable alkenyl groups represented by formula [2] is an organopolysiloxane where 0 < Q. That is, it is characterized by having Q units. By having Q units, the heat resistance of the cured organopolysiloxane can be improved. Except for Q = 0, the possible ranges of the coefficients M1, M2, D1, D2, T1, T2, and Q, including preferred combinations, are as described in formula [1] above. The structural units represented by each coefficient are also as described in formula [1] above.

[0096] The organopolysiloxane may also be represented by the following formula [3]. (R １ R ２ R ３ SiO １／２ ) Ｍ１ (R ４ R ５ R ６ SiO １／２ ) Ｍ２ (R ７ R ８ SiO ２／２ ) Ｄ１ (R ９ R ６ SiO ２／２ ) Ｄ２ (R １０ SiO ３／２ ) Ｔ１ (R ６ SiO ３／２ ) Ｔ２ (O １／２ R１１ ) Ｙ１ (O １／２ R ６ ) Ｙ２ ...[3]

[0097] In the above formula [3], R １ ~R ５ , R ７ ~R １１ Each of these is independently selected from the group consisting of organic groups and hydrogen atoms, one or more of these groups. １ ~R ３ , R ７ , R ８ , R １０ and R １１ It does not contain polymerizable functional groups. ６ is one or more organic groups containing polymerizable functional groups, and if there are multiple, they may be the same or different from each other, 0 ≤ M1, 0 ≤ D1, 0 ≤ T1, 0 ≤ Y1, 0 ≤ Y2, 0 < D1 + D2 + T1 + T2, 0 < M2 + D2 + T2, and M1 + M2 + D1 + D2 + T1 + T2 = 1.

[0098] Equation [3] represents an organopolysiloxane in which the coefficient Q in Equation [1] is 0, that is, an organopolysiloxane that does not contain Q units. R in Equation [3] １ ~R １１ The formula is the same as in formula [1], and the preferred group is also the same. M1, M2, D1, D2, T1, T2, Y1, Y2 are also the same as in formula [1], and the preferred numerical ranges for each coefficient are also the same.

[0099] <D1+D2+T1+T2> In the organopolysiloxane represented by formula [3], if 0 < D1+D2+T1+T2, it is possible to introduce constituent units other than M units into the organopolysiloxane, which is advantageous from the viewpoint of curability and heat resistance after curing. D1+D2+T1+T2 is preferably 0.01 < D1+D2+T1+T2, more preferably 0.1 < D1+D2+T1+T2, and even more preferably 0.2 < D1+D2+T1+T. There is no particular upper limit, and by definition it is 1 or less. From the viewpoint of introducing flexible parts into the organopolysiloxane and improving the crack resistance of the cured product, it is preferable that 0 < D1+D2. D1+D2≧0.05 is more preferable, and D1+D2≧0.1 is even more preferable. Furthermore, from the viewpoint of suppressing thermal expansion of the cured organopolysiloxane, D1 + D2 ≤ 0.9 is preferred, and D1 + D2 ≤ 0.8 is more preferred.

[0100] From the viewpoint of improving the heat resistance of the cured organopolysiloxane, it is preferable that 0 < T1 + T2. More preferably, T1 + T2 ≥ 0.05, and even more preferably, T1 + T2 ≥ 0.1. From the viewpoint of suppressing curing shrinkage of the cured organopolysiloxane, it is preferable that T1 + T2 ≤ 0.9, and more preferably, T1 + T2 ≤ 0.8. In other words, from the viewpoint of achieving both crack resistance and heat resistance of the cured organopolysiloxane, it is preferable that 0 < D1 + D2 and 0 < T1 + T2.

[0101] Therefore, it is preferable that each ratio in the above formula [3] is 0 < M2 + D2 + T2 ≤ 0.9, 0.02 ≤ Y1 ≤ 0.25, Y2 < 0.4, 0 < M1 ≤ 0.6, D1 ≤ 0.5, T1 ≤ 0.5, more preferably 0.10 ≤ M2 + D2 + T2 ≤ 0.8, 0.025 ≤ Y1 ≤ 0.20, Y2 < 0.3, 0.09 ≤ M1 ≤ 0.5, D1 ≤ 0.4, T1 ≤ 0.4, and even more preferably 0.12 ≤ M2 + D2 + T2 ≤ 0.6, 0.03 ≤ Y1 ≤ 0.15, Y2 < 0.2, 0.09 ≤ M1 ≤ 0.4, D1 ≤ 0.3, T1 ≤ 0.3.

[0102] The second core portion and / or second cladding portion of the second optical waveguide portion can be formed, for example, by curing the organopolysiloxane-containing composition described above. Furthermore, in order to suppress an increase in the refractive index of the cured product, it is also preferable to use an organopolysiloxane that does not contain aromatic structures.

[0103] (Method for producing organopolysiloxanes) The method for producing organopolysiloxanes is not particularly limited as long as the organopolysiloxanes represented by formulas [1], [2], and [3] can be obtained. For example, any of the following methods may be used: a method of condensing disiloxane compounds, disilazane compounds and their hydrolysates, alkoxysilane compounds and their hydrolysates, or partially hydrolyzed condensates, either individually or in combination with others; a method of condensing chlorosilane compounds and their hydrolysates, or partially hydrolyzed condensates; a method of ring-opening polymerization of cyclic siloxane compounds; or chain polymerization including anionic polymerization. Multiple methods may also be used in combination. Furthermore, there are no particular limitations on the method for introducing polymerizable functional groups. Any method may be used, such as condensing one type of alkoxysilane compound, disiloxane compound, disilazane compound, or their hydrolysates or partially hydrolyzed condensates, or a method of converting reactive organic groups introduced into organopolysiloxanes into polymerizable functional groups by chemical means. These methods may also be used in combination. Below are some examples of raw materials that can be used in the production of organopolysiloxanes by hydrolysis condensation.

[0104] <M Unit Source> Examples of M unit sources include trimethylsilanol, trimethylmethoxysilane, hexamethyldisiloxane, hexamethyldisilazane, dimethylsilanol, dimethylmethoxysilane, tetramethyldisiloxane, tetramethyldisilazane, dimethylvinylsilanol, dimethylvinylmethoxysilane, 1,3-divinyltetramethyldisiloxane, 1,3-divinyltetramethyldisilazane, 3-(meth)acryloyloxypropyldimethylsilanol, 3-(meth)acryloyloxypropyldimethylmethoxysilane, 1,3-bis((meth)acryloyloxypropyl)-1,1,3,3-tetramethyldisiloxane, methoxytriphenylsilane, triphenylsilanol, 1,3-diphenyl Tramethyldisiloxane, 1,3-diphenyltetramethyldisilazane, dimethylphenylsilanol, dimethylmethoxyphenylsilane, 1,4-bis(dimethylmethoxysilyl)benzene, 1,4-bis(dimethylethoxysilyl)benzene, 2-(3,4-epoxycyclohexyl)ethyldimethylmethoxysilane, 2-(3,4-epoxycyclohexyl)ethyldimethylethoxysilane, 3-glycidoxypropyldimethylmethoxysilane, 3-glycidoxypropyldimethylethoxysilane, and, among the compounds listed above, those containing a silanol hydroxyl group or an alkoxy group, in which a halogen is bonded instead of the silanol hydroxyl group or alkoxy group, can be used. Hexamethyldisiloxane can be particularly preferred as the M unit source.

[0105] <D Unit Source> Examples of D unit sources include dimethyldisilanol, dimethyldimethoxysilane, tetramethyldisiloxane, dimethylsiloxane oligomer, 3-(meth)acryloyloxypropyldimethoxymethylsilane, methyldimethoxyphenylsilane, diethoxymethylphenylsilane, methylphenyldisilanol, 1,4-bis(methyldimethoxysilyl)benzene, 1,4-bis(methyldiethoxysilyl)benzene, 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and compounds in which halogens are bonded instead of the silanol hydroxyl group or alkoxy group of the listed compounds, as well as polymers thereof. Dimethyldimethoxysilane can be used particularly favorably.

[0106] <T Unit Source> Examples of T unit sources include C such as trimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, hexyltrimethoxysilane, and decyltrimethoxysilane. １ ~C ２０Examples of modified long-chain alkoxy groups include trimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 8-(meth)acryloyloxyoctyltrimethoxysilane, 1,4-bis(trimethoxysilyl)benzene, p-styryltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, and 3-glycidoxypropyltrimethoxysilane. In addition to these methoxysilane compounds, alkoxysilane compounds such as ethoxysilane, silanol compounds, chlorosilane compounds, hydrosilylsilane compounds, and polymers thereof can also be used. In particular, 3-methacryloyloxypropyltrimethoxysilane, 8-methacryloyloxyoctyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 8-acryloyloxyoctyltrimethoxysilane, and decyltrimethoxysilane can be suitably used.

[0107] <Q Unit Sources> Examples of Q unit sources include tetrachlorosilane, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetrapentyloxysilane, tetraphenyloxysilane, trimethoxymonoethoxysilane, dimethoxydiethoxysilane, triethoxymonomethoxysilane, trimethoxymonopropoxysilane, monomethoxytributoxysilane, monomethoxytripentyloxysilane, monomethoxytriphenyloxysilane, dimethoxydipropoxysilane, tripropoxymonomethoxysilane, trimethoxymonobutoxysilane, dimethoxydibutoxysilane, triethoxymonopropoxysilane, diethoxydipropoxysilane, tripropoxymonopropoxysilane, dimethoxymonoethoxymonobutoxy Alkoxysilanes such as sisilane, diethoxymonomethoxymonoboxysilane, diethoxymonopropoxymonoboxysilane, dipropoxymonomethoxymonoethoxysilane, dipropoxymonomethoxymonoboxysilane, dipropoxymonoethoxymonoboxysilane, dipropoxymonomethoxymonoboxysilane, dipropoxymonoethoxymonoboxysilane, dibutoxymonomethoxymonoethoxysilane, dibutoxymonoethoxymonoboxysilane, monomethoxymonoethoxymonoboxysilane, or aryloxysilanes and tetramethoxysilane oligomers such as methyl silicate MS51, MS56, MS57, MS60 manufactured by Mitsubishi Chemical Corporation, and ethyl silicate oligomers ES40, ES48 manufactured by Tama Chemical Industry Co., Ltd. can be used as tetraethoxysilane oligomers, with methyl silicate MS51 being particularly preferred. One or more of the above M, D, T, and Q unit sources can be used in combination.

[0108] As catalysts for hydrolysis and condensation of these silicon raw materials, acid catalysts, base catalysts, or inorganic salts can be used, with acid catalysts being particularly preferred. Examples of acid catalysts include hydrochloric acid, sulfuric acid, trifluoroacetic acid, acetic acid, methacrylic acid, and acrylic acid, with hydrochloric acid being particularly preferred. Examples of base catalysts include ammonia, hexamethyldisilazane, triethylamine, tetraethylammonium hydroxide, diazabicycloundecene, potassium hydroxide, sodium hydroxide, barium hydroxide, potassium carbonate, and sodium carbonate, with potassium hydroxide being particularly preferred. As inorganic salts, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium bromide, potassium bromide, magnesium bromide, and calcium bromide can be used, with sodium chloride being particularly preferred.

[0109] Examples of solvents used in the hydrolysis condensation reaction include tetrahydrofuran, toluene, methanol, ethanol, isopropanol, hexane, and heptane. Tetrahydrofuran is particularly preferred, and two or more solvents may be used depending on the solubility of the product. A mixture of toluene and methanol, or a mixture of tetrahydrofuran and methanol, is particularly preferred.

[0110] Alkoxy and silanol groups that remain after hydrolysis condensation may be substituted with organic acids or alcohols as needed. Examples of organic acids include acetic acid, acrylic acid, and methacrylic acid. Examples of alcohols that do not contain polymerizable alkenyl groups include methanol, ethanol, propanol, butyl alcohol, pentanol, hexanol, heptanol, and their structural isomers. Examples of alcohols that contain polymerizable alkenyl groups include 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. From the viewpoint of stability, 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate are preferred.

[0111] If the organopolysiloxane has a rigid structure such as a perfectly caged silsesquioxane, the cured product will be hard and brittle; therefore, it is preferable that it does not have a perfectly caged structure. It does not need to be a perfectly caged silsesquioxane; for example, it may include a random structure or a ladder structure as a higher-order structure, as long as it does not impair the effects of the present invention.

[0112] <Water> The amount of water used for hydrolysis is preferably 0.5 equivalents or more, more preferably 0.8 equivalents or more, and even more preferably 1.1 equivalents or more, relative to the total amount of alkoxy groups contained in the MDTQ unit source. The water is not particularly limited and may be water contained in commercially available hydrochloric acid, or water purified by distillation or ion exchange resin may be used.

[0113] (Organopolysiloxane-containing composition) The organopolysiloxane-containing composition in the present invention (also referred to as organopolysiloxane-containing composition) is used for forming optical waveguides. The composition is preferably a photocurable organopolysiloxane-containing composition, preferably an organopolysiloxane-containing composition having polymerizable functional groups as described above, and more preferably an organopolysiloxane-containing composition having polymerizable alkenyl groups. In addition to the organopolysiloxane described above, the composition may contain monofunctional polymerizable alkenyl compounds, polyfunctional polymerizable alkenyl compounds, and / or alkenyl polymers, etc., to the extent that they do not impair the properties of the cured product obtained from the composition, as described later.

[0114] Furthermore, the composition may contain a polymerization initiator to polymerize and cure the organopolysiloxane and polymerizable alkenyl compound. Although it is possible to cure the organopolysiloxane or organopolysiloxane-containing composition by electron beam irradiation or the like without using a polymerization initiator, a large amount of energy is required for curing. Therefore, in addition to the organopolysiloxane described above, a preferred embodiment of the organopolysiloxane-containing composition in the present invention is one that contains at least a polymerization initiator. In addition, other components such as sensitizers, chain transfer agents, antioxidants, ultraviolet absorbers, light stabilizers, leveling agents, rheology modifiers, adhesion aids such as silane coupling agents, dyes, defoamers, other components, and solvents may be included in a manner that does not impair the properties of the cured product obtained from the composition, as described below. The following describes components that may be included in the organopolysiloxane-containing composition.

[0115] <Monofunctional Polymerizable Alkenyl Compounds> Specific examples of monofunctional polymerizable alkenyl compounds include (meth)acrylates containing carboxyl groups such as (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxyethyl phthalate, and 2-(meth)acryloyloxyethyl hexahydrophthalate; and (meth)acrylates having hydroxyl groups such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. Alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, etc. (meth)acrylates containing alicyclic structures such as cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, 2-dicyclopentenoxyethyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, and 4-tert-butylcyclohexyl (meth)acrylate;(Meth)acrylates containing aromatic ring structures such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, phenoxypolypropylene glycol (meth)acrylate, phenylphenyl (meth)acrylate, phenylphenoxyethyl (meth)acrylate, phenoxybenzyl (meth)acrylate, phenylbenzyl (meth)acrylate, naphthyl (meth)acrylate, (1-naphthyl)methyl (meth)acrylate; (meth)acrylates containing heterocyclic structures such as tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, (meth)acryloylmorpholine; alkoxy (meth)acrylates such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and butoxyethyl (meth)acrylate; Examples include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 2-(meth)acryloyloxyethyl acid phosphate, trifluoroethyl (meth)acrylate and heptadecafluorodecyl (meth)acrylate, 2-(meth)acryloyloxyethyl isocyanate; styrene derivatives such as styrene, α-methylstyrene, 2-vinylpyridine, 4-vinylpyridine, 1,1-diphenylethylene and their aromatic ring hydrogen-substituted derivatives; vinyl compounds such as vinyl acetate, vinyl octanoate, vinyl decanoate, vinyl hexanoate, acrylonitrile, and vinyl benzoate. It is preferable to use materials that do not contain aromatic structures, as this would increase the refractive index of the cured product.

[0116] <Polyfunctional Polymerizable Alkenyl Compounds> Specific examples of polyfunctional polymerizable alkenyl compounds include alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylate; and polyalkylene glycol di(meth)acrylates such as polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polybutylene glycol di(meth)acrylate. Di(meth)acrylates containing alicyclic structures such as cyclohexanedimethanol di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, ethoxylated hydrogenated bisphenol A di(meth)acrylate, propoxylated hydrogenated bisphenol A di(meth)acrylate, and adamantanediol di(meth)acrylate; difunctional (meth)acrylates such as polycarbonate diol di(meth)acrylate, polyester diol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, propoxylated bisphenol A di(meth)acrylate, 9,9-bis(4-acryloyloxyethoxyphenyl)fluorene, and polyurethane di(meth)acrylate; Examples include trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate, ethoxylated isocyanurate tri(meth)acrylate, and ε-caprolactone-modified tris((meth)acrooxyethyl) isocyanurate; tetrafunctional (meth)acrylates such as ditrimethylolpropane tetra(meth)acrylate; pentafunctional (meth)acrylates such as dipentaerythritol penta(meth)acrylate; and polyfunctional monomers such as hexafunctional (meth)acrylates such as dipentaerythritol hexa(meth)acrylate; as well as 1,4-divinylbenzene and 1,3-divinylbenzene. It is preferable to use materials that do not contain aromatic structures because the refractive index of the cured product will be high.

[0117] <Alkenyl Polymers> Alkenyl polymers are polymers containing 50% by mass or more of alkenyl monomer units in their composition. In this specification, "unit" means a repeating unit that constitutes a polymer. Alkenyl polymers may be monofunctional or polyfunctional. Furthermore, it is preferable to use those that do not contain aromatic structures because the refractive index of the cured product becomes high and the cured product becomes brittle. The alkenyl monomer units contained in the alkenyl polymer may be one type or two or more types. The polymerization method for obtaining alkenyl polymers is not particularly limited and can be polymerized by known methods such as solution polymerization, suspension polymerization, emulsion polymerization, and partial polymerization. In the present invention, suspension polymerization is preferred because it is relatively easy to control the polymerization reaction and separate the resulting polymer.

[0118] As the alkenyl polymer, a modified version may be used, which has been chemically modified to introduce a functional group containing a double bond, such as a (meth)acryloyl group or a vinyl group, into the side chain. As chemical modification methods, for example, the reaction of a carboxyl group with a glycidyl group or the reaction of a hydroxyl group with an isocyanate group can be used. When using the reaction of a carboxyl group with a glycidyl group as the chemical modification method, for example, an alkenyl polymer containing an alkenyl monomer unit having a carboxyl group can be produced, and the obtained alkenyl polymer can be reacted with a compound having a glycidyl group and a double bond, such as glycidyl (meth)acrylate.

[0119] In the reaction between an alkenyl polymer containing alkenyl monomer units having a carboxyl group and a compound having a glycidyl group and a double bond, it is preferable to use a reaction catalyst to shorten the reaction time. Examples of reaction catalysts include quaternary ammonium salts such as tetrabutylammonium bromide, quaternary phosphonium salts such as ethyltriphenylphosphonium bromide, and phosphine compounds such as triphenylphosphine. Quaternary ammonium salts are particularly preferred because the organopolysiloxane-containing composition of this embodiment is less likely to discolor.

[0120] The weight-average molecular weight (Mw) of the alkenyl polymer is preferably 5,000 to 500,000, and more preferably 10,000 to 200,000. When the weight-average molecular weight is 5,000 or more, the strength of the cured product is good. When it is 500,000 or less, the viscosity of the organopolysiloxane-containing composition of this embodiment decreases, resulting in good workability.

[0121] <Polymerization Initiators> Examples of polymerization initiators include photopolymerization initiators, thermal polymerization initiators, and peroxides used in redox polymerization. The type of polymerization initiator can be appropriately selected depending on the polymerization method.

[0122] <Photopolymerization Initiators> Photopolymerization initiators are radical polymerization initiators used in photopolymerization. Specific examples of photopolymerization initiators include benzophenone-type compounds such as benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, methyl 2-benzoylbenzoate, and 4-phenylbenzophenone; anthraquinone-type compounds such as tert-butylanthraquinone and 2-ethylanthraquinone; 2-hydroxy-2-methyl-1-phenylpropan-1-one, oligo{2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone}, benzyldimethyl ketal, 1-hydroxycyclohexylphenyl ketone, benzoin methyl ether, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propanone, and 2-hydroxy-1-{4-[4 Examples include alkylphenone-type compounds such as -(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one; thioxanthone-type compounds such as 2-benzyl-2-dimethylamino-4'-morpholinobylophenone, diethylthioxanthone, and isopropylthioxanthone; acylphosphine oxide-type compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; and phenylglyoxylate-type compounds such as phenylglyoxylic acid methyl esters.

[0123] Among these, alkylphenone-type compounds are preferred in that they can suppress discoloration of the cured product, and 2-hydroxy-2-methyl-1-phenylpropan-1-one and 1-hydroxycyclohexylphenyl ketone are more preferred. Furthermore, acylphosphine oxide-type compounds are preferred in that they facilitate sufficient curing to the interior of the cured product, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide is more preferred in that it can suppress discoloration of the cured product. Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, which has higher sensitivity to longer wavelength light, is even more preferred. 2-benzyl-2-dimethylamino-4'-morpholinobutyrophenone is also preferred from the viewpoint of high reactivity to light around 365 nm. These photopolymerization initiators may be used individually or in combination of two or more.

[0124] When curing the organopolysiloxane-containing composition of the present invention by photopolymerization to obtain a cured product, the wavelength of light irradiated onto the organopolysiloxane-containing composition is not particularly limited, but it is preferable to irradiate it with ultraviolet light having a wavelength of 200 to 500 nm. Specific examples of ultraviolet light sources include ultra-high pressure mercury lamps, high-pressure mercury lamps, metal halide lamps, high-power metal halide lamps, UV-LED lamps, chemical lamps, and black lights. After photopolymerization of the organopolysiloxane-containing composition, after-curing may be performed. By performing after-curing, the amount of unreacted polymerizable alkenyl groups remaining in the cured product can be reduced, and the strength of the cured product can be further increased. The conditions for after-curing are preferably 70 to 200°C for 0.01 to 24 hours, and more preferably 80 to 180°C for 0.1 to 10 hours.

[0125] <Thermal Polymerization Initiators> Thermal polymerization initiators are radical polymerization initiators used in thermal polymerization. Examples of thermal polymerization initiators include organic peroxides and azo compounds. Specific examples of organic peroxides include ketone peroxides such as methyl ethyl ketone peroxide; peroxyketals such as 1,1-di(tert-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-hexylperoxy)cyclohexane, and 1,1-di(tert-butylperoxy)cyclohexane; hydroperoxides such as 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, and p-menthane hydroperoxide; and dicumyl peroxide and di-tert-butyl peroxide. Examples include dialkyl peroxides; diacyl peroxides such as dilauroyl peroxide and dibenzoyl peroxide; peroxydicarbonates such as di(4-tert-butylcyclohexyl) peroxydicarbonate and di(2-ethylhexyl) peroxydicarbonate; and peroxyesters such as tert-butyl peroxy-2-ethylhexanoate, tert-hexyl peroxyisopropyl monocarbonate, tert-butyl peroxybenzoate, and 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate.

[0126] Specific examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 1,1'-azobis-1-cyclohexanecarbonitrate, dimethyl-2,2'-azobisisobutyrate, 4,4'-azobis-4-cyanovaleric acid, and 2,2'-azobis-(2-amidinopropane)dihydrochloride.

[0127] These thermal polymerization initiators may be used individually or in combination of two or more. Organic peroxides are preferred as thermal polymerization initiators because they are less likely to cause bubbles in the cured product. Considering the balance between the curing time and pot life of the organopolysiloxane-containing composition, the 10-hour half-life temperature of the organic peroxide is preferably 35 to 80°C, more preferably 40 to 75°C, and even more preferably 45 to 70°C. If the 10-hour half-life temperature is 35°C or higher, the organopolysiloxane-containing composition is less likely to gel at room temperature, resulting in a good pot life. On the other hand, if the 10-hour half-life temperature is 80°C or lower, the curing time of the organopolysiloxane-containing composition can be shortened.

[0128] Examples of such organic peroxides include 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, tert-butylperoxy-2-ethylhexanoate, and di(4-tert-butylcyclohexyl)peroxydicarbonate. A commercially available example of 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate is Perocta-O (trade name, manufactured by NOF Corporation, 10-hour half-life temperature: 65.3°C). A commercially available example of tert-butylperoxy-2-ethylhexanoate is Perbutyl-O (trade name, manufactured by NOF Corporation, 10-hour half-life temperature: 72.1°C). A commercially available example of di(4-tert-butylcyclohexyl)peroxydicarbonate is PerloylTCP (trade name, manufactured by NOF Corporation, 10-hour half-life temperature: 40.8°C).

[0129] When curing an organopolysiloxane-containing composition by thermal polymerization to obtain a cured product, the curing conditions are not particularly limited, but from the viewpoint of obtaining an optical component resin with suppressed discoloration, the curing temperature is preferably 40 to 200°C, and more preferably 60 to 150°C. The curing time (heating time) also varies depending on the curing temperature, but is preferably 1 to 120 minutes, and more preferably 1 to 60 minutes. After thermal polymerization of the organopolysiloxane-containing composition, it is preferable to perform an after-curing. The conditions for after-curing are preferably 50 to 200°C for 0.1 to 10 hours, and more preferably 70 to 180°C for 0.2 to 5 hours.

[0130] <Redox Polymerization> Redox polymerization typically uses redox polymerization initiators. Redox polymerization initiators are polymerization initiators that use a peroxide and a reducing agent in combination. Examples of peroxides used in redox polymerization include dibenzoyl peroxide and hydroperoxide. These peroxides may be used individually or in combination of two or more. When the above-mentioned peroxides are used as redox polymerization initiators, examples of combinations with reducing agents are as follows: (1) A combination of dibenzoyl peroxide (peroxide) and aromatic tertiary amines such as N,N-dimethylaniline, N,N-dimethyl-p-toluidine, and N,N-bis(2-hydroxypropyl)-p-toluidine (reducing agents). (2) A combination of hydroperoxide (peroxide) and metal soaps (reducing agents). (3) A combination of hydroperoxide (peroxide) and thioureas (reducing agents).

[0131] When curing an organopolysiloxane-containing composition by redox polymerization to obtain a cured product, curing can be performed at room temperature of 5 to 40°C by using a redox polymerization initiator. A curing temperature of 15 to 40°C is preferred because it can reduce the amount of unreacted (meth)acryloyl groups remaining in the resulting cured product and further increase the strength of the cured product. A method of curing is preferred in which a reducing agent is dissolved in the organopolysiloxane-containing composition beforehand, and then a peroxide is added, because the organopolysiloxane-containing composition is less likely to gel and can be handled stably. When curing an organopolysiloxane-containing composition, it is preferable to cure it in a sealed state in order to suppress curing inhibition by oxygen. Methods of sealing include sandwiching the organopolysiloxane-containing composition between glass or PET film. Alternatively, curing may be performed under an inert gas atmosphere.

[0132] <Chain Transfer Agents> When curing reactions of organopolysiloxane-containing compositions are carried out in air, oxygen traps active radicals as peroxide radicals, inhibiting polymerization. However, by adding hydrogen-donating chain transfer agents, polymerization inhibition by oxygen can be suppressed. Examples of thiol compounds used as the above-mentioned chain transfer agents include methyl mercaptoacetate, methyl 3-mercaptopropionate, 2-ethylhexyl 3-mercaptopropionate, 3-methoxybutyl 3-mercaptopropionate, n-octyl 3-mercaptopropionate, stearyl 3-mercaptopropionate, 1,4-bis(3-mercaptopropionyloxy)butane, 1,4-bis(3-mercaptobutyryloxy)butane, and trimethylolethanetris(3-mercaptopropionate (3-mercaptobutyrate), trimethylolethanetris(3-mercaptopropionate), trimethylolpropanetris(3-mercaptopropionate), trimethylolpropanetris(3-mercaptobutyrate), pentaerythritoltetrakis(3-mercaptopropionate), pentaerythritoltetrakis(3-mercaptopropionate), dipentaerythritolhexakis(3-mercaptopropionate), dipentaerythritolhexakis(3-mercaptobutyrate), Mercaptocarboxylic acid esters such as tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate and tris[2-(3-mercaptobutyryloxy)ethyl]isocyanurate; alkylthiols such as ethanethiol, 2-methylpropane-2-thiol, n-dodecanethiol, 2,3,3,4,4,5-hexamethylhexane-2-thiol (tert-dodecanethiol), ethane-1,2-dithiol, propane-1,3-dithiol, and benzylthiol. Examples include aromatic thiols such as benzenethiol, 3-methylbenzenethiol, 4-methylbenzenethiol, naphthalene-2-thiol, pyridine-2-thiol, benzimidazole-2-thiol, and benzothiazole-2-thiol; mercaptoalcohols such as 2-mercaptoethanol and 4-mercapto-1-butanol; and silane-containing thiols such as 3-(trimethoxysilyl)propane-1-thiol and 3-(triethoxysilyl)propane-1-thiol.When adding a chain transfer agent, it may be used alone or in a mixture of two or more types. The amount added is 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the total amount of polymerizable components. When using a mixture of two or more types, the total amount of chain transfer agents will be within the above range.

[0133] <Solvent> A solvent may be included for the purpose of diluting the organopolysiloxane-containing composition. The type of solvent is not particularly limited as long as it does not impair the physical properties required for the cured product of the organopolysiloxane-containing composition, but good solubility is desirable. Aromatic hydrocarbons (e.g., toluene, xylene, ethyl benzoate, ethylbenzene, benzyl alcohol), ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, diacetone alcohol), esters (e.g., methyl acetate, ethyl acetate, butyl acetate, sec-butyl acetate, methoxybutyl acetate, amyl acetate, n-propyl acetate, ethyl lactate, methyl lactate, butyl lactate, propylene glycol monomethyl ether acetate, γ-butyrolactone), ethers (e.g. Alternatively, isopropyl ether, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monobutyl ether, 1,4-dioxane, methyl tert-butyl ether, tetrahydrofuran), alcohols (e.g., methanol, ethanol, n-propanol, isopropanol, butanol, sec-butanol, tert-butanol, n-pentanol), halogenated solvents (e.g., methylene chloride, trichloroethylene, tetrachloroethylene, bromopropane, chloroform), and others (e.g., dimethyl sulfoxide, N,N-dimethylformamide, water) may be used, and two or more solvents may be used.

[0134] The amount of the solvent in the organopolysiloxane-containing composition is not particularly limited as long as it does not impair the physical properties required for the cured product of the organopolysiloxane-containing composition. However, if it is desirable to reduce viscosity while keeping the volatile content low, the amount is preferably more than 0% by mass and 25% by mass or less of the total organopolysiloxane-containing composition. Furthermore, when obtaining a cured thin film, the amount is preferably 75% by mass or more and less than 100% by mass of the total composition.

[0135] <Antioxidants> It is preferable that the organopolysiloxane-containing composition further contains antioxidants. By containing antioxidants in the organopolysiloxane-containing composition, discoloration due to heat, such as heating during soldering of cured products or heat generation of devices, can be suppressed. Specific examples of antioxidants include 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, tetrakis-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane, triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], etc. Examples of antioxidants include: ol-based antioxidants; phosphorus-based antioxidants such as triphenyl phosphite, trisisodecyl phosphite, tristridecyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, and tetra(C12-15 alkyl)-4,4'-isopropylidenediphenyl diphosphite; and sulfur-based antioxidants such as dilauryl-3,3'-thiodipropionate, ditridecyl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, disteryl-3,3'-thiodipropionate, and pentaerythritol tetrakis(β-laurylthiopropionate). These antioxidants may be used individually or in combination of two or more.

[0136] <Other Components> The organopolysiloxane-containing composition of the present invention may also contain other components such as fillers, curing control agents, and viscosity modifiers. These components can be included as appropriate, within a range that does not affect the transmission loss, heat resistance, and refractive index of the cured product.

[0137] (Cured product of organopolysiloxane-containing composition) The cured product obtained by curing the organopolysiloxane-containing composition described above with heat or light is not particularly limited, and can be cured using conditions that are used for curing silicone resin, depending on the type of polymerization initiator, etc.

[0138] <Refractive Index of Cured Product> The refractive index of the cured product can be controlled by changing the proportion of constituent units of the organopolysiloxane. For example, by increasing the value of M2 + D2 + T2 in formulas [1], [2], or [3] above, that is, by increasing the content of polymerizable functional groups, the density of the resulting cured product can be increased, and the refractive index can be increased. Conversely, by decreasing the value of M2 + D2 + T2, that is, by decreasing the content of polymerizable functional groups, the density of the resulting cured product can be decreased, and the refractive index can be decreased. The refractive index of the cured product can also be controlled by changing the component proportions of the organopolysiloxane-containing composition.

[0139] (Manufacturing Method for Optical Waveguide Elements) The manufacturing method for the optical waveguide elements is not particularly limited, and various conventionally known methods can be used. For example, a method of manufacturing by directly laminating a first optical waveguide portion 100 and a second optical waveguide portion 110 formed on separate members, or via an adhesive layer; a method of manufacturing by directly laminating a member on which the first optical waveguide portion 100 is formed with an optical waveguide sheet described later, or via an adhesive layer; and a method of manufacturing by directly forming a second optical waveguide on the first optical waveguide portion 100. Specifically, the second optical waveguide portion 110 can be formed by mirror projection exposure, proximity exposure, laser lithography, a method using a semiconductor exposure apparatus (stepper), a replication (stamper) method, a direct exposure method, a reactive ion etching (RIE) method, a method based on injection molding, a photobleaching method, a direct writing method, a self-forming method, an optical imprint method, etc.

[0140] (Optical Waveguide Sheet) An optical waveguide sheet according to one embodiment of the present invention (hereinafter also referred to as "this optical waveguide sheet") is an optical waveguide sheet comprising a second optical waveguide portion having a structure that allows for adiabatic coupling with the first optical waveguide portion 1 provided in the optical waveguide portion, wherein the second optical waveguide portion comprises a second core portion and a second cladding portion, the refractive indices of the core portion and the cladding portion of the optical waveguide portion 1 at a wavelength of 1300 nm are different, the refractive indices of the second core portion and the second cladding portion at a wavelength of 1300 nm are different, the refractive index of the second core portion at a wavelength of 1300 nm is 0.01 or greater than the refractive index of the cladding portion of the optical waveguide portion 1 at a wavelength of 1300 nm, and the absolute value of the refractive index difference between the second cladding portion and the cladding portion of the optical waveguide portion 1 at a wavelength of 1300 nm is 0.05 or less, and the optical waveguide sheet has the second cladding portion.

[0141] In this optical waveguide sheet, the second optical waveguide section preferably has a configuration in which, in the wavelength range of 1000 to 2000 nm, propagating light exists such that the relationship between the coupling efficiency X of the TE polarization component and the coupling efficiency Y of the TM polarization component of the optical waveguide section 1 and the second optical waveguide section is X / Y ≥ 1.0, and more preferably, propagating light exists such that X / Y ≥ 1.2, and even more preferably, X / Y ≥ 1.4. Having X / Y within this range reduces noise in the light guiding the core of the optical waveguide section 1, thereby improving transmission characteristics. Furthermore, although not particularly limited, X ≥ 70% is preferred, X ≥ 80% is more preferred, and X ≥ 90% is particularly preferred. Also, Y ≤ 90% is preferred, Y ≤ 80% is more preferred, and Y ≤ 70% is particularly preferred. It is preferable that the coupling efficiency X and coupling efficiency Y satisfy the above relationship in both cases: when light propagates from optical waveguide section 1 to the second optical waveguide section, and when light propagates from the second optical waveguide section to optical waveguide section 1. When optical waveguide section 1 and the second optical waveguide section are single-mode waveguides, the coupling efficiency of the TE and TM polarization components is usually constant regardless of the direction of light propagation. The coupling efficiency X of the TE polarization component and the coupling efficiency Y of the TM polarization component can be obtained, for example, by coupling optical fibers to both ends of the optical waveguide element and evaluating the intensity of each emitted polarization component. Estimation by optical simulation is also possible.

[0142] When light with a wavelength in the range of 1000 to 2000 nm propagates from the core of the optical waveguide section 1 to the second core section 111 of the second optical waveguide section 110, or from the core section 111 of the second optical waveguide section 110 to the core of the optical waveguide section 1, the wavelength of light that satisfies the above relational expression for the relationship between the coupling efficiency X of the TE polarization component and the coupling efficiency Y of the TM polarization component is preferably in the range of 1260 to 1360 nm or 1460 to 1675 nm, more preferably in the range of 1300 to 1310 nm or 1550 nm, even more preferably 1300 nm, 1310 nm or 1550 nm, and particularly preferably 1300 nm or 1550 nm.

[0143] The optical waveguide sheet is not particularly limited in its configuration as long as it satisfies the above requirements, but for example, a configuration comprising the second optical waveguide portion on a substrate can be used. As the substrate, a rigid substrate or a film-like substrate can be used, and for example, silicon wafers, silicon wafers with oxide films, polyimide resins, epoxy resins, PEEK resins, liquid crystal polymers, glass, glass epoxy substrates, etc., can be used. The preferred form and preferred forming material of the second optical waveguide portion in the optical waveguide sheet are as described in the description of the optical waveguide element.

[0144] The optical waveguide device comprising the optical waveguide section 1 is not particularly limited as long as it comprises an optical waveguide section, but specifically, examples include devices comprising a single optical waveguide, and optical waveguide elements such as PLCs (Planar Lightwave Circuits) consisting of multiple waveguides, optical switches, optical filters, wavelength division multiplexers, polarization separators, optical phase shifters, and optical modulators.

[0145] The optical waveguide element may also serve as a connection for mode coupling (optical coupling) of a first optical waveguide section 100 and a second optical waveguide section 110 formed on separate members, and more preferably for adiabatic coupling. For example, the optical waveguide element is formed by connecting the second optical waveguide section 110 formed on one member to the first optical waveguide section 100 formed on the other member, or by connecting the second optical waveguide section 110 provided on the optical waveguide sheet to an optical waveguide device equipped with an optical waveguide section 1 formed on another member, thereby mode coupling (optical coupling) of the two members, and more preferably, adiabatic coupling.

[0146] (Applications) This optical waveguide element efficiently connects two different optical waveguides and has high transmission characteristics. Due to these characteristics, this optical waveguide element can be used in optical components, including optical interconnection applications, and can be used as an optical waveguide element that modally couples (optically couples) or more preferably adiabatically couples a package substrate or the like with an optical waveguide such as an optical fiber.

[0147] An embodiment of the optical waveguide element of the present invention will be described below. However, the present invention is not limited to the following embodiment.

[0148] (Synthesis of organopolysiloxanes) The following organopolysiloxanes A-1, A-2, B-1, and B-2 were synthesized.

[0149] <Synthesis Example 1> 103.53 g of dimethoxydimethylsilane KBM-22 manufactured by Shin-Etsu Chemical Co., Ltd., 115.00 g of 3-methacryloyloxypropyltrimethoxysilane KBM-503, 109.27 g of toluene and 109.27 g of methanol were used as solvents, and a mixture of 76.72 g of 1N hydrochloric acid and 76.72 g of methanol was used as a catalyst. Hydrolysis condensation was carried out while maintaining the temperature from 15°C to 40°C. After that, the reaction solution was neutralized, washed with desalted water, the solvent and water were removed, and the mixture was filtered to obtain 140.9 g of the target liquid organopolysiloxane A-1.

[0150] <Synthesis Example 2> 72.71 g of dimethoxydimethylsilane KBM-22 manufactured by Shin-Etsu Chemical Co., Ltd., 150.00 g of 3-methacryloyloxypropyltrimethoxysilane KBM-503, 111.36 g of toluene and 111.36 g of methanol were used as solvents, and a mixture of 74.52 g of 1N hydrochloric acid and 74.52 g of methanol was used as a catalyst. Hydrolysis condensation was carried out while maintaining the temperature from 15°C to 40°C. After that, the reaction solution was neutralized, washed with desalted water, the solvent and water were removed, and the mixture was filtered to obtain 140.3 g of the target liquid organopolysiloxane A-2.

[0151] <Synthesis Example 3> Organopolysiloxane B-1 was obtained using 3-methacryloyloxypropyltrimethoxysilane KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd., diphenylsilanediol manufactured by Tokyo Chemical Industry Co., Ltd., and trimethoxy(3,3,3-trifluoropropyl)silane manufactured by Tokyo Chemical Industry Co., Ltd., with reference to Japanese Patent Publication No. 2014-510159.

[0152] <Synthesis Example 4> Organopolysiloxane B-2 was obtained using 3-methacryloyloxypropyltrimethoxysilane KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd. and diphenylsilanediol manufactured by Tokyo Chemical Industry Co., Ltd., with reference to Japanese Patent Publication No. 2014-510159.

[0153] <Composition C-1> To 100 parts by mass of organopolysiloxane A-1, 2.0 parts by mass of 2-benzyl-2-(dimethylamino)-4'-morpholinobtyrophenone (Omnirad 369, manufactured by IGM Resins B.V.) and 40 parts by mass of propylene glycol monomethyl ether acetate were added and stirred for 2 hours to obtain composition C-1.

[0154] <Composition C-2> To 100 parts by mass of organopolysiloxane A-2, 2.0 parts by mass of 2-benzyl-2-(dimethylamino)-4'-morpholinobtyrophenone (Omnirad 369, manufactured by IGM Resins B.V.) and 68 parts by mass of propylene glycol monomethyl ether acetate were added and stirred for 2 hours to obtain composition C-2.

[0155] <Composition D-1> To 100 parts by mass of organopolysiloxane B-1, 0.5 parts by mass of 2-benzyl-2-(dimethylamino)-4'-morpholinobtyrophenone (Omnirad 369, manufactured by IGM Resins B.V.) and 20 parts by mass of propylene glycol monomethyl ether acetate were added, and the mixture was stirred for 2 hours to obtain composition D-1.

[0156] <Composition D-2> To 100 parts by mass of organopolysiloxane B-2, 0.5 parts by mass of 2-benzyl-2-(dimethylamino)-4'-morpholinobtyrophenone (Omnirad 369, manufactured by IGM Resins B.V.) and 20 parts by mass of propylene glycol monomethyl ether acetate were added, and the mixture was stirred for 2 hours to obtain composition D-2.

[0157] (Evaluation of refractive index of organosiloxane) <Example 1> Compositions C-1 and C-2 were applied by spin coating onto a glass substrate treated with a UV ozone cleaning device. Each of the resulting coating films was exposed to an LED light source with a wavelength of 365 nm at an exposure dose of 1000 mJ / cm². ２ Exposure was carried out to achieve the desired result. Subsequently, the surface of the coating film was cleaned with propylene glycol monomethyl ether acetate and 2-propanol, and then dried to obtain cured films of compositions C-1 and C-2, respectively. The refractive indices of these cured films at a wavelength of 1300 nm were measured using a prism coupler manufactured by Metricon, and were found to be 1.454 and 1.469, respectively.

[0158] The coupling efficiency of an optical waveguide using silicon dioxide as the cladding material and silicon (Si) as the core material, when connected to an optical waveguide using C-1 as the cladding material and C-2 as the core material, was calculated using the eigenmode expansion method (EME method) with the waveguide analysis software Lumérical MODE (Ansys). The wavelength of the propagating light was set to 1300 nm, and the coupling efficiency of the fundamental modes of TE was calculated. As shown in Figure 7, a structural model was set in which the core portion 101 of optical waveguide section 100 and the core portion 111 of optical waveguide section 110 are in direct contact. The parameters of the structural model are shown below.

[0159] (Core section 111) Width (W) 4 μm Height (H) 4 μm Refractive index 1.469

[0160] (Cladding portion 112) Height 16 μm Refractive index 1.454

[0161] (Core section 101) As shown in Figure 3-2, the width of the tip changes linearly (tapered) from 0.35 μm to 0.1 μm from the left side to the right end. Height 0.18 μm Refractive index 3.500 Taper length changed to 200 μm, 400 μm, and 1000 μm.

[0162] (Cladding portion 102) Height 14 μm Refractive index 1.450

[0163] The results are shown in Table 1 below.

[0164]

[0165] <Comparative Example 1> Compositions D-1 and D-2 were applied by spin coating to a glass substrate treated with a UV ozone cleaning device. Each of the resulting coating films was exposed to an LED light source with a wavelength of 365 nm at an exposure dose of 1000 mJ / cm². ２ Exposure was carried out to achieve the desired result. Subsequently, the surface of the coating film was cleaned with propylene glycol monomethyl ether acetate and 2-propanol, and then dried to obtain cured films of compositions D-1 and D-2, respectively. The refractive indices of these cured films at a wavelength of 1300 nm were measured using a prism coupler manufactured by Metricon, and were found to be 1.520 and 1.540, respectively.

[0166] The coupling efficiency of an optical waveguide using silicon dioxide as the cladding material and silicon as the core material, when connected to an optical waveguide using D-1 as the cladding material and D-2 as the core material, was calculated using the eigenmode expansion method (EME method) with the waveguide analysis software Lumérical MODE (Ansys). The wavelength of the propagating light was set to 1300 nm, and the coupling efficiency of the fundamental modes of TE was calculated. As shown in Figure 7, a structural model was set in which the core portion 101 of optical waveguide 100 and the core portion 111 of optical waveguide 110 are in direct contact. The parameters of the structural model are shown below.

[0167] (Core section 111) Width (W) 4 μm Height (H) 4 μm Refractive index 1.540

[0168] (Cladding portion 112) Height 16 μm Refractive index 1.520

[0169] (Core section 101) As shown in Figure 3-2, the width of the tip changes linearly (tapered) from 0.35 μm to 0.1 μm from the left side to the right end. Height 0.18 μm Refractive index 3.500 Taper length changed to 200 μm, 400 μm, and 1000 μm.

[0170] (Cladding portion 102) Height 14 μm Refractive index 1.450

[0171] The simulation results are shown in Table 2 below.

[0172]

[0173] (Examples 2-17, Comparative Examples 2-3) As shown in Table 3, the TE coupling efficiency (X) at each taper length was calculated in the same manner as in Example 1, except that the refractive index of the core portion 111 and the cladding portion 112 was changed. The simulation results are shown in Table 3. In addition, the coupling efficiency (Y) of the basic mode of TM was calculated for Examples 1-17 and Comparative Examples 1-3, and the coupling efficiency ratio (X / Y) was calculated. The results are shown in Table 3.

[0174] Regarding the results of the examples and comparative examples, if the TE coupling efficiency was less than 50% at each taper length, or if the coupling efficiency ratio (X / Y) was less than 1.00 at each taper length, it was determined that the two optical waveguide sections were not connected with high coupling efficiency.

[0175]

[0176] (Discussion of Results) From the results of the examples and comparative examples, it became clear that when the refractive index difference between the cladding portion 102 of the optical waveguide portion 100 and the core portion 111 of the optical waveguide portion 110 is 0.01 or more, and the refractive index difference between the cladding portion 102 of the optical waveguide portion 100 and the cladding portion 112 of the optical waveguide portion 110 is 0.05 or less, the coupling efficiency of the TE mode is high. Furthermore, it was confirmed that under these conditions, the coupling efficiency of the polarization component of the TE mode is higher compared to the TM mode, and that it is possible to selectively improve the coupling efficiency of the TE mode.

[0177] The optical waveguide element of the present invention efficiently connects two types of optical waveguides and has high transmission characteristics. Due to these characteristics, the optical waveguide element of the present invention can be used in optical components, including optical interconnection applications.

[0178] 100 First optical waveguide section 101 First core section 102 First cladding section 110 Second optical waveguide section 111 Second core section 112 Second cladding section 120 Joint section 121 Length of joint section 122 Taper angle of first core section 123 Taper length of first core section 131 Adhesive layer 141 Distance (gap) 142 Maximum widthwise length of second core section cross-section 143 Maximum heightwise length of second core section cross-section 144 Axial misalignment between first and second core sections 145 Height of second cladding section 146 Maximum widthwise length of first core section cross-section 147 Maximum heightwise length of first core section cross-section 148 Height of first cladding section 150 Barrier layer

Claims

1. An optical waveguide element comprising a coupling portion in which a first optical waveguide portion comprising a first core portion and a first cladding portion and a second optical waveguide portion comprising a second core portion and a second cladding portion are adiabatically coupled, wherein the refractive indices of the first core portion and the first cladding portion at a wavelength of 1300 nm are different, the refractive indices of the second core portion and the second cladding portion at a wavelength of 1300 nm are different, the refractive index of the second core portion at a wavelength of 1300 nm is 0.01 or greater than the refractive index of the first cladding portion at a wavelength of 1300 nm, and the absolute value of the refractive index difference between the first cladding portion and the second cladding portion at a wavelength of 1300 nm is 0.05 or less.

2. The optical waveguide element according to claim 1, wherein, in the wavelength range of 1000 to 2000 nm, there exists propagating light such that the relationship between the coupling efficiency X of the TE polarization component and the coupling efficiency Y of the TM polarization component of the first optical waveguide and the second optical waveguide is X / Y ≥ 1.

0.

3. The optical waveguide element according to claim 1, wherein the absolute value of the refractive index difference is 0.03 or less.

4. The optical waveguide element according to claim 2, wherein there exists propagating light in the wavelength range of 1260 to 1360 nm or 1460 to 1675 nm where X / Y ≥ 1.

0.

5. The optical waveguide element according to claim 2, wherein the wavelength of the propagating light is 1300 nm or 1550 nm.

6. The optical waveguide element according to claim 1, wherein the refractive index of the first core portion at a wavelength of 1300 nm is greater than the refractive index of the second core portion at a wavelength of 1300 nm.

7. The optical waveguide element according to claim 1, wherein the difference in relative refractive index between the first core portion and the first cladding portion at a wavelength of 1300 nm is greater than the difference in relative refractive index between the second core portion and the second cladding portion at a wavelength of 1300 nm.

8. The optical waveguide element according to claim 6, wherein in the coupling portion, the plan view shape of the tip of the first core portion is tapered, becoming narrower at the tip.

9. The optical waveguide element according to claim 7, wherein in the coupling portion, the plan view shape of the tip of the first core portion is tapered, becoming narrower at the tip.

10. The optical waveguide element according to claim 8, wherein the taper length at the tip of the first core portion is 100 μm or more.

11. The optical waveguide element according to claim 9, wherein the taper length at the tip of the first core portion is 100 μm or more.

12. The optical waveguide element according to any one of claims 1 to 11, wherein the first core portion and the first cladding portion are each independently composed of at least one selected from the group consisting of Si, SiN, SiON, SiOx and those containing impurities thereof.

13. The optical waveguide element according to any one of claims 1 to 11, wherein, in the coupling portion, when the maximum length in the width direction of the cross-section of the second core portion is W [μm] and the maximum length in the height direction is H [μm], H / W is 0.1 to 10.

14. The optical waveguide element according to any one of claims 1 to 11, wherein the distance between the first core portion and the second core portion in the coupling portion is 10 μm or less.

15. The optical waveguide element according to any one of claims 1 to 11, wherein, in the joint portion, the angle between the line connecting the cross-sectional center of the first core portion and the cross-sectional center of the second core portion and the interface between the first optical waveguide portion and the second optical waveguide portion is 60° to 120°.

16. The optical waveguide element according to any one of claims 1 to 11, wherein the second core portion and / or the second cladding portion are formed from a polymer material.

17. The optical waveguide element according to any one of claims 1 to 11, wherein the second core portion and / or the second cladding portion are formed by curing an organopolysiloxane-containing composition.

18. An optical waveguide sheet comprising a second optical waveguide portion having a structure that allows for adiabatic coupling with an optical waveguide portion 1 provided by an optical waveguide device, wherein the second optical waveguide portion comprises a second core portion and a second cladding portion, the refractive indices of the core portion and the cladding portion of the optical waveguide portion 1 at a wavelength of 1300 nm are different, the refractive indices of the second core portion and the second cladding portion at a wavelength of 1300 nm are different, the refractive index of the second core portion at a wavelength of 1300 nm is 0.01 or greater than the refractive index of the cladding portion of the optical waveguide portion 1 at a wavelength of 1300 nm, and the absolute value of the difference in refractive index between the second cladding portion and the cladding portion of the optical waveguide portion 1 at a wavelength of 1300 nm is 0.05 or less.

19. The optical waveguide sheet according to claim 18, wherein the second optical waveguide section has a configuration in which, in the wavelength range of 1000 to 2000 nm, there exists propagating light such that the relationship between the coupling efficiency X of the TE polarization component and the coupling efficiency Y of the TM polarization component of the optical waveguide section 1 and the second optical waveguide section is X / Y ≥ 1.0.

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