Optical waveguide, method for manufacturing optical waveguide, opto-electric hybrid substrate using optical waveguide, and active optical cable

Abstract

The invention provides an optical waveguide, a method for manufacturing the optical waveguide, an opto-electric hybrid substrate using the optical waveguide, and an active optical cable, wherein the inspection man-hour is reduced and the production efficiency is improved. An optical waveguide (1) having a core (2) and a cladding (3) that covers the core (2), the optical waveguide (1) having a mirror section (4) that changes the orientation of an optical path that propagates through the core (2), the mirror section (4) being configured from a recess (19) formed in one surface of the optical waveguide (1), the recess (19) having a substantially quadrangular frustum pyramid shape that narrows toward a bottom surface (20), a first surface (6) of the recess (19), which rises from the bottom surface (20), has a cross-section of the core (2), which is a reflection surface (5) that serves as an optical path, and the first surface (6) of the recess (19) and a second surface (7) adjacent to the first surface (6) are connected via a first curved section (8) that protrudes outward.

Description

Technical Field

[0001] The present invention relates to an optical waveguide, a method for manufacturing the optical waveguide, an optoelectronic hybrid substrate using the optical waveguide, and an active optical cable. More specifically, it relates to an optical waveguide and a method for manufacturing the optical waveguide with reduced inspection man-hours and high production efficiency, an optoelectronic hybrid substrate using the optical waveguide, and an active optical cable. Background Art

[0002] In recent years, in electronic devices and the like, with the increase in the amount of transmitted information, an optoelectronic hybrid substrate that uses both optical wiring and electrical wiring in addition to electrical wiring has been widely used. In this optoelectronic hybrid substrate, an optical waveguide is used as the optical wiring.

[0003] The optical waveguide is composed of a linear core and a cladding provided so as to cover the core, and optically connects between optical elements (for example, a light-emitting element and a light-receiving element). More specifically, while reflecting the light emitted from a light-emitting element such as a semiconductor laser at the boundary between the core and the cladding, a light-receiving element such as a photodiode receives the light, and communication is performed based on the light and dark pattern or the light intensity pattern of the received light.

[0004] As such an optical waveguide, for example, an optical waveguide 30 is disclosed in Patent Document 1, as Figure 21 shown, the optical waveguide 30 has: a core layer 32 in which a core portion 31 is formed; a first cladding 33 laminated on one surface of the core layer 32; a second cladding 34 laminated on the other surface of the core layer 32; and a mirror portion 35 that penetrates through the second cladding 34 and the core layer 32 and reaches the first cladding 33, respectively.

[0005] Moreover, an inclined surface 37 having a reflecting surface 36 is provided in the mirror portion 35 of the optical waveguide 30, and the light emitted from the light-emitting element is reflected by the reflecting surface 36, whereby the light is incident on the core portion 31.

[0006] Therefore, for example, when the reflecting surface 36 of the mirror portion 35 is not formed at the correct position with respect to the light-emitting element, sufficient light cannot be incident on the core portion 31, and connection failure may occur. Therefore, the position of the reflecting surface of the mirror portion with respect to the light-emitting element is extremely important in the optical waveguide.

[0007] Therefore, the optical waveguide usually undergoes two types of inspections, a mirror position inspection and an optical loss inspection, before installing the optical element. The mirror position inspection highly accurately confirms whether the reflecting surface of the mirror portion is formed at the correct position, and the optical loss inspection confirms the presence of a core defect and whether foreign matter is mixed in the core.

[0008] However, the mirror position inspection is usually performed using an image measurement system that automatically measures the size and shape of the reflecting surface of the mirror part based on an image obtained by a CCD camera. Therefore, it is necessary to introduce an expensive system, and the measurement takes time, which is the main reason for the decrease in the production efficiency of the optical waveguide.

[0009] Prior art documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-127783 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] Therefore, an object of the present invention is to provide an optical waveguide that reduces inspection man-hours and improves production efficiency.

[0014] Solutions to the Problems

[0015] In view of the above circumstances, the present inventors repeatedly made diligent studies and as a result, found the following and completed the present invention, that is: for the shape of the mirror part of the optical waveguide, by connecting the first surface having an optical path reflecting surface and the second surface adjacent to the first surface via a first bending part protruding outward, when the reflecting surface involves the first bending part, by using the situation where the optical loss increases, it is possible to detect the position deviation of the reflecting surface of the mirror part only by the optical loss inspection.

[0016] That is, the present invention has the following aspects. [1]

[0018] An optical waveguide having a core and a cladding covering the core, wherein,

[0019] the optical waveguide has a mirror part that changes the orientation of the optical path propagating in the core,

[0020] the mirror part is constituted by a concave part formed on one surface of the optical waveguide,

[0021] the shape of the concave part is a substantially frustum of a pyramid that narrows toward the bottom surface,

[0022] the first surface of the concave part that stands up from the bottom surface has a cross-section of the core that becomes an optical path reflecting surface,

[0023] the first surface of the concave part and the second surface adjacent to the first surface are connected via a first bending part protruding outward. [2]

[0025] The optical waveguide according to [1], wherein,

[0026] The first surface of the recessed portion and the second surface adjacent to the first surface are connected via the first bent portion that protrudes in a direction along the longitudinal direction of the optical waveguide. [3]

[0028] The optical waveguide according to [1] or [2], wherein

[0029] The first surface of the recessed portion and a third surface adjacent to the first surface and located on the opposite side of the second surface are connected via a second curved portion protruding outward. [4]

[0031] The optical waveguide according to any one of [1] to [3], wherein

[0032] The width d of the reflecting surface of the optical path is narrower than the width w of the first surface of the recess. [5]

[0034] The optical waveguide according to [4], wherein

[0035] The width d of the reflecting surface of the optical path and the width w of the first surface of the recessed portion are in a relationship satisfying the following formula (1).

[0036] 10μm≤(wd) / 2 (1) [6]

[0038] The optical waveguide according to [5], wherein

[0039] The width d of the reflecting surface of the optical path and the width w of the first surface of the recessed portion are in a relationship satisfying the following formula (2).

[0040] 10μm≤(wd) / 2≤50μm (2) [7]

[0042] The optical waveguide according to any one of [1] to [6], wherein

[0043] The first curved portion of the recessed portion extends to the bottom surface.

[0044] In a cross section obtained by horizontally cutting the concave portion at the height of the bottom of the reflecting surface of the optical path, a curvature radius of an inclined portion formed by the first surface of the concave portion and the first curved portion is set to be 10 μm or greater. [8]

[0046] The optical waveguide according to any one of [1] to [7], wherein

[0047] The first curved portion of the recessed portion extends to the bottom surface.

[0048] In a cross section obtained by horizontally cutting the recess at the height of the bottom of the reflecting surface of the optical path, a curvature radius of an inclined portion formed by the first surface of the recess and the first curved portion is 10 μm to 80 μm. [9]

[0050] An optoelectronic hybrid substrate, wherein:

[0051] The optoelectronic hybrid substrate has the optical waveguide described in any one of [1] to [8].

[10]

[0053] An active optical cable, wherein:

[0054] The active optical cable has the optical waveguide described in any one of [1] to [8].

[11]

[0056] A method for manufacturing an optical waveguide, wherein:

[0057] The method for manufacturing the optical waveguide includes the following steps:

[0058] preparing an optical waveguide having a core and a cladding provided so as to cover the core;

[0059] placing a mask having an opening on one surface of the optical waveguide; and

[0060] The opening of the mask is irradiated with laser light to form a concave portion serving as a mirror portion on one surface of the optical waveguide.

[0061] The shape of the opening of the mask is a deformed square with four corners protruding outward.

[0062] Effects of the Invention

[0063] That is, according to the optical waveguide of the present invention, the deviation of the reflecting surface of the mirror portion can be efficiently detected only by the optical loss inspection, so that the mirror position inspection is unnecessary, and the production efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a perspective view showing the main part of the optical waveguide according to the first embodiment of the present invention.

[0065] Figure 2 yes Figure 1 A-A' cross-sectional view.

[0066] Figure 3 yes Figure 1 Top view of the optical waveguide.

[0067] Figure 4 This is a cross-sectional view of the first surface of the recessed portion according to the first embodiment as viewed from the front.

[0068] Figure 5 It is a diagram showing a cross-sectional view obtained by horizontally cutting a concave portion along the height of the bottom side of the reflecting surface of the optical path of the optical waveguide of the first embodiment.

[0069] Figure 6 Schematically shows a method of forming a mirror portion of an optical waveguide according to an embodiment of the present invention by a laser processing method.

[0070] Figure 7 It is a diagram showing a situation of a process of forming a concave portion of a mirror portion using a laser region locus when viewed from above the optical waveguide.

[0071] Figure 8 It is a top view of a mask for forming a mirror portion of the first embodiment.

[0072] Figure 9 It is a perspective view showing a main part of an optical waveguide according to a second embodiment of the present invention.

[0073] Figure 10 It is Figure 9 a top view of the optical waveguide.

[0074] Figure 11 It is a perspective view showing a main part of an optical waveguide according to a third embodiment of the present invention.

[0075] Figure 12 It is Figure 11 a top view of the optical waveguide.

[0076] Figure 13 It is a perspective view showing a main part of an optical waveguide according to a fourth embodiment of the present invention.

[0077] Figure 14 It is Figure 13 a top view of the optical waveguide.

[0078] Figure 15 It is a diagram showing a cross-sectional view obtained by horizontally cutting a concave portion of the optical waveguide of Example 1 along the height of the bottom side of the reflecting surface of the optical path.

[0079] Figure 16 It is a diagram showing a cross-sectional view obtained by horizontally cutting a concave portion of the optical waveguide of Example 2 along the height of the bottom side of the reflecting surface of the optical path.

[0080] Figure 17 It is a diagram showing a cross-sectional view obtained by horizontally cutting a concave portion of the optical waveguide of Example 3 along the height of the bottom side of the reflecting surface of the optical path.

[0081] Figure 18This is a cross-sectional view showing the optical waveguide of Example 4 cut horizontally at the height of the bottom edge of the reflecting surface of the optical path to obtain the cross-section of the recessed portion.

[0082] Figure 19 This is a cross-sectional view showing the optical waveguide of the reference example cut horizontally at the height of the bottom edge of the reflecting surface of the optical path to obtain the cross-section of the recessed portion.

[0083] Figure 20 This is a cross-sectional view showing the optical waveguide of Comparative Example 1 cut horizontally at the height of the bottom edge of the reflecting surface of the optical path to obtain the cross-section of the recessed portion.

[0084] Figure 21 This is an explanatory view showing another example of a conventional optical waveguide.

[0085] Explanation of Reference Numerals

[0086] 1. Optical waveguide (first embodiment); 2. Core; 3. Cladding; 4. Mirror portion; 5. Reflecting surface; 5'. Displaced reflecting surface; 5(a). Upper edge of the reflecting surface; 5(b). Bottom edge of the reflecting surface; 5(c). Height to the bottom edge of the reflecting surface; 6. First surface; 7. Second surface; 8. First bending portion; 9. Third surface; 10. Second bending portion; 11. Fourth surface; 12. Third bending portion; 13. Fourth bending portion; 14. Mask; 15. Opening; 17. Shielding portion; 18. Protrusion of the mask; 19. Recessed portion; 20. Bottom surface; 21. Tapered portion; 30. Optical waveguide; 31. Core portion; 32. Core layer; 33. First cladding; 34. Second cladding; 35. Mirror portion; 36. Reflecting surface; 37. Tapered surface; 38. Convex portion; 39. Edge portion; 40. Optical waveguide (second embodiment); 41. Optical waveguide (third embodiment); 42. Optical waveguide (fourth embodiment); d. Width of the core (width of the reflecting surface); e. Thickness of the core; h. Height of the recessed portion; q. Thickness of the optical waveguide; r. Radius of curvature of the tapered portion; s. Size in the longitudinal direction of the upper surface of the recessed portion; t. Size in the longitudinal direction of the bottom surface of the recessed portion; u. Width of the recessed portion; v. Length of one side of the mask opening; w. Width of the first surface; x. Center of the protrusion; y. Radius of the mask opening. Detailed Embodiments

[0087] Hereinafter, the present invention will be described based on examples of the mode for carrying out the present invention. However, the present invention is not limited to the embodiments described below.

[0088] In addition, in this specification, when expressed as "P or more" (P is an arbitrary number) or "Q or less" (Q is an arbitrary number), it also includes the meaning of "preferably greater than P" or "preferably less than Q".

[0089] In addition, in this specification, the optical loss inspection means that a light source and a detector are respectively connected to the input end and the output end of the optical waveguide, and the intensity difference between the input light and the output light is calculated, thereby checking the amount of optical loss. As the light source, for example, a semiconductor element that emits light of a specific wavelength such as a light-emitting diode can be used. In addition, as the detector, for example, a CCD detector that converts light into charge for detection can be used.

[0090] <First Embodiment>

[0091] Figure 1 It is a perspective view showing a main part of the optical waveguide 1 according to the first embodiment of the present invention.

[0092] The optical waveguide 1 has a core 2 and a cladding 3 covering the core 2. The optical waveguide 1 has a mirror portion 4 that changes the direction of the optical path propagating in the core 2. The mirror portion 4 is constituted by a concave portion 19 formed on one surface of the optical waveguide 1. The shape of the concave portion 19 is a substantially frustum of a quadrangular pyramid that narrows toward the bottom surface 20. The first surface 6 of the concave portion 19 that stands up from the bottom surface 20 has a cross section of the core 2 that serves as a reflecting surface 5 of the optical path. The first surface 6 and the second surface 7 of the concave portion 19 adjacent to the first surface 6 are connected via a first bending portion 8 that protrudes outward.

[0093] In addition, in Figure 1 For ease of explanation, the main part of the optical waveguide 1 is shown as a quadrangular prism, and a part of the core 2 and the mirror portion 4 is illustrated by a dotted line.

[0094] These structures will be described in detail below.

[0095] <Optical Waveguide>

[0096] The optical waveguide 1 is constituted by a core 2 and a cladding 3 covering the core 2, and the optical waveguide 1 is formed in a strip shape.

[0097] The thickness q of the optical waveguide 1 (refer to Figure 2 ) is not particularly limited, and is usually 10 μm or more and 200 μm or less, preferably 60 μm or more and 150 μm or less, more preferably 80 μm or more and 120 μm or less, and further preferably 90 μm or more and 110 μm or less. When the thickness q of the optical waveguide 1 is too small, the durability of the optical waveguide 1 tends to deteriorate. When the thickness q of the optical waveguide 1 is too large, it tends to be difficult to make it thinner and lighter. In addition, the thickness q of the optical waveguide 1 refers to the overall thickness including the core 2 and the cladding 3.

[0098] The core 2 of the optical waveguide 1 is used to propagate light that is reflected at the boundary between the core and the cladding 3 when the incident light enters.

[0099] The thickness e of the core 2 (refer to Figure 2)There is no particular limitation, preferably 60 μm or more and 150 μm or less, more preferably 80 μm or more and 120 μm or less, and still more preferably 85 μm or more and 100 μm or less.

[0100] In addition, the width d of the core 2 (hereinafter, the width d of the core 2 is synonymous with the width of the core cross-section and the width of the reflecting surface 5) (refer to Figure 4 )There is no particular limitation, preferably 30 μm or more and 100 μm or less, more preferably 40 μm or more and 80 μm or less, and still more preferably 45 μm or more and 60 μm or less.

[0101] When the thickness e and width d of the core 2 are too small, there is a tendency for the durability of the core 2 to deteriorate. When the thickness e and width d of the core 2 are too large, there is a tendency for it to be difficult to make it thinner and lighter.

[0102] As the forming materials for the core 2 and cladding 3 of the optical waveguide 1, for example, epoxy resins (such as glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, alicyclic epoxy resins, etc.), polyimide resins, acrylic resins, etc. can be cited. Among them, from the aspects of transparency, heat resistance, and fine patterning properties, epoxy resins are preferably used. They can be used alone or in combination of two or more.

[0103] The refractive index of the core 2 is generally greater than that of the cladding 3.

[0104] Both the core 2 and cladding 3 of the optical waveguide 1 are preferably formed of a resin having a coefficient of linear expansion of 30 ppm / °C or more and 120 ppm / °C or less, more preferably formed of a resin having a coefficient of linear expansion of 30 ppm / °C or more and 90 ppm / °C or less, and still more preferably formed of a resin having a coefficient of linear expansion of 30 ppm / °C or more and 70 ppm / °C or less. If the coefficients of linear expansion of the core 2 and cladding 3 of the optical waveguide 1 are within the above range, there is a tendency to further suppress the warping of the optical waveguide 1. In addition, generally, the coefficients of linear expansion of the core 2 and cladding 3 can be different from each other or the same.

[0105] Moreover, the optical waveguide 1 has a mirror portion 4 for changing the orientation of the optical path propagating in the core 2. As Figure 2 shown, the mirror portion 4 is constituted by a concave portion 19 formed on one surface of the optical waveguide 1. Moreover, when one surface of the optical waveguide 1 is set as the upper surface, the shape of the concave portion 19 becomes a substantially frustum of a pyramid that narrows toward the bottom surface 20 of the optical waveguide 1.

[0106] In addition, in Figure 2 , the first bending portion 8 and the fourth bending portion 13 described later are shown by dashed lines.

[0107] The height h of the recess 19 also depends on the thickness q of the optical waveguide 1 and the thickness e of the core 2, but is preferably 50 μm or more and 260 μm or less, more preferably 60 μm or more and 220 μm or less, and further preferably 70 μm or more and 180 μm or less.

[0108] In addition, the size s in the length direction of the upper surface of the recess 19 is preferably 150 μm or more and 650 μm or less, more preferably 180 μm or more and 550 μm or less, and further preferably 200 μm or more and 450 μm or less.

[0109] Moreover, the size t in the length direction of the bottom surface 20 of the recess 19 is preferably 30 μm or more and 390 μm or less, more preferably 40 μm or more and 330 μm or less, and further preferably 50 μm or more and 270 μm or less.

[0110] As described above, if the height h of the recess 19, the size s in the length direction of the upper surface, and the size t in the length direction of the bottom surface 20 are set within the above ranges, the angles of the inclined surfaces of the first surface 6 and the fourth surface 11 described later can be adjusted.

[0111] The width u of the recess 19 (refer to Figure 3 ) also depends on the width d of the core 2 (refer to Figure 4 ), but is preferably 150 μm or more and 500 μm or less, more preferably 200 μm or more and 400 μm or less, and further preferably 225 μm or more and 300 μm or less. If the width u of the recess 19 is set within the above range, the position deviation of the reflecting surface 5 can be efficiently detected by the optical loss inspection.

[0112] Moreover, in the recess 19 of the mirror portion 4, there are: a first surface 6 that stands up from the bottom surface 20 and has a cross-section of the core 2 that serves as a reflecting surface 5 for the optical path; and a second surface 7 that is adjacent to the first surface 6.

[0113] In addition, in the recess 19 of the mirror portion 4, there are: a third surface 9 that is adjacent to the first surface 6 and is located on the opposite side of the second surface 7 (refer to Figure 3 ); and a fourth surface 11 that is located on the opposite side of the first surface 6.

[0114] The first surface 6 is usually formed to be inclined 45° with respect to the bottom surface 20 in the length direction. By inclining the first surface 6 with respect to the bottom surface 20, the reflecting surface 5, which is the cross-section of the core 2 located on the first surface 6, functions to change the direction of the light propagating in the core 2 by 90° and incident on the light receiving portion of the optical element, or conversely, to change the direction of the light emitted from the light emitting portion of the optical element by 90° and incident on the core 2.

[0115] As shown in the top view of the optical waveguide 1 of Figure 3 Figure 3 , the second surface 7 stands vertically with respect to the bottom surface 20.

[0116] In addition, in Figure 3 Figure 3 , a part of the core 2 is shown by a dotted line.

[0117] In addition, the fourth surface 11 adjacent to the second surface 7 on the opposite side of the first surface 6 and the first surface 6 are in a symmetrical relationship.

[0118] In addition, the third surface 9 adjacent to the first surface 6 and the fourth surface 11 on the opposite side of the second surface 7 and the second surface 7 are in a symmetrical relationship.

[0119] In addition, convex portions 38 may be provided on the second surface 7 and the third surface 9.

[0120] Since the convex portion 38 is formed through the manufacturing process described later, the convex portion 38 can also be removed by cutting operation or the like.

[0121] The shape of the concave portion 19 is not limited to a substantially frustum shape formed by the first surface 6, the second surface 7, the third surface 9, and the fourth surface 11. For example, it includes a shape in which the second surface 7 and the third surface 9 are inclined with respect to the bottom surface 20, and a shape in which the fourth surface 11 stands vertically with respect to the bottom surface 20.

[0122] Moreover, the first surface 6 and the second surface 7 adjacent to the first surface 6 are connected via a first bending portion 8 protruding outward. This is the greatest feature of the present invention.

[0123] According to this structure, when the reflecting surface 5 is offset to the position of the reflecting surface 5', for example, the reflecting surface 5' enters the first bending portion 8. Thus, when performing the optical loss inspection, the optical loss increases, and the position offset of the reflecting surface 5 can be detected.

[0124] That is, when the reflecting surface 5 is offset to the position of the reflecting surface 5' and enters the first bending portion 8, not all of the light from the light source input to the optical waveguide 1 from the light emitting side can reach the light receiving side. Therefore, the amount of electric charge that can be converted on the light receiving side decreases. By checking whether this amount of electric charge decreases, the position offset of the reflecting surface 5 can be detected through the optical loss inspection.

[0125] Normally, as Figure 4As shown, the first curved portion 8 extends from the upper surface of the recessed portion 19 of the mirror portion 4 to the bottom surface 20. However, since the reflective surface 5 can enter the first curved portion 8, the positional deviation of the reflective surface 5 can be detected by optical loss inspection, and therefore it does not necessarily need to extend to the bottom surface 20. In other words, the first curved portion 8 preferably only needs to be within the range from the upper surface of the recessed portion 19 of the mirror portion 4 to the bottom edge 5(b) of the reflective surface, and more preferably only needs to be within the range from the upper edge 5(a) of the reflective surface to the bottom edge 5(b) of the reflective surface.

[0126] The shape of the first bent portion 8 will be described below using a cross section obtained by horizontally cutting the recess 19 at a height 5 ( c ) to the bottom of the reflecting surface of the optical path.

[0127] like Figure 5 As shown, the first bent portion 8 protrudes in a direction along the longitudinal direction of the optical waveguide 1 and is connected to the first surface 6 and the second surface 7 .

[0128] Furthermore, the first curved portion 8 may be connected to the second surface 7 via a rounded edge portion 39 .

[0129] The edge portion 39 is formed by a manufacturing process described later, and therefore the edge portion 39 can be removed by cutting or the like.

[0130] In addition, in the cross-sectional plane, the first curved portion 8 is gently curved to connect to the first surface 6 and the second surface 7 , but the first curved portion 8 may be sharply bent.

[0131] However, from the viewpoint of achieving an excellent balance between increased efficiency in manufacturing the optical waveguide 1 and accuracy in optical loss inspection, it is preferable that the first bent portion 8 be gently curved.

[0132] When the first curved portion 8 is gently curved, the lower limit of the curvature radius r of the inclined portion 21 formed by the first surface 6 of the recess 19 and the first curved portion 8 is preferably 10 μm or more, more preferably 20 μm or more, and further preferably 30 μm or more.

[0133] The upper limit of the curvature radius r of the inclined portion 21 is preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 65 μm or less. In other words, the curvature radius r of the inclined portion 21 formed by the first surface 6 of the recess 19 and the first curved portion 8 is preferably 10 μm or more and 80 μm or less.

[0134] If the radius of curvature r is within the above range, the position deviation of the reflecting surface 5 can be efficiently detected by the optical loss inspection. Here, the radius of curvature r of the inclined portion 21 refers to the radius of curvature r of the inclined portion 21 when observing the cross-sectional plane obtained by horizontally cutting the concave portion 19 along the height up to the bottom edge of the reflecting surface 5 (see Figure 5 etc.).

[0135] In particular, if the first surface 6 and the third surface 9 adjacent to the first surface 6 and located on the opposite side of the second surface 7 are connected via the second bending portion 10 in the same manner as the first bending portion 8, even when the reflecting surface 5 has a position deviation to the left or right in the width direction, the position deviation of the reflecting surface 5 can be efficiently detected by the optical loss inspection.

[0136] Moreover, if the second surface 7 and the third surface 9 and the fourth surface 11 adjacent to the opposite side of the first surface -six are connected via the third bending portion 12 and the fourth bending portion 13 in the same manner as the first bending portion 8, when the fourth surface 11 has the reflecting surface 5, the position deviation of the reflecting surface 5 can also be efficiently detected on the fourth surface 11 by the optical loss inspection.

[0137] In addition, the second bending portion 10, the third bending portion 12, and the fourth bending portion 13 are preferably the same as the radius of curvature r of the first bending portion 8, but may be different from each other.

[0138] The radius of curvature r is usually determined after setting the width u of the concave portion 19 of the mirror portion 4 (see Figure 3 ). Therefore, when the radius of curvature r is too large, as Figure 4 shown, as a result, the width w of the first surface 6 becomes smaller, the portion where the reflecting surface 5 can be arranged becomes smaller, and there is a tendency that the design freedom of the optical waveguide 1 is reduced.

[0139] That is, it is preferable that the width w of the first surface 6 is wider than the width d of the reflecting surface 5. In other words, the width d of the reflecting surface 5 is narrower than the width w of the first surface 6. In particular, if the relationship between the width w of the first surface 6 and the width d of the reflecting surface 5 satisfies the following formula (1), the position deviation of the reflecting surface 5 can be detected more efficiently. In other words, the value of (w - d) / 2 ≥ 10 (μm).

[0140] 10 (μm) ≤ (w - d) / 2 (1)

[0141] In addition, the value of (w-d) / 2 can be 15 (μm) or more, or can be 20 (μm) or more. Further, the value of (w-d) / 2 can be 50 (μm) or less, or can be 45 (μm) or less. When the value of (w-d) / 2 satisfies the above conditions, the position deviation of the reflecting surface 5 can be detected more efficiently. For example, the relationship between the width w of the first surface 6 and the width d of the reflecting surface 5 satisfies the following formula (2).

[0142] 10 (μm) ≤ (w-d) / 2 ≤ 50 (μm) (2)

[0143] The width w of the flat surface of the first surface 6 is preferably 70 μm or more and 140 μm or less, more preferably 80 μm or more and 120 μm or less, and still more preferably 85 μm or more and 100 μm or less. If the width w is set within the above range, the position deviation of the reflecting surface 5 can be detected with higher precision.

[0144] <Manufacturing method of optical waveguide>

[0145] Next, a manufacturing method of the optical waveguide 1 according to an embodiment of the present invention will be described.

[0146] The optical waveguide 1 of the present embodiment can be manufactured by a process of preparing the optical waveguide 1 having the core 2 and the cladding 3 provided so as to cover the core 2, and a process of forming a concave portion 19 serving as a mirror portion 4 on one surface of the optical waveguide 1.

[0147] As a method of forming the concave portion 19 serving as the mirror portion 4 on one surface of the optical waveguide 1, for example, machining methods such as cutting and grinding, a laser processing method, an electron beam processing method, an imprint method, etc. can be cited. Among them, from the viewpoint of being able to form the mirror portion 4 with higher dimensional accuracy, it is preferable to form the mirror portion 4 by a laser processing method. Hereinafter, a method of forming the mirror portion 4 by a laser processing method will be described.

[0148] Figure 6 Schematically shows a method of forming the concave portion 19 serving as the mirror portion 4 of the optical waveguide 1 of the present embodiment by a laser processing method. When forming the concave portion 19 of the mirror portion 4 by a laser processing method, for example, the optical waveguide 1 is placed on a driving stage (not shown), and a mask 14 having an opening portion 15 with a special shape as described later is placed on one surface of the optical waveguide 1, and laser light is irradiated toward the opening portion 15 of the mask 14 in the direction of the white arrow 16.

[0149] Moreover, each time the laser is irradiated, the optical waveguide 1 is moved on the driving stage in the direction indicated by the black arrow, so that the concave portion 19 of the mirror portion 4 can be formed as a track of the laser irradiation area (see Figure 1 ).

[0150] Figure 7 The process of forming the concave portion 19 of the mirror portion 4 using the trajectory of the laser irradiation region is shown as viewed from above the optical waveguide 1. Specifically, when the optical waveguide 1 placed on the driving stage moves in the direction indicated by the black arrow, the opening 15 of the mask relatively moves in the direction opposite to the black arrow.

[0151] At this time, a difference in depth occurs due to a difference in the number of times (times) of exposure to the laser beam, forming a concave portion 19 of the mirror portion 4 having a predetermined inclined surface (first surface 6 ) and a reflecting surface 5 on the first surface 6 .

[0152] During the laser irradiation step, the optical waveguide 1 is moved relative to the fixed mask 14. However, the mask 14 may be moved while the optical waveguide 1 is fixed, or both may be moved. However, from the perspective of dimensional accuracy, it is preferable to move either one of them. In particular, from the perspective of not moving the laser irradiation device, it is preferable to move the optical waveguide 1.

[0153] The laser light source can be appropriately selected according to the wavelength of the oscillated laser light, and examples thereof include YAG laser, YVO laser, Yb laser, various solid-state lasers such as semiconductor lasers, CO laser, He—Ne laser, and various lasers such as excimer lasers.

[0154] The wavelength of the laser light can be appropriately selected depending on the constituent material of the optical waveguide 1 , and is preferably 150 nm to 950 nm, more preferably 200 nm to 850 nm, and even more preferably 300 nm to 750 nm.

[0155] like Figure 8 As shown, the mask 14 is a plate-shaped body having an opening 15 for the laser to pass through and a shielding portion 17 for shielding the laser. The shape of the opening 15 of the mask is a deformed square with four corners protruding outward.

[0156] The length v of each side of the square of the opening 15 of the mask 14, excluding the protruding portions at the four corners, also depends on the sizes of the optical waveguide 1 and the core 2, but is preferably 0.5 μm to 2.0 μm, more preferably 0.6 μm to 1.5 μm, and even more preferably 0.7 μm to 1.0 μm. If the length v of each side of the square of the opening 15 is set within the above range, the recess 19 of the mirror portion 4 can be formed to the set size.

[0157] The four protruding portions 18 at the four corners of the opening 15 are preferably shaped like circles superimposed on the corners of the square, and the centers x of the substantially circular circles are preferably located at the corners of the square.

[0158] The radius y of the circle is appropriately selected according to the radius of curvature r, preferably 0.03 mm or more and 0.45 mm or less, more preferably 0.04 mm or more and 0.3 mm or less, and still more preferably 0.05 mm or more and 0.3 mm or less. If the radius y of the circle is set within the above range, the position deviation of the reflecting surface 5 can be detected more efficiently.

[0159] In addition, in the present embodiment, the shape of the opening 15 of the mask 14 is a deformed square in which the four corners of the square protrude outward. However, in this square, each side is not formed by a straight line, and includes a case formed by a curve as long as it does not violate the gist of the present invention. Further, according to the same gist, the lengths of the respective sides of the square do not need to be strictly the same.

[0160] Moreover, the shape of the protruding portion 18 of the opening 15 is not only a substantially circular shape formed by overlapping the above-described circle on the four corners of the square, but for example, an oval shape or a shape formed by overlapping other shapes on the four corners of the square can also be used. However, in terms of the size of the first bending portion 8 capable of accurately forming the concave portion 19 of the mirror portion 4, a substantially circular shape formed by overlapping a circle on the four corners of the square is preferred.

[0161] <Optical communication module>

[0162] The optical waveguide 1 of the present embodiment can be used for optical wiring of an optoelectronic hybrid substrate.

[0163] Further, by connecting various cables and the like to the optoelectronic hybrid substrate using the optical waveguide 1 of the present embodiment, an optical communication cable (for example, an active optical cable) can be obtained. Therefore, the production efficiency of the optoelectronic hybrid substrate using the optical waveguide 1 and the optical communication cable using the optoelectronic hybrid substrate is improved.

[0164] <Second Embodiment>

[0165] Figure 9 is a perspective view showing a main part of an optical waveguide 40 according to a second embodiment of the present invention, Figure 10 is a plan view of the optical waveguide 40 according to the second embodiment.

[0166] The difference of the optical waveguide 40 of the second embodiment is that the second surface 7 and the third surface 9 do not have Figure 3 the convex portions 38 provided on the surfaces of the second surface 7 and the third surface 9 of the optical waveguide 1 of the first embodiment shown, that is, they are changed to flat surfaces. The other structures are the same as those of the optical waveguide 1 of the first embodiment shown in Figure 1 and the same reference numerals are given to the same parts and the description thereof is omitted.

[0167] As a method for manufacturing the optical waveguide 40, for example, by removing the convex portions 38 provided on the second surface 7 and the third surface 9 of the optical waveguide 1 of the first embodiment by means of a cutting operation or the like (refer to Figure 3 ), an optical waveguide 40 without the convex portion 38 can be manufactured.

[0168] Even in the case of the structure of the optical waveguide 40 of the second embodiment, when the position of the reflecting surface 5 is shifted, the position shift of the reflecting surface 5 can be detected by the optical loss inspection.

[0169] <Third Embodiment>

[0170] Figure 11 FIG. is a perspective view showing a main part of the optical waveguide 41 of the third embodiment of the present invention. Figure 12 FIG. is a top view of the optical waveguide 41 of the third embodiment.

[0171] The difference of the optical waveguide 41 of the third embodiment is that the connecting portions between the first bending portion 8 and the second surface 7, the connecting portion between the second bending portion 10 and the third surface 9, the connecting portion between the third bending portion 12 and the third surface 9, and the connecting portion between the fourth bending portion 13 and the second surface 7 do not have Figure 3 the rounded edge portions 39 provided in the connecting portion between the first bending portion 8 and the second surface 7, the connecting portion between the second bending portion 10 and the third surface 9, the connecting portion between the third bending portion 12 and the third surface 9, and the connecting portion between the fourth bending portion 13 and the second surface 7 of the optical waveguide 1 of the first embodiment as shown. Except for this, the structure is the same as that of the optical waveguide 1 of the first embodiment shown in Figure 1 , and the same reference numerals are assigned to the same parts and the description thereof is omitted.

[0172] As a method for manufacturing the optical waveguide 41, for example, by removing the rounded edge portions 39 provided in the connecting portion between the first bending portion 8 and the second surface 7, the connecting portion between the second bending portion 10 and the third surface 9, the connecting portion between the third bending portion 12 and the third surface 9, and the connecting portion between the fourth bending portion 13 and the second surface 7 of the optical waveguide 1 of the first embodiment by means of a cutting operation or the like (refer to Figure 3 ), an optical waveguide 41 without the edge portion 39 can be manufactured.

[0173] Even in the case of the structure of the optical waveguide 41 of the third embodiment, when the position of the reflecting surface 5 is shifted, the position shift of the reflecting surface 5 can be detected by the optical loss inspection, and by not forming the edge portion 39 (refer to Figure 3 ), thus as Figure 12As shown, the shape of the opening of the mirror part 4 is close to a rectangular shape, the rigidity of the optical waveguide 41 becomes higher, and there is a tendency for excellent mechanical strength.

[0174] <Fourth Embodiment>

[0175] Figure 13 It is a perspective view of the main part of the optical waveguide 42 showing the fourth embodiment of the present invention. Figure 14 It is a top view of the optical waveguide 42 of the fourth embodiment.

[0176] The difference in this optical waveguide 42 is that the second surface 7 and the third surface 9 do not have Figure 3 the convex portions 38 provided on the surfaces of the second surface 7 and the third surface 9 of the optical waveguide 1 of the first embodiment shown; the connecting portions between the first bending portion 8 and the second surface 7, the second bending portion 10 and the third surface 9, the third bending portion 12 and the third surface 9, and the fourth bending portion 13 and the second surface 7 of the optical waveguide 42 do not have Figure 3 the rounded edge portions 39 provided on the connecting portions between the first bending portion 8 and the second surface 7, the second bending portion 10 and the third surface 9, the third bending portion 12 and the third surface 9, and the fourth bending portion 13 and the second surface 7 of the optical waveguide 1 of the first embodiment shown. Except for this, the structure is the same as that of the optical waveguide 1 of the first embodiment shown in Figure 1 and the same reference numerals are given to the same parts and their description is omitted.

[0177] As a manufacturing method of the optical waveguide 42, for example, by removing the convex portions 38 (refer to Figure 3 ) provided on the second surface 7 and the third surface 9 of the optical waveguide 1 of the first embodiment, and the rounded edge portions 39 (refer to Figure 3 ) provided on the connecting portions between the first bending portion 8 and the second surface 7, the second bending portion 10 and the third surface 9, the third bending portion 12 and the third surface 9, and the fourth bending portion 13 and the second surface 7 of the optical waveguide 1 of the first embodiment by cutting operations or the like, it is possible to fabricate the optical waveguide 42 that does not have the convex portions 38 (refer to Figure 3 ) and the edge portions 39 (refer to Figure 3 ).

[0178] Even with the structure of the optical waveguide 42 of this fourth embodiment, in the case where the position of the reflecting surface 5 is displaced, it is possible to detect the displacement of the position of the reflecting surface 5 by optical loss inspection.

[0179] Examples

[0180] Next, specific examples of the present invention will be described.

[0181] [Example 1]

[0182] First, prepare an optical waveguide having a core (thickness e of 100 μm, width d of the core (width of the reflective surface) of 45 μm) and a cladding covering the core.

[0183] Moreover, as a mask used during laser irradiation for forming the mirror portion of the optical waveguide, prepare a mask having a deformed square shape with square corners protruding outward, where the length v of one side of the square is 0.75 mm and the size of the radius y of the circle is 0.05 mm.

[0184] Next, place the prepared optical waveguide on the driving stage, place the prepared mask with a special opening shape on one surface of the optical waveguide, and perform laser irradiation (wavelength 248 nm) using a YAG laser. Then, each time the laser is irradiated, move the optical waveguide to form a concave portion serving as the mirror portion such that the size s in the length direction of the upper surface of the concave portion, the size t in the length direction of the bottom surface, and the height h are approximately 230 μm, approximately 60 μm, and approximately 80 μm, respectively, to fabricate the optical waveguide of Example 1.

[0185] Figure 15 shows the shape of the mirror portion (concave portion) of the optical waveguide of Example 1.

[0186] In addition, Figures 15 - 20 is a diagram schematically showing a cross-sectional view obtained by horizontally cutting along the height of the bottom edge of the reflective surface of the optical path, and for easy understanding, the sizes and shapes of each part are exaggerated appropriately.

[0187] [Examples 2 to 4, Comparative Example]

[0188] Change the shape of the opening of the mask as follows. Except for this, fabricate the optical waveguides of Examples 2 to 4 and the Comparative Example in the same manner as in Example 1. That is, the shape of the opening of Examples 2 to 4 and the Comparative Example is a deformed square with square corners protruding outward, and the radius y of the circles at the four corners of the square is changed to the radii shown in Table 1 below.

[0189] Figures 16 - 19 shows the shapes of the mirror portions (concave portions) of the optical waveguides of Examples 2 to 4 and the Comparative Example.

[0190] [Comparative Example 1]

[0191] Except for changing the shape of the opening of the mask to a square with a side of 0.75 μm (i.e., a conventional mask without a protruding portion at the opening), fabricate the optical waveguide of Comparative Example 1 in the same manner as in Example 1.

[0192] Figure 20 It represents the shape of the mirror part (concave part) of the optical waveguide of Comparative Example 1.

[0193] Using a digital microscope (VH X-7000, manufactured by Keyence Corporation), the width w of the flat surface of the first surface and the radius of curvature r of the inclined part were measured in the cross-sectional plane obtained by horizontally cutting the optical waveguides of Example 1 to Example 4, the reference example, and Comparative Example 1 along the height of the bottom edge of the reflecting surface with respect to the mirror part (concave part). The obtained values are shown in Table 1 described later.

[0194] In addition, these values were substituted into the following formula (1) to calculate the detectable range of the position shift of the reflecting surface. The calculated values are also shown in Table 1 described later.

[0195] 10 (μm) ≤ (w - d) / 2 (1)

[0196] (Evaluation of the position shift of the reflecting surface)

[0197] Optical waveguides of Example 1 to Example 4, the reference example, and Comparative Example 1 were respectively fabricated, and a mass-production high-speed conduction inspection (optical loss inspection) of the polymer optical wiring waveguides was performed on these optical waveguides using an optical wiring waveguide high-speed conduction inspection device (manufactured by Synergy Optosystems Co., Ltd.) with an optical tester, and the loss generated by the optical tester was measured to evaluate the position shift of the reflecting surface. In addition, among the optical waveguides of Example 1 to Example 4, the reference example, and Comparative Example 1 fabricated in large quantities, there are optical waveguides with a shift of the reflecting surface of the mirror part.

[0198] Whether the reflecting surface of the mirror part is in the normal position is confirmed by the brightness of the light displayed on the measurement screen of the optical tester. The optical waveguide with a shift of the reflecting surface of the mirror part is displayed 30% darker than the optical waveguide with the reflecting surface of the mirror part in the normal position.

[0199] When there is a darker part displayed on the measurement screen of the optical tester, it is marked as 〇 (circle) as being able to determine the position shift of the reflecting surface of the mirror part in the optical loss inspection, and when there is no darker part displayed on the measurement screen of the optical tester, it is marked as × (cross) as being unable to determine the position shift of the reflecting surface of the mirror part in the optical loss inspection, and the results are shown in Table 1 described below.

[0200] Table 1

[0201]

[0202] As shown in Table 1, in Examples 1 to 4, it is possible to evaluate whether there is a positional shift in the reflective surface only by performing an optical loss inspection. In contrast, in Comparative Example 1, which is an existing product, it is not possible to evaluate whether there is a positional shift in the reflective surface only by an optical loss inspection.

[0203] In addition, in the reference example, since the width d of the core (width of the reflective surface) is greater than the width w of the flat surface of the first surface, it is not possible to evaluate whether there is a positional shift in the reflective surface. However, by making the width d of the core (width of the reflective surface) less than the width w of the flat surface of the first surface, it is possible to evaluate whether there is a positional shift in the reflective surface.

[0204] Industrial applicability

[0205] The optical waveguide of the present invention can be widely used in high-speed signal transmission technology.

Claims

1. An optical waveguide comprising a core and a cladding covering the core, wherein: The optical waveguide includes a mirror portion for changing the direction of the light path propagating in the core. The mirror portion is composed of a recessed portion formed on one surface of the optical waveguide. The shape of the recess is a substantially quadrangular pyramid that narrows toward the bottom surface. The first surface of the recessed portion rising from the bottom surface has a cross section of the core that serves as a reflection surface of the light path. The first surface of the recessed portion and the second surface adjacent to the first surface are connected via a first curved portion protruding outward.

2. The optical waveguide according to claim 1, wherein The first surface of the recessed portion and the second surface adjacent to the first surface are connected via the first bent portion that protrudes in a direction along the longitudinal direction of the optical waveguide.

3. The optical waveguide according to claim 1, wherein The first surface of the recessed portion and a third surface adjacent to the first surface and located on the opposite side of the second surface are connected via a second curved portion protruding outward.

4. The optical waveguide according to claim 1 or 2, wherein The width d of the reflecting surface of the optical path is narrower than the width w of the first surface of the recess.

5. The optical waveguide according to claim 4, wherein The width d of the reflecting surface of the optical path and the width w of the first surface of the recess are in a relationship satisfying the following formula (1): 10μm≤(wd) / 2 (1).

6. The optical waveguide according to claim 5, wherein The width d of the reflecting surface of the optical path and the width w of the first surface of the recess are in a relationship satisfying the following formula (2): 10μm≤(wd) / 2≤50μm (2).

7. The optical waveguide according to claim 1, wherein The first curved portion of the recessed portion extends to the bottom surface. In a cross section obtained by horizontally cutting the recess at the height of the bottom of the reflecting surface of the optical path, a curvature radius of an inclined portion formed by the first surface of the recess and the first curved portion is set to be 10 μm or greater.

8. The optical waveguide according to claim 7, wherein In a cross section obtained by horizontally cutting the recess at the height of the bottom of the reflecting surface of the optical path, a curvature radius of an inclined portion formed by the first surface of the recess and the first curved portion is 10 μm to 80 μm.

9. An optoelectronic hybrid substrate, wherein: This opto-electric hybrid substrate comprises the optical waveguide according to any one of claims 1 to 8.

10. An active optical cable, wherein: This active optical cable comprises the optical waveguide according to any one of claims 1 to 8.

11. A method for manufacturing an optical waveguide, wherein: The method for manufacturing the optical waveguide includes the following steps: preparing an optical waveguide having a core and a cladding provided so as to cover the core; placing a mask having an opening on one surface of the optical waveguide; as well as The opening of the mask is irradiated with laser light to form a concave portion serving as a mirror portion on one surface of the optical waveguide. The shape of the opening of the mask is a deformed square with four corners protruding outward.

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