WO2009131231A1

WO2009131231A1 - Method for manufacturing optical waveguide having inclined end surface

Info

Publication number: WO2009131231A1
Application number: PCT/JP2009/058220
Authority: WO
Inventors: Tohru Nakashiba; Yuichi Fujisawa; Shinji Hashimoto; Naoyuki Kondou
Original assignee: Panasonic Electric Works Co., Ltd.
Priority date: 2008-04-21
Filing date: 2009-04-20
Publication date: 2009-10-29
Also published as: JP2009258563A; JP5319954B2

Abstract

Disclosed is a method for manufacturing an optical waveguide having an inclined end surface, the method comprising: a perpendicular cutting step of causing a router bit, which has a predetermined inclined surface at a leading end portion, to penetrate in a perpendicular direction to a predetermined depth while cutting the optical waveguide, from above a position at which an inclined end surface of the optical waveguide is to be formed; and a parallel cutting step of moving the penetrated router bit in parallel or perpendicular direction relative to the longitudinal direction of the optical waveguide, while maintaining the height of the router bit, to form thereby an inclined end surface. The object of such a method is to provide a method for manufacturing an optical waveguide having an accurately disposed inclined end surface.

Description

DESCRIPTION

METHOD FOR MANUFACTURING OPTICAL WAVEGUIDE HAVING INCLINED END SURFACE

TECHNICAL FIELD

The present invention relates to a method for manufacturing an optical waveguide having an inclined end surface used in mirrors and the like.

BACKGROUND ART

Micromirrors for inputting and outputting light to/from optical waveguides are formed in optical waveguides such as optical fibers or flat optical waveguides. Micromirrors are, for instance, 45-degree inclined end surfaces that can change an optical path by 90 degrees.

Known methods for forming such mirrors include, for instance, methods that involve forming inclined end surfaces by cutting an optical waveguide with a dicing blade.

For instance, Patent document 1 discloses the feature of cutting an optical waveguide, using a dicing blade whose cutting edge has a cross-sectional shape with a 90° apex angle, or whose cutting edge has a substantially wedge-like cross section, with an apex angle of about 45°, such that the dicing blade abuts substantially perpendicularly against the optical waveguide. Patent document 1 discloses that a micromirror having an inclined surface, through formation of a V-groove in the optical waveguide, can be formed by way of such a cutting process. Patent document 1 discloses also that the micromirror thus formed allows light propagating through the optical waveguide to exit out of the plane of the optical waveguide, or allows an optical path of light incident from outside the plane of the optical waveguide to be optically coupled to the optical waveguide .

Patent document 2 discloses the feature of cutting an optical waveguide using a dicing blade in which the leading end of the cutting edge has a flat portion, with a view to lessening the influence of blade wobbling or shape wear during cutting. Patent document 2 discloses the feature that inclined end surfaces used as a micromirror are formed by way of such a cutting method.

Circular rotary blades are used for cutting by dicing, and hence the contact width is prone to widening. Also, the contact width becomes wider as the cutting depth increases. For instance, when forming an inclined end surface on one specific optical waveguide 91 alone, upon formation of a plurality of optical waveguides over a narrow range as illustrated in Fig. 1, a dicing blade 90 cuts beyond the optical waveguide 91 into optical waveguides 92 and 93 that were not intended to be cut. Cutting by dicing precluded thus achieving the fine processing involved in forming accurately inclined end surfaces in only one specific optical waveguide.

In cutting by dicing, moreover, the running direction of the dicing blade 90 is restricted to one of the directions denoted by the arrow in Fig. 2. When forming respective mirrors in each of a plurality of optical waveguides (A, B) disposed perpendicular to each other, as illustrated in Fig. 2, it was necessary to remove temporarily the substrate on which the optical waveguides (A, B) were formed. The substrate was reset by changing the orientation thereof by 90 degrees, after which cutting had to start anew.

This method was problematic, on account of poor cutting efficiency, when inclined end surfaces are formed by dicing in a plurality of optical waveguides, as described above.

Patent document 1: Japanese Patent Application Laid-open No.HlO-300961

Patent document 2: Japanese Patent Application Laid-open No.2006-235126

DISCLOSURE OF THE INVENTION

One aspect of the present invention is a method for manufacturing an optical waveguide having an inclined end surface, the method comprising: a perpendicular cutting step of causing a router bit, which has a predetermined inclined surface at a leading end portion, to penetrate in a perpendicular direction to a predetermined depth while cutting the optical waveguide, from above a position at which an inclined end surface of the optical waveguide is to be formed; and a parallel cutting step of moving the penetrated router bit in parallel or perpendicular direction relative to the longitudinal direction of the optical waveguide, while maintaining the height of the penetrated router bit, to form thereby an inclined end surface.

The present invention allows forming accurately an inclined end surface only at a target position of an optical waveguide. Moreover, inclined end surfaces can be formed continuously, even when respective inclined end surfaces are formed in a plurality of optical waveguides disposed at mutually different angles, without removing and re-setting the work to be cut by changing the direction of the latter, as is the case during cutting by dicing.

The objects, characteristics, aspects and advantages of the present invention will be made more apparent on the basis of the detailed explanation and accompanying drawings below.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an illustrative diagram for explaining the formation process of an inclined end surface using a dicing blade;

Fig. 2 is an illustrative diagram for explaining variable direction during cutting of an optical waveguide using a dicing blade;

Fig. 3A is an illustrative diagram for explaining a step in the formation of a waveguide in a first embodiment;

Fig. 3B is an illustrative diagram for explaining a step in the formation of a waveguide in the first embodiment;

Fig. 3C is an illustrative diagram for explaining a step in the formation of a waveguide in the first embodiment;

Fig. 3D is an illustrative diagram for explaining a step in the formation of a waveguide in the first embodiment; Fig. 3E is an illustrative diagram for explaining a step in the formation of a waveguide in the first embodiment;

Fig. 4A is a cross-sectional schematic diagram illustrating an example of the leading end shape of a router bit;

Fig. 4B is a cross-sectional schematic diagram illustrating an example of the leading end shape of a router bit;

Fig. 5 is an illustrative diagram for explaining a process of forming an inclined end surface using a router bit;

Fig. 6 is an illustrative diagram for explaining a variable direction of a router bit;

Fig. 7 is a cross-sectional schematic diagram of an optical waveguide formed on a substrate;

Fig. 8A is an illustrative diagram for explaining part of a method for controlling cutting depth;

Fig. 8B is an illustrative diagram for explaining part of a method for controlling cutting depth;

Fig. 8C is an illustrative diagram for explaining part of a method for controlling cutting depth;

Fig. 9 is an illustrative diagram for explaining a method of forming respective inclined end surfaces in a plurality of optical waveguides, disposed substantially parallelly, in the first embodiment;

Fig. 1OA is an illustrative diagram for explaining a step in the formation of a waveguide in a second embodiment;

Fig. 1OB is an illustrative diagram for explaining a step in the formation of a waveguide in the second embodiment;

Fig. 1OC is an illustrative diagram for explaining a step in the formation of a waveguide in the second embodiment;

Fig. 1OD is an illustrative diagram for explaining a step in the formation of a waveguide in the second embodiment; and

Fig. 1OE is an illustrative diagram for explaining a step in the formation of a waveguide in the second embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[First embodiment]

An embodiment of the method for manufacturing an optical waveguide having an inclined end surface according to the present invention will be explained in detail next with reference to accompanying drawings .

Figs. 3A to 3E illustrate schematically the manufacturing process of a flat-plate optical waveguide 1, having inclined end surfaces 2, used as a mirror. In Figs. 3A to 3E, the reference numeral 2 denotes inclined end surfaces, 3 denotes a router bit, 10 denotes a substrate, 11 denotes a lower cladding layer (first cladding layer) , 12 denotes a core, 13 denotes an upper cladding layer (second cladding layer) and 20 denotes notched grooves.

In the present manufacturing process, firstly the lower cladding layer 11 is formed on the substrate 10, as illustrated in Fig. 3A.

As the substrate 10 there may be used various organic and inorganic substrates, without any particular limitation. Specific examples of organic substrates include epoxy substrates, acrylic substrates, polycarbonate substrates and polyimide substrates. Examples of inorganic substrates include, for instance, silicon substrates and glass substrates. The substrate used may also be a printed circuit substrate in which a circuit is formed beforehand on a substrate.

The method for forming the lower cladding layer 11 may involve bonding a resin film comprising a curable resin material having a predetermined refractive index, for forming the lower cladding layer 11, on the surface of the substrate 10, followed by curing, or may involve coating a liquid curable resin material for forming the lower cladding layer 11, followed by curing.

The curable resin material for forming the lower cladding layer 11 is a material having a lower refractive index, at the transmission wavelength of the guided light, than the curable resin material for forming the core 12. The refractive index at the transmission wavelength is, for instance, of about 1.5 to 1.54. Examples of such a curable resin material include, for instance, epoxy resins, acrylic resins, polycarbonate resins and polyimide resins having a refractive index within the above range.

The thickness of the lower cladding layer 11 is not particularly limited. Specifically, the thickness of the lower cladding layer 11 ranges preferably, for instance, from about 5 to 15 μm.

The specific method for forming the lower cladding layer 11 may be for instance as follows. A resin film comprising a curable resin material for forming the lower cladding layer 11 is overlaid on the surface of the substrate 10 and is then bonded to the latter by heat-pressing. Alternatively, the bonded resin film is cured through light irradiation or heating.

In another method, a liquid curable resin material or a varnish of a curable resin material for forming the lower cladding layer 11 is coated onto the surface of the substrate 10 by spin coating, bar coating, dip coating or the like, followed by curing through light irradiation or heating.

As illustrated in Fig. 3B, the core 12 is formed next on the lower cladding layer 11 formed as described above.

The specific method for forming the core 12 may be, for instance, as follows . ^■

A resin film comprising a curable resin material having a predetermined refractive index, for forming the core 12, is bonded to the surface of the lower cladding layer 11, or, alternatively, a liquid curable resin material for forming the core 12 is coated onto the surface of the lower cladding layer 11. Thereafter, only the portions that are to form the core 12 are selectively cured by- exposure via a photomask.

As the curable resin material for forming the core 12 there is used a material having a higher refractive index, at the transmission wavelength of the guided light, than that of the material of the lower cladding layer 11. The refractive index at the transmission wavelength is, for instance, of about 1.54 to 1.6. Examples of such a curable resin material include, for instance, epoxy resins, acrylic resins, polycarbonate resins, polyimide resins and the like.

The thickness of the core 12 is not particularly limited. Specifically, the thickness of the core 12 ranges preferably, for instance, from about 20 to 100 μm.

The selective exposure method used is not particularly limited, but may involve exposure of light having a wavelength capable of curing a photocurable resin material, at a light intensity necessary for curing, via a conventional photomask.

Selective exposure of the core is followed by developing. The core 12 such as the one illustrated in Fig. 3B is formed as a result. In developing, the unexposed portions, in the case of positive developing, or the exposed portions, in the case of negative developing, are washed with a developer, to remove unwanted portions. Specific examples of the developer include, for instance, acetone, isopropyl alcohol, toluene, ethylene glycol or a mixture of the foregoing at predetermined proportions. There may also be used, preferably, an aqueous developer such as the one disclosed in Japanese Patent Application Laid-open No.2007-292964. The developing method may involve spraying the developer or may involve ultrasonic cleaning.

Next, an upper cladding layer (second cladding layer) 13 is formed such a way so as to cover the core 12, as illustrated in Fig. 3C. The optical waveguide 1 is formed as a result.

The method of forming the upper cladding layer 13 may involve coating a liquid curable resin material for forming the upper cladding layer 13 in such a way so as to bury the core 12, followed by curing. Another method may involve bonding a resin film comprising a curable resin material, having a predetermined refractive index, for forming the upper cladding layer 13, followed by curing.

The curable resin material for forming the upper cladding layer 13 is not particularly limited, so long as it is a material having a lower refractive index, at the transmission wavelength of the guided light, than that of the core 12. The material is ordinarily a curable resin material identical to the material of the lower cladding layer 11.

The thickness of the upper cladding layer 13 is not particularly limited. For instance, the thickness of the upper cladding layer 13 is preferably comparable to the thickness of the lower cladding layer 11.

An optical waveguide 1 such as the one illustrated in Fig. 3C is obtained as a result the above process.

Next, a router bit 3 comprising a leading end portion having a predetermined inclined surface is penetrated (sunk) substantially perpendicularly into the optical waveguide 1, from above a region of the optical waveguide 1, formed as described above, where an inclined end surface is to be formed, to cut the optical waveguide 1 to a cutting depth D, as illustrated in Fig. 3D. The penetrated (sunk) router bit 3 is moved in a substantially parallel direction, to form inclined end surfaces 2 such as the ones illustrated in Fig. 3D. The leading end portion of the router bit has a predetermined inclined surface 3a such as the one illustrated in Fig. 4A or 4B. The angle of the inclined end surface is adjusted in accordance with the inclination angle of the inclined surface 3a. In the case of a 45-degree mirror, the inclination angle of the inclined surface 3a is 45 degrees. A router bit in which the cross-sectional shape of the leading end portion has a flat portion 3b, such as the one illustrated in Fig. 4B, is preferably used, in terms of preventing shape loss, caused by wear, at the router bit leading end.

In the cutting process by the router bit, as illustrated in Fig. 5, the router bit 3 having the inclined surface 3a rotating in the direction of the arrow is penetrated (sunk) into a region where there is to be formed an inclined end surface of a specific core 12 from among the cores 12 of a plurality of optical waveguides that are formed on the substrate 10. The router bit 3 can be moved, while maintaining the height of the latter, in the parallel direction (direction denoted by the white arrow in Fig. 5) . As a result, an accurate inclined end surface is formed only at the core 12 of a specific optical waveguide. The router bit can move freely in two dimensions. As illustrated in Fig. 6, the direction of the router bit, as denoted by the arrows in the figure, can be therefore modified freely when forming, for instance, inclined end surfaces in a plurality of optical waveguides (Ia, Ib, Ic) disposed at respectively dissimilar angles. As a result, it is not necessary to remove the work to be processed, change its direction and reset it, as is the case in cutting by dicing, which can only advance in one direction. Therefore, cutting using a router bit allows forming continuously an inclined end surface at a plurality of optical waveguides that are disposed at different angles.

The optical waveguides are ordinarily formed on a substrate. When using a thin film as the substrate, for instance a thin film such as those employed in flexible printed wiring boards, the height of the surface of the optical waveguide may be offset in parts, on account of slight bending of the film, even when the latter is accurately positioned on the cutting stage. It is difficult to grasp the surface height offset of the optical waveguide, which is caused by partial bending of the film, on the basis of the mechanical coordinates of the router bit alone. Also, as illustrated in Fig. 7, the core 12 may cause the upper cladding layer 13, comprised in the optical waveguide 1, to bulge up only at a portion above the core 12. In such cases, cutting can be carried out to an accurate depth by specifying the surface height of the optical waveguide in accordance with the method below.

Firstly, a recess 31 is formed, using a router bit, in the vicinity of the center of the position where the inclined end surfaces of the optical waveguide 1 are to be formed, as illustrated in Figs. 8A and 8B. The opening diameter W of the formed recess 31 is measured, as illustrated in Fig. 8C. The depth DO of the recess can be specified on the basis of the relationship between the diameter Wl of the leading end portion and the height H of the router bit, as illustrated in Fig. 4A or 4B. Taking as ZO the Z-axis coordinate of the router bit upon formation of the recess 31, inclined end surfaces of a cutting depth D can be formed accurately by sinking the router bit by a predetermined distance (D-DO) from the coordinate ZO. More specifically, the recess 31, having a shallower depth than a predetermined cutting depth D, is formed, using the router bit 3, in the vicinity of the center of the position where an inclined end surface is to be formed, as illustrated in Figs. 8A and 8B. The Z-axis coordinate in the height direction of the sunk router bit 3 is set to ZO . The opening diameter W of the recess 31 is measured after raising the router bit 3. The depth DO for an opening diameter W of the recess 31 is determined on the basis of the relationship between the specific height H and leading end portion diameter Wl of the router bit 3. That is, the depth DO can be specified on the basis of the height H of the router bit taking the diameter Wl of the leading end portion of the router bit to be identical to the opening diameter W, as illustrated in Fig. 8A or 8B. To realize the target cutting depth D, the router bit 3 is sunk to a position having a Z-axis coordinate zl (Zl=ZO- (D-DO) ) . A cut having a cutting depth D can thus be formed accurately by moving the router bit substantially in the parallel direction while maintaining the Z-axis coordinate Zl. The depth DO of the recess 31 is not particularly limited, but ranges preferably, for instance, from about 1/6 to 2/3, more preferably from about 1/3 to 1/2, relative to the cutting depth D. When the cutting depth D is for instance 90 μm, DO is set preferably to be no greater than 60 μm. Thus, inclined end surfaces can be formed with good precision by cutting to a specified Z-axis coordinate Zl, on the basis of the relationship between a specific height H and leading end portion diameter Wl of the router bit 3. Such a method allows preventing, for instance, excessive cutting in which the router bit reaches down to the lower cladding layer 11. The method allows also realizing high-precision positioning, of the order of several microns, since the parallel position precision of the inclined end surface 2 is influenced by the cutting depth.

The cutting operation becomes cumbersome when inclined end surfaces 71a to 71e are formed, at positions arrayed in a row, in a plurality of optical waveguides 70a to 7Oe that extend substantially parallel to each other across a predetermined gap, as illustrated in Fig. 9. Herein, the cutting operation involves, as described above, setting an accurate Z-axis coordinate (Zl_a to Zl_e) for each optical waveguide 70a to 7Oe, and also raising and lowering the router bit for each optical waveguide 70a to 7Oe. In such a case, a plurality of three-dimensional coordinates having a Z-axis coordinate (ZIi and Zl₂) for obtaining the cutting depth D of the router bit 3 in a respective optical waveguide are specified for at least two optical waveguides. The inclined end surfaces are formed across the plurality of optical waveguides by moving the router bit in parallel or perpendicular direction so as to join the three-dimensional coordinates having the Z-axis coordinates (ZIi and Zl₂) . Such a method allows forming inclined end surfaces in a plurality of optical waveguides at a time. Needless to say, increasing the number of Zl coordinates allows reducing in-plane precision variability. The number of Zl coordinates may be set so as to strike a balance with throughput .

The inclined end surfaces 2 thus formed may be used as mirrors without further modification, but are preferably used after being subjected to a smoothing treatment for increasing reflectance. Such a smoothing treatment affords mirrors of higher reflectance.

Specifically, the smoothing treatment may involve irradiating an energy beam, such as an infrared laser or the like, onto the surface of the inclined end surface 2, to melt and smoothen thereby the surface. The surface of the inclined end surface 2 cut using the router bit exhibits small cutting marks in the micron to submicron order. These cutting marks give rise to diffuse reflection of light. The smoothing treatment allows eliminating these small cutting marks.

Irradiation of energy beams relies on simpler equipment than contact methods, and, as a result, is free of the variability associated to contact methods. Also, the energy beam irradiation area can be limited, and hence only the inclined end surface is treated. The inclined end surface can be thermally melted more efficiently by imparting high-density energy to the surface using an infrared laser, to elicit molecular vibration at the surface being irradiated. Infrared lasers are easy to handle, and are thus also preferable on this score. Ordinarily, polymers absorb light, through molecular vibration, at wavelengths in the vicinity of 10 μm. Hence, a carbon dioxide gas laser having a wavelength in the vicinity of 10 μm is particularly preferred, in terms of keeping costs low.

Preferably, the energy beam is irradiated in the normal direction relative to the inclined end surface, since doing so allows irradiating the inclined end surface at a high energy density. In this case, energy irradiation at portions other than the inclined end s.urface is curtailed. This allows reducing the influence of irradiation on portions other than the inclined end surface, and affords thus higher energy efficiency. Irradiation along a normal direction relative to the optical waveguide itself makes for simpler equipment during energy beam irradiation.

Besides energy beam irradiation, other smoothing treatment methods include, for instance, coating the inclined end surface with a resin. The resin used for resin coating is a resin such as the one used for forming the core or the cladding. The resin is used diluted for coating. In this case, the resin exhibits excellent compatibility with the characteristics (coefficient of thermal expansion and the like) of the underlay, and moreover, the refractive indices of resin and underlay are similar. As a result, optical characteristics remain unimpaired. Good coating workability can be maintained by using a diluted resin. Furthermore, the resin can be coated in the minimum required amount, and thus the inclined end surfaces can be sufficiently smoothed as a result.

With a view to increasing the reflectance of the formed inclined end surfaces 2, a reflective film comprising, for instance, a metal or a dielectric multilayer film, may be formed on the surface of the inclined end surfaces 2 by a known method such as vapor deposition or sputtering, nanopaste printing and the like. Forming such a reflective film allows reflection to take place in specific directions, which is not possible in the case of total reflection.

As an example, a 45-degree inclined end surface was formed on an optical waveguide formed on the surface of a substrate, using a router bit shaped as illustrated in Fig. 4A (RFDAM 3175090, by Kemmer Japan) . The roughness of the obtained inclined end surfaces was 300 nm (rms) . The inclined end surface was irradiated, from the normal direction thereof, using a TEA-CO₂ laser (wavelength 9.8 μm) , under conditions that involved an energy density of 9 mJ/mm², an irradiation area of 100 μmD (square), an irradiation pulse count of 4, a pulse width of 9.3 μs, and a repetition frequency of 100 Hz. This smoothing treatment results in an inclined end surface exhibiting a roughness of 100 nm (rms) . A mirror surface was then formed by forming a reflective film, by vapor deposition, on the smoothed inclined end surface. Upon evaluation, the loss of the obtained mirror surface was of 1.2 dB at a wavelength of 850 μm. The waveguide was sliced and polished at a waveguide position 1 cm inwards from the position at which the mirror surface was formed, and then light was caused to strike the mirror surface. Reflection loss was evaluated on the basis of the power of the emission light that exited through the sliced end face.

In another example, a coating layer was formed on an inclined end surface having the above-described roughness of 300 nm (rms) . Specifically, a varnish was prepared first in which propylene glycol monomethyl ether acetate (PGMEA), as a curable resin material for forming the core, was diluted to a concentration of 2 mass%. A substrate having formed thereon an optical waveguide having the above-described inclined end surface was dipped in the varnish. The substrate was then taken out of the varnish. Then a coating layer was formed thereon through UV curing of the PGMEA adhered to the inclined end surface. The roughness of the inclined end surface improved from 300 nm (rms) to 62 nm (rms) . A reflective film was formed by metal vapor deposition on the smoothed inclined end surface, to form thereby a mirror surface. Upon evaluation, the loss of the obtained mirror surface was of 1.0 dB for a wavelength of 850 nm.

[Second embodiment]

In the second embodiment there is explained a method in which a core is formed and then inclined end surfaces are formed before covering the core with a cladding layer. A detailed explanation of portions common to the first embodiment will be omitted.

Figs 1OA to 1OE are process diagrams for explaining the manufacturing method of the second embodiment. In Figs. 1OA to 1OE, the reference numeral 82 denotes inclined end surfaces, 3 denotes a router bit, 10 denotes a substrate, 11 denotes a lower cladding layer (first cladding layer) , 12 denotes a core, 13 denotes an upper cladding layer (second cladding layer) and 30 denotes a notched groove .

In the present manufacturing process, the lower cladding layer 11 is formed first on the substrate 10, as illustrated in Fig. 1OA. As illustrated in Fig. 1OB, the core 12 is formed next on the lower cladding layer 11. Thus far, the method is identical to that of the first embodiment.

Then, as shown in Fig. 1OC, the router bit 3 is penetrated (sunk) into the core, in a substantially perpendicular direction, from above a region of the core 12 where an inclined end surface is to be formed. Inclined end surfaces 82 such as those illustrated in Fig. 1OD are then formed by causing the penetrated (sunk) router bit 3 to move in a direction perpendicular to the longitudinal direction of the core 12 while maintaining the height of the router bit 3. The formed inclined end surfaces may be optionally subjected to a smoothing treatment or may have a reflective film formed thereon, as in the first embodiment.

Lastly, the upper cladding layer (second cladding layer) 13 is formed so as to cover the core 12 in which the inclined end surfaces 82 are formed, to form thereby the optical waveguide 81, as illustrated in Fig. 1OE.

In the manufacturing method of the second embodiment, the inclined end surfaces 82 are formed on the core 12 not covered by the second cladding layer 13. Forming the inclined end surfaces 82 this way has the following advantages. When the core 12 is covered by the second cladding layer 13, part of the surface of the second cladding layer 13 bulges up, as illustrated in Fig. 7. In such a case, the surface height of the second cladding layer 13 is nonuniform, and hence it is difficult to sink the router bit 3 into the core 12 while maintaining an accurate depth. In the present manufacturing method, the inclined end surfaces 82 can be formed with high precision in the core 12, without any concerns as to the uniformity of the surface height of the second cladding layer 13. Also, it is not necessary to cut the second cladding layer 13. Wear of the router bit 3 is curbed thereby. The amount of cutting chips, moreover, is greatly reduced. Forming the second cladding layer 13 after formation of the inclined end surfaces 82 allows obviating a process, e.g. formation of a protective layer for protecting the inclined end surfaces, since the inclined end surfaces 82 are protected by the second cladding layer 13.

The above-described embodiments have been explained in detail on the basis of a flat plate-type optical waveguide, as a typical example, in which a core is embedded in a cladding layer, on a substrate. However, the present invention can also be used in instances where an optical fiber is fixed to a substrate.

Claims

1. A method for manufacturing an optical waveguide having an inclined end surface, the method comprising: a perpendicular cutting step of causing a router bit, which has a predetermined inclined surface at a leading end portion, to penetrate in a perpendicular direction to a predetermined depth while cutting said optical waveguide, from above a position at which an inclined end surface of said optical waveguide is to be formed; and a parallel cutting step of moving said penetrated router bit in parallel or perpendicular direction relative to the longitudinal direction of said optical waveguide, while maintaining the height of said penetrated router bit, to form thereby an inclined end surface .

2. The method for manufacturing an optical waveguide having an inclined end surface according to claim 1, wherein said perpendicular cutting step is a step of penetration from the surface of said optical waveguide by a cutting depth D, the method further comprising: a recess forming step of forming a recess by way of said router bit, in the vicinity of the center of a region where said inclined end surface is to be formed, and of setting a reference coordinate ZO in the Z-axis of coordinates of said router bit at the time of said recess formation; an opening diameter measuring step of measuring an opening diameter W of said recess; a step of calculating a depth DO of said recess on the basis of said measured opening diameter W, according to a relationship between diameter and height at a predetermined position of the leading end portion of said router bit; and a step of causing said router bit to penetrate to a Z-axis coordinate Zl=ZO-(D-DO) .

3. The method for manufacturing an optical waveguide having an inclined end surface according to claim 2, comprising: specifying a plurality of three-dimensional coordinates having said Z-axis coordinate Zl of respective optical waveguides for at least two optical waveguides selected from among a plurality of said optical waveguides that are disposed parallelly on a substrate; and forming inclined end surfaces across said plurality of optical waveguides while moving said router bit in the parallel or perpendicular direction so as to join the plurality of three-dimensional coordinates having said Z-axis coordinate Zl.

4. The method for manufacturing an optical waveguide having an inclined end surface according to any one of claims 1 to 3, further comprising a smoothing step of smoothing said inclined end surface by melting the surface through irradiation of an energy beam thereonto .

5. The method for manufacturing an optical waveguide having an inclined end surface according to any one of claims 1 to 3, further comprising a smoothing step of smoothing said inclined end surface by coating said surface with a resin.

6. A method for manufacturing an optical waveguide having an inclined end surface, comprising sequentially: a first step of forming a first cladding layer on a surface of a substrate; a second step of forming a core on a surface of said first cladding layer; a third step of forming an inclined end surface on said core; and a fourth step of forming a second cladding layer so as to bury said core, wherein said third step comprises: a perpendicular cutting step of causing a router bit, which has a predetermined inclined surface at a leading end portion, to penetrate in a perpendicular direction to a predetermined depth while cutting said core, from above a position at which an inclined end surface of said optical waveguide is to be formed; and a parallel cutting step of moving said penetrated router bit in parallel or perpendicular direction relative to the longitudinal direction of said core, while maintaining the height of said router bit, to form thereby an inclined end surface.

7. The method for manufacturing an optical waveguide having an inclined end surface according to claim 6, wherein said perpendicular cutting step is a step of penetration from the surface of said core by a cutting depth D, the method further comprising: a recess forming step of forming a recess by way of said router bit, in the vicinity of the center of a region where said inclined end surface is to be formed, and of setting a reference coordinate ZO in the Z-axis of coordinates of said router bit at the time of said recess formation; an opening diameter measuring step of measuring an opening diameter W of said recess; a step of calculating a depth DO of said recess on the basis of said measured opening diameter W, according to a relationship between diameter and height at a predetermined position of the leading end portion of said router bit; and a step of causing said router bit to penetrate to a Z-axis coordinate Zl=ZO-(D-DO) .

8. The method for manufacturing an optical waveguide having an inclined end surface according to claim 7, comprising: specifying a plurality of three-dimensional coordinates having said Z-axis coordinate Zl of respective cores for at least two cores selected from among a plurality of said cores that are disposed parallelly on a substrate; and forming inclined end surfaces across said plurality of cores while moving said router bit in the parallel or perpendicular direction so as to join the plurality of three-dimensional coordinates having said Z-axis coordinate Zl.

9. The method for manufacturing an optical waveguide having an inclined end surface according to any one of claims 6 to 8, further comprising a smoothing step of smoothing said inclined end surface by melting the surface through irradiation of an energy beam thereonto.

10. The method for manufacturing an optical waveguide having an inclined end surface according to any one of claims 6 to 8, further comprising a smoothing step of smoothing said inclined end surface by coating said surface with a resin.