Optical path changing device

Cores are embedded in a cladding, each core constituting a continuous optical path in which a first core end surface is exposed at a first end surface, and a second core end surface is exposed at a second end surface. Each of the continuous optical paths extends from the first core end surface to a mirror surface, is changed in direction at the minor surface, and then extends to the second core end surface. The first core end surfaces and the second core end surfaces are respectively arranged two-dimensionally at the first end surface and the second end surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a construction and a method for the manufacture of an optical path changing device for optically coupling parts having optoelectronic converting components, optical waveguides, etc., arranged two-dimensionally.

2. Description of the Related Art

In recent years, the development of optical interconnections for signal transmission inside devices at high density is being pursued vigorously with the aim of developing massively parallel computers for parallel signal processing between high-speed, high-capacity optical communication systems, large numbers of processors, etc. When performing optical interconnections of this kind, processing of transmitted optical signals is carried out by electronic devices. In the interface devices connecting these electronic devices, hybrid optical-electrical devices are required in which optical waveguides, optoelectronic converting components, large-scale integrated circuits (LSIs), switches, etc., for electronic control, or electric circuits for driving electronic components are combined. In order to achieve high-speed broadband communication systems, in particular, the demand for devices provided with optoelectronic converting components such as vertical-cavity surface-emitting lasers (VCSELs), laser diodes (LDs), photo diodes (PDs), etc., has risen.

To meet this kind of demand, techniques have been proposed such as “Ninety-degree Optical Path Changing Techniques in Optical Circuit Packaging”, Journal of Japan Institute of Electronics Packaging, Vol. 2, No. 5, pp. 368-372, 1999, for example, in which an optoelectronic converting component and an optical printed circuit board are optically coupled by disposing an optical pin with a micromirror on the optoelectronic converting component, disposing a through hole having a similar shape to the optical pin in the optical printed circuit board, and inserting the optical pin into the through hole.

In this conventional 90-degree optical path changing technique in optical circuit packaging, as shown inFIG. 17, a core2constituting an optical waveguide is embedded in an optical printed circuit board1, a through hole3is formed in the optical printed circuit board1so as to cut across the core2, and a micromirrored optical pin5fixed to an optoelectronic converting component4is inserted into the through hole3. The through hole3is formed into the optical printed circuit board1such that an aperture center thereof is perpendicular to an optical axis of the core2, and a tip surface of the optical pin5is formed into a micromirror5ahaving an angle of 45 degrees to the optical axis. Thus, for example, light propagating through the core2is totally reflected by the micromirror5a,is directed into the optical pin5, propagates inside the optical pin5, and reaches the optoelectronic converting component4. In other words, the core2and the optoelectronic converting component4are optically coupled by 90-degree optical path changing.

By adopting this conventional optical path changing technique, degradation of optical coupling between light-emitting components and the optical waveguide, optical coupling between the optical waveguide and light-detecting components, etc., resulting from light emitted from the light-emitting components into free space or light emitted from the optical waveguide into free space having an angle of radiation and spreading, can be prevented. In addition, using this conventional optical path changing technique is advantageous in that optical coupling between the optoelectronic converting component4and the core2can be performed by a like construction in cases where light is inserted into the core2from a light-emitting component (an optoelectronic converting component) such as a VCSEL, etc., through the micromirror5a, and also in cases where light is emitted from the core2into a light-detecting component (an optoelectronic converting component) such as a PD, etc.

However, because the conventional optical path changing technique is constructed in the above manner, micromirrored optical pins5must be secured to each of the optoelectronic converting components4separately, making the manufacturing process complicated and preventing cost reductions from being achieved.

Furthermore, it is necessary to form a through hole3in the optical printed circuit board1in order to insert the optical pin5. Since this optical pin5has a diameter of several μm to several hundred μm and the through hole3must be formed so as to have a diameter equivalent to the optical pin5, machining of the through hole3is extremely difficult, making the rate of production poor. This problem becomes more pronounced as the number of through holes3is increased. In addition, it is difficult to form the inner wall surfaces of the minute through hole3without irregularities, leading to deterioration of optical coupling efficiency between the core2and the optical pin5as a result of irregularities at the end surface of the core2formed by the through hole3.

In a construction in which the optoelectronic converting components4are arranged two-dimensionally, optical pins5must be fixed to large numbers of optoelectronic converting components4separately, making positioning accuracy of the optical pins5poor. Thus, optical axis misalignment may occur between the optoelectronic converting component4and the optical pin5, giving rise to deterioration in the optical coupling efficiency.

In a construction in which a large number of layers in which cores2are arranged two-dimensionally, in order to cape with increases in the number of optoelectronic converting components4, the lengths of the optical pins5differ in each core layer, making long optical pins5necessary. This lengthening of the optical pins5may give rise to buckling in the optical pins5, making the positioning accuracy of the micromirrors5arelative to the optical axes of the cores2poor, thereby causing the optical coupling efficiency to deteriorate.

SUMMARY OF THE INVENTION

The present invention aims to solve the above problems and an object of the present invention is to provide an optical path changing device and a method for the manufacture thereof enabling simplification of a manufacturing process, enabling cost reductions to be achieved, and enabling suppression of deterioration in optical coupling efficiency by integrating a plurality of optical waveguides and mirror surfaces for optical path changing for optically coupling parts such as optical waveguides, optoelectronic converting components, etc., arranged two-dimensionally.

With the above object in view, according to a first aspect of the present invention, there is provided an optical path changing device of the present invention including a cladding formed with a first end surface, a second end surface, and a mirror surface; and at least three cores embedded in the cladding. Each core constitutes a continuous optical path in which a first core end surface is exposed at the first end surface and a second core end surface is exposed at the second end surface. Each of the continuous optical paths extends from the first core end surface to the mirror surface, is changed in direction at the mirror surface, and extends to the second core end surface, The first core end surfaces and the second core end surfaces are arranged two-dimensionally at the first end surface and the second end surface, respectively.

Therefore, the present invention gives the effect that an optical path changing device having high optical coupling efficiency can be obtained at low cost.

According to a second aspect of the present invention, there is provided a method for manufacturing an optical path changing device including the step of preparing a first waveguide body in which at least one angular core composed of a pair of first and second core segments formed into an angular shape such that optical axes of the pair of first and second core segments intersect at an intersecting portion is embedded in a first substrate made of a first cladding formed with a mirror surface such that the pair of first and second core segments are arranged on a common plane perpendicular to the mirror surface with the intersecting portion of the optical axes positioned at the mirror surface. Yet, the method includes the step of preparing a second waveguide body in which at least two angular cores each composed of a pair of first and second core segments formed into an angular shape such that optical axes of each of the pairs of first and second core segments intersect at an intersecting portion are embedded in a second substrate made of a second cladding formed with a mirror surface such that the pairs of first and second core segments are arranged on a common plane perpendicular to the mirror surface with the intersecting portions of the optical axes positioned at the mirror surface. Further, the method includes the step of integrating the first and second waveguide bodies by laminating the first and second waveguide bodies such that the mirror surfaces are superposed in a direction of lamination, and then fixing together the first and second waveguide bodies.

Therefore, this method gives the effect that an optical path changing device having high optical coupling efficiency can be manufactured inexpensively.

According to a third aspect of the present invention, there is provided a method for manufacturing an optical path changing device including the step of preparing a waveguide body having a first end surface, a second end surface, and a mirror surface in which a plurality of first core segments are embedded inside a cladding so as to extend from the first end surface to the mirror surface such that core end surfaces of the first core segments are arranged two-dimensionally at the first end surface. Further, the method includes the step of forming second core segments inside the cladding by condensing and focusing a laser on the cladding of the waveguide body such that core end surfaces of the second core segments are arranged two-dimensionally at the second end surface and optical axes of each of the second core segments intersect optical axes of corresponding first core segments at the mirror surface such that each of the pairs of first and second core segments forms an angular core having a return portion at the mirror surface.

Therefore, this method gives the effect that an optical path changing device having high optical coupling efficiency can be manufactured inexpensively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be explained with reference to the drawings.

FIG. 1is a perspective schematically showing an optical path changing device according to Embodiment 1 of the present invention, andFIG. 2is a side elevation explaining an optical path changing operation in the optical path changing device according to Embodiment 1 of the present invention.

InFIG. 1, an optical path changing device10is prepared by embedding six angular cores11constituting optical paths inside a device cladding12.

A first end surface12a,a second end surface12b,and an optical-path-changing mirror surface13are formed into the device cladding12. First core end surfaces11aof the angular cores11are arranged into a 2 by 3 matrix shape (two-dimensionally) at the first end surface12aof the device cladding12, and second core end surfaces11bare arranged into a 2 by 3 matrix shape (two-dimensionally) at the second end surface12bof the device cladding12. Each of the angular cores11is formed into a “L” shape such that optical axes of an optical path extending from the first core end surface11ato the mirror surface13and an optical path extending from the second core end surface11bto the mirror surface13intersect at the mirror surface13and are symmetrical relative to a line perpendicular to the mirror surface13at a point of intersection between the optical axes. The six angular cores11are configured such that pairs of angular cores11arranged parallel to each other on common planes perpendicular to the mirror surface13are arranged in three rows at a predetermined pitch parallel to a direction perpendicular to those planes. Moreover, the points of intersection of the optical axes of each of the angular cores11are arranged into a 2 by 3 matrix shape (two-dimensionally) on the mirror surface13.

Moreover, the mirror surface13is formed into a flat surface at an angle of 45 degrees to the optical axes of the angular cores11(mirror angle θ). The first and second end surfaces12aand12bare formed into flat surfaces each at an angle of 90 degrees to the optical axes of the angular cores11.

Furthermore, glasses having different indices of refraction from each other are used in the angular cores11and the device cladding12, respectively. The glass used in the angular cores11has a higher index of refraction than the glass in the device cladding12, the difference between the indices of refraction of the two being 0.1 to 1.0 percent.

An optical path changing operation in the optical path changing device10constructed in this manner will now be explained with reference to FIG.2.

Light14enters the first core end surface11aof an angular core11from the first end surface12aof the optical path changing device10. Because the index of refraction of the angular core11is greater than the index of refraction of the device cladding12, the light14travels inside the angular core11with low loss and reaches the mirror surface13. Then, the light14is reflected by the mirror surface13, has its optical path changed by 90 degrees, travels inside the angular core11with low loss, and is emitted from the second core end surface11bof the angular core11. Thus, the optical path of the light14is changed by 90 degrees by the optical path changing device10.

Moreover, when light14enters the second core end surface11bof the angular core11from the second end surface12bof the optical path changing device10, it similarly has its optical path changed by 90 degrees, and is emitted from the first core end surface11aof the angular core11.

Next, an optical coupling construction using this optical path changing device10will be explained with reference to FIG.3.

InFIG. 3, in an arrayed optoelectronic converting component unit20, optoelectronic converting components21composed of light-emitting components such as surface-emitting lasers (VCSELs), end-emitting lasers or laser diodes (LDs), etc., or light-receiving components such as photo diodes (PDs), etc., are appropriately selected according to desired specifications, arranged two-dimensionally, and mounted on a substrate22. In this case, six optoelectronic converting components21are arranged in a 2 by 3 matrix with an array pitch equivalent to the first core end surfaces11aof the angular cores11in the optical path changing device10.

An arrayed optical waveguide unit25is prepared by embedding waveguide cores26having a rectangular cross section constituting optical waveguides in a waveguide cladding27so as to be arranged into a 2 by 3 matrix with the optical axes thereof parallel. The array pitch of the waveguide cores26in this arrayed optical waveguide unit25is configured so as to be equal to the array pitch of the second core end surfaces11bof the angular cores11in the optical path changing device10. First and second end surfaces of the arrayed optical waveguide unit25in the longitudinal direction of the waveguide cores26are formed into flat surfaces at an angle of 90 degrees to the optical axes of the waveguide cores26. Here, fluorinated polyimides, for example, are used as the materials for the waveguide cores26and the waveguide cladding27. The fluorinated polyimide used in the waveguide cores26has a higher index of refraction than the fluorinated polyimide in the waveguide cladding27. The difference between the indices of refraction of the two is 0.1 to 1.0 percent.

This optical path changing device10is disposed in close contact with the arrayed optoelectronic converting component unit20such that the optical axes of the first core end surfaces11aof the angular cores11are each aligned with centers of component surfaces of the optoelectronic converting components21. The arrayed optical waveguide unit25is disposed in close contact with the optical path changing device10such that the optical axes of each of the waveguide cores26align with the optical axes of the second core end surfaces11bof each of the angular cores11.

Thus, if the optoelectronic converting components21are light-emitting components, light emitted from the optoelectronic converting components21has its optical path changed by 90 degrees by the optical path changing device10, and enters the waveguide cores26from the first end of the arrayed optical waveguide unit25. Because the index of refraction of the waveguide cores26is greater than the index of refraction of the waveguide cladding27, the light14travels inside the waveguide cores26with low loss and is emitted from the second end of the arrayed optical waveguide unit25.

On the other hand, if the optoelectronic converting components21are light-receiving components, light entering the waveguide cores26from the second end of the arrayed optical waveguide unit25enters the angular cores11from the second core end surfaces11b.Then, the light has its optical path changed by 90 degrees by the optical path changing device10, and exits from the first core end surfaces11a,and is received by the optoelectronic converting components21.

Next, a packaging example for the optical coupling construction shown inFIG. 3will be explained based on FIG.4.

An integrated circuit (IC)16and the arrayed optoelectronic converting component unit20are mounted to a substrate17by means of solder bumps or wire bonding. The optical path changing device10and the arrayed optical waveguide unit25are mounted on an electrical circuit board19such that the cores11and26align with each other. Next, the optical coupling construction shown inFIG. 3is achieved by mounting the substrate17on the electrical circuit board19by means of solder balls18such that the optoelectronic converting components21align with the first core end surfaces11aof the angular cores11of the optical path changing device10.

Then, for example, the optical coupling construction is incorporated into an optical communication system, a massively parallel computer, etc., by connecting the waveguide cores26of the arrayed optical waveguide unit25to optical devices such as optical switches, multiplexers, branching filters, etc., by means of optical connectors, etc.

Now, inFIG. 4, the arrayed optoelectronic converting component unit20is fixed to the substrate17, but the arrayed optoelectronic converting component unit20may also be mounted (fixed) to the optical path changing device10.

Furthermore, the arrayed optoelectronic converting component unit20is electrically connected to the substrate17by means of solder bumps, wire bonding, etc., but an electrically-conductive adhesive, a pin-grid array (PGA), a land-grid array (LGA), etc., may also be used to connect the two.

Gaps between the arrayed optoelectronic converting component unit20and the optical path changing device10, gaps between the arrayed optical waveguide unit25and the optical path changing device10, etc., are generally occupied by air, but these gaps may also be filled with a material having low propagation loss at service wavelengths, for example, a resin such as a fluorinated polyimide, a polymethyl methacrylate (PMMA), a silicone resin, an epoxy resin, etc., enabling the cores11and26to be optically coupled efficiently.

The arrayed optical waveguide unit25can be fixed to the electrical circuit board19using an adhesive such as a fluorinated polyimide, a polymethyl methacrylate, a silicone resin, an epoxy resin, etc., for example, but the arrayed optical waveguide unit25may also be fixed to the optical path changing device10using a positioning frame body, guide pins, etc.

Thus, according to Embodiment 1, the angular cores11constituting optical waveguides are embedded in the device cladding12so as to be arranged into a 2 by 3 matrix shape, and the optical-path-changing mirror surface13is formed integrally with the device cladding12.

Thus, the need for conventional micromirrored optical pins5and through holes3into which the optical pins5are inserted is eliminated, simplifying the manufacturing process and enabling cost reductions, as well as also eliminating deterioration in optical coupling efficiency resulting from irregularities on the inner wall surfaces of the through holes3.

Because the angular cores11can be prepared into the matrix-shaped arrangement with high positioning accuracy, optical axis misalignment is less likely to occur between optoelectronic converting components21(or waveguide cores26) arranged into a matrix shape and the angular cores11, suppressing deterioration in optical coupling efficiency.

Furthermore, optical components arranged into a matrix shape can be optically coupled to each other by a single optical path changing device, simplifying construction and enabling cost reductions.

Because the angular cores11are contiguous before and after the mirror surface13, propagating light can be adequately enclosed, enabling loss to be reduced.

Because the angular cores11are embedded in the device cladding12, the occurrence of buckling of the cores resulting from the lengthening of the angular cores11is significantly reduced compared to the buckling occurring in the separate optical pins5in the conventional technique. As a result, even if the angular cores11are arranged into a 2 by 3 matrix shape, there is no deterioration in the positioning accuracy of the angular cores11, significantly suppressing deterioration in optical coupling efficiency.

Because the optical path changing device10is an integrated block body, optical coupling between components such as the arrayed optoelectronic converting component unit20, the arrayed optical waveguide unit25, etc., and the optical path changing device10can be performed accurately by a simple and convenient method.

Now, in Embodiment 1 above, the mirror surface13, which is a flat surface, is prepared by removing a portion of the device cladding12, but gold, or a multilayer film, etc., having a high reflectance may also be coated onto the mirror surface13. In that case, reflectance at the mirror surface13is improved, suppressing deterioration due to loss. A photoselectively permeable film may also be coated onto the mirror surface13. In that case, a filtering function is imparted to the mirror surface13, whereby only light of a predetermined wavelength is allowed to pass through the mirror surface13and enter another optical waveguide, enabling expansion of the intended uses.

Moreover, in Embodiment 1 above, the first and second core end surfaces11aand11bof the angular cores11are arranged into a 2 by 3 matrix shape, but the first and second core end surfaces11aand11bare not limited to this arrangement and can be appropriately set to match the arrangement of the optoelectronic converting elements21or the arrangement of the waveguide cores26, etc. Furthermore, the array pitch of the first and second core end surfaces11aand11bdoes not have to be a uniform pitch and can be appropriately set to match the arrangement of the optoelectronic converting elements21or the waveguide cores26. In addition, the first and second core end surfaces11aand11bdo not necessarily have to be arranged into a complete 2 by 3 matrix shape and, for example, two core end surfaces in any given column may also be offset in a row direction relative to the core end surfaces in other columns, or one or three or more core end surfaces may also be disposed in any given column, etc.

Furthermore, the mirror angle θ is designated as 45 degrees, but the mirror angle θ is not limited to 45 degrees and if set appropriately, the angle of change in the optical path can be adjusted arbitrarily.

It goes without saying that the mode which propagates inside the cores11and26may be either a single mode or a multimode.

Furthermore, in Embodiment 1 above, glasses such as silica glasses, oxide glasses, halide glasses, etc., are used as the material for the angular cores11and the device cladding12, but the angular cores11and the device cladding12are not limited to these materials provided that they are a low-loss material with respect to propagation loss, and for example, fluorinated polyimides, polymethyl methacrylates, silicone resins, epoxy resins, etc., can be used. The difference between the indices of refraction of the angular cores11and the device cladding12is approximately 0.1 to 1.0 percent, but it goes without saying that this may be appropriately changed depending on the intended use.

The wavelengths able to be handled by the optoelectronic converting components21are generally 0.85 μm, 1.3 μm, and 1.55 μm but are not limited to these; any wavelength can be used as required.

Furthermore, a plurality of wavelengths may also be handled by utilizing wavelength characteristics of the optoelectronic converting elements21. In that case, cross talk between the light propagating through adjacent cores11and26can be suppressed.

The waveguide cores26and the waveguide cladding27in the arrayed optical waveguide unit25are not limited to fluorinated polyimides provided that the index of refraction required for the propagation of light is achieved and the materials have low loss relative to the propagated wavelengths. For example, glasses such as silica glasses, oxide glasses, halide glasses, etc., polymethyl methacrylates, silicone resins, epoxy resins, etc., can be used. The difference between the indices of refraction of the waveguide cores26and the waveguide cladding27is approximately 0.1 to 1.0 percent, but it goes without saying that this may be appropriately changed depending on the intended use.

Furthermore, the arrayed optical waveguide unit25is constructed by embedding the waveguide cores26in the waveguide cladding27, but an arrayed optical waveguide unit may also be constructed by bundling a plurality of optical fibers in which a core and a cladding are prepared integrally.

In Embodiment 2, as shown inFIG. 5, a second mirror surface13afor which the mirror angle θ is 45 degrees is formed between the mirror surface13and the second end surface12b.

In an optical path changing device10A prepared in this manner, the optical path can be changed by 180 degrees.

Moreover, in Embodiment 2, the angle of change in the optical path can also be adjusted arbitrarily by setting the mirror angle θ appropriately.

In Embodiment 3, as shown inFIG. 6, a second mirror surface13bfor which the mirror angle θ is 45 degrees is formed between the mirror surface13and the second end surface12b.

In an optical path changing device10B prepared in this manner, the optical path can be changed in a zigzag or Z-shape (a 0-degree change).

Moreover, in Embodiment 3, the angle of change in the optical path can also be adjusted arbitrarily by setting the mirror angle θ appropriately.

FIG. 7is a schematic diagram showing a packaging construction using an optical path changing device according to Embodiment 4 of the present invention.

In Embodiment 4, as shown inFIG. 7, an optical coupling construction for coupling between arrayed optoelectronic converting component units20mounted to different substrates17is achieved by combining optical path changing devices10and arrayed optical waveguide units25.

Consequently, this optical path changing device10can be applied to optical coupling between arrayed optoelectronic converting component units20and the arrayed optical waveguide unit25, and also to optical coupling between arrayed optical waveguide units25.

FIG. 8is a schematic diagram showing a packaging construction using an optical path changing device according to Embodiment 5 of the present invention.

In Embodiment 5, as shown inFIG. 8, an optical coupling construction for coupling between arrayed optoelectronic converting component units20mounted to different substrates17is achieved by an optical path changing device10A.

Consequently, this optical path changing device10A can be applied to optical coupling between arrayed optoelectronic converting component units20.

FIGS. 9Ato9D are process diagrams explaining a method for manufacturing an optical path changing device according to Embodiment 6 of the present invention.

A method for manufacturing an optical path changing device using quartzes for the core and cladding materials will now be explained.

First, as shown inFIG. 9A, a thin, flat substrate30is prepared using a silica glass having a low index of refraction. Next, a quartz having a high index of refraction is formed into a film on the substrate30to a predetermined thickness using a vacuum film-formation technique such as sputtering, etc. Then, a photoresist is applied onto the quartz film having a high index of refraction, the photoresist is patterned using a photoengraving technique, and then unwanted portions of the quartz film are removed by means of reactive ion etching (RIE). Next, two pairs of first and second core segments31aand31bmade of the quartz film having a high index of refraction formed on a common plane are obtained by removing the photoresist. The pair of first core segments31aare formed into straight, parallel lines, the pair of second core segments31bare formed into straight, parallel lines, and the first core segments31aand the second core segments31bare perpendicular to each other. Moreover, intersecting portions of the first and second core segments31aand31bare positioned in a straight line and correspond to return portions of the angular cores11.

Next, the quartz having a low index of refraction is formed into a film on the substrate30to a predetermined thickness using a vacuum film-formation technique such as sputtering, etc. Thus, as shown inFIG. 9B, a waveguide body32is obtained in which the first and second core segments31aand31bare embedded in the quartz having a low index of refraction (a cladding).

Next, a waveguide unit33is obtained by superposing a plurality of these waveguide bodies32with the first and second core segments31aand31baligned as shown inFIG. 9C, and fixing together the superposed waveguide bodies32.

An optical path changing device is then obtained by forming a mirror surface34by cutting and removing a portion of the waveguide unit33together with a portion of the intersecting portions of the first and second core segments31aand31bby dicing as shown in FIG.9D. Moreover, the mirror surface34is formed so as to pass through the points of intersection between the optical axes of the first core segments31aand the optical axes of the second core segments31b.

In the optical path changing device prepared in this manner, the first core segments31aand the second core segments31bare returned at the mirror surface34to constitute continuous angular cores11, the quartz having a low index of refraction constitutes the device cladding12, and the mirror surface34constitutes the mirror surface13.

Each of the angular cores11is formed such that a first core segment31aextending from the first core end surface11ato the mirror surface13(34) and a second core segment31bextending from the second core end surface11bto the mirror surface13(34) intersect at the mirror surface13(34) and are symmetrical relative to a line perpendicular to the mirror surface13(34) at their point of intersection. Eight angular cores11are configured such that pairs of angular cores11arranged parallel to each other on common planes perpendicular to the mirror surface13(34) are arranged in four rows parallel to a direction perpendicular to those planes (a direction of lamination). Furthermore, the first core end surfaces11aand the second core end surfaces11bare each arranged into a2by4matrix shape at the first end surface12aand the second end surface12b,respectively.

In the manufacturing method according to Embodiment 6, because the angular cores11are prepared by a combination of photoengraving techniques and reactive ion etching, positioning accuracy of the angular cores11is ensured, enabling optical coupling efficiency in optical coupling with optoelectronic converting elements21and waveguide cores26to be increased.

Furthermore, because a plurality of the first and second core segments31aand31bcan be prepared in the waveguide bodies32, cost reductions are enabled.

Moreover, in Embodiment 6 above, the mirror surface34is prepared by cutting the waveguide unit33by dicing, but the flatness of the mirror surface34may also be increased by performing polishing after dicing. In addition, a mirror surface may also be formed by means of reactive ion etching, polishing, etc., instead of dicing.

Furthermore, in Embodiment 6 above, the core segments are formed by etching after forming a quartz film having a high index of refraction, but core segments prepared into a predetermined shape beforehand may also be fixed onto the substrate30.

In Embodiment 6 above, if three each of the first and second core segments31aand31bare prepared in just one of the waveguide bodies32, a two-dimensional arrangement can be obtained in which just one column has three rows of first and second core end surfaces11aand11b.In that case, it is necessary for the three sets of first and second core segments31aand31bto be formed on the waveguide body32such that the points of intersection of the optical axes of the first and second core segments31aand31bconstituting the angular cores11are arranged in a straight line. Furthermore, if one each of the first and second core segments31aand31bare prepared in just one of the waveguide bodies32, a two-dimensional arrangement can be obtained in which just one column has one row of first and second core end surfaces11aand11b.

In Embodiment 6 above, if four waveguide bodies32are alternately offset and fixed together, a two-dimensional arrangement is obtained in which the first and second core end surfaces11aand11bare arranged into a zigzag pattern. In that case, it is necessary for the waveguide bodies32to be laminated in such a way that straight lines passing through the points of intersection of the optical axes of the first and second core segments31aand31bconstituting the angular cores11in each of the waveguide bodies32are superposed in the direction of lamination of the waveguide bodies32.

In Embodiment 6 above, the mirror surface34is prepared after fixing the waveguide bodies32together, but in Embodiment 7, mirror surfaces are formed at a stage when substrates are prepared.

A method for manufacturing an optical path changing device according to Embodiment 7 of the present invention will now be explained with reference toFIGS. 10Ato10D.

First, as shown inFIG. 10A, a thin, flat substrate30A on which a mirror surface34ais formed is prepared using a silica glass having a low index of refraction. Next, a quartz having a high index of refraction is formed into a film on the substrate30A to a predetermined thickness using a vacuum film-formation technique such as sputtering, etc. Then, a photoresist is applied onto the quartz film having a high index of refraction, the photoresist is patterned using a photoengraving technique, and then unwanted portions of the quartz film are removed by means of reactive ion etching (RIE). Next, two pairs of first and second core segments31aand31bmade of the quartz film having a high index of refraction formed on a common plane are obtained by removing the photoresist. The pair of first core segments31aare formed into straight, parallel lines, the pair of second core segments31bare formed into straight, parallel lines, and the first core segments31aand the second core segments31bare perpendicular to each other at the mirror surface34a.

Next, the quartz having a low index of refraction is formed into a film on the substrate30A to a predetermined thickness using a vacuum film-formation technique such as sputtering, etc. Thus, as shown inFIG. 10B, a waveguide body32A is obtained in which the first and second core segments31aand31bare embedded in the quartz having a low index of refraction (a cladding).

Next, a waveguide unit33is obtained by superposing a plurality of these waveguide bodies32A with the mirror surfaces34aaligned as shown inFIG. 10C, and fixing together the superposed waveguide bodies32A. Thus, an optical path changing device such as shown inFIG. 10Dis obtained. Moreover, the mirror surface34is constituted by the mirror surfaces34a,being formed so as to pass through the points of intersection between the optical axes of the first core segments31aand the optical axes of the second core segments31b.

Thus, an optical path changing device similar to that in Embodiment 6 above is also manufactured in Embodiment 7.

Embodiment 6 above has been explained for a construction using quartzes constituting inorganic materials as the materials for the cores and the cladding, but in Embodiment 8, fluorinated polyimides constituting organic materials are used as materials for cores and cladding.

First, a first fluorinated polyimide solution having a low index of refraction is spin-coated onto a quartz substrate and is baked to form a first cladding layer. Next, a second fluorinated polyimide solution having a high index of refraction is spin-coated and baked to form a core layer on the first cladding layer.

Then, a photoresist is applied onto the core layer, the photoresist is patterned by a photoengraving technique, and then unwanted portions of the core layer are removed by means of reactive ion etching. Then, core segments made of the core layer are obtained by removing the photoresist. Next, the first fluorinated polyimide solution is spin-coated and baked to form a second cladding layer.

Thus, a waveguide body (corresponding to the waveguide body32described above) is obtained in which core segments are embedded in a first and second cladding layer. Moreover, the core segments are constructed in a similar manner to the core segments31aand31bin Embodiment 6 above. Thereafter, a waveguide unit is prepared by laminating and fixing together a plurality of these waveguide bodies in a similar manner to Embodiment 6 above, and a mirror surface is formed to obtain an optical path changing device.

Consequently, similar effects to those in Embodiment 6 above can also be achieved in Embodiment 8.

Moreover, in Embodiment 8, fluorinated polyimides are used for the core and cladding materials, but this manufacturing method can also be applied when polymethyl methacrylates, silicone resins, epoxy resins, etc., are used for the core and cladding materials.

Furthermore, in Embodiment 8 above, the core layer is patterned by reactive ion etching, but if the second fluorinated polyimide solution is imparted with photocuring properties, the core layer can be patterned by a photoengraving technique alone, enabling simplification of the manufacturing process.

In Embodiment 8 above, the mirror surface is prepared after fixing the waveguide bodies together, but mirror surfaces may also be formed in advance on the substrates to which the first and second fluorinated polyimide solutions are applied in a similar manner to Embodiment 7 above.

Furthermore, in Embodiment 8 above, the core segments are formed by etching after forming the core layer by applying and hardening the second fluorinated polyimide solution, but core segments prepared into a predetermined shape beforehand may also be fixed onto the first cladding layer.

FIGS. 11Ato11D are process diagrams explaining a method for manufacturing an optical path changing device according to Embodiment 9 of the present invention, andFIG. 12is a diagram explaining a core formation method.

A method for manufacturing an optical path changing device using halide glasses for the core and cladding materials will now be explained.

First, as shown inFIG. 11A, a flat substrate40made of a halide glass is prepared.

Next, as shown inFIG. 12, an 810-nm laser beam emitted by a laser generating apparatus38is condensed by a condenser lens39, and is focused at a predetermined depth position in the substrate40with an energy of 100 MJ/cm2. At this time, one first core segment41bis formed at the position where the laser beam condenses inside the substrate40by moving the substrate40in the direction of the arrow in FIG.12. After forming one first core segment41b,the substrate40is shifted in a direction perpendicular to that first core segment41bby a predetermined amount, and another first core segment41bis formed while moving the substrate40in a similar manner. Three first core segments41bformed in this manner so as to be arranged parallel to each other on a common plane inside the substrate40.

Next, the depth of the condensing position of the condenser lens39inside the substrate40is reduced by a predetermined amount, and three more first core segments41bformed in a similar manner inside the substrate40so as to be arranged parallel to each other. Thus, as shown inFIG. 11B, a substrate40(a waveguide body) is obtained in which six first core segments41barranged in 3 columns and 2 layers.

Next, the position of the substrate40is rotated by 90 degrees, and six second core segments41aare formed inside the substrate40so as to be arranged in 3 columns and 2 layers using the laser generating apparatus38and the condenser lens39in a similar manner. Thus, as shown inFIG. 11C, a substrate40(a waveguide body) is obtained in which second core segments41aand first core segments41bformed so as to intersect at right angles to each other. Moreover, intersecting portions between corresponding second core segments41aand first core segments41bare all positioned on a common plane.

Then, an optical path changing device is obtained by forming a mirror surface42by cutting and removing a portion of the substrate40together with a portion of the intersecting portions of the first and second core segments41band41aby dicing as shown in FIG.11D. This mirror surface42is formed so as to pass through the points of intersection between the optical axes of the second core segments41aand the optical axes of the first core segments41b.

In the optical path changing device prepared in this manner, the second core segments41aand the first core segments41breturned at the mirror surface42to constitute angular cores11, the substrate4constitutes the device cladding12, and the mirror surface42constitutes the mirror surface13.

Each of the angular cores11is formed such that a second core segment41aextending from the first core end surface11ato the mirror surface13(42) and a first core segment41bextending from the second core end surface11bto the mirror surface13(42) intersect at the mirror surface13(42) and are symmetrical relative to a line perpendicular to the mirror surface13(42) at their point of intersection. The angular cores11are configured such that pairs of angular cores11arranged parallel to each other on common planes perpendicular to the mirror surface13(42) are arranged in three rows parallel to a direction perpendicular to those planes.

In the manufacturing method according to Embodiment 9, core segments41aand41bprepared by causing a change in the index of refraction inside the substrate40by condensing and focusing a laser beam on the substrate40using a laser generating apparatus38and a condenser lens39. Thus, compared to Embodiments 6 to 8 above, a process for fixing together the waveguide bodies32and32A is no longer necessary, simplifying the manufacturing process and enabling cost reductions.

Furthermore, in the manufacturing methods according to Embodiments 6 to 8 above, the cores are formed with a rectangular cross section, but in Embodiment 9, because cores having a circular cross section can be formed, loss during propagation is reduced, enabling optical coupling to be performed efficiently.

Moreover, in Embodiment 9 above, a halide glass is used for the substrate40, but the material for the substrate is not limited to a halide glass, and for example, an oxide glass, a silica glass, etc., can be used provided that a change in the index of refraction can be brought about by optical irradiation.

Moreover, in Embodiment 9 above, the mirror surface42is prepared by cutting the substrate40by dicing, but the flatness of the mirror surface42may also be increased by performing polishing after dicing. In addition, a mirror surface may also be formed by means of reactive ion etching, polishing, etc., instead of dicing.

Furthermore, in Embodiment 9 above, core segments41band41aarranged into 3 columns and 2 layers are formed inside the substrate40by optical irradiation, but second core segments41aarranged into 3 columns and 2 layers may also be formed inside the substrate40by optical irradiation after preparing a substrate40in which first core segments41barranged into3columns and 2 layers by another method. Here, the substrate40in which first core segments41barranged into 3 columns and 2 layers can be obtained, for example, by forming three recessed grooves in the substrate40, housing two quartz waveguides, optical fibers, etc., inside each of the recessed grooves, and then integrating them by filling the inside of the recessed grooves with an adhesive such as a fluorinated polyimide, etc.

In Embodiment 9 above, the mirror surface42is prepared on the substrate40formed with the core segments41aand41b,but in Embodiment 10, the mirror surface42is formed on the substrate40A before formation of the core segments41aand41b.

A method for manufacturing an optical path changing device according to Embodiment 10 of the present invention will now be explained with reference toFIGS. 13Ato13C.

First, as shown inFIG. 13A, a flat substrate40A on which a mirror surface42is formed is prepared using a halide glass.

Next, an 810-nm laser beam emitted by a laser generating apparatus38is condensed by a condenser lens39, and is focused at a predetermined depth position in the substrate40A with an energy of 100 MJ/cm2. At this time, one first core segment41bis formed at the position where the laser beam condenses inside the substrate40A by moving the substrate40A in the direction of the arrow in FIG.12. After forming one first core segment41b,the substrate40A is shifted in a direction perpendicular to that first core segment41bby a predetermined amount, and another first core segment41bis formed while moving the substrate40A in a similar manner. In this manner, a substrate40A (a waveguide body) is obtained in which three first core segments41bformed so as to be arranged parallel to each other on a common plane.

Next, the depth of the condensing position of the condenser lens39inside the substrate40A is reduced by a predetermined amount, and three more first core segments41bformed in a similar manner inside the substrate40A so as to be arranged parallel to each other. Thus, as shown inFIG. 13B, a substrate40A (a waveguide body) is obtained in which six first core segments41barranged in 3 columns and 2 layers.

Next, the position of the substrate40A is rotated by 90 degrees, and six second core segments41aare formed inside the substrate40A using the laser generating apparatus38and the condenser lens39in a similar manner so as to be arranged in 3 columns and 2 layers. As shown inFIG. 13C, optical axes of each of the second core segments41aare formed so as to intersect at right angles to optical axes of the corresponding first core segments41bat the mirror surface42.

Thus, an optical path changing device is obtained. Moreover, the mirror surface42is formed so as to pass through the points of intersection between the optical axes of the second core segments41aand the optical axes of the first core segments41b.

Thus, an optical path changing device similar to that in Embodiment 9 above is also manufactured in Embodiment 10.

FIG. 14is a side elevation showing an optical path changing device according to Embodiment 11 of the present invention.

In an optical path changing device10C according to Embodiment 11, optical path cross sections of angular cores45are formed so as to enlarge gradually from the mirror surface13toward first core end surfaces45a.

Moreover, the rest of this embodiment is constructed in a similar manner to Embodiment 1 above.

According to Embodiment 11, because the optical path cross sections of the angular cores45are formed so as to enlarge gradually from the mirror surface13toward the first core end surfaces45a,the cross-sectional area of the first core end surfaces45ais increased, easing positioning accuracy between the optoelectronic converting elements21and the optical path changing device10C and between the waveguide cores26and the optical path changing device10C when the first core end surfaces45aare used as insertion end surfaces.

Moreover, adjustment of the optical path cross sections of the angular cores45can easily be achieved by changing mask shapes during reactive ion etching, changing the method of condensing the laser, etc.

In Embodiment 11 above, the optical path cross sections of the angular cores45are formed so as to enlarge gradually over an entire region extending from the mirror surface13to the first core end surfaces45a,but the optical path cross sections of the angular cores45may also be formed so as to enlarge gradually toward the first core end surfaces45aat least in a vicinity of the first core end surfaces45awith the cross-sectional areas of the first core end surfaces45amaximized.

Furthermore, in Embodiment 11 above, the optical path cross sections of the angular cores45are formed so as to enlarge gradually from the mirror surface13toward the first core end surfaces45a,but the optical path cross sections of the angular cores45may also be formed so as to enlarge gradually from the mirror surface13toward second core end surfaces45b.

FIG. 15is a side elevation showing an optical path changing device according to Embodiment 12 of the present invention.

In an optical path changing device10D according to Embodiment 12, optical path cross sections of angular cores46are formed so as to reduce gradually from the mirror surface13toward first core end surfaces46a.

Moreover, the rest of this embodiment is constructed in a similar manner to Embodiment 11 above.

According to Embodiment 12 , because the optical path cross sections of the angular cores46are formed so as to reduce gradually from the mirror surface13toward the first core end surfaces46a,the cross-sectional area of the first core end surfaces46ais reduced, easing positioning accuracy between the optoelectronic converting elements21and the optical path changing device10D and between the waveguide cores26and the optical path changing device10D when the first core end surfaces46aare used as emission end surfaces.

Moreover, in Embodiment 12 above, the optical path cross sections of the angular cores46are formed so as to reduce gradually over an entire region extending from the mirror surface13to the first core end surfaces46a,but the optical path cross sections of the angular cores46may also be formed so as to reduce gradually toward the first core end surfaces46aat least in a vicinity of the first core end surfaces46awith the cross-sectional areas of the first core end surfaces46aminimized.

Furthermore, in Embodiment 12 above, the optical path cross sections of the angular cores46are formed so as to reduce gradually from the mirror surface13toward the first core end surfaces46a,but the optical path cross sections of the angular cores46may also be formed so as to reduce gradually from the mirror surface13toward second core end surfaces46b.

FIG. 16is a side elevation showing an optical path changing device according to Embodiment 13 of the present invention.

In an optical path changing device10E according to Embodiment 13, branch cores48aand48bformed so as to branch off from an intermediate portion of an angular core47between the second end surface12band the mirror surface13and be exposed at the second end surface12b.

Moreover, the rest of this embodiment is constructed in a similar manner to Embodiment 1 above.

According to Embodiment 13, because the angular core47branches off into the two branch cores48aand48b,two beams of light can be combined into a single beam of light and emitted, or a single beam of light can be split into two beams of light and emitted, etc., enabling the intended uses to be expanded.

Moreover, in this case, the number of first core end surfaces47aarranged two-dimensionally at the first end surface12aof the optical path changing device10E and the number of second core end surfaces47barranged two-dimensionally at the second end surface12bis different.

Furthermore, the number of branching angular cores47is appropriately set to match desired optical coupling specifications. They may also branch off from an intermediate portion of an angular core47between the first end surface12aand the mirror surface13and be exposed at the first end surface12a.

If a light filter is formed in the branch cores48aand48b,light can be passed through the branch cores48aand48bselectively. In addition, if a thermo-optic switch is disposed in the branch cores48aand48b,the optical path can be switched selectively.

The present invention is constructed in the above manner and exhibits the effects described below.

As explained above, according to one aspect of the present invention, there is provided an optical path changing device including:

a cladding formed with a first end surface, a second end surface, and a mirror surface; and

at least three cores embedded in the cladding, each core constituting a continuous optical path in which a first core end surface is exposed at the first end surface and a second core end surface is exposed at the second end surface, each of the continuous optical paths extending from the first core end surface to the mirror surface, being changed in direction at the mirror surface, and extending to the second core end surface,

wherein the first core end surfaces and the second core end surfaces are arranged two-dimensionally at the first end surface and the second end surface, respectively,

enabling an optical path changing device having high optical coupling efficiency to be obtained at low cost.

An optical path cross-sectional area of at least one of the cores may also be constructed so as to increase gradually in a direction away from the mirror surface toward the first end surface at least in a vicinity of the first core end surface, facilitating positioning accuracy with parts to be optically coupled when the first end surface is used as an insertion end surface.

An optical path cross-sectional area of at least one of the cores may also be constructed so as to decrease gradually in a direction away from the mirror surface toward the first end surface at least in a vicinity of the first core end surface, facilitating positioning accuracy with parts to be optically coupled when the first end surface is used as an emission end surface.

At least one of the cores may also be provided with a branch core branching off from an intermediate portion between the mirror surface and the first end surface, the branch core being exposed at the first end surface, enabling light beam combination or splitting to be achieved easily.

A second mirror surface may also be formed on the cladding between the mirror surface and the second end surface so as to change a direction of an optical path of the cores, enabling adaptation to complicated optical path changing.

According to yet another aspect of the present invention, there is provided a method for manufacturing an optical path changing device, the method including the steps of:

preparing a first waveguide body in which at least one pair of first and second core segments formed such that optical axes of the pair of first and second core segments intersect at an intersecting portion is embedded in a first cladding such that the pair of first and second core segments are arranged on a common plane with the intersecting portion of the optical axes positioned on a first straight line;

preparing a second waveguide body in which at least two pairs of first and second core segments formed such that optical axes of each of the pairs of first and second core segments intersect at an intersecting portion are embedded in a second cladding such that the pairs of first and second core segments are arranged on a common plane with the intersecting portions of the optical axes positioned on a second straight line;

preparing a waveguide unit by laminating the first and second waveguide bodies such that the first and second straight lines are superposed in a direction of lamination, and then fixing together the first and second waveguide bodies; and

forming an optical-path-changing mirror surface at the intersecting portions of the pairs of first and second core segments by removing a portion of the first and second claddings in the waveguide unit on a plane including the intersecting portions of the optical axes of the pairs of first and second core segments together with a portion of the intersecting portions of the pairs of first and second core segments such that each of the pairs of first and second core segments forms an angular core having a return portion at the mirror surface, thereby providing a method for manufacturing an optical path changing device enabling an optical path changing device having high optical coupling efficiency to be manufactured inexpensively.

According to another aspect of the present invention, there is provided a method for manufacturing an optical path changing device, the method including the steps of:

preparing a first waveguide body in which at least one angular core composed of a pair of first and second core segments formed into an angular shape such that optical axes of the pair of first and second core segments intersect at an intersecting portion is embedded in a first substrate made of a first cladding formed with a mirror surface such that the pair of first and second core segments are arranged on a common plane perpendicular to the mirror surface with the intersecting portion of the optical axes positioned at the mirror surface;

preparing a second waveguide body in which at least two angular cores each composed of a pair of first and second core segments formed into an angular shape such that optical axes of each of the pairs of first and second core segments intersect at an intersecting portion are embedded in a second substrate made of a second cladding formed with a mirror surface such that the pairs of first and second core segments are arranged on a common plane perpendicular to the mirror surface with the intersecting portions of the optical axes positioned at the mirror surface; and

integrating the first and second waveguide bodies by laminating the first and second waveguide bodies such that the mirror surfaces are superposed in a direction of lamination, and then fixing together the first and second waveguide bodies, thereby providing a method for manufacturing an optical path changing device enabling an optical path changing device having high optical coupling efficiency to be manufactured inexpensively.

According to yet another aspect of the present invention, there is provided a method for manufacturing an optical path changing device, the method including the steps of:

preparing a waveguide body having a first end surface and a second end surface in which a plurality of first core segments are embedded inside a cladding such that core end surfaces of the first core segments are arranged two-dimensionally at the first end surface;

forming second core segments inside the cladding by condensing and focusing a laser on the cladding of the waveguide body such that core end surfaces of the second core segments are arranged two-dimensionally at the second end surface, optical axes of each of the second core segments intersect optical axes of corresponding first core segments at intersecting portions, and the intersecting portions of the optical axes are positioned on a common plane; and

forming an optical-path-changing mirror surface at the plane on which the intersecting portions of the optical axes are positioned by removing a portion of the cladding of the waveguide body together with a portion of the first and second core segments such that each of the pairs of first and second core segments forms an angular core having a return portion at the mirror surface, thereby providing a method for manufacturing an optical path changing device enabling an optical path changing device having high optical coupling efficiency to be manufactured inexpensively.

According to yet another aspect of the present invention, there is provided a method for manufacturing an optical path changing device, the method including the steps of:

preparing a waveguide body having a first end surface, a second end surface, and a mirror surface in which a plurality of first core segments are embedded inside a cladding so as to extend from the first end surface to the mirror surface such that core end surfaces of the first core segments are arranged two-dimensionally at the first end surface; and

forming second core segments inside the cladding by condensing and focusing a laser on the cladding of the waveguide body such that core end surfaces of the second core segments are arranged two-dimensionally at the second end surface and optical axes of each of the second core segments intersect optical axes of corresponding first core segments at the mirror surface such that each of the pairs of first and second core segments forms an angular core having a return portion at the mirror surface, thereby providing a method for manufacturing an optical path changing device enabling an optical path changing device having high optical coupling efficiency to be manufactured inexpensively.

The first core segments may also be formed by condensing and focusing the laser on the cladding of the waveguide body, enabling the first and second core segments to be formed by laser in succession, thereby enabling simplification of the manufacturing process.