Abstract:
Even if there is a temperature variation, a positional discrepancy at a colliding surface of an active surface of a semiconductor laser and an optical waveguide is suppressed, resulting in realization of a semiconductor light emitting element coupled with optical fiber of stable operation. In order to realize the above object, a semiconductor light emitting element coupled with optical fiber comprises a substrate, an optical waveguide disposed on the substrate and including a core and a cladding layer covering the core, a semiconductor light emitting element disposed on the substrate and comprising an output end-surface facing one end of the core of the optical waveguide, and an optical fiber comprising a core an end of which faces the other end of the core of the optical waveguide, wherein the cladding layer sandwiches both surfaces of the semiconductor light emitting element.

Description:
BACKGROUND ART INFORMATION 
     1. Technical Field 
     The present invention relates to a semiconductor light emitting element coupled with optical fiber in which emission of a semiconductor element is outputted from an optical fiber. 
     2. Background Art 
     In optically coupling an edge emitting type semiconductor laser and an optical fiber for instance, optical means such as lens are used in general. The optical means such as lenses or the like can converge a diameter of a broad output beam of a semiconductor laser to a narrow one to enable to enter in the optical fiber with ease. As the result of this, a coupling loss between the semiconductor laser and the optical fiber can be suppressed. 
     However, in optically coupling a semiconductor laser and an optical fiber by use of optical means such as lens or the like, a plurality of lenses are required to be aligned with extremely high precision. Accordingly, an alignment takes a long time to result in increasing manufacturing costs. 
     As the means for annulling complication of the alignment, a method in which an emitting element and a light-propagating medium are directly coupled is disclosed in Japanese Patent Laid-open Publication No. HEI 5-134151. According to the above, a semiconductor laser and an optical waveguide are directly coupled to make unnecessary the complicated alignment, resulting in cost reduction. 
     In the disclosure of the aforementioned reference, however, the semiconductor laser and the optical waveguide are disposed in an intimate contact with each other on the same substrate. As the result of this, the optical waveguide dilates due to the heat of the semiconductor laser to cause the semiconductor laser and the optical waveguide to become off-axis, resulting in the likelihood of lowering light output. 
     Thus, in the existing semiconductor light emitting element coupled with optical fiber, temperature variation may cause a fluctuation of light output. In the case of a semiconductor laser of high output power being broad in an active layer in particular, close attention must be paid on the fluctuation of the light output. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide an semiconductor light emitting element coupled with optical fiber of which variation of light output is small even if there is a temperature variation and that operates with stability. 
     In order to achieve the above object, the present semiconductor light emitting element coupled with optical fiber is constituted in the following ways. 
     (1) A semiconductor light emitting element coupled with optical fiber comprises a substrate, an optical waveguide, a semiconductor light emitting element, and an optical fiber possessing a core of which end faces the other end of the core of the optical waveguide. The optical waveguide is disposed on the substrate and includes a core and a cladding layer covering the core. The semiconductor light emitting element is disposed on the substrate and possesses an outputting end-surface facing one end of a core of the optical waveguide. Here, the cladding layer sandwiches both side surfaces of the semiconductor light emitting element. 
     The cladding layer of the optical waveguide sandwiches both side-surfaces of the semiconductor light emitting element, thereby the semiconductor light emitting element being directly coupled to the optical waveguide. The semiconductor light emitting element being disposed on the substrate, in the neighborhood of an optical coupling (one end of the core of the optical waveguide) of the semiconductor light emitting element and the optical waveguide, the optical waveguide is not necessary to be solidly fixed onto the substrate. Accordingly, in the neighborhood of the optical coupling of the semiconductor light emitting element and the optical waveguide, between the optical waveguide and the substrate a gap can be formed. 
     As a result of this, even in the case where the optical waveguide is heated due to emission from the semiconductor light emitting element to result in dilation, in the neighborhood of the optical coupling with the semiconductor light emitting element, the optical waveguide is not pressed down on the substrate. 
     Accordingly, due to thermal expansion of the optical waveguide relative position between an output terminal of the semiconductor light emitting element and a core of the optical waveguide shifts less. 
     Further, the semiconductor light emitting element and the cladding layer of the optical waveguide being unnecessary to be connected, due to the dilation of the optical waveguide an optical coupling state fluctuates less. 
     As mentioned above, in the semiconductor light emitting element coupled with optical fiber involving the present invention, the temperature variation in the optical waveguide does not disturb a stable light output. 
     (2) A semiconductor light emitting element coupled with optical fiber comprises a substrate, an optical waveguide, a semiconductor light emitting element, and an optical fiber possessing a core of which end faces the other end of the core of the optical waveguide. The optical waveguide is disposed on the substrate and includes a core and a cladding layer covering the core. The semiconductor light emitting element is mounted on a base disposed on the substrate and possesses an output end-surface facing one end of a core of the optical waveguide. Here, the cladding layer sandwiches both side surfaces of the semiconductor light emitting element or the base. 
     The cladding layer of the optical waveguide sandwiches both side-surfaces of the semiconductor light emitting element or the base thereon the semiconductor light emitting element is mounted. Thereby, the semiconductor light emitting element and the optical waveguide are indirectly coupled. Accordingly, similarly with the case (1), a gap can be formed between the optical waveguide and the substrate, and the semiconductor light emitting element and the cladding layer of the optical waveguide are not required to adhere. 
     As a result of this, similarly with the case (1), in the semiconductor light emitting element coupled with optical fiber involving the present invention, the temperature variation does not disturb stable light output. 
     (3) A semiconductor light emitting element coupled with optical fiber comprises a substrate, an optical waveguide, a semiconductor light emitting element, and an optical fiber possessing a core of which an end faces the other end of the core of the optical waveguide. The optical waveguide is disposed on the substrate and includes a core and a cladding layer covering the core. The semiconductor light emitting element is mounted on a base disposed on the substrate and possesses an output end-surface facing one end of a core of the optical waveguide. Here, the cladding layer of the optical waveguide is solidly fixed on an upper surface of the base. 
     The cladding layer of the optical waveguide is solidly fixed on an upper surface of the base thereon the semiconductor light emitting element is mounted. Thereby, the semiconductor light emitting element and the optical waveguide are indirectly coupled. Accordingly, similarly with the case (1), a gap can be formed between the optical waveguide and the substrate, and the semiconductor light emitting element and the cladding layer of the optical waveguide are not required to adhere. 
     As a result of this, similarly with the case (1), in the semiconductor light emitting element coupled with optical fiber involving the present invention, even the temperature variation does not disturb stable light output. 
     (4) A semiconductor light emitting element coupled with optical fiber comprises a substrate, an optical waveguide, a semiconductor light emitting element, and an optical fiber possessing a core of which end faces the other end of the core of the optical waveguide. The optical waveguide is disposed on the substrate and includes a core and a cladding layer covering the core. The semiconductor light emitting element is disposed on the substrate and possesses an output end-surface facing one end of a core of the optical waveguide. Here, the cladding layer of the optical waveguide is solidly fixed on an end-surface of a side that does not face the optical waveguide of the semiconductor light emitting element. 
     The cladding layer of the optical waveguide is solidly fixed to the semiconductor light emitting element, thereby the semiconductor light emitting element is connected to the optical waveguide. Accordingly, similarly with the case (1), a gap can be formed between the optical waveguide and the substrate, resulting in dispensing with adherence of the cladding layer of the semiconductor light emitting element and the optical waveguide. 
     Accordingly, an optical coupling-state between the output end-surface of the semiconductor light emitting element and the core of the optical waveguide is not affected by the thermal expansion of the optical guide, to be constant. As a result of this, the temperature variation in the optical waveguide does not disturb stable light output. 
     (5) A semiconductor light emitting element coupled with optical fiber comprises a substrate, an optical waveguide, a semiconductor light emitting element, and an optical fiber possessing a core of which end faces the other end of the core of the optical waveguide. The optical waveguide is disposed on the substrate and includes a core and a cladding layer covering the core. The semiconductor light emitting element is mounted on a base disposed on the substrate and possesses an output end-surface facing one end of a core of the optical waveguide. Here, the cladding layer of the optical waveguide is solidly fixed to an end-surface of a side thereto the optical waveguide of the base does not face. 
     Accordingly, a gap can be formed between the optical waveguide the substrate, thereby the semiconductor light emitting element and the cladding layer of the optical waveguide being unnecessary to adhere. 
     Accordingly, similarly with the case (4), the temperature variation of the optical waveguide does not disturb stable light output. 
     (6) A semiconductor light emitting element coupled with optical fiber comprises a substrate, an optical waveguide, a semiconductor light emitting element, and an optical fiber possessing a core of which end faces the other end of a core of the optical waveguide. The optical waveguide is disposed on the substrate and includes the core and a cladding layer covering the core. The semiconductor light emitting element is disposed on the substrate and possesses an output end-surface facing one end of the core of the optical waveguide. Here, the optical waveguide is solidly fixed to the substrate in the neighborhood of the other end of the core and possesses a gap between the substrate in the neighborhood of one end of the core. 
     The existence of the gap, between the semiconductor light emitting element and the optical waveguide, decreases a shift of a relative position due to thermal expansion of the optical waveguide. Accordingly, the temperature variation in the optical waveguide does not disturb stable light output. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG.  1 A and FIG. 1B are diagrams of fundamental configuration showing a first embodiment of the present invention, FIG. 1A being a plan view and FIG. 1B being a sectional side view. 
     FIG. 2 is a perspective view showing a state seen from an optical fiber side of an optical waveguide of FIG.  1 . 
     FIG. 3 is a sectional view showing a section of an optical waveguide in FIG.  1 . 
     FIG. 4 is a sectional side view showing a second embodiment of the present invention. 
     FIG. 5 is a partial plan view showing a modification example of a second embodiment of the present invention. 
     FIG. 6 is a sectional side view showing a third embodiment of he present invention. 
     FIG. 7 is a perspective view showing a shape of a substrate in FIG.  6 . 
     FIG. 8 is a plan view showing a fourth embodiment of the present invention. 
     FIG. 9 is sectional side view showing a fifth embodiment of he present invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the following, detailed explanation of embodiments of the present invention will be given with reference to the drawings. 
     (First Embodiment) 
     In from FIG. 1 to FIG. 3, a first embodiment of a semiconductor light emitting element coupled with optical fiber involving the present invention is shown. FIG. 1A is a plan view, FIG. 1B being a sectional side view showing a side cross-section along a line A-A′ of FIG.  1 A. FIG. 2 is a perspective view showing a substantial portion of the semiconductor light emitting element coupled with optical fiber shown in FIG.  1 . FIG. 3 is a sectional view showing a cross-section of an optical waveguide. 
     In the axes of coordinates shown in FIG. 1A, a propagating direction of laser light is X-axis, a direction perpendicular to a plane of paper Y-axis, and an axis orthogonal to these directions Z-axis. Constituents of electric circuitry such as wiring and terminals for power supply are omitted in the figures. 
     On a substrate  19 , a semiconductor laser  11  and an optical waveguide  13  are disposed, one end of an optical fiber  16  being inserted into the inside of the optical waveguide  13 . An end-surface of an active layer  12  in the semiconductor laser  11  faces an end of a core  15  of the optical waveguide  13 , the other end of the core  15  of the optical waveguide  13  being opposite to an end of a core  18  of the optical fiber  16 . 
     Laser light is emitted from an end-surface of the active layer  12  of the semiconductor laser  11 . The laser light emitted from the active layer  12  is propagated to the core  18  of the optical fiber  16  after repeating total reflections at a boundary surface of the core  15  and a cladding layer  14 . Thus, the laser light of the semiconductor laser  11  is lead to the core  18  of the optical fiber  16  through the core  15  of the optical waveguide  13 . 
     The semiconductor laser  11  constitutes a semiconductor light emitting element in the present embodiment. In the present embodiment, the semiconductor laser  11  is a so-called edge emitting type semiconductor laser. 
     The optical waveguide  13 , as shown in a perspective view of FIG. 2 seen from the optical fiber  16  side, is constituted by surrounding a circumference of the core  15  by the cladding layer  14  of a refractive index lower than the core. The cladding layer  14  is constituted of upper and lower cladding layers  141  and  142 . On the optical fiber  16  side, v-grooves  21   a  and  21   b  are formed on the upper and lower cladding layers  141  and  142 . In the semiconductor laser  11  side, the cladding layer  14  forms arms  14   a  and  14   b.    
     As materials for the cladding layer  14  and the core  15 , glass and resin such as acrylic resin or polycarbonate can be used. On the other hand, in order to facilitate absorption of expansion and contraction due to temperature variations of a system constituting the device, silicone based resin may be used. 
     In general, when a width of the active layer  12  therefrom the laser light is emitted is narrow in a direction of Z-axis, the semiconductor laser  11  and the optical fiber  16  are optically coupled by means of optical system such as lenses or the like. The optical system such as the lens or the like converges the laser light emitted from the active layer  12  and leads to the core  18  of the optical fiber  16 . However, when the laser light of high output power is desired, the width of the active layer  12  becomes inevitably broader. Accordingly, it is difficult for the laser light emitted from the active layer  12  to be efficiently inputted into the core  18  of the optical fiber  16  of which cross section is ordinarily circular by means of the optical system such as the lens or the like. As the result of this, in the present embodiment, the semiconductor laser  11  and the optical fiber  16  are optically coupled by use of the optical waveguide  13 . 
     Here, the shape of the cross-section of the optical waveguide  13  is symmetrical with the core  15  as a center. That is, when the cross section is a rectangle, as shown in FIG. 3, thicknesses of Y-axis and Z-axis directions that sandwich the core are made equal, respectively. Naturally, when the cross section is a circle, the center of the core is the center of the circle. 
     Implementing thus, the expansion of the optical waveguide  13  due to heat generation of the semiconductor laser  11  becomes symmetrical with the core  15  as the center. Accordingly, positional shift between the active layer  12  and the core  15  can be suppressed smaller. 
     The configuration of FIG. 3 can be similarly applied to all the following embodiments. 
     The optical fiber  16  is surrounded a circumference of the core  18  by the cladding layer  17  of refractive index lower than that of the core  18  to constitute. 
     In the following, state of connections of the respective constituents will be explained in detail. 
     The semiconductor laser  11  is sandwiched by arms  14   a  and  14   b  extended on side surfaces thereof to fix to the optical waveguide  13 . In fixing, the semiconductor laser  11  is adhered to side surfaces of the arms  14   a  and  14   b  in the vicinity of the active layer  12 . Here, the semiconductor laser  11  is adhered to the arms  14   a  and  14   b  with the core  15  of the optical waveguide  13  pressed onto the active layer  12  of the semiconductor laser  11 . Accordingly, the optical waveguide  13  and the semiconductor laser  11  are solidly fixed with pressure exerted therebetween. 
     As a result of this, the active layer  12  of the semiconductor laser  11  faces the core  15  of the optical waveguide  13 , the semiconductor laser  11  and the optical waveguide  13  being optically coupled. 
     At an end-surface of the semiconductor laser  11  side of the optical waveguide  13 , the core  15  is projected from the cladding layer  14 , the core  15  and the active layer  12  being heightened in intimacy of contact. Thereby, efficient optical coupling between the core  15  and the active layer  12  can be implemented. 
     The optical fiber  16  is sandwiched by the V-grooves  21   a  and  21   b  of the optical waveguide  13  to fix. As a result of this, the core  15  of the optical waveguide  13  and the core  18  of the optical fiber  16  are disposed to face end-surfaces thereof to each other, the optical waveguide  13  and the optical fiber  16  being optically coupled. 
     In the neighborhood where the optical waveguide  13  and the optical fiber  16  are solidly fixed, a bottom surface of the optical waveguide  13  and the substrate  19  are adhered by means of an adherent  20 . As the result of this, as shown in FIG. 1B, between the optical waveguide  13  (in the neighborhood of the connection with the semiconductor laser  11  in particular) and the substrate  19 , a gap  22  corresponding to a thickness of a layer of the adherent  20  is disposed. 
     Due to the existence of the gap  22 , even if the optical waveguide  13  is dilated due to the heat generation of the semiconductor laser  11 , the optical waveguide  13  does not push the substrate  19 . As the result of this, the active layer  12  of the semiconductor laser  11  and the core  15  are not shifted relative to each other due to the dilation of the optical waveguide  13 . 
     As mentioned above, in the present embodiment, the optical waveguide is prevented from expanding due to the heat generation to push the substrate to result in the relative shifting between the active layer and the core. Accordingly, the laser light can be propagated with stability. 
     (Second Embodiment) 
     A second embodiment of a semiconductor light emitting element coupled with optical fiber involving the present invention will be explained. 
     FIG. 4 is a sectional side view showing the present second embodiment, corresponding to FIG.  1 B. FIG. 5 is a plan view showing part of a semiconductor light emitting element coupled with optical fiber involving the present embodiment. The same constituents with FIG. 1 are given the same reference numerals. 
     As shown in FIG. 4, the semiconductor laser  11  is attached to the substrate  19  through a base  31 . On the substrate  19 , the base  31  of a prescribed height of aluminum nitride that is excellent in thermal conduction is disposed. Further, on the base  31 , the semiconductor laser  11  is disposed so that the active layer  12  is located at an approximately equal height with the core  18  of the optical fiber  16 . 
     The semiconductor laser  11 , as approximately identical with FIG. 1B, is fixed to the optical waveguide  13  in the following way. That is, the semiconductor laser  11  or the base  31  are adhered to side surfaces of the arms  14   a  and  14   b  in the vicinity of the active layer  12 . Here, the semiconductor laser  11  or the base  31  are adhered to the arms  14   a  and  14   b  with the core  15  of the optical waveguide  13  pressed onto the active layer of the semiconductor laser  11 . Accordingly, the optical waveguide  13  and the semiconductor laser  11  are solidly fixed with pressure exerted therebetween. 
     As explained in FIG. 1, the optical waveguide  13  is adhered to the substrate  19  only in the neighborhood of the optical fiber  16 . As the result of this, between the optical waveguide  13  (vicinity of connection with the semiconductor laser  11  in particular) and the substrate  19 , the gap  22  corresponding to a thickness of a layer of the adherent  20  is disposed. 
     The present embodiment is effective when an active layer of a semiconductor laser is located close to a substrate thereto a semiconductor laser is solidly fixed, and the semiconductor laser  11 , the optical waveguide  13  and the optical fiber  16  are connected with difficulty on the same planar substrate  19 . 
     The plan view of FIG. 5, as a modification example of the second embodiment, shows the case where an upper surface of the base  31  is sufficiently larger than the semiconductor laser  11 . In this case, the arms  14   a  and  14   b  are removed of portions corresponding to the lower side cladding layer  142  shown in FIG. 2, being fixed on the base  31  at a portion corresponding to the upper side cladding layer  141 . 
     (Third Embodiment) 
     A third embodiment of a semiconductor light emitting element coupled with optical fiber involving the present invention will be explained. 
     FIGS. 6 and 7 are a sectional side view and a perspective view showing a third embodiment of the present invention. Here, FIG. 6 corresponds to FIG.  1 B. The same constituents with FIG. 1 are given the same reference numerals. 
     As shown in FIGS. 6 and 7, the semiconductor laser  11  is attached to the substrate  19 . On the substrate  19 , a step portion  51  corresponding to a height of the base  31  in FIG. 4 is formed integrally with the substrate  19 . The semiconductor laser  11  is disposed on the step portion  51 . As the result of this, the active layer  12  and the core  18  of the optical fiber  16  are disposed at an approximately same height. 
     In a step  151  due to the step portion  51  thereon the semiconductor laser  11  is mounted, as shown in FIG. 7, on both sides of the semiconductor laser  11 , concave portions  51   a  and  51   b  are formed. These concave portions  51   a  and  51   b  are formed in the sizes corresponding to the arms  14   a  and  14   b  of the cladding layer  14 . As the result of this, the arms  14   a  and  14   b  can enter into the concave portions  51   a  and  51   b.  Thereby, the step portion  51  thereon the semiconductor laser  11  is mounted, as identical with FIGS. 1 and 4 can be sandwiched. 
     In the present embodiment, without forming the concave portions  51   a  and  51   b,  a height of the semiconductor laser  11  can be adjusted. For instance, as in FIG. 5, with the arms  14   a  and  14   b  removed of the portions corresponding to the lower side cladding layer  142 , the portions corresponding to the upper side cladding layers  141  can be fixed on the step portion  51 . 
     (Fourth Embodiment) 
     A fourth embodiment of an semiconductor light emitting element coupled with optical fiber involving the present invention will be explained. 
     FIG. 8 is a plan view showing a fourth embodiment of the present invention, corresponding to FIG.  1 A. The same constituents with FIG. 1 are given the same reference numerals. 
     As shown in FIG. 8, the semiconductor laser  11  is attached to the substrate  19 . The arms  14   a  and  14   b  of the cladding layer  14  go around from side surfaces of the semiconductor laser  11  up to a rear surface  71  opposite to a surface where the semiconductor laser  11  contacts the core  15 . The arms  14   a  and  14   b  are adhered to the rear surface  71  to connect the semiconductor laser  11  and the optical waveguide  13 . 
     When the optical waveguide  13  is expanded due to heat generation of the semiconductor laser  11 , the arms  14   a  and  14   b  also expand. Accordingly, between the core  15  and the semiconductor laser  11 , force exerts to divert from each other. 
     However, the semiconductor laser  11  and the optical waveguide  13  being solidly fixed on the substrate  19  respectively (the optical waveguide  13  being solidly fixed on the substrate  19  in the neighborhood of the optical coupling between the optical waveguide  13  and the optical fiber  16 ), the semiconductor laser  11  and the core  15  do not separate from each other. 
     As the result of this, an optical coupling state of colliding surfaces of the active layer  12  and the core  15  is not affected adversely by the heat generation of the semiconductor laser  11 , resulting in a stable light output. 
     As shown in the above, FIG. 8 shows an embodiment where the arms  14   a  and  14   b  of the cladding layer  14  and the rear surface  71  of the semiconductor laser  11  are directly fixed. However, the arms  14   a  and  14   b  of the cladding layer  14  and the rear surface  71  of the semiconductor laser  11  can be indirectly fixed. For instance, as in the second embodiment, the semiconductor laser  11  is mounted on the base for height adjustment. Thereafter, a rear surface of the base on a side that does not contact the core  15  and side portions of the arms  14   a  and  14   b  of the cladding layer  14  can be adhered. 
     (Fifth Embodiment) 
     In the aforementioned embodiments 1 to 4, with the adherent  20 , the gap  22  is formed between the optical waveguide  13  and the substrate  19 . The gap  22  is formed in the neighborhood of the connection between the core  15  and the semiconductor laser  11 , a thickness thereof being corresponding to a thickness of the adherent  20 . 
     By contrast, a constitution that forms the gap  22  without necessarily depending on the thickness of the layer of the adherent  20  is shown as a fifth embodiment. 
     FIG. 9 is a sectional side view of an semiconductor light emitting element coupled with optical fiber involving a fifth embodiment of the present invention. 
     As shown in this figure, on the substrate  19  of a portion that demands a gap, a concave portion  81  is formed so that a step is formed from a side opposite to the optical fiber of the optical waveguide  13 . By means of the concave portion  81 , the gap  22  is formed in the vicinity of the connection between the core  15  and the semiconductor laser  11 . 
     In the present embodiment, compared with the case where the adherent  20  forms the gap  22 , a depth of the concave portion  81  can be arbitrarily set with ease. As the result of this, a necessary amount of the gap  22  can be obtained with ease. That is, the present embodiment, even if the desired gap is difficult to obtain by means of a layer of adherent, can be applied with ease. 
     FIG. 9 shows in a sense a modification example of a first embodiment. The formation of the concave portion  81  of the present embodiment is of course similarly applicable to the second to fourth embodiments. 
     (Other Embodiment) 
     The present invention is not restricted to the aforementioned embodiments. The embodiment of the present invention can be expanded and modified within the range of technical thought of the present invention, the expanded and modified embodiments also being included in the technical range of the present invention. 
     (1). For instance, as a semiconductor light emitting element, though a edge emitting type being used in the above, a surface light emitting type can be similarly effective. 
     (2). The adherent  20 , to form the gap  22  into an appropriate height, can be mixed with for instance fine spherical glass beads. Adjustment of a diameter of the glass beads being mixed with allows controlling a height of the gap  22 . 
     Other than the fifth embodiment, without depending on the layer of the adherent  20 , the gap  22  can be formed. For instance, a plate of an appropriate thickness can be interposed between the optical waveguide  13  and the substrate  19  as a spacer. Thereafter, by screwing up the optical waveguide  13  and the substrate  19 , the gap  22  corresponding to the thickness of the plate can be formed. 
     (3). The fundamental thought of the present invention is to reduce an influence of thermal expansion of the optical waveguide  13  in the vicinity of the optical coupling between the semiconductor light emitting element  11  and the optical waveguide  13 . For this, in the neighborhood of the optical coupling, the gap is formed for the optical waveguide  13  and the substrate  19  not to contact. 
     Means for forming the gap  22 , other than the means due to the adherent  20  or the concave portion  81 , the heights of the semiconductor light emitting element  11  and the optical waveguide  13  can be adjusted to implement. That is, the active layer  12  of the semiconductor light emitting element  11  can be made a little higher than that of the core of the optical waveguide  13  to form the gap  22  of an appropriate thickness. The height of the active layer  12  can be adjusted with ease by, other than the semiconductor light emitting element itself, adjustment of the height of the base  31 . 
     As obvious from the above, the thickness of the gap  22  can be determined by taking into consideration all of the adjustment of the heights of the semiconductor light emitting element  11  and the optical waveguide  13 , the thickness of the layer (or spacer) of the adherent  20  and the depth of the concave portion  81 .