Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-380284, filed Dec. 27, 2002, the entire contents of which are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to an improvement of a semiconductor laser device which, in particular, can be used as a light source of a projection image display apparatus.  
           [0004]    2. Description of the Related Art  
           [0005]    As is well known, in recent years, extensively performed are developments of semiconductor lasers to be used as a light source in projection image display apparatuses, such as liquid crystal projectors.  
           [0006]    In image display apparatuses of this kind, outgoing light from a semiconductor laser, which generates an intense light output as much as several to 10 W, is made incident on an optical fiber forming a fiber laser, and thereby visible light of a high optical density is generated and used for image display.  
           [0007]    Generally, semiconductor lasers having a high output are multimode lasers, and have a light-outgoing region having an elongate shape. For example, in the light-outgoing region of a semiconductor laser which outputs 1 W, the ratio of the length of a slow axis parallel to its active layer to the length of a fast axis vertical to the active layer is 50:1 to 500:1.  
           [0008]    In light-outgoing regions having such a high aspect ratio, light outgoing therefrom has an angle of divergence of only about ±4° in the slow axis direction with respect to an optical axis vertical to the surface of the light-outgoing region, while it has an angle of divergence of ±20° in the fast axis direction.  
           [0009]    Therefore, in the conventional art, to make outgoing light from a semiconductor laser incident efficiently on an optical element such as an optical fiber, a collimate lens such as a rod lens and a cylindrical lens is disposed immediately in front of the light-outgoing region, and the lens converts the outgoing light, which diverges in the fast axis direction, into parallel light.  
           [0010]    For example, Jpn. Pat. Appln. KOKAI Pub. No. 2000-98190 discloses a structure, wherein a peripheral surface in a central portion of a cylindrical rod lens is disposed adjacent to a light-outgoing surface of a semiconductor laser supported by a block member, and in the position both end portions of the peripheral surface of the rod lens are fixed on the block member by adhesive.  
           [0011]    However, the method of attaching a rod lens disclosed in the publication has the problem that, when adhesive is provided between the block member and the peripheral surface of the rod lens, the adhesive enters between the light-outgoing surface of the semiconductor laser and the peripheral surface of the rod lens and covers the light-outgoing surface of the semiconductor laser.  
         BRIEF SUMMARY OF THE INVENTION  
         [0012]    According to one aspect of the present invention, there is provided a semiconductor laser device comprising a base, a semiconductor laser configured to be supported by the base, and a collimate lens configured to have a portion opposed to a light-outgoing region of the semiconductor laser, and a portion to be adhered to the base, wherein a notch is formed at the base, and held between a portion to which the collimate lens is adhered and a portion which supports the semiconductor laser, of the base. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0013]    [0013]FIG. 1 is a perspective view illustrating a first embodiment of the present invention;  
         [0014]    [0014]FIG. 2 is a diagram illustrating a modification of the first embodiment;  
         [0015]    [0015]FIG. 3 is a diagram illustrating another modification of the first embodiment;  
         [0016]    [0016]FIG. 4 is a diagram illustrating a second embodiment of the present invention;  
         [0017]    [0017]FIG. 5 is a diagram illustrating a modification of the second embodiment; and  
         [0018]    [0018]FIG. 6 is a diagram illustrating another modification of the second embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    A first embodiment of the present invention will now be described in detail, with reference to drawings. FIG. 1 illustrates a schematic structure of a semi-conductor laser device explained in the first embodiment. Specifically, reference numeral  11  denotes a base, which is formed of copper and the like in a rectangular parallelpiped shape and also serves as a heat sink.  
         [0020]    A GaAs semiconductor laser  12  is mounted in a central portion of an upper surface  11   a  of the base  11 . The semiconductor laser  12  is supported by the base  11  such that its surface  12   b  having a light-outgoing region  12   a  is aligned with one side surface  11   b  of the base  11 .  
         [0021]    In the semiconductor laser  12 , a direction of the slow axis of the light-outgoing region  12   a  is defined as an X axis, a direction of the fast axis thereof is defined as a Y axis, and a direction in which laser light outgoes from the light-outgoing region  12   a,  that is, a direction vertical to the surface  12   b  having the light-outgoing region  12   a  of the semiconductor laser  12  is defined as a Z axis.  
         [0022]    Further, an insulating block  13 , which is formed of ceramics and the like and is nonconductive, is mounted on an end portion of the upper surface  11   a  of the base  11 . A terminal  14  located on an upper surface  13   a  of the insulating block  13  is connected to an external power supply.  
         [0023]    The semiconductor laser  12  is connected to the external power supply, by bonding an electrode formed on an upper surface of the semiconductor laser  12  to the terminal  14  by a wire  15  formed of gold. Further, an electrode formed on another surface of the semi-conductor laser  12  facing the base  11  is also connected to the external power supply through the base  11 .  
         [0024]    The semiconductor laser  12  is mounted on the upper surface  11   a  of the base  11  in a junction-down manner. Therefore, the light-outgoing region  12   a  of the semiconductor laser  12  is set in a position directly above the upper surface  11   a  of the base  11  with a solder layer intervened therebetween, and aligned with the side surface  11   b  of the base  11 .  
         [0025]    A cylindrical rod lens  16  is located on an upper end portion of the side surface  11   b  of the base  11  aligned with the surface  12   b  having the light-outgoing region  12   a  of the semiconductor laser  12 . The rod lens  16  is located such that its axis runs along the slow-axis direction of the light-outgoing region  12   a  of the semiconductor laser  12 .  
         [0026]    Further, the rod lens  16  is located such that its peripheral surface in the central portion of the rod lens is adjacent and opposed to the light-outgoing region  12   a  of the semiconductor laser  12 . The rod lens  16  is also located such that an optical axis of laser light outgoing from the light-outgoing region  12   a  of the semiconductor laser  12  runs through the center of the Y-axis direction.  
         [0027]    The rod lens  16  functions as a collimate lens for converting laser light, which outgoes from the light-outgoing region  12   a  of the semiconductor  12  and spreads in the fast-axis direction, into parallel light. After conversion, the laser light which has passed through the rod lens  16  is made incident on an optical element, such as an optical fiber, of the following stage.  
         [0028]    The rod lens  16  is fixed to the base  11 , by adhering both end portions of the peripheral surface to upper end portions of the side surface  11   b  aligned with the surface  12   b  having the light-outgoing region  12   a  of the semiconductor laser  12 , by ultraviolet-setting adhesive  17 .  
         [0029]    In this case, the rod lens  16  is positioned as described above with respect to the light-outgoing region  12   a  of the semiconductor laser  12 . Thereafter, an ultraviolet-setting adhesive  17  is poured between the both end portions of the peripheral surface and the side surface  11   b  of the base  11  and sets by ultraviolet irradiation. Thereby, the rod lens  16  is fixed to the base  11 .  
         [0030]    More practically speaking, the rod lens  16  is fixed by the adhesive  17  to a portion of the side surface  11   b  of the base  11  aligned with the surface  12   b  having the light-outgoing region  12   a  of the semiconductor laser  12 . The portion of the side surface  11   b  is very close to an edge  11   c  made by the upper surface  11   a,  on which the semiconductor laser  12  is mounted, and the side surface  11   b.    
         [0031]    A space between the light-outgoing region  12   a  of the semiconductor laser  12  and the central portion of the peripheral surface of the rod lens  16  is set very narrow. Therefore, there is a risk that the adhesive  17  poured between the both end portions of the peripheral surface of the rod lens  16  and the side surface  11   b  of the base  11  enters between the side surface  11   b  and the rod lens  16  by a capillary phenomenon, and intrudes into the light-outgoing region  12   a  of the semiconductor laser  12 .  
         [0032]    Therefore, in the first embodiment, in the base  11 , notches  18  are formed on both sides of the portion on which the semiconductor laser  12  is mounted, and inside the portions to which the adhesive  17  is applied. Each of the notches  18  are formed to range from the upper surface  11   a  and the side surface  11   b,  including the edge  11   c  of the base  11 .  
         [0033]    Thereby, even if the adhesive  17  poured between the end portions of the peripheral surface of the rod lens  16  and the side surface  11   b  of the base  11  runs between the side surface  11   b  and the rod lens  16 , the adhesive  17  is collected in the notches  18  and is fully prevented from reaching the semiconductor laser  12 . This eliminates the need to strictly specify the applying amount of the adhesive  17 , thus simplifies assembly of the device.  
         [0034]    [0034]FIG. 2 illustrates a modification of the first embodiment. Specifically, between the side surface  11   b  of the base  11  aligned with the surface  12   b  having the light-outgoing region  12   a  of the semiconductor laser  12  and the both end portions of the peripheral surface of the rod lens  16 , spacers  19  are provided to the base  11  for controlling the space between them.  
         [0035]    Further, the rod lens  16  is abut against the side surface  11   b  of the base  11  with the spacers  19  intervened therebetween, and the adhesive  17  is applied in the above state to fix the spacers  19  and the rod lens  16  to the base  11 . Thereby, it is possible to easily set the space between the light-outgoing region  12   a  of the semiconductor laser  12  and the rod lens  16 , and simplify assembly of the device.  
         [0036]    Although the spacers  19  are provided in positions outside the notches  18  in FIG. 2, the spacers  19  may be provided in positions inside the notches  18 , as long as the adhesive  17  is applied to positions outside the notches  18 .  
         [0037]    [0037]FIG. 3 illustrates another modification of the first embodiment. Specifically, in the base  11 , projections  20  serving as spacers for controlling the space between the side surface  11   b  and the both end portions of the peripheral surfaces of the rod lens  16  are provided on the side surface  11   b  aligned with the surface  12   b  having the light-outgoing region  12   a  of the semiconductor laser  12 .  
         [0038]    Further, the rod lens  16  is abut against the projections  20  formed on the side surfaces  11   b  of the base  11 , and the adhesive  17  is applied in the above state to fix the rod lens  16  to the base  11 . Thereby, it is possible to easily set the space between the light-outgoing region  12   a  of the semiconductor laser  12  and the rod lens  16 , and simplify assembly of the device.  
         [0039]    Although the projections  20  are provided in positions outside the notches  18  in FIG. 3, the projections  20  may be provided in positions inside the notches  18 , as long as the adhesive  17  is applied to positions outside the notches  18 .  
         [0040]    Next, FIG. 4 illustrates a second embodiment of the present invention. In FIG. 4, like reference numerals denote like constituent elements of FIG. 1. In FIG. 4, in a rod lens  16 , notches  21  are formed on both sides of a portion of a peripheral surface which is opposed to a light-outgoing region  12   a  of a semiconductor laser  12 , and at positions inside portions to which adhesive  17  is applied.  
         [0041]    Thereby, even if the adhesive  17  poured between the both end portions of the peripheral surface of the rod lens  16  and a side surface  11   b  of a base  11  runs between the side surface  11   b  and the rod lens  16 , the adhesive is collected in the notches  21  and is fully prevented from reaching the semiconductor laser  12 . Therefore, it eliminates the need to strictly specify the applying amount of the adhesive  17 , thus simplifies assembly of the device.  
         [0042]    [0042]FIG. 5 illustrates a modification of the second embodiment. Specifically, in the base  11 , between the side surface  11   b  of the base  11  aligned with the surface  12   b  having the light-outgoing region  12   a  of the semiconductor laser  12  and both end portions of the peripheral surface of the rod lens  16 , spacers  22  are provided for controlling the space between them.  
         [0043]    Further, the rod lens  16  is abut against the side surface  11   b  of the base  11  with the spacers  22  intervened therebetween, and the adhesive  17  is applied in the above state to fix the spacers  22  and the rod lens  16  to the base  11 . Thereby, it is possible to easily set the space between the light-outgoing region  12   a  of the semiconductor laser  12  and the rod lens  16 , and simplify assembly of the device.  
         [0044]    Although the spacers  22  are provided in positions outside the notches  18  in FIG. 5, the spacers  22  may be provided in positions inside the notches  21 , as long as the adhesive  17  is applied to positions outside the notches  21 .  
         [0045]    [0045]FIG. 6 illustrates another modification of the second embodiment. Specifically, in the base  11 , projections  23  serving as spacers for controlling the space between the side surface  11   b  and the both end portions of the peripheral surfaces of the rod lens  16  are provided on the side surface  11   b  aligned with the surface  12   b  having the light-outgoing region  12   a  of the semiconductor laser  12 .  
         [0046]    Further, the rod lens  16  is abut against the projections  23  formed on the side surfaces  11   b  of the base  11 , and the adhesive  17  is applied in the above state to fix the rod lens  16  to the base  11 . Thereby, it is possible to easily set the space between the light-outgoing region  12   a  of the semiconductor laser  12  and the rod lens  16 , and simplify assembly of the device.  
         [0047]    Although the projections  23  are provided in positions outside the notches  21  in FIG. 6, the projections  23  may be provided in positions inside the notches  21 , as long as the adhesive  17  is applied to positions outside the notches  21 .  
         [0048]    Although the case where the rod lens  16  is fixed to the base  11  is explained in the above first and second embodiments, the present invention is not limited to using the rod lens  16 , but may use a cylindrical lens and the like. In short, the present invention is widely applicable to attachment of a collimate lens for converting laser light, which outgoes from the light-outgoing region  12   a  of the semiconductor laser  12 , spreading in the fast-axis direction, into parallel light.  
         [0049]    Further, in the first and second embodiments, the notches  18  of the base  11  and the notches  21  of the rod lens  16 , respectively, are formed on both sides of the semiconductor laser  12 . However, they may be formed on only one side of the semiconductor laser  12 , according to necessity.  
         [0050]    The present invention is not limited to the above embodiments, but its constituent elements may be variously modified in carrying out the present invention, without departing from the gist of the invention. Further, various inventions can be made by properly combining the plural constituent elements disclosed in the above embodiments. For example, some of the constituent elements disclosed in the embodiments may be deleted, and some of the constituent elements disclosed in one embodiment may be added to another embodiment.

Technology Category: 5