Abstract:
The present invention proposes a semiconductor light-emitting device having an axis of symmetry, the device including two or more laser diodes, each of the laser diodes has an axis of symmetry, wherein the laser diodes are arranged in series on the axis of symmetry of the light-emitting device in such a way that their axes of symmetry coincide, wherein faces of the laser diodes are connected so that they are in electric and mechanic contact and form a bar of the laser diodes, a directional pattern of radiation thereof has an axis of symmetry coinciding with the axis of symmetry of the light-emitting device. The proposed light-emitting device can be used in laser lamps of white light for exciting phosphors since it provides a high degree of flare of cylindrical surfaces.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Phase of International Application No. PCT/RU2015/000137, filed 5 Mar. 2015, which claims benefit of Russian Patent Application No. 2014108564, filed 5 Mar. 2014, the contents of which are incorporated herein by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to light-emitting devices, in particular, to highly effective solid state light-emitting devices made on a base of a bar of laser diodes. 
       BACKGROUND ART 
       [0003]    At the present time, bars of laser diodes are widely used for pumping powerful solid body lasers used for cutting, welding, grinding and thermal treatment of surfaces of various materials in many fields of industry and medicine. 
         [0004]    Usually a bar of laser diodes consists of a set of single strip-geometry laser diodes, arranged parallel to each other on a common substrate, which is used as a heat sink, RU2150164, RU2455739. These bars of strip-geometry laser diodes emit light in a determined direction as a set of parallel beams. 
         [0005]    Single laser diodes with cylindrically symmetrical resonators with light extraction in any determined direction, either parallel to an axis of symmetry of the resonator, or perpendicular to the axis of symmetry were also proposed, U.S. Pat. No. 5,343,490, U.S. Pat. No. 6,134,257, U.S. Pat. No. 6,333,944, U.S. Pat. No. 6,519,271, U.S. Pat. No. 8,326,098, RU2423764, RU2431225, and also arrays of geometrically diverged in the directions perpendicular to their axes of symmetry of axially symmetric laser diodes, RU2465699, US 2011/0163292 A1. 
         [0006]    The possibility of using laser diodes in combination with phosphor in sources of white light for illumination purposes represents a considerable interest, AIP ADVANCES 3, 072107 (2013). 
         [0007]    To provide a small-sized laser light source capable of emitting light in various directions and having a directional pattern of a far radiation field close to axially symmetric, without forming optics, it was proposed to use a set of units of the strip-geometry laser diodes turned relative to each other in a plane perpendicular to an axis of radiation, RU 2187183, selected as a prototype. 
         [0008]    The drawback of laser diodes and bars of laser diodes existing in the present-day is an inability to provide a homogeneous flare of phosphor in axially symmetric laser lamps when using these diodes as emitting elements in the laser source of light. 
       SUMMARY 
       [0009]    To solve this problem the present invention proposes a semiconductor light-emitting device having an axis of symmetry, and including two or more laser diodes. The claimed device is characterized in that each of the laser diodes has an axis of symmetry, wherein the laser diodes are arranged in series on the axis of symmetry of the light-emitting device in such a way that their axes of symmetry coincide, wherein the faces of the laser diodes are connected so that they are in electric and mechanic contact and form a bar of laser diodes, a directional pattern of radiation thereof has an axis of symmetry coinciding with the axis of symmetry of the light-emitting device. 
         [0010]    In preferred embodiments, each of the laser diodes includes a disc optical resonator, or a hollow optical resonator, or a ring optical resonator, or a polygonal optical resonator, or a hollow polygonal optical resonator. 
         [0011]    In a preferred embodiment each of the laser diodes is made of III-nitrides. 
         [0012]    The invention also proposes a laser lamp containing a phosphor characterized in that the proposed semiconductor light-emitting device is used as a source of visible or ultra-violet light for optical excitation of the phosphor. 
         [0013]    A capability of the proposed semiconductor light-emitting device to emit light in all directions perpendicular to the axis of symmetry is used in the proposed laser lamp to provide a high degree of homogeneity of flare of cylindrically symmetric surfaces on which the phosphor is deposited. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  shows a single laser diode with a disc optical resonator which is a component of a cylindrical bar of laser diodes shown in  FIG. 2 . 
           [0015]      FIG. 2  shows a cylindrical bar of laser diodes having an axis of symmetry and composed of the single laser diodes shown in  FIG. 1 . 
           [0016]      FIG. 3  shows a diagram of a cylindrically symmetric lamp emitting white light and using phosphor for converting ultra-violet or blue radiation into white light, as well as using the bar of laser diodes shown in  FIG. 2  as a generator of ultra-violet or blue radiation. 
           [0017]      FIG. 4  shows a single laser diode with a hollow disc optical resonator which is a component of the cylindrical bar of laser diodes shown in  FIG. 5 . 
           [0018]      FIG. 5  shows a cylindrical bar of laser diodes with a through cavity having an axis of symmetry and composed of the single laser diodes shown in  FIG. 4 . 
           [0019]      FIG. 6  shows a single laser diode with a ring optical resonator which is a component of the cylindrical bar of laser diodes shown in  FIG. 7 . 
           [0020]      FIG. 7  shows a cylindrical bar of laser diodes with a through cavity having an axis of symmetry and composed of the single laser diodes shown in  FIG. 6 . 
           [0021]      FIG. 8  shows a single laser diode with a hexagonal resonator which is a component of the hexagonal bar of laser diodes shown in  FIG. 9 . 
           [0022]      FIG. 9  shows a hexagonal bar of laser diodes with a through hexagonal cavity having an axis of sixth order symmetry and composed of the single laser diodes shown in  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    This invention will become clear in terms of several embodiments given below. It should be noted, that the subsequent description of these embodiments is an illustrative one only and is not an exhaustive one. 
       EXAMPLE 1 
     A Cylindrical Bar of Blue Laser Diodes Used as a Light Source in a Cylindrical Laser Lamp 
       [0024]    In this example, an axially symmetric bar of laser diodes consists of single laser diodes with a structure GaN/Al 0.2 Ga 0.8 N/GaN/In 0.25 Ga 0.75 N/GaN/In 0.25 Ga 0.75 N/GaN/Al 0.2 Ga 0.8 N/GaN with disc optical resonators. 
         [0025]    A single laser diode with a disc optical resonator is shown in  FIG. 1 . It consists of a metal n-contact  1 , a contact layer  2  of n-type gallium nitride doped with silicon of concentration 5·10 18  cm −3  and 2μ thick, a cladding  3  of solid solution Al 0.2 Ga 0.8 N of n-type 0.5μ thick doped with silicon of concentration 10 19  cm −3 , a waveguiding layer  4  of gallium nitride which includes two In 0.2 Ga 0.8 N quantum wells 2.5 nm wide, a cladding layer  5  of solid solution Al 0.2 Ga 0.8 N of p-type 0.5μ thick doped with magnum of concentration 5·10 20  cm −3 , a contact layer  6  of p-type gallium nitride 0.1μ thick, doped with magnum of concentration 10 20  cm −3  and a metal p-contact  7 . 
         [0026]    A cylindrical bar of vertically integrated laser diodes with disc optical resonators is shown in  FIG. 2 . Electrical voltage supplying the cylindrical bar of vertically integrated single diodes is applied through the n-contact  1  of an upper laser diode and through the p-contact  7  of a lower laser diode. A supply voltage of the bar of laser diodes is equal to V=n·V LD , where n is a number of the laser diodes in the bar, and V LD  is a supply voltage of single laser diode. Choice of the number n of the laser diodes in the bar allows changing the supply voltage V of the bar and provides a suitable matching of the supply voltage V with supply sources and power networks. The upper p-contacts and the lower n-contacts of the neighboring laser diodes are pressed mechanically and form an electric connection  9  between n-contact  1  and p-contact  7 . Thus, current supplying the bar of laser diodes flows through the n-contact  1  and p-contact  7  of the laser diodes, then through the contact layers  2  and  6 , cladding layers  3  and  5 , as well as through the waveguiding layers  4  with active quantum wells of all the laser diodes vertically integrated into the bar. In this case, since the cylindrical bar of laser diodes has an axis of symmetry  8 , light  10  therefrom is emitted homogeneously in all directions perpendicular to the axis of symmetry  8 . 
         [0027]    Use of the cylindrical bar of laser diodes as a light source in a cylindrical laser lamp is shown in  FIG. 3 . 
         [0028]    The cylindrical laser lamp consists of a transparent plastic cylinder  13  with phosphor  14  applied on side walls of cylinder, inside of which a cylindrical bar  12  of laser diodes is placed. 
         [0029]    When applying a supply voltage V to external wires  15  and  16  passing inside the cylinder  13  through openings  17  and connected to upper and lower contacts of the cylindrical bar  12  of laser diodes, current flowing through the laser bar generates blue light  10  which is emitted homogeneously in all directions perpendicular to the axis of symmetry. In this case a homogeneous flare of phosphor  14 , which partially converts blue light into yellow one, is provided, and as a result of mixing of blue and yellow lights, white light  18  goes outwards. Since the whole laser lamp has cylindrical symmetry white light  18  is emitted homogeneously in all directions perpendicular to its axis of symmetry. 
       EXAMPLE 2 
     A Hollow Cylindrical Bar of Ultra-Violet Laser Diodes Used as a Light Source in a Cylindrical Laser Lamp 
       [0030]    In this example the axially symmetric bar of the laser diodes consists of single laser diodes with a structure GaN/Al 0.4 Ga 0.6 N/Al 0.2 Ga 0.8 N/GaN/Al 0.2 Ga 0.8 N/Al 0.4 Ga 0.6 N/GaN with hollow disc optical resonators. 
         [0031]    A single laser diode with a hollow disc optical resonator is shown in  FIG. 4 . It consists of a metal n-contact  1 , a contact layer  2  of n-type gallium nitride doped with silicon of concentration 5·10 18  cm −3  and 2μ thick, a cladding layer  3  of solid solution Al 0.4 Ga 0.6 N of n-type 0.5μ thick doped with silicon of concentration 10 19  cm −3 , waveguiding layer  4  Al 0.2 Ga 0.8 N which includes a GaN quantum well 3 nm wide, a cladding layer  5  of solid solution Al 0.4 Ga 0.6 N of p-type 0.5μ thick doped with magnum of concentration 10 20  cm −3 , a contact layer  6  of p-type gallium nitride 0.1μ thick, doped with magnum of concentration 10 20  cm −3  and a metal p-contact  7 . The laser diode includes a cylindrical cavity  11  passing through all layers of its structure disposed along the axis of symmetry. 
         [0032]    A cylindrical bar of vertically integrated laser diodes with hollow disc optical resonators is shown in  FIG. 5 . Electrical voltage supplying the cylindrical bar of vertically integrated single diodes is applied through an n-contact  1  of an upper laser diode and through a p-contact  7  of a lower laser diode. A supply voltage of the bar of laser diodes is equal to V=n·V LD , where n is a number of the laser diodes in the bar, and V LD  is the supply voltage of single laser diode. The choice of the number n of laser diodes in the bar allows changing the supply voltage V of the bar and provides a suitable matching of the supply voltage V with supply sources and power networks. The upper p-contacts and the lower n-contacts of neighboring laser diodes are pressed mechanically and form an electric connection  9  between n-contact  1  and p-contact  7 . Thus, current supplying the bar of laser diodes flows through the n-contact  1  and p-contact  7  of the laser diodes, then through the contact layers  2  and  6 , the cladding layers  3  and  5 , as well as through waveguiding layers  4  with an active quantum well of all laser diodes vertically integrated into the bar. In this case, since the cylindrical bar of laser diodes has the axis of symmetry  8 , light  10  therefrom is emitted homogeneously in all directions perpendicular to the axis of symmetry  8 . The hollow cylindrical bar of laser diodes includes a cylindrical cavity  11  disposed along the axis of symmetry and passing through all laser diodes. Existence of the cavity  11  allows pumping a cooling liquid through the bar of laser diodes and effectively taking away heat produced in the process of light generation. 
         [0033]    Use of the hollow cylindrical bar of laser diodes as a light source in a cylindrical laser lamp is shown in  FIG. 3 . 
         [0034]    The cylindrical laser lamp consists of a transparent plastic cylinder  13  with phosphor  14  applied on side walls of cylinder, inside of which a hollow cylindrical bar  12  of laser diodes is placed. 
         [0035]    When applying a supply voltage V to external wires  15  and  16  passing inside the cylinder  13  through openings  17  and connected to upper and lower contacts of the hollow cylindrical bar  12  of laser diodes, current flowing through the laser bar generates ultra-violet light  10  which is emitted homogeneously in all directions perpendicular to the axis of symmetry. In this case a homogeneous flare of phosphor  14 , which fully converts ultra-violet light into white one, is provided, and as a result white light  18  goes outwards. A cooling liquid, which passes through the bar of laser diodes and effectively takes away heat produced in process of light generation, is also fed to the cylindrical bar  12  through the openings  17 . 
         [0036]    Since the whole laser lamp has cylindrical symmetry, white light  18  is emitted homogeneously in all directions perpendicular to its axis of symmetry. 
       EXAMPLE 3 
     A Ring Cylindrical Bar of Blue Laser Diodes Used as a Light Source in a Cylindrical Laser Lamp 
       [0037]    In this example an axially symmetric bar of laser diodes consists of single laser diodes with a structure GaN/Al 0.2 Ga 0.8 N/GaN/In 0.2 Ga 0.8 N/GaN/Al 0.2 Ga 0.8 N/GaN with ring optical resonators. 
         [0038]    A single laser diode with a ring optical resonator is shown in  FIG. 6 . It consists of a metal n-contact  1 , a contact layer  2  of n-type gallium nitride doped with silicon of concentration 5·10 18  cm −3  and 2μ thick, a cladding layer  3  of solid solution Al 0.2 Ga 0.8 N of n-type 0.5μ thick doped with silicon of concentration 10 19  cm −3 , a waveguiding layer  4  of gallium nitride which includes In 0.2 Ga 0.8 N quantum well 3 nm wide, a cladding layer  5  of solid solution Al 0.2 Ga 0.8 N of p-type 0.5μ thick doped with magnum of concentration 10 20  cm −3 , a contact layer  6  of p-type gallium nitride 0.1μ thick, doped with magnum of concentration 10 20  cm −3  and a metal p-contact  7 . The laser diode with the ring optical resonator includes a cylindrical cavity  11  passing through all layers of its structure disposed along the axis of symmetry. 
         [0039]    A ring cylindrical bar of vertically integrated laser diodes with ring optical resonators is shown in  FIG. 7 . Electrical voltage supplying the ring cylindrical bar of vertically integrated single diodes is applied through an n-contact  1  of an upper laser diode and through a p-contact  7  of a lower laser diode. A supply voltage of the bar of laser diodes is equal to V=n·V LD , where n is a number of laser diodes in the bar, and V LD  is the supply voltage of the single laser diode. A choice of the number n of the laser diodes in the bar allows changing the supply voltage V of the bar and provides a suitable matching of the supply voltage V with supply sources and power networks. The upper p-contacts and the lower n-contacts of neighboring laser diodes are pressed mechanically and form an electric connection  9  between n-contact  1  and p-contact  7 . Thus, current supplying the bar of laser diodes flows through the n-contact  1  and p-contact  7  of the laser diodes, then through the contact layers  2  and  6 , the cladding layers  3  and  5 , as well through the waveguiding layers  4  with an active quantum well of all the laser diodes vertically integrated into the bar. In this case, since the cylindrical bar of laser diodes has the axis of symmetry  8 , light  10  therefrom is emitted homogeneously in all directions perpendicular to the axis of symmetry  8 . The ring cylindrical bar of laser diodes includes a cylindrical cavity  11  disposed along the axis of symmetry and passing through all laser diodes. Existence of the cavity  11  allows pumping a cooling liquid through the bar of laser diodes and effectively taking away of heat produced in the process of light generation. 
         [0040]    Use of a ring cylindrical bar of laser diodes as a light source in a cylindrical laser lamp is shown in  FIG. 3 . 
         [0041]    The cylindrical laser lamp consists of a transparent plastic cylinder  13  with phosphor  14  applied on side walls of cylinder, inside of which a ring cylindrical bar  12  of laser diodes is placed. 
         [0042]    When applying a supply voltage V to external wires  15  and  16  passing inside the cylinder  13  through openings  17  and connected to upper and lower contacts of the cylindrical bar  12  of laser diodes, current flowing through the laser bar generates blue light  10  which is emitted homogeneously in all directions perpendicular to the axis of symmetry. In this case a homogeneous flare of phosphor  14 , which partially converts blue light into yellow one, is provided and as a result of mixing blue and yellow lights, white light  18  goes outwards. A cooling liquid, which passes through the bar of laser diodes and effectively takes away heat generated in the process of light generation, is also fed to the ring cylindrical bar  12  through the openings  17 . 
         [0043]    Since the whole laser lamp has cylindrical symmetry, white light  18  is emitted homogeneously in all directions perpendicular to its axis of symmetry. 
       EXAMPLE 4 
     A Hollow Hexagonal Bar of Ultra-Violet Laser Diodes Used as a Light Source in a Cylindrical Laser Lamp 
       [0044]    In this example a bar of laser diodes consists of single laser diodes with a structure GaN/Al 0.4 Ga 0.6 N/Al 0.2 Ga 0.8 N/GaN/Al 0.2 Ga 0.8 N/Al 0.4 Ga 0.6 N/GaN with hollow hexagonal optical resonators. 
         [0045]    A single laser diode with a hollow hexagonal optical resonator is shown in  FIG. 8 . It consists of a metal n-contact  1 , a contact layer  2  of n-type gallium nitride doped with silicon of concentration 5·10 18  cm −3  and 2μ thick, a cladding layer  3  of solid solution Al 0.4 Ga 0.6 N of n-type 0.5μ thick doped with silicon of concentration 10 19  cm −3 , a waveguiding layer  4  Al 0.2 Ga 0.8 N which includes a GaN quantum well 3 nm wide, a cladding layer  5  of solid solution Al 0.4 Ga 0.6 N of p-type 0.5μ thick doped with magnum of concentration 10 20  cm −3 , a contact layer  6  of p-type gallium nitride 0.1μ thick, doped with magnum of concentration 10 20  cm −3  and a metal p-contact  7 . The laser diode includes a hexagonal cavity  11  passing through all layers of its structure disposed along the axis of symmetry. 
         [0046]    A hollow hexagonal bar of the vertically integrated laser diodes with hollow hexagonal optical resonators is shown in  FIG. 9 . Electrical voltage supplying the cylindrical bar of vertically integrated single diodes is applied through an n-contact  1  of an upper laser diode and through a p-contact  7  of a lower laser diode. A supply voltage of the bar of laser diodes is equal to V=n·V LD , where n is a number of laser diodes in the bar, and V LD  is the supply voltage of a single laser diode. Choice of the number n of laser diodes in the bar allows changing the supply voltage V of the bar and provides a suitable matching of the supply voltage V with supply sources and power networks. The upper p-contacts and the lower n-contacts of neighboring laser diodes are pressed mechanically and form the electric connection  9  between n-contact  1  and p-contact  7 . Thus, current supplying the bar of laser diodes flows through the n-contact  1  and p-contact  7  of the laser diodes, then through the contact layers  2  and  6 , the cladding layers  3  and  5 , as well as through the waveguiding layers  4  with an active quantum well of all laser diodes vertically integrated into the bar. In this case, since the hollow hexagonal bar of laser diodes has the axis of symmetry  8 , light  10  therefrom will is emitted almost homogeneously in all directions perpendicular to the axis of symmetry  8 . The hollow hexagonal bar of laser diodes includes a hexagonal cavity  11  disposed along the axis of symmetry and passing through all laser diodes. Existence of the cavity  11  allows pumping a cooling liquid through the bar of laser diodes and effectively taking away heat produced in the process of light generation. 
         [0047]    Use of a hollow hexagonal bar of laser diodes as a light source in a cylindrical laser lamp is shown in  FIG. 3 . 
         [0048]    The cylindrical laser lamp consists of a transparent plastic cylinder  13  with phosphor  14  deposited on side walls of the cylinder, inside of which a hollow hexagonal bar  12  of laser diodes is placed. 
         [0049]    When applying supply voltage V to external wires  15  and  16  passing inside the cylinder  13  through openings  17  and connected to upper and lower contacts of the hollow cylindrical bar  12  of laser diodes, current flowing through the laser bar generates ultra-violet light  10  which is emitted almost homogeneously in all directions perpendicular to the axis of symmetry. In this case almost homogeneous flare of phosphor  14  which fully converts ultra-violet light into white one is provided and, as a result, white light  18  goes outwards. A cooling liquid, which passes through the bar of laser diodes and effectively takes away heat produced in the process of light generation, is also fed to the hollow hexagonal bar  12  through the openings  17 . 
         [0050]    Since the whole laser lamp possesses the axis of the six order symmetry, white light  18  is emitted almost homogeneously in all directions perpendicular to its axis of symmetry. 
         [0051]    Despite the fact that this invention has been described and represented by the examples of the invention embodiments, it should be noted that this invention is not limited by the given examples in any case.