Abstract:
A method and apparatus for combining light output from multiple laser diode bars is disclosed. The apparatus includes two laser diode bars and a mirror arrangement placed between the laser diode bars. The mirror arrangement reflects the light output from the laser diode bars into a preferred plane and a preferred direction. The mirror arrangement is preferably comprised of metal mirrors. Alternative mirror assemblies disclosed are based on prisms. An alternative mirror disclosed includes a cylindrically concave surface for collimating or focusing an individual laser beam.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of lasers. More particularly, the present invention relates to laser diode bars. 
     BACKGROUND OF THE INVENTION 
     A laser diode bar of the prior art is illustrated in FIG.  1 . The laser diode bar  2  includes a plurality of light emitting surfaces  4 . The plurality of light emitting surfaces  4  each emit a laser beam  6 . The plurality of light emitting surfaces form a linear array. The laser beams  6  combine to form a light output  8 . Each laser beam is located on a center  10 . The centers  10  are located on a pitch  12  and lie in a plane. 
     A laser diode bar has an upper limit on power output. Hawkes et al. in “Lasers Theory and Practice,” pages 407 and 408, teach that linear arrays of laser diodes can be stacked in order to produce higher output. In some applications it would be advantageous to increase the power output while maintaining the centers of the laser beams in a common plane. 
     What is needed is a method of combining light output from multiple laser diode bars while placing the centers of the laser beams in a common plane. 
     SUMMARY OF THE INVENTION 
     This invention is a method and apparatus for combining light output from multiple laser diode bars. The apparatus includes two laser diode bars and a mirror arrangement placed between the laser diode bars. The mirror arrangement reflects the light output from the laser diode bars into a preferred plane and a preferred direction. The mirror arrangement is preferably comprised of metal mirrors. Alternative mirror arrangements are based on prisms. An alternative mirror includes a cylindrically concave surface for collimating or focusing an individual laser beam. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a laser diode bar of the prior art. 
     FIG. 2 illustrates the preferred embodiment for combining light output from multiple laser diode bars of the present invention. 
     FIG. 3 illustrates the preferred mirror arrangement of the present invention. 
     FIG. 4 illustrates a first alternative embodiment for combining light output from multiple laser diode bars of the present invention. 
     FIG. 5 illustrates a second alternative embodiment for combining light output from multiple laser diode bars of the present invention. 
     FIG. 6 illustrates a third alternative embodiment for combining light output from multiple laser diode bars of the present invention. 
     FIG. 7A illustrates an assembly of prism mirrors of the present invention. 
     FIG. 7B illustrates a cross section of the assembly of prism mirrors of the present invention. 
     FIG. 8A illustrates an alternative assembly of prism mirrors of the present invention. 
     FIG. 8B illustrates a cross section of the alternative assembly of prism mirrors of the present invention. 
     FIG. 9 illustrates a cylindrically concave mirror for focusing a laser beam of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment for combining light output from multiple laser diode bars of the present invention is illustrated in FIG.  2 . The preferred embodiment  20  includes a first diode laser bar  22 , a second diode laser bar  24 , and a preferred mirror arrangement  26 . The first laser diode bar  20  is placed to a first side of the preferred mirror arrangement  26 . The second laser diode bar  24  is placed to a second side of the preferred mirror arrangement  26 . The first laser diode bar  22  emits a first laser beam  28 , a second laser beam  30 , and a third laser beam  32 . The first, second. and third laser beams  28 ,  30 , and  32  as well as other laser beams of the present invention are illustrated in the figures by centers of the laser beams in order to clearly illustrate the present invention. The first , second, and third laser beams  28 ,  30 , and  32  comprise a first light output  34 . It will be apparent to one of ordinary skill in the art that the first laser diode bar  22  can be configured to emit more or fewer laser beams. 
     The second laser diode bar  24  emits a fourth laser beam  36 , a fifth laser beam  38 , and a sixth laser beam  40 . The fourth, fifth, and sixth laser beams  36 ,  38 , and  40  comprise a second light output  42 . The second laser diode bar  24  can be configured to emit more or fewer laser beams. 
     Upon encountering the preferred mirror arrangement  26 , the first light output  34  and the second light output  42  are reflected into a common direction. The first light output  34  and the second light output  42  form a preferred combined light output  44 . The first, second, and third laser beams  28 ,  30 , and  32  are interdigitated with the fourth, fifth, and sixth laser beams  36 ,  38 , and  40  to form the preferred combined light output  44 . 
     The first, second, and third laser beams  28 ,  30 , and  32  are on a first pitch with first centers. The first centers define a first plane between the first laser diode bar  22  and the preferred mirror arrangement  26 . The fourth, fifth, and sixth laser beams  36 ,  38 , and  40  are on a second pitch with second centers. The second centers define a second plane between the second laser diode bar  24  and the preferred mirror arrangement  26 . The first pitch and the second pitch are preferably equal. The first, second, and third laser beams  28 ,  30 , and  32  encounter the first mirror arrangement  26  about an intersecting line  46 . The fourth, fifth, and sixth laser beams  36 ,  38 , and  40  also encounter the first mirror arrangement  26  about the intersecting line  46 . At the intersecting line  46 , the second centers are preferably offset from the first centers by half the first pitch. Upon the first and second light outputs  34  and  42  reflecting from the preferred mirror arrangement  26 , the first and second centers define a common plane. 
     The preferred mirror arrangement  26  of the present invention is illustrated in FIG.  3 . The preferred mirror arrangement  26  includes first mirrors  48  and second mirrors  50 . The first and second mirrors  48  an  50  are preferably metallic mirrors. Alternatively, the first and second mirrors  48  and  50  are formed of glass and coated with a reflective material. 
     A first alternative embodiment for combining light output from multiple laser diode bars of the present invention is illustrated in FIG.  4 . The first alternative embodiment  52  includes the first and second diode laser bars  22  and  24 , and a first alternative mirror arrangement  54 . The first laser diode bar  22  is placed to a side of the first alternative mirror arrangement  54 . The second laser diode bar  24  is placed below the first alternative mirror arrangement  54 . The first laser diode bar  42  emits the first, second, and third laser beams  28 ,  30 , and  32 , which comprise the first light output  34 . The second laser diode bar  24  emits the fourth, fifth, and sixth laser beams  36 ,  38 , and  40 , which comprise the second light output  42 . The second light output  42  has a preferred direction. The first alternative mirror arrangement  54  allows the second light output  42  to pass the first alternative mirror arrangement  54  unimpeded. The first alternative mirror arrangement  54  reflects the first light output  34  into the preferred direction. The first light output  34  and the second light output  42  combine to form the preferred combined light output  44 . The first, second, and third laser beams  28 ,  30 , and  32  are interdigitated with the fourth, fifth, and sixth laser beams  36 ,  38 , and  40  to form the preferred combined light output  44 . 
     A second alternative embodiment for combining light output from multiple laser diode bars of the present invention is illustrated in FIG.  5 . The second alternative embodiment  56  includes the first laser diode bar  22 , the second laser diode bar  24 , a third laser diode laser bar  57 , and a second alternative mirror arrangement  58 . The first laser diode bar  22  emits the first, second, and third laser beams  28 ,  30 , and  32 , which comprise the first light output  34 . The second laser diode bar emits the fourth, fifth, and sixth laser beams  36 ,  38 , and  40 , which comprise the second light output  42 . The third laser diode bar  57  emits a seventh laser beam  59 , an eighth laser beam  60 , and a ninth laser beam  61 . The third laser diode bar  57  can be configured to emit more or fewer laser beams. 
     The seventh, eighth, and ninth laser beams  59 ,  60 , and  61  form a third light output  62 . The seventh, eighth, and ninth laser beams  59 ,  60 , and  61  define the preferred direction. The seventh, eighth, and ninth laser beams  59 ,  60 , and  61  are on a third pitch with third centers. The third centers define the common plane. 
     The second alternative mirror arrangement  58  reflects the first light output  34  into the preferred direction and such that the first centers lie in the common plane. The second alternative mirror arrangement  58  reflects the second light output  42  into the preferred direction such that the second centers lie in the common plane. The first, second and third light outputs  34 ,  42 , and  62  form a first alternative combined light output  63 . 
     A third alternative embodiment for combining light output from multiple laser diode bars of the present invention is illustrated in FIG.  6 . The third alternative embodiment  64  includes the first, second, and third laser diode bars  22 ,  24 , and  57 , a fourth laser diode bar  65 , and a third alternative mirror arrangement  66 . The first laser diode bar  22  emits the first, second, and third laser beams  28 ,  30 , and  32 , which comprise the first light output  34 . The second laser diode bar emits the fourth, fifth, and sixth laser beams  36 ,  38 , and  40 , which comprise the second light output  42 . The third laser diode bar  57  emits the seventh, eighth, and ninth laser beams  59 ,  60 , and  61 , which comprise the third light output  62 . The fourth laser diode bar  65  emits a tenth laser beam  67 , an eleventh laser beam  68 , and a twelfth laser beam  69 , which comprise a fourth light output  70 . The fourth laser diode bar  65  can be configured to emit more or fewer laser beams. The third alternative mirror arrangement  66  reflects the first, second, third, and fourth light outputs into the common plane and the preferred direction to form a second alternative combined light output  71 . 
     It will be readily apparent to one of ordinary skill in the art that additional laser diode bars can be added to the third alternative embodiment  64 . For example, a fifth leaser diode bar (not shown) could be added by modifying the third alternative mirror arrangement  66  and placing the fifth laser diode bar below the third alternative mirror arrangement  66 . 
     A fourth alternative mirror arrangement of the present invention is illustrated in FIG.  7 A. The fourth alternative mirror arrangement  72  includes a first prism housing  74 , first prisms  76 , and second prisms  78 . A cross section of the fourth alternative mirror arrangement  72  is illustrated in FIG.  7 B. The first prisms  76  are oriented towards a side of the first prism housing  74 . The second prisms  78  are oriented towards the opposite side of the first prism housing  74 . The first and second prisms  76  and  78  are placed in a first dove-cut groove  80  of the first prism housing  74 . The first and second prisms  76  and  78  can be held by adhesive, solder, or diffusion bonding. Alternatively, the first prisms and second prisms  76  and  78  can be integrally formed from a single glass block. The first and second prisms  76  and  78  reflect light from coatings  82 . The coatings  82  can be metallic coatings or multilayered dielectric coatings. In operation, the first light output  34  reflects from the first prisms  76 . The second light output  42  reflects from the second prisms  78 . Upon reflection, the first and second light outputs  34  and  42  combine to form the preferred combined light output  44 . 
     A fifth alternative mirror arrangement of the present invention is illustrated in FIG.  8 A. The fifth alternative mirror arrangement  84  includes a second prism housing  86 , third prisms  88 , and fourth prisms  90 . A cross section of the fifth alternative mirror arrangement  84  of the present invention is illustrated in FIG.  8 B. The third prisms  88  are oriented towards a side of the second prism housing  86 . The second prisms  90  are oriented towards the opposite side of the second prism housing  86 . The third and fourth prisms  88  and  90  are placed in a second dove-cut groove  92  of the second prism housing  86 . The third and fourth prisms  88  and  90  can be held by adhesive, solder, or diffusion bonding. Alternatively, the third and fourth prisms  88  and  90  can be integrally formed from a single glass block. The third and fourth prisms  88  and  90  reflect light from prism facets  94  by total internal reflection. In operation, the first light output  34  reflects from the third prisms  88 . The second light output  42  reflects from the fourth prisms  90 . Upon reflection, the first and second light outputs  34  and  42  combine to form the preferred combined light output  44 . 
     A first alternative mirror of the present invention is illustrated in FIG. 9. A prism  102  reflects light  104  from a cylindrically concave surface  106 . The cylindrically concave surface  106  focuses the light  104  into a line segment  108 . Focusing could also be performed by using a cylindrical lens (not shown). The light  104  focused into the line segment  108  could be coupled to a planar waveguide (not shown) placed at the line segment  108 . Alternatively, the cylindrically concave surface  106  or the cylindrical lens could be configured to collimate the light  104 . A second alternative mirror of the present invention replaces the cylindrically concave surface  106  of FIG. 9 with an aspherical surface. A third alternative mirror of the present invention replaces the cylindrically concave surface  106  of FIG. 9 with a diffractive surface. A fourth alternative mirror of the present invention replaces the cylindrically concave surface  106  of FIG. 9 with a non-imaging surface. 
     It will be readily apparent to one skilled in the art that other various modifications may be made to the preferred embodiment without departing from the spirit and scope of the invention as defined by the appended claims.