High power high efficiency cladding pumping fiber laser

Abstract

In the present invention, methods and apparatus for making efficient cladding pumping fiber lasers is disclosed. In particular, new fiber cladding geometry and new method of coupling pumping laser into an optical fiber are disclosed. Both aspects of the present invention will facilitate the realization of high-efficiency and high-power fiber lasers. In the present invention, cladding boundary geometry structures that can prevent the formation of local modes are disclosed. Besides the cladding geometry, methods for efficient coupling of diode lasers into a laser fiber for high power injection are also disclosed. Essentially, the new methods make it possible to transmit diode laser beams for a long distance with substantially the same brightness. In other words, with the methods and apparatus disclosed, a laser beam from a laser diode array with collimating structures can be transmitted for a long distance while the beam spot dimension including beam divergence can be kept substantially unchanged even if the beam from said array is not substantially collimated. With the method taught in the present invention, laser diode array modules can be formed with laser diode arrays (LDA) with collimating structures and relay systems. Because of the brightness conservation nature of the modules, when a plurality of such modules (such as 3, 9 or more than 200 pieces) are combined, the beams from the arrays can be efficiently coupled into an optical fiber. Thus the pumping laser coupling method can be used for the construction of high-efficiency and high-power fiber lasers. Thus, the fiber lasers of this invention may comprise of a fiber laser core doped with active species, a symmetry-broken inner cladding or a multiple-imaging inner cladding surrounding said core, a plurality of brightness substantially-conserved laser diode array module for coupling the beam from said laser diode array module into said inner cladding.An apparatus for a high efficiency cladding pumping fiber laser component includes a laser fiber having a core doped with active species disposed along an axis. A symmetry- broken inner cladding surrounds said core for transmitting optical energy from the inner cladding to said core. The symmetry - broken inner cladding has a substantially rectilinear cross - section with respect to the axis with at least two pair opposing sides. At least one side of each pair of each opposing sides is disposed in nonparallel relationship to its respective opposed side whereby the inner cladding has a symmetry - broken cross - section shape that minimizes local modes in the inner cladding.

1. A high-efficiency cladding pumping fiber laser apparatus comprising:
 a laser fiber having cladding with its  having a core doped with at least one active species and defining an aperture,  
 at least one laser diode array module,  for emitting a laser beam with a beam spot dimension,  
 an imaging optical system,  
 wherein said  the imaging optical system is disposed between said  the laser diode array module and an  the aperture of said  the laser fiber and focuses the laser beam from said  the laser diode array module onto the aperture of said  the laser fiber; and wherein said  the laser diode array module comprises at least one laser diode array with a  the beam having fast and slow axis divergence, a collimating structure, and an optical relay system; and wherein said  the imaging optical relay  system has at least one optical element for beam relay and is disposed between said  the laser diode array module and said  the laser fiber, whereby the laser beam from said  the laser diode array module is relayed to a more distant point with the beam spot dimension being kept substantially unchanged.  
 
     
     
       2. An  The apparatus of  claim 1 , wherein said  the laser fiber has a symmetry-broken inner cladding surround the core of said  the laser fiber. 
     
     
       3. An  The apparatus of  claim 2 , wherein said  the symmetry-broken cladding is symmetry-broken circular cladding. 
     
     
       4. An  The apparatus of  claim 2 , wherein said  the symmetry-broken cladding is symmetry-broken rectangular cladding. 
     
     
       5. An  The apparatus of  claim 1 , wherein said  the laser fiber has a multiple-imaging cladding surrounding the core of said  the laser fiber. 
     
     
       6. An  The apparatus of  claim 5 , wherein said  the multiple-imaging cladding is rectangular-like multiple-imaging cladding. 
     
     
       7. An  The apparatus of  claim 1 , wherein said  the optical relay system is a cylindrical lens. 
     
     
       8. An  The apparatus of  claim 1 , wherein said  the optical relay system is a 1:1 4f cylindrical relay. 
     
     
       9. An  The apparatus of  claim 1 , wherein said  the optical relay system is a non-1:1 cylindrical telecentric relay. 
     
     
       10. An  The apparatus of  claim 1 , wherein said  the collimating structure includes a plurality of fold prisms. 
     
     
       11. A high-efficiency diode-pumped solid state laser apparatus comprising:
 a laser rod doped with active species defining an aperture,  
 at least one laser diode array module for emitting a beam with a beam spot dimension,  
 an imaging optical system,  
 wherein said  the imaging optical system is disposed between said  the laser diode array module and an  the aperture of said  the laser rod and focuses the beam from said  the laser diode array module onto the aperture of said  the laser rod; and wherein said  the laser diode array module comprises at least one laser diode array with a  the beam having fast and slow axis divergence, a collimating structure, and an optical relay system; and wherein said  the optical relay has at least one optical element for beam relay and is disposed between said  the laser diode array and said  the laser rod, whereby the laser beam from said  the laser diode array module is relayed to a more distant point with the beam spot dimension being kept substantially unchanged.  
 
     
     
       12. An  The apparatus of  claim 11 , wherein said  the optical relay system is a cylindrical lens. 
     
     
       13. An  The apparatus of  claim 11 , wherein said  the optical relay system is a 1:1 4f cylindrical relay. 
     
     
       14. An  The apparatus of  claim 11 , wherein said  the optical relay system is a non-1:1 cylindrical telecentric relay. 
     
     
       15. An apparatus for laser beam transmission comprising:
 an optical fiber for laser beam transmission,  
 at least one laser diode array module for emitting a beam with a beam spot dimension,  
 an imaging optical system,  
 wherein said  the imaging optical system is disposed between said  the laser diode array module and an  the aperture of said  the optical fiber and focuses the beam from said  the module onto the aperture of said  the optical fiber; and wherein said  the laser diode array module comprises at least one laser diode array with a  the beam having fast and slow axis divergence, a collimating structure, and an optical relay system; and wherein said  the optical relay has at least one optical element for beam relay and is disposed between said  the laser diode array and said  the optical fiber, whereby the laser beam from said  the laser diode array is relayed to a more distant point with the beam spot dimension being kept substantially unchanged.  
 
     
     
       16. An  The apparatus of  claim 15 , wherein said  the optical relay system is a cylindrical lens. 
     
     
       17. An  The apparatus of  claim 15 , wherein said  the optical relay system is a 1:1 4f cylindrical relay. 
     
     
       18. An  The apparatus of  claim 15 , wherein said  the optical relay system is a non-1:1 cylindrical telecentric relay. 
     
     
       19. An apparatus for a high efficiency cladding pumping fiber laser component comprising:
   a laser fiber including a core doped with active species disposed along an axis;        a symmetry - broken inner cladding surrounding said core for transmitting optical energy from the inner cladding to said core;        the symmetry - broken inner cladding having a substantially rectilinear cross - section with respect to the axis with at least two pair opposing sides; and,        at least one side of each pair of each opposing sides disposed in nonparallel relationship to its respective opposed side whereby the inner cladding has a symmetry - broken cross - section shape that minimizes local modes in the inner cladding.      
     
     
       20. The apparatus for a high efficiency cladding pumping fiber laser in accordance with  claim 19  wherein:
   each of the opposing sides are disposed in nonparallel relationship with respect to a rectangle.      
     
     
       21. The apparatus for a high efficiency cladding pumping fiber laser in accordance with  claim 19  wherein:
   the at least one side disposed in nonparallel relationship includes a first segment disposed in a first nonparallel relationship and a second segment disposed in a second nonparallel relationship.      
     
     
       22. The apparatus for a high efficiency cladding pumping fiber laser in accordance with  claim 19  including:
   an outer cladding disposed adjacent the inner cladding.      
     
     
       23. A high efficiency cladding pumping fiber laser component comprising:
   a laser fiber including a core doped with active species disposed along an axis;        a symmetry - broken inner cladding surrounding said core for transmitting optical energy from the inner cladding to said core;        at least one light path disposed along the symmetry - broken inner cladding;        the symmetry - broken inner cladding having a cross - section shape that includes multiple imaging cladding surrounding the core between the light path and the laser fiber whereby the inner cladding has a symmetry - broken cross - section shape that minimizes local modes in the inner cladding.      
     
     
       24. The high efficiency cladding pumping fiber laser component of  claim 23 , wherein
   said multiple - imaging cladding is rectangular - like multiple - imaging cladding.      
     
     
       25. The high efficiency cladding pumping fiber laser component of  claim 23 , further including:
   an outer cladding disposed adjacent the inner cladding.