Method for tailoring the dopant profile in a laser crystal using zone processing

Abstract

A lasing medium having a tailored dopant concentration and a method of fabrication thereof is disclosed. The lasing medium has a single crystal having a continuous body having a selected length, wherein the crystal comprises dopant distributed along the length of the body to define a dopant concentration profile. In one embodiment, the dopant concentration profile results in a uniform heating profile. A method of fabricating a laser crystal having a tailored dopant concentration profile includes arranging a plurality of polycrystalline segments together to form an ingot, the polycrystalline segments each having dopant distributed, providing a crystal seed at a first end of the ingot, and moving a heating element along the ingot starting from the first end to a second end of the ingot, the moving heating element creating a moving molten region within the ingot while passing therealong.

1 . A method of fabricating a single, continuous laser crystal having a tailored dopant concentration profile, the method comprising:
 arranging a plurality of polycrystalline segments together to form an ingot, the polycrystalline segments each having dopant distributed therein;   providing a crystal seed at a first end of the ingot;   moving a heating element along the ingot starting from the first end to a second end of the ingot, the moving heating element creating a moving molten region within the ingot while passing therealong.   
     
     
         2 . The method of  claim 1 , wherein the dopant comprises neodymium, ytterbium, erbium, holmium, or a combination thereof. 
     
     
         3 . The method of  claim 1 , wherein the heating element uses RF induction. 
     
     
         4 . The method of  claim 1 , wherein each of the segments has a different dopant concentration from other segments. 
     
     
         5 . The method of  claim 1 , wherein each of the segments has a different length. 
     
     
         6 . The method of  claim 1 , wherein the seed crystal comprises a dopant concentration equal to a target concentration at the first end of the ingot. 
     
     
         7 . The method of  claim 1 , wherein a segment at the first end of the ingot has a higher dopant concentration than a segment at the second end of the ingot. 
     
     
         8 . The method of  claim 1 , wherein moving the heating element along the ingot comprises the heating element surrounding a portion of a length of the ingot. 
     
     
         9 . The method of  claim 1 , wherein interfaces between the moving molten region and the segments of the ingot are substantially normal to the axis. 
     
     
         10 . The method of  claim 1 , wherein the crystal comprises YAG (Y 3 Al 5 O 12 ), YLF (YLiF 4 ), GGG (Gd 3 Ga 5 O 12 ). 
     
     
         11 . A lasing medium comprising:
 a single crystal having a continuous body having a selected length, wherein the crystal comprises dopant distributed along the length of the body to define a dopant concentration profile.   
     
     
         12 . The lasing medium of  claim 11 , wherein the dopant concentration profile results in a substantially uniform heating profile. 
     
     
         13 . The lasing medium of  claim 11 , wherein the laser crystal is fabricated with the method of  claim 1 , and wherein the laser crystal is machined to a final size. 
     
     
         14 . The lasing medium of  claim 13 , wherein the laser crystal is machined using saw cutting, core drilling, grinding, polishing, coating, or a combination thereof. 
     
     
         15 . The lasing medium of  claim 11 , wherein the dopant comprises neodymium, ytterbium, erbium, holmium, or a combination thereof. 
     
     
         16 . The lasing medium of  claim 11 , wherein the crystal is YAG (Y 3 Al 5 O 12 ), YLF (YLiF 4 ), or GGG (Gd 3 Ga 5 O 12 ). 
     
     
         17 . The lasing medium of  claim 11 , wherein the lasing medium is in the shape of a rod or slab or configured as a planar waveguide. 
     
     
         18 . The lasing medium of  claim 11 , wherein the dopant concentration is a function of distance along the length of the crystal. 
     
     
         19 . A single crystal having a tailored dopant concentration profile, produced by a process comprising the steps of:
 arranging a plurality of polycrystalline segments together to form an ingot, the polycrystalline segments each having dopant distributed therein;   providing a crystal seed at a first end of the ingot;   moving a heating element along the ingot starting from the first end to a second end of the ingot, the moving heating element creating a moving molten region within the ingot while passing therealong.