High-power, single-mode fiber sources

Abstract

An optical apparatus includes one or more pump sources situated to provide laser pump light, and a gain fiber optically coupled to the one or more pump sources, the gain fiber including an actively doped core situated to produce an output beam, an inner cladding and outer cladding surrounding the doped core and situated to propagate pump light, and a polymer cladding surrounding the outer cladding and situated to guide a selected portion of the pump light coupled into the inner and outer claddings of the gain fiber. Methods of pumping a fiber sources include generating pump light from one or more pump sources, coupling the pump light into a glass inner cladding and a glass outer cladding of a gain fiber of the fiber source such that a portion of the pump light is guided by a polymer cladding surrounding the glass outer cladding, and generating a single-mode output beam from the gain fiber.

We claim: 
     
         1 . A method of pumping a high power fiber source, comprising:
 generating pump light at a pump wavelength from one or more pump sources;   coupling the pump light into a glass inner cladding and a glass outer cladding of a gain fiber of the fiber source such that a portion of the pump light is guided by a polymer cladding surrounding the glass outer cladding; and   generating a single-mode output beam from the gain fiber.   
     
     
         2 . The method of  claim 1 , wherein 10% or more of the pump light is guided by the polymer cladding. 
     
     
         3 . The method of  claim 1 , wherein the pump light has a wavelength between 910 nm and 920 nm. 
     
     
         4 . The method of  claim 1 , wherein the length of the gain fiber is selected based on the coupling of the pump light into the glass inner and outer claddings so as to allow the power of the output beam to be 1 kW or greater and single-mode with out of band optical nonlinearities being generated that are 20% or less than the power of the output beam.