Higher Order Mode Optical Fiber Laser or Amplifier

Abstract

A method of producing higher power optical energy with an optical fiber can include providing a length of optical fiber having a core constructed so as to support more than one mode at a selected wavelength, the length of optical fiber comprising an active material for providing optical gain at the selected wavelength responsive to optical pumping, said optical gain being provided to the optical energy while propagating in at least one higher order mode of the core; providing a length of output optical fiber having a core; and providing for optical communication between the length of optical fiber and the core of the length of output optical fiber wherein the optical energy from the core of the length of optical fiber that experiences optical gain while propagating in at least one of the at least one higher order modes is communicated to the fundamental mode of the core of the length of output optical fiber.

1 . A method of producing higher power optical energy using an optical fiber by reducing non-linear effects, comprising:
 propagating optical energy having a selected wavelength in the fundamental mode of a core of a first length of optical fiber;   communicating the optical energy having the selected wavelength from the fundamental mode of the core of the first length of optical fiber to at least one higher order mode of a multimode core of a second length of optical fiber that comprises an active material for providing optical gain at the selected wavelength;   optically pumping the second length of optical fiber such that the optical energy experiences optical gain while propagating in at least one of the at least one higher order modes; and   communicating said optical energy that has experienced gain from the second length of optical fiber to the fundamental mode of a core of a third length of optical fiber for propagation thereby.   
   
   
       2 . The method of  claim 1  wherein communicating the optical energy having the selected wavelength from the core of the first length of optical fiber to the core of the second length of optical fiber comprises mode matching. 
   
   
       3 . The method of  claim 1  wherein communicating said optical energy that has experienced optical gain from the second length of optical fiber to the core of the third length of optical fiber comprises mode matching. 
   
   
       4 . The method of  claim 1  wherein communicating the optical energy having the selected wavelength from the core of the first length of optical fiber to the second length of optical fiber comprises splicing the first length of optical fiber to the second length of optical fiber. 
   
   
       5 . The method of  claim 1  wherein the active material comprises one of ytterbium, erbium or thulium. 
   
   
       6 . The method of  claim 1  wherein the core of the second length of optical fiber comprises a refractive index n 1  and the second length of optical fiber comprises an inner cladding surrounding the core and comprising a refractive index n 2  and a second cladding surrounding the inner cladding and having a refractive index n 3  and wherein n 1 >n 2 >n 3 . 
   
   
       7 . The method of  claim 6  wherein [(n 1 ) 2 −(n 2 ) 2 ] 1/2  is less than [(n 2 ) 2 −(n 3 ) 2 ] 1/2 . 
   
   
       8 . The method of  claim 7  wherein [(n 1 ) 2 −(n 2 ) 2 ] 1/2  is less about 0.17 and greater than about 0.05 and wherein [(n 2 ) 2 −(n 3 ) 2 ] 1/2  is less than about 0.5. 
   
   
       9 . The method of  claim 1  wherein said first length of optical fiber is single mode at the selected wavelength. 
   
   
       10 . The method of  claim 9  wherein the third length of optical fiber is single mode at the selected wavelength. 
   
   
       11 . The method of  claim 1  wherein the third length of optical fiber is single mode at the selected wavelength. 
   
   
       12 . The method of  claim 1  comprising configuring the lengths of optical fiber as a laser. 
   
   
       13 . The method of  claim 1  comprising configuring the lengths of optical fiber as an optical amplifier. 
   
   
       14 . A method of producing higher power optical energy using an optical fiber by reducing non-linear effects, comprising:
 providing a length of optical fiber having a core constructed so as to support more than one mode of optical energy at a selected wavelength, the length of optical fiber comprising an active material for providing optical gain at the selected wavelength responsive to the length of fiber being optically pumped, said optical gain being provided to the optical energy while propagating in at least one higher order mode of the core of the length of optical fiber;   providing a length of output optical fiber having a core;   providing for optical communication between the length of optical fiber and the core of the length of output optical fiber wherein the optical energy from the core of the length of optical fiber that experiences optical gain while propagating in at least one of the at least one higher order modes when the length of optical fiber is optically pumped is communicated to the fundamental mode of the core of the length of output optical fiber.   
   
   
       15 . The method of  claim 14  wherein the active material comprises one of erbium, ytterbium or thulium. 
   
   
       16 . The method of  claim 14  wherein the core of the length of optical fiber has a thickness of less than about 15 microns. 
   
   
       17 . The method of  claim 14  wherein the core of the length of optical fiber has a thickness of less than about 10 microns. 
   
   
       18 . The method of  claim 14  wherein the core of the length of optical fiber comprises a refractive index n 1  and wherein the length of optical fiber comprises an inner cladding surrounding the core and comprising a refractive index n 2  and a second cladding surrounding the inner cladding and having a refractive index n 3  and wherein n 1 >n 2 >n 3 . 
   
   
       19 . The method of  claim 18  wherein [(n 1 ) 2 −(n 2 ) 2 ] 1/2  is less than [(n 2 ) 2 −(n 3 ) 2 ] 1/2 . 
   
   
       20 . The method of  claim 19  wherein [(n 1 ) 2 −(n 2 ) 2 ] 1/2  is less about 0.17 and greater than about 0.05 and wherein [(n 2 ) 2 −(n 3 ) 2 ] 1/2  is less than about 0.5. 
   
   
       21 . The method of  claim 14  comprising:
 providing another length of optical fiber, the another length having a core; and   providing optical communication between the core of the another length of optical fiber and the core of the length of optical fiber wherein optical energy propagating in the fundamental mode of the core of the another length of optical fiber is communicated to the core of the length of optical fiber for experiencing optical gain while propagating in at least one higher order mode of the core of the length of optical fiber.