Fabrication of high air fraction photonic band gap (pbg) fibers

Abstract

A photonic band gap fiber and method of making thereof is provided. The fiber is made of a non-silica-based glass and has a longitudinal central opening, a microstructured region having a plurality of longitudinal surrounding openings, and a jacket. The air fill fraction of the microstructured region is at least about 40%. The fiber may be made by drawing a preform into a fiber, while applying gas pressure to the microstructured region. The air fill fraction of the microstructured region is changed during the drawing.

1 . A method of making a fiber comprising the steps of: 
 providing a cylindrical preform comprising a non-silica-based glass, wherein the non-silica-based glass defines a longitudinal central hole and a plurality of longitudinal surrounding holes, the preform includes a first structured region disposed around the central hole including all of the surrounding holes and the non-silica glass therebetween and a jacket of non-silica based glass surrounding the structured region; and wherein the first structured region of the preform has a first air fill fraction;    pressurizing surrounding holes of the preform with a gas; and    drawing the preform into a fiber at an elevated temperature wherein a second structured region of the fiber has a second air fill fraction;    wherein the second air fill fraction of the structured region of the fiber is greater than the first air fill fraction of the structured region of the preform, and wherein the second air fill fraction of the fiber is at least about 40%.    
   
   
       2 . The method of  claim 1 , wherein a cross-sectional area of each of the plurality of longitudinal surrounding holes of the preform are approximately the same.  
   
   
       3 . The method of  claim 1 , wherein a first cross-sectional area of the longitudinal central hole of the preform is larger than a second cross-sectional area of each of the plurality of surrounding holes of the preform.  
   
   
       4 . The method of  claim 3 , wherein the first cross-sectional area of the longitudinal central hole of the preform is at least two times the second cross-sectional area of each of the plurality of longitudinal surrounding holes of the preform.  
   
   
       5 . The method of  claim 1 , wherein the gas is applied to the plurality of surrounding holes of the preform at a first gas pressure and wherein the method further comprising the step of: 
 applying a second gas at a second gas pressure to the longitudinal central hole of the preform during the drawing step.    
   
   
       6 . The method of  claim 5 , wherein the second gas pressure in the longitudinal central hole of the preform is controlled independently from the first gas pressure in the plurality of surrounding holes of the preform.  
   
   
       7 . The method of  claim 6 , wherein the second gas pressure in the longitudinal central hole of the preform is less than the first gas pressure in the plurality of surrounding holes of the preform.  
   
   
       8 . The method of  claim 1 , wherein a pressure of the gas is controlled and is substantially constant during the drawing step.  
   
   
       9 . The method of  claim 1 , wherein the gas is selected from the group consisting of inert gases, nitrogen, argon, and helium.  
   
   
       10 . The method of  claim 1 , wherein the second air fill fraction of the fiber is at least about 70%.  
   
   
       11 . The method of  claim 1 , wherein the second air fill fraction of the fiber is at least about 90%.  
   
   
       12 . The method of  claim 1 , wherein an overall diameter of the fiber is from about 80 microns to about 1000 microns.  
   
   
       13 . The method of  claim 1 , wherein the non-silica-based glass is a chalcogenide glass.  
   
   
       14 . The method of  claim 1 , wherein the non-silica-based glass is selected from the group consisting of chalcogenide glass, germanate glass, phosphate glass, tellurite glass, borate glass, antimonate glass, and halide glass.  
   
   
       15 . The method of  claim 1 , wherein the first air fill fraction of the preform is less than about 30%.