Tapered lensed fiber for focusing and condenser applications

Abstract

A tapered lensed fiber includes a tapered multimode fiber having a gradient-index core and an optical fiber attached to the tapered multimode fiber. A method for forming a tapered lensed fiber includes attaching an optical fiber to a multimode fiber having a gradient-index core, applying heat to a surface of the multimode fiber, and pulling the multimode fiber into a taper. The method also allows for forming a tapered polarization-maintaining fiber while preserving stress rods and polarization isolation properties of the polarization-maintaining fiber.

What is claimed is:  
     
         1 . A tapered lensed fiber, comprising: 
 a tapered multimode fiber having a gradient-index core; and    an optical fiber attached to the tapered multimode fiber.    
     
     
         2 . The tapered lensed fiber of  claim 1 , wherein the tapered multimode fiber is terminated with a radius of curvature.  
     
     
         3 . The tapered lensed fiber of  claim 2 , wherein the radius of curvature ranges from about 5 to 30 μm.  
     
     
         4 . The tapered lensed fiber of  claim 1 , wherein the optical fiber is a single-mode fiber.  
     
     
         5 . The tapered lensed fiber of  claim 4 , wherein the single-mode fiber is a polarization-maintaining fiber.  
     
     
         6 . A method for forming a tapered lensed fiber, comprising: 
 attaching an optical fiber to a multimode fiber having a gradient-index core;    applying heat to a surface of the multimode fiber; and    pulling the multimode fiber into a taper.    
     
     
         7 . The method of  claim 6 , wherein applying heat to the surface of the multimode fiber comprises using a resistive filament to provide the heat.  
     
     
         8 . The method of  claim 7 , wherein applying heat to the surface  6   f  the multimode fiber further comprises moving the resistive filament along the surface of the multimode fiber during heating.  
     
     
         9 . The method of  claim 6 , wherein applying heat to the surface of the multimode fiber and pulling the multimode fiber into a taper occur simultaneously.  
     
     
         10 . The method of  claim 6 , wherein pulling the multimode fiber into a taper comprises forming a radius of curvature at a distal end of the taper.  
     
     
         11 . The method of  claim 10 , wherein the radius of curvature ranges from about 5 to 30 μm.  
     
     
         12 . The method of  claim 6 , wherein attaching the multimode fiber to the optical fiber comprises fusion-splicing the multimode fiber to the optical fiber.  
     
     
         13 . The method of  claim 6 , wherein pulling the multimode fiber into a taper comprises simultaneously pulling the optical fiber and the multimode fiber in opposite directions along a longitudinal axis of the multimode fiber.  
     
     
         14 . The method of  claim 6 , wherein the optical fiber is a single-mode fiber.  
     
     
         15 . The method of  claim 14 , wherein the single-mode fiber is a polarization-maintaining fiber.  
     
     
         16 . A method for forming a tapered polarization-maintaining fiber, comprising: 
 attaching a polarization-maintaining fiber to a multimode fiber having a gradient-index core;    applying heat to a surface of the multimode fiber; and    pulling the multimode fiber into a taper.    
     
     
         17 . The method of  claim 16 , wherein applying heat to the surface of the multimode fiber comprises using a resistive filament to provide the heat.  
     
     
         18 . The method of  claim 16 , wherein applying heat to the surface of the multimode fiber and pulling the multimode fiber into a taper occur simultaneously.  
     
     
         19 . The method of  claim 16 , wherein pulling the multimode fiber into a taper comprises forming a radius of curvature at a distal end of the taper.  
     
     
         20 . The method of  claim 16 , wherein attaching the polarization-maintaining fiber to a multimode fiber comprises fusion-splicing the polarization-maintaining fiber to the multimode fiber.  
     
     
         21 . A tapered polarization-maintaining fiber, comprising: 
 a tapered multimode fiber having a gradient-index core; and    a polarization-maintaining fiber attached to the tapered multimode fiber.    
     
     
         22 . The tapered polarization-maintaining fiber of  claim 21 , wherein the multimode fiber is terminated with a radius of curvature.  
     
     
         23 . The tapered polarization-maintaining fiber of  claim 22 , wherein the radius of curvature ranges from about 5 to 30 μm.