Multimode long period fiber bragg grating machined by ultrafast direct writing

Abstract

An optical fiber with an integral photonic crystal structure. The optical fiber core is formed of a non-photosensitive material having an initial index of refraction. The optical fiber core includes a substantially cylindrical surface, a longitudinal core axis, a core radius, and a number of index-altered portions having an altered index of refraction different from the initial cladding index of refraction. The index-altered portions are arranged within the non-photosensitive material of the optical fiber core to form a photonic crystal structure. The photonic crystal structure may be a one dimensional, a two dimensional, or a three dimensional photonic crystal structure.

1 . An optical fiber with an integral photonic crystal section, comprising:
 an optical fiber core formed of a non-photosensitive material having an initial index of refraction, the optical fiber core includes;
 a substantially cylindrical surface; 
 a longitudinal core axis; 
 a core radius; and 
 a plurality of index-altered portions having an altered index of refraction different from the initial index of refraction; 
   wherein the plurality of index-altered portions are arranged within the non-photosensitive material of the optical fiber core to form a photonic crystal structure.   
   
   
       2 . An optical fiber according to  claim 1 , wherein the non-photosensitive material of the optical fiber core includes at least one of: fused silica; borosilicate; quartz; zirconium fluoride; silver halide; chalcogenide glass; optical plastic; clear fused quartz; aluminosilicate; polymethylmeth-acrylate; polystyrene; acrylic; or arsenic trioxide. 
   
   
       3 . An optical fiber according to  claim 1 , wherein the optical fiber core is a multimode optical fiber core. 
   
   
       4 . A optical fiber according to  claim 3 , wherein the core radius of the multimode optical fiber core is in the range of about 10 μm to about 200 μm. 
   
   
       5 . A multimode optical fiber according to  claim 4 , wherein the core radius of the multimode optical fiber core is in the range of about 25 μm to about 31.25 μm. 
   
   
       6 . An optical fiber according to  claim 1 , wherein the altered index of refraction of the plurality of index-altered portions is altered by selective irradiation of the non-photosensitive material by pulses of ultrafast laser light. 
   
   
       7 . An optical fiber according to  claim 1 , wherein:
 the non-photosensitive material of the optical fiber core has an initial crystallinity; and   the plurality of index-altered portions have an altered crystallinity which is less than the initial crystallinity of the non-photosensitive material.   
   
   
       8 . An optical fiber according to  claim 7 , wherein the altered crystallinity of the plurality of index-altered portions is altered by selective irradiation of the non-photosensitive material by pulses of ultrafast laser light. 
   
   
       9 . An optical fiber according to  claim 1 , wherein the photonic crystal structure formed in the optical fiber core is a one dimensional photonic crystal structure. 
   
   
       10 . An optical fiber according to  claim 1 , wherein the photonic crystal structure formed in the optical fiber core is a two dimensional photonic crystal structure. 
   
   
       11 . An optical fiber according to  claim 1 , wherein the photonic crystal structure formed in the optical fiber core is a three dimensional photonic crystal structure. 
   
   
       12 . An optical fiber according to  claim 1 , wherein the photonic crystal structure formed in the optical fiber core includes a defect. 
   
   
       13 . An optical fiber with integral diffractive coupling optics, comprising:
 an optical fiber core formed of a non-photosensitive material having an initial index of refraction, the optical fiber core includes;
 a substantially planar end surface; 
 a substantially cylindrical surface; 
 a longitudinal core axis; 
 a core radius; and 
 a coupling section adjacent to the substantially planar end surface with a plurality of index-altered portions having an altered index of refraction different from the initial index of refraction; 
   wherein the plurality of index-altered portions are arranged within the coupling section of the optical fiber core to form the integral diffractive coupling optics.   
   
   
       14 . An optical fiber according to  claim 13 , wherein the non-photosensitive material of the optical fiber core includes at least one of: fused silica; borosilicate; quartz; zirconium fluoride; silver halide; chalcogenide glass; optical plastic; clear fused quartz; aluminosilicate; polymethylmeth-acrylate; polystyrene; acrylic; or arsenic trioxide. 
   
   
       15 . An optical fiber according to  claim 13 , wherein the optical fiber core is a multimode optical fiber core. 
   
   
       16 . An optical fiber according to  claim 15 , wherein the core radius of the multimode optical fiber core is in the range of about 10 μm to about 200 μm. 
   
   
       17 . An optical fiber according to  claim 13 , wherein the altered index of refraction of the plurality of index-altered portions is altered by selective irradiation of the non-photosensitive material by pulses of ultrafast laser light. 
   
   
       18 . An optical fiber according to  claim 13 , wherein:
 the plurality of index-altered portions are a plurality of concentric circular annular portions centered on the longitudinal core axis of the optical fiber core; and   the plurality of concentric circular annular portions are sized and arranged such that the integral diffractive coupling optics formed in the coupling section of the optical fiber core is a circular two dimensional diffractive optical lens.   
   
   
       19 . An optical fiber according to  claim 13 , wherein:
 the plurality of index-altered portions are a plurality of concentric elliptical annular portions centered on the longitudinal core axis of the optical fiber core;   the plurality of concentric elliptical annular portions are sized and arranged such that the integral diffractive coupling optics formed in the coupling section of the optical fiber core is an elliptical two dimensional diffractive optical lens.   
   
   
       20 . An optical fiber according to  claim 13 , wherein:
 the plurality of index-altered portions are a plurality of parallel lines perpendicular to the longitudinal core axis of the optical fiber core;   the plurality of parallel lines are sized and arranged such that the integral diffractive coupling optics formed in the coupling section of the optical fiber core is a one dimensional diffractive optical lens.