Phase and Amplitude Control for Optical Fiber Output

Abstract

A method for shaping an output light beam from an optical fiber by controlling the phase and amplitude of the beam by producing beam shaping elements on an exit facet of the optical fiber by direct surface texturing of the exit facet, where a controlled phase difference is achieved across the fiber cross-section over a predefined pattern. The optical fiber can be a single mode fiber or a multi-mode fiber. Either a binary or a complex phase difference can be achieved. Also disclosed is the related system for shaping an output light beam from an optical fiber.

What is claimed is: 
     
         1 . A system for shaping an output light beam, the system comprising:
 an optical fiber configured to transmit the output light beam; and   an exit facet of the optical fiber, wherein the exit facet comprises a surface textured according to a texturing pattern designed to initiate a static phase difference between a first portion of the output light beam and a second portion of the output light beam such that the textured surface has a plurality of varying depths in the exit facet.   
     
     
         2 . The system of  claim 1 , wherein the optical fiber comprises chalcogenide, fluoride, or tellurite. 
     
     
         3 . The system of  claim 1 , wherein the optical fiber comprises a solid core photonic crystal fiber. 
     
     
         4 . The system of  claim 1 , wherein the optical fiber is a single mode fiber. 
     
     
         5 . The system of  claim 1 , wherein the optical fiber is a multi-mode fiber. 
     
     
         6 . The system of  claim 1 , wherein no additional material is attached to or deposited on the exit facet of the optical fiber to initiate the static phase difference. 
     
     
         7 . The system of  claim 1 , wherein the surface is stamped to form the textured surface. 
     
     
         8 . The system of  claim 1 , wherein the exit facet comprises a plurality of beam shaping elements formed by the textured surface. 
     
     
         9 . The system of  claim 1 , wherein the textured surface comprises multiple steps created in a spiral pattern, and wherein the output light beam is in a shape of a ring with no light in the center. 
     
     
         10 . The system of  claim 1 , wherein the texturing pattern is a periodic texturing pattern. 
     
     
         11 . The system of  claim 1 , wherein the texturing pattern includes an array of circular symmetric lines. 
     
     
         12 . The system of  claim 1 , wherein the texturing pattern includes an array of non-circular symmetric lines. 
     
     
         13 . A optical fiber for shaping an output light beam transmitted through the optical fiber, the optical fiber comprising:
 an exit facet;   a first step formed on a surface of a first portion of the exit facet according to a texturing pattern designed to initiate a static phase difference between a first portion of the output light beam and a second portion of the output light beam; and   a second step formed on the surface of a second portion of the exit facet according to the texturing pattern, wherein a first depth of the first step in the surface of the exit facet is different than a second depth of the second step in the surface of the exit facet.   
     
     
         14 . The optical fiber of  claim 13 , wherein the static phase difference between the first portion of the output light beam and the second portion of the output light beam is a π phase shift. 
     
     
         15 . The optical fiber of  claim 14 , wherein a difference between the first depth and the second depth is determined according to the equation d=λ/(2(n−1)), wherein n represents an effective index of the fundamental mode, wherein λ represents an operating wavelength, and wherein d represents the difference between the first depth and the second depth. 
     
     
         16 . The optical fiber of  claim 13 , further comprising:
 a plurality of steps, including the first step and the second step, formed in a spiral pattern on the surface of the exit facet according to the texturing pattern, wherein the output light beam is in the shape of a ring with no light in the center.   
     
     
         17 . The optical fiber of  claim 13 , wherein the texturing pattern is a periodic texturing pattern. 
     
     
         18 . A optical fiber for shaping an output light beam transmitted through the optical fiber, the optical fiber comprising:
 an exit facet;   a first step formed on a surface of a first portion of the exit facet according to a texturing pattern designed to initiate a static phase difference between a first portion of the output light beam and a second portion of the output light beam; and   a second step formed on the surface of a second portion of the exit facet according to the texturing pattern, wherein a first depth of the first step in the surface of the exit facet is different than a second depth of the second step in the surface of the exit facet, and wherein the first step and the second step are formed such that, after passing through the exit facet, the first portion of the output light beam and the second portion of the output light beam differ in phase according to the static phase difference.   
     
     
         19 . The optical fiber of  claim 18 , wherein a light beam with a substantially uniform phase is transmitted through an entire core of the optical fiber to produce the output light beam. 
     
     
         20 . The optical fiber of  claim 18 , further comprising:
 a plurality of steps, including the first step and the second step, formed in a spiral pattern on the surface of the exit facet according to the texturing pattern, wherein the output light beam is in the shape of a ring with no light in the center.