US2006198578A1PendingUtilityA1

Optical structure writing system

19
Individually held — no corporate assignee on recordPriority: Feb 25, 2003Filed: Feb 25, 2004Published: Sep 7, 2006
Est. expiryFeb 25, 2023(expired)· nominal 20-yr term from priority
Inventors:Goran Lars Edvell
G02B 6/02133G02B 6/02138
19
PatentIndex Score
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Claims

Abstract

The present invention relates to a system for writing an optical structure in a waveguide. The system including, means for splitting a light beam into two coherent writing beams, an optical circuit for directing the writing beams along substantially the same optical path in opposite directions such that they produce an interference pattern in an interference region substantially within the waveguide to write the optical structure, said optical circuit including at least two acousto-optic modulators (AOMs) configured to enable a controllable phase shift to be applied to a light beam propagating therethrough, the two AOMs being arranged such that, in use, each AOM shifts the phase of only one of the writing beams, to thereby provide a controllable phase difference between the writing beams.

Claims

exact text as granted — not AI-modified
1 . A system for writing an optical structure in a waveguide including: 
 means for splitting a light beam into two coherent writing beams,    an optical circuit for directing the writing beams along substantially the same optical path in opposite directions such that they produce an interference pattern in an interference region substantially within the waveguide to write the optical structure, said optical circuit including at least two acousto-optic modulators (AOMs) configured to enable a controllable phase shift to be applied to a light beam propagating therethrough, the two AOMs being arranged such that, in use, each AOM shifts the phase of only one of the writing beams, to thereby provide a controllable phase difference between the writing beams.    
   
   
       2 . A system as claimed in  claim 1  wherein at least one AOM is configured to shift the phase of each writing beam.  
   
   
       3 . A system as claimed in  claim 1  wherein the AOMs are configured to shift the phase of the same writing beam.  
   
   
       4 . A system as claimed in any one of the preceding claims, wherein the system includes means for providing a relative movement between the waveguide and the interfering writing beams to allow writing of an extended optical structure in the waveguide.  
   
   
       5 . A system as claimed in  claim 4 , which further includes means for providing a relative movement between the means for splitting the light beam and the interfering writing beams wherein, in use, the means for splitting the light beam and the waveguide undergo identical movement relative to the writing beams, and wherein a relative phase shift is induced between the writing beams to balance a velocity of variations in the interference pattern and a velocity of the movement of the waveguide relative to the writing beams.  
   
   
       6 . A system as claimed in  claim 5  wherein the system is configured to enable optical structures with varying phase and/or pitch to be written by controlling relative phase shift between the writing beams using the AOMs to detune the velocity balance between the variations in the interference pattern and the movement of the waveguide relative to the writing beams.  
   
   
       7 . A system as claimed in any one of the preceding claims, wherein the AOMs are arranged to enable dithering of the interference fringes in the interference pattern for writing optical structures of varying amplitude profile.  
   
   
       8 . A system as claimed in any one of the preceding claims, wherein the AOMs are configured to move the interference region during writing of the optical structures.  
   
   
       9 . A system as claimed in any one of the preceding claims wherein the AOMs are configured to enable the angle between the converging writing beams to varied.  
   
   
       10 . A system as claimed in any one of the preceding claims, wherein the intensity of the writing beams is controlled using partial Bragg diffraction driving of at least one AOM.  
   
   
       11 . A system as claimed in any one of the preceding claims, wherein the splitting means comprises a phase mask.  
   
   
       12 . A system as claimed in any one of the preceding claims, wherein the system further includes means for focusing the writing beams in the interference region.  
   
   
       13 . A system as claimed in any one of the preceding claims, wherein the optical circuit is substantially arranged in a Sagnac interferometer format.  
   
   
       14 . A system as claimed in any one of the preceding claims, wherein the waveguide comprises an optical fibre.  
   
   
       15 . A method of writing an optical structure in a waveguide, the method including the steps of: 
 splitting a light beam into two coherent writing beams,    directing the two writing beams along substantially the same optical path in opposite directions, such that they produce an interference pattern in an interference region substantially within the waveguide; and    controlling a phase difference between the two writing beams by selectively using at least two acousto-optic modulators (AOMs) to shift the phase of at least one of the writing beams.    
   
   
       16 . A method as claimed in  claim 15  in which controlling the phase difference between the two writing beams includes using the two AOMs to shift the phase of the same writing beam.  
   
   
       17 . A method as claimed in  claim 15  in which controlling the phase difference between the two writing beams includes using the two AOMs to shift the phase of different writing beams.  
   
   
       18 . A method as claimed in any one of  claims 15  to  17 , which further includes moving the waveguide relative to the interfering writing beams to write extended optical structures in the waveguide.  
   
   
       19 . A method as claimed in  claim 18 , wherein the method includes moving a beam splitting means relative to the writing beams in concert with the waveguide, and 
 inducing a relative phase shift between the writing beams, for balancing of a velocity of variations in the interference pattern and a velocity of the movement of the waveguide relative to the writing beams.    
   
   
       20 . A method as claimed in  claim 19  wherein the method includes detuning the extent of velocity balance between the variations in the interference pattern and the movement of the waveguide, by controlling the relative phase shift between the writing beams.  
   
   
       21 . A method as claimed in any one of  claims 15  to  20 , wherein the method includes dithering the interference fringes with respect to the optical waveguide using the at least one AOM.  
   
   
       22 . A method as claimed in any one of  claims 15  to  21 , wherein the method includes moving the interference region during writing of the optical structure using the at least one AOM.  
   
   
       23 . A method as claimed in any one of  claims 15  to  21 , wherein the method includes changing the angle between the converging writing beams using the AOMs.  
   
   
       24 . A method as claimed in any one of  claims 15  to  23 , wherein the method includes controlling the intensity of the interfering writing beams using partial Bragg diffraction driving of at least one AOM.  
   
   
       25 . A method as claimed in any one of  claims 15  to  24 , wherein the method further includes focusing of the writing beams in the interference region.  
   
   
       26 . An interferometer for writing an optical structure in a waveguide moving relative to interfering writing beams of the interferometer, the interferometer including at least two acousto-optic modulators (AOM) for introducing a controlled phase difference between the writing beams, wherein, in use, a phase error of an interference pattern created by the interferometer is less than about ±10° for a relative movement of the waveguide of about 100 mm.  
   
   
       27 . An interferometer as claimed in  claim 26 , wherein the phase error is about ±3°.  
   
   
       28 . An interferometer as claimed in either of claims  26  or  27  wherein the interferometer includes two AOMs.  
   
   
       29 . A system as claimed in  claim 29  wherein the interferometer is arranged so the writing beams travel along substantially the same optical path in opposite directions, and wherein the AOMs are disposed such that, in use, both writing beams propagate through at least two AOMs in a manner such that each AOM shifts the phase of only one of the writing beams.  
   
   
       30 . A waveguide including an optical structure written using the method of any one of  claims 15  to  25   
   
   
       31 . A system for writing an optical structure in a waveguide, substantially as herein described with reference to the accompanying drawings.  
   
   
       32 . A method of writing an optical structure in a waveguide, substantially as herein described with reference to the accompanying drawings.  
   
   
       33 . An interferometer substantially as herein described with reference to the accompanying drawings.

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