Controlled phase delay between beams for writing bragg gratings
First Claim
1. A method of writing an extended grating structure in a photosensitive waveguide comprising:
- utilising at least two overlapping beams of light to form an interference pattern,moving the waveguide through an overlap region defined by said overlapping beams,simultaneously varying the phase of at least one of the beams relative to at least one of the other beams utilising a phase modulator,thereby variably controlling the velocity of the maxima within said interference pattern so that such velocity is different from the velocity of the photosensitive waveguide within the overlap region for the duration of the writing, excluding any periods of velocity change when the velocity of said maxima momentarily equals the velocity of the waveguide, wherein;
the phase modulator comprises a non-mechanical means for effecting the phase modulation, andvariation of the velocity of the maxima within the overlap region relative to the photosensitive waveguide is utilised to vary at least one of the phase, amplitude and period properties of at least a portion of the extended grating structure in the photosensitive waveguide.
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Abstract
A method of writing an extended grating structure in a photosensitive waveguide comprising the steps of utilizing at least two overlapping beams of light to form an interference pattern, moving the waveguide through said overlapping beams, simultaneously controlling a relative phase delay between the beams utilising a phase modulator, thereby controlling the positions of maxima within said interference pattern to move at approximately the same velocity as the photosensitive waveguide, wherein the phase modulator does not comprise a mechanical means for effecting the phase modulation, and modifying the relative phase delay between the beams during the writing of the grating structure, whereby a deliberate detuning of the velocity of the positions of maxima within said interference pattern and the velocity of the photosensitive waveguide is utilized to vary a period of the written grating structure in the photosensitive waveguide.
18 Citations
15 Claims
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1. A method of writing an extended grating structure in a photosensitive waveguide comprising:
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utilising at least two overlapping beams of light to form an interference pattern, moving the waveguide through an overlap region defined by said overlapping beams, simultaneously varying the phase of at least one of the beams relative to at least one of the other beams utilising a phase modulator, thereby variably controlling the velocity of the maxima within said interference pattern so that such velocity is different from the velocity of the photosensitive waveguide within the overlap region for the duration of the writing, excluding any periods of velocity change when the velocity of said maxima momentarily equals the velocity of the waveguide, wherein; the phase modulator comprises a non-mechanical means for effecting the phase modulation, and variation of the velocity of the maxima within the overlap region relative to the photosensitive waveguide is utilised to vary at least one of the phase, amplitude and period properties of at least a portion of the extended grating structure in the photosensitive waveguide. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification