| 摘要 |
<p>Instead of a single beam (10), two coherent beams (10' and 10") of light are used to illuminate a phase grating in spatially separated zones for writing a Bragg reflection grating in an underlying optical (fibre) waveguide (12). Close proximity between phase grating and waveguide is not required. This facilitates the use of masking so that only two different diffracted orders (10'c and 10"a) contribute to the fringe pattern that generates the Bragg grating, thereby improving fringe contrast and reducing the deleterious spectral effects upon the reflectivity of the Bragg reflector occasioned by the presence of stitch errors in the phase grating. <IMAGE></p> |
