Abstract

Parent et al.¹ were the first to report that the refractive index change induced in optical fibers is anisotropic for linearly polarized exposures, the induced birefringence lining up with the optical electric field. This effect was recently used to create a distributed feed-forward (DFF) polarization converter in Hi-Bi (high bire-fringence) fiber.¹⁵ This device was formed by launching linearly polarized light at 45° to the axes of the fiber. After exposure, the result is a gently rocking net high birefringence that couples from one eigenstate to the other within a narrow wavelength band. Here we report a distributed feed-back (DFB) polarization state converter that reflects, within a narrow wavelength range, a linearly polarized mode into the orthogonal counter-propagating mode. This filter is formed by launching two orthogonal linearly polarized counterpropagating beams into a photosensitive optical fiber; the resulting fine-period polarization fringe pattern is transferred to a corresponding rocking pattern of induced birefringence. The behavior of light in this type of structure has been examined by Yeh.

© 1992 Optical Society of America