Abstract

In this paper, the general form of the dielectric tensor induced in glass by interferometric exposure to light of arbitrary polarization is derived using a Hamiltonian approach for one and two-photon absorption. Considerable research effort has been devoted to the fabrication of polarization convertors in optical fibers using anisotropic photosensitivity [1-4], partly because of their potential applications in distributed sensing. The analysis of these devices has been conducted by writing down the dielectric tensor using phenomenological arguments. A rigorous development of the complete dielectric tensor starting from the microscopic origins has been lacking in the literature. We discuss the physical origins of anisotropic photosensitivity and develop a model based on preferential ionization to arrive at the form of the dielectric tensor under general exposure conditions. Both single and two-photon processes can be treated, making the formulation valid for both UV side-writing and in-core filter writing with blue/green guided modes. In addition to elucidating the dielectric tensor of polarization convertors, the treatment predicts that a special new type of light tap will form during single-photon side-writing with waves of linear but orthogonal polarization states.

© 1993 Optical Society of America