Photosensitive polymer optical fibers and gratings.

摘要

The objective of this thesis is to develop ultraviolet (UV) photosensitive single-mode polymer optical fibers (POFs) which exhibit a photo-induced change in refractive index (commonly referred to as photosensitivity) and can be applied to fabricate fiber optic gratings with a low energy and small dosage of UV irradiation. It studied the two-step fabrication process (preform making and heat drawing) of single-mode optical fibers comprising PMMA and copolymers as the cladding and core, respectively, and obtained a set of workable processing conditions and material parameters. The preforms and fibers were successfully made. Lorenz-Lorenz Equation was efficiently applied in the design of core copolymer composition in terms of its refractive index with a satisfactory result. Three photosensitive systems were investigated for the core of the fiber; the most promising one was identified: MMA copolymer doped with trans-4-stilbenemethanol (TS). The mechanism of refractive index modulation in this system and PMMA were studied in details by a number of analytical methods. The grating writing process of the TS-doped PMMA optical fibers and films by masked UV laser exposure from a pulse laser system at 325 nm and UV lamp was investigated, from which, the photosensitivity and stability of the material system were confirmed.