Mode-field converters and long-period gratings fabricated by thermo-diffusion in nitrogen-doped silica-core fibers

摘要

Novel nitrogen-doped silica-core pure-silica-cladding fibers provide exceptional possibilities to achieve abrupt variations of the refractive-index profile by thermo-diffusion of nitrogen. A high diffusion coefficient of nitrogen in silica makes it possible to create deep changes in refractive index by means of short-time heat action on a fiber section with a length comparable to the fiber diameter. Thus, N-doped silica fibers are most appropriate for various fiber-optic devices produced by thermo-diffusion.