Fabrication of multi-core structures in optical fibers using plasma self-channeling excited by a femtosecond laser

Fabrication of multi-core structures with bulk refractive index modification in optical fibers was first demonstrated by the scanning of plasma self-channeling using a femtosecond (110 fs) laser (/spl lambda//sub p/ = 790 nm). Plasma self-channeling is an intensity-dependent nonlinear phenomenon, in which a laser beam is tightly focused and guided for the distance longer than the Rayleigh range. It is attributed to self-focusing due to the intensity-dependent refractive index change and to self-defocusing by the laser-induced plasma. The fabrication method of the multi-core structure in optical fibers can be a useful tool for a variety of applications such as photonic crystal fibers and micro-waveguides in the fields of optical communication and optical sensors.