Periodic Structures on Biconically Tapered Optical Fibers Using Ion Beam Milling and Boron Implantation

In this paper, the authors introduce local periodic perturbations of the cladding refractive index in the reduced diameter (waist) region of biconically tapered single-mode optical fibers by two methods. The first was focused ion beam milling to give short grooves perpendicular to the fiber axis, and the second was boron implantation, giving a phase grating in the cladding. Both structures exhibit a wavelength-dependent throughput and are highly sensitive to the environment in the waist region, which makes them potentially applicable in optical communication networks as well as in sensors. A simple corrugated slab-waveguide model is able to account for the measured spectral transmission of these structures.