Fabrication and characterization of multimaterial chalcogenide glass fiber tapers with high numerical apertures

This paper reports on the fabrication and characterization of multimaterial chalcogenide fiber tapers that have high numerical apertures (NAs). We first fabricated multimaterial As2Se3-As2S3 chalcogenide fiber preforms via a modified one-step coextrusion process. The preforms were drawn into multi- and single-mode fibers with high NAs (∼1.45), whose core/cladding diameters were 103/207 and 11/246 μm, respectively. The outer diameter of the fiber was tapered from a few hundred microns to approximately two microns through a self-developed automatic tapering process. Simulation results showed that the zero-dispersion wavelengths (ZDWs) of the tapers were shorter than 2 μm, indicating that the tapers can be conveniently pumped by commercial short wavelength infrared lasers. We also experimentally demonstrated the supercontinuum generation (SCG) in a 15-cm-long multimaterial As₂Se₃-As₂S₃ chalcogenide taper with 1.9 μm core diameter and the ZDW was shifted to 3.3 μm. When pumping the taper with 100 fs short pulses at 3.4 μm, a 20 dB spectral of the generated supercontinuum spans from 1.5 μm to longer than 4.8 μm.