Fabrication and characterization of step-index tellurite fibers with varying numerical aperture for near- and mid-infrared nonlinear optics

We present an overview of the fabrication process and characterization of tellurite, germanate, and germanate–tellurite step-index fibers with different index contrasts. Several compatible core/cladding glass pairs were first explored for fiber manufacturing under ambient atmosphere. The potential of the resulting waveguides for nonlinear optics is revealed by means of supercontinuum generation experiments using a near-infrared femtosecond fiber laser. Fabrication of the glass preforms was also adapted to dehydration procedures, allowing the drawing of low-OH step-index tellurite fibers. The beneficial impact of glass purification on supercontinuum generation toward the mid-infrared region is confirmed.