Supercontinuum Generation Covering the Entire 0.4–5 Μm Transmission Window in a Tapered Ultra-High Numerical Aperture All-Solid Fluorotellurite Fiber

Enormous efforts have been made to realize supercontinuum (SC) generation covering the entire transmission window of fiber materials for their wide applications in many fields. Here we demonstrate ultra-broadband SC generation from 400 to 5140nm in a tapered ultra-high numerical aperture (NA) all-solid fluorotellurite liber pumped by a 1560nm mode-locked fiber laser. The fluorotellurite fibers arc fabricated using a rod-in-tube method. The core and cladding materials are TeO2-BaF2-Y2O3- and TeO2-modified fluoroaluminate glasses, respectively, which have large refractive index contrast and similar thermal expansion coefflcienls and softening temperatures. The NA at 3200nm of the fluorotellurite fiber is about 1.11. Furthermore, tapered fluorotellurite fibers arc prepared using an elongation machine. SC generation covering the entire 0.4-5 mu m transmission window is achieved in a tapered fluorotellurite fiber for a pumping peak power of similar to 10.5 kW through synergetic control of dispersion, nonlinearity, confinement loss and other unexpecled effects (e.g. the attachment of dust or water to the surface of the fiber core) of the fiber. Our results show that, tapered ultrahigh NA all-solid soft glass fibers have a potential for generating SC light covering their entire transmission window.