Structured-Core GeO $_{2}$ -Doped Photonic-Crystal Fibers for Parametric and Supercontinuum Generation

We demonstrate efficient broadband four-wave-mixing (FWM) generation at the particular frequency detuning of ~150 THz from a 1064-nm sub-nanosecond laser pump in innovative structured-core germanium-oxide (GeO₂)-doped photonic crystal fibers (PCFs). Remarkably, the latter PCF has a small-diameter highly concentrated germanium rod in the core center that enables fine tuning of the FWM wavelengths. The generated anti-Stokes radiation at ~700 nm is subsequently used as secondary pump for generating a bright visible supercontinuum in the fundamental mode from 370 nm to beyond 1750 nm, when splicing the GeO₂-doped PCF to a pure-silica PCF, whose zero-dispersion wavelength is set in-between the pump and anti-Stokes wavelengths, consistently with the standard dual-wavelength pumping scheme.