0.6-3.2 μm supercontinuum generation in a step-index germania-core fiber using a 4.4 kW peak-power pump laser

An ultra-broadband supercontinuum was generated in a short piece of step-index germania-core fiber using a fiber laser with a peak power of 4.4 kW. The pure germania core made this fiber capable of propagating light towards the desirable mid-infrared region. The spectral broadening characteristics towards the mid-infrared region under different lengths of germania-core fiber were investigated using pump pulses of 4.4 kW and 1.1 ns at 1550 nm. The large nonlinear refractive index of germania and the small core size of germania-core fiber produced a nonlinear coefficient as high as 11.8 (W km)^-1 at 1550 nm, which was beneficial for supercontinuum generation. The pump wavelength was located in the anomalous dispersion regime and close to the zero dispersion wavelength of this germania-core fiber, 1.426 μm. Eventually, an ultra-broadband supercontinuum source with a spectrum spanning from 0.6 to 3.2 μm was obtained and had a total output power of 350 mW at an optimized germania-core fiber length of 0.8 m. This work is the first demonstration, to the best of our knowledge, of a germania-core fiber-based ultra-broadband supercontinuum source that spans from the visible region to the mid-infrared region.