Ultra-low-noise supercontinuum generation with a flat near-zero normal dispersion fiber

A pure silica photonic crystal fiber with a group velocity dispersion (beta(2)) of 4 ps(2)/km at 1.55 mu m and less than 7 ps(2)/km from 1.32 mu m to the zero dispersion wavelength (ZDW) 1.80 mu m was designed and fabricated. The dispersion of the fiber was measured experimentally and found to agree with the fiber design, which also provides low loss below 1.83 mu m due to eight outer rings with increased hole diameters. The fiber was pumped with a 1.55 mu m, 125 fs laser and, at the maximum in-coupled peak power (P-0) of 9 kW, a 1.34-1.82 mu m low-noise spectrum with a relative intensity noise below 2.2% was measured. The numerical modeling agreed very well with the experiments and showed that P-0 could be increased to 26 kW before noise from solitons above the ZDW started to influence the spectrum by pushing high-noise dispersive waves through the spectrum. (C) 2019 Optical Society of America