Fig. 2: Short NIR pulse generated with ND-HNLF.

a The intensity profile of the pulse. SHG- FROG is used to measure the pulse width of 22 fs. (Inset) The NIR spectrum of the measured pulse covering 1.3−1.7 μm and relatively flat spectral phase. b Experimental FROG and c reconstructed FROG with < 1% error.