Controlling the width of a femtosecond continuum generated in a small-diameter fibre

The control of the width of a continuum generated in a tapered germanium-doped silica fibre with the waist diameter of ~3 μm is experimentally demonstrated for the first time. The width of the continuum was controlled by varying the wavelength of chirped femtosecond pump pulses near the zero-point of the group velocity dispersion of the fibre. The width of the continuum at the – 20-dB level was varied from 98 to 790 nm by tuning the central wavelength of 80-fs, 0.6-nJ input pulses from 789 to 847 nm.