Flat super-continuum generation using carbon-nanotube-based modelocked laser and normal dispersion photonic crystal fibre

A flat super-continuum (SC) generated by a 1.5 μm passively fibre modelocked laser incorporating a single-walled carbon-nanotube-based saturable absorber and a normal dispersion highly nonlinear photonic crystal fibre (PCF) is demonstrated. A compressed 620 fs pulse train from the modelocked laser is obtained and launched into the PCF. Since the pulses propagate in the normal dispersion regime of the PCF, linear frequency chirp is induced by self-phase modulation which leads to a flat SC. An SC covering 200 nm with less than 7 dB power fluctuation is achieved. The experimental results are consistent with the theoretical analysis based on the nonlinear Schrödinger equation.