Recent developments in optical fibre technology have allowed significant advances in the nonlinear generation and tailoring of broadband spectra. Much work in this direction has focused on the optimisation of the properties of the optical fibres used for the nonlinear pulse propagation. In this work, we combine the nonlinear element (a highly nonlinear fibre - HNLF) with a programmable phase and amplitude filter, which we use as a pulse shaper. This architecture allows power-efficient and flexible sculpturing of the output spectrum, which is no longer tied directly to the characteristics of the pulse source used at the input. The pulse shaping function is obtained by application of the inverse split-step Fourier method (ISSFM) , which uses the desired output spectrum and the HNLF characteristics as its input parameters . As an example of the application of this technique, we study the generation of broadband flat (third-order super-Gaussian) spectra starting from a 10GHz mode-locked pulsed laser (MLL). Here we present our design procedure and a first experimental validation of the technique.
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