## 4 Conclusions  
We have provided an overview of our recent results and advances in the realisation of pulse shaping in passively-mode-locked fibre lasers by inclusion of an amplitude and phase spectral filter into the laser cavity. We have presented a fibre laser design in which pulse shaping occurs through filtering of a spectrally nonlinearly-broadened pulse in the cavity. This strategy of pulse shaping has been illustrated through the numerical demonstration of the laser operation in different pulse-generation regimes, including bright and dark parabolic, flat-top, triangular and saw-tooth waveform generations, depending on the amplitude profile of the in-cavity spectral filter. These results are of particular relevance with the high interest in the generation of specialised pulse waveforms for applications in optical signal processing and manipulation. Using a spectral filter based on a programmable optical processor, one would be able to easily reconfigure the operation of the laser with a computer interface. The pulse-shaping approach presented here is attractive because it provides a high degree of control over the output pulse shape of the laser to adjust its operation to different experimental requirements. As an  
Figure 8: Simulated evolution of the rms temporal (red) and spectral (blue) widths of the pulse along the cavity for the (**a**) soliton, (**b**) DM soliton and (**c**) DS regimes. Adapted from [37]. application of this method, we have numerically shown the possibility of directly generating sinc-shaped Nyquist pulses of high quality from a laser incorporating a simple flat-top spectral filter in the cavity. We have also shown that the use of a filter's profile with a corrective convex top can compensate for the concavity of the nonlinearly-broadened pulse spectrum in the fibre, thereby relaxing the need for large nonlinear phase accumulation. The filtering process being used enables the tunability of the spectral bandwidth of the output sinc pulses over a wide range, up to a few terahertz. The high flexibility of the bandwidth can be of particular interest for photonic-assisted technologies, such as photonic analogue-to-digital conversion or optical sampling. Finally, we have reported on a recently-developed versatile ultrafast passively-mode-locked EDF laser in which the pulse formation mechanism can be flexibly controlled by an in-cavity programmable filter. We have demonstrated that conventional solitons, DM solitons and DSs can be selected and reliably targeted in a single laser by adaptively changing the dispersion and bandwidth programmed on the in-cavity filter. We have confirmed the different regimes of pulse generation experimentally and by numerical simulations. The transitions among the different pulse-shaping regimes are easily reconfigurable and inherently interesting in the field of ultrafast optics owing to their vastly different characteristics. This multifunction ultrashort-pulse fibre laser source has great potential for several applications, such as optical communications and signal processing, and can also be readily implemented at different wavelength regions, such as at the two-micron region, where suitable dispersion-compensating fibres are still under development. From a fundamental standpoint, our work confirms the great potential of the concept of an in-cavity spectral pulse shaper for manipulating and controlling the dynamics of mode-locked fibre lasers and, thus, enabling different mode-locking regimes. We acknowledge important contributions of our colleagues, [PERSON] and [PERSON], to the original papers discussed in this review. We would also like to acknowledge the financial support of the Leverhulme Trust (Grant RPG-278) and the European Commission Marie Curie International Incoming Fellowship scheme (Grant No. 628198). [PERSON] had the initial idea for and led the work presented in this paper. She contributed to the design of the study, the production of the numerical results, the analysis and interpretation of the results and the preparation of the manuscript.