Abstract:
This thesis focuses on the realization and study of an all-normal dispersion passively mode-locked fibre laser operating around the 1 μm spectral region. The laser developed herein is designed to operate in an industrial environment where strong temperature fluctuations and mechanical vibrations usually occur. To do so, our laser architecture incorporates only all-polarisation maintaining components and implements a nonlinear amplifying loop mirror as a mode-locker. This element includes an extra segment of doped-fibre, which provides an additional degree of control over the pulse dynamics. The laser can emit a wide range of pulses with different spectral and temporal characteristics depending on the pump powers in the laser cavity. When the laser is operating in stable mode-locking regime it emits linearly chirped pulses with a spectral bandwidth over 20 nm that can be recompressed to 120 fs. Our laser design can also operate in the giant chirp regime by suitably adding a long segment of single mode fibre in the cavity. In this regime, the laser can sustain high-energy pulses up to 16 nJ. These results demonstrate the high versatility of our design. All our experimental results are supported by numerical simulations based on a set of nonlinear Schrodinger equations. These simulations are in very good agreement and provide great insight on the pulse formation in the laser cavity. For higher gain values the laser operates in an unstablemode-locking regime, where the laser output display the features of noise-like pulses. In this regime, a second spectral component arises from stimulated Raman scattering. To spectrally characterise this regime we implement a dispersive Fourier transform technique that allows us to measure the real-time pulse-to-pulse spectra, revealing new dissipative phenomena. Additionally, our measurements reveal strong shot-to-shot spectral fluctuations. A statistical study of the energy fluctuations shows that the second spectral component fulfills the rogue wave criteria. Finally, by adjusting the pump power to lie in between the stable and unstable regimes we observe another transient regime, called soliton explosions, where a dissipative soliton circulating in the laser cavity collapses abruptly but within few roundtrips returns to its previous pseudo-stable state. Numerical simulations are in good agreement with the real-time spectral measurements and reveal that these explosions exhibit abrupt temporal shifts in the pulse train. A second set of real-time measurements performed in the time-domain confirm these numerical predictions, as we observe a 40 ps temporal jump every time an explosion occurs.