Abstract
We present the operation of an ultrafast passively mode-locked fibre laser, in which flexible control of the pulse formation mechanism is readily realised by an in-cavity programmable filter the dispersion and bandwidth of which can be software configured. We show that conventional soliton, dispersion-managed (DM) soliton (stretched-pulse) and dissipative soliton mode-locking regimes can be reliably targeted by changing the filter’s dispersion and bandwidth only, while no changes are made to the physical layout of the laser cavity. Numerical simulations are presented which confirm the different nonlinear pulse evolutions inside the laser cavity. The proposed technique holds great potential for achieving a high degree of control over the dynamics and output of ultrafast fibre lasers, in contrast to the traditional method to control the pulse formation mechanism in a DM fibre laser, which involves manual optimisation of the relative length of fibres with opposite-sign dispersion in the cavity. Our versatile ultrafast fibre laser will be attractive for applications requiring different pulse profiles such as in optical signal processing and optical communications.
Highlights
Generation at net anomalous or normal dispersion can be realised in a DM fibre laser via appropriate in-cavity dispersion management[21,22,23,24]
A programmable liquid-crystal-onsilicon (LCoS) phase and amplitude filter[35] was used to realise different regimes of pulse generation in the cavity. (Further details can be found in the Methods.) Under mode-locking conditions, the laser operated at a repetition period of 89 ns (Fig. 2), which remained constant throughout the experiments described below
At the level of fundamental research, mode-locked lasers constitute an ideal platform for the investigation of original and complex nonlinear dynamics of ultrashort pulses, while at the applied research level, pulses with different and optimised features – e.g., in terms of pulse duration, temporal and/or spectral shape, width, energy, repetition rate and emission bandwidth – are sought with the general constraint of developing efficient cavity architectures
Summary
Generation at net anomalous or normal dispersion can be realised in a DM fibre laser via appropriate in-cavity dispersion management[21,22,23,24]. Programmable phase and amplitude filters[35] are already commercially available and extensively used in telecommunications applications[36] The use of such filters, when placed inside a laser cavity, has the potential to allow the operation of lasers that exhibit pulse characteristics that can be controlled purely through software control. 32, it was numerically shown that a passively mode-locked fibre laser can operate in different pulse-shaping regimes, including bright and dark parabolic, flat-top, triangular, and saw-tooth waveform generations, depending on the amplitude profile of an in-cavity spectral filter. An application of this technique using a flat-top spectral filter was numerically demonstrated to achieve the direct generation of high-quality sinc-shaped optical Nyquist pulses with widely tuneable bandwidth from a passively mode-locked fibre laser[33]. The programmable-filter-based technique presented in this paper greatly relaxes the need for employing opposite-sign dispersion fibres and fibre length optimisation in order to achieve the desired pulse-shaping regime in ultrafast fibre lasers
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