ULTRAFIL · Ultra-short pulse fibre laser technology

Ultra-short pulse fibre laser technology

The project ULRAFIL was focused on the development and application of dispersion-managed dissipative soliton fibre lasers with high energy. The overall research aim of the project was to develop new concepts, techniques and approaches to the new design of fibre lasers based on a transfer of the methods of nonlinear science into the field of optical engineering. Mode-locking is a technique by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds or femtoseconds. In a mode-locked fibre laser, the interplay among the effects of gain/loss, dispersion (the dependence of wave velocity on frequency) and nonlinearity can be used to shape the pulses and manipulate the light dynamics and, hence, lead to different regimes of mode locking. Techniques for generating specialized waveforms have become increasingly important in many scientific areas, including, amongst others, ultrahigh-speed optical communications, and optical signal processing. Versatile ultrafast laser sources, which can selectively emit different types of pulses, are highly desirable in this context. The key to access different pulse regimes in passively mode-locked fibre laser is in-cavity dispersion management. Commonly employed methods to achieve in-cavity dispersion tuning include grating pairs, or simply physically changing the length of the fibre in the cavity. All these techniques however, require manual tuning of some physical parameters of the cavity. Spectral pulse shaping employed in a mode-locked fibre laser has emerged as a method to achieve a potentially high degree of control over the dynamics and the output of the laser purely through software control. In the project ULTRAFIL we demonstrated that different pulse regimes including soliton, dispersion-managed soliton, and dissipative soliton mode-locking regimes can be switched and reliably targeted by programming the dispersion and bandwidth on an in-cavity programmable filter. The generation and in-cavity evolution of the different regimes are further confirmed by a numerical analysis. Each of these mode-locking regimes obviously takes on major practical importance. To our knowledge, this is the first time that these distinctly different pulse solutions are obtained in a single laser system without applying any physical changes in 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 dispersion-managed fibre laser, which involves manual optimization 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. Please see the attached document titled final publishable summary report

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