Design and Applications of In-Cavity Pulse Shaping by Spectral Sculpturing in Mode-Locked Fibre Lasers

Abstract

We review our recent progress on the realisation of pulse shaping in passively-mode-locked fibre lasers by inclusion of an amplitude and/or phase spectral filter into the laser cavity. We numerically show that depending on the amplitude transfer function of the in-cavity filter, various regimes of advanced waveform generation can be achieved, including ones featuring parabolic-, flat-top-and triangular-profiled pulses. An application of this approach using a flat-top spectral filter is shown to achieve the direct generation of high-quality sinc-shaped optical Nyquist pulses with a widely tunable bandwidth from the laser oscillator. We also present the operation of an ultrafast fibre laser in which conventional soliton, dispersion-managed soliton (stretched-pulse) and dissipative soliton mode-locking regimes can be selectively and reliably targeted by adaptively changing the dispersion profile and bandwidth programmed on an in-cavity programmable filter. The results demonstrate the strong potential of an in-cavity spectral pulse shaper for achieving a high degree of control over the dynamics and output of mode-locked fibre lasers.

Direct control of mode-locking states of a fiber laser

“…To this end, we use a spatial light modulator (SLM) positioned in the Fourier plane of a dispersive delay line in a fiber laser cavity. While use of fixed spectral filters to influence mode locking goes back to the 1980s [18], our results rather build on recent demonstrations of SLM-based spectral filtering in picosecond fiber lasers [19,20] since we require dynamic and fully adjustable control; an excellent review is [17]. We now show that we can initiate or halt mode locking, steer the mode-locking state to more favorable but difficult-to-reach states, prevent cw breakthrough instability, automatically improve pulse shape, and generate pulses as short as 40 fs.…”

“…A complementary approach involves management of nonlinear effects directly [10], ranging from use of negative (self-defocusing) nonlinearities [10,11] to identification of nonlinearity-resilient pulse propagation schemes. Milestones include demonstration of the wave-breaking-free laser [12] in 2003, the similariton laser in 2004 [13], the all-normal dispersion laser [14] in 2008, supporting dissipative solitons [15], and the soliton-similariton laser [16] in 2010, which is the only laser to date that has two types of nonlinear waves propagating in the cavity [17]. While these developments have led to superior laser performance and unraveled new laser physics, there is currently no possibility of detailed control over the mode-locking states that the lasers support.…”

Several new directions for ultrafast fiber lasers [Invited]

“…Both in experiments and simulations, an efficient means of mining for useful phenomena will be the use of heuristic search, or machine learning, techniques. These have already yielded interesting results in the comparatively simple world of the singlemode fiber oscillators [237][238][239][240][241] and in passive or amplifier multimode fiber propagation [232,242], and should be even more useful in the voluminous parameter space of multimode fiber lasers. To some extent, these techniques could be viewed as higher-dimensional versions of the work that has already been done on polarization (i.e., using waveplates to control NPE) and spectral/dispersion (using SLM-based pulse shapers) control.…”

Rogue Wave Modes for the Coupled Nonlinear Schrödinger System with Three Components: A Computational Study

“…Detailed investigations on evolution of rogue waves in general systems of coupled nonlinear Schrödinger equations without any restriction on coefficients would be conducted in the future. Moreover, modified NLS equation or the corresponding systems can be studied [50].…”