Real-Time Intensity Domain Characterization of Fibre Lasers Using Spatio-Temporal Dynamics

Abstract

Fibre lasers are light sources that are synonymous with stability. They can give rise to highly coherent continuous-wave radiation, or a stable train of mode locked pulses with well-defined characteristics. However, they can also exhibit an exceedingly diverse range of nonlinear operational regimes spanning a multi-dimensional parameter space. The complex nature of the dynamics poses significant challenges in the theoretical and experimental studies of such systems. Here, we demonstrate how the real-time experimental methodology of spatio-temporal dynamics can be used to unambiguously identify and discern between such highly complex lasing regimes. This two-dimensional representation of laser intensity allows the identification and tracking of individual features embedded in the radiation as they make round-trip circulations inside the cavity. The salient features of this methodology are highlighted by its application to the case of Raman fibre lasers and a partially mode locked ring fibre laser operating in the normal dispersion regime.

Rotation Active Sensors Based on Ultrafast Fibre Lasers

“…Figure 6 demonstrates the principle of spatiotemporal dynamics of periodic pulses in bidirectional mode-locked fibre laser [ 29 ]. The temporal resolution is limited by the oscilloscope-detector combination according to the following expression [ 163 ]: where and are the time-domain impulse response of photodetector and oscilloscope, correspondingly, which relate to the rise time as = 0.915 . The temporal resolution limits of the above method can be surpassed using nonlinear approaches.…”

Analysis of laser radiation using the Nonlinear Fourier transform

“…NFT-based signal processing requires full-field information, i.e., the knowledge of both the power (or intensity) and the phase. Note that while methods like spatio-temporal dynamics 29,30 and DFT 22 are often used for studying the dynamic behaviour of laser field, they do not capture phase information. The bottleneck lies in the intensity-based response of the square law detectors which average out all fast phase variation.…”

“…For instance, the dispersive Fourier transform (DFT) method for real-time spectral measurement 22 has been successfully used in fibre lasers for studying soliton explosions 26 , bound solitons 24,27 , and the complexities of mode-locking onset behaviour 28 . Further, measurements of spatio-temporal dynamics of intensity in fibre lasers 29,30 have revealed the existence of distinct spatio-temporal regimes of operation in ultralong fibre lasers 29,31 , proliferation of dark solitons in stretched pulse fibre lasers 29 , generation of spatio-temporal extreme events 32 and also interaction and collisions of solitons in multisoliton regimes 33 . The methodology of space-time duality 34 has been successfully exploited to realise time lenses for the study of integrable turbulence 35 , the direct observation of rogue waves 36 and in uncovering hidden universalities in soliton dynamics 37 .…”

Mapping the dynamical regimes of a SESAM mode-locked VECSEL with a long cavity using time series analysis

“…5 ps is the sampling period. Figure 4 shows a space-time representation of the single pulse within each round-trip, for 100 round-trips [24,25]. Each pixel in the figure is a representation of the acquired discrete signal amplitude for one sampling period of the oscilloscope and is scaled to the color according to the color-scale located on the right hand side of the figure.…”