Real-time measurements of dissipative solitons in a mode-locked fiber laser

Dissipative solitons are remarkable localized states of a physical system that arise from the dynamical balance between nonlinearity, dispersion and environmental energy exchange. They are the most universal form of soliton that can exist in nature, and are seen in far-from-equilibrium systems in many fields including chemistry, biology, and physics. There has been particular interest in studying their properties in mode-locked lasers producing ultrashort light pulses, but experiments have been limited by the lack of convenient measurement techniques able to track the soliton evolution in real-time. Here, we use dispersive Fourier transform and time lens measurements to simultaneously measure real-time spectral and temporal evolution of dissipative solitons in a fiber laser as the turn-on dynamics pass through a transient unstable regime with complex break-up and collision dynamics before stabilizing to a regular mode-locked pulse train. Our measurements enable reconstruction of the soliton amplitude and phase and calculation of the corresponding complex-valued eigenvalue spectrum to provide further physical insight. These findings are significant in showing how real-time measurements can provide new perspectives into the ultrafast transient dynamics of complex systems.Comment: See also M. Narhi, P. Ryczkowski, C. Billet, G. Genty, J. M. Dudley, Ultrafast Simultaneous Real Time Spectral and Temporal Measurements of Fibre Laser Modelocking Dynamics, 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference, paper EE-3.5 (2017

Analysis of laser radiation using the Nonlinear Fourier transform

Modern high-power lasers exhibit a rich diversity of nonlinear dynamics, often featuring nontrivial co-existence of linear dispersive waves and coherent structures. While the classical Fourier method adequately describes extended dispersive waves, the analysis of time-localised and/or non-stationary signals call for more nuanced approaches. Yet, mathematical methods that can be used for simultaneous characterisation of localized and extended fields are not yet well developed. Here, we demonstrate how the Nonlinear Fourier transform (NFT) based on the Zakharov-Shabat spectral problem can be applied as a signal processing tool for representation and analysis of coherent structures embedded into dispersive radiation. We use full-field, real-time experimental measurements of mode-locked pulses to compute the nonlinear pulse spectra. For the classification of lasing regimes, we present the concept of eigenvalue probability distributions. We present two field normalisation approaches, and show the NFT can yield an effective model of the laser radiation under appropriate signal normalisation conditions

All-depth dispersion cancellation in spectral domain optical coherence tomography using numerical intensity correlations

In ultra-high resolution (UHR-) optical coherence tomography (OCT) group velocity dispersion (GVD) must be corrected for in order to approach the theoretical resolution limit. One approach promises not only compensation, but complete annihilation of even order dispersion effects, and that at all sample depths. This approach has hitherto been demonstrated with an experimentally demanding ‘balanced detection’ configuration based on using two detectors. We demonstrate intensity correlation (IC) OCT using a conventional spectral domain (SD) UHR-OCT system with a single detector. IC-SD-OCT configurations exhibit cross term ghost images and a reduced axial range, half of that of conventional SD-OCT. We demonstrate that both shortcomings can be removed by applying a generic artefact reduction algorithm and using analytic interferograms. We show the superiority of IC-SD-OCT compared to conventional SD-OCT by showing how IC-SD-OCT is able to image spatial structures behind a strongly dispersive silicon wafer. Finally, we question the resolution enhancement of 2–? that IC-SD-OCT is often believed to have compared to SD-OCT. We show that this is simply the effect of squaring the reflectivity profile as a natural result of processing the product of two intensity spectra instead of a single spectrum

The study on alkali-promoted Co-Mo/Al2\text{}_{2}O3\text{}_{3} catalysts for water-gas shift process

The following contribution presents the results of studies on the effects of alkali metals on the physicochemical properties and the effectiveness of a Co-Mo/Al$\text{}_{2}$O$\text{}_{3}$ catalyst for the water gas shift reaction. It has been shown that the addition of alkali metals modifies the properties of Co-Mo catalysts, resulting in a significant increase in activity of catalysts in water gas shift reaction. The greatest effect was observed in the case of sodium-promoted reaction

Investigations on hydrogenation of selected organic sulfur compounds on the Ni-Mo/Al2\text{}_{2}O3\text{}_{3}catalyst in terms of natural gas desulfurization

Technological problems of natural gas desulfurization in syngases manufacturing plants have been discussed and the results of investigations on the activity of the model Ni-Mo/Al$\text{}_{2}$O$\text{}_{3}$ catalyst in hydrogenation of selected sulfur compounds have been presented. The HDS reaction rate is dependent on a compound structure. The hydrogenation rate on the Ni-Mo/Al$\text{}_{2}$O$\text{}_{3}$ catalyst for the given sulfur compound increases in the order: CS$\text{}_{2}$(CH$\text{}_{3}$)$\text{}_{2}$S>C$\text{}_{4}$H$\text{}_{10}$S>C$\text{}_{2}$H$\text{}_{6}$S$\text{}_{2}$C$\text{}_{4}$H$\text{}_{4}$S

Temporal ghost imaging

No abstract available