Srikanth Sugavanam received his B.Tech in Optics and Optoelectronics from the University of Calcutta, and his MS in Optics under the framework of the Erasmus Mundus OpSciTech Programme from the Warsaw University of Technology and Friedrich Schiller University, Jena. He did his PhD in electrical engineering from Aston University, Birmingham, UK, specialising in real-time measurements for fibre lasers. Since graduation, he has been working as a Research Fellow with Aston Institute of Photonic Technologies (AIPT) on different areas including conventional and ultralong fibre lasers, random fibre lasers, fibre optic sensors and ultrafast bidirectional fibre laser-based gyroscopes. Apart from actively pursuing research, Srikanth is fulfilling the role of Programme Manager for the Marie S.-Curie Postdoctoral Fellowship programme, MULTIPLY, co-ordinated by Aston University.
NFT FOR LASER CHARACTERIZATION
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 approaches 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.