Replica Symmetry Breaking Enabled by Rayleigh Scattering in a Random Fibre Laser

The light confinement in single-mode fibres allows the creation of one dimensional Random Lasers, which belong to the subclass of Random Fibre Lasers (RFLs), which have been thoroughly characterised in [1]. The evolution from spontaneous emission to lasing regime has been regarded as the photonic analogue to a spin-glass phase transition [2]: the high disorder of multiple scatterers under sufficiently high pumping may lead to strong fluctuation of the emitted spectra, where a phase transition at the lasing threshold is characterised by the change on the distribution of the intensity fluctuation overlap (IFO) parameter q. This transition is known as replica symmetry breaking (RSB) because the system can produce a different output under same initial conditions (replicas) - pumping and scatterers' positions are fixed. Uncontrolled environment perturbation in Brillouin-based RFL lead to the observation of RSB near threshold but a strong decrease of the q parameter above threshold [3].