Abstract
Random distributed feedback fibre lasers belong to the class of random lasers, where the feedback is provided by amplified Rayleigh scattering on sub-micron refractive index inhomogenities randomly distributed over the fibre length. Despite the elastic nature of Rayleigh scattering, the feedback mechanism has been insofar deemed incoherent, which corresponds to the commonly observed smooth generation spectra. Here, using a real-time spectral measurement technique based on a scanning Fabry-Pérot interferometer, we observe long-living narrowband components in the random fibre laser’s spectrum. Statistical analysis of the ∼104 single-scan spectra reveals a preferential interspacing for the components and their anticorrelation in intensities. Furthermore, using mutual information analysis, we confirm the existence of nonlinear correlations between different parts of the random fibre laser spectra. The existence of such narrowband spectral components, together with their observed correlations, establishes a long-missing parallel between the fields of random fibre lasers and conventional random lasers.
Highlights
Random distributed feedback fibre lasers belong to the class of random lasers, where the feedback is provided by amplified Rayleigh scattering on sub-micron refractive index inhomogenities randomly distributed over the fibre length
Piezo-enabled Fabry-Perot interferometer (FPI) are capable of operating at frequencies B102 Hz, corresponding to a spectral acquisition rate that is at least two orders of magnitude higher than conventional Czerny–Turner-based optical spectrum analyser (OSA) configurations
The real-time spectral measurement technique based on the FPI has allowed to observe individual narrowband spectral components in the radiation of the random fibre laser
Summary
Random distributed feedback fibre lasers belong to the class of random lasers, where the feedback is provided by amplified Rayleigh scattering on sub-micron refractive index inhomogenities randomly distributed over the fibre length. Multiple scattering events increase the mean free path of the photons within the gain media, leading to an avalanche generation of stimulated photons[1] (the so-called ‘photonic bomb’ effect) This principle has been very successfully employed in realizing lasing in different configurations of both strongly scattering[2,3,4] and weakly scattering systems[5,6]. It is known that in conventional random lasers based on strongly scattering systems, multiple scattering events can result in generation of closed loops within the medium that can sustain a coherent feedback[9] These can result in a generation spectrum consisting of well-defined spectral peaks with high Q-factors, which follow the Schawlow-Townes linewidth relation[13]. A numerical model based on coupled nonlinear Schrodinger equations with an assumption of incoherent feedback[19] reproduces the experimentally observed smooth spectrum as well
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
