Random fibre lasers constitute 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. It is known than the nature of Rayleigh scattering is elastic. However, as the laser generates a smooth spectra, the feedback mechanism in random fibre lasers has been assumed to be incoherent. In the present talk we will use a real-time spectral measurement technique based on a scanning Fabry-Perot interferometer to reveal fast dynamics of the random fibre laser spectrum. We observe long-living narrowband components in the generation spectrum, and make a statistical analysis of a large number single-scan spectra to reveal a preferential interspacing between narrow-components. Further, we will discuss the results of advanced real-time spectral measurements via heterodyne-based measurements. We will show that ultra-narrow spectral components (with spectral width down to 1 kHz) are generated. 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.
Dmitry V. Churkin, Srikanth Sugavanam, and Mariia Sorokina, "Coherent modes in a random fibre laser (Conference Presentation)," Proc. SPIE 10517, Real-time Measurements, Rogue Phenomena, and Single-Shot Applications III, 105170O (Presented at SPIE LASE: January 30, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2289603.5751425877001.
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