Ultra-high spectral purity laser derived from weak external distributed perturbation

Ultra-high spectral purity lasers are of considerable research interests in numerous fields such as coherent optical communication,microwave photonics,distributed optical fiber sensing,gravitational wave detection,optical clock,and so on.Herein,to deeply purify laser spectrum with compact size under normal condition,we propose a novel and practical idea to effectively suppress the spontaneous radiation of the laser cavity through weak external distributed perturbation.Subsequently,a laser configuration consisting of a main lasing cavity and an external distributed feedback cavity is proposed.The feedback signal with continuous spatio-temporal phase transition controlled by a distributed feedback structure is injected into the main cavity,which can deeply suppress the coupling rate from the spontaneous radiation to the stimulated emission and extremely purify the laser spectrum.Eventually,an ultra-narrow linewidth on-chip laser system with a side mode suppression ratio greater than 80 dB,an output linewidth of 10 Hz,and a relative intensity noise less than-150 dB/Hz is successfully obtained under normal conditions.The proposed concept in this work provides a new perspective for extreme regulation of laser parameters by using weak external distributed perturbation,which can be valid for various gain-type lasers with wide wavelength bands.

Spectrum evolution of Rayleigh backscattering in one‐dimensional waveguide

Despite the tremendous awareness of Rayleigh scattering characteristics and its considerable research interest for numerous fields,no report has been documented on the dynamic characteristics of spectrum evolution(SpE)and physical law for Rayleigh scattering from a micro perspective.Herein,the dynamic characteristics of the SpE of Rayleigh scattering in a one-dimensional waveguide(ODW)is investigated based on the quantum theory and a SpE-model of Rayleigh backscattering(RBS)source is established.By means of simulation,the evolution law which represents the dynamic process of the spectrum linewidth at a state of continuous scattering is revealed,which is consistent with our previous experimental observation.Moreover,an approximate theoretical prediction of the existing relationship between the spectrum linewidth of RBS source and the transmission length in ODW is proposed,which theoretically provides the feasibility of constructing functional devices suitable to ascertain laser linewidth compression.The designed experimental scheme can be implemented provided the assumptions are fulfilled.In addition,a theoretical model of the micro-cavity structure to realize the deep compression of laser linewidth is proposed.