Research On Novel Multiwavelength Random Fiber Lasers

Sergei K.Turitsyn et al firstly demonstrated the random lasers which used the fiber as a random medium in 2010 and proposed the concept of random distributed feedback fiber laser(RDF-FL).The random distributed feedback of this novel type of random laser is provided by the backward Rayleigh scattering(RS),and the gain is usually provided by the stimulated Raman scattering(SRS)or stimulated Brillouin scattering(SBS).RDF-FLs have attracted much interests for its efficiency,simplicity and tunability since their first demonstration.So far the RDF-FLs have great developments in many aspects,such as high power,multiwavelength,narrow bandwidth,tunability,different spectral location and sensing systems.Meanwhile,RDF-FLs are also a useful platform to study random theory for their insightful physical mechanism.In this thesis,a novel type of multiwavelength random fiber laser based on SBS is proposed,which realizes the separated output of odd and even Stokes waves.The interval between two adjacent lasing wavelengths is 0.174 nm.By adjusting the pump of the proposed structure,the output performance as well as the tunability can be improved.The power balance equation for random fiber lasers with linearly polarized output is also optimized.The thesis is divided into the following parts:(1)The concept of random lasers and the research background of the RDF-FLs are introduced.Then the research situation of the RDF-FLs is also summarized.(2)Different scattering theories(RS,SRS,SBS)which RDF-FLs depend on are analyzed and the basic theory of fiber lasers is introduced.Finally,the output power of the RDF-FLs is simulated by using the power balance equation(3)The power balance equation for random fiber lasers with linearly polarized output is optimized.The output power of the linearly polarized random fiber lasers is simulated and analyzed based on the optimized power balance equation.(4)A novel type of multiwavelength random fiber laser based on SBS is proposed and experimentally demonstrated.The proposal realizes the separated output of odd and even Stokes waves.(5)The proposed multiwavelength random fiber laser is further improved.The output of the multiwavelength random fiber laser is optimized and tunability is realized.A simple theoretical model is established to explain the output spectra.