Studies On Supercontinuum Generated By Random Fiber Laser

Random fiber laser is a novel type of fiber laser,which is different from the traditional fiber oscillator with resonator structure.It uses the random distributed feedback provided by the Rayleigh scattering in the fiber and the gain provided by the stimulated Raman scattering to achieve laser output.It has outstanding features like good temporal stability,simple structure and lasing in any wavelength,which make it has a promising application prospect in imaging and communication and many other fields.This paper has carried out some theoretical and experimental research on supercontinuum generation from random fiber laser,which including the following several aspects:In theoretical aspect,a model is built to describe the process of supercontinuum generation in random fiber laser,and the model is preliminarily simulated.Spectrum extension can be observed in output results.The existing problems of the model and methods to optimize it are analyzed.In the experimental aspect,firstly,the feasibility analysis and experimental exploration of near infrared supercontinuum generation in random fiber laser are carried out.The possibility of supercontinuum generation is verified by spectrum controlling methods.Combined with ytterbium doped fiber and device with broad reflective band,a near-infrared supercontinuum with 20 d B bandwidth of more than 500 nm is generated in a half-open cavity random fiber laser.The effects of the reflective bandwidth and the length of passive fiber on the generation of supercontinuum are discussed.The results show that the broad reflective bandwidth is beneficial for the generation of supercontinuum.The spectrum extension of supercontinuum generated by random fiber laser is studied.After theoretical calculation,it is speculated that the four-wave mixing effect is possible to extent the spectrum to the visible band.By increasing the pump power and the length of the doped fiber,the four-wave mixing process is promoted,and the supercontinuum is successfully extended to the visible light band.Finally,under the pump power of 44.7 W,the visible to near infrared supercontinuum with spectrum covering 600-1700 nm,output power of 3.45 W and the 20-d B bandwidth of more than660 nm is achieved.