Research On Narrow Line-width Er&Yb Co-doped Fiber Laser

The fiber lasers have many advantages including light weight and small size, high pumpto laser conversion efficiency, good radiation effect and tunable wave length. Particularly, thenarrow line-width lasers have particularly narrow line-width even less than10^-8nm, whichgives the laser beam excellent coherent performance. Because of this kind of characteristic, thenarrow line-width lasers have broad application prospects in the field of optical fiber sensingand communication, especially in spatial coherence detection. In this dissertation, the outputcharacteristics of narrow line-width Er³⁺-Yb³⁺co-doped fiber laser are studied, several ways ofnarrowing line-width are analyzed, and some basic experiment results are shown.This article firstly gives introduction to the basic principles and forms of fiber lasers andthe line-width compression theory. Based on the theoretical statements, the principles ofEr³⁺-Yb³⁺co-doped fiber lasers are analyzed and the model of linear cavity fiber laser isestablished. With this model, the influence of various parameters on the fiber laser is analyzedby the means of simulation. According to the simulation results, fiber laser parameters aredesigned. Then two feasible methods of saturable absorber and fiber Bragg grating F-P cavityare contrasted, and the experimental program, which combines the advantages of both, isdetermined.In the experiment, the Er³⁺-Yb³⁺co-doped double-clad fiber is taken as the gain medium,and a semiconductor laser, a wavelength division multiplexing module, several optic couplesand some optic isolators are joined together to form a narrow line-width fiber laser. In the ringcavity a couple of Bragg fiber gratings perform as F-P etalon to achieve frequency selection,and a piece of unpumped doped fiber acts as saturable absorber to do the frequencystabilization. Finally the stable output laser with line-width less than10kHz and power largerthan50mW can be experimentally demonstrated.