Key Technology Of Ytterbium Doped Fiber Laser And Superfluorescent Fiber Source

Compared with traditional solid-state lasers, fiber laser has better beam quality, higher conversion efficiency and more compact structure. Besides, it is convenient to make its thermal control. So fiber laser is widely used in optical communications, optical sensing, industrial processing, medical science, aerospace industry and laser weapons. Furthermore, as a broadband light source, superfluorescent fiber source(SFS), compared with superluminescent diode (SLD), has better spatial coherence and low temporal coherence for its good temperature stability, high output power and wide width of spectrum. It can be used in fiber optic gyroscope, optical coherence tomography, source of Raman laser and some signal processing system.In this thesis, the investigation of Yb-doped double-clad fiber lasers and Yb-doped SFS ara focused on from both theoretical and experimental aspects. A 1018nm Yb-doped double-clad fiber laser obtained in the experiment is as a pump source to achieve the tandem core-pumped SFS for the first time. It provides a new way of thinking about SFS. The main achievements are described in the following.Firstly, rate equation is set up for modeling the characteristics of Yb-doped fiber laser. The corresponding program is written by Matlab. The effect of the wavelength of pump light, the way of pump, the length of fiber and reflectivity of resonator mirror on the output power of laser are discussed in detail.Secondly, combined with Yb-doped SFS’s operating principle and rate equation, the threshold condition of parasitic oscillation is deduced. Then RP Fiber Power software is used to simulate the behavior of Yb-doped SFS. The effect of the way of pump and the length of fiber and fiber end reflectivity on the output power and spectrum of SFS are discussed in detail.Thirdly, with a 976nm LD as the pump source, the experimental system is set up to produce the output lasing at the wavelength of 1018nm with Yb-doped double-clad fiber laser. When the pump power is 22.6W, the maximum continuous output power is 13.9W with the central wavelength of 1018.08nm and 3dB bandwidth of 0.30nm. The implement of 1018nm fiber laser offers the possibility to achieve the tandem pumped SFS.Finally, with the homemade 1018nm fiber laser as the pump source, a one way SFS with core-pumped is proposed and demonstrated experimentally. To the best of our knowledge, it is the first time to realize the Yb-doped SFS based on tandem pump. The effects of different pump power and fiber length on output power and spectrum of ASE are investigated in detail. In addition, as comparison, a SFS with 976nm LD as a pump source is set up and investigated. The contrast experiment shows that the slope efficiency of forward ASE with tandem pump is larger than the slope efficiency of forward ASE and backward ASE with cladding pump. It proves that SFS with tandem pump does have a higher quantum efficiency and broader output spectrum only with shorter fiber length.