Theoretical And Experimental Studies Of Cladding Pumping Er～(3+)/Yb～(3+) Co-doped Fiber Laser And Amplifier

With the development of LD pumping and fiber manufacturing technology, all kinds of fiber laser come into use. Its application field is expanded from fiber communication to other more fields. People give great passion to the large power pulse fiber laser in 1.5 m wavelength, because of its widely use in communication, medicine, machining and biology et al. We have firstly developed the all fiber femto-second laser, but its average output power is only tens of milliwatt. With the development of cladding pumped technology, it is the efficient way to amplifying the output power.In the paper, we theoretically analyze the absorption efficiency of different shape of inner cladding, the physical and chemical characters of doped rare-earth element and matrix, nonlinear effect in fiber. Double cladding fiber characteristic parameters (doped rare-earth concentration in core, confinement factor, absorption cross and emission cross) are calculated theoretically.In the paper, the configuration of double cladding fiber amplifier is designed. Before amplification, the femto-second seed pulse is stretched by dispersion fiber. The stretched pulse is amplified through doped fiber, and the amplified pulse is compressed by chirp fiber Brag fiber grating. Numerical calculation proves that the configuration of system is reliable.Because high power LD is low cost, easy to manipulate and has high power output, it becomes the best option for pumping source of fiber laser. But the core and NA of LD output fiber is larger than that of double cladding fiber's inner cladding, it is important to analyze the ray propagating and focusing. The intensity distribution of multi-mode fiber is analyzed based on our experiments. And the optimum coupling efficiency is discussed between two multi-mode fiber, especially for the condition that core radius and NA of output fiber are larger than that of input fiber. The coupling efficiency is simulated numerically. And the accuracy of the simulation is approved by our experiments.The amplification characters of Er3+/Yb3+ co-doped fiber are studied in ourexperiments. When the doped fiber length is 50cm, the amplified signal power is 170mW and the gain is 12.2dB in the case of signal power of 10.8mW and pumping power of 2.5W. Then we discuss the influence of laser produced by ASE on signal gain.The research of Er3+/Yb3+ co-doped fiber laser and amplifier is carrying in experiment. The Er3+/Yb + co-doped double cladding fiber is produced by INO, the pumping resource wavelength is 977nm, the maximum pumping power coupling into inner cladding is 1.33W. The output laser wavelength is 1551nm, and the maximum output laser is 312mW with slope efficiency is 31.8%.