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Theoretical And Experimental Study Of Ytterbium-doped Double-clad Fiber Laser

Posted on:2008-11-30Degree:MasterType:Thesis
Country:ChinaCandidate:H Y ZhangFull Text:PDF
GTID:2178360245991887Subject:Physical Electronics
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Yb-doped double-clad (YDDC) fiber lasers have the advantages of compact structure, simple cooling, broad pumping wavelengths, high efficiency, high power, long-life and they are widely used in optical communication, industry process, medical treatment, laser printing and label-making.YDDC fiber lasers are studied both theoretically and experimentally in this dissertation. The main points can be concluded as follows:1. The principal, application and rencent development of YDDC fiber lasers have been introduced.2. A fast, accurate and stable algorithm for CW fiber lasers has been proposed. Based on shooting method, the solution of the rate equations of CW fiber laser with boundary conditions is converted into an unconstrained optimization problem for the first time. BFGS algorithm combined with Newton algorithm is a good choice for its fast rapidity of convergence and good global convergence.The algorithm can be also applied to fiber amplifiers to solve the steady equations. The algorithm for the Q-switched fiber lasers is also discussed.3. The output characteristics of YDDC fiber lasers for forward pumping, backward pumping and bidirection pumping have been simulated by numerical modelling. The impact of fiber length, doped concentration and the signal reflectivity at the fiber output end on the output power has been studied. It has been firstly proposed that for the high power YDDC fiber lasers when other parameters are constant, the maximal output power can be gained with appropriate distribution of the two-end-pumped power and a full discussion has been made on how to distribute the two-end-pumped power. It will be helpful for improving the output power of fiber lasers in theories.4. The CW and Q-switched YDDC all fiber lasers have been studied in experiment.(1)Pumped by a 975 nm laser diode (LD) of 12.008W, the CW laser of 3.426W is obtained at the wavelength 1083.20nm and the efficiency is 28.5%.(2)Pumped by a 975 nmLD of 8.47W with the repetition frequency of the Q switch of 500 Hz, the active Q-switched pulse at the wavelength 1083nm is obtained with a 3μs pulse width and an average power of 1.47W. The single pulse energy is 2.94mJ and the peak power is 980W. The repetition frequency can be adjusted from 0.5 kHz to 30 kHz.(3)Pumped by a 975 nmLD of 6.52W with the the active and passive Q-switched method by use of the SBS effect in the single mode fiber, the steady pulse at the wavelength 1083nm is obtained with a 150 ns pulse width and the repetition frequency is 50 kHz. The average power is about 1.02W and the single pulse energy is 0.02mJ with the peak power of 133W.
Keywords/Search Tags:Yb-doped double-clad fiber laser, numerical simulation, optimization method, BFGS algorithm, the optimal pump power distribution, Q-switch, all fiber
PDF Full Text Request
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