Ld Pumped Quasi Four-level Doped Nd <sup> 3 + </ Sup> Double-clad Fiber Lasers, Theoretical And Experimental Study

Blue laser has a wide range of applications in high-density data storage, undersea communications, large-screen display, optical detection, medical treatment, life sciences and other areas. Besides the known methods to obtain the blue lasers, this dissertation intends to use another way to obtain the blue laser by using frequency double of double-clad fiber laser.The Nd-doped double-clad fiber laser has strong ⁴F₍(3/2)â†'⁴ I_9/2 transition that could be able to meet the needs of our access to 0.9-0.95μm laser .In this dissertation, the characters of Nd-doped double-clad fiber laser at the quasi-four-level are studied experimentally andtheoretically. The main research subjects list as follows:1. The review of the fiber laser's history, cavity type, clad-pumping styles, and their owncharacteristics.The pump absorption efficiency is studied theoretically with different inner-clad shapes and different bending methods.2. The Nd-doped double-clad fiber laser's quasi-four-level transition is studied theoretically.The expressions of the quasi-four-level Nd-doped double-clad fiber laser's output power, threshold and the slope efficiency are derived and the relationship between the output power and the slope efficiency, pump threshold and some other parameters, such as doping concentration are also simulated by using the origin mathematical software.3. The dissertations focus on the⁴F_3/2â†'⁴I_9/2transition in Nd-doped double-clad fiber lasers. The recent research on⁴F_3/2â†'⁴I_9/2transition in Nd-doped double-clad fiber lasers and the commonly used methods to promote the ⁴F_3/2â†'⁴I_9/2 transition, or to suppress thetransition are also analyzed.4. The Nd-doped double-clad fiber laser is studied experimentally. Three different pumpcoupling system are also studied. By using the aspheric lens coupling system and the end-pump way, 120mW of single mode 907nm laser output is obtained when the fiber length is 14m, the bending radius is 100cm and the pump current is 26 A. Some characters of 907nm laser output are also analyzed.5. The summery and the prospect of the dissertation...