Analysis On Influence Of The Way Of Pumping On Double-clad Pumped Fiber Lasers

At present, double-clad pumped fiber laser is popular because of the virtues of high-quality of laser bean, low-threshold, high-power and so on. With the development of technology of the single-mode fiber, the double-clad fiber laser has draw more and more attention, and it can be widely applied in the optic-communication, precision machining, aerospace and so on.The aim of research is to analyze the trace of the pump radiation launched into the double-clad fiber laser, and to search a feasible measure to improve the performance of the double-clad fiber laser by simulating the cladding pumped fiber laser.The background of the technology of cladding-pumped fiber, the structure, and the characteristic of cladding pumped fiber lasers are analyzed .at the same time, the state of the research and development way in the field of fiber laser worldwide are summarized.Firstly, the pumped radiations launched into the double-clad fiber laser have been traced with the geometric optics and the propagation of the pump light within the inner clad has been analytically analyzed, the expression for the distance between different rays in the process of propagation and central axis of fiber core has been derived and then we got the expression of the traveling distance of pump rays inside the fiber core.Secondly, theoretic model and the theoretical analysis' method of the four-level system cladding-pumped fiber lasers are analyzed. Based on the rate equation model of four-level system fiber laser, the module of the cladding-pumped is simulated .the influence of forward-pump, backward-pump, double-pump on the performance of the cladding-pumped fiber laser in the situation of scattering-loss and scattering-lossless.The conclusion of research can be concluded as followed:1 Without the consideration of the scattering-loss, we can conclude that the power of output is increased with the increasing of length of the laser by using the way of forward pump, however, the speed of increasing decreased. By the way of backward pump, the power of the output is increased with the increasing of the length of the laser, the speed of increasing increased. By the way of double pump, the power of the output is increased slowly, but the power of output increase quickly in the output point due to the backward pumping optical.2 With the consideration of the scattering-loss, we can conclude that the power of output is increased with the increasing of length of the laser in the way of the forward pump. However, the power of the output decreased when the power of output reach the highest-point. In the way of backward pump, the power of the output is increased with the increasing of the length of the laser, the speed of increasing increased. In the way of double pump, the power of the output is increased slowly, but the power of output increase quickly in the output point due to the backward pumping ray. Also, the power of output can be influenced by the dispersion loss.At last, the influence of the three way of pumping and scattering-loss coefficient of pumping on the power of the output have been researched, the power of the laser increase with the increase of the pumping optical power, and the power of the laser reduce with the increase of scattering-loss coefficient of pumping.