The Study Of High Power Fiber Laser

Fiber laser is a research hotspot in the fields of lasers, recently, which was paid more attention by people because of it's excellent performance and low price. Fiber laser was invented by Snitzer in 1961,and it's development was slow for being restricted of condition. The previous fiber laser used single-mode fiber, emitted a few tens of millwatts. For many laser applications, however, watts of optical power rather than millwatts are required. Until 1988 the invention of double clad fiber deliver the base of realization of watts even higher power fiber laser. The study of fiber laser had large progress with the development of high power diode laser and technology doping fiber in the 1990s, output power was increased from 500mw of 1994 to 2000w of 2002. The modern high-power fiber laser is pumped by high-power multimode diodes via a cladding surrounding a single-mode core. In the early time, the concept allowed the efficient conversion of multimode output radiation from a solid-state pump laser, or a broad-stripe semiconductor laser diode (or an array of laser diodes) into single-mode emission of fiber lasers. In the simple double-clad fiber architecture, an axial single-mode glass core is doped with the desired laser ion (neodymium, erbium, ytterbium, and thulium are some examples). This core fiber is encased in a surrounding undoped glass cladding that has a diameter many times that of the core fiber as well as a lower index of refraction. The inner pump cladding, in turn, is encased in an outer undoped glass cladding of yet-lower index of refraction. In this fiber architecture, multimode diode pump radiation is injected into the pump cladding through an end facet of the composite fiber, propagates along the fiber structures, periodically traversing the doped single-mode fiber core, and produces a population inversion in the core fiber, and coupling efficiency and conversion efficiency were enhanced, output power of laser was increased.High power fiber laser hang together both bumping technology of high power diode laser and manufacture technology of doping fiber. Nowadays, high power fiber laser attracted many scientist because of it's capabilities. In this thesis, based on the concept of r double-clad fiber, a deep and systematical study has been developed around the properties of high power Yb3+-doped double-clad fiber laser. The contents of the paper including:First of all, it summarized the international research progress of double-clad fiber lasers. It pointed out the significance of the research of double-clad fiber laser components, and introduced simply my work.2.According to the characteristic of Yb3+ level, the absorption and emission spectrum of Yb3+, We gave the theoretical analyses about the choice of pump source.3.Analyzed the capabilities of Yb3+-doped double-clad fiber laser, introduced the design of cavity of double-clad fiber laser, discussed high power fiber laser based on cavity of fiber Bragg-grating.4.Based on analysis of theory, discussed the relation of the input and output characteristics by numerical analysis. In the meantime, we adjusted LD's wavelength by control of temperature, analyzed the characteristics of fiber laser.5.Experimental research on all-fiber laser: with designing the experimental setup and testing system of fiber laser, We got a double-clad fiber with the output wavelength 1100nm, output power 10.8w, slope efficiency 59%, optical-optical conversion efficiency 58%, total electric- optical conversions efficiency 18.7%, output laser mode TEM00. It's the first time in domestic research.6．Introduced the development of pulse double-clad fiber laser, discussed three realizing ways and compared. 7.In the end, the development and possible application of high-power fiber lasers and new-type structure fiber lasers will be discussed. Currently, the finite brightness of pump sources and the numerical aperture of the inner cladding collecting the pump light limit the pump power that can be coupled into the end of the fiber. This effectively...