The Research Into The Theories And Medical Applications Of Fiber Lasers

The unparalleled predominance of fiber lasers has attracted interests of researchers throughout the world and great attentions of industry. Composite crystal fiber lasers and polarization-maintain large-mode-area fiber amplifiers are researched and combined to form the high power green laser that may be used for therapy of benign prostatic hyperplasia(BPH). The photoselective vaporization of the prostate(PVP) using the laser system is promising.The basic theory including physical principles of the fiber laser, the atomic structure, energy level and spectral characteristic of doped lanthanide has been introduced. Fiber lasers have been classified and the design of their resonant cavity has been provided. At present, double clad doped rare-earth fiber lasers and photon crystal fiber lasers are the most important approaches to scale the output power. Moreover, SRS and SBS fiber lasers based the nonlinear effect in the fiber, fiber soliton lasers, supercontinuum and ultrafast fiber lasers with great value both in theory and in practice have been discussed. Optical amplifiers and the rate equations then have been studied. The applications of fiber lasers in various fields have also been analyzed particularly. Finally the potential of fiber lasers substituting the traditional solid lasers and gas lasers has been pointed out but the time that it come true is in the future, at the same time they will also confront the possible competition which come from diode lasers.Various methods of the growth of crystal fibers have been investigated and they are Laser Heated Pedestal Growth(LHPG), capillary-fed melt growth, Capillary-Bridgeman growth and Float-zone or pedestal growth. Subsequently, the character of LHPG technique has been showed. It paves the way for the use of LHPG technique in this chapter.Q-switching technique, especially the interesting passively Q-switching, for getting ultrashort pulse has been discussed. Composite crystal fibers incorporating Nd:YAG and Cr4+:YAG are grown by the laser heated pedestal growth technique, which is considered to be a powerful tool for rapid growth of high-melting temperature oxides and incongruent melting compositions. After handling the composite crystal fiber laser is demonstrated. Using the velocity rate theory, the parameters are calculated by numerically method and they are well in accord with the experiment results. The composite passively Q-switching crystal fiber lasers can obtain excellent performance.Photonic crystal fibers (PCFs), the revolutionary power in the fiber family, and their produce techniques have been introduced. They have very intensive optical nonlinear effect, high birefringence, fantastic dispersion, ceaseless single mode transmission characteristic and dreamlike performance parameters. They can be used to form lasers with higher average power or peak value power. In a word they are the instruments that can rein the photon imaginably! Various theories and numerical analyzing methods of the photonic crystal fiber laser have been listed.Laser prostatectomy of BPH has been studied. Therefore various laser-induced bio-tissue vaporization experiments have been carried out and the reasonable parameters of the laser tissue vaporization have been searched. Consequently the photoselective vaporization of the prostate with green laser is the preferred for lots of advantages of the method. The results are in accordance with the reports that have been released and exhibit the refulgent prospect of the green laser used in therapy of BPH.Utilizing the composite crystal passively Q-switching fiber laser and polarization maintain large mode area fiber as the seed light signal and amplifier respectively, the signal light is amplified to more than 100W and is doubled frequency by the KTP crystal with temperature manager equipment thereby high power green output can be obtained. The laser system has the predominance of simple design, high reliability, and high power.