A ytterbium fiber laser emitting 60 watts of power at 1064 nm has been designed, fabricated, and tested. The laser has an 83% optical efficiency at this power level, ~ 10% under that predicted by the quantum defect. Typical continuous wave nonlinearities have not been detected in the laser’s output characteristics. Additionally, amplified spontaneous emission at 1030 nm has not occurred at an observable level within the laser’s spectral output. Other deleterious effects on high-power laser operation are discussed. The spectral output has precisely controlled spectral characteristics enabled by the use of fiber Bragg gratings as cavity mirrors. Additional spectral peaks are observed in the output of the resonator. The probable cause of the unexpected spectral features is parasitic lasing from Fabry Perot effects between the output facet of the fiber and the high reflectivity Fiber Bragg Grating. The future addition of an endcap will enable this system to generate greater than a kilowatt of output power while eliminating spectral abnormalities. Challenges during construction related to splicing and the results of the implemented improvements are documented. Unmanageable thermal complications with fusion splicing required the refinement of splicing, decontamination, and cleaving protocols. Standard splice functionality was ultimately regained, and assembly of the laser was continued. This laser is expected to be deployed at the Townes Institute Science and Technology Experimentation Facility (TISTEF) upon completion of the kilowatt power build. Beam shaping characterization studies will be performed upon laser delivery. Emphasis will be placed on interactions between nondiffracting beams and atmospheric turbulence.

Fiber lasers represent the state-of-the-art in laser technology and hold great promise for a wide range of applications because they have a minimum of exposed optical interfaces, very high efficiency, and are capable of exceptional beam quality. In the near future, the most important markets such as micromachining, automotive, biomedical and military applications will begin to use this technology. The scope of this thesis is to design and develop a short picosecond pulsed fiber laser using rare-earth doped fiber as a gain medium. The proposed master oscillator power amplifier (MOPA) will be used to generate pulses with high repetition rates. In this study, first we explain the basic theoretical background of nonlinear optics and fiber laser. Then, the numerical simulation will be introduced to explain how the laser system design and optimization. The simulation is based on nonlinear Schr&ouml / dinger equation with the method of split-step evaluation. The brief theoretical background and simulation results of the laser system will be shown. Finally, the experimental study of the developmental fiber laser system that comprises an oscillator, preamplifier and power amplifier will be discussed.

Le remplacement des lasers à gaz émettant à 488 nm ou à 442 nm, à l'aide de lasers solides, représente un véritable enjeu industriel. De nombreuses solutions ont été développées, néanmoins, celle consistant en le doublement de fréquence d'une oscillation autour de 884 nm (cristaux dopés aux ions Nd3+) ou de 976 nm (cristaux dopés aux ions Yb3+) a toujours été écartée, de par la nature à trois niveaux des transitions mises en jeu. La très forte réabsorption du milieu à la longueur d'onde laser rend, à première vue, cette alternative peu efficace. Grâce à la significative amélioration de la luminance des diodes de pompe, ce problème peut désormais être dépassé et l'oscillation de ces transitions envisagée. Dans ces travaux, nous proposons une étude théorique et expérimentale de l'oscillation laser en pompage par diode des transitions à trois niveaux dans les cristaux dopés aux ions Nd3+ et Yb3+. Tout d'abord nous présentons l'étude du pompage direct par diode d'un cristal de Nd:GdVO4 émettant à 880 nm, qui après doublement de fréquence nous permet de proposer une alternative aux lasers à HeCd. Nous présentons ensuite un nouveau concept, le pompage en intracavité, que nous appliquons aux cristaux dopés aux ions Yb3+ pour obtenir un effet laser autour de 980 nm. En effet, à l'intérieur d'une cavité laser, la forte puissance circulante est couplée à une bonne qualité spatiale de faisceau; ces caractéristiques représentent les conditions optimales de pompage d'une transition à trois niveaux. En conclusion, nous proposons une comparaison théorique des différents types de pompage proposés, permettant de dégager avantages et inconvénients de chacune de ces deux configurations.