Development of 2 Micron Fiber Lasers for Material Processing

Abstract

In this dissertation, 2 μm fiber lasers with tailored properties are designed and constructed for material processing, especially for semiconductors. An all-fiber nanosecond laser at 2 μm was firstly used to explore the potential application in direct semiconductor processing. Due to the transparency of silicon at this wavelength, the absorption of light is nonlinear, allowing better confinement of deposited energy. By creating fine structures, black and superhydrophilic surfaces were demonstrated with regular silicon wafers. Besides surface modification, micro-joining of silicon to other dissimilar materials was achieved without surface damage. To improve the processing performance and to access to more processing regimes, ultrafast laser sources are needed. After the investigation of intracavity pulse dynamics with numerical simulations, a high energy femtosecond laser oscillator at 2 μm was constructed. Next, to make laser immune to the environmental perturbations, an all-polarization-maintaining dissipative soliton fiber laser was demonstrated. This laser was based on a newly developed thulium-doped silicate fiber with normal dispersion and high gain. The potential of the new fiber was also explored with numerical simulations. For further improvements, a novel optical fiber structure was proposed. Guided by the theoretical analysis, the fiber was fabricated with rod-in-tube technique and experimentally investigated.