Silica and Germanate Glass High Power Fiber Laser Sources

Abstract

Abstract : The overarching aims of this project were to develop capabilities in fundamental materials, fabrication techniques, and design of two leading candidate glass systems for new fiber laser architectures operating in the 1-4 micro m spectral region. The research involved investigation of fundamental design and thermal limitations of IR silica fibers in the 2-2.1 micro m range; of techniques for power handling using air structured cladding; and examination and characterization of Tm+ doped germanate glass fiber lasers that operate in the 2-3.5 micro m range. Research accomplishments include successful fabrication of a range of index and microstructured guided rare-earth doped silica fibers using a modified chemical vapor deposition system; development of an air-jacketed 2.1 microstructured fiber and fiber laser with demonstrated high quantum efficiency; demonstration of a range of germanate glasses and optimization for laser and non-linear applications; development of extruded germanate microstructured preforms that have been drawn into microstructured optical fibers suitable for laser and non-linear applications; and fabrication of a range of undoped and holmium doped germanate microstructured fibers. Judd-Ofelt modeling was undertaken to estimate branching ratios and emission cross-sections and predict laser performance of rare earth doped germanate glass lasers. Simulations and fabrication of leaky-mode large mode area fibers was also investigated. This research led to development of novel complex microstructured features in a relatively immature glass (especially when compared to silica), whilst maintaining low-loss, and testing the design as a laser in the short to mid-infrared, which is one of the hardest spectral regions to operate a laser.