Study On 2 μm Barium Gallo-germanate Glass Single-mode Optical Fiber

Fiber lasers operating around 2.0 μm have been widely used in atmospheric monitoring, eye-safe light detection and ranging, laser medicine, and spectroscopy. The laser performance of commonly used silica fiber has been limited due to the low rare-earth solubility. In recent years, multi-component glasses have received intensive interest due to its high rare-earth doping concentration. Particularly, the barium gallo-germanate(BGG) glass, which combines excellent optical property with good physicochemical and mechanical characteristics has become a research topic as the promising 2.0 μm fiber laser host glass. But to date, majority of the researches only investigated the spectroscopic characteristics of rare earth ions in the BGG glasses, the fabrication of high-quality BGG glass fibers still encounters some bottlenecks.In this dissertation, high-quality heavily Tm3+-doped barium gallogermanate single-mode(SM) glass fibers were successfully fabricated by enhancing the glass anti-crystallization ability, developing efficient dehydration method and optimizing the fiber fabrication technique. All-fiber laser performances of as-drawn Tm3+ doped BGG SM glass fibers were also investigated. The specific research contents and results are as follows:(1) According to the results of glass DSC curves, heat-treatments and fiber drawing processes, the anti-crystallization ability of BGG glass were studied. It was found that that co-doping La2O3 and Y2O3 into BGG glass could enhance the glass thermal stability. Meanwhile, the dehydration techiniques would have further effects on the glass anti-crystallization ability. Using Reaction Atmosphere Procedure or fluoride to remove the OH- content would decrease the glass anti-crystallization ability, while dehydration techinique as bubbling high-purity O2 into glass could avoid the bad effects.(2) Bubbling high-purity O2 into glass was utilized as the dehydration technique. The effects of the O2 flowing time, flowing rate and flowing tempreture on the dehydration efficiency were investigated to optimize the dehydration techunique. The OH- absorption efficiency of sample melted with the optimized dehydration techunique was 1/10 of the value in the non-dehydrated sample, indiating that the optimized dehydration techunique is an efficient way to remove the OH- content in BGG glass.(3) High-quality BGG core glass and the well-matched cladding glass with low OH- content and high anti-crystallization ability were obtained. The Tm3+ dopant concentration in BGG core glass was 7.6×1020 ions/cm3. Heavily Tm3+-doped BGG SM glass fibers were fabricated by the rod-in-tube fiber drawing technique in the drawing tower. The obtained glass fibers featured a core diameter of 9.2 μm and cladding diameter of 125 μm, together with a numerical aperture of 0.132.(4) Single-frequency 2.0 μm fiber lases were realized by using 1.6 cm, 2.1 cm, 2.5 cm as-drawn BGG SM glass fibers in a distributed Bragg reflector(DBR) cavity when pumped by a homemade 1568 nm fiber laser. The center wavelength of the laser was around 1950.02 nm. The maximum laser output powers were 35 m W, 53 m W, and 73 m W with corresponding slope efficiency of 5.5%, 8.7%, and 10.1%, respectively. Addtionally, fiber lasers with multi-longitudinal modes were achieved by using the 5-cm and 10-cm BGG active fibers. The center wavelengths of the lasers were 1949.95 nm and 1950.01 nm, respectively. The maximum laser output powers were 89 m W and 165 m W with the corresponding slope efficiency of 10.1% and 17.0%, respectively.