Surface Treatment Of Multi-component Phosphate Laser Glass

Narrow linewidth single frequency (or single-longitudinal-mode) fiber laser has a great potential application in laser radar, laser ranging, optical sensor and long distance exploration due to its excellent beam quality, ultra-narrow linewidth and low thermal effects. At present, narrow linewidth single-frequency laser have been obtained in phosphate fiber with a short cavity configuration. However, even though high-purity raw materials and fine melting are adopted, the transmission loss of phosphate fiber is also much higher than the intrinsic loss of phosphate glass. The loss mainly comes form the interface defects and impurities between fiber core and cladding. The defeats and impurities, such as the scratches and holes, mainly come from the cold processing of phosphate fiber preform. They would cause the light scattered and absorpted, leading to a high loss. Therefore, the aim of this dissertation is to improve the fiber core-cladding interface quality and lay a foundation for material process used in narrow linewidth single frequency fiber laser.Phosphate glass with the molar composition 60.9P2O5-15BaO-10Al2O3-1.5Er2O3 -12.6(K2O-Nb2O5-Sb2O3--Yb2O3) was chose in this dissertation. The dissolution mechanism of phosphate glass in acid medium was investigated. The etching effect factors such as solution concentration, temperature, reaction time and ultrasonic stirring etc were also investigated. Based on thermodynamic and kinetic theory, the reaction direction and limit of phosphate glass in acid etching solution was discussed. A dynamic model of dissolution was established to fit the mass loss curves, the dissolution rate curve and the ion concentration curve. Accordingly, a variety of reaction parameters were optimized. Experiments show that the acid solution could remove the glass surface contaminations and defects.A white opaque layer was formed on the glass surface by prolonging the immersion time in hydrochloric acid. This opaque layer limits the diffusion and exchange process of ions, reducing the glass transmittance. The micron-scale crystallines have a lower melting point, so they are easy to re-vitrificated with certain heat treatment and the light transmittance of glass is improved.The results show that, chemical etching followed by high-temperature heat treatment is an effective method to improve the quality of phosphate glass surface, which make the fiber core/cladding interface better matching in rod in tube technology.