The Spectral Properties Of Thulium Doped Silicate Glasses And Investigation Of Fiber Preparation

Fiber laser is a new laser source in the 21 st century which has experienced the rapid development from 1.0 μm to 1.5 μm. Now, researchers are focusing on the mid-infrared waveband, especially the 2.0 μm wavelength. 2.0 μm laser source has an irreplaceable role in military, medical, space communication, and so on. 2.0 μm laser has been achieved in silica and several multicomponent glass fibers. However, as to the pulse fiber laser of high peak power at 2.0 μm, its peak power is hard to be improved for lack of 2.0 μm optical fiber materials with higher gain and higher anti-laser damage threshold.Silica fiber has many advantages, such as lower optical loss and more mature preparation technology compared with other glass fibers, but its lower solubility of rare earth ions severely limits the improvement of the gain in the active fiber. At the same time, t he silicate glasses provide more stable physical and chemical properties, higher mechanical strength, higher anti-laser damage threshold than other multicomponent glasses. Besides, higher solubility of rare earth ions will be realized after selecting and adjusting the composition of the silicate glasses. Then the fabricated 2.0 μm silicate glass fiber with higher gain will lay a good foundation for the pulse fiber laser of high peak power at 2.0 μm.This dissertation is aimed at fabricating Tm3+-doped silicate glass fiber with better performance by optimizing the composition of the silicate glasses and fiber drawing technology. Additionlly, the property of the fiber has been studied. The research contents are as follows:(1) The effect of the composition of the silicate glass on the 2.0 μm spectra properties of Tm3+ ions:We find that the luminescence intensity of Tm3+ is largest when the concentration of Tm2O3 is 1 mol% in Si O2-Na2O-K2O-Ba O-Nb2O5-Sb2O3-Al2O3 glass. In 1 mol% Tm2O3 doped glass, the calculated J-O intensity parameters of Ω2, Ω4, Ω6 are 4.05, 0.78, 0.32, respectively. And the calculated spontaneous emission lifetime at 1836 nm is 5.96 ms. Additionlly, in this glass, the calculated maximum σabs, σem and the gain coefficient are 1.57×10-21 cm2, 3.34×10-21 cm2, 1.58 cm-1, respectively. Obviously, these large parameter values mean that this silicate glass is a good choice for the preparation of Tm3+-doped silicate glass fiber with high gain.(2) The research on how to eliminate OH- in the silicate glasses:We find that in Si O2-Al2O3-Ca O-Ba O-Sb2O3 glasses, the method of reaction atmosphere process(O2 + CCl4) is the most effective to reduce OH-, but it can lead to a large number of volatilization of Na2 O and K2 O in Si O2-Na2O-K2O-Ba O-Nb2O5-Sb2O3-Al2O3 glasses. When removing water by the introduction of fluorides, we find that prolonging the time of bubbling O2 and increasing the introduction of fluorides can both benefit to eliminate OH-. At the same time, that can also strengthen the fluorescence intensity in Tm-doped glasses Si O2-Na2O-K2O-Ba O-Nb2O5-Sb2O3-Al2O3, but it is more likely to cause crystallization in glasses Si O2-Al2O3-Ca O-Ba O-Sb2O3.(3) The study on the enhanced emission intensity of Tm3+ sensitized by Cr3+:In 1 mol%Tm2O3 and 0.1 mol% Cr2O3 co-doped Si O2-Na2O-K2O-Ba O-Nb2O5-Sb2O3-Al2O3 glass, the energy transfer efficiency from Cr3+ to Tm3+ is 40.97 % when excited with 430 nm xenon lamp. And when pumped by 808 nm LD, the 2.0 μm luminescence intensity of Tm3+ ions can be effectively enhanced by Cr3+ ions in this Cr3+/Tm3+ co-doped glass. However, the 2.0 μm fluorescence intensity will reduce when the concentration of Cr2O3 continues to increase. Meanwhile we have analysised the mechanism of energy transfer between Cr3+ and Tm3+.(4) The research on the preparation of Tm3+-doped silicate glass fiber:After achieving the appropriate formula of Tm3+-doped silicate glass, we have prepared the glass preform by rod-in-tube and drawn out the fiber. The numerical aperture of the fiber is 0.136, while the core diameter and outer diameter of the fiber are 9.8 μm and 125 μm. The background loss of the fiber at 1310 nm was measured to be 19.01 d B/m using the cutback method.