The Spectral Properties Of Thulium Doped Lead Silicate Glasses And Investigation Of Photonic Crystal Fiber

In the past ten years, the output power of continuous wave and pulse fiber laser system have unprecedented improved. The development of high power fiber laser is mainly focused on 1.0 μm band due to the two-level characteristic of Yb³⁺. In recent years, because of the application in medical, industrial, communications, national defense, 2.0 μm laser has developed rapidly. At present, 2.0 μm band laser output in quartz,germanate, tellurite, multi-component glass fiber has been achieved. Due to the low solubility of rare earth ion of quartz glass, the bad anti-crystallization ability of germanate and poor mechanical characteristics of tellurite glass, the power of fiber laser is difficult to further improve for 2.0 μm band. Two paths can be done for achieving high power laser output: First, we can increase the mode field area of the fiber, which can reduce the nonlinear effect in the fiber. Second we can look for the host with high laser damage threshold, the high rare earth ions solubility and excellent mechanical performance. This paper is devoted to seeking for the effective path to realize the above two points. Based on the drawback of the traditional fiber laser in high power laser output and single mode, the photonic crystal fiber is researched. The photonic crystal fiber has many good characteristics: large mode field area, adjustable nonlinear effect and close to the diffraction limit of the beam quality. So it has received widespread attentions.This study aimed at the unique advantages of photonic crystal fiber and lead silicate glass with low phonon energy, broad infrared transmission, high rare earth ions solubility, good anti-crystallization ability. So we carried out the study for the lead silicate photonic crystal fiber. It could be the excellent gain material, which can realize high efficiency and high power laser output, for the 2 microns band. It has great significance in the new band of optical communication and laser.The spectral characteristics of glass and properties of drawing optical fiber can be optimized through adjusting the composition and preparation process of lead silicate glass. The preparation technique of thulium doped silicate glass, the performance of the fiber and the relationship between them were studied. The contents include:（1） The effect of the composition of the lead silicate glass on the 2.0 μm spectra properties of Tm³⁺ ions:The largest luminescence intensity of Tm³⁺ can be achieved when the concentration of Tm2O3 is 1 mol% in Si O2-PbO-K2CO3-BaCO3 glass. In the 1 mol% Tm2O3 doped glass, the calculated J-O intensity parameters of Ω2, Ω4, Ω6 are 4.81, 0.22 and 0.64, respectively. The calculated spontaneous emission lifetime at 1836 nm is 4.89 ms. Additionlly, in this glass, the calculated maximum σabs, σem and the gain coefficient are 2.8×10-21 cm2, 5.67×10-21 cm2, 2.57 cm-1, respectively. All these results show that the lead silicate glass is suitable for the preparation of Tm³⁺-doped lead silicate glass fiber with high gain.（2） The study on the enhanced emission intensity of Tm³⁺ sensitized by Er³⁺:In the Tm2O3 and Er2O3 co-doped SiO2-Pb O-K2CO3-BaCO3 glass, the 2.0 μm luminescence intensity of Tm³⁺ ions can be effectively enhanced by Er³⁺ ions. However, the 2.0 μm fluorescence intensity will reduce when the concentration of Er2O3 continues to increase. Meanwhile, the up-conversions have also been studied. The energy transfer efficiencies from Er³⁺ to Tm³⁺ are 67.1% and 67.4% when pumped by 808 and 980 nm laser diodes. Besides, the mechanisms of energy transfer between Er³⁺ and Tm³⁺ have also been analysised.（3） The research on the preparation of Tm³⁺-doped lead silicate glass fiber:Based on the appropriate process of Tm³⁺-doped lead silicate glass, we have prepared the glass preform by rod-in-tube and drawn out the fiber. The numerical aperture of the fiber is 0.118, while the core diameter and outer diameter of the fiber are 8.4 μm and 125 μm. The background loss of the fiber at 1310 nm was measured to be 4.17 dB/m by using the cutback method. At the same time, 2.0 μm amplified spontaneous emission（ASE） was realized in a 3.5-cm-long as-drawn SM fiber when pumped by a homemade single mode 1560 nm fiber laser.（4） The research on the preparation of Tm³⁺-doped lead silicate glass photonic crystal fiber:The composition of the cladding glass was adjusted, to achieve a good match between the cladding glass and core glass. The numerical aperture of the fiber is 0.02, and the core diameter and outer diameter of the fiber are 30 μm and 280 μm. Based on the theory and software, the characteristic parameters of the photonic crystal fiber have been simulated. The background loss of the fiber at 1310 nm was measured to be 2.91 dB/m by using the cutback method. At the same time, using the microscope, the end face of photonic crystal fiber has also been observed.