| As a novel oxide glass host, fluorotellurite glass possesses not only the most advantages of oxide glasses, including excellent physical and chemical stability, lower damage threshold of laser, and easy to process et al.; but also the characteristics of fluoride glass, such as lower phonon energy(650~700 cm-1), longer red-cutting edge(6.1 ?m), and smaller OH absorption coefficient(0.027 cm-1) in the MIR region. All the excellent properties above make fluorotellurite glass and fiber as the most potential materials which can play an important role in the development of visible-infrared fiber devices. In this thesis, based on glass composition of 78TeO2-12ZnO-10Na2O(mol%, TZN78), the host of 60TeO2-30 Zn F2-10NaF(mol%, TZNF60) is thus formed. Intense 549 nm, 660 nm, 1.19 ?m, 2.04 ?m and 2.85 ?m fluorescence are obtainted because of holimiun highly-doping in the glass system. According to the process of experiment, details are described as follows:(1) By using conventional melting and quenching methods, a group of Ho3+/Yb3+ co-doped tellurite glasses(xH3Y-TZN78, x=0.1, 0.3, 0.5, 0.7, 0.9) are made. Pumped by 976 nm laser, bright yellow light is detected easily even by naked eyes, which comes from a mixture of intense green and red emissions. Resulting from the erengy transfer upconversion between Yb and Ho, TZN78 glass is found to present the strongest red flurescence with the intensity about three times higher than that of the green one. Besides, the result of DSC demonstrates that thermal stability of TZN78 glass is very high(?T=156 ℃), thus this group has strong ability of resisting surface crystallization during fiber drawing process. All the results show that HY-TZN78 glasses are very suitable for visible fiber laser development.(2) By physical and chemical dehydration technique, a group of Ho3+ doped fluorotellurite glasses(x Ho-TZNF60, x=0.50, 0.75, 1.00, 1.25, 1.50) are made. Thanks to the variation of composition, great changes of physical properties of tellurite glasses have taken place, such as the decline of refractive index(n=1.8), the shift of Raman frequency peak, and the slight decrease of thermal stability(?T=148 ℃). However, due to the addition of fluorides, physical H2 O molecules and chemical OH groups can be easily removed in the ~3.0 μm region, and therefore open the mid-IR window of tellurite oxide glasses, which plays an important role in the development of tellurite glass and fiber at MIR area.(3) Excited by 1163 nm OPO, intense 2.85 μm fluorescence(Ho3+: 5I6?5I7) is observed: A wide bandwidth of ~83 nm, great simulated emission cross-section of 1.51×10-20 cm2, and the biggest reported fluorescence lifetime of ~0.81 ms among all the reported Ho3+-doped oxide glasses, all of which are benefiting from the water-free characteristic, lower phonon energy of fluorotellurite glasses and thus the lower non-radiative transition rate at the 5I6 level. In addition, 2.04 μm fluorescence(Ho3+: 5I7?5I8) is also detected in this experiment: A broad bandwidth of ~149 nm, the longest reported fluorescence lifetime of ~10 ms, large simulated emission cross-section of 7.2×10-21 cm2, and therefore the maximum figure of merit of 7.13×10-27 m2·s. Fully considering lifetime, emission cross-section and bandwidth, Ho-TZNF60 glass is proposed to be a potential material for midinfrared fiber laser and amplifier developments.(4) Excited by an OPO laser system at 534 nm and 891 nm, intense 1.19(Ho3+: 5I6?5I8) and 1.36 μm(Ho3+:(5S2,5F4)?5I5) emissions in Ho3+ doped TZNF60 glasses are observed. Resulting from the absence of OH groups and the lower phonon energy of fluorotellurite glasses, long lifetimes at 1.19 μm of 750~950 μs and of 32~44 μs for 1.36 μm, respectively, are directly measured. Up to now, there have been few evidences to report the 1.36 μm emission and lifetime of Ho-doped oxide glass systems because of their extremely weak emission intensity. By evaluating the gain characteristics of 1.19 μm, we find that the biggest theoretical gain coefficient is 0.51 dB/cm when the population inversion reaches 0.6. This value indicates that Ho-TZNF60 glass is very suitable for application of optical communication and sensor at the unexplored 1.2 μm region.(5) By “built-in casting method”, “high-speed rotational-casting method” and “rod-in-tube method”, we fabricate fluorotellurite glass fiber based on the component of TZNF glasses. From the results of FTIR, we can easily find that the red-cutting edge of fluorotellurite glasses has broaden from 2.8 μm(TZN glass fiber) to 4.2 μm, which further verifies the effect of F-. Moreover, red shift of transmission range is very important to the mid-infrared luminescence of holmium. Although the loss of TZNF glass fiber is as high as 1.91 dB/m at 1550 nm, we find it can decrease by purifying raw materials and optimizing drawing process. Moreover, the non-resonant nonlinear refractive index n2 and nonlinear parameter γ of TZNF glass fiber are measured by the continuous-wave self-phase modulation(cw-SPM) method, results indicate that n2 and γ are estimated to be 1.4(±0.2)×10-18 m2/W and 20.9 W-1·km-1, respectively. The excellent nonlinear property demoatrates that TZNF glass fiber is a new kind of material which can be used to infrared display device, all-optical switch and supercontinuous fiber laser. |
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