| The new concepts and technologies for digital data acquisition, processing and transportation strongly accelerated the information age. In order to meet the rapid development of computer network and optical telecommunication, the wavelength-division multiplexing system demands fiber amplifiers with broader and more efficient gain bandwidth in the telecommunication windows.Since its invention in the late1980s, the Er-doped fiber has proven to be a versatile material system with a wide range of applications, including broadband optical sources, wideband optical amplifiers, and tunable lasers. However, the Er-doped fiber amplifier is valid only in a limited range of wavelengths, so it is difficult to meet the needs of development of optical communication systems. On the other hand, the fiber preparation technology has made it possible for fiber communications available window covering1200-1700nm entire near-infrared bands. Based on this, people came up with a vision:using the same optical fiber and a pump source to perform optical amplifier whole optical communication band.In2001, Fujimoto reported infrared broadband luminescence and the1300nm optical amplification at800nm excitation in Bi-doped silica glass. The Bi-doped glass near-infrared glow with bandwidth wide, fluorescence lifetime long benefit is expected to become the new ultra-wideband optical amplification. However, until now, Bi-doped glass fiber not yet commercially available. The main reason is because of its emission mechanism is not clear; lower optical gain intensity and broadband optical emission but not very flat. In this dissertation, we chose Bi and rare-earth co-doped lanthanum aluminosilicate glasses to research subjects. Our purpose is to find the materials that can perform optical amplification in the entire optical communication band. At the same time, through the study of the mechanism of energy transfer between rare-earth and Bi ions to achieve enhanced infrared emission.This thesis mainly focuses on the near-infrared emission spectra of Bi, Tm and Er doped SiO2-Al2O3-La2O3glass under the excited of808nm laser diode and discussed the energy transfer processes between them. The works performed include the following:The Bi-doped lanthanum aluminosilicate glasses with compositions of60SiO2-xAl2O3-(40-x)La2O3-1Bi2O3(x=10,15,20,25,30mol%) were prepared at1600℃for1h, annealed the glasses at600℃for6h to remove the thermal strains. Absorption spectra and fluorescence spectra of the glasses have been measured and discussed. The infrared fluorescence centered at around1270nm with the full-width at half-maximum250nm was observed in Bi-doped glass. The intensity of the near-infrared emission reached the maximum value when the concentration of Al2O3is30mol%. In addition, on the base of the luminescence spectra, we propose that the near-infrared emission from glass might be ascribed to the Bi+ions.The Bi-Tm co-doped60SiO2-30Al2O3-10La2O3glasses, which exhibited a broadband near-infrared emission was investigated by the optical absorption and photoluminescence spectra. The super broadband near-infrared emission from1000to2100nm was observed in the60SiO2-30Al2O3-9.8La2O3-1Bi2O3-0.2Tm2O3glass, as a result of the overlap of the Bi+ions emission band and the emission from Tm3+ions. Relative luminescence intensity at1270,1440and1800nm wavelength varied depending on the mixing ratio of Bi+and Tm3+and the full-width at half-maximum extending from1000to1600nm could be350nm. On the other hand, we deem that there was possibly energy transition process between Bi+and Tm3+ions in the Bi-Tm co-doped lanthanum aluminosilicate glasses.The Bi-Er co-doped60SiO2-30Al2O3-10La2O3glasses, which exhibited a broadband near-infrared emission, were developed and observed in using the optical absorption and photoluminescence spectra. A super broadband near-infrared emission extending from1000to1800nm with a full-width at half-maximum of450nm which covered the whole O, E, S, C, L and U bands, was observed in60SiO2-30Al2O3-9.95La2O3-lBi2O3-0.05Er2O3glass under the excitation of808nm laser diode. In addition, we deem that there was possibly energy transition process between Bi+and Er3+ionsThe near-infrared luminescence property of Bi-Tm-Er co-doped lanthanum aluminosilicate glasses was also studied. When the glass composition is60SiO2-30Al2O3-9.55La2O3-1Bi2O3-0.4Tm2O3-0.05Er2O3, a super broadband near-infrared emission with the relatively flat amplification from950to1600nm was observed. On the other hand, we found a super broadband luminescence with the full-width at half maximum of750nm from950to2100nm in the60SiO2-30Al2O3-9.7La2O3-3Bi2O3-0.2Tm2O3-0.1Er2O3glass. In addition, energy transfer process between Bi+, Tm3+and Er3+ion in glasses were also discussed.These researches has great value to make further understanding on the mechanism of energy transfer between Bi+, Tm3+and Er3+ions in lanthanum aluminosilicate glass. In addition, glass components listed above could provide potential applications in tunable lasers as well as the broadband optical amplifiers in the wavelength-division multiplexing system. |
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