|Title:||Non-rare-earth doped thin-film photonic materials with ultrabroadband near-infrared luminescence|
|Advisors:||Hao, Jianhua (AP)|
|Subject:||Photonics -- Materials.|
Hong Kong Polytechnic University -- Dissertations
|Department:||Department of Applied Physics|
|Pages:||xxv, 168 pages : color illustrations|
|Abstract:||Photonic materials with near-infrared (NIR) luminescence have continuously received much attention, as they are promising for practical applications in optical telecommunication systems, biomedicine, and light sources. Recently, the development of novel Ni- and Bi-doped photonic materials with ultrabroadband NIR emission are very attractive. Succeeded by the current rare-earth (RE) doped photonic materials, Ni- and Bi-doped materials have great potential application as the gain medium in broadband optical amplifiers and tunable lasers. Since thin-film photonic materials are of great interest in planar optical amplifiers and other integrated photonic technologies. In this thesis, following the studied Ni- and Bi-doped photonic bulks, Ni- and Bi-doped thin-film materials have been synthesized and characterized in this study. First, simultaneous ferroelectric and ultabroadband NIR photoluminescence properties are presented in Ni²⁺-doped perovskite BaxSr1-xTiO₃. Large tuning of NIR emission is realized by chemical substitution, due to the variation in crystal-field acting on Ni²⁺. In particular, Ni²⁺-doped Ba₀.₅Sr₀.₅TiO₃ possesses the most broadly emission band. Then, the dielectric and photoluminescence properties of Ni²⁺-doped Ba₀.₅Sr₀.₅TiO₃ were studied at different temperatures. Using Ni²⁺-doped perovskite oxide bulks as target, Ni²⁺-doped thin films were prepared by pulsed laser deposition (PLD). Large tuning of NIR PL is achieved by Ni²⁺-doped perovskite thin films via chemical substitution. In addition, based on strain engineering, tunable NIR luminescence of Ni²⁺ doped SrTiO₃ thin film grown on piezoelectric Pb(Mg₁/₃Nb₂/₃)₀.₇Ti₀.₃O₃ (PMN-PT) substrate has been demonstrated, through controlling the thickness of STO:Ni film and the modulated strain from PMN-PT.|
Ultrabroadband NIR luminescence has also been observed in Bi-doped oxyfluoride germanate and phosphate glass thin films prepared by PLD. Their emission peaks show tunable performance with controlling oxygen pressure during PLD growth. Systematic investigation revealed that the origins of the luminescence were ascribed to Bi clusters. With the sensitization of Bi NIR active centers, enhanced broadband ~2 m luminescence of Ho³⁺ was realized in Bi/Ho codoped oxyfluoride germanate glass films with high energy transfer efficiency. These results are promising for the realizations of planar waveguide lasers in the NIR region for integrated optics. In conclusion, Ni- and Bi-doped thin film photonic materials with ultrabroadband NIR luminescence have been developed in this study. Their NIR luminescent properties can be modulated by chemical substitution, strain engineering, and controlling the growth process. These results will be very helpful for a better scientific understanding of ultrabroadband NIR luminescence in non-rare-earth doped photonic materials and selection of the potential materials for a new generation of thin-film integrated photonic technology.
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