The Luminescence Properties Of Rare Earth Ions Doped Luminescent Glasses

Rare earth ions exhibit rich energy levels, a multitude of energy level transition pathways and long fluorescence lifetime, which can be as significant medium to achieve spectrum conversation. Rare earth ions have potential application prospect in many aspects, such as solar cells, lasers, white LEDs, fiber amplifiers and fluorescent bio-probes. Therefore, research on the luminescence properties of rare earth and their related host materials has become an important subject in different countries. In this background, this thesis focuses on the investigation and study of rare earth doped optical glasses which combines with the actual application on solar cells and optical fiber amplifiers. The following shows the four research topics in this thesis: 1. Spectral down-conversion based on energy transfer of Tb³⁺/Yb³⁺ ionsCrystalline Silicon-based solar cells（c-Si）, which band gap of 1.12 eV corresponding to a wavelength of 1100 nm, have weak photoelectric response at the range from near ultraviolet to blue light. Therefore, we would like to convert near-ultraviolet and blue spectrum to near-infrared（NIR） light by means of down-conversion（DC） characteristics, to improve the photoelectric response of c-Si solar cells. We prepared the Tb³⁺/Yb³⁺ co-doped phosphate glasses by melt-quenching method, and analyzed energy transfer of Tb³⁺/Yb³⁺ ions. The results demonstrated that the DC process occurred from Tb³⁺ to Yb³⁺ at the excitation of 486 nm. In addition, the energy conversion efficiency（ECE） of solar cell covered by the 0.5mol% Tb³⁺ and 0.5mol% Yb³⁺ codoped glass was measured which increased by 0.34% comparing with the cell covered by host glass. 2. Spectral down-shifting based on energy transfer of Tb³⁺/Eu³⁺ ionsAmorphous Silicon solar cells（a-Si）, which band gap of 1.75 eV corresponding to a wavelength of 708 nm, have weak photoelectric response at near ultraviolet region（300-400nm）. Hence, we prepared the Tb³⁺/Eu³⁺ co-doped phosphate glasses based on Tb³⁺ and Eu³⁺ ions which existed broadband absorption characteristics in the near ultraviolet region. The results manifested that the fluorescence emission occurred at the range wavelength from 500 to 700 nm. Furthermore, the energy transfer process from Tb³⁺ to Eu³⁺ was investigated in Tb³⁺/Eu³⁺ codoped phosphate glass in detail. The ET mechanism from Tb³⁺ to Eu³⁺ was ascribed to the cross relaxation. 3. Energy transfer and broadband near-infrared emission based on Pr³⁺/Er³⁺ ionsContinuous increasing demands for network traffic have led researchers to develop amplifiers for optical communication system with broader bandwidth. Therefore, it is attractive to develop superbroadband optical amplifiers that cover entirely the expanded low-loss telecommunication window. The most widespread amplifiers are Erbium-doped fiber amplifiers（EDFA） which are difficult to meet optical communication requirements as their gain bandwidth has no more than 70nm（1530-1600nm）. Herein, we reported near-infrared（NIR） emission spectra of Pr³⁺/Er³⁺ codoped phosphate glasses with 483 nm excitation. A broadband emission extending from 1300 to 1640 nm was obtained and the related mechanism was also investigated. 4. Ultra-broadband NIR gain spectra based on Co²⁺ ionsIn order to study the NIR gain spectrum of Co²⁺ ions, we took glass-ceramic fiber as the substrate. We established a quasi-three-level system model, then utilized the rate and power propagation equations to analyze the Co²⁺ doped glass-ceramic fiber. It is shown that when pumped at 1200 nm, the fiber has ultra-broadband gain spectra in 1250-2000 nm range, which is promising for full-band fiber amplifiers.