Glasses and Glass ceramics doped with RE³⁺ ions

Glassy and glass-ceramic materials are highly versatile alternatives to optical crystals for photonic and bio-photonic applications. Since the development of the laser in 1960, there has been a great interest in laser glasses based on the narrow emissions of trivalent rare-earth ions, mainly in the near-infrared region (~ 1.0 μm). These ions play a fundamental role in many technological fields. For example, at the first optical transmission window for telecommunications, the usage of the Er³⁺ emission at 1.5 μm stands out. At spectral regions corresponding to the absorption by water there are Er³⁺ (2.8 μm) and Tm³⁺ (1.8 μm) lasers. Yb³⁺ high power lasers at ~1.0 μm are used for nuclear fusion. In the visible region, from blue to red, Tm³⁺, Tb³⁺, Er³⁺, Dy³⁺ and Eu³⁺ emissions are employed in optical recording of data, biological markers, submarine communication, lighting devices, white light generation, etc.
RE³⁺-doped glasses can show conversion of low energy radiation (e.g., infrared) to higher energy radiation (e.g., visible or UV) through the process known as upconversion. Conversely, high energy radiation can be converted into lower energy radiation (downconversion and/or quantum-cutting). All these processes allow the development of materials that absorb UV and IR portions of the solar spectrum and convert them into radiation that can be absorbed by c-Si photovoltaic cells. Recently, a lot of attention has also been given to glass and glass-ceramics scintillators capable of converting high energy radiation such as UV-C, X-rays and β rays to the lower energy UV-A and visible radiation.
For each application, some material requirements must be met through the proper choice of the system’s composition and a number of fundamental properties can be adjusted during processing: phonon energy, excited-state lifetime, emission intensity as a function of dopant concentration, chemical, mechanical and thermal stability, etc. For the last 15 years, researchers at LEMAF have been studying numerous glass systems such as borates, phosphates, fluorides, oxy-fluorides and chalcogenides. Strategies to enhance the emissions efficiency of dopant ions include the controlled growth of metallic nanoparticles (Ag, Au) in the RE³⁺-doped glasses, controlled crystallization of different phases in glass-ceramics and co-doping with other sensitizing ions.
We characterize the optical properties and the structure of these amorphous materials by steady-state and time-resolved photoluminescence as well as Raman and solid-state NMR and EPR. The structure-property correlations give feedback to the synthesis process in order to optimize the desired properties.