Use of thulium-sensitized rare earth-doped low phonon energy crystalline hosts for IR sources

Abstract

Crystalline hosts with low phonon energies enable novel energy transfer processes when doped with rare earth ions. Two applications of energy transfer for rare earth ions in thulium-sensitized low phonon energy crystals that result in infrared luminescence are discussed. One application is an endothermic, phonon-assisted cross-relaxation process in thulium-doped yttrium chloride that converts lattice phonons to infrared emission, which raises the possibility of a fundamentally new method for achieving solid-state optical cooling. The other application is an optically pumped mid-IR phosphor using thulium-praseodymium-doped potassium lead chloride that converts 805-nm diode light to broadband emission from 4,000 to 5,500 nm. These two applications in chloride crystals are discussed in terms of critical radii calculated from Forster-Dexter energy transfer theory. It is found that the critical radii for electric dipole-dipole interactions in low phonon energy chloride crystals are comparable to those in conventional oxide and fluoride crystals. It is the reduction in multi-phonon relaxation rates in chloride crystals that enable these additional energy transfer processes and infrared luminescence.

Radiation-induced Luminescence Properties of Tm-doped Bi4Ge3O12 Single Crystals

“…The emission at 1600 nm was considered to have originated from the 3 F 4 -3 H 6 transition. (45) Broad emission bands due to the 3 P 1 -1 S 0 transition of Bi 3+ were additionally confirmed at 400-700 nm. (46) The X-ray-induced scintillation decay curves monitored at 160-650 nm and 380-900 nm are shown in Fig.…”