Use of thulium-sensitized rare earth-doped low phonon energy crystalline hosts for IR sources |
| |
Authors: | Joseph Ganem Steven R Bowman |
| |
Affiliation: | 1.Department of Physics, Loyola University Maryland, 4501 N. Charles Street, Baltimore, MD 21210, USA;2.Optical Sciences Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA |
| |
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. |
| |
Keywords: | Rare earth-doped crystals Thulium cross-relaxation Solid-state optical cooling Mid-infrared sources Optically pumped mid-infrared phosphors Potassium lead chloride |
|
|