Abstract
The paper compares the mechanisms that enable the upconverted green emission of the ion under infrared excitation (700–920 nm) in several crystalline hosts and Parameters involved in the upconversion such as excited-state absorption and cross-relaxation rates were determined from spectroscopic measurements. A system of differential equation (rate equations) was used to describe the upconversion mechanism and was numerically solved. The results were compared with experimental data. A reduction of this system to a three-level “simplified system” is presented, which includes only the ground level, the emitting level, and the intermediate level. The differences between the photon-avalanche mechanism and the looping mechanism are discussed and analyzed according to this simplified system.
- Received 19 November 2001
DOI:https://doi.org/10.1103/PhysRevB.65.235119
©2002 American Physical Society