Abstract

Laser emission in various regimes was obtained at room temperature in the three-micron range on Er³⁺ transition ⁴I_11/2→⁴i_13/2, despite a much larger lifetime of the terminal level. Various mechanisms have been considered in order to obtain efficient depopulation of ⁴I_13/2 necessary to avoid the self-saturation of the laser emission: excited state absorption of the pump radiation from the terminal level,¹ energy transfer to impurities,² up-conver-sion,³ and, most recently, cascading with 1.5µm emission from ⁴I_13/2 to the ground level ⁴I_15/2,⁴ While the up-conversion is an internal mechanism of the system of Er³⁺ ions and a high Er concentration is necessary in order to be effective, all the other mechanisms require additional external conditions and could act at any Er concentration.

© 1994 IEEE