Room-temperature green upconversion fluorescence of an Er(3+)-doped laser liquid.

Room-temperature green upconversion fluorescence of an Er(3+)-doped POCl(3)-SnCl(4) solution is achieved when the solution is pumped with an 800-nm GaAs laser diode. The upconversion emission at 550 nm is determined to be the result of a two-step absorption process. Numerical analysis reveals that laser systems that employ this erbium-doped laser liquid should be realizable with threshold pump powers as low as 45 mW.