INFRARED-PUMPED ERBIUM LASER AT 550 NM.

Continuous-wave laser operation in the 4S//3/////2 yields 4///1//5/////2 transition of Er3** plus has been achieved using an upconversion pumping scheme in YAlO//33 plus (1%) at a temperature of less than equivalent to 77 K. Two IR dye lasers were used for pumping. In addition to the above two-laser pumping, the 2S//3/////2 state is also populated by a cooperative energy transfer process involving two ions in the 4///1//1/////2 metastable state. The presence of this effect is apparent from observation of strong green fluorescence when only the first pump laser is present. In the 1% Er3 plus crystal, this process contributes significantly to reaching threshold.