Infrared-pumped erbium laser at 550 nm

Continuous wave laser operation in the /sup 4/S/sub 3/2/ → /sup 4///sub 15/2/ transition of Er/sup 3+/ has been achieved using an upconversion pumping scheme in YAIO/sub 3/:Er/sup 3+/ (1%) at a temperature of ≤77 K. Two IR dye lasers were used for pumping with the excitation scheme described. In addition to the above two-laser pumping, the /sup 4/S/sub 3/2/ state is also populated by a cooperative energy transfer process involving two ions in the /sup 4///sub 11/2/ metastable state. To achieve lasing, a 0.3-cm long crystal of YAIO/sub 3/:Er/sup 3+/ was polished with spherical faces (r = 2 cm), and mirror coatings were deposited directly onto these surfaces. The two pump lasers were combined using polarization coupling and focused into the crystal. Threshold was obtained at 35 K with pump powers of 100-150 mW from each laser entering the cryostat. Experiments with increased output coupling are reported. The suitability of other host materials is also being investigated