Abstract

An upconversion laser pumped at 797 nm has produced 100 mW output at 551 nm with an overall IR to visible conversion efficiency of more than 5%. A high power, narrow band, multi-element semiconductor diode laser system was used to longitudinally pump the upconversion laser crystal in a manner that provided an efficient matching of laser and pump mode geometries and a spectral linewidth that closely matched the absorption width of the active rare earth ion at the operating temperature. The maximum pump power delivered to the upconversion crystal was 1.75 W. The monolithic laser crystal was a 5 mm long cylinder of Er5%:YLiF₄ with dielectric reflectors applied to each end, and was cooled to 48 K. The absorbed pump power was 88% of the incident pump power. The system oscillated on two components of the ⁴S_3/2-⁴I_15/2 transition, at 550.97 nm (air) and 551.25 nm (air). A net IR-to-visible conversion efficiency of 5% was achieved. At the higher powers a slope efficiency of 8% has been demonstrated. Higher output power, improved efficiency, and better beam quality can be achieved with a better mode-match and an improved resonator design.

© 1992 Optical Society of America