Green infrared‐pumped erbium upconversion lasers

Upconversion pumping with near‐infrared cw dye lasers was used to achieve laser action at 550 nm on the 4S3/2→4I15/2 transition of Er3+. In YAlO3:Er3+, upconversion excitation occurs via sequential two‐photon absorption. In YLiF4:Er3+, energy transfer upconversion involving two Er3+ ions in the intermediate 4I11/2 state causes excitation of the upper laser level. These upconversion lasers operate at temperatures up to 90 K. With pump powers of several hundred milliwatt near 800 nm we have obtained 550‐nm output powers in the miliwatt range.