Diode-Laser-Pumped 551-nm Upconversion Laser in YLiF₄;Er³⁺

Abstract

A single-mode diode laser at 802 nm was used to pump the 4/15/12 → 4/9/2 transition of LiF4:Er3+, producing up to 2.3 mW of lascr output at 551 nm (4S3/2 → 4/15/2)at 50 K; 0.5 m\V of geen output were obtained at 77 K. The upconversion mechanisms were found to dopend on the pump wavelen@h. Energy transfer cross-rclaxation is generally the dominant mechanism, but at certain pump wavelengths two-step absorption bccomes important. Lasing at 560.6 nm froni the 2H912 leve1is also reportcd. Although the upconversion excitation of 2H9/2 requires more than two pump photons, the effiiciency of this laser is comparable to that at 551 nm which uscs a two-step process.