Laser-relevant spectroscopy and upconversion mechanisms of Er3+ in Ba2YCl7 pumped at 800 nm

摘要

We present a comprehensive spectroscopic study of the possible room-temperature green laser transition H-2(9/2), I-4(13/2) in Ba2YCl7:3%Er3+. Because of the low phonon energies, 270 cm(-1) in Ba2YCl7, the otherwise multiphonon-quenched I-4(9/2) and H-2(9/2) levels are metastable and can serve as intermediate pump and upper laser levels, respectively, for a green upconversion laser excited at 800 nm. Polarized spectra of ground-state and excited-state absorption at 800 nm and of emission at 560 nm are measured, and the corresponding absorption and emission cross sections are derived. Luminescence-decay measurements provide lifetime data. Despite the large number of metastable levels of Er3+ in low-phonon host material, luminescence spectra and intensity-versus-power measurements reveal that the energy dissipation into levels other than those required for the operation of the laser transition (i.e., I-4(15/2) --> I-4(9/2) --> H-2(9/2) --> I-4(13/2)) is Small at low dopant concentrations. At higher concentrations, an energy-transfer upconversion process populates the lower laser level and counteracts inversion. The theoretical pump threshold of the proposed upconversion-laser transition under cw and pulsed excitation is derived. (C) 2000 Optical Society of America [S0740-3224(00)02111-1] OCIS codes: 300.6280, 300.6360, 160.5690, 160.4760. [References: 44]