We report room-temperature pulsed up-conversion laser oscillation in E
r-doped LiYF4 and KYF4 at 551 and 562 nm, respectively. In both crysta
ls laser oscillation is observed on the S-4(3/2)-I-4(15/2) ground stat
e transition. Excitation was provided by a tunable flashlamp-pumped Ti
:sapphire laser in the spectral region around 810 nm. Additional pumpi
ng with a continuous wave krypton ion laser at 647 nm was beneficial t
o both lasers. Laser action has also been observed in Er-doped Y3Al5O1
2 on the same transition.