Abstract: The present invention is a solid state laser, including: (1) a laser cavity defined by a first mirror and an opposing second mirror, where these mirrors are reflective at the output wavelength of the laser; (2) a laser medium disposed in the laser cavity, including a low phonon energy host material, doped with an amount of praseodymium ions sufficient to produce a longitudinal mode laser emission from the transition of the praseodymium ions from the .sup.3 F.sub.3 excited state to a lower energy state when the laser medium is pumped by an appropriate pump, where the energy gap between the .sup.3 F.sub.3 excited state and the lower energy state corresponds to the output wavelength of the laser; and (3) a pump for the laser medium.