Development of solid state vibrational lasers

Continuous-wave lasing in the 5 micrometers wavelength region has been obtained on the 2 to 1 vibrational transition of impurity CN- ions in KBr. Population inversion is produced by optical pumping of the weakly allowed first-overtone level of the molecule with a tunable (F2(+)) sub A color center laser. We have investigated the energy budget of this solid-state vibrational laser when the v = 2 upper laser level is pumped with a CW color center laser. Using pulsed fluorescence techniques and numerical simulations, we find that due to vibrational energy exchange between pairs of CN- ions in the v = 1 lower level, waste pump energy is recycled to the v = 2 upper level. Ideally the efficiency of this recycling scheme approaches unity, but due to energy transfer into higher vibrational levels, and because of spectral diffusion within the inhomogeneously broadened CN- profile, the observed recycling efficiency is reduced. To our knowledge this is the first experiment demonstrating defeat of the Manley-Rowe limit.