FOUR-LEVEL SOLID-STATE LASER IN THE 1.5-4 UM RANGE

MULTI-SPECTRAL LASER COUNTERMEASURE SYSTEMS REQUIRE SOURCES IN THE MID-INFRARED. SOLID-STATE LASER SOURCES UNDER DEVELOPMENT ARE QUASITHREE LEVEL LASERS, SUCH AS TM:HO:YAG (2.1 UM). OPERATION OF QUASITHREE LEVEL LASERS IS TEMPERATURE DEPENDENT AND SUCH DEVICES HAVE INCREASED THRESHOLDS AND REDUCED EFFICIENCIES AT ROOM TEMPERATURE. WE PROPOSE A FOUR-LEVEL SOLID-STATE LASER BASED ON A COMBINATION OF RARE-EARTH IONS IN A FLUORIDE HOST. PREVIOUSLY WE CONDUCTED AN INVESTIGATION OF THESE IONS DOPED INTO AN OXIDE GARNET HOST AND DEMONSTRATED THE FEASIBILITY OF THE SCHEME. THE FLUORIDE HOST SHOULD GREATLY IMPROVE THE LASER PERFORMANCE OF THE ION COMBINATION. WE WILL GROW THE CO-DOPED FLUORIDE CRYSTAL, EXAMINE ITS LASER POTENTIAL BY SPECTROSCOPY AND PERFORM A LASER PUMPED LASER EXPERIMENT. THE CO-DOPED SYSTEM WILL BE PUMPED BY VISIBLE SOURCES FOR INITIAL INVESTIGATIONS BUT CAN BE PUMPED BY GAALAS DIODES IN THE 750-850 NM RANGE FOR HIGHER EFFICIENCY. THE LASING ION HAS FOUR EMISSION BANDS, NOT TERMINATING IN THE GROUND STATE, FROM 1.5 TO 4 UM INCLUDING A TRANSITION IN THE 'EYE SAFE' (1.4-1.85 UM) REGIME. THIS LASER COULD BE A DIRECT SOURCE FOR APPLICATIONS IN THE MIR AS WELL AS BEING AN EFFICIENT PUMP SOURCE FOR OPTICAL PARAMETRIC OSCILLATORS.