Development of host crystals for Ce(+3) blue and blue-green solid-state lasers

Blue-green lasers operating at equivalent 480 nm, a region of sea water transparency, could become an integral part of undersea and air to sea communication and imaging systems. During Phase 1 of this program, wide band gap oxides were examined which could support Ce+3 luminescence in this region. A basic requirement for observing Ce+3 d yields f luminescence in this region is a cubic site symmetry as is found in the Th+4 or Ce+4 position of THO2 and CeO2, or the La+3 position of LaAl03 and LaAl1-xScx03 (perovskites). These oxides were synthesized, doped with Ce+3, using either oxidation of mixed oxalates for THO2.Ce, or a combination of component oxides in a molten BaCO3/BaF2 flux for the perovskites. Total luminescence spectra of the oxides revealed a two component fluorescence between 400 and 500 nm in all cases, with two excitation maxima between 320 and 380 nm. Some contribution to the spectra from Ce+4 or from an impurity defect center could not be ruled out. A concerted effort on production of optical quality specimens of the promising materials, either as clear ceramics or single crystals, is recommended for Phase 2 of this investigation so that they may be evaluated as lasers.