Sintered, translucent ceramic microbeads, preferably alumina, titania, zirconia, {TAIL ~ yttria}, zirconium phosphate, or {HEAD ~ yttrium aluminum garnet} are doped with one or more optically active species 
Sintered , translucent ceramic microbeads , preferably alumina , titania , zirconia , { TAIL ~ yttria } , zirconium phosphate , or { HEAD ~ yttrium aluminum garnet } are doped with one or more optically active species
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