Potential uses of chromium(III)-doped transparent glass ceramics in tunable lasers and luminescent solar concentrators

The successful operation of alexandrite as a room temperature tunable laser arises from the fact that chromium exists in these crystals at a low crystal field. A similar situation has been found in chromium(III)-doped glass ceramics prepared by Buch and Ish-Shalom. The ⁴T₂ → ⁴A₂ splitting becomes comparable with or smaller than the separation to the ²E → ⁴A₂ level, and as a result a broad band four-level laser system can be obtained. In addition, ⁴T₂ → ⁴A₂ luminescence in some of the glass ceramics doped with chromium is of extremely high quantum yield; this makes such materials suitable candidates for luminescence solar concentrators which concentrate solar light on small areas, thereby enabling the cost of photovoltalic electricity to be reduced. The theory of tunable lasers and luminescent solar concentrators is outlined.