Broadband Visible Light Emission From Nominally Undoped and $\hbox{Cr}^{3+}$ Doped Garnet Nanopowders

Synthetic garnet nanopowders of Y
₃
Al
₅
O
₁₂
(YAG) and Gd
₃
Ga
₅
O
₁₂
(GGG) were produced, and the occurrence of a broadband bright visible emission by nominally undoped YAG and GGG and Cr
³⁺
doped GGG, depending on the environment pressure, as well as exciting on the pumping power, was demonstrated. The results indicate that high-intensity infrared laser irradiation in samples not only leads to heating (melting effects) but also produces visible broadband emission. Low pressure of the powders' environment favors the white light emission by lowering the threshold pumping power. A hypothesis on the nature of the emission is presented.