White emission of lithium ytterbium tetraphosphate nanocrystals.

An efficient anti-Stokes white broadband emission induced by 976 nm laser diode in lithium ytterbium tetraphosphate (LiYbP4O12) nanocrystals was investigated. The emission occurs at room temperature and atmospheric pressure. Its intensity demonstrates an evident threshold dependence on the temperature and excitation density characteristic to avalanche process. The white emission is accompanied by very efficient photoconductivity characterized by microampere photocurrent which increases with the fourth order of applied incident light power (~P4). We show that this emission is critically dependent on temperature and increases significantly in vacuum. It is concluded that the anti-Stokes white emission is associated with theYb3+- CT luminescence.