e/Energy transfer upconversion

Information
has gloss	eng: Energy Transfer Upconversion or ETU is a physical principle (most commonly encountered in solid-state laser physics) that involves the excitation of a laser-active ion to a level above that which would be achieved by simple absorption of a pump photon, the required additional energy being transferred from another laser-active ion undergoing nonradiative deexcitation.
lexicalization	eng: Energy transfer upconversion
instance of	c/Solid-state lasers