[Upconversion luminescence in Ho3+ doped fluoride thin film with excitation red laser]

Ho3+ doped fluoride thin film was deposited on common glass matrix by low energy pulse laser (532 nm, quadratic harmonics of Nd: YAG laser). Red and green upconversion luminescences with central wavelength of 770 and 540 nm have been observed through Japan R-500 spectrometer with excitation of 632.8 nm He-Ne laser. These upconverted emissions are ascribed to transitions of 5S2-->5I7, 5F4-->5I7 and 5S2-->5I8 and they are realized by two step absorption of Ho3+ ions and energy transfer among Ho3+ ions.