VISIBLE TO UV UP-CONVERSION IN ER3+ DOPED CADMIUM CHLORIDE AND ZINC-CHLORIDE GLASSES

Up-conversion luminescence in the UV has been observed in Er3+ doped cadmium chloride and zinc chloride glasses (Cd0.5Ba0.3K0.2Cl1.8 and Zn0.5K0.5Cl1.5) when the 4S3/2(E) excited state is pumped by pulsed laser between 545 and 555 nm. The principal up-conversion emissions arise from the 4G9/2(T), 4G11/2(L), and H-2(9/2)(K) excited states at 36 200, 26 000, and 24 300 cm-1 respectively. The main up-conversion process is the sequential two-photon absorption at a single Er3+ ion to populate the 4G9/2(T) state. At excitation intensities of roughly 10(18) photons/cm2 the UV emissions from the cadmium chloride glass are remarkably strong, approaching 5% of the intensity of the visible emission from the directly pumped state. The up-conversion luminescence from the zinc chloride glass is detectable but very weak. The emission from the 4G9/2(T) state decays nonexponentially over roughly 200 mus in the cadmium chloride glass. The 4G9/2(T) emission decays in less than 1 mus in the zinc chloride glass.