Visible to UV up-conversion in Er3+ doped cadmium chloride and zinc chloride glasses

Abstract

Up‐conversion luminescence in the UV has been observed in Er³⁺ doped cadmium chloride and zinc chloride glasses (Cd_0.5Ba_0.3K_0.2Cl_1.8 and Zn_0.5K_0.5Cl_1.5) when the ⁴S_3/2(E) excited state is pumped by pulsed laser between 545 and 555 nm. The principal up‐conversion emissions arise from the ⁴G_9/2(T), ⁴G_11/2(L), and ²H_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 ⁴G_9/2(T) state. At excitation intensities of roughly 10¹⁸ 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 ⁴G_9/2(T) state decays nonexponentially over roughly 200 μs in the cadmium chloride glass. The ⁴G_9/2(T) emission decays in less than 1 μs in the zinc chloride glass.