Excited-state absorption and up-conversion in Er3+single sites of CdF2:Er3+,Na+

Abstract

An efficient red-to-green up-conversion arising from Er³⁺ single sites of C_2v symmetry has been observed in CdF₂:0.1 mol% ErF₃, 0.1 mol% NaF at 77 K, under CW dye-laser excitation in a phonon sideband. It is shown that the mechanism responsible for this anti-Stokes fluorescence is a sequential two-photon absorption process via the lowest excited state of the Er³⁺ ion. This up-conversion phenomenon is used to study the excited-state absorptions of two major sites of Er³⁺ in CdF₂:0.1 mol% ErF₃. The excited-state absorption processes cannot be neglected in the interpretation of the excitation spectra of the laser-induced anti-Stokes fluorescences. In addition, the authors emphasise the importance of the two-step absorption in site-selective spectroscopy.