Two-photon absorption-induced ⁴F_9/2 → ⁶H_15/2 fluorescence of dysprosium ions

Fluorescence spectra of a solution containing Dy³⁺ ions have been measured at room temperature. The excitation spectrum features show a great peak at 350 nm when the detection wavelength is fixed at 483 nm. Meanwhile another weaker peak takes place at 630 nm, which is owing to two-photon absorption. Therefore, as the excitation wavelength is fixed at 320 nm and 630 nm, respectively, both single-photon and two-photon absorption induced fluorescence emission peaks are observed. Furthermore, the emission excited by 630 nm is more intense. When silver colloids are added to the solution containing Dy³⁺, the enhancements of two-photon absorption induced fluorescence are more intensive. We believe that these enhanced fluorescence are due to the local field enhancement around Dy³⁺ ions owing to the induced surface plasmon resonance of silver nanoparticles.