Fluorescence anti-Stokes de l'Er³⁺ et du Tm³⁺ par transfert d'energie

Abstract

Abstract Antistokes fluorescence in the green and blue region, excited by infrared radiation (λ=0.97μm) is observed with a relatively high efficiency in substances which contain not only a luminescent activator (Er 3+ or Tm 3+ ), but also a sensitizer which has a strong infrared absorption (Yb 3+ ). Polycrystalline mixed tungstates and germanate glasses have been studied. The green fluorescence of Er 3+ increases as a square-law function of the excitation intensity, the blue fluorescence of Tm 3+ as a cubic function. This effect has been used to build an optical amplifier which has served to measure the excitation spectra. The mechanism of excitation is the following: Absorption of the infrared radiation by the sensitizer, followed by energy transfers to the luminescent activator, which is excited stepwise up to the initial level of luminescence. Oscillator strengths for some transitions between excited levels have been calculated.