A non-destructive determination of the rare-earth ion concentration in laser crystals

The efficiency of the laser crystals doped with trivalent rare-earth (RE) ions depends on the degree of the homogeneous distribution of the concentration of the RE ion in the crystal volume. In this communication, and as a first contribution to the subject, the concentration of the Pr³⁺, Er³⁺ and Tm³⁺ ions in BaF_2, SrF₂, CaF₂ and KY₃F₁₀ wide band-gap dielectric crystal hosts was determined by measuring the magnetic moment of the ions, using the vibrating sample magnetometer (VSM) method, for the first time to our knowledge. With this experimental method concentration of the RE ions could be determined within 0.1% accuracy in a non-destructive way. In addition, by applying laser induced fluorescence spectroscopy in the vacuum ultraviolet region of the spectrum (100–200 nm), the magnetic properties of the 4fⁿ⁻¹5d electronic configurations can be predicted from the optical spectra for electronic states lying 8 eV above the ground electronic state of the 4fⁿ electronic configuration.